WO2011061727A1

WO2011061727A1 - Focusing antenna system and method

Info

Publication number: WO2011061727A1
Application number: PCT/IL2009/001101
Authority: WO
Inventors: Michael Bank; Boris Levin; Motti Haridim; Susan E. Lifshitz
Original assignee: Michael Bank; Boris Levin; Motti Haridim
Priority date: 2009-11-23
Filing date: 2009-11-23
Publication date: 2011-05-26

Abstract

The present invention provides focusing antenna systems and methods for controlling both near and far radiation patterns, the system comprising a focusing antenna system and a control module, constructed and configured to control the radiation patterns of said system so as to form both a predetermined level of radiation at a first short distance from a telecommunication device and concomitantly to provide at least a second level of radiation at least one longer distance from the communication device.

Description

FOCUSING ANTENNA SYSTEM AND METHOD

FIELD OF THE INVENTION

The field of the invention is related generally to antennae and antenna systems, and more specifically to antenna systems for controlling radiation patterns.

BACKGROUND OF THE INVENTION

An antenna, or antennae, system can be classified in various ways. One particular classification refers to the directivity of the antenna. An antenna can be omni- directional in multiple directions, or omni- directional in one plane, for example, a monopole. While omni-directional antennas are required in certain applications, there are many other applications in which efforts are directed as to produce a rather narrow beam (pencil like) of radiation. In these cases it is desirable to concentrate the radiation energy in a single main lobe and to avoid creation of side lobes.

For the latter case, well known antenna array (AA) systems consisting a multitude of emitters (radiators), have been developed which allow for creating a directional radiation pattern, see Fig. 1. An AA is a multiple of active antennas fed by a common source, or a load in the case of a receiving antenna array, which is designed as to produce a directive radiation pattern at far field region. The spatial relationship, besides the current feeding scheme in terms of the amplitude and the phase of the current in each element, between the radiators also contributes to the directivity of the antenna.

There are different kinds of AAs, and the main goal of all conventional (state of the art) AAs is to concentrate the far field radiation energy in a certain direction. The main idea behind the conventional AAs is to feed each radiator with a signal of appropriate phase so that the fields of all emitters add constructively in one (desired) direction at any distance, in the far field region.

Besides the fixed pattern AAs, there are also reconfigurable AAs, which allow for changing the direction of the main beam, i.e. the directional radiation pattern, without moving the antennas. This is achieved by dynamic phase shifters used in each radiator circuit, see Fig. 2.

All known AAs including the reconfigurable AAs are comprised of N (>2) radiators. The radiation pattern in these AAs does not depend on distance from the antenna, as far as the distance from the array corresponds to the far field region of the antenna system. Design efforts are devoted to obtain a certain pattern at far field regions and no attempt is made as to shape the near field pattern.

Wireless communication transmitters or transceivers emit radiation in an area around the device, besides the intended radiation towards the relatively long distances. Proximity of a transmitting antenna to sensitive/vulnerable devices, circuits or systems, may induce damage both in terms of proper operation of such device, circuit or system, and in terms of physical damage. A particular example is, mobile telephones and other telecommunication devices, which are often placed close to the user's head/body for the duration of the telephone conversation. It is known that this radiation may lead to health problems, especially in the long term. Additionally, the radiator's proximity to user's head distorts an antenna pattern and results in power losses and hence degradation of communication performance. It is thus necessary to reduce the irradiation of human tissues. At the same time, a pattern and a field magnitude in a far region should not change in order to preserve the quality of communication with the correspondents (directly or through base stations) in any direction.

Some methods of reducing the irradiation interaction level from a transmitter on the human body, or a vulnerable device located in the near field region are known in the art. For example, in the case of cellular handsets, an antenna is disposed distantly from the most sensitive parts of human tissues. This method is applied, inter alia, in US Patent Nos. 5,950,1 16 and 5,513,318, as well as in International Patent Publication No. WO99/044346. The antennas, which are produced according to this method, are bulky, not aesthetic and are also not very practical for use.

Some methods are based on field screening and others on radiation absorption using special materials to be mounted on the vulnerable device/receiving antenna or human side. Antenna screening is described, inter alia, in US Patent Nos. 5,784,032, 5,826,201 and 5,657,386. US Patent No. 5,666,125 describes a method of radiation absorption from a cell phone. However, for protection of the user it is necessary to employ a screen, which is substantially larger in size than a lateral dimension of the phone housing. Additionally, this method is limited as it causes field magnitude decrease and pattern distortion in a far region.

International Patent Publication No. WO08/076688 discloses a directive antenna with null zone in a given direction. This method is further elaborated in a publication entitled "SAR reduction for handset with two-element phased array antenna computed using hybrid MoM/FDTD technique."(auihors Mangoud M. A., Abd-Alhameed R. A., McEwan N. J. et al., journal "Electronics Letters", vol. 35, no. 20, 1999, p.1693). The antenna described is a two-element phased array antenna, which comprises a metallic box with two monopoles mounted thereupon. The monopoles are placed along a straight line, and perpendicular to the straight line, passing through the center of the aforementioned metallic box and the center of a user's head. The phased array antenna is designed to direct power away from the user's head and to greatly reduce the radio frequency exposure of the user. However, this method destroys the antenna pattern at far field and creates gaps and null zones, thereby reducing the communication quality.

There is therefore a need for a method and system for providing different radiation patterns at different distances.

SUMMARY OF THE INVENTION

It is an object of some aspects of the present invention to provide systems, devices and methods, which are configured to provide two different radiation patterns, a) one at small distances (near field) and b) a second one at long distances (far field). The near field pattern is designed and configured to deal with problems involving damage and/or disturbance to nearby devices/ antennas /users, and the far field pattern will address the communications needs of the system.

It is another object of some aspects of the present invention to provide systems, devices and methods which are configured to reduce the quantity of incident radiation on a vulnerable device/user, without reducing or ruining the quality of communication.

Some aspects of the present invention provide methods and systems for significantly reducing, or anti- focusing, or focusing electromagnetic radiation into a certain area located at certain distance from an antenna. In other words, the present invention provides a Focusing Spot (FS) at a certain distance from the antenna. FS can be either a tiny (point) spot, or an extended spot of certain shape, e.g. a ring or part of a ring. Another example of such applications is the desire for increasing field intensity inside a particular apartment or other indoor location while decreasing the field intensity behind that apartment, or other outdoor location, for data-security purposes. Yet another example could be in such applications where a multiple of communication systems, including several Tx (transmitting) and Rx (receiving) antennas, co-exist in a relatively small area. In this case the fields stemming from a Tx antenna can interfere with the field falling on a nearby receiving antenna, causing a distortion of the received signals. The ability for producing a Focusing Spot (FS) is also desired in cases that the field strength around a powerful transmitter, which must be reduced without decreasing the radiation level at far regions.

Further non-limiting examples include:

i) Situations in which a powerful transmitter irradiates on nearby residential buildings. It is required to create a weak field area near and around the transmitting antenna, and

ii) situations where a high data-security area is required.

It is a further object of some aspects of the present invention to provide systems, devices and methods for providing antenna systems to be used in different wireless communication and radar systems, , and also to be applied to the field of EMC (Electromagnetic compatibility). In communication systems generally the main concern is to ensure that the received energy is sufficiently high, above the receiver's sensitivity, so that the receiver can function properly at an adequate performance level. In certain applications, it is very important to ensure that the EM (electromagnetic) irradiance in certain areas within the near field region is low. Examples include, but are not restricted to, antennae in the vicinity of human bodies, such as wireless phone handsets and devices, receiving antennae mounted in the vicinity of high power transmitting antennas, sensitive components located nearby transmitting antennas, EMC oriented problems and requirements for high data security regions.

The method, systems and antenna modules of the present invention introduce a new class of antenna systems for which the near field pattern is designed (shaped) desirably as to maintain the radiation level requirements in given areas, yet without affecting the above-mentioned far field performances.

The method, systems and antenna assemblies or systems modules of the present invention are constructed and configured to either significantly reduce or increase the electromagnetic (EM) radiation inside a certain area at a certain distance from the antenna system (or main antenna). In other words, the systems provided create a strong or weak radiation spot (hereafter called a Focusing Spot - FS) at a certain distance from the antenna. FS can be either a tiny (point) spot, or an extended spot of certain shape, e.g. a ring or part of a ring.

FS can be either a positive focus (high radiation level) or an anti-focus, namely lack of radiation.

It is another object of some aspects of the present invention to provide systems, devices and methods which are configured to provide the ability for producing, by independent design, two different radiation patterns at different distances, e.g. for the purpose of reducing the quantity of incident radiation on a device or user, without reducing or ruining the quality of communication.

A further object is to provide the ability to combat successfully effects of changing environmental conditions which may adversely affect the performance of the said system/module/method. For this purpose, this invention introduces a novel circuitry for field intensity stabilization so that under environmental changes, the FS remains stable in terms of its position, size, and the radiation level. In short, this invention is twofold: it introduces a Focusing Antenna (FA) system, and a novel stabilization scheme.

As stated above, one objective of the present invention is to provide a system/module/device which allows for a desirable design of 2 different radiation patterns: at the far field region, and at closer distances. The near field pattern is usually concerned with the quantity of radiation, namely either a drastic decrease or a drastic increase of the field density in an area located at a desired distance from the transmitter up to the receiver area.

It is a further object of some aspects of the present invention to provide systems, devices and methods which are configured to retain a quality of communication under all conditions including when the user is moving or roaming. This may be performed using a number of combinations of methods, including using antennae of different lengths and types, disposing the antennae in different directions, employing an antenna of special type (e.g. a PIFA or a monopole), providing a self- adjusting system, providing an automatic compensation system, providing an automatic compensation system with a time delay, reducing the quantity of incident radiation on a device, or user, or combinations thereof, without reducing or ruining the quality of communication.

According to some embodiments of the present invention, a transmitting antenna system is provided comprising of a main antenna and an auxiliary antenna, such as two monopoles. The monopoles are disposed in a near region of each other, near a vulnerable object. The monopoles are disposed such that their radiation fields superimpose on each other in such way that reduce the total radiation impinging on the vulnerable object.

There is thus provided according to an embodiment of the present invention, an antenna system for controlling both near and far radiation patterns, the system including;

a focusing antenna system, including a control module, constructed and configured to control the radiation patterns of the system,

wherein the system is adapted to provide a maximal predetermined level of radiation at a first short distance from a main antenna and concomitantly to provide at least a second level of radiation at at least one longer distance from the main antenna.

According to some embodiments of the present invention, the focusing antenna system includes;

i. at least one main antenna;

ii. at least one auxiliary antenna; and iii. a tuning block.

Additionally, according to some embodiments of the present invention, the at least one auxiliary antenna includes at least two auxiliary antennae.

Furthermore, according to some embodiments of the present invention, the main antenna is constructed and configured to define a far radiation pattern at the at least one longer distance.

Yet further, according to some embodiments of the present invention, the at least one auxiliary antenna is constructed and configured to define a near field radiation pattern at the first short distance.

Moreover, according to some embodiments of the present invention, the near radiation pattern is at a distance less than a communication range of a device in the system.

Additionally, according to some embodiments of the present invention, the at least one main antenna is installed within a communication device.

According to some further embodiments of the present invention, the near field radiation pattern is selected from the group of various shapes including; a spot in a near field of the device; a ring in a near field of the device; an annulus in the near field of the device; a shell in the near field of the device; and various threshold values of radiation level.

According to some additional embodiments of the present invention, the device further includes a tuning block (TB) disposed in a feeding line of each of the at least one auxiliary antenna.

Furthermore, according to some embodiments of the present invention, the near radiation pattern is selected from the group consisting of; a high radiation focused spot and an anti-focused spot of diminished radiation.

According to some additional embodiments of the present invention, at least one main antenna is constructed and configured to provide communication of the device at far field regions and the at least one auxiliary antenna is disposed proximal to the at least one main antenna in the device.

Additionally, according to some embodiments of the present invention, the at least one auxiliary antenna is constructed and configured to provide a desired radiation pattern in a near field of the device, without affecting the far field performance of the main antenna.

There is thus provided according to an additional embodiment of the present invention, a transmitting antenna system for use in a telecommunication device for creating a reduced radiation in a near field, the device including;

a. a telecommunication apparatus including a main antenna; and

b. a radiation reducing unit including at least one auxiliary antenna connected to the signal source via a tuning block. According to some additional embodiments of the present invention, the tuning block includes a magnitude controller and a phase shifter. Additionally, according to some additional embodiments of the present invention, the main antenna and the at least one auxiliary antenna are of the same type but of different sizes.

Moreover, according to some additional embodiments of the present invention, the main antenna and the at least one auxiliary antenna are of different types and of different sizes.

There is thus provided according to a further embodiment of the present invention, a mobile telecommunication device with reduced radiation in a near field, the device including;

a) a telecommunication apparatus including a main antenna connected to a signal source; and

b) a radiation reducing unit including an auxiliary antenna connected to the signal source via a tuning block including one of:

i. a magnitude controller and a phase shifter; and ii. a self-adjusting system including a phase shifter, a phase detector, and a self-tuning unit adapted to provide outputs of the phase tuner and the magnitude controller with certain values of phase difference and amplitudes ratio.

According to some further embodiments of the present invention, the main antenna and the auxiliary antennae are of different sizes, thereby being adapted to create a weak field disposed at any desired location.

According to some further embodiments of the present invention the near field radiation pattern is a weak or zero field and the device is configured to use at least one reflection signal from a nearby reflecting surface for creation of a focusing spot (FS).

According to some additional embodiments of the present invention the self- tuning unit includes a multiplier, at least one low pass filter, operational amplifiers and a phase detector.

Additionally, according to some further embodiments of the present invention, the mobile telecommunication device further includes a first connection of the low pass filter with a control input of the phase shifter and a second connection of the operational amplifier output with a control input of the magnitude controller.

According to some further embodiments of the present invention, the magnitude controller is an adjustable potentiometer.

Additionally, according to some further embodiments of the present invention, a phase compensation time delay, disposed between the low pass filter and the phase tuner.

Additionally, according to some further embodiments of the present invention, the telecommunication device is a telephone. In some cases, the telephone is a mobile cellular phone.

Additionally, according to some further embodiments of the present invention, the device is selected from a cordless telephone, an ad-hoc wireless communication network device using a handset; a personal assistant and a portable computer.

In some cases, the auxiliary antenna is adapted to be disposed closer to a head of a user of the device than the main antenna.

There is thus provided according to a further embodiment of the present invention, a method of radio transmission from a communication device for creating;

a zero (minimal) field at a compensation point P;

a weak field at a Focusing Spot (FS) around the compensation point; and a minor change of field far from the FS.

Additionally, according to some further embodiments of the present invention, the fields of two radiators mutually compensate each other at a given point of the device, and the field magnitudes, created by these radiators, equal in this point, whereas the field phases in this point differ one from another by a value 180°.

Moreover, according to some further embodiments of the present invention, a few radiators produce zero field at the compensation point P and a weak field in a FS surrounding the point P, and the weak field in the FS is substantially lower than the field, which every one of the radiators would produce in the absence of all other fields.

Additionally, according to some further embodiments of the present invention, the radiators are placed in a housing of a mobile phone, in order to decrease an irradiation of user's body and to decrease the total and the local Specific Absorption Rate (SAR) inside a user's body, in particular inside of user's head and hand.

Furthermore, according to some further embodiments of the present invention, two fields radiated by two radiators, located at different distances from the point P and tuned to ensure the fields having the same magnitudes and opposite in phase in the point P.

Additionally, according to some further embodiments of the present invention, the distance between the two radiators is λ/4 or less.

Additionally, according to some further embodiments of the present invention, the distance between the antennae is small for field compensation, thereby enabling construction of a thin device.

Moreover, according to some further embodiments of the present invention, at least one of the two fields created is a result of a superposition of separate fields, and wherein each field is produced by a separate radiator.

Additionally, according to some further embodiments of the present invention, the radiator positioned closer to the compensation point P, is performed by two radiators, placed along a straight line, perpendicular to the straight line connecting the auxiliary radiator and point P, and thereby produce a field of the half magnitude.

Additionally, according to some further embodiments of the present invention, the two radiators are connected to a single source, at that at least one of the radiators is connected to the single source via a magnitude controller and at least one of the radiators is connected to the single source via a phase shifter.

Additionally, according to some further embodiments of the present invention, the size of one auxiliary radiator is selected in order to provide the required phase shift and the magnitude change, so as to render unnecessary the radiator connection to the signal source either via a phase shifter or via a magnitude controller.

There is thus provided according to a further embodiment of the present invention, a transmitter having a main antenna, and auxiliary antennae, all antennae being connected to the same signal source, wherein the antennae are designed and positioned in respect of each other in a manner enabling them to transmit signals, the superposition of which has zero intensity at a predetermined point P positioned in a transmission zone and non-zero intensity at the rest of the transmission zone. The size of at least one of the antennas may be designed to provide for the required phase shift and amplitude control, so as to render unnecessary the connection of the antenna to the signal source via a phase shifter and an magnitude controller.

Additionally, according to some further embodiments of the present invention the two antennas are positioned in different distances from the point P.

There is thus provided according to a further embodiment of the present invention, A phase locking method for radio transmission from a communication device for automatic stabilization of antenna pattern behavior upon appearing up of metallic objects or proximity to different media making the surrounding of the FA a heterogenic medium which influences the antennas parameters.

Additionally, according to some further embodiments of the present invention, the method includes having an extended tuning block (TB) for automatic stabilization of the antennae, the antennae being subject to external influences.

There is thus provided according to a further embodiment of the present invention, a transmitting antenna module for increasing amount of radiation indoors and decreasing outdoor radiation for data security.

Additionally, according to some further embodiments of the present invention, the methods herein may be applied for application of focusing array (FA) in electromagnetic compatibility (EMC) problems in reducing radiation levels in vulnerable devi ces .

Additionally, according to some further embodiments of the present invention, the method further includes employing at least one focusing antenna in a dense area of antennas, the dense area including a plurality of receiving antennae and a plurality of transmitting antennae, for removal of any undesired radiation at a receiving antenna due to a nearby high power transmitter.

Additionally, according to some further embodiments of the present invention, the method further includes integration of at least one transmitter and at least one receiver on a single chip.

There is thus provided according to a further embodiment of the present invention, a three dimensional assembly of auxiliary antennae in the system as described herein. A focusing antenna system (FA) including a main antenna which is a conventional antenna array (AA) and at least one auxiliary antenna which is located opposite at least one of a plurality of antenna array elements, thereby producing a focusing spot (FS) in the vicinity of the at least one element of the antenna array.

There is thus provided according to a further embodiment of the present invention, a method of design of a focusing antenna system including;

a. monitoring changes in at least one parameter of each antenna in the focusing antenna system; and

b. designing the system according to results of the monitoring step, wherein at least one change is responsive to the presence of the human body.

There is thus provided according to a further embodiment of the present invention, a method for improving electromagnetic compatibility (EMC) including;

a. monitoring radiation levels to characterize the exiting fields in at least one location; and

b. providing auxiliary antennae so as to reduce a radiation level by compensation at the at least one location, wherein the at least one location is selected from the group consisting of; a location on a piece of equipment; a location proximal to a piece of equipment; and a location of a known high level of radiation, thereby reducing the radiation level at the location.

The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be a useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings:

Fig. 1 is a simplified pictorial illustration of a prior art antenna array (AA) consisting of three antenna elements;

Fig. 2 is a simplified pictorial illustration of a prior art reconfigurable antenna array (AA) with the possibility of phase adjustment to allow for dynamic change of a far field radiation pattern;

Fig. 3 A is a simplified pictorial illustration of a focusing antenna array (FA) in the general case, in accordance with an embodiment of the present invention;

Fig. 3B is a graphical representation of the distance dependence of a radiated electric field of a regular antenna and of a focusing antenna system, in accordance with an embodiment of the present invention;

Fig. 4 is a simplified pictorial illustration of a tuning block (TB) consisting of

RF circuitry for phase shifting and amplitude controlling, in accordance with an embodiment of the present invention;

Fig. 5 is a simplified pictorial illustration of focusing antenna array, used for decreasing radiation near a powerful transmitter, in accordance with an embodiment of the present invention;

Fig. 6 is a simplified pictorial illustration of the field strength distribution created by the focusing antenna system of Fig. 5;

Fig. 7 is a simplified pictorial illustration of an application of a focusing antenna array to data security, in accordance with an embodiment of the present invention;

Fig. 8 is a simplified pictorial illustration of a primary focusing antenna system with one auxiliary antenna, illustrating a focusing spot (FS) location, in accordance with an embodiment of the present invention;

Fig. 9 is a simplified pictorial illustration of the presence of a disturbing object near focusing antenna (FA) system in a dynamic environment;

Fig. 10 is a simplified pictorial illustration a prior art phase locked loop (PLL) used for equalization of the phases of two signals (zero phase difference);

Fig. 1 1 is a simplified pictorial illustration a prior art scheme for equalization of the voltage levels of two signals (amplitudes ratio of unity);

Fig. 12 is a simplified pictorial illustration of a control module comprising circuitry for maintaining a constant phase difference of any value and a constant amplitude ratio of any value between two signals, in accordance with an embodiment of the present invention; and

Fig. 13 is a simplified pictorial illustration of a radiation reducing unit comprising a time delay unit in the self-adjusting automatic compensation system in a mobile telecommunication device, according to an embodiment of the present invention.

In all the figures similar reference numerals identify similar parts.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that these are specific embodiments and that the present invention may be practiced also in different ways that embody the characterizing features of the invention as described and claimed herein.

Reference is now made to Fig. 1, which is a simplified pictorial illustration of a prior art antenna array (AA) 100 consisting of N elements (three in this case). N is normally greater or equal to two. An AA typically includes multiple antenna elements coupled to transmit or receive directive signals.

101, 102 and 103 are identical antennas of any type, e.g. monopoles, dipoles, patch antennas, PIFAs. All antennae are fed by the same signal. The distance between the array elements is designed solely for the purpose of a good communication link at far regions, with no attention whatsoever to affect the near field pattern.

Usually AAs are used to produce a narrow beam so that energy is efficiently transferred to long distances, well into the far field region of the antennas

Reference is now made to Fig. 2 which is a simplified pictorial illustration of a prior art reconfigurable array antenna (AA) 200 with the possibility of phase adjustment to allow for dynamic change of the far field radiation pattern. 201, 202, 203 are identical antennas of any type, 204, 205, 206 are phase shifters, and an input signal 207. Here, the phase of each element may be dynamically (electrically) changed in order to change the far field pattern, e.g. to move (to change the direction, or to scan) the narrow beam produced by the AA. This replaces the otherwise mechanical means for beam scanning.

Reference is now made to Fig. 3A which describes a simplified pictorial block diagram of a focusing antenna system (FA) 300A, in accordance with an embodiment of the present invention. The focusing antenna system (FA) is constructed and configured to change the near field radiation pattern of a main antenna 301 to obtain a desired shape (radiation level inside a certain volume). FA comprises main antenna

301 , N (N>1) auxiliary antennas 302, 303 and N tuning blocks (TBs) 304, 305. In this embodiment, N=2 auxiliary antennae are used (N>1).

The main antenna 301 is designed according to the very requirements of the communication link performance, i.e. the far field pattern. The auxiliary antennas 302, 303 are similar, usually even identical, in terms of their radiation characteristics, to the main antenna. The size of the auxiliary antennas, their feeds (relative to the main antenna) and their spatial relationship relative to each other as well as to the main antenna are designed such that the near field pattern is shaped according to a desired pattern, yet without affecting the far field performance of the main antenna. FA is different than the prior art AA (both contain a multitude of antennae) in the sense that:-

1) the design efforts are directed to make the fields of various elements interfere, either constructively or destructively, at a certain area in the near region of the main antenna, whereas in the case of prior art AAs, efforts are solely directed to far field radiation pattern

2) there is a well-pronounced difference, in terms of the input signal between the main antenna and the auxiliary ones.

3) The radiators separation is a small fraction of the wavelength, whereas in the prior art AAs the distance is usually λ/4 or more. Reference is now made to Fig. 3B, which is a graphical representation 300B of the distance dependence of a radiated electric field of a regular antenna and of a focusing antenna system. The distance dependence of the radiated electric field for two cases: i) regular antenna (curve 310), in which the field strength decreases monotonically, and ii) FA (curve 311) in which the field strength is at first reduced and has a minimum value 312 at a short distance from the main antenna, after which it increases to another turning point 313 and then declines with behavior, similar to that of the main antenna alone 310.

Fig.3B shows the behavior of the total electric field as a function of distance from the main antenna with and without the auxiliary antenna/e. The curve pertaining to the main antenna alone 310 indicates a monotonic decrease of the field with the distance, as is well known for any single antenna and for conventional AA. The curve for the FA 31 1 shows a well pronounced notch at a near distance to the antenna system. The notch defines the FS, and its depth and position can be determined for any desired values.

Generally, FA consists of two or more antennae: a main radiator (usually a single antenna but could be an array as well) and N (N > 1) auxiliary antennae (Fig. 3A). The auxiliary antennae are fed by the same generator of the main transmit antenna but their phase and amplitude are set by means of Tuning Blocks (TBs), consisting of a phase shifter 402 and a magnitude controller 401 (Fig. 4).

To achieve the required control of the radiation intensity at certain area, (either decreasing or increasing the field intensity), the TB parameters (i.e. the amount of phase shifting and the amplitude of the signal at the input of each auxiliary radiator) are set for minimum or maximum field strength in FS.

The present invention further provides a method of radio transmission, aimed to create a weak field (or strong field), and more preferably, a zero field (or a very strong field), at a compensation point (a focusing point). One example is a compensation point case. The compensation point is to be disposed near to or within a vulnerable object. Around the compensation point, a FS of a relatively weak field is produced, accompanied merely by a lighter change of the field outside the FS compared with the field of a main radiator alone, particularly and much lighter in the far region.

The radio transmitter creates a total electromagnetic field, produced by at least two radiators, both excited by a common generator.

Typically the method of the invention produces a zero field in a given point P and a weak field in an area surrounding the point P (in a FS). The weak field in the FA must be substantially lower than the field, which one of the radiators (i.e.the main one) produced in the absence of all other fields.

In particular, the method according to the invention, creates a total electromagnetic field as a sum (superposition) of two fields being of the same magnitude but of opposite signs/directions at the point P thereby canceling each other out. Equal fields magnitudes in the point P may be achieved by two radiators, located at different distances from the point P and tuned (in terms of input signals)to ensure equal field strengths at point P. An auxiliary radiator, positioned closer to the point P, usually lies in a straight line connecting the first radiator and point P.

The auxiliary radiator produces a field, having a lower magnitude and opposite phase to the first radiator, positioned more far from the point P. This produces an omnidirectional antenna pattern ( no angular sector with zero radiation).

The total fields of two radiators inside the FA, around the point P, may have either different magnitudes or will not be opposite in phase. Thus, the resultant field of the two radiators inside FS near P may be weak, but is a non-zero field. Outside the FS, the total field of the two radiators produce is equal to, or close to, the field which would have been produced by the main radiator in the absence of the auxiliary antennae whatsoever. If the two radiators (presumably of the same type) are placed at less than a quarter of a wavelength away, one from the other, the resulting pattern will have the same angular distribution in a vertical plane, as that of each of them alone. Such distribution permits one to obtain compensation of total field components thereby decreasing the total field at the compensation point. Additionally, small distances between radiators may be required in practice due to design limitations. Calculations and experience have shown that at frequencies of about 1 GHz, when free space wavelengths are about 30 cm, a distance between radiators of about 1 cm allows one to obtain the required compensation and a required factor of irradiation significant decrease.

It is clear that each of the two fields created in accordance with the invention may be the result of superposition of a few fields, each of which is produced by a separate radiator. In another embodiment, the radiator, positioned closer to the compensation point P, may be replaced by two radiators placed along a straight line, connecting the other (main) radiator and the point P, and each radiator producing field, the magnitude of which equals, at the compensation point, to half of the main radiator field magnitude. Also such radiator may be performed as two radiators, placed along a straight line, perpendicular to the straight line connecting the main radiator and the point P, and producing a field with the half magnitude.

The method of the invention may be used in order to reduce the irradiation of a predetermined volume inside the user's head (or other parts) by a cellular/mobile phone. Also the method of the invention may be used in order to reduce the irradiation of the whole head.

One embodiment of an antenna structure according to the invention has two radiators connected to a signal source, wherein at least one of the radiators is connected to the signal source through a magnitude controller and at least one of the radiators is connected to the signal source through a phase shifter.

In the case of dynamic environmental changes, the performances of the systems described above can be degraded (change of the position of the FS and level of field reduction). A spot of weak field intensity (Fig. 8) is created due to mutual compensation of the fields of the two antennas. This compensation condition can be disturbed in the presence of nearby metallic (conducting) parts/ objects/ materials, as shown in Fig 9. The influence of the conductive parts can be characterized in terms of changes in the antennas parameters, e.g. self and mutual impedances. To maintain the required compensation conditions, one must keep the antennae's phase and amplitude relationships unchanged also upon the introduction of metallic objects in the vicinity of the antennas. Phase-Locked Loop (PLL) based systems are usually used for maintaining a zero phase difference between two signals. For example, the PLL in Fig. 10 is used to maintain a zero phase difference between blocks A and B.

It is well known that one can utilize Operation Amplifier (OA)-based systems/circuits for keeping two voltage levels equal (Fig 1 1). These known schemes of Fig. 10 and 11 are best fitted where equal amplitudes and equal phases are needed.

In contrast, in the system of the present invention, a non-zero phase difference, yet constant difference and non-equal amplitudes, of a constant ratio, are required.

Reference is now made to Fig. 4 which presents a simplified pictorial illustration of a tuning block (TB) used at the input of each auxiliary antenna. It consists of a phase tuner 402 and an magnitude controller 401. The TB is fed by the signal source of the main antenna, via a power splitter and produces an appropriate feed (in terms of phase and amplitude) for the auxiliary antenna.

The magnitude controller may be an attenuator in which the attenuation level is controlled electrically. The phase tuner 402 sets a phase difference between its input and output signals.

Reference is now made to Fig.5, which is a simplified pictorial illustration of one possible application according to an embodiment of the present invention. Here the FA is used to reduce the radiation level nearby a transmitting antenna. In this case the main antenna 501 (producing a strong field in its near field area) is accompanied with N=6 auxiliary antennae 502, 503, 504, 505, 506, 507 through N=6 TBs 508,509, 510, 51 1, 512, 513. The very mutual position of the main antenna and the auxiliary ones determines the size and the position of the FS. In this embodiment, the auxiliary antennae are arranged in a 2-dimensional arrangement.

Reference is now made to Fig. 6 which is a simplified pictorial illustration of a

FS (weak-field area) produced by FA, according to an embodiment of the present invention.

601 is a main antenna; 602, 603, 604, 605, 606, 607 are auxiliary antennae, 608 is FS (focusing spot, weak field area) and 610 is the far field area due to the main antenna only.

This figure indicates that the invented method doesn't cause pattern distortions such as producing gaps and null zones in the pattern. That is, the communication quality doesn't degrade.

Reference is now made to Fig. 7, which is a simplified pictorial illustration of a radiation increasing scenario, according to an embodiment of the present invention. The FA is used in order to increase the signal power at certain place e.g. an indoor room such as a meeting room, and at the same time to reduce the signal power at another place such as outdoor vicinity surrounding the building, allowing to prevent data leakage hence improving data security. In this case FA 704 is used to increase the radiation level inside a room (focusing) and at the same time to decrease the radiation level outside that room (anti-focusing).

701 is the high field area (e.g. a meeting room); 702 is the area where field should be strengthen for high quality communications; 703 is the area in which the field is to be reduced in-order to prevent un-authorized person to "listen" to the communication; 704 is proposed FA.

Reference is now made to Fig. 8, which is a simplified pictorial illustration of an FA (for radiation reducing) utilizing one (N=l) auxiliary antenna and the weak- field region thus obtained. 801 is the main antenna; 802 is an additional antenna; 803 is an magnitude controller (controlled attenuator) (a part of TB), 804 is a controlled phase shifter (a part of TB); 805 is the FS produced by the FA.

Reference is now made to Fig. 9, which is a simplified pictorial illustration of a changing environment that can disturb the proper functioning of FA if appropriate measures are not taken. As well known the parameters, properties and performance of any antenna may change subject to the surrounding bodies, medium, materials, e.g. vehicles, users of mobile phones especially when carrying metallic parts. This invention provides a solution for proper operation of FA also when such disturbing bodies pup up in the vicinity of FA. 901 is the main antenna; 902 is additional antenna; 903 is controlled attenuator, 904 is controlled phase shifter; 905 is FS; 906 is a metallic object.

Reference is now made to Fig. 10, which is a simplified pictorial illustration of a prior art phase locked loop (PLL)- a controversial module used in many applications. 1001 is sinusoidal signal source which is the input of PLL, blocks A

1002 and B 1003 represent the loads due to antennae 1004 is phase tuner (controllable phase shifter). The aim of block 1004 is equalizing the phases on blocks 1002 and 1003 inputs in initial state; 1005 is phase detector (PD); 1006 is low pass filter (LPF). The phase detector (PD) (block X) 1005 has two inputs and one output. The PD's output is an electrical signal that ideally is proportional to the instantaneous phase difference between the two input signals. In most implementations, a voltage controlled oscillator (VCO) is used as the second input to the PD besides the source signal. In the PLL shown in Fig. 10, the second input to the PD is obtained from block

1003 input. In case of blocks 1002 and 1003 parameters changing, the negative feedback embedded in the loop tends to equalize the phase difference between the PD's inputs so that the feedback signal (output of PD) is kept close to zero. The LPF 1006 is used to remove any high frequency components in the output of PD, so that only the slowly changing components of the phase difference (which may change with time) is fed-back to the phase detector PD 1005, as a controlling signal. Blocks A and B 1002-1003 which represent the loads due to antennae are dynamically changing loads due to the environmental changes. FA requires that the signals fed into A 1002 and B 1003 to have the same frequency and matched phases. The PLL is used to keep the phase difference between signals fed to A 1002 and B 1003 constant regardless of the environmental changes tending to modify the loads they present to the power supply. However the use of the conventional PLL is limited only to the case that the desired phase difference is 0. FA requires various values of phase difference and hence the PLL cannot be used.

Reference is now made to Fig.1 1 , which is a simplified pictorial illustration of a prior art scheme for equalization of the voltage level of two signals. 1101 is a sinusoidal signal source, 1 102, 1 103 are radio circuits representing the load; 1 104 is an magnitude controller (controlled attenuator). The aim of block 1 104 is equalizing the amplitudes on blocks 1102 and 1 103 inputs in initial state; 1 105 is differential amplifier (usually an operational amplifier- OA); 1 106 is low pass filter (LPF). This figure is basically an analogue to Fig. 10 except that here the attempt is to equalize the signals amplitudes (instead of phases) by means of a negative feedback through an operational amplifier 1 105. FA requires an amplitude adjustment capability in order to provide an amplitude ratio of any desired value. However, this prior art circuit is capable of providing a sole value of ratio=l, and hence is not usable in FA.

As stated above, in the present invention we introduce a novel self-adjusting scheme, which allows for maintaining a constant phase difference of desired value and a constant amplitude ratio of desired value. This scheme is illustrated in Fig 12, in which blocks (p_ad_, Ri and R₂₎ are added to allow for getting phase equality at the inputs of the multiplier and amplitude equality at the OA inputs.

Reference is now made to Fig. 12, which presents a simplified pictorial illustration of a circuitry of the present invention for maintaining a constant phase difference of any value and a constant amplitude ratio of any value between two signals. 1201 is the signal source; 1202 is main antenna; 1203 is an auxiliary antenna; 1204 is an magnitude controller (controlled attenuator), The aim of block 1204 is to maintain the needed amplitude ratio in blocks 1202 and 1203. 1205 is one of controlled phase shifters; 1206 is additional phase shifter. The aim of block 1206 is to maintain the needed phase difference on blocks 1201 and 1202 inputs. The aim of block 1206 is to equalize the phases on block 1207, in initial state. The aim of blocks 1209 and 1210 is to equalize the amplitudes on block 121 1 , in initial state. 1207 is phase detector; 1208 is a low pass filter; 1209, 1210 are attenuators; 121 1 is a differential amplifier; 1212 is a low pass filter.

The operation of this circuit consists of two stages. The first one is the initial tuning stage, in which one tunes the TB's magnitude controller 1204 and phase shifter 1205, to achieve compensation in the desired place. In the second stage the circuit automatically adjusts itself by means of the phase shifter 1206, the magnitude controllers Rl 1209 and R2 1210, the multiplier X 1207, low pass filter 1208, Operational Amplifier 1211 , in order to retain the required values of the phase difference and amplitudes ratio.

Using this invention, it is possible to retain compensation conditions in case the surrounding conditions change, even when a metallic object or metallic wall suddenly appears, as shown in Fig. 9. This circuit thereby enables compensation under changing external environments, such as upon approaching a large metallic object.

One non limiting example of the components used in Fig. 12 is provided hereinbelow in Table 1.

Reference is now made to Fig. 13, which is a simplified pictorial illustration of a self-adjusting automatic compensation system with a time delay 1313 according to an embodiment of the present invention. For the purpose of amplitude compensation before phase compensation time delay 1313 is added to Fig. 12.

One non limiting example of the components used in a self-adjusting automatic compensation system with a time delay of Fig. 13 is provided hereinbelow in Table 2.

GLOSSARY

The following is a list of terms and the way they should be understood when used in the description given below.

Total field - a field obtainable by superposition of two and more fields produced by radiators in a given point.

Distance between an antenna and a compensation point - a distance between an antenna phase centre and an observation point. Compensation point - an observation point, in which a total field vanishes (near to zero).

Focusing spot FS- an area of weak or strong field, which arises around the compensation/focus point, relative to the case of the main antenna alone.

Distance between an antenna and a point - a distance along the horizontal straight line between an antenna base and an observation point.

The terms "radiator" and "antenna" are used herein interchangeably.

The references cited herein teach many principles that are applicable to the present invention. Therefore the full contents of these publications are incorporated by reference herein where appropriate for teachings of additional or alternative details, features and/or technical background.

It is to be understood that the invention is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the invention as hereinbefore described without departing from its scope, defined in and by the appended claims.

Claims

1. An antenna system for controlling both near and far radiation patterns, the system comprising:

a) a focusing antenna system; and

b) a control module constructed and configured to control the radiation patterns of said system,

wherein the system is adapted to provide(prevent??) a maximal predetermined level of radiation at a first short distance from a main antenna and concomitantly to provide at least a second level of radiation at at least one longer distance from the main antenna.

2. An antenna system according to claim 1, wherein said focusing antenna system comprises:

i. at least one main antenna; and

ii. at least one auxiliary antenna.

iii. TB?

3. An antenna system according to claim 2, wherein said at least one auxiliary antenna comprises at least two auxiliary antennae.

4. An antenna system according to claim 2, wherein said main antenna is constructed and configured to define a far radiation pattern at said at least one longer distance.

5. An antenna system according to claim 2, wherein said at least one auxiliary antenna is constructed and configured to define a near field radiation pattern at said first short distance.

6. An antenna system according to claim 5, wherein said near radiation pattern is at a distance less than a communication range of a device in the system.

7. An antenna system according to claim 5, wherein said at least one main antenna is installed within a communication device.

8. An antenna system according to claim 7, wherein said near field radiation pattern is selected from the group of various shapes including: a spot in a near field of the device; a ring in a near field of the device; an annulus in the near field of the device; a shell in the near field of the device; and various threshold values of radiation level.

9. An antenna system according to claim 7, wherein said device further comprises a tuning block (TB) disposed in a feeding line of each of said at least one auxiliary antenna.

10. An antenna system according to claim 8, wherein said near radiation pattern is selected from the group consisting of: a high radiation focused spot and an anti- focused spot of diminished radiation.

11. An antenna system according to claim 8, wherein at least one main antenna is constructed and configured to provide communication of said device at far field regions and said at least one auxiliary antenna is disposed proximal to said at least one main antenna in said device.

12. An antenna system according to claim 10, wherein said at least one auxiliary antenna is constructed and configured to provide a desired radiation pattern in a near field of said device, without affecting the far field performance of the main antenna.

13. A transmitting antenna system for use in a telecommunication device for creating a reduced radiation in a near field, the device comprising:

a) a telecommunication apparatus comprising a main antenna; and b) a radiation reducing unit comprising at least one auxiliary antenna connected to the signal source via a tuning block.

14. A transmitting antenna system according to claim 13, wherein said tuning block comprises a magnitude controller and a phase shifter.

15. A transmitting antenna system according to claim 13, wherein said main antenna and said at least one auxiliary antenna are of the same type but of different sizes.

16. A transmitting antenna system according to claim 13, wherein said main antenna and said at least one auxiliary antenna are of different types and of different sizes.

17. A mobile telecommunication device with reduced radiation in a near field, the device comprising:

a ) a telecommunication apparatus comprising a main antenna connected to a signal source;

b ) a radiation reducing unit including an auxiliary antenna connected to the signal source via a tuning block comprising one of: i ) a magnitude controller and a phase shifter; and

ii) a self-adjusting system including a phase shifter, a phase detector, and a self-tuning unit adapted to provide outputs of the phase tuner and the magnitude controller with certain values of phase difference and amplitudes ratio.

18. A mobile telecommunication device according to claim 17, wherein said main antenna and said auxiliary antennae are of different sizes, thereby being adapted to create a weak field disposed at any desired location.

19. A mobile telecommunication device according to claim 17, wherein said near field radiation pattern is a weak or zero field and said device is configured to use at least one reflection signal from a nearby reflecting surface for creation of a focusing spot (FS).

20. A mobile telecommunication device according to claim 19, wherein said self- tuning unit comprises a multiplier, at least one low pass filter, operational amplifiers and a phase detector, in order to allow for self adjustment of said tuning block when environmental conditions change

21. A mobile telecommunication device according to claim 20, further comprising a first connection of a phase detector followed by a low pass filter with a control input of the phase shifter and a second connection of the operational amplifier output with a control input of the magnitude controller .

22. A mobile telecommunication device according to claim 21, further comprising a time delay unit (for phase comensation???), disposed between said low pass filter and said phase tuner.

23. A mobile telecommunication device according to any of claims 17 to 22, wherein said telecommunication device is a telephone.

24. A mobile telecommunication device according to claim 23, wherein said telephone is a mobile phone.

25. A mobile telecommunication device according to claim 17, wherein said device is selected from a cordless telephone, an ad-hoc wireless communication network device using a handset; a personal assistant and a portable computer.

26. A mobile telecommunication device according to any of claims 17 to 25?? wherein said auxiliary antenna is adapted to be disposed closer to a FS of said device than said main antenna.

27. A method of radio transmission from a communication device for creating:

a) a zero (minimal) field at a compensation point P;

b) a weak field at a Focusing Spot (FS) around said compensation point; and

c) a minor change of field far from the FS in the covering area of the communication system (for which the main antenna is designed).

28. A method according to claim 27, wherein the fields of two radiators mutually compensate each other at a given point of said device, and the field magnitudes, created by these radiators, equal in this point, whereas the field phases in this point differ one from another by a value 180°.

29. A method according to claim 28, wherein a few radiators produce zero field at the compensation point P and a weak field in a FS surrounding the point P, and the weak field in the FS is substantially lower than the field, which every one of the radiators would produce in the absence of all other fields.

30. A method according to claim 29, wherein the radiators are placed in a housing of a mobile phone, in order to decrease an irradiation of user's body and to decrease the total and the local Specific Absorption Rate (SAR) inside a user's body, in particular inside of user's head and hand.

31. A method according to claim 30, wherein two fields radiated by two radiators, located at different distances from the point P and tuned to ensure the fields having the same magnitudes and opposite in phase in the point P.

32. A method according to claim 31, wherein the distance between the two radiators is λ/4 or less.

33. A method according to claim 31, wherein the distance between the antennae is small, thereby enabling construction of a compact device, with field compensation mechanism.

34. A method according to claim 33, wherein the auxiliary radiator positioned closer to the compensation point P, is performed by two radiators, placed along a straight line, perpendicular to the straight line connecting the auxiliary radiator and point P, and thereby produce a field of the half magnitude.

35. A method according to claim 34, wherein the two radiators are connected to a signal source, at that at least one of the radiators is connected to the signal source via a magnitude controller and at least one of the radiators is connected to the signal source via a phase shifter.

36. A method according to claim 35, wherein the size of one auxiliary radiator is selected in order to provide the required phase shift and the magnitude change, so as to render unnecessary the radiator connection to the signal source either via a phase shifter or via a magnitude controller.

37. A transmitter having a main antenna, and auxiliary antennae, all antennae being connected to the same signal source, wherein the antennae are designed and positioned in respect of each other in a manner enabling them to transmit signals, the superposition of which has zero intensity at a predetermined point P positioned in a transmission zone and non-zero intensity at the rest of the transmission zone.

38. A transmitter according to claim 37, wherein the size of at least one of the antennas is designed to provide for the required phase shift and amplitude control, so as to render unnecessary the connection of the antenna to the signal source via a phase shifter and an amplitude controller.

39. A phase locking method for automatic stabilization of the radiation patterns produced by a focusing antenna system, said patterns comprising both a desired focusing spot and a far field pattern, whereupon appearance of any metallic objects and/or upon proximity to different media producing a heterogeneous medium around the antenna, said automatic stabilization method ensures proper operation of said FA, even if characteristics of said antennae change.

40. A method of radio transmission according to claim 39, having an extended tuning block (TB) for automatic stabilization of said antennae, said antennae being subject to external influences.

41. A transmitting antenna module for increasing amount of radiation indoors and decreasing outdoor radiation for data security.

42. A method of radio transmission according to claim 40, for application of focusing array (FA) in electromagnetic compatibility (EMC) problems in reducing radiation levels in devices in the vicinity of the antenna.

43. A method of radio transmission according to claim 42, employing at least one focusing antenna in a dense area of antennas, the dense area comprising a plurality of receiving antennae and a plurality of transmitting antennae, for removal of any undesired radiation at a receiving antenna due to a nearby high power transmitter.

44. A method of radio transmission according to claim 40, comprising integration of at least one transmitter and at least one receiver on a single chip.

45. A three dimensional assembly of auxiliary antennae in the system, according to claim 1.

46. A focusing antenna system (FA) comprising a main antenna which is a conventional antenna array (AA) and at least one auxiliary antenna which is located opposite at least one of the of antenna array elements, thereby producing a focusing spot (FS) in the vicinity of said at least one element of the antenna array.

47. A method of design of a focusing antenna system accounting for the presence of the human body.

48. A method for solving electromagnetic compatibility (EMC) problems comprising :

a) monitoring radiation levels to characterize the exiting fields in at least one location; and

b) providing auxiliary antennae so as to reduce a radiation level by compensation at said at least one location, wherein said at least one location is selected from the group consisting of: a location on a piece of equipment; a location proximal to a piece of equipment; and a location of a known high level of radiation, thereby reducing the radiation level at said location.