WO2002095961A2 - A method and electronic circuit for detecting an alternating current component - Google Patents
A method and electronic circuit for detecting an alternating current component Download PDFInfo
- Publication number
- WO2002095961A2 WO2002095961A2 PCT/IB2002/001821 IB0201821W WO02095961A2 WO 2002095961 A2 WO2002095961 A2 WO 2002095961A2 IB 0201821 W IB0201821 W IB 0201821W WO 02095961 A2 WO02095961 A2 WO 02095961A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- dale
- detection signal
- detection
- detector
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/1027—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/1081—Reduction of multipath noise
Definitions
- the present invention relates to the field of detecting an alternating current component in a signal, in particular for application in communication systems, and more particularly, to the detection of co-channel interference and multi path interference.
- a variety of conventional detectors for the detection of a low frequency component in a signal having a direct current (DC) offset is known.
- a detector typically contains a direct current blocker and an amplitude detector for detecting the amplitude of a residual alternating current component.
- the direct current blocker must have a very low cut-off frequency (e.g. 0,1 Hz) in order to enable the amplitude detector to detect low frequency alternating current components.
- the step response of such a direct current blocker has a settlement time in the order of multiple seconds.
- the detection of the low- frequency alternating current component can only start after the output of the direct current blocker has settled and has reached its end value. Hence, the time required for the detection of the alternating current component is relatively long and not acceptable for some applications.
- U.S. Pat.No. 4,998,289 shows an interference detecting circuit which is used in a cellular radio telephone communication system.
- the circuit includes a logarithmic envelope detector for receiving a channel's angular modulated signal and for providing a log envelope output signal, a high pass filter for removing a particular range of undesired frequencies from the log envelope output signal, and a level detector for indicating the level of the filtered output signal.
- the output of the level detector represents the amount of interference on the angular modulated frequency signal.
- the level detector includes a maximum peak detector and a minimum peak detector for respectively detecting the envelope's functions maxima and minima.
- a microcomputer When a threshold level is exceeded, a microcomputer is alarmed in order to indicate that the co-channel and / or multi path interference has exceeded an acceptable level.
- This prior art level detector is deficient as small voltage ripples are also detected as voltage swings such that the output provided by the level detector can be random.
- the invention allows to detect an alternating current component in a signal having a direct current offset in an efficient and reliable way.
- the invention can be used even if the direct current component of the signal varies. This is particularly beneficial for applications in receivers during the tuning to a desired frequency.
- the detection of the alternating current component can be performed with a minimal time delay. This is due to the fact that a direct current blocker which typically has a settlement time in the order of seconds is not required. Rather the detection of an alternating current component is directly performed on the signal containing the direct current component.
- the reliability of the detection is further increased if hold detectors are used in conjunction with respective top and dale detectors. This allows to indicate a maximum or minimum of the signal only when the signal has a waveform with a predefined minimal peak to peak value. This avoids a random output signal of the detector due to small signal ripples.
- the reliability of the detection is further increased by alternately enabling the top detector and the dale detector. This way only the top detector or the dale detector is enabled at a given time. This way it is ensured that a minimum can only be detected if a maximum has been detected before and vice versa.
- the detection signals for the detection of minima and maxima of the alternating current component are counted. The counter value is compared to a counter threshold value. If the counter value surpasses the counter threshold value this indicates that an acceptable level of co-channel and / or multi path interference has been exceeded.
- the counter is periodically reset at predetermined time intervals.
- Fig. 1 is a block diagram of an embodiment of the circuit for detecting an alternating current component
- Fig. 2 is a signal diagram illustrating the detection of the alternating current component by means of the circuit of Fig. 1,
- Fig. 3 shows a variety of internal signals of the circuit of Fig. 1 to illustrate the operation of the circuit
- Fig. 4 is a block diagram of a receiver including a co-channel interference detection.
- Fig. 1 shows an electronic circuit for detecting an alternating current component of the input signal SI.
- the input signal SI is applied to a maximum hold detector 1, to a minimum hold detector 2 as well as to top detector 3 and dale detector 4.
- the maximum hold detector 1 has an output signal S2 which is inputted into the top detector 3.
- the signal S2 produced by the maximum hold detector 1 is representative of a maximum value the input signal has reached after the last reset of the maximum hold detector 1.
- the minimum hold detector 2 has an output signal S4 which is inputted into the dale detector 4.
- the signal S4 produced by the minimum hold detector 2 is representative of a minimum value of the input signal after the last resets of the minimum hold detector 2.
- the top detector 3 has an output signal S3 which indicates the detection of a maximum in the input signal SI.
- the dale detector 4 has an output signal S5 which indicates the detection of a minimum in the input signal SI .
- the signal S3 of the top detector 3 is provided as a reset pulse to the dale detector 4 and to the minimum hold detector 2.
- the detection of a maximum of the input signal as indicated by the signal S3 resets the minimum hold detector 2 and the dale detector 4 for a subsequent detection of a minimum of the input signal.
- the signal S5 of the dale detector 4 is provided as a reset signal to the maximum hold detector 1 and the top detector 3 to enable the detection of a maximum of the input signal after a minimum has been detected. Further the top detector 3 and the dale detector 4 have an control input Th for entering a detector threshold signal.
- the detector threshold signal is representative of a threshold value for the purposes of the detection of an input signal maximum and minimum.
- the detector threshold specifies the minimum peak-to-peak value between an maximum and a consecutive minimum of the input signal waveform which is to be considered as a relevant voltage swing.
- the top detector 3 compares the input signal SI to the signal S2.
- the signals S3 and S5 are provided to a counter 5 for counting of the respective signal pulses.
- the counter 5 has a reset which is coupled to a timer 6. The timer 6 resets the counter 5 at predetermined time intervals.
- an AM receiver - which is not shown in Fig. 2 - is tuned to a certain frequency.
- the counter 5 is reset and counts the pulses provided by signals S3 and S5 for a pre-defined period. After this period has lapsed the interference-flag 9 is checked. The detector is now disabled until the receiver is tuned to a new frequency.
- the counter 5 has an output coupled to a comparator 7.
- the comparator 7 compares the counter value of the counter 5 to a threshold provided by memory 8 which is coupled to the comparator 7. When the counter value of the counter 5 exceeds the threshold of memory 8 the comparator 7 produces an output signal in order to set the flag 9. When the flag 9 is set this indicates that an alternating current component has been detected. In particular this can be used for the detection of an unacceptable level of co-channel and / or multi path interference.
- the maximum hold detector 1 and the minimum hold detector 2 can be switched to a follow-mode by applying a corresponding control signal to respective inputs of the maximum hold detector 1 and the minimum hold detector 2. In this case the outputs of the maximum hold detector 1 and the minimum hold detector 2 are equal to the input signal SI such that the detectors have a correct initial value to start from. This further improves the detection speed.
- Fig. 2 shows an example of the waveform of the input signal SI of Fig. 1.
- the signal SI has a minimum MINI and a subsequent maximum MAX1.
- the minimum MINI is detected by the dale detector 4 of Fig. 1 when the signal SI has increased by the detector threshold value Th with respect to the minimum MINI .
- the detection of the minimum MINI at this point enables the top detector 3 by resetting both the maximum hold detector 1 and the top detector 3.
- the maximum MAXl is detected when the signal SI has fallen below the signal level MAXl by the detector threshold value Th.
- the corresponding output pulse (signal S3) of the top detector 3 enables the dale detector 4 for the detection of a subsequent minimum of the signal SI.
- Fig. 3 shows another example of the waveform of the input signal SI of the circuit of Fig.
- the signal S3 consists of a sequence of pulses which are output by the top detector 3 (cf. Fig. 1) when the signal SI has dropped back by the detector threshold value Th after having reached a maximum.
- Fig. 3 Below the signal S3 the signal S4 of the minimum hold detector 2 (cf. Fig. 1) is depicted in Fig. 3. As it is apparent from Fig. 3 each pulse of the signal S3 resets the minimum hold detector 2 such that the corresponding waveform of the signal S4 results. Further the signal S5 is shown below the signal S4. The signal S5 also consists of a series of pulses. Each pulse indicates the detection of a minimum in the signal SI. A pulse is only output by the dale detector 4 after the signal SI has increased by the detector threshold value Th after having reached a prior minimum. Fig. 4 shows a co-channel interference detector. Co-channel interference detectors typically are used in communication systems and receivers, and in particular in mobile phones and car-radio systems.
- An amplitude modulated intermediate frequency signal AM-IF is provided by a receiver circuitry which is not shown in Fig. 4.
- the AM-IF signal is input into an intermediate frequency level detector 10 which produces a direct current output signal having a ripple in the case of co-channel and / or multi path interference.
- the frequency of the ripple is in the order of 1 to 40 Hz.
- the output signal of the intermediate frequency level detector 10 is low pass filtered by low pass filter 11.
- the low pass filter 11 has a cut- off frequency of 40 Hz such that audio frequency components are removed and the direct current and ripple components are passed.
- the output of the low pass filter 11 is provided to a circuit 12 of the type as depicted in Fig. 1.
- the circuit 12 has an output signal to indicate the presence of a co-channel interference and / or of multi-path interference. This output signal of the circuit 12 can be provided to a microprocessor of the receiver of Fig. 4 (not shown in the drawing) to indicate the presence of interference.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002592304A JP2004520774A (en) | 2001-05-25 | 2002-05-22 | Method and electronic circuit for detecting AC component |
EP02730607A EP1396086A2 (en) | 2001-05-25 | 2002-05-22 | A method and electronic circuit for detecting an alternating current component |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP01201966 | 2001-05-25 | ||
EP01201966.7 | 2001-05-25 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2002095961A2 true WO2002095961A2 (en) | 2002-11-28 |
WO2002095961A3 WO2002095961A3 (en) | 2003-02-13 |
Family
ID=8180367
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2002/001821 WO2002095961A2 (en) | 2001-05-25 | 2002-05-22 | A method and electronic circuit for detecting an alternating current component |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP1396086A2 (en) |
JP (1) | JP2004520774A (en) |
WO (1) | WO2002095961A2 (en) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4998289A (en) * | 1988-06-02 | 1991-03-05 | Motorola, Inc. | Signal integrity control technique for an RF communication system |
US5555452A (en) * | 1995-05-12 | 1996-09-10 | Callaway, Jr.; Edgar H. | Peak and valley signal measuring circuit using single digital-to-analog converter |
US5949827A (en) * | 1997-09-19 | 1999-09-07 | Motorola, Inc. | Continuous integration digital demodulator for use in a communication device |
US5966406A (en) * | 1996-12-30 | 1999-10-12 | Windbond Electronics Corp. | Method and apparatus for noise burst detection in signal processors |
-
2002
- 2002-05-22 WO PCT/IB2002/001821 patent/WO2002095961A2/en not_active Application Discontinuation
- 2002-05-22 EP EP02730607A patent/EP1396086A2/en not_active Withdrawn
- 2002-05-22 JP JP2002592304A patent/JP2004520774A/en not_active Withdrawn
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4998289A (en) * | 1988-06-02 | 1991-03-05 | Motorola, Inc. | Signal integrity control technique for an RF communication system |
US5555452A (en) * | 1995-05-12 | 1996-09-10 | Callaway, Jr.; Edgar H. | Peak and valley signal measuring circuit using single digital-to-analog converter |
US5966406A (en) * | 1996-12-30 | 1999-10-12 | Windbond Electronics Corp. | Method and apparatus for noise burst detection in signal processors |
US5949827A (en) * | 1997-09-19 | 1999-09-07 | Motorola, Inc. | Continuous integration digital demodulator for use in a communication device |
Also Published As
Publication number | Publication date |
---|---|
WO2002095961A3 (en) | 2003-02-13 |
EP1396086A2 (en) | 2004-03-10 |
JP2004520774A (en) | 2004-07-08 |
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