WO2011065142A1

WO2011065142A1 - Reception device and gain control method

Info

Publication number: WO2011065142A1
Application number: PCT/JP2010/068056
Authority: WO
Inventors: 直樹大島
Original assignee: 日本電気株式会社
Priority date: 2009-11-30
Filing date: 2010-10-14
Publication date: 2011-06-03
Also published as: JPWO2011065142A1; JP5360227B2

Abstract

First, noise index information is stored in a memory, said noise index information indicating the relationship between numbers of amplitude points and S/N ratios of received signals exceeding prescribed thresholds that are preset by received signal type. Then, amplitude points of a received signal having an amplitude that exceeds the threshold are counted over a prescribed time period, and the resulting count is used along with the noise index information to obtain a noise proportion roughly equal to the S/N ratio of the received signal. The gain of a variable-gain amplifier is then set on the basis of said noise proportion.

Description

Receiver and gain control method

The present invention relates to a receiving device including an A / D converter and a gain control method applicable to the receiving device.

In order to demodulate a received signal that is a radio signal and extract information contained in the received signal, a mixer that converts a radio signal (high-frequency signal) into a B-band signal (analog signal) and a baseband signal output from the mixer An A / D (Analog to Digital) converter that converts a digital signal into a digital signal and a demodulator that demodulates a baseband signal converted into a digital signal and extracts information transmitted as a radio signal are required. Usually, the amplitude range of a signal that can be converted by the A / D converter is set at the time of designing the A / D converter and cannot be changed. Therefore, in a general receiving device, a variable gain amplifier is provided in front of the A / D converter, and the gain is adjusted so that the maximum amplitude of the baseband signal matches the maximum allowable input of the A / D converter. The resolution of the A / D converter is used efficiently.

However, when the received signal has a signal with the maximum amplitude only occasionally appearing like the OFDM signal and the average value of the signal amplitude is smaller than the maximum value, the maximum amplitude of the input signal of the A / D converter is the A / D converter. If the gain of the variable gain amplifier is adjusted to be equal to the maximum allowable input of the D converter, only a part of the resolution of the A / D converter is used for conversion of most input signals having a small signal amplitude. As a result, the demodulation accuracy of the received signal is reduced.

FIG. 1 is a waveform diagram showing a waveform example of an OFDM signal. In FIG. 1, the maximum amplitude value of the OFDM signal is indicated by Vmax.

As can be seen from FIG. 1, the maximum amplitude Vmax hardly appears in the OFDM signal, and the amplitude of many signals is Ve or less. Therefore, when an OFDM signal as shown in FIG. 1 is converted into a digital signal by an A / D converter whose Vmax matches the maximum allowable input, the resolution for converting the signals Ve to Vmax is almost wasted.

As a technique for solving the above problems, for example, in Patent Document 1 and Patent Document 2, the maximum amplitude Vmax of the input signal to the A / D converter is set larger than the maximum allowable input of the A / D converter. Thus, a method for substantially improving the signal resolution by the A / D converter has been proposed.

Patent Document 1 describes that the maximum amplitude ratio r of an input signal with respect to the maximum allowable input of the A / D converter is controlled according to the resolution (number of bits) of the A / D converter, and r is 1 or more, That is, it describes that the maximum amplitude of the input signal to the A / D converter is set to a value larger than the maximum allowable input of the A / D converter. Patent Document 2 describes a technique for determining the gain of a variable gain amplifier according to the magnitude of noise included in a received signal.

In addition, although it does not improve the signal resolution by the A / D converter, Patent Document 3 discloses that the S / N of the signal output from the variable gain amplifier in order to suppress the deterioration of the BER characteristic during the strong electric field fading. A technique for determining the gain of a variable gain amplifier according to the (signal to noise) ratio is described.

Patent Document 1 described above limits the received signal to an OFDM signal, and does not show any processing for other types of signals whose signal amplitude greatly changes, such as a QAM (Quadrature Amplitude Modulation) signal. When the maximum amplitude of the input signal to the A / D converter is set larger than the maximum allowable input of the A / D converter, generally, the gain of the variable gain amplifier should not be determined only by the resolution of the A / D converter. In addition, it should be determined in consideration of the magnitude of noise included in the received signal. Patent Document 1 shows that when the received signal is limited to an OFDM signal, the gain of the variable gain amplifier can be determined using the resolution of the A / D converter, and noise included in the received signal is taken into consideration. Thus, nothing is shown about the method of setting the gain of the variable gain amplifier.

On the other hand, Patent Documents 2 and 3 describe techniques for determining the gain of the variable gain amplifier in consideration of the magnitude of noise included in the received signal as described above. However, the receiving device described in Patent Document 2 is configured to obtain noise included in the received signal by performing Fourier transform on the received signal converted into a digital signal and analyzing the frequency spectrum, and is therefore necessary for noise detection. There is a problem that the circuit scale and processing load are large.

Patent Document 3 shows that the S / N ratio of a received signal is obtained from a BER (bit error rate), but the BER transmits a known data sequence determined in advance from a transmission device, for example, and receives the signal. It is necessary to calculate by comparing the data sequence demodulated by the apparatus with a known data sequence. Therefore, the transmission device and the reception device must cooperate with each other, and it is difficult to obtain the S / N ratio in real time during communication. Therefore, a technique for obtaining the noise of the received signal more simply and in real time is desired.

Japanese Patent Laid-Open No. 07-226725 (FIG. 13) Japanese Patent Laid-Open No. 2002-353813 (FIG. 14) Japanese Patent Laid-Open No. 10-303665 (FIG. 15)

Therefore, an object of the present invention is to provide a receiving apparatus and a gain control method for the same that can easily and in real time obtain noise included in a received signal, which is used for determining the gain of a variable gain amplifier.

In order to achieve the above object, a receiving apparatus of the present invention includes a variable gain amplifier whose gain can be changed in accordance with an external control signal;
An A / D converter that converts a received signal composed of an analog signal output from the variable gain amplifier into a digital signal;
A detector that counts the number of amplitude points at which the amplitude of the received signal exceeds a predetermined threshold in a predetermined period;
Noise index information indicating the relationship between the number of amplitude points of the received signal exceeding the threshold and the S / N ratio of the received signal, which is obtained in advance corresponding to the type of the received signal, A control unit for obtaining a noise ratio substantially equal to an S / N ratio of the received signal based on a count value output from the detection unit using index information, and setting a gain of the variable gain amplifier from the noise ratio;
A demodulator that demodulates the received signal converted into a digital signal by the A / D converter;
Have

On the other hand, the gain control method of the present invention includes a variable gain amplifier whose gain can be changed in accordance with an external control signal,
An A / D converter that converts a received signal composed of an analog signal output from the variable gain amplifier into a digital signal;
A demodulator that demodulates the received signal converted into a digital signal by the A / D converter;
A gain control method for controlling the gain of the variable gain amplifier in a receiver comprising:
Information processing device
Noise index information indicating the relationship between the number of amplitude points of the received signal exceeding a predetermined threshold and the S / N ratio of the received signal, which is obtained in advance corresponding to the type of the received signal, is stored in the memory. Aside,
The number of amplitude points where the amplitude of the received signal exceeds a predetermined threshold is counted in a predetermined period,
Based on the count value that is the result of the counting, using the noise index information, a noise ratio that is substantially equal to the S / N ratio of the received signal is obtained, and the gain of the variable gain amplifier is set from the noise ratio. is there.

FIG. 1 is a waveform diagram showing a waveform example of an OFDM signal. FIG. 2 is a graph showing the relationship between the number of amplitude points where the amplitude of the received signal exceeds a predetermined threshold and the S / N ratio of the received signal. FIG. 3 is a block diagram illustrating a configuration example of the receiving apparatus according to the first embodiment. FIG. 4 is a graph showing the relationship of the error rate to the S / N ratio of the received signal in the background art receiver. FIG. 5 is a graph showing the relationship of the error rate to the S / N ratio of the received signal in the receiving apparatus according to the first embodiment. FIG. 6 is a flowchart illustrating a processing procedure of the receiving apparatus according to the first embodiment. FIG. 7 is a waveform diagram showing how the signal amplitude changes when the gain of the variable gain amplifier is changed during signal reception. FIG. 8 is a block diagram illustrating a configuration example of the communication apparatus according to the second embodiment. FIG. 9 is a circuit diagram showing an embodiment of the detection unit shown in FIG. FIG. 10 is a block diagram illustrating a configuration example of the communication apparatus according to the third embodiment. FIG. 11 is a block diagram illustrating a configuration example of the receiving apparatus according to the fourth embodiment. FIG. 12 is a circuit diagram illustrating a configuration example of the detection unit illustrated in FIG. 11.

Next, the present invention will be described with reference to the drawings.
(First embodiment)
In the receiving apparatus of the present embodiment, the maximum amplitude of the input signal to the A / D converter is set larger than the maximum allowable input of the A / D converter, and the A / D converter The gain of the variable gain amplifier provided in the preceding stage of the D converter is set. Hereinafter, setting the maximum amplitude of the input signal to the A / D converter to be larger than the maximum allowable input of the A / D converter is referred to as “over-amplification”.

In this embodiment, the noise used for determining the gain of the variable gain amplifier is obtained according to the following principle.

FIG. 2 is a graph showing the relationship between the number of amplitude points (count value) at which the amplitude of the received signal exceeds a predetermined threshold and the S / N ratio of the received signal.

As shown in FIG. 2, the inventor of the present application has found that there is a certain relationship between the number of amplitude points of a received signal exceeding a predetermined threshold and the S / N ratio of the received signal. Therefore, in the receiving apparatus of this embodiment, the relationship between the number of amplitude points and the S / N ratio is obtained in advance by simulation or the like and stored in a memory or the like, and the S of the received signal is determined from the measured value of the number of amplitude points. / N ratio is obtained, and the gain of the variable gain amplifier is determined according to the S / N ratio. However, when the S / N ratio of the received signal is obtained from the measured value (count value) using the relationship shown in FIG. 2, the measured value includes conditions and errors that are not assumed in the simulation. It is difficult to say that the obtained value shows an accurate S / N ratio. Therefore, hereinafter, a value obtained from the measured value (count value) is referred to as “noise ratio” and is distinguished from “S / N ratio”. However, this noise ratio is substantially equal to the S / N ratio of the received signal, and even if the gain of the variable gain amplifier is determined based on the noise ratio, the BER or the like does not deteriorate greatly. In the receiving apparatus of this embodiment, the gain of the variable gain amplifier is determined using this noise ratio (≈S / N ratio).

FIG. 2 shows the result of simulating the relationship between the number of amplitude points (count value) exceeding a predetermined threshold and the S / N ratio when the received signal is an OFDM signal. When the received signal is another type of signal (for example, a QAM signal), a similar relationship may be obtained and stored for each type of the received signal by simulation or the like. Information stored in the receiving apparatus, which indicates the relationship between the number of amplitude points exceeding the predetermined threshold and the S / N ratio, is hereinafter referred to as “noise index information”.

FIG. 3 is a block diagram illustrating a configuration example of the receiving apparatus according to the first embodiment.

As shown in FIG. 3, the receiving apparatus of the first embodiment includes a variable gain amplifier 201, a gain adjusting unit 202, a peak detecting unit 203, a control unit 204, an A / D converter 205, a detecting unit 206, and a demodulating unit. 207.

The variable gain amplifier 201 amplifies a reception signal (baseband signal) that is an analog signal output from a mixer (not shown) with a gain set by the gain adjustment unit 203.

The A / D converter 205 converts the reception signal amplified by the variable gain amplifier 201 into a digital signal. The resolution of the A / D converter 205 may be fixed or variable, but in the present embodiment, the A / D converter 205 having a variable resolution is used. For example, P. Nicolas, V. Isabelle, H. Yann, “A Pixel Columun Level, Ultra Low Power, 9M Sample / s Multi bit A / D Converter for Monolithic Active Pixel Sensors in High Energy physics ", MIXDES 2009, 16 th International Conference" Mixed design of Integrated Circuit and Systems ", pp. 597-602, June 25-27, may be implemented utilizing the techniques described in 2009..

The peak detector 203 detects the maximum amplitude value of the received signal amplified by the variable gain amplifier 201.

The detection unit 206 compares the received signal converted into a digital signal by the A / D converter 205 with a predetermined threshold value, counts the amplitude points of the received signal exceeding the threshold value, and outputs the count value ( Measurement value) is output to the control unit 204.

The control unit 204 includes the noise index information, and uses the noise index information to obtain the noise ratio from the count value output from the detection unit 206, and determines the gain of the variable gain amplifier 201 based on the noise ratio. Then, a control signal for causing the gain adjusting unit 203 to set the gain of the variable gain amplifier 201 is output.

The gain adjusting unit 203 sets the gain of the variable gain amplifier 202 according to the maximum amplitude value of the received signal detected by the peak detecting unit 204 or the control signal received from the control unit 204.

In the receiving apparatus of the present embodiment, for example, the noise ratio is detected every predetermined period, and the gain of the variable gain amplifier 201 is determined by the control unit 204 based on the noise ratio. Therefore, immediately after starting to receive a radio signal from an arbitrary communication apparatus, the control unit 204 cannot determine the gain of the variable gain amplifier 201 based on the noise ratio because the noise ratio of the received signal cannot be detected. Therefore, the control unit 204 matches the maximum amplitude value detected by the peak detection unit 203 with the maximum allowable input of the A / D converter 205 in the first period immediately after the start of reception of a radio signal from another communication device. Thus, the gain adjustment unit 203 is caused to set the gain of the variable gain amplifier 201.

The demodulator 207 demodulates the reception signal converted into a digital signal by the A / D converter 205, and extracts reception information such as user data included in the reception signal.

The control unit 204, the detection unit 206, and the demodulation unit 207 of the present embodiment include, for example, a CPU, a DSP, a memory, an A / D converter, a D / A converter, and various logic circuits that execute predetermined signal processing according to a program. It can be realized by an information processing apparatus including the above. The variable gain amplifier 201, the gain adjustment unit 202, and the peak detection unit 203 of the present embodiment may be realized by a known analog circuit.

Note that the receiving apparatus generally includes a low-pass filter or the like for removing aliasing before the A / D converter 205. However, the element for removing aliasing has no relation to the feature of the present invention, and is omitted here.

FIG. 4 shows the relationship of the error rate (BER) to the S / N ratio of the received signal when the maximum amplitude value of the received signal is matched with the maximum allowable input of the A / D converter 205, that is, in the background art receiving apparatus. Show. FIG. 5 shows the relationship of the error rate (BER) with respect to the S / N ratio of the received signal in the received signal of the first embodiment. 4 and 5 respectively show the BER when the resolution of the A / D converter is changed to 2, 3, 4, and 8 bits.

As can be seen from a comparison of FIGS. 4 and 5, the BER reduction effect in the receiving apparatus employing the method shown in this embodiment is greatest when the resolution of the A / D converter is 2 bits. That is, the method shown in this embodiment is suitable when a low-resolution A / D converter is used. However, even if the resolution of the A / D converter is high, the BER can be improved by applying the method shown in this embodiment.

Therefore, in the receiving apparatus of this embodiment, the resolution of the A / D converter 205 is lowered when the noise ratio of the received signal is small. In general, a low-resolution A / D converter requires less power. Therefore, if the resolution of the A / D converter 205 is lowered when the noise ratio of the received signal is small, the power consumption of the entire receiving apparatus including the A / D converter 205 can be reduced.

FIG. 6 is a flowchart illustrating a processing procedure of the receiving apparatus according to the first embodiment. 6 shows only the processing procedure of the control unit 205 shown in FIG.

As shown in FIG. 6, when reception of a radio signal is started from an arbitrary communication device, the control unit 204 first determines the maximum amplitude value of the received signal detected by the peak detection unit 203 and the maximum allowable value of the A / D converter 205. The gain adjustment unit 202 is caused to set the gain of the variable gain amplifier 201 so as to match the input (step S1). At this time, even if the resolution of the A / D converter 205 is variable, the control unit 204 causes the A / D converter 205 to perform A / D conversion with the maximum resolution (maximum bit).

The variable gain amplifier 201 whose gain has been set by the gain adjusting unit 202 amplifies the input received signal (baseband signal) with the gain and outputs it to the A / D converter 205. The A / D converter 205 converts the received signal, which is an analog signal, into a digital signal and outputs the digital signal to the demodulation unit 207 and the detection unit 206. The detection unit 206 counts the number of amplitude points of the received signal exceeding a predetermined threshold for each preset period, and outputs the count value to the control unit 204.

The control unit 204 outputs from the detection unit 206 using the noise index information indicating the relationship (see FIG. 2) between the S / N ratio and the number of received signal amplitude points (count value) exceeding a predetermined threshold. Based on the counted value, the noise ratio of the received signal is obtained (step S2).

Next, the control unit 204 compares the obtained noise ratio with a preset noise reference value, and determines whether or not the noise ratio is larger than the noise reference value (step S3). When the obtained noise ratio is larger than the noise reference value, the control unit 204 determines only the gain of the variable gain amplifier 201 and sets the gain of the variable gain amplifier 201 via the gain adjustment unit 202 (step S4). If the obtained noise ratio is equal to or less than the noise reference value, the control unit 204 reduces the resolution of the A / D converter 205, determines the gain of the variable gain amplifier 201 based on the noise ratio, and adjusts the gain. The gain of the variable gain amplifier 201 is set via the unit 202 (step S5). The noise reference value is a value used to determine whether the noise ratio of the received signal is at a sufficiently low level that does not cause a problem even if the resolution of the A / D converter 205 is lowered.

As a method of determining the gain of the variable gain amplifier 201 based on the noise ratio, the following can be considered.

The control unit 204 of this embodiment basically includes a variable gain amplifier as the maximum amplitude of the input signal of the A / D converter 205 is larger than the maximum allowable input of the A / D converter 205 and the noise ratio is larger. The gain of the variable gain amplifier 201 is set so that the gain of 201 becomes large.

However, the gain of the variable gain amplifier 201 is shown in FIG. 1 by the demodulation accuracy that is improved when the resolution of the A / D converter 205 in the signal of 0 to Ve shown in FIG. The optimum value is obtained when the difference from the demodulation error that occurs when the signals Ve to Vmax are not A / D converted is the largest. Such a relationship can be obtained by simulation, for example.

Next, the control unit 204 changes the threshold value used for measuring the count value based on the changed resolution of the A / D converter 205 and the gain of the variable gain amplifier 201 (step S6), and step S2 Returning to the process, steps S2 to S6 are repeated.

Here, the following can be considered as a method for changing the threshold value.

As shown in FIG. 2, since the count value changes by changing the threshold value, the sensitivity for obtaining the noise ratio also changes when the threshold value is changed. First, the control unit 204 sets a threshold value used by the detection unit 206 to a small value so that the noise can be detected even if the noise included in the received signal is small. Thereafter, if the obtained noise ratio is large, the threshold value is increased to reduce the count value.

By the way, in the receiving apparatus of the present embodiment, the count value output from the detection unit 206 is acquired for every predetermined frame set in advance, for example, one frame defined by the OFDM method, and the noise ratio can be obtained by the control unit 204. That's fine. However, it is preferable to change the gain of the variable gain amplifier 201 even when one frame signal is being received, for example, when noise increases due to a change in the communication environment.

FIG. 7 shows how the signal amplitude changes when the gain of the variable gain amplifier 201 is changed during signal reception.

For example, when the gain of the variable gain amplifier 201 is changed during the reception of a signal of one frame, the gain of the entire receiving apparatus changes, so that the demodulator 207 cannot normally demodulate the received signal as it is. In such a case, the control unit 204 may notify the demodulating unit 207 of the changed gain and its setting timing.

In the demodulator 207 of this embodiment that demodulates the received signal converted into the digital signal, if it is possible to know the change in the gain of the entire receiver, it is easy to switch to the arithmetic processing according to the changed gain, The processing load is hardly changed. Excessive amplification processing cycles may be arbitrarily set in accordance with changes in the noise ratio, except for the first processing cycle at the start of communication.

According to the receiving apparatus of the present embodiment, the relationship between the number of amplitude points of the received signal exceeding the predetermined threshold and the S / N ratio is obtained in advance by simulation or the like and stored in a memory or the like. The noise ratio approximately equal to the S / N ratio of the received signal is obtained from the measured value of the number of the signals, and the gain of the variable gain amplifier 201 is set using the noise ratio. The noise included in the received signal that can be used for the determination can be obtained in real time. Also, by setting the gain of the variable gain amplifier 201 using the noise ratio, the 201 gain of the variable gain amplifier can be determined with a simple configuration without increasing the circuit scale and processing load.

Furthermore, in the receiving apparatus of this embodiment, as long as the above-described noise index information is provided for each type of received signal, not only the OFDM signal but also other types of received signals whose signal amplitude greatly changes are as described above. Similarly, the gain of the variable gain amplifier can be determined from the noise ratio.
(Second Embodiment)
FIG. 8 is a block diagram illustrating a configuration example of the communication apparatus according to the second embodiment.

As shown in FIG. 8, the communication apparatus according to the second embodiment has a configuration in which the detection unit 301 detects a noise ratio using a reception signal that is an analog signal output from the variable gain amplifier 201. Therefore, the detection unit 301 of the present embodiment is configured with an analog circuit. The resolution of the A / D converter 302 is variable as in the first embodiment.

Also, the control unit 302 of the second embodiment may be configured with an analog circuit because the detection unit 301 is an analog circuit. However, when the control unit 302 is realized by an information processing apparatus including a CPU, a DSP, a memory, and the like as in the first embodiment, A / D conversion for capturing the output signal of the detection unit 301 in the control unit 302 is performed. It is necessary to provide a vessel. Since other configurations and operations are the same as those in the first embodiment, the description thereof is omitted.

FIG. 9 is a circuit diagram showing an embodiment of the detection unit shown in FIG.

As shown in FIG. 9, the detection unit 301 includes an amplitude reference value generation unit 401, a first comparator 402, an integration circuit 403, a noise reference value generation unit 404, and a second comparator 405.

The amplitude reference value generation unit 401 generates a threshold voltage used for counting the amplitude points.

The first comparator 402 compares the threshold voltage generated by the amplitude reference value generation unit 401 with the output signal of the variable gain amplifier 201, and outputs an output signal of the variable gain amplifier 201 that is greater than the threshold voltage. Is output.

The integration circuit 403 integrates (smooths) the signal output from the first comparator 402 and outputs the result. This corresponds to the number (count value) of amplitude points at which the output value of the integrating circuit 403 is larger than the threshold voltage shown in the first embodiment. An output signal of the integration circuit 403 is output to the second comparator 405 and the control unit 302.

The noise reference value generation unit 404 generates a noise reference voltage for determining whether the noise ratio of the received signal is at a sufficiently low level that does not cause a problem even if the resolution of the A / D converter 302 is reduced. To do.

The second comparator 405 compares the integration voltage output from the integration circuit 403 with the noise reference voltage generated by the noise reference value generation unit 404, and outputs the comparison result to the control unit 302.

The control unit 302 obtains the noise ratio of the received signal using the integrated voltage output from the integrating circuit 403 instead of the count value shown in the first embodiment, and the variable gain amplifier 201 is based on the noise ratio. And a control signal indicating the determined gain is output to the gain adjusting unit 202. The control unit 302 reduces the resolution of the A / D converter 302 when the integrated voltage output from the integrating circuit 403 is smaller than the noise reference voltage.

According to the communication apparatus of the second embodiment, the same effect as that of the first embodiment can be obtained even if the detection unit 301 is configured by an analog circuit.
(Third embodiment)
FIG. 10 is a block diagram illustrating a configuration example of the communication apparatus according to the third embodiment.

The communication apparatus according to the third embodiment is an example using an A / D converter 501 with a fixed resolution. In this case, as shown in FIG. 10, the control unit 503 does not need to instruct the A / D converter 501 to change the resolution. Since other configurations and operations are the same as those in the first embodiment, the description thereof is omitted.

According to the communication apparatus of the present embodiment, the same effect as that of the communication apparatus of the first embodiment can be obtained, and the process of changing the resolution of the A / D converter 501 is unnecessary. The load is reduced.
(Fourth embodiment)
FIG. 11 is a block diagram illustrating a configuration example of the receiving apparatus according to the fourth embodiment.

In the receiving apparatus according to the fourth embodiment, similarly to the receiving apparatus according to the second embodiment, the detection unit 601 detects the noise ratio using the received signal that is an analog signal output from the variable gain amplifier 201. It is a configuration. The receiving apparatus according to the fourth embodiment uses an A / D converter 501 with a fixed resolution, as in the third embodiment. Therefore, as in the third embodiment, the control unit 603 does not need to instruct the A / D converter 501 to change the resolution.

FIG. 12 is a circuit diagram showing a configuration example of the detection unit shown in FIG.

As shown in FIG. 12, the detection unit 601 of the present embodiment has a configuration in which the noise reference value generation unit 404 and the second comparator 405 are excluded from the detection unit 301 of the second embodiment shown in FIG. is there. That is, in this embodiment, since the resolution of the A / D converter 602 is fixed, the detection unit 601 only needs to output the integrated voltage from the integration circuit 403 to the control unit 603.

According to the communication device of this embodiment, the same effect as that of the communication device of the first embodiment can be obtained, and the control unit 603 does not need to instruct the A / D converter 601 to change the resolution. The processing load on the control unit 603 is reduced. Furthermore, the detection unit 601 only needs to output the integrated voltage from the integration circuit 403 to the control unit 603, and the detection unit 601 can be configured more simply than in the second embodiment.

As mentioned above, although this invention was demonstrated with reference to embodiment, this invention is not limited to the said embodiment. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

This application claims priority based on Japanese Patent Application No. 2009-271491 filed on November 30, 2009, the entire disclosure of which is incorporated herein.

Claims

A variable gain amplifier whose gain can be changed in accordance with an external control signal;
An A / D converter that converts a received signal composed of an analog signal output from the variable gain amplifier into a digital signal;
A detector that counts the number of amplitude points at which the amplitude of the received signal exceeds a predetermined threshold in a predetermined period;
Noise index information indicating the relationship between the number of amplitude points of the received signal exceeding the threshold and the S / N ratio of the received signal, which is obtained in advance corresponding to the type of the received signal, A control unit for obtaining a noise ratio substantially equal to an S / N ratio of the received signal based on a count value output from the detection unit using index information, and setting a gain of the variable gain amplifier from the noise ratio;
A demodulator that demodulates the received signal converted into a digital signal by the A / D converter;
A receiving apparatus.
The controller is
The gain of the variable gain amplifier is such that the maximum amplitude of the input signal of the A / D converter is larger than the maximum allowable input of the A / D converter and the gain of the variable gain amplifier increases as the noise ratio increases. The receiving apparatus according to claim 1, wherein:
The A / D converter has a variable resolution,
The controller is
The receiving apparatus according to claim 1, wherein when the noise ratio is equal to or lower than a preset reference value, the resolution of the A / D converter is reduced.
A peak detector for detecting a maximum amplitude of the received signal;
The controller is
At the start of signal reception from another communication device, the gain of the variable gain amplifier is set so that the maximum amplitude of the received signal detected by the peak detector is equal to the maximum allowable input of the A / D converter 4. The receiving device according to claim 1, wherein a gain of the variable gain amplifier is set from the noise ratio after a predetermined period has elapsed from the start of signal reception.
The controller is
The receiving apparatus according to claim 1, wherein the demodulator is notified of the gain of the variable gain amplifier and the timing of setting the gain.
A variable gain amplifier whose gain can be changed in accordance with an external control signal;
An A / D converter for converting a received signal composed of an analog signal output from the variable gain amplifier into a digital signal;
A demodulator that demodulates the received signal converted into a digital signal by the A / D converter;
A gain control method for controlling the gain of the variable gain amplifier in a receiver comprising:
Information processing device
Noise index information indicating the relationship between the number of amplitude points of the received signal exceeding a predetermined threshold and the S / N ratio of the received signal, which is obtained in advance corresponding to the type of the received signal, is stored in the memory. Aside,
The number of amplitude points at which the amplitude of the received signal exceeds a predetermined threshold is counted in a predetermined period,
Based on the count value obtained as a result of the counting, using the noise index information, a noise ratio approximately equal to the S / N ratio of the received signal is obtained, and gain control for setting the gain of the variable gain amplifier from the noise ratio Method.
The information processing apparatus is
The gain of the variable gain amplifier is such that the maximum amplitude of the input signal of the A / D converter is larger than the maximum allowable input of the A / D converter and the gain of the variable gain amplifier increases as the noise ratio increases. The gain control method according to claim 6, wherein:
When the resolution of the A / D converter is variable,
The information processing apparatus is
The gain control method according to claim 6 or 7, wherein the resolution of the A / D converter is lowered when the noise ratio is equal to or less than a preset reference value.
The information processing apparatus is
At the start of signal reception from another communication device, the maximum amplitude of the received signal is detected, and the gain of the variable gain amplifier is set so that the maximum amplitude is equal to the maximum allowable input of the A / D converter. ,
The gain control method according to any one of claims 6 to 8, wherein a gain of the variable gain amplifier is set from the noise ratio after a predetermined period has elapsed from the start of signal reception.
The information processing apparatus is
The gain control method according to claim 6, wherein the demodulator is notified of the gain of the variable gain amplifier and the setting timing of the gain.