JP4269820B2 - Digital receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital receiver.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a wireless receiving device, one having a configuration for removing a correlated noise signal described in Patent Document 1, for example, is known. FIG. 2 is a block diagram showing a generalized wireless receiving device 70 of Patent Document 1. In FIG. As shown in the figure, this radio receiving apparatus 70 receives a desired signal S mixed with a correlated noise signal N as ambient noise with one antenna 71. Then, the radio reception device 70 down-converts the received signal to a desired frequency band in the high frequency processing unit 72 and further A / D converts it in the A / D conversion unit 73, thereby corresponding digital signal (S ″ + N ″). ) And output to the noise removing unit 74. In addition, the wireless reception device 70 receives the noise signal N with the other antenna 75. Then, the radio reception device 70 down-converts the received signal to a desired frequency band in the high frequency processing unit 77 of the reference noise signal output unit 76 and further A / D converts it in the A / D conversion unit 78 to thereby generate a noise signal. A reference noise signal Nr having a correlation with N is generated and output to the noise removing unit 74.
[0003]
The noise removing unit 74 generates a noise cancellation signal AN through the adaptive filter unit 79 based on the reference noise signal Nr, and the input signal (S ″ + N ″) from the antenna 71 side is added by the adder 80. In addition, the noise signal N is removed. The filter coefficient of the adaptive filter unit 79 is sequentially updated by the filter coefficient update unit 81 so that the noise signal N (N ″) is reduced most.
[0004]
As another conventional radio receiving apparatus, for example, one having a configuration for removing a non-correlated noise signal described in Patent Document 2, in other words, a configuration for extracting only a correlated signal is known. It has been. FIG. 3 is a block diagram showing a generalized wireless receiver 90 of Patent Document 2. As shown in FIG. As shown in the figure, the radio receiving apparatus 90 receives an antenna 91 with a desired signal S mixed with a noise signal N having no correlation as ambient noise. Radio receiving apparatus 90 delays the received signal in delay section 93 of noise removing section 92 and outputs the delayed signal to adaptive filter section 94. The wireless reception device 90 generates an error signal by subtracting the output signal from the adaptive filter unit 94 from the desired signal S mixed with the noise signal N in the error calculator 95 of the noise removal unit 92, and updates the filter coefficient. By outputting to the unit 96, the characteristics of the adaptive filter unit 94 are optimized. As a result, the wireless reception device 90 outputs an output signal approximated to the desired signal S from the adaptive filter unit 94.
[0005]
[Patent Document 1]
JP 2001-4736 A (FIG. 4)
[Patent Document 2]
JP-A-8-102644 (FIG. 11)
[0006]
[Problems to be solved by the invention]
By the way, in the wireless reception device 70 of Patent Document 1, an antenna 75 and a reference noise signal output unit 76 (a high frequency processing unit 77 and an A / D conversion unit 78) are required to receive the noise signal N, so that the circuit scale is large. Forced to increase. In addition, a device for preventing the desired signal S from being input to the antenna 75 side is required. This is because if the desired signal S is input to the antenna 75 side, the desired signal S is also generated as the noise cancellation signal AN in the adaptive filter unit 79, and the desired signal S may be removed. It is. Needless to say, in this wireless reception device 70, it is difficult to remove noise signals having no correlation.
[0007]
On the other hand, in the wireless reception device 90 of Patent Document 2, when there is a correlated noise signal, the noise signal is extracted together with the desired signal S and processed as an error signal to approximate the desired signal S. This adversely affects the output signal from the adaptive filter unit 94 to be performed. That is, it is difficult to remove correlated noise signals.
[0008]
An object of the present invention is to provide a digital receiver capable of suitably reducing ambient noise without increasing the circuit scale.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the invention according to claim 1 is characterized in that a first adaptive filter that reduces uncorrelated noise and ambient noise while sequentially updating filter coefficients in a standby state for receiving a desired signal. A second adaptive filter for reducing correlated noise having an adaptive mode to remove and a non-adaptive mode to stop updating the filter coefficients in the reception state of the desired signal; and the adaptation of the second adaptive filter The present invention includes a filter control means for switching and controlling the mode and the non-adaptive mode.
[0010]
According to a second aspect of the present invention, in the digital receiver according to the first aspect, the second adaptive filter is an adaptive filter in which the filter coefficient changes in accordance with a change in ambient noise in a standby state for receiving the desired signal. And a filter coefficient updating unit that sequentially updates the filter coefficients of the adaptive filter unit so as to reduce the ambient noise most.
[0011]
According to a third aspect of the present invention, in the digital reception device according to the first or second aspect, the digital signal receiving apparatus includes a detection unit that detects a new signal in a reception standby state of the desired signal, and the filter control unit includes the detection unit. The gist is to switch the second adaptive filter from the adaptive mode to the non-adaptive mode when the new signal is detected.
[0012]
According to a fourth aspect of the present invention, in the digital receiver according to the third aspect, the filter control means moves the second adaptive filter from the non-adaptive mode when the detected new signal is not the desired signal. The gist is to switch to the adaptive mode, and when the detected new signal is the desired signal, hold the second adaptive filter in the non-adaptive mode until the desired signal disappears.
[0014]
(Function)
According to the first or second aspect of the present invention, uncorrelated ambient noise is reduced by the first adaptive filter. Further, in the adaptive mode, correlated ambient noise is reduced by the second adaptive filter. In particular, in a standby state for receiving a desired signal, the second adaptive filter removes ambient noise while sequentially updating the filter coefficient corresponding to the adaptive mode. On the other hand, in the reception state of the desired signal, the second adaptive filter stops updating the filter coefficient corresponding to the non-adaptive mode. That is, in the non-adaptive mode, the second adaptive filter removes the ambient noise using the filter coefficient updated to remove the ambient noise in the adaptive mode. Therefore, in the reception state of the desired signal, even if the ambient noise and the desired signal have a correlation, only the ambient noise is removed by the adaptive filter, and the desired signal is suitably received. Even if the ambient noise and the desired signal are correlated, the filter control means can selectively receive these signals by switching between the adaptive mode and the non-adaptive mode. For example, the ambient noise and the desired signal can be received. The circuit scale is reduced as compared with the case where a circuit configuration that can be individually received is employed.
[0015]
According to a third aspect of the present invention, the second adaptive filter is switched from the adaptive mode to the non-adaptive mode by detecting a new signal by the detecting means. Therefore, without waiting for the judgment whether the new signal is due to a significant change in ambient noise or the desired signal, the filter control means immediately stops the update of the filter coefficient, so that the new signal becomes the desired signal. The desired signal is reflected on the filter coefficient as ambient noise until it is determined, and it is suppressed that the desired signal is removed after the determination.
[0016]
According to the fourth aspect of the present invention, when the detected new signal is not the desired signal, the second adaptive filter is switched from the non-adaptive mode to the adaptive mode, thereby removing the new signal as ambient noise. Accordingly, the update of the filter coefficient is resumed. On the other hand, when the detected new signal is the desired signal, the second adaptive filter is held in the non-adaptive mode until there is no desired signal, so that ambient noise is removed based on the last updated filter coefficient. And a desired signal is received suitably by removal of this ambient noise.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment embodying the present invention will be described with reference to FIG.
FIG. 1 is a system block diagram showing an FSK (Frequency Shift Keying) digital receiver 10. The FSK digital receiver 10 is for receiving a signal (hereinafter referred to as a desired signal) from a transmitter owned by a user, for example. Therefore, the operation modes of the FSK digital receiver 10 include a reception state for receiving a desired signal and a reception standby state for the desired signal. As shown in the figure, the FSK digital receiver 10 includes an antenna 11, a first frequency converter 12, an A / D converter 13, a second frequency converter 14, a band limiter 15, The first noise removing unit 16, the second noise removing unit 17, and the processing unit 18 are provided.
[0019]
The antenna 11 is basically configured to input a desired signal. In the reception state, ambient noise is input along with this, and in the reception standby state, ambient noise is input.
[0020]
The first frequency conversion unit 12 frequency-converts the input signal from the antenna 11 to generate an intermediate frequency signal, and outputs this to the A / D conversion unit 13. The A / D converter 13 performs A / D conversion on the signal from the first frequency converter 12 to generate a discretized digital signal. Then, the A / D converter 13 outputs this discretized digital signal to the second frequency converter 14.
[0021]
The second frequency conversion unit 14 frequency-converts the signal from the A / D conversion unit 13 to generate a baseband signal, and outputs this to the band limiting unit 15. The band limiting unit 15 performs band limitation on the signal from the second frequency converting unit 14 to generate a band limited signal, and outputs this to the first noise removing unit 16 as a received signal x1. This received signal x1 includes at least ambient noise as a noise signal.
[0022]
The first noise removing unit 16 is configured as an adaptive filter for reducing uncorrelated noise (for example, white noise) among ambient noise mixed in the reception signal x1 from the band limiting unit 15. The first noise removing unit 16 includes a first adaptive filter unit 16a in which the filter coefficient changes in accordance with a change in mixed correlated noise, and a filter coefficient of the first adaptive filter unit 16a so that the noise is reduced most. The first filter coefficient updating unit 16b for sequentially updating the. In the first noise removing unit 16, the received signal x1 from the band limiting unit 15 is output to the first adaptive filter unit 16a. The first noise removing unit 16 generates an error signal e1 in the error calculating unit 16c based on the received signal x1 from the band limiting unit 15 and the same signal via the first adaptive filter unit 16a, and this is generated by the first filter. By outputting to the coefficient updating unit 16b, the characteristics of the first adaptive filter unit 16a are optimized. As a result, the first noise removing unit 16 generates an extracted signal x2 from which uncorrelated noise has been removed from the ambient noise mixed in the received signal x1 from the band limiting unit 15, and the second noise removing unit 17 Output to. Therefore, the extracted signal x2 output to the second noise removing unit 17 is correlated noise (for example, fixed noise such as a stable interference wave).
[0023]
The second noise removing unit 17 is configured as an adaptive filter for removing the extracted signal x2 from the first noise removing unit 16 as correlated noise in the reception waiting state of the desired signal. The second noise removing unit 17 uses the second adaptive filter units 17a and 17b whose filter coefficients change with the change of the extraction signal x2, and the filter coefficients of the second adaptive filter units 17a and 17b so as to remove the signals. The second filter coefficient updating units 17c and 17d are sequentially updated. The second adaptive filter unit 17a and the second filter coefficient update unit 17c are for changing a part of the filter coefficient, and the second adaptive filter unit 17b and the second filter coefficient update unit 17d are the rest of the filter coefficient. It is for changing. The second adaptive filter unit 17a and the second filter coefficient update unit 17c and the second adaptive filter unit 17b and the second filter coefficient update unit 17d are connected in parallel, and a part and the rest of the filter coefficients are updated by parallel processing. By doing so, calculation efficiency is improved.
[0024]
When the extracted signal x2 from the first noise removing unit 16 is output to the second adaptive filter unit 17a and is output to the second adaptive filter unit 17b via the delay unit 17e, the second noise removing unit 17 Based on the signals through the second adaptive filter units 17a and 17b, the error calculation unit 17f generates an error signal e2. Then, the second noise removal unit 17 optimizes the characteristics of the second adaptive filter units 17a and 17b by outputting the error signal e2 to the second filter coefficient update units 17c and 17d (adaptive mode). Thereby, the second noise removal unit 17 removes the extracted signal x2 from the first noise removal unit 16 as correlated noise in the reception standby state of the desired signal, and outputs this to the processing unit 18. Therefore, the signal (error signal e2) output to the processing unit 18 is basically a zero level signal.
[0025]
Here, when a significant change in the error signal e2 is detected as a new signal in the processing unit 18, such as when ambient noise changes or when a desired signal is received, the second noise removing unit 17 causes the second filter to be output by the processing unit 18. The updating of the filter coefficients in the coefficient updating units 17c and 17d is stopped (non-adaptive mode). That is, the second adaptive filter units 17a and 17b of the second noise removing unit 17 hold the last filter coefficient immediately before the detection of the new signal. Therefore, in the reception state of the desired signal, the second noise removal unit 17 basically removes the correlated signal corresponding to the reception standby state as correlated noise, and removes the remaining signal after removing the stable interference wave. The extracted signal is output to the processing unit 18.
[0026]
The delay unit 17e is for synchronizing the filter processing in each of the second adaptive filter units 17a and 17b.
The processing unit 18 includes a signal processing unit 18a, a detection unit 18b, a filter control unit 18c, and a demodulation unit 18d. The signal processing unit 18a receives the signal (error signal e2) from the error calculation unit 17f of the second noise removal unit 17, calculates its autocorrelation, and outputs it as a correlation signal to the detection unit 18b and the demodulation unit 18d, respectively. .
[0027]
The detection unit 18b detects the presence of the desired signal based on the correlation signal from the signal processing unit 18a. Then, the detecting unit 18b outputs the detected presence of the desired signal to an external circuit (not shown). In particular, when the error signal e2 changes significantly, such as when a desired signal is received, the detection unit 18b detects this as a new signal and outputs a detection signal representing this to the filter control unit 18c at that time. At this time, the filter control unit 18c outputs the filter control signal to the second filter coefficient update units 17c and 17d, thereby stopping the update of the filter coefficient by them. On the other hand, if there is no input of the detection signal from the detection unit 18b, the filter control unit 18c allows the filter coefficient update by the second filter coefficient update units 17c and 17d.
[0028]
The demodulator 18d demodulates the desired signal based on the correlation signal from the signal processor 18a. The demodulator 18d outputs the demodulated signal to an external circuit (not shown).
[0029]
As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) In the present embodiment, in the reception standby state of the desired signal, the second noise removing unit 17 removes ambient noise (correlated noise) while sequentially updating the filter coefficient corresponding to the adaptive mode. . On the other hand, in the reception state of the desired signal, the second noise removal unit 17 stops updating the filter coefficient corresponding to the non-adaptive mode. That is, in the non-adaptive mode, the second noise removal unit 17 removes the ambient noise using the filter coefficient updated to remove the ambient noise (correlated noise) in the adaptive mode. Therefore, in the reception state of the desired signal, even if the ambient noise and the desired signal have a correlation, only the ambient noise is removed by the second noise removing unit 17 and the desired signal can be received suitably. Even if the ambient noise and the desired signal are correlated, the filter control unit 18c can selectively receive these signals by switching between the adaptive mode and the non-adaptive mode. For example, the ambient noise and the desired signal can be received. The circuit scale can be reduced as compared with the case where a circuit configuration capable of individually receiving the signal is adopted. For example, a noise signal receiving antenna and a reference noise signal output circuit as in Patent Document 1 can be omitted.
[0030]
(2) In the present embodiment, when the detection unit 18b detects a new signal, the second noise removal unit 17 is switched from the adaptive mode to the non-adaptive mode. Therefore, the filter control unit 18c promptly stops updating the filter coefficient without waiting for a determination as to whether the new signal is due to a significant change in ambient noise or a desired signal. Thereby, it is possible to prevent the desired signal from being reflected as the ambient noise in the filter coefficient until the new signal is confirmed as the desired signal and being removed after the determination. In other words, the generation of the desired signal as a noise cancellation signal before the new signal is determined as the desired signal is suppressed, and it is possible to prevent the reception sensitivity of the desired signal from deteriorating.
[0031]
(3) In the present embodiment, when the detected new signal is not the desired signal, the second noise removing unit 17 is switched from the non-adaptive mode to the adaptive mode, thereby filtering the new signal as ambient noise. The coefficient update is resumed. On the other hand, when the detected new signal is the desired signal, the second noise removing unit 17 is held in the non-adaptive mode until the desired signal disappears, whereby ambient noise is removed based on the last updated filter coefficient. The And a desired signal can be received suitably by removal of this ambient noise.
[0032]
(4) In the present embodiment, noise having no correlation can be removed by the first noise removing unit 16. Further, in the adaptive mode, correlated noise can be removed by the second noise removing unit 17.
[0033]
(5) For example, in an analog receiver, when an interference wave exists within a band, the desired wave needs to be larger than the interference wave. That is, when the interference wave (noise) in the band is larger than the desired wave (FSK signal), the FSK signal cannot be demodulated. In this embodiment, since the digital receiver is employed, the FSK signal can be demodulated even in an environment where noise larger than that of the FSK signal exists.
[0034]
In addition, embodiment of this invention is not limited to the said embodiment, You may change as follows.
In the above-described embodiment, the FSK digital receiver is adopted as the digital receiver, but other digital receivers such as ASK (amplitude modulation) and PSK (phase modulation) may be adopted.
[0035]
Although not particularly mentioned in the above embodiment, the digital receiver according to the present invention can be used as an on-vehicle digital receiver. As such a vehicle-mounted digital receiver, for example, there is a device that constitutes a so-called electronic lock that authenticates locking / unlocking of a vehicle door and start / stop of an engine by wireless communication with a transmitter owned by a user. Alternatively, the present invention may be applied to a system in which a user's remote control operation is received by wireless communication to drive and control various electric devices such as a power window device, a sliding door device, a sunroof device, and a seat device for the physically handicapped. In short, any system can be used as long as it can have a non-communication state (reception standby state) of a required signal.
[0036]
【The invention's effect】
As described above in detail, according to the first to fourth aspects of the present invention, ambient noise can be suitably reduced without increasing the circuit scale.
[Brief description of the drawings]
FIG. 1 is a system block diagram showing an embodiment of the present invention.
FIG. 2 is a block diagram showing a conventional example.
FIG. 3 is a block diagram showing another conventional example.
[Explanation of symbols]
16 1st noise removal part 17 as a 1st adaptive filter which comprises an adaptive filter 2nd noise removal part 17a, 17b as a 2nd adaptive filter which comprises an adaptive filter 2nd adaptive filter part 17c, 17d as an adaptive filter part Second filter coefficient update unit 18b as filter coefficient update unit Detection unit 18c as detection unit Filter control unit as filter control unit

Claims (4)

A first adaptive filter that reduces uncorrelated noise;
There is a correlation having an adaptive mode in which ambient noise is removed while sequentially updating filter coefficients in a reception waiting state of a desired signal, and a non-adaptive mode in which updating of the filter coefficient is stopped in the reception state of the desired signal A second adaptive filter for reducing noise ;
A digital receiving apparatus comprising: filter control means for switching and controlling the adaptive mode and the non-adaptive mode of the second adaptive filter. The digital receiver according to claim 1, wherein
The second adaptive filter includes an adaptive filter unit in which the filter coefficient changes in accordance with a change in ambient noise in a standby state for receiving the desired signal, and the filter coefficient of the adaptive filter unit so as to reduce the ambient noise most. And a filter coefficient updating unit that sequentially updates the digital receiver. The digital receiver according to claim 1 or 2,
In the standby state for receiving the desired signal, the detection means for detecting a new signal,
The digital control apparatus according to claim 1, wherein the filter control unit switches the second adaptive filter from the adaptive mode to the non-adaptive mode when the detection unit detects the new signal. The digital receiver according to claim 3, wherein
The filter control means includes
When the detected new signal is not the desired signal, the second adaptive filter is switched from the non-adaptive mode to the adaptive mode;
When the detected new signal is the desired signal, the second adaptive filter is held in the non-adaptive mode until the desired signal disappears .

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