EP0337025A1 - Beamforming/null-steering adaptive array - Google Patents
Beamforming/null-steering adaptive arrayInfo
- Publication number
- EP0337025A1 EP0337025A1 EP88303340A EP88303340A EP0337025A1 EP 0337025 A1 EP0337025 A1 EP 0337025A1 EP 88303340 A EP88303340 A EP 88303340A EP 88303340 A EP88303340 A EP 88303340A EP 0337025 A1 EP0337025 A1 EP 0337025A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- epoch
- output
- signal
- gate
- desired signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
- H01Q3/2605—Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
- H01Q3/2611—Means for null steering; Adaptive interference nulling
- H01Q3/2617—Array of identical elements
Definitions
- the invention generally relates to an apparatus for adaptive signal processing and, in particular, an adaptive processor including beamforming and null-steering for an array antenna.
- Phase-coded spread spectrum communication signals may be acquired and synchronized in the presence of interference with the aid of an adaptive array antenna under the control of a well-known LMS (least mean square) algorithm performing power minimization.
- LMS least mean square
- the signal to interference (S/I) ratio at the adaptive array output port of a system using this type of processing although adequate for acquisition and synchronization, provides undesirable message quality which, at best, is several decibels below the theoretical maximum obtainable when direction of arrival (beam steering) information is available.
- the spectral bandwidth of the interference source is significantly wider than the desired signal's bandwidth. Null-steering in such a case may be obtained by an LMS algorithm with spectral preconditioning of control signals of an adaptive processor to prevent null formation on the desired signal.
- the invention includes an apparatus for cancelling interference effecting a desired signal, which interference is produced by a source distant from a source of the desired signal.
- First means provides the desired signal and any undesired signal received with the desired signal and is associated with a null-steering means for separating the desired signal and the undesired signal.
- the null-steering means cancels at least a portion of the undesired signal.
- a beamforming means is also associated with the first means for separating the desired signal and the undesired signal and enhancing at least a portion of the desired signal.
- Second means are provided for coordinating the null-steering means and the beamforming means.
- the null-steering and beamforming loops employ ON and OFF epoch processors.
- the null-steering means is operative to reduce the gain of the radiation pattern of an array antenna in the direction of the source of the interference.
- the beam-forming means is operative to increase the gain of the radiation pattern of the array antenna in the direction of the source of the desired signal.
- Figures 1-3 are single line block diagrams used generally to represent a vector system with multiple signals.
- references to a "line” are intended to generally mean multiple paths transmitting more than one signal.
- references to “mixers” generally mean multiplication with vectorial weights for combining multiple signals.
- Figure 1 illustrates in block diagram form the general features of the invention. Practice of the invention is demonstrated with reference to an array antenna 300 having four antenna elements 301, 302, 303, and 304 positioned for receiving an electromagnetic signal. It should be understood that, while the invention will be described with reference to reception of electromagnetic signals, the theory of the invention is applicable equally to the reception of sonic signals in which case the elements of the antenna would be transducers for converting sonic energy to electric energy.
- the four elements 301-304 of the antenna 300 are presented by way of example, it being understood that many more elements may be employed in practice. Also, in the general case, it is to be understood that the elements 301-304 may be positioned in a straight line or on a curved surface in accordance with the circumstances under which the antenna 300 is to be deployed. The situation in which the elements of the antenna 300 are to be positioned along a curved surface is found in the locating of antenna elements on an aircraft in which case the elements may be positioned on the curved surface of a fuselage or wing of the aircraft.
- Adaptive processing of input signals received at the elements 301-304 is accomplished by adaptive signal processors 305, 306, 307, and 308, respectively, coupled to the elements 301-304.
- Output signals of the processors 305-305 are applied to input terminals of a summer 309 which sums together the output signals of the processors 305-308 to output on line 310 a combined signal of the contributions of all of the elements 301-304 of the antenna 300.
- the output signal on line 310 is also fed back to each of the processors 305-308 to be used as a reference signal in the generation of weighting factors which are applied by the processors 305-308 in an adaptive fashion to the input signals of the respective elements 301-304 in accordance with the invention as will be described hereinafter.
- each of the processors 305-308 in combination with its respective antenna element 301-304 constitutes a separate signal processing channel, each channel sharing the summer 309 in common to provide the common reference signal on line 310.
- Each of these channels operates in the same fashion and comprises the same circuitry. Accordingly, in the ensuing description of the invention, the description will be directed to the circuitry of one of the channels, namely the circuitry within the processor 305, it being understood that this description applies equally well to the other processors 306-308.
- the overall configuration of a set of processors sharing a common summer for weighting antenna signals is well known and need not be described further for an understanding of the invention. The invention resides within the circuitry of a single processor, such as the processor 305, as will now be described.
- a desired signal with undesired signals is provided by line 10 to mixer 11.
- the desired signal with interference is also provided via line 12 to beamforming circuit 200 and via line 13 to null-steering circuit 100.
- the output of null-steering circuit 100 is provided via line 14 to coordinator 15 and added to the output of beamforming circuit 200 provided via line 16.
- the coordinated sum is provided via line 9 to mixer 11, and further combined with the corresponding signals of the other channels by the summer 309, so that mixed output lines 310 and 17 carry the desired signal with interference mixed with the output of coordinator 15.
- This mixed signal is provided via line 18 to beamforming circuit 200 and via line 19 to null-steering circuit 100.
- the null-steering circuit 100 functions as a first vector loop 1 to cancel at least a portion of the interfering signals.
- the beamforming circuit 200 functions as a second vector loop 2 to enhance at least a portion of the desired signal so that the mixed signal provided by line 17 has an enhanced S/I ratio and hence message quality.
- the null-steering circuit and beamforming circuit may accomplish their functions by temporal processing or by spectral processing.
- temporal processing may be employed as illustrated in a detailed diagram of the processors 305 in Figure 2.
- the desired and interfering signals may be provided via line 10 to an automatic gain control circuit (AGC) 20 for stabilizing the signal amplitude.
- AGC automatic gain control circuit
- the output of AGC 20 is applied via line 21 to matched filter 22 and coded with the particular code of the desired signal.
- the output of matched filter 22 is provided via line 23 to first wideband vector weight control loop 1WB for null-steering and second wideband vector weight control loop 2WB for beamforming.
- first vector loop 1WB the reference signal provided by line 24 and feedback signal provided by line 25 are processed by off-epoch sample/hold filter circuit 101 and off-epoch sample/hold filter circuit 103, respectively.
- the processed signals are provided to correlator 102 for weighting the signal of antenna element 301 with the output of correlator 102 provided by line 106 to adder 28.
- the reference signal provided by line 26 and the feedback signal provided by line 27 are processed by on-epoch sample/hold filter circuit 201 and on-epoch sample/hold filter circuit 203, respectively.
- the processed signals are provided to correlator 202 for weighting with the output of the correlator 102 provided by line 206 to added 28.
- the second loop 2WB enhances the desired signal to interference power ratio of the control signal of a modified LMS algorithm effected by correlator 202 with a net positive signal shown at adder 28 representing implementation of a maximization process.
- Correlator 102 of vector loop 1WB comprises mixer 104 for mixing the output of the off-epoch circuits 101 and 103 and integrator 105 for integrating the mixed outputs.
- Correlator 202 of vector loop 2WB comprises mixer 204 for mixing the outputs of on-epoch circuits 201 and 203 and integrator 205 for integrating the mixed outputs.
- the output (line 106) of correlator 102 of loop 1WB is added to the output (line 206) of correlator 202 of loop 2WB by adder 28 and the sum is mixed by mixer 29 with the input signal provided by line 23 resulting in a mixed output signal provided by line 17.
- the epoch processing circuits 101 and 201 are fabricated conveniently as a single unit 311 and, similarly, the epoch processing circuits 103 and 203 are fabricated conveniently as a single unit 312. Both of the units 311 and 312 have the same configuration and, accordingly, only the unit 311 need be described in detail, it being understood that the description thereof applies also to the unit 312.
- a unit 311 is found in each of the processors 305-308 of Figure 1.
- a unit 312 may be placed in each of the processors 305-308 or, alternatively, only one unti 312 need to provided for the entire antenna 300, with the output signals of the single unit 312 being employed by all of the processors 305-308.
- FIG. 3 there is shown a block diagram of epoch processing circuits contained within the unit 311, the description in Figure 3 applying also to the epoch processing unit 312.
- Output signals are applied to the mixers 104 and 204 as shown in Figure 2.
- the input signal to the epoch processing circuits are obtained from line 23 in the case of the unit 311, and from the line 17 in the case of the unit 312.
- the unit 311 comprises an envelope detector 313, a threshold unit 314, a clock 315, a counter 316, and two signal generators 317 and 318 for producing an early-gate signal and a late-gate signal respectively.
- Input signals from line 23 are detected by the detector 313 which outputs the amplitude of the signal envelope to the threshold unit 314.
- the counter 316 counts clock pulses applied thereto by the clock 315.
- the threshold unit 314 outputs a command signal to the counter 316 during the interval of time when a detector 313 outputs a signal amplitude above the threshold of the unit 314. Thereby, the counter 316 is activated and deactivated to count the duration of a pulse of the input signal.
- the counter 316 strobes the generators 317 and 318.
- the strobing of the generator 317 activates the generator 317 to output an early-gate signal, indicated graphically at 319, which extends in time from a point prior to the input signal pulse to the end of the input signal pulse.
- the strobing of the generator 318 activates the generator 318 to output a late-gate signal, indicated graphically at 320, extending in time from a point at the beginning of the input pulse signal to a point after the conclusion of the input pulse signal.
- the two signals 319 and 320 overlap during the interval of time of the next anticipated occurrence of the input pulse signal.
- the units 311 further comprises two gates 321 and 322, two low-pass filters 323 and 324, and a subtractor 325. Both of the gates 321 and 322 have input terminals connected to the detector 313 for receiving signals outputted by the detector 313.
- the gates 321 is activated by the early-gate signal 319 of the generator 317 to pass detector signals to the filter 323 during the early-gate.
- the gate 322 is activated by the late-gate signal 320 of the generator 318 to pass detector signals to the filter 324 during the late-gate.
- the filters 323 and 324 average the signals applied repetitively by the gates 321 and 322.
- the average values outputted by the filters 323 and 324 are subtracted by the subtractor 325 to produce an error signal which indicates any error in the emplacement of the gate signals 319 and 320 about an input signal pulse.
- the error signal is applied to the clock 315 to advance or retard the occurrence of clock pulses as commanded by the error signal, thereby to align the overlapping region of the gate signals 319 and 320 with the input signal pulse.
- Stylized representations of the signals outputted by the early-gate 321 and the late-gate 322 are indicated at 326 and 327.
- the unit 311 also comprises two gates 328 and 329, a delay unit 330 and a summer 331.
- the summer 331 provides an AND function between the early-gate signal 319 and the late-gate signal 320 to output a signal on line 332 having a value of logic-1 during the overlap region of the two signals 319 and 320, and a value of logic-0 otherwise, the overlap region between the two signals 319 and 320 is indicated graphically at 333.
- the logic-1 signal outputted by the summer 331 is indicated at 334.
- the signal 334 indicates the expected time of arrival of the next input signal pulse on line 23, and is applied to a terminal of the gate 329 to activate the gate 329 to conduct a signal from line 23 to the mixer 204. This is termed the on-epoch part of the transmission of signals received by the antenna element 301.
- the signal 334 is also coupled via the delay 330 to a terminal of the gate 328 to activate the gate to couple signals from the line 23 to the mixer 104.
- the delay imparted by the delay unti 330 is sufficient to offset the activation interval of the gate 328 to a time after termination of the on-epoch of the gate 329. Accordingly, the interval of activation of the gate 328 is termed an off-epoch portion of the signal received at the antenna element 301.
- the epoch processing circuitry of the unit 311 provides for a tracking of the substantially periodic occurrences of pulses of the input signal outputted by the match filter on line 23.
- the tracking of the input signal pulse is employed to operate the on-epoch gate 329 and the off-epoch gate 328 to provide samples of the signal energy during the times of receipts of the desired signal, and during the times wherein an interfering signal may be received.
- the off-epoch interval provides jamming data utilized by the loop 1WB ( Figure 2) for directing a null in the direction of an interfering signal.
- the on-epoch interval provides energy of the desired signal which is employed by the loop 2WB ( Figure 2) for maximizing the gain of the antenna 300 in the direction of a source of the desired signal. It is also noted that in the operation of the processor 305, that the integration operation of the correlators 102 and 202 converts the pulsed signal outputted by the epoch gates 328 and 329 to continuous signals applied to the adder 28 for formation of a continuously present weighting factor applied to the mixer 29. Thereby, the epoch processing circuits in conjunction with the correlators provide the adaptive control, loops with the characteristic of a sample-hold filter circuit with the temporal filtering being accomplished by the late and early-gate tracking operation.
- Figures 4 and 5 illustrate the benefits of simultaneous null-steering and beamforming for a five-element random spaced array of antennas with an extent of 1 x 6 wavelengths in the azimuth plane and 2 wavelengths in elevation in a scenario consisting of three equal strength jammers (J1, J2, J3) which are 10dB above the desired signal at each antenna: Elevation Azimuth Jammer 1 (J1) 0° 0.4° Jammer 2 (J2) 0° 22.3° Jammer 3 (J3) 0° 93.8° User (5) 0° 62.2°
- Figure 4 is the adapted antenna pattern attained from a null-steering only control on the full signal band of frequencies for a loop bias condition which results in a single element "on" quiescent weight vector.
- all the jammers are nulled by about 30dB and the desired signal(s) falls on the sides of a null which leads to a net improvement in S/J (signal to jammer) ratio of about 22dB.
- Figure 5 is the adapted pattern for the same scenario when the adaptive processor is configured according to the invention employing both null-steering and beamforming. In this adapted state, the null in the vicinity of the desired signal(s) is filled in leading to an additional 6dB improvement in S/J ratio.
Abstract
Description
- The invention generally relates to an apparatus for adaptive signal processing and, in particular, an adaptive processor including beamforming and null-steering for an array antenna.
- Phase-coded spread spectrum communication signals may be acquired and synchronized in the presence of interference with the aid of an adaptive array antenna under the control of a well-known LMS (least mean square) algorithm performing power minimization. However, the signal to interference (S/I) ratio at the adaptive array output port of a system using this type of processing, although adequate for acquisition and synchronization, provides undesirable message quality which, at best, is several decibels below the theoretical maximum obtainable when direction of arrival (beam steering) information is available.
- In narrow band interference (e.g., AM radios) communication systems, the spectral bandwidth of the interference source is significantly wider than the desired signal's bandwidth. Null-steering in such a case may be obtained by an LMS algorithm with spectral preconditioning of control signals of an adaptive processor to prevent null formation on the desired signal.
- It is an object of this invention to provide an adaptive processor which performs simultaneously beamforming and null-steering.
- It is another object of this invention to provide adaptive processing with a first adaptive control loop having off-epoch sample/hold filters and a second adaptive control loop having on-epoch sample/hold filters.
- The invention includes an apparatus for cancelling interference effecting a desired signal, which interference is produced by a source distant from a source of the desired signal. First means provides the desired signal and any undesired signal received with the desired signal and is associated with a null-steering means for separating the desired signal and the undesired signal. The null-steering means cancels at least a portion of the undesired signal. A beamforming means is also associated with the first means for separating the desired signal and the undesired signal and enhancing at least a portion of the desired signal. Second means are provided for coordinating the null-steering means and the beamforming means. The null-steering and beamforming loops employ ON and OFF epoch processors. The null-steering means is operative to reduce the gain of the radiation pattern of an array antenna in the direction of the source of the interference. The beam-forming means is operative to increase the gain of the radiation pattern of the array antenna in the direction of the source of the desired signal.
- For a better understanding of the present invention, together with other and further objects, reference is made to the following description, taken in conjunction with the accompanying drawings, and its scope will be pointed out in the appended claims.
- Figure 1 is a block diagram of an array antenna with adaptive processor according to the invention.
- Figure 2 is a block diagram of a wideband spread spectrum temporal processor for one of a set of signal channels of Figure 1 according to the invention.
- Figure 3 is a block diagram of an epoch processor of Figure 2 according to the invention.
- Figure 4 is an array antenna pattern in the horizontal plane illustrating null-steering simulation.
- Figure 5 is an array antenna pattern in the horizontal plane illustrating beamforming/null-steering simulation according to the invention.
- Figures 1-3 are single line block diagrams used generally to represent a vector system with multiple signals. As used herein, references to a "line" are intended to generally mean multiple paths transmitting more than one signal. Similarly, references to "mixers" generally mean multiplication with vectorial weights for combining multiple signals.
- Figure 1 illustrates in block diagram form the general features of the invention. Practice of the invention is demonstrated with reference to an
array antenna 300 having fourantenna elements antenna 300 are presented by way of example, it being understood that many more elements may be employed in practice. Also, in the general case, it is to be understood that the elements 301-304 may be positioned in a straight line or on a curved surface in accordance with the circumstances under which theantenna 300 is to be deployed. The situation in which the elements of theantenna 300 are to be positioned along a curved surface is found in the locating of antenna elements on an aircraft in which case the elements may be positioned on the curved surface of a fuselage or wing of the aircraft. - Adaptive processing of input signals received at the elements 301-304 is accomplished by
adaptive signal processors summer 309 which sums together the output signals of the processors 305-308 to output on line 310 a combined signal of the contributions of all of the elements 301-304 of theantenna 300. The output signal online 310 is also fed back to each of the processors 305-308 to be used as a reference signal in the generation of weighting factors which are applied by the processors 305-308 in an adaptive fashion to the input signals of the respective elements 301-304 in accordance with the invention as will be described hereinafter. - It is noted that each of the processors 305-308 in combination with its respective antenna element 301-304 constitutes a separate signal processing channel, each channel sharing the
summer 309 in common to provide the common reference signal online 310. Each of these channels operates in the same fashion and comprises the same circuitry. Accordingly, in the ensuing description of the invention, the description will be directed to the circuitry of one of the channels, namely the circuitry within theprocessor 305, it being understood that this description applies equally well to the other processors 306-308. The overall configuration of a set of processors sharing a common summer for weighting antenna signals is well known and need not be described further for an understanding of the invention. The invention resides within the circuitry of a single processor, such as theprocessor 305, as will now be described. - As shown in Figure 1, a desired signal with undesired signals (i.e., interference) is provided by
line 10 to mixer 11. The desired signal with interference is also provided vialine 12 to beamformingcircuit 200 and vialine 13 to null-steering circuit 100. The output of null-steering circuit 100 is provided vialine 14 tocoordinator 15 and added to the output ofbeamforming circuit 200 provided vialine 16. The coordinated sum is provided via line 9 to mixer 11, and further combined with the corresponding signals of the other channels by thesummer 309, so thatmixed output lines coordinator 15. This mixed signal is provided vialine 18 to beamformingcircuit 200 and vialine 19 to null-steering circuit 100. Effectively, the null-steering circuit 100 functions as afirst vector loop 1 to cancel at least a portion of the interfering signals. Conversely, thebeamforming circuit 200 functions as asecond vector loop 2 to enhance at least a portion of the desired signal so that the mixed signal provided byline 17 has an enhanced S/I ratio and hence message quality. - The null-steering circuit and beamforming circuit may accomplish their functions by temporal processing or by spectral processing. In the processing of phase-coded wideband spread spectrum communication signals, temporal processing may be employed as illustrated in a detailed diagram of the
processors 305 in Figure 2. - As shown in Figure 2, the desired and interfering signals may be provided via
line 10 to an automatic gain control circuit (AGC) 20 for stabilizing the signal amplitude. The output ofAGC 20 is applied vialine 21 to matchedfilter 22 and coded with the particular code of the desired signal. The output of matchedfilter 22 is provided vialine 23 to first wideband vector weight control loop 1WB for null-steering and second wideband vector weight control loop 2WB for beamforming. In the first vector loop 1WB, the reference signal provided byline 24 and feedback signal provided byline 25 are processed by off-epoch sample/holdfilter circuit 101 and off-epoch sample/hold filter circuit 103, respectively. The processed signals are provided tocorrelator 102 for weighting the signal ofantenna element 301 with the output ofcorrelator 102 provided byline 106 to adder 28. This effectively removes the desired signal from the control signal of a modified LMS algorithm effected in loop 1WB bycorrelator 102 with the minus sign in the vector loop 1WB shown atadder 28 representing implementation of a minimization process. - In the second vector loop 2WB, the reference signal provided by
line 26 and the feedback signal provided byline 27 are processed by on-epoch sample/holdfilter circuit 201 and on-epoch sample/holdfilter circuit 203, respectively. The processed signals are provided tocorrelator 202 for weighting with the output of thecorrelator 102 provided byline 206 to added 28. The second loop 2WB enhances the desired signal to interference power ratio of the control signal of a modified LMS algorithm effected bycorrelator 202 with a net positive signal shown atadder 28 representing implementation of a maximization process. -
Correlator 102 of vector loop 1WB comprisesmixer 104 for mixing the output of the off-epoch circuits integrator 105 for integrating the mixed outputs.Correlator 202 of vector loop 2WB comprisesmixer 204 for mixing the outputs of on-epoch circuits integrator 205 for integrating the mixed outputs. The output (line 106) ofcorrelator 102 of loop 1WB is added to the output (line 206) ofcorrelator 202 of loop 2WB byadder 28 and the sum is mixed bymixer 29 with the input signal provided byline 23 resulting in a mixed output signal provided byline 17. - The
epoch processing circuits single unit 311 and, similarly, theepoch processing circuits single unit 312. Both of theunits unit 311 need be described in detail, it being understood that the description thereof applies also to theunit 312. Aunit 311 is found in each of the processors 305-308 of Figure 1. Also, aunit 312 may be placed in each of the processors 305-308 or, alternatively, only one unti 312 need to provided for theentire antenna 300, with the output signals of thesingle unit 312 being employed by all of the processors 305-308. - With reference to Figure 3, there is shown a block diagram of epoch processing circuits contained within the
unit 311, the description in Figure 3 applying also to theepoch processing unit 312. Output signals are applied to themixers line 23 in the case of theunit 311, and from theline 17 in the case of theunit 312. - The
unit 311 comprises anenvelope detector 313, athreshold unit 314, aclock 315, acounter 316, and twosignal generators 317 and 318 for producing an early-gate signal and a late-gate signal respectively. Input signals fromline 23 are detected by thedetector 313 which outputs the amplitude of the signal envelope to thethreshold unit 314. Thecounter 316 counts clock pulses applied thereto by theclock 315. Thethreshold unit 314 outputs a command signal to thecounter 316 during the interval of time when adetector 313 outputs a signal amplitude above the threshold of theunit 314. Thereby, thecounter 316 is activated and deactivated to count the duration of a pulse of the input signal. Thecounter 316 strobes thegenerators 317 and 318. In the case of a repetitive input signal, as is the usual case in radar communication, the strobing of thegenerator 317 activates thegenerator 317 to output an early-gate signal, indicated graphically at 319, which extends in time from a point prior to the input signal pulse to the end of the input signal pulse. Similarly, the strobing of the generator 318 activates the generator 318 to output a late-gate signal, indicated graphically at 320, extending in time from a point at the beginning of the input pulse signal to a point after the conclusion of the input pulse signal. The twosignals - The
units 311 further comprises twogates pass filters subtractor 325. Both of thegates detector 313 for receiving signals outputted by thedetector 313. Thegates 321 is activated by theearly-gate signal 319 of thegenerator 317 to pass detector signals to thefilter 323 during the early-gate. Thegate 322 is activated by thelate-gate signal 320 of the generator 318 to pass detector signals to thefilter 324 during the late-gate. Thefilters gates filters subtractor 325 to produce an error signal which indicates any error in the emplacement of the gate signals 319 and 320 about an input signal pulse. The error signal is applied to theclock 315 to advance or retard the occurrence of clock pulses as commanded by the error signal, thereby to align the overlapping region of the gate signals 319 and 320 with the input signal pulse. Stylized representations of the signals outputted by the early-gate 321 and the late-gate 322 are indicated at 326 and 327. - The
unit 311 also comprises twogates delay unit 330 and asummer 331. Thesummer 331 provides an AND function between theearly-gate signal 319 and thelate-gate signal 320 to output a signal online 332 having a value of logic-1 during the overlap region of the twosignals signals summer 331 is indicated at 334. - The
signal 334 indicates the expected time of arrival of the next input signal pulse online 23, and is applied to a terminal of thegate 329 to activate thegate 329 to conduct a signal fromline 23 to themixer 204. This is termed the on-epoch part of the transmission of signals received by theantenna element 301. Thesignal 334 is also coupled via thedelay 330 to a terminal of thegate 328 to activate the gate to couple signals from theline 23 to themixer 104. The delay imparted by thedelay unti 330 is sufficient to offset the activation interval of thegate 328 to a time after termination of the on-epoch of thegate 329. Accordingly, the interval of activation of thegate 328 is termed an off-epoch portion of the signal received at theantenna element 301. - In operation, the epoch processing circuitry of the
unit 311 provides for a tracking of the substantially periodic occurrences of pulses of the input signal outputted by the match filter online 23. The tracking of the input signal pulse is employed to operate the on-epoch gate 329 and the off-epoch gate 328 to provide samples of the signal energy during the times of receipts of the desired signal, and during the times wherein an interfering signal may be received. The off-epoch interval provides jamming data utilized by the loop 1WB (Figure 2) for directing a null in the direction of an interfering signal. The on-epoch interval provides energy of the desired signal which is employed by the loop 2WB (Figure 2) for maximizing the gain of theantenna 300 in the direction of a source of the desired signal. It is also noted that in the operation of theprocessor 305, that the integration operation of thecorrelators epoch gates adder 28 for formation of a continuously present weighting factor applied to themixer 29. Thereby, the epoch processing circuits in conjunction with the correlators provide the adaptive control, loops with the characteristic of a sample-hold filter circuit with the temporal filtering being accomplished by the late and early-gate tracking operation. - Figures 4 and 5 illustrate the benefits of simultaneous null-steering and beamforming for a five-element random spaced array of antennas with an extent of 1 x 6 wavelengths in the azimuth plane and 2 wavelengths in elevation in a scenario consisting of three equal strength jammers (J1, J2, J3) which are 10dB above the desired signal at each antenna:
Elevation Azimuth Jammer 1 (J1) 0° 0.4° Jammer 2 (J2) 0° 22.3° Jammer 3 (J3) 0° 93.8° User (5) 0° 62.2° - Figure 4 is the adapted antenna pattern attained from a null-steering only control on the full signal band of frequencies for a loop bias condition which results in a single element "on" quiescent weight vector. In the adapted state, all the jammers are nulled by about 30dB and the desired signal(s) falls on the sides of a null which leads to a net improvement in S/J (signal to jammer) ratio of about 22dB. Figure 5 is the adapted pattern for the same scenario when the adaptive processor is configured according to the invention employing both null-steering and beamforming. In this adapted state, the null in the vicinity of the desired signal(s) is filled in leading to an additional 6dB improvement in S/J ratio.
Claims (7)
- Claim 1. Apparatus for suppressing undesired signals received with a desired spread spectrum signal, said apparatus comprising:(a) first means (301, 10) for supplying the desired signal and any undesired signals received with the desired signal;(b) second means (100), responsive to signals supplied by said first means, for separating the desired and any undesired signals and cancelling at least a portion of any undesired signals;(c) third means (200), also responsive to signals supplied by said first means, for separating the desired and any undesired signals and enhancing at least a portion of the desired signal; and(d) fourth means (11, 15, 309) for combining the outputs of said second and third means to develop an output signal having an enhanced signal-to-interference ratio with respect to said desired signal.
- Claim 2. The apparatus of claim 1 wherein said second means comprises a first adaptive control loop (1) coupled to said first means, said first loop having a negative correcting output for minimizing the undesired signal;
said third means comprises a second adaptive control loop (2) coupled to said first means, said second loop having a positive correcting output for maximizing the desired signal; and
said fourth means comprises means (15) for summing the negative correcting output and the positive correcting output and a mixer (11) for mixing the desired and any undesired signals supplied by said first means with said sum to provide said output signal. - Claim 3. The apparatus of claim 2 wherein said means for summing is an adder (28) having a first input coupled to said positive correcting output, a second input coupled to said negative correcting output, and having its output coupled to an input of said mixer (11).
- Claim 4. The apparatus of claim 2 wherein said first adaptive control loop (1) comprises a first off-epoch sample/hold filter circuit (101) coupled to the first means and providing an off-epoch unmixed output, a second off-epoch sample/hold filter circuit (103) coupled to the mixer output and providing an off-epoch mixed output, and a correlator (102) correlating the off-epoch unmixed output with the off-epoch mixed output to provide the negative correcting output.
- Claim 5. The apparatus of claim 4 wherein each of said epoch filter circuits (101, 103) includes means for tracking a desired signal, said tracking means including an early-gate and a late-gate overlapping a time of occurrence of the desired signal, there being an off-epoch gate and an on-epoch gate driven by said tracking means for extracting samples of the desired signal and any undesired signals.
- Claim 6. The apparatus of claim 2 wherein said second adaptive control loop (2) comprises a first on-epoch sample/hold filter circuit (201) coupled to the first means and providing an on-epoch unmixed output, a second on-epoch sample/hold filter circuit (203) coupled to the mixer output and providing an on-epoch mixed output, and a correlator (102) correlating the on-epoch unmixed output with the on-epoch mixed output to provide the positive correcting output.
- Claim 7. The apparatus of claim 6 wherein each of said epoch filter circuits (101, 103, 201, 203) includes means for tracking a desired signal, said tracking means including an early-gate and a late-gate overlapping a time of occurrence of the desired signal, there being an off-epoch gate and an on-epoch gate driven by said tracking means for extracting samples of the desired signal and any undesired signals.
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/017,109 US4771289A (en) | 1982-05-28 | 1987-02-20 | Beamforming/null-steering adaptive array |
CA000563730A CA1325260C (en) | 1982-05-28 | 1988-04-08 | Beamforming/null-steering adaptive array |
DE3885089T DE3885089T2 (en) | 1988-04-08 | 1988-04-13 | Antenna system with antenna diagram adapting to useful and interference signals. |
EP88303340A EP0337025B1 (en) | 1988-04-08 | 1988-04-13 | Beamforming/null-steering adaptive array |
AU14750/88A AU602974B2 (en) | 1988-04-08 | 1988-04-19 | Beamforming/null-steering adaptive array |
JP63109825A JPH01293002A (en) | 1988-04-08 | 1988-05-02 | Beam forming/zero sensitivity navigation optimum array |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA000563730A CA1325260C (en) | 1982-05-28 | 1988-04-08 | Beamforming/null-steering adaptive array |
EP88303340A EP0337025B1 (en) | 1988-04-08 | 1988-04-13 | Beamforming/null-steering adaptive array |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0337025A1 true EP0337025A1 (en) | 1989-10-18 |
EP0337025B1 EP0337025B1 (en) | 1993-10-20 |
Family
ID=25671828
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP88303340A Expired - Lifetime EP0337025B1 (en) | 1982-05-28 | 1988-04-13 | Beamforming/null-steering adaptive array |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0337025B1 (en) |
JP (1) | JPH01293002A (en) |
AU (1) | AU602974B2 (en) |
DE (1) | DE3885089T2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4415282A1 (en) * | 1994-04-30 | 1995-11-02 | Sel Alcatel Ag | Multipath reception radio receiver |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4079381A (en) * | 1976-11-22 | 1978-03-14 | Motorola, Inc. | Null steering apparatus for a multiple antenna array on an AM receiver |
US4156877A (en) * | 1978-01-16 | 1979-05-29 | Motorola, Inc. | In null steering apparatus a reference to spread spectrum signals |
US4173759A (en) * | 1978-11-06 | 1979-11-06 | Cubic Corporation | Adaptive antenna array and method of operating same |
US4225870A (en) * | 1978-05-10 | 1980-09-30 | The United States Of America As Represented By The Secretary Of The Army | Null steering antenna |
GB2122053A (en) * | 1982-05-28 | 1984-01-04 | Hazeltine Corp | Beamforming/null-steering adaptive array |
US4516126A (en) * | 1982-09-30 | 1985-05-07 | Hazeltine Corporation | Adaptive array having an auxiliary channel notched pattern in the steered beam direction |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL7106554A (en) * | 1971-05-13 | 1972-11-15 | ||
US4344150A (en) * | 1980-07-10 | 1982-08-10 | Newmont Mining Corporation | Coherent noise cancelling filter |
US4648118A (en) * | 1984-04-20 | 1987-03-03 | Matsushita Electric Industrial Co., Ltd. | Apparatus for reducing noise in audio signals |
-
1988
- 1988-04-13 DE DE3885089T patent/DE3885089T2/en not_active Expired - Fee Related
- 1988-04-13 EP EP88303340A patent/EP0337025B1/en not_active Expired - Lifetime
- 1988-04-19 AU AU14750/88A patent/AU602974B2/en not_active Ceased
- 1988-05-02 JP JP63109825A patent/JPH01293002A/en active Pending
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4079381A (en) * | 1976-11-22 | 1978-03-14 | Motorola, Inc. | Null steering apparatus for a multiple antenna array on an AM receiver |
US4156877A (en) * | 1978-01-16 | 1979-05-29 | Motorola, Inc. | In null steering apparatus a reference to spread spectrum signals |
US4225870A (en) * | 1978-05-10 | 1980-09-30 | The United States Of America As Represented By The Secretary Of The Army | Null steering antenna |
US4173759A (en) * | 1978-11-06 | 1979-11-06 | Cubic Corporation | Adaptive antenna array and method of operating same |
GB2122053A (en) * | 1982-05-28 | 1984-01-04 | Hazeltine Corp | Beamforming/null-steering adaptive array |
US4516126A (en) * | 1982-09-30 | 1985-05-07 | Hazeltine Corporation | Adaptive array having an auxiliary channel notched pattern in the steered beam direction |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4415282A1 (en) * | 1994-04-30 | 1995-11-02 | Sel Alcatel Ag | Multipath reception radio receiver |
Also Published As
Publication number | Publication date |
---|---|
JPH01293002A (en) | 1989-11-27 |
DE3885089D1 (en) | 1993-11-25 |
AU602974B2 (en) | 1990-11-01 |
EP0337025B1 (en) | 1993-10-20 |
DE3885089T2 (en) | 1994-05-19 |
AU1475088A (en) | 1989-12-21 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4771289A (en) | Beamforming/null-steering adaptive array | |
US4516126A (en) | Adaptive array having an auxiliary channel notched pattern in the steered beam direction | |
CA2397131C (en) | Linear signal separation using polarization diversity | |
US4628320A (en) | Cancellation of scatter jamming | |
US4280128A (en) | Adaptive steerable null antenna processor | |
US4268829A (en) | Steerable null antenna processor with gain control | |
AU559567B2 (en) | Adaptive antenna array | |
US3202990A (en) | Intermediate frequency side-lobe canceller | |
US3987444A (en) | Interference rejection system for multi-beam antenna having single control loop | |
GB2262009A (en) | Beamforming communications | |
US4097866A (en) | Multilevel sidelobe canceller | |
US4388723A (en) | Control device for steerable null antenna processor | |
US4651155A (en) | Beamforming/null-steering adaptive array | |
US4129873A (en) | Main lobe signal canceller in a null steering array antenna | |
US3938154A (en) | Modified sidelobe canceller system | |
US4495502A (en) | Multiple loop sidelobe canceller | |
US4800390A (en) | Adaptive antenna arrays for frequency hopped systems | |
US3938153A (en) | Sidelobe canceller system | |
US3916408A (en) | Radar receiver having clutter and large signal reduction | |
US5361074A (en) | Mainlobe canceller system | |
US4586048A (en) | Sidelobe canceller | |
US3981014A (en) | Interference rejection system for multi-beam antenna | |
US4549183A (en) | Interference suppressor for an electronically or mechanically scanning monopulse radar generating sum and difference signals from received microwave energy | |
EP0337025B1 (en) | Beamforming/null-steering adaptive array | |
US4439769A (en) | Combined adaptive sidelobe canceller and frequency filter system |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): DE GB IT |
|
17P | Request for examination filed |
Effective date: 19900412 |
|
17Q | First examination report despatched |
Effective date: 19920708 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE GB IT |
|
ITF | It: translation for a ep patent filed |
Owner name: JACOBACCI CASETTA & PERANI S.P.A. |
|
REF | Corresponds to: |
Ref document number: 3885089 Country of ref document: DE Date of ref document: 19931125 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed | ||
REG | Reference to a national code |
Ref country code: GB Ref legal event code: IF02 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20040512 Year of fee payment: 17 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20040601 Year of fee payment: 17 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED. Effective date: 20050413 Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20050413 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20051101 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20050413 |