JP2000228636A - Receiving level control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the error of a received signal level monitor due to a temperature characteristic by providing a controlling means which controls the attenuation quantity of a variable attenuation part so that inputted signal level difference can be equal to a set reference level and corrects a received signal level by using the change of the attenuation quantity at this time, etc. SOLUTION: A part of a distribution signal Pb amplified by a low noise high frequency amplifier circuit 3 is attenuated by a variable attenuator 16 to be a distribution signal Pb', a distribution signal Pa is made to be a distribution signal Pa' being a reverse phase to the signal Pb by a phase shifter 17 and both of them are synthesized by a power synthetic circuit 15. When the amplitudes of the two distribution signals do not coincide here, i.e., Pa'≠Pb', signal level difference is outputted, and this output is amplified by an amplifier 18 and detected by a detector 19. The detected signal is compared with a reference level by a comparator circuit 20 and the attenuation quantity of the attenuator 16 is controlled so as to be equal to the reference level. In such a case, a received signal level is corrected by using the change of the attenuation quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic gain control circuit for a radio receiver, which keeps a demodulator input level constant irrespective of a received signal level, and more particularly to a monitoring operation of a received signal level. Things.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing an automatic reception gain control circuit of a heterodyne radio apparatus.

[0003] In the figure, 3 is a low-noise high-frequency amplifier circuit,
5 is a mixer, 6 ₁ and 6 ₂ are first and second intermediate frequency amplifiers,
7 is a variable attenuator, 8 is a power distribution circuit, 9 is an envelope detection circuit, 10 is a comparison circuit, and 11 is a received signal monitoring circuit.

First, in order to perform the automatic reception gain control operation (hereinafter abbreviated as reception AGC operation), (1) changing the bias condition of the device of the amplifier circuit,
The gain of the amplifier circuit is changed. (2) A variable attenuator is incorporated in a reception high-frequency amplifier circuit or an intermediate-frequency amplifier circuit, and attenuation control is performed on signals passing through these amplifier circuits. There are two general methods.

[0005] The method (1) is used when the fractional band is narrow because not only the gain of the device but also other device parameters such as input / output impedance change with the change of the bias condition. Is used for (2).

Therefore, (2) will be described briefly.

In FIG. 6, a high-frequency signal received by an antenna 1 is amplified by a low-noise high-frequency amplifier circuit 3 in a receiving AGC circuit, and then input to a mixer 5.

Since a local signal from a local oscillator (not shown) is also input here, the high-frequency signal is converted into an intermediate frequency signal and output.

[0009] Then, the intermediate frequency amplifier 6 ₁ first intermediate frequency signal, the variable attenuator 7, through an intermediate frequency amplifier 6 ₂ is 2 distributed by the power distribution circuit 8, partly taken out as an AGC circuit output signal The remaining part is detected by an envelope detection circuit 9 and sent to a comparison circuit 10 as a detection voltage.

Therefore, the comparison circuit 10 compares the input detection voltage with the reference voltage and feeds back the difference signal to the variable attenuator 7, so that the variable attenuator 7 is output from the envelope detection circuit 9. The attenuation is controlled so that the detected voltage becomes equal to the reference voltage.

That is, when the received signal level is low, the attenuation of the variable attenuator 7 is small, and when the received signal level is high, the attenuation is increased. Since the amount varies, the difference signal corresponds to the input level of the received signal.

For this reason, the differential signal is transmitted to the reception signal monitoring circuit 1.
1 and is also used as a received signal level monitor.

[0013]

The conventional receiving AGC circuit has a configuration as shown in FIG. 6, and the level of the output signal of the AGC circuit sent from the power distribution circuit 8 is kept constant by the reference voltage. .

However, the environmental temperature of the wireless device changes, and the low-noise high-frequency amplifier circuit 3, the mixer 5, the first and second
If the gains of the intermediate frequency amplifiers 6 ₁ and 6 ₂ change, the reception signal level equivalently changes, and the reception signal level monitor in such a case will not show a correct value.

In order to correct the temperature error of the received signal level monitor by changing the reference voltage in accordance with the temperature change, the low-noise high-frequency amplifier circuit 3, the mixer 5, the first and the second 2 intermediate frequency amplifiers 6 ₁ , 6 ₂
A device having a temperature characteristic similar to that described above is required on the reference voltage side.

However, the elements used in the low-noise high-frequency amplifier circuit 3 are, for example, HEMTs and FETs, and the elements used in the mixer 5 are diodes. The device used will be different.

The device used for the reference voltage operates on a DC voltage, whereas the low-noise high-frequency amplifier circuit 3,
Devices used for the mixer 5 and the intermediate frequency amplifiers 6 ₁ and 6 ₂ are used in a high frequency band, and have different operating frequencies and different devices.

Further, the number of devices used in the reference voltage section is different.

That is, as described above, in addition to the difference between the devices themselves, the operating frequency is different, and the number of devices is different. Therefore, the difference in temperature characteristics is easily corrected by calculation in consideration of the device variation. However, there is a problem that it is necessary to select a correction device connected in multiple stages.

It is an object of the present invention to provide a reception level control circuit which omits the operation of selecting a correction device and reduces an error of a reception signal level monitor due to temperature characteristics.

[0021]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 1 (a) is a diagram illustrating the principle of the present invention, and FIG. 1 (b) is a diagram of a variable resonator that can be replaced with the variable attenuator in FIG. It is a block diagram.

In the figure, 2 is a power distribution circuit, 3 is a low-noise high-frequency amplifier circuit, 15 is a power combining circuit, 16 is a variable attenuator, 17 is a phase shifter, 18 is an amplifier, 19 is a detector, 2
0 indicates a comparator.

First, according to the first aspect of the present invention, a reception signal having a function of amplifying a reception signal by a high frequency amplifier, converting the signal into an intermediate frequency signal by a mixer using a local oscillation signal from a local oscillator, and outputting the signal. A first power distribution means for distributing an input signal to first and second distribution signals, and amplifying the first distribution signal by a high frequency amplifier. After that, second power distribution means for distributing the signals to the third and fourth distribution signals, and a phase shift portion and a variable attenuation portion are provided, and the phase shift portion is used to reverse the fourth distribution signal. A variable power synthesizing means for synthesizing the second distributed signal in phase and the fourth distributed signal whose level has been changed by the variable attenuation portion, and outputting a level difference of the synthesized signal; Variable so that is equal to the preset reference level. It controls the attenuation amount of the portion, provided with a control means for correcting the received signal level by using the variation of the attenuation amount at this time.

Further, the composition of the variable power combining means can be controlled in accordance with the reception level.

According to a second aspect of the present invention, the first power distribution means and the variable power synthesis means are replaced with a variable power distribution means and a power synthesis means having a variable attenuation portion.

Further, the control means controls the amount of attenuation of the variable attenuation portion provided in the variable power distribution means.

According to a third aspect of the present invention, the second power distribution means connected to the variable power combining means is connected to the output side of the first intermediate frequency amplifier, and the output side of the high frequency amplifier is connected to the variable power combining means. And first and second mixers are provided between the first and second mixers, respectively, and the first and second mixers are connected by a phase shift portion, and the phase shift portion and the first mixer are connected to each other. The mixer and the mixer were connected by a local oscillator, and a configuration was adopted in which a distribution signal was synthesized at an intermediate frequency.

According to a fourth aspect of the present invention, the first mixer and the second mixer
Are replaced with variable power distribution means having a phase shift portion and a variable attenuation portion, and the variable power combiner connected with the power distributor is replaced with a power combiner.

The level and phase of the intermediate frequency signal output from the first and second mixers can be controlled.

That is, the present invention has been made to reduce a received signal level monitor error due to temperature characteristics in the above-mentioned AGC circuit, and has been made to change the phase of the power distribution circuit and one of the outputs of the power distribution circuit. A low-noise amplifier circuit having a temperature characteristic in a loop composed of a power distribution circuit, a phase shifter, and a power synthesis circuit having a phase circuit and a power synthesis circuit for synthesizing both outputs again. By doing so, it is possible to correct a change in the gain of the low noise amplifier circuit according to the amount of synthesis of the power synthesis circuit.

That is, the gain change of the circuit having the temperature characteristic is corrected by a loop including a distribution circuit, a phase shift circuit, and a synthesis circuit. The distribution amount or the synthesis amount can be controlled from the outside, and the synthesis amount is controlled. The gain change of the low-noise high-frequency amplifier and the mixer having the temperature characteristic is corrected by feeding the obtained signal back to the distributor and the synthesis circuit.

Further, by adding this correction amount to the reception signal level monitor circuit, it becomes possible to monitor the reception level with the temperature characteristic corrected.

Next, the principle of the present invention will be described with reference to FIG. 1A. In FIG. 1, Pa, Pa ', Pb, and Pb' are distributed input signals. , P
a ', Pb, Pb'.

Now, a part of the distribution signal Pb amplified by the low-noise high-frequency amplifier circuit 3 is attenuated by the variable attenuator 16 to become a distribution signal Pb ′, and the distribution signal Pa is divided by the phase shifter 17 into the distribution signal Pb. It becomes the distribution signal Pa 'which becomes out of phase,
Both are combined by the power combining circuit 15.

Since the combined distribution signals have phases opposite to each other,
When the amplitudes of the distribution signals match, that is, the distribution signal P
Canceled when a '= distribution signal Pb', but 2
When the amplitudes of the two distribution signals do not match, that is, Pa '≠ P
If b ′, a signal level difference is output.

The output according to the signal level difference is amplified by the amplifier 18 to a detectable level.
9 to be detected.

The detected signal is compared with a reference level by a comparison circuit 20, and the amount of attenuation of the variable attenuator 16 is controlled so as to be equal to the reference level.

Next, a signal P input to a demodulator (not shown)
When the level changes, the following three cases can be considered. (A) When the input signal level changes (b) When the gain of the low-noise high-frequency amplifier circuit changes (c) When (a) and (b) are combined Here, the reference level is set to the distribution signal Pa ′. And distribution signal P
b ′ is set to a canceled state, and the distribution signal Pb ′>
If the distribution signal Pa ', the attenuation of the variable attenuator 16 is increased,
If the distribution signal Pb ′ <the distribution signal Pa ′, the variable attenuator 16
If the variable attenuator 16 is controlled so as to reduce the amount of attenuation of the signal P, the term (b) of the level variation of the signal P input to the demodulator will show the change in gain of the low-noise high-frequency amplifier circuit 3 depending on the amount of attenuation. Correction is possible.

That is, if the gain of the low-noise high-frequency amplifier circuit 3 does not change, the distribution signals Pa ',
The amount of attenuation for canceling the distribution signal Pb 'is the same, because the amount of change in the amount of attenuation reflects the change in gain.

Therefore, in the present invention, regarding the case that the gain change of the low-noise high-frequency amplifier circuit 3 is equivalent to the change of the received signal level described in the above-mentioned subject, the present invention provides a low-noise high-frequency amplifier. Since the circuit is placed in a loop, the gain change of the low-noise high-frequency amplifier circuit can be corrected by the attenuation of the variable attenuator 16 as described above.

On the other hand, with the above configuration, it is necessary to consider a change in the gain of the amplifier 18 of the detection circuit, but this change in gain can be ignored for the following reason.

That is, since the amplifier 18 does not need to demodulate the signal and only needs to extract the detection output with the detector, an amplifier having good temperature characteristics even if the noise is large or the linearity is poor is obtained. Can be used. Usually, when demodulating a received signal, a predetermined S / N is required according to the modulation method.

However, in the case of the detection circuit amplifier, it is only necessary to determine whether or not the distribution signals Pa ′ and Pb ′ have been canceled, and the above-described predetermined S / N is not required.

In FIG. 1A, the power combining circuit 15
In order to be able to change the synthesis amount of
Although the example using the variable attenuator 16 has been described, it is not always necessary to use the variable attenuator. For example, a variable gain amplifier (a temperature-compensated one may have large noise)
Alternatively, a coupler capable of changing the coupling amount may be used.

Further, although the phase shifter 17 is also provided on the Pa side in FIG. 1A, the same applies if it is provided on the Pb side.

FIG. 1B shows an example in which a variable resonator is used in place of the variable attenuator 16 shown in FIG. 1A.

Although the model diagram is composed of coils and varactors, it may be composed of distributed constant elements instead of lumped constant elements.

Although FIG. 1A shows the case where the variable attenuator 16 is connected to the power combining circuit 15, the variable attenuator 16 is connected between the power distribution circuit 2 and the low-noise high-frequency amplifier circuit 3. A similar effect can be obtained even if the processing is performed.

[0049]

FIG. 2 is a block diagram of a first embodiment of the present invention, FIG. 3 is a block diagram of a second embodiment of the present invention, and FIG. 4 is a block diagram of a third embodiment of the present invention. FIG. 5 and FIG. 5 are configuration diagrams of a fourth embodiment of the present invention.

In the figure, 1 is an antenna, 2, 4 and 8 are power distribution circuits, 3 is a low-noise high-frequency amplifier circuit, 5 ₁ and 5 ₂ are first and second mixers, 6 ₁ and 6 ₂ Is a first and second intermediate frequency amplifier, 7 is a variable attenuator, 9 is an envelope detection circuit, and 10 is a comparison circuit.

Reference numeral 11 denotes a received signal monitor circuit, 12 denotes a variable power combiner, 13 denotes a feedback amplifier, 14 denotes a variable power distributor, 15 denotes a power combiner, and 21 denotes a local oscillator.

The variable power combiner 12 shown in FIG.
The feedback amplifier 13 comprises a variable attenuator 16 and a power combining circuit 15 for variably controlling the combined amount. The feedback amplifier 13 comprises an amplifier 18, a detector 19, and a comparing circuit 20 in FIG. , One amplifier symbol.

Hereinafter, the operations of FIGS. 2 to 5 will be sequentially described.

In FIG. 2, the signal received by the antenna 1 is distributed by the power distribution circuit 2 at a predetermined ratio, and the signal is transmitted to the low-noise high-frequency amplifier circuit 3 and the signal is transmitted to the variable power combiner 12, respectively. .

Therefore, the signal is supplied to the low-noise high-frequency amplifier circuit 3.
After that, the signal is again divided into signals by the power distribution circuit 4.

[0056] After signal frequency-converted by the mixer 5 ₁ of the first, first, second intermediate frequency amplifier 6 _1, 6
_The signal is output at a constant power through an AGC circuit composed of the variable attenuator 7 and the variable attenuator 7.

The signal is sent to the variable power combiner 12 together with the signal.
Is input to

The feedback amplifier 13 controls the amount of synthesis of the variable power combiner 12 so as to cancel the synthesized signal.
Since this signal is added to the received signal monitoring circuit 11 constituting the circuit, this circuit corrects the received signal level and outputs the corrected signal.

Here, assuming that the levels of the above signals are P1 and P2, the level of the input signal from the antenna is P, and the distribution ratio of the power distribution circuit 2 is x, P1 = P · x / (1 + x) P2 = P / (1 + x).

Assuming that the gain of the low-noise high-frequency amplifier circuit 3 is G and the distribution ratio of the power distribution circuit 4 is y, the signal,
P3 = P1 · Gy / (1 + y) = P · x / (1 + x) · Gy / (1 + y) P4 = P2 · G · 1 / (1 + y) = P / ( 1 + x) · G / (1 + y).

Here, since x and y in P1 to P4 are constants as described above, they can be expressed as P4 = A ＝ G ・ P P2 = B ・ P.

Note that A = 1 / (1 + x) · 1 / (1 + y) B = 1 / (1 + x).

Now, when the attenuation of the variable attenuator in the variable power combiner 12 is controlled to make the combined amount 1 / z, in the variable power combiner 12, (P4 / z) -P2 = (A · G ・
P / z)-BP.

Here, if z is adjusted and one item on the right side and two items are made equal, A / GP / z = BP and G =
z · B / A.

Then, from the above G = z · B / A, it is possible to detect the gain G of the low-noise high-frequency amplifier circuit 3 by z which is the reciprocal of the synthesis amount.

That is, as shown in FIG. 2, since the low-noise high-frequency amplifier circuit 3 is included in a loop formed by the power distribution circuits 2 and 4 and the variable power combiner 12, the low-noise high-frequency amplifier circuit due to temperature fluctuations. If the gain of No. 3 fluctuates from G → G ′, z → z ′ to compensate for the gain fluctuation.

However, even if the input signal level changes from P to P ', z does not change to z'.

That is, the variation of z, which is the reciprocal of the synthesis amount, is a value corresponding to the variation of the gain of the low-noise high-frequency amplifier circuit. The signal is supplied to the reception signal monitor circuit 11 via the circuit 10 and the like.

Accordingly, when the input level to the AGC circuit (the input level of the variable attenuator 7 in the figure) changes,
Whether the change is a change in the received signal level (P → P ′), a change in the gain (G → G ′), or a change in both, can be determined in the state of z described above. Signal level monitoring becomes possible.

Referring to FIG. 3, variable power combiner 12 shown in FIG.
Corresponds to the case where the function of
The basic operation is the same as in FIG.

However, in the case of FIG. 3, since a power divider with a variable attenuator is provided on the input side, when the received signal level decreases, the low-noise high-frequency amplifier circuit 3 and the first and second intermediate circuits are provided. The power distribution to the main line to which the frequency amplifiers 6 ₁ and 6 ₂ are connected is increased, and when the received signal level is increased, the power distribution to the main line is reduced. It is possible to make the C / N of the signal input to the device better than in the case of FIG.

In FIG. 4, the phase shifter 17 is connected to the local oscillator 2
1 and it has been placed between the second mixer 5 _2, be provided at the output stage of the power distribution circuit 2 or a variable power combiner 1,
It may be installed in the previous stage of 2.

[0073] In this configuration, the power distribution circuit 2, first mixer 5 _1, the power distribution circuit 4, the variable power combiner 12, a low noise radio frequency amplifier in the loop constituted by the second mixer 5 ₂ since circuit 3 and the first intermediate frequency amplifier ₆₁ is provided, in addition to the low-noise high frequency amplifier circuit 3, the correction is possible of the first temperature characteristic of the intermediate frequency amplifier 6 _1.

Also, as in the case of FIG.
The same applies to the case where variable means is provided in the first embodiment.

[0075] Figure in 5, which was placed between the mixer 5 ₁ phase shifter 17 local oscillator 21 by changing the variable power divider 14 which gave level control function and the first 4,
As in FIG. 4, the temperature characteristics of the _first intermediate frequency amplifier 61 can be corrected in addition to the low noise high frequency amplifier circuit 3.

[0076]

As described in detail above, according to the present invention, when the input level of the AGC circuit changes, it is determined whether the received signal level itself has changed or the gain of the amplifier has changed. The determination can be made separately, and an effect of correcting the influence of the change in the amplifier gain at the time of monitoring the received signal level can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a configuration diagram of a first embodiment of the present invention.

FIG. 3 is a configuration diagram of a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of a reception automatic gain control circuit of the heterodyne wireless device.

[Explanation of symbols]

1 Antenna 2 4,8 power distribution circuit 3 low-noise high frequency amplifier circuit 5 _1, 5 ₂ first, mixer 6 ₁ of the second, 6 ₂ first, second intermediate frequency amplifier 7 variable attenuator 9 envelope Circuit 10 Comparison circuit 11 Received signal monitoring circuit 12 Variable power combiner 13 Feedback amplifier 14 Variable power distributor 15 Power combiner 16 Variable attenuator 17 Phase shifter 18 Amplifier 19 Detector 20 Comparator 21 Local oscillator

Claims (4)

[Claims] 1. After amplifying a received signal with a high frequency amplifier,
A receiver having a function of converting a local oscillation signal from a local oscillator into an intermediate frequency signal by a mixer and outputting the signal, wherein an automatic gain control circuit for making a reception level constant, wherein an input signal is a first signal. A first power distribution means for distributing the first distribution signal to a second distribution signal, a second power distribution means for amplifying the first distribution signal by a high-frequency amplifier, and then distributing the amplified first and third distribution signals to third and fourth distribution signals. A phase shift portion and a variable attenuation portion are provided, a second distribution signal having a phase opposite to the fourth distribution signal using the phase shift portion, and a fourth level having a level changed by the variable attenuation portion. Variable power combining means for combining the divided signals and outputting the level difference of the combined signal; controlling the amount of attenuation of the variable attenuation portion so that the input signal level difference becomes equal to a preset reference level; , Using the change in attenuation at this time, A reception level control circuit, comprising: control means for correcting a level. 2. The variable power distributing means and the variable power distributing means having a variable attenuation portion are replaced with the first power distributing means and the variable power synthesizing means, and the control means is provided in the variable power distributing means. 2. The reception level control circuit according to claim 1, wherein said reception level control circuit is configured to control an amount of attenuation of said variable attenuation portion. 3. The second variable power combining means connected to the variable power combining means.
Is connected to the output side of the first intermediate frequency amplifier, and first and second mixers are provided between the output side of the high frequency amplifier and the input side of the variable power combining means, respectively. A configuration in which a first mixer and a second mixer are connected by a phase shifter, a phase oscillator is connected by a local oscillator between the first mixer and a second mixer, and a distribution signal is synthesized at an intermediate frequency. 2. The reception level control circuit according to claim 1, wherein: 4. A phase shifter connected between the first mixer and the second mixer, the phase shifter being connected to a variable power distributor having a phase shifter and a variable attenuator, the phase shifter being connected to a power distributor. The variable power combiner is replaced with a power combiner so that the level and phase of the intermediate frequency signal output from each of the first and second mixers can be controlled.