JP3005472B2 - Receiving machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver, and more particularly to a receiver for variably controlling a characteristic impedance according to a received electric field.

[0002]

2. Description of the Related Art Generally, in a radio communication device, an AGC circuit and an automatic equalizer are used so that a constant demodulation level is always obtained because a reception level of a receiver fluctuates due to a fluctuation of a radio wave propagation environment. .

One example of such a receiver is disclosed in
No. 2,283,908 discloses a “receiver having a step-type gain adjustment function”.

In this publication, a rectifying circuit for rectifying an intermediate frequency signal is described for a receiver performing burst reception,
A low-pass filter for smoothing the output of the rectifier circuit, a comparator for comparing the output voltage of the low-pass filter with a predetermined value and converting the output voltage to a digital signal indicating the magnitude of the signal amplitude, and a storage for holding the digital signal for one burst reception period Means and a variable attenuator for attenuating a high-frequency signal received in front of the front-end amplifier of the receiver in accordance with the data held in the storage means, and a technique having a step-type gain adjustment function of giving a comparator a hysteresis characteristic. ing.

FIG. 6 is a block diagram showing a conventional receiver.

Referring to FIG. 6, a conventional receiver comprises a variable attenuator 15 for attenuating a received signal 1, a high-frequency circuit 2 for amplifying a high-frequency signal, and a frequency converter 3 for converting a high-frequency signal to an intermediate frequency signal. , An IF filter 4 for filtering an intermediate frequency signal, a matching circuit 16 for performing impedance matching, and an IF filter 4 for amplifying the intermediate frequency signal.
It comprises an F amplifier 6, an electric field level detecting circuit 7 for detecting an electric field level, and a control circuit 9 for outputting a control voltage 10 based on electric field information 8 output from the detecting circuit.

Next, the operation will be described.

The received signal 1 is output to the high frequency circuit 2 via the variable attenuator 15. The received signal 1 amplified by the high frequency circuit 2 is converted into an IF signal of an intermediate frequency by a frequency converter 3 and output to an IF filter 4. IF filter 4
The IF signal band-limited by the above is amplified by the IF amplifier 6 via the matching circuit 16. The IF signal amplified by the IF amplifier 6 is output to the electric field level detection circuit 7, and outputs electric field information 8 corresponding to the received electric field level. Electric field information 8 is output to control circuit 9. The control circuit 9 outputs a control voltage 10 to the variable attenuator 15 to perform feedback control.

The control circuit 9 outputs a control voltage 10 in accordance with the electric field information 8, and when the level of the received signal 1 is high, the control voltage is variable so as to prevent the high frequency circuit 2, the frequency converter 3 and the IF amplifier 6 from being saturated. The amount of attenuation of the attenuator 15 is controlled.

[0010]

The above-described conventional receiver has a variable attenuator, and therefore has a high frequency amplifier or IF.
The disadvantages are that the gain of the amplifier must be set to a larger value than without the variable attenuator, and that an additional high-frequency or IF amplifier may be required to satisfy the total gain. Have.

In addition, when the variable attenuator is provided in a stage preceding the high-frequency circuit, there is a drawback that sensitivity is deteriorated at a low reception signal level.

On the other hand, when the variable attenuator is not used, there is a disadvantage that the high-frequency amplifier or the IF amplifier is saturated at the time of a high reception signal level and the reception sensitivity is deteriorated.

It is an object of the present invention to provide a receiver that does not use a variable attenuator and that prevents reception sensitivity from deteriorating even when the received signal level is high.

[0014]

A receiver according to the present invention converts a received signal into an intermediate frequency signal and includes an intermediate frequency filter for band-limiting the intermediate frequency signal and an intermediate frequency amplifier for amplifying the intermediate frequency signal. When the intermediate frequency amplifier is saturated and the input / output impedance fluctuates when the received signal level is high, the level of the received signal is detected, and the control signal corresponding thereto detects the level of the received signal. It is characterized in that the characteristic impedance of the matching circuit is varied to offset the fluctuation of the input / output impedance.

A high-frequency circuit for amplifying a received signal; a frequency converter for converting a high-frequency signal output from the high-frequency circuit into an intermediate-frequency signal; an intermediate-frequency filter for band-limiting the intermediate-frequency signal; A matching circuit that performs impedance matching of the intermediate frequency amplifier that amplifies the intermediate frequency signal, a detection circuit that detects the level of the amplified signal output by the intermediate frequency amplifier and outputs electric field information, and a control signal that corresponds to the electric field information. And a control circuit for outputting to the matching circuit.

A high-frequency circuit for amplifying a received signal, a frequency converter for converting a high-frequency signal output from the high-frequency circuit into an intermediate frequency signal, an intermediate frequency filter for band-limiting the intermediate frequency signal, A matching circuit that performs impedance matching of an intermediate frequency amplifier that amplifies the intermediate frequency signal, a demodulation circuit that demodulates an amplified signal output by the intermediate frequency amplifier and outputs demodulation information, and detects reception characteristic degradation from the demodulation information. A detection circuit that outputs a detection signal; and a control circuit that outputs a control signal corresponding to the detection signal to the matching circuit.

The matching circuit includes a plurality of capacitors connected in series, and a varicap diode connected between a connection point of these capacitors and a ground point.

The detection circuit includes a high-pass filter, a detection circuit for detecting a harmonic output from the filter, and a band-pass filter for outputting a demodulated wave.

[0019]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a receiver according to the present invention.

In this embodiment shown in FIG. 1, a high-frequency circuit 2 for amplifying a received signal 1 at a high frequency, a frequency converter 3 for converting the received signal having a high-frequency amplification to an intermediate frequency, and an IF signal of the converted intermediate frequency IF filter 4 for band limitation and matching circuit 5 for impedance matching
And an IF amplifier 6 for amplifying the matched IF signal
And an electric field level detecting circuit 7 for detecting a received electric field level from the IF signal amplified by the IF amplifier 6 and outputting electric field information 8, and outputting a control voltage 10 preset according to the electric field information 8 to the matching circuit 5. And a control circuit 9 for performing impedance control.

In FIG. 1, components corresponding to those shown in FIG. 6 are denoted by the same reference numerals or symbols, and description thereof will be omitted.

FIG. 2 is a detailed block diagram showing an example of the matching circuit of FIG.

The matching circuit 5 includes a plurality of capacitors connected in series and a varicap diode 17 for performing impedance matching of the capacitance components of the IF filter 4 and the IF amplifier 6.

Since the inter-terminal capacitance of the varicap diode 17 is controlled by the control voltage 10, the impedance of the matching circuit 5 can be varied.

FIG. 3 is a diagram for explaining the characteristics of the varicap diode.

Referring to FIG. 3, the varicap diode 17 has a characteristic that the terminal capacitance changes in response to the reverse voltage.

Next, the operation of the present embodiment will be described in more detail with reference to FIG. 1, FIG. 2 and FIG.

The control circuit 9 outputs a control voltage 10 for controlling the matching circuit 5, and controls the reception characteristics so as not to deteriorate. The reason for the deterioration of the reception characteristic is that when the reception signal 1 having a high input level is input, the IF amplifier 6 is saturated and the input impedance fluctuates, so that the pass characteristic of the IF filter 4 changes and the distortion component increases. It is.

In order to improve the reception characteristics, it is necessary to configure a matching circuit 5 that obtains an impedance that cancels the fluctuation of the input impedance when the IF amplifier 6 is saturated.

That is, the electric field information 8 is classified into a predetermined level range, a control voltage 10 corresponding to each electric field information 8 is obtained from an experimental result, and these data are stored in the control circuit 9 so that the electric field information 8 is stored. This is performed by controlling the matching circuit 5 by outputting the control voltage 10 corresponding to 8 stepwise.

That is, when the IF amplifier 6 is saturated and the input impedance fluctuates when the level of the received signal 1 is high, the control circuit 9 outputs the control voltage 10 and the characteristic impedance of the matching circuit 5 Control is performed so as to cancel the impedance fluctuation. As a result, I
The pass characteristic of the IF filter 4 deteriorated by the saturation of the F amplifier 6 can be improved, and the reception characteristic can be improved.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

Referring to FIG. 4, a high-frequency circuit 2 for amplifying the received signal 1 at a high frequency, a frequency converter 3 for converting the received signal subjected to the high-frequency amplification to an intermediate frequency, and limiting the band of the converted intermediate-frequency IF signal. An IF filter 4, a matching circuit 5 for performing impedance matching, an IF amplifier 6 for amplifying the matched IF signal, a demodulation circuit 11 for demodulating the IF signal amplified by the IF amplifier 6,
The detection circuit 13 includes a detection circuit 13 that detects the deterioration of reception characteristics from the demodulation information 12 of the demodulated received signal and outputs a detection result 14, and a control circuit 9 that outputs a control voltage 10 corresponding to the detection result 14 to the matching circuit 5. ing.

In FIG. 4, components corresponding to those shown in FIG. 1 are denoted by the same reference numerals or symbols, and description thereof is omitted.

The circuit shown in FIG. 4 is the same as the circuit shown in FIG. 1 in that a control voltage 10 is output to the matching circuit 5 to control the reception characteristics so as not to deteriorate, but the demodulation information 12 is used as a control method. It differs in using it.

In the case of a digital communication system, it is necessary to set an optimal demodulation timing when demodulating a received signal. Since information indicating the quality of reception characteristics has already been detected at the time of demodulation, this information is used. Can be output.

That is, the demodulation circuit 11 outputs demodulation information 12 indicating the quality of the reception characteristic, the detection circuit 13 detects whether the reception characteristic has deteriorated or improved, and outputs a detection result 14.

The control circuit 9 outputs a control voltage 10 such that the deterioration of the reception characteristics obtained from the detection result 14 is reduced. When the detection result 14 indicating that the reception characteristics have deteriorated is input, the control circuit 9 increases or decreases the control voltage 10.

The control circuit 9 determines that the control voltage 10 is increased as an initial value when, for example, the reception characteristics deteriorate. As a result, when the detection result 14 indicating that the reception characteristics have further deteriorated is obtained, the control voltage 10 is reduced. As a result, when the detection result 14 indicating that the reception characteristics have been improved is obtained, the control voltage 10 is further reduced. When the detection result 14 indicating that the reception characteristics have been degraded is obtained, the control voltage 10 is increased this time. .

As described above, by increasing or decreasing the control voltage 10, it is possible to perform feedback control of the matching circuit 5 so that the reception characteristics are optimized.

On the other hand, in the case of an analog communication system, it is possible to obtain information indicating whether the reception characteristic is good or not by detecting the harmonic component of the demodulated wave, and the same feedback control can be performed.

FIG. 5 is a detailed block diagram showing an example of an analog type detection circuit.

The demodulation information 12 output from the demodulation circuit 11 is band-limited by a band-pass filter 18 and output as a demodulated wave 19. At the same time, only the higher harmonics 22 are extracted from the demodulation information 12 by the high-pass filter 20, and the higher harmonics 22 are detected by the detection circuit 21 to obtain the detection result 14. Since the detection result 14 is obtained as a DC voltage corresponding to the level of the harmonic 22, a high DC voltage is obtained, for example, when there are many harmonics, that is, when the demodulation wave is distorted and the receiving characteristics are poor.

In the case of the circuits shown in FIGS. 4 and 5, in addition to being able to improve the deterioration of the reception characteristic due to the fluctuation of the input level of the received signal, the reception characteristic is deteriorated due to factors other than the fluctuation of the input level of the received signal. Control can be performed even in this case. As a cause other than the fluctuation of the input level of the received signal, the fluctuation of the impedance of the IF filter 4 and the IF amplifier 6 due to the temperature fluctuation and the aging can be considered.

In both FIGS. 1 and 4, the matching circuit 5 can be independently controlled by the control voltage 10 even if the matching circuit 5 is provided on the input side of the IF filter 4.

As described above, the receiver of the present invention can prevent the saturation of the amplifier by the feedback control of the control voltage at the time of the high reception level, and thus has the effect of preventing the deterioration of the reception sensitivity. are doing.

Further, since the variable attenuator can be eliminated, there is an effect that the reception characteristics do not deteriorate even when the reception signal level is low.

Further, since the matching characteristic can be controlled by the feedback control of the control voltage so that the receiving characteristic becomes the best, the fluctuation of the receiving sensitivity is always possible even with the fluctuation of the characteristic of the circuit element due to the temperature fluctuation and the aging. Has the effect of suppressing

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a receiver according to the present invention.

FIG. 2 is a detailed block diagram illustrating an example of a matching circuit of FIG. 1;

FIG. 3 is a diagram illustrating characteristics of a varicap diode.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a detailed block diagram illustrating an example of an analog detection circuit.

FIG. 6 is a block diagram showing a conventional receiver.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reception signal 2 high frequency circuit 3 frequency converter 4 IF filter 5 matching circuit 6 IF amplifier 7 electric field level detection circuit 8 electric field information 9 control circuit 10 control voltage 11 demodulation circuit 12 demodulation information 13 detection circuit 14 detection result 15 variable attenuator 16 Matching circuit 17 Varicap diode 18 Band-pass filter 19 Demodulated wave 20 High-pass filter 21 Detection circuit 22 Harmonic

Claims (5)

(57) [Claims] A matching circuit that converts a received signal into an intermediate frequency signal, and performs impedance matching between an intermediate frequency filter that limits the band of the intermediate frequency signal and an intermediate frequency amplifier that amplifies the intermediate frequency signal; When the intermediate frequency amplifier is saturated when the received signal level is high and the input / output impedance fluctuates, the level of the received signal is detected, and the characteristic impedance of the matching circuit is varied by a control signal corresponding to the received signal level. A receiver for canceling impedance fluctuations. 2. A high-frequency circuit for amplifying a received signal; a frequency converter for converting a high-frequency signal output from the high-frequency circuit into an intermediate frequency signal; an intermediate frequency filter for band-limiting the intermediate frequency signal; A filter and a matching circuit that performs impedance matching of the intermediate frequency amplifier that amplifies the intermediate frequency signal, a detection circuit that detects the level of an amplified signal output by the intermediate frequency amplifier and outputs electric field information, and that corresponds to the electric field information. A receiver for outputting a control signal to the matching circuit. 3. A high-frequency circuit for amplifying a received signal, a frequency converter for converting a high-frequency signal output by the high-frequency circuit into an intermediate frequency signal, an intermediate frequency filter for band-limiting the intermediate frequency signal, and an intermediate frequency filter. A filter and a matching circuit for impedance matching of the intermediate frequency amplifier for amplifying the intermediate frequency signal; a demodulation circuit for demodulating an amplified signal output from the intermediate frequency amplifier and outputting demodulation information; A receiver comprising: a detection circuit that detects and outputs a detection signal; and a control circuit that outputs a control signal corresponding to the detection signal to the matching circuit. 4. The matching circuit according to claim 2, wherein the matching circuit includes a plurality of capacitors connected in series, and a varicap diode connected between a connection point of these capacitors and a ground point. Item 3. The receiver according to Item 3. 5. The detection circuit, comprising: a high-pass filter;
A detection circuit for detecting harmonics output by the filter,
4. The receiver according to claim 3, further comprising a band filter that outputs a demodulated wave.