JP4148813B2 - Reception circuit and mobile radio receiver using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a receiving circuit for controlling a reception level by suppressing circuit saturation caused by an interference wave, and a mobile radio receiver using the receiving circuit.
[0002]
[Prior art]
In general, an automatic gain control (AGC) circuit keeps the signal amplitude at a desired value when the signal is reproduced by a receiver or the like. Therefore, when the input signal amplitude is small, the gain of the variable voltage amplifier is increased. When is large, the operation of lowering the gain of the variable voltage amplifier is automatically performed. However, when the interference wave is larger than the desired wave, the interior of the receiver is saturated. In such a case, an attempt has been made to satisfactorily receive a desired wave signal by providing a saturation detector in the receiver.
[0003]
As described above, the AGC circuit that performs the automatic gain control by connecting the saturation detector to the AGC circuit includes an analog control system that performs gain control using an analog circuit and a gain control that uses a digital circuit. It is known to perform digital control systems.
[0004]
FIG. 2 is a block diagram illustrating a configuration of a receiver having a receiving circuit that controls gain using an analog circuit. The first main part of the receiving circuit is composed of a first variable gain amplifying means 1, a frequency converting circuit 2, a filter 3, a second variable gain amplifying means 4, and a demodulating circuit 6. The second main part of the receiving circuit is composed of a saturation detection circuit 7 and an AGC circuit 8 (see, for example, Patent Document 1).
[0005]
The first variable gain amplifying means 1 has a function of amplifying or attenuating a signal received by an antenna (not shown), and its output is input to the frequency conversion circuit 2. This frequency conversion circuit 2 extracts the frequency of the desired wave signal and converts it to a predetermined frequency. The signal after the frequency conversion is given to the filter 3. The signal is band-limited by the filter 3. The signal band-limited by the filter 3 is amplified by the second variable gain limiting means and demodulated by the demodulation circuit 5.
[0006]
The signal output from the demodulation circuit 5 is output to a subsequent circuit (not shown) and also output to the AGC circuit 8. Further, the output from the frequency conversion circuit 2 is input to the saturation detection circuit 9 to detect whether or not the inside of the receiver is saturated, and the result is output to the AGC circuit 8. When the saturation detection circuit 9 detects that the interior of the receiver is saturated, the AGC circuit 7 attenuates the gain in order from the previous variable gain amplification means (first variable gain amplification means 1). On the other hand, when the saturation detection circuit 9 detects that the interior of the receiver is not saturated, the AGC circuit 8 increases the gain in order from the preceding variable gain amplification means (first variable gain amplification means 1). To do.
[0007]
However, in an analog AGC circuit, if the time constant of control is large, the capacitor and resistor that determine the time constant must be increased. When an analog front end unit including an AGC circuit is integrated into an IC in a receiver, elements for determining these time constants cannot be placed inside the IC. This causes problems such as an increase in external parts. In particular, when used in a mobile radio receiver, the number of parts increases, so that the receiver becomes larger and not practical. The saturation detector also requires a larger capacitor and resistor for determining the time constant in order to lower the frequency of the detection circuit output.
[0008]
Further, when a digital AGC circuit is used, the detection circuit must be digitized, and the input of the saturation detection circuit must be digitized. That is, a high-speed and wide dynamic range A / D converter is required, which is expensive.
[0009]
On the other hand, when the AGC circuit is applied to a digital broadcast receiver or a digital wireless communication receiver, the AGC circuit is preferably a digital circuit. In the digital AGC circuit, the time constant can be stored as a digital value, so that no capacitor or resistor is required, and the number of components can be reduced. In addition, if the processing after A / D conversion is performed by a DSP (Digital Signal Processor), it is possible to use the digital function as a signal by using the programming function to change the receiving environment, the moving speed, etc. Since the gain can be controlled flexibly, the function of the receiver can be enhanced.
[0010]
In order to control the gain using such a digital circuit, the level calculator detects the output level of the A / D converter, and the gain obtained from this and the reference level set in the arithmetic unit in advance. There is known a technique in which the gain of an amplifier is controlled using a control amount and a result of determining whether or not a circuit is saturated from an output of the amplifier before A / D conversion (for example, Patent Document 2). The automatic gain amplifying circuit described in this document uses a comparator as a saturation detector, and when it detects that the circuit is saturated, it selects a predetermined gain in the integrator and reduces the gain of the amplifier. Has been.
[0011]
However, in this prior art, for example, even when a strong interference wave is instantaneously received and the circuit is saturated, the predetermined gain is selected as described above. For this reason, even after the interference wave is no longer received, there is a problem that the gain cannot be flexibly controlled because it is affected by the selected gain.
[0012]
[Patent Document 1]
Japanese Utility Model Publication No. 3-46881 (summary, Fig. 1)
[Patent Document 2]
JP 2002-314356 A (Claim 2, paragraphs 0016 to 0024, FIG. 1)
[0013]
[Problems to be solved by the invention]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a receiving circuit in which an element for determining a time constant can be easily placed inside an IC.
Another object of the present invention is to provide a receiving circuit that can provide information to the AGC circuit whether or not the inside of the receiving circuit is saturated with a relatively simple configuration when a digital AGC circuit is used. It is in.
Still another object of the present invention is to provide a receiving circuit and a mobile radio receiver having an AGC circuit that can increase the gain of receiving a desired wave by reducing the influence of circuit saturation caused by an interference wave. .
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the receiving circuit of the present invention is configured to reflect the information from the comparator for determining whether or not the circuit is saturated in the control signal when the gain is controlled by the digital AGC circuit. That is, the present invention is as follows.
[0015]
  The receiving circuit of the present invention includes a first variable gain amplifying means for adjusting a level of a received signal, a frequency converting circuit for converting the frequency of an output signal from the first variable gain amplifying means, and the converted signal. , A second variable gain amplifying means for amplifying or attenuating the passing signal of the filter, and an A / D for converting the signal amplified or attenuated by the second variable gain amplifying means into a digital signal In a receiving circuit having a converter and a demodulating circuit for demodulating a signal output from the A / D converter, the voltage value of the output signal from the frequency converting circuit and the maximum level at which the filter is not saturated are set to the frequency. Comparing the value converted into the output voltage of the conversion circuit and outputting the comparison result as a predetermined signal, and the output signal based on the comparison result of the comparator From the output signal from the demodulation circuit, a first control signal for controlling the gain of the first variable gain amplifying means and a second control signal for controlling the gain of the second variable gain amplifying means are output. Automatic gain amplifierAnd comprising. The automatic gain amplifying circuit is connected to a control circuit, a first difference means for obtaining a difference between an output signal output from the demodulation circuit and a reference signal output from the control circuit, and the first difference means Connected to the first loop filter and the first loop filter for obtaining an envelope of the difference signal output from the first difference means 11 based on the filter coefficient output from the control circuit. A first integration circuit that integrates the differential signal output from the first loop filter, and a filter coefficient connected to the comparator and an envelope of the signal output from the comparator output from the control circuit And a second loop filter connected to the second loop filter to obtain the output from the second loop filter. A second integrating circuit that compares the two signals output from the first integrating circuit and the second integrating circuit, and selects a smaller value, and is connected to the comparing means, A first D / A converter that converts the selected smaller signal into an analog signal and outputs the signal as a first control signal; and further, the output signal output from the demodulation circuit and the control circuit A second difference means for obtaining a difference from the reference signal output from the second difference means, and an envelope of the difference signal output from the second difference means is output from the control circuit. A third loop filter that is obtained on the basis of the filter coefficient, a third integration circuit that is connected to the third loop filter and integrates a differential signal output from the third loop filter, and Third product A second D / A converter connected to a circuit for converting the signal output from the third integration circuit into an analog signal and outputting the analog signal as the second control signal, and the first D Based on the first control signal output from the A / A converter, the gain of the first variable gain amplifying means is controlled, and the second control output from the second D / A converter is performed. Based on the signal, the gain of the second variable gain amplifying means VGA is controlled.
[0016]
The comparator may compare a voltage of an output signal from the first variable gain amplifying unit with a predetermined voltage.
[0017]
According to this configuration, since the digital AGC circuit is used, the time constant can be stored as a digital value, a capacitor and a resistor are not required, and the number of parts can be reduced.
[0018]
In addition, since the comparator determines whether or not the receiving circuit is saturated, it is possible to provide the AGC circuit with information on whether or not the receiving circuit is saturated with a relatively simple configuration.
[0020]
The receiving circuit of the present invention can be used for a mobile radio receiver.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
Hereinafter, a receiving circuit according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a mobile radio receiver having a receiving circuit according to an embodiment of the present invention.
[0022]
In FIG. 1, 1 is a first variable gain amplification means, 2 is a frequency conversion circuit, 3 is a filter, 4 is a second variable gain amplification means, 5 is an A / D converter, 6 is a demodulation circuit, and 7 is a comparator. , 8 represent automatic gain amplification (AGC) circuits, respectively.
[0023]
In FIG. 1, a signal output from an antenna (not shown) is amplified or attenuated by the first variable gain amplifying means 1. The amplified or attenuated signal includes a signal having a frequency of several channels. The frequency conversion circuit 2 takes out the frequency of the desired wave signal from the signals of several channels and converts it to an intermediate frequency or a baseband frequency. The signal output from the frequency conversion circuit 2 includes a desired wave signal, an interference wave signal, and an image signal generated during frequency conversion. Therefore, the signal output from the frequency conversion circuit 2 is passed through the filter 3 and only the desired wave signal is extracted. The desired wave signal output from the filter 3 is amplified by the second variable gain amplifying means 4. The amplified desired wave signal is converted to a digital signal by the A / D converter 5, subjected to digital demodulation processing by the demodulation circuit 6, converted into a data series, and output from the output terminal. When the frequency conversion circuit 2 converts the frequency to an intermediate frequency, the demodulation circuit 6 converts the frequency to a baseband frequency. The demodulating circuit 6 performs error correction on the demodulated signal and calculates an error rate of the data. Further, the demodulating circuit 6 calculates the output intensity of the second variable gain amplifying means 4 and sets this as the intensity of the desired wave signal. In the present specification, the intensity takes a non-negative value of 0 or more. On the other hand, if the intensity is 0, it means that the desired wave signal has not been received.
[0024]
Part of the output signal from the frequency converter 2 is input to the comparator 7. The comparator 7 compares the voltage of this output signal with a predetermined voltage. Here, the predetermined voltage is an output voltage of the frequency converter 2 and is a voltage that may be saturated in any one of the first variable gain amplifying means 1, the frequency converter 2, and the filter 3. This voltage is determined by, for example, a circuit simulator to determine how much output voltage (output equivalent saturation voltage) each of the first variable gain amplifying means 1, the frequency converter 2 and the filter 3 starts, or It can be obtained by actually making each part as a prototype and actually measuring it. At the same time, each gain or attenuation is also obtained by a simulator or actual measurement. From the respective gains or attenuation amounts, the relationship of the output of the frequency converter 2 with respect to the output voltage of each part is obtained. Using this relationship, the output equivalent saturation voltage of each part is converted to the output voltage of the frequency converter 2, and the lowest voltage among the voltages of each part is set as a predetermined voltage. The comparator 7 outputs 0 to the AGC circuit 8 if the output voltage of the frequency converter 2 exceeds a predetermined voltage, and 1 otherwise to the AGC circuit 8.
[0025]
The AGC circuit 8 determines the gains of the first variable gain amplifying means 1 and the second variable gain amplifying means 4 from the intensity of the desired wave signal, the data error rate, and the output signal from the comparator.
[0026]
Next, an example of the automatic gain method according to the present invention will be described. FIG. 3 is a block diagram illustrating an example of an automatic gain circuit. In the example of this figure, the gain of the variable gain amplifying means is increased as the control signal is larger, and the gain of the variable gain amplifying means is lowered and attenuated as the control signal is smaller.
[0027]
  The first control signal is obtained as follows. The desired wave signal output from the demodulating circuit 6 takes the difference from the reference signal output from the control circuit 10 by the difference means 11 and outputs the difference signal to the loop filter 21. The loop filter 21 smoothes the difference signal based on the filter coefficient output from the control circuit 10.(Operation to obtain the envelope of the differential signal)And output to the integrating circuit 31. The smoothed difference signal is integrated by the integration circuit 31. On the other hand, the signal output from the comparator 7 is input to the loop filter 20, and the difference signal is smoothed based on the filter coefficient output from the control circuit 10 and integrated by the integration circuit 30. These two signals output from the integration circuits 30 and 31 are output to the comparison circuit 40, and the smaller value is selected as the first control signal. The first control signal is output to the D / A converter 51 and converted into an analog signal. Based on this signal strength, the gain of the first variable gain amplifying means 1 is controlled.
[0028]
The second control signal is obtained as follows. The desired wave signal output from the demodulating circuit 6 takes the difference from the reference signal output from the control circuit 10 by the difference circuit 12 and outputs the difference signal to the loop filter 12. The loop filter 12 smoothes the difference signal based on the filter coefficient output from the control circuit 10 and outputs the difference signal to the integration circuit 32. The smoothed difference signal is integrated by the integration circuit 32. The second control signal is output to the D / A converter 52 and converted into an analog signal. Based on this signal, the gain of the second variable gain amplifying means 4 is controlled.
[0029]
Each of the integration circuits 30, 31, and 32 is provided with a limiter function for determining an upper limit and a lower limit so that the integral value does not exceed a certain range. Further, when the integral value reaches the upper limiter or the lower limiter, the information is sent to the control circuit 10 and used to determine the first reference value and the second reference value.
[0030]
The control circuit 10 determines the optimum value of the desired wave signal intensity, which is considered to be optimum, obtained from the data error rate, the first and second reference values, the filter coefficients of the loop filters 20, 21, and 22.
[0031]
Next, the gain control method of the first variable gain amplifying means 1 and the second variable gain amplifying means 4 according to the receiving circuit of the present invention will be described. First, a gain control method when the inside of the receiver is not saturated will be described. In this case, since the comparator 7 outputs 1, a signal obtained from the difference between the reference value and the desired wave signal intensity is selected as the first control signal. Based on this signal, the gain of the first variable gain amplifying means 1 is controlled.
[0032]
The optimum value of the desired wave signal intensity is set as the reference value of the first variable gain amplifying means 1, 0 is set as the reference value of the second variable gain amplifying means 4, and the first and second control signals are output as the integration circuit outputs. The minimum value that can be taken is set as each initial value. By setting such an initial value, it is possible to avoid saturation of the inside of the receiver even when the desired wave signal intensity is high from the start of reception.
[0033]
That is, when the actual desired wave signal strength is larger than the reference value of the first variable gain amplifying means 1, the loop filter 21 outputs a signal that lowers the gain of the first variable gain amplifying means 1. . Since the input of the loop filter 22 is always a negative value, the loop filter 22 also outputs a signal that lowers the gain of the second variable gain amplifying means 4. However, the outputs of the integrating circuits are already set to the minimum values that can be taken by the first and second control signals, and the gains of the first variable gain amplifying means 1 and the second variable gain amplifying means are the lowest. Yes. For this reason, the inside of the receiver is stabilized in this state.
[0034]
When the actual desired wave signal intensity is smaller than the reference value of the first variable gain amplifying means 1, the control signal obtained from the difference between the reference value of the first variable gain amplifying means 1 and the desired wave signal intensity is used. The first control signal is increased so as to increase the gain of the first variable gain amplifying means 1. On the other hand, the input to the loop filter 22 is always a negative value, and the loop filter 22 outputs a signal that lowers the gain of the second variable gain amplifying means 4. However, since the integration circuit 32 is already set to the minimum value that can be taken by the second control signal, the gain of the second variable gain amplifying means 4 remains at the minimum.
[0035]
If the desired wave signal intensity matches the reference value of the first variable gain amplifying means 1 before the first control signal is applied to the upper limiter of the integrator 31, the difference is reduced. As a result, there is no need to change the gain of the first variable gain amplifying means 1, so that the first control signal is stabilized in this state.
[0036]
When the first control signal rises and reaches the upper limit limiter 31 of the integrator in a state where the circuit is not saturated, the desired wave signal is obtained even if the gain of the first variable gain amplifying means 1 is maximized. It means that the optimum value of strength has not been reached. In this case, the reference value of the first variable gain amplifying means 1 is set to the maximum value that the desired wave signal intensity can take, and the reference value of the second variable gain amplifying means 4 is set to the optimum value of the desired wave signal intensity. That is, the second control signal is increased so as to increase the gain of the second variable gain amplifying means 4 while keeping the gain of the first variable gain amplifying means 1 at the maximum.
[0037]
If the desired wave signal intensity matches the reference value of the second variable gain amplifying means 4 before the second control signal is applied to the upper limiter of the integrator 32, the difference becomes small. As a result, it is not necessary to change the gain, so that the second control signal is stabilized.
[0038]
When the second control signal rises and reaches the upper limiter of the integrator 32, the optimum value of the desired wave signal strength is not reached even if the gain of the second variable gain amplifying means 4 is maximized. Means. In this case, each of the first variable gain amplifying means 1 and the second variable gain amplifying means 4 has a maximum gain that can be set. That is, the received signal strength is very small.
[0039]
As the received signal strength increases from a state where the received signal strength is very small, the difference between the reference value of the second variable gain amplifying means 4 and the desired wave signal strength decreases. That is, the second control signal is reduced, and the gain of the second variable gain amplifying means 4 is lowered to approach the optimum value of the desired wave signal intensity.
[0040]
Further, when the desired wave signal intensity continues to be higher than the reference value of the second variable gain amplifying means 4 and reaches the lower limiter of the integrator 32, the gain of the second variable gain amplifying means 4 is minimized. Anyway, this means that the desired wave signal intensity is high. In this case, the reference value of the first variable gain amplifying means 1 is set to the optimum value of the desired wave signal intensity, the reference value of the second variable gain amplifying means 4 is set to 0, and the first variable gain amplifying means 1 Reduce gain.
[0041]
The reference values of the first and second variable gain amplifying means are the same as the reference values in the initial state. That is, when the inside of the circuit is not saturated, the AGC circuit according to the present invention operates so as to set the desired wave signal strength to an optimum value by performing the above-described operation with respect to fluctuations in the strength of the received signal. .
[0042]
Next, the operation when there is a possibility that the interference wave included in the received signal is large and the inside of the receiver may be saturated will be described.
[0043]
In this case, the point that the output from the comparator 7 is reflected when the gain of the first variable gain amplifying means 1 is controlled is different from the case where the interior of the receiver is not saturated. That is, when the instantaneous value of the output voltage from the frequency converter 2 exceeds the value saturated in the receiver, the comparator 7 outputs 0. Specifically, as described above, the instantaneous value of the output voltage from the frequency converter 2 may be saturated by any one of the first variable gain amplifying means 1, the frequency converter 2, and the filter 3. This is the case when a certain voltage is exceeded.
[0044]
The value obtained by smoothing this value by the loop filter 20 and integrating by the integration circuit 30 decreases linearly. When the value obtained from the output signal from the comparator 7 becomes smaller than the value obtained from the difference between the reference value and the desired wave signal intensity, the output signal from the comparator 7 is selected as the first control signal, The gain of one variable gain amplifying means 1 is reduced. As a result, the desired wave signal intensity decreases.
[0045]
In this state, the desired wave signal intensity is smaller than the first reference value and the second reference value. Therefore, the automatic gain amplifying circuit 8 increases the first control signal and the second control signal obtained from the difference between the reference value and the desired wave signal strength in order to increase the desired wave signal strength. However, since the first variable gain control means 1 is dominated by the control signal based on the comparator 7, the gain remains lowered. As a result, since the signal intensity of the interference wave input to the filter 3 remains lowered, the influence of the interference wave can be reduced.
[0046]
By reducing the gain of the first variable gain control means 1 and reducing the signal strength of the interference wave, the frequency with which the comparator 7 detects saturation inside the circuit is reduced. As a result, the frequency at which the comparator outputs 0 decreases, so that the gain of the first variable gain control means 1 is stabilized.
[0047]
On the other hand, the second variable gain amplifying means 4 sets the reference value as the optimum value of the desired wave signal strength in order to increase the gain. As a result, the second control signal is increased, and the desired wave signal intensity is increased. However, since the first variable gain amplifying means 1 is dominated by the signal based on the output from the comparator, the desired wave signal strength may not reach the optimum value.
[0048]
The comparator 7 outputs 1 when the receiving circuit does not saturate due to the elimination of the interference wave. The value smoothed by the loop filter 20 and integrated by the integration circuit 30 increases linearly. When the value obtained from the output signal from the comparator 7 becomes larger than the value obtained from the difference between the reference value and the desired wave signal intensity, the signal obtained from the difference between the reference value and the desired wave signal intensity is the first value. Is selected as the control signal.
[0049]
According to the configuration of the present invention, it is extremely effective when a strong interference wave in a very short time like a pulse is received. That is, it is a very short time for the comparator to detect the saturation inside the circuit and output 0. Accordingly, the comparator does not output 0 before the value obtained from the output signal from the comparator becomes smaller than the value obtained from the difference between the reference value and the desired wave signal intensity. As a result, the first variable gain amplifying means remains dominated by the control signal based on the value obtained from the difference between the reference value and the desired wave signal intensity. The influence on the control can be reduced. That is, if the gain of the first variable gain amplifying means remains reduced for a while due to the instantaneously input interference wave, the period during which the desired wave signal-to-noise ratio decreases becomes longer. For this reason, since the state where the error rate of the demodulated signal is high continues, the error correction function does not work sufficiently, and the reception quality deteriorates. On the other hand, according to the configuration of the present invention, there is a possibility that the demodulated signal data may be corrupted by the disturbing wave input instantaneously. However, in this case, since there is a high possibility that the error can be corrected by error correction, it is possible to prevent deterioration in reception quality.
[0050]
When receiving a desired wave with a high signal strength, if a very large interference wave is received continuously, the signal considered as the desired wave signal by the demodulation circuit may be a distortion component due to saturation. is there. In this case, the control circuit can change the filter coefficient of the loop filter in order to quickly reduce the gain of the first variable gain amplifying means from the data error rate and the value obtained from the output signal from the comparator.
[0051]
(Embodiment 2)
In the first embodiment, the output signal output from the frequency conversion circuit to the comparator is compared with a predetermined voltage. On the other hand, the present embodiment is different from the first embodiment in that the output signal output from the first variable gain amplifying means to the comparator is compared with a predetermined voltage. That is, if the frequency handled by the first variable gain amplifying means is not so high and the comparator can operate sufficiently, there is no problem even if the comparator input uses the output of the first variable gain amplifying means. The predetermined voltage used for the comparator is a value obtained by converting a voltage at which each part may be saturated into the output of the first variable gain amplifying means. The points other than these are the same as in the first embodiment.
[0052]
If the receiver circuit embodying this patent is used in a mobile radio receiver, a digital AGC circuit is used, so that the time constant can be stored as a digital value, no capacitors or resistors are required, and the number of parts can be reduced. This receiver can be miniaturized and portable. Moreover, even when the intensity of the disturbing wave becomes larger than the intensity of the desired wave during mobile reception, it can be received comfortably.
[0053]
【The invention's effect】
As described above, the present invention uses a digital AGC circuit and determines the circuit saturation by a comparator without using an analog saturation detection circuit. Therefore, an element for determining a time constant can be easily inserted in the IC. A receiving circuit capable of performing the above is obtained.
Further, according to the present invention, when a digital AGC circuit is used, it is possible to obtain a receiving circuit that can output information on whether the inside of the receiving circuit is saturated or not to the AGC circuit with a relatively simple configuration called a comparator.
Further, according to the present invention, when the circuit is saturated, the gain of the variable gain amplifying means can be controlled by the saturation signal from the comparator. A receiver circuit and a mobile radio receiver having an AGC circuit capable of increasing the frequency are obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a mobile radio receiver having a receiving circuit according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a receiver including a receiving circuit that performs gain control using an analog circuit;
FIG. 3 is a block diagram illustrating an example of an automatic gain circuit.
[Explanation of symbols]
1 First variable gain amplification means
2 Frequency conversion circuit
3 filters
4 Second variable gain amplifying means
5 A / D converter
6 Demodulator circuit
7 Comparator
8 Automatic gain amplification circuit
9 Saturation detection circuit
10 Control circuit
11, 12 Difference means
20, 21, 22 Loop filter
30, 31, 32 Integration circuit
40 Comparison circuit
51, 52 D / A converter

Claims (3)

First variable gain amplification means for adjusting the level of the received signal;
A frequency conversion circuit for converting the frequency of the output signal from the first variable gain amplification means;
A filter for band-limiting the converted signal;
Second variable gain amplifying means for amplifying or attenuating the passing signal of the filter;
An A / D converter for converting the signal amplified or attenuated by the second variable gain amplification means into a digital signal;
A receiving circuit having a demodulation circuit for demodulating a signal output from the A / D converter;
A comparator that compares the voltage value of the output signal from the frequency conversion circuit with a value obtained by converting the maximum level at which the filter is not saturated into the output voltage of the frequency conversion circuit, and outputs the comparison result as a predetermined signal; ,
The first control signal for controlling the gain of the first variable gain amplifying means and the gain of the second variable gain amplifying means are controlled from the output signal based on the comparison result of the comparator and the output signal from the demodulation circuit. An automatic gain amplification circuit that outputs a second control signal to be
The automatic gain amplification circuit includes:
A control circuit;
First difference means for taking a difference between an output signal output from the demodulation circuit and a reference signal output from the control circuit;
A first loop filter coupled to the first difference means for obtaining an envelope of the difference signal output from the first difference means 11 based on a filter coefficient output from the control circuit;
A first integration circuit connected to the first loop filter and integrating the differential signal output from the first loop filter;
A second loop filter connected to the comparator for obtaining an envelope of a signal output from the comparator based on a filter coefficient output from the control circuit;
A second integrating circuit connected to the second loop filter and integrating an output from the second loop filter;
Comparing means for comparing two signals output from the first integrating circuit and the second integrating circuit and selecting a smaller value;
A first D / A converter connected to the comparison means for converting the selected smaller signal into an analog signal and outputting it as a first control signal;
Second difference means for taking a difference between an output signal output from the demodulation circuit and a reference signal output from the control circuit;
A third loop filter coupled to the second difference means for obtaining an envelope of the difference signal output from the second difference means based on the filter coefficient output from the control circuit;
A third integrating circuit connected to the third loop filter and integrating the differential signal output from the third loop filter;
A second D / A converter connected to the third integration circuit, converting a signal output from the third integration circuit into an analog signal and outputting the analog signal as the second control signal;
Based on the first control signal output from the first D / A converter, the gain of the first variable gain amplifying means is controlled,
A receiving circuit for controlling the gain of the second variable gain amplifying means VGA based on the second control signal output from the second D / A converter. First variable gain amplification means for adjusting the level of the received signal;
A frequency conversion circuit for converting the frequency of the output signal from the first variable gain amplification means;
A filter for band-limiting the converted signal;
Second variable gain amplifying means for amplifying or attenuating the passing signal of the filter;
In a receiving circuit comprising: an A / D converter that converts a signal amplified or attenuated by the second variable gain amplifying means into a digital signal; and a demodulation circuit that demodulates the signal output from the A / D converter ,
The voltage value of the output signal from the first variable gain amplifying means is compared with the value obtained by converting the maximum level at which the filter does not saturate into the output voltage of the frequency conversion circuit, and the comparison result is used as a predetermined signal. A comparator to output,
Based on the output signal based on the comparison result of the comparator and the output signal from the demodulation circuit, the first control signal for controlling the gain of the first variable gain amplifying means and the gain of the second variable gain amplifying means are obtained. An automatic gain amplifying circuit that outputs a second control signal to be controlled, the automatic gain amplifying circuit comprising:
A control circuit;
First difference means for taking a difference between an output signal output from the demodulation circuit and a reference signal output from the control circuit;
A first loop filter coupled to the first difference means for obtaining an envelope of the difference signal output from the first difference means 11 based on a filter coefficient output from the control circuit;
A first integration circuit connected to the first loop filter and integrating the differential signal output from the first loop filter;
A second loop filter connected to the comparator for obtaining an envelope of a signal output from the comparator based on a filter coefficient output from the control circuit;
A second integrating circuit connected to the second loop filter and integrating an output from the second loop filter;
Comparing means for comparing two signals output from the first integrating circuit and the second integrating circuit and selecting a smaller value;
A first D / A converter connected to the comparison means for converting the selected smaller signal into an analog signal and outputting it as a first control signal;
Second difference means for taking a difference between an output signal output from the demodulation circuit and a reference signal output from the control circuit;
A third loop filter coupled to the second difference means for obtaining an envelope of the difference signal output from the second difference means based on the filter coefficient output from the control circuit;
A third integrating circuit connected to the third loop filter and integrating the differential signal output from the third loop filter;
A second D / A converter connected to the third integration circuit, converting a signal output from the third integration circuit into an analog signal and outputting the analog signal as the second control signal;
Based on the first control signal output from the first D / A converter, the gain of the first variable gain amplifying means is controlled,
A receiving circuit for controlling the gain of the second variable gain amplifying means VGA based on the second control signal output from the second D / A converter. A mobile radio receiver comprising the receiving circuit according to claim 1 .

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