JPH03179818A - Agc controlled communication equipment and level controller - Google Patents

Abstract

PURPOSE:To reduce signal distortion and to make output stable even when a strong input allowable range is increased by changing an attenuator potential of a filter to attenuate a strong input of an object frequency. CONSTITUTION:The attenuator potential of filters 1, 3 is changed corresponding to the signal of a feedback circuit 6 detecting the gain output of an amplifier element with a strong input against the strong input in excess of the specified gain of an amplifier element 5 having the filters 1, 3 determining a pass frequency band at its input side. While the input is attenuated, the allowable strong input range of the amplifier element 5 is increased corresponding to the sum attenuation force of one or plural filters 1, 3 used for the input side of the amplifier element 5 to control the specified output or below with respect to the increased strong input allowable range. Thus, both S/N and TDH are kept constant and the effective range of the stable operation is increased.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to improvement of the individual input characteristics of an automatic gain control circuit (AGC), and is concerned with the improvement of the individual input characteristics of an automatic gain control circuit (AGC), and the control of the output within the standard in response to the expansion of the allowable intensity range of input waves. The present invention relates to a level controller that performs this and an AGC-controlled communication device that has excellent individual input characteristics.

AGC devices are effective in suppressing distortion of signal waveforms or suppressing noise caused by clicks, and are particularly widely used in communication systems such as heterodyne systems.

[Prior Art] In the receiving system of a conventional wireless communication device shown in FIG.
A obtained by rectifying the signal applied to the detection stage 103 at J
The GC voltage is applied to the amplifying section 100 in the previous stage, and the degree of amplification is lowered in inverse proportion to the magnitude of the AGC voltage.

The reception strength of radio waves can become very strong due to changes in reception conditions such as passing through a tunnel, moving from the plains to a hill with good reception conditions, between buildings, or approaching a broadcasting station, so it is important to adjust the bias of the amplification section at this time. The above AGC voltage is used to increase the gain reduction and control the gain within the specified or standard range. However, this gain control has the fact that the input waveform is distorted even if the gain is lowered (Figure 7 [1
1], see d-line>. The degree of gain reduction is usually 30 dB per amplification stage, which cannot be said to be sufficient.

Also, if this process is forward AGC control, the AGC
Because a large amount of bias current is passed through the amplifier stage for control purposes, conditions deteriorate, leading to an increase in current consumption.This deterioration of conditions is difficult to ignore, especially in portable receivers and radios.
This method is difficult to adopt.

Alternatively, in the case of reverse AGC control, there are times when the necessary gain reduction cannot be obtained unless the AGC voltage is reduced to a negative voltage, resulting in a costly system that requires a negative power supply circuit in preparation for such situations, so this method was not adopted. It's difficult.

[Problems to be Solved by the Invention] It is an object of the present invention to further expand the input wave intensity limit of 30 to 50 dB in conventional AGC devices and to avoid an increase in current consumption. We will develop a level controller that has an output within the standard for the input and can output with little distortion, and at the same time develop an AGC-controlled communication device that is immersed in strong input characteristics.

As mentioned above, the input conditions for gain control of the AGC device are clearly narrow, so the AGC device expands its automatic control capability to a level controller that can be used as a highly independent gain control device that widens the effective range of stable operation. It needs to be developed.

[Means for Solving the Problem] The present invention provides feedback for detecting the gain output of the amplification element of the strong input for a strong input that exceeds the specified gain of the amplification element having a filter on the input side that determines the pass frequency band. While changing the attenuator and attenuator of the filter in accordance with the signal of the circuit and attenuating the input, For example, 8
It is possible to tolerate a strong input of 0 dB, achieve control of a standard output of, for example, 0.2 V or less within this expanded strong input tolerance range, and maintain both S/N and TDH constant.

Further, the present invention provides an AGC-controlled henodyne communication device in which AGC voltage changes are applied to a feedback circuit that provides a band tracking error of a high-frequency filter to cause a tracking error in the high-frequency filter, and the tracking error is transferred to a lower heterodyne. In the case of the heterodyne method, this is performed by an upper shift, and in the case of an upper heterodyne method, it is performed by a lower shift, and the tracking band is shifted in a direction away from the image wave generated in the heterodyne method to avoid amplification of the image wave, and the above shift is performed. By lowering the input strength of the target frequency using the damping force of the error tracking band and controlling the AGC voltage within the specified range, a strong input of, for example, 80 dB can be tolerated, and the standard output can be adjusted for this expanded strong input tolerance range. For example, 0.
It is possible to obtain an AGC-controlled communication device that achieves control of 2V or less and has excellent strong input characteristics that keep both S/N and TDH constant.

[Operations and Embodiments] In the AGC-controlled communication device shown in the embodiments of FIGS. 1(A) and 1(B), the AGC voltage taken out from the detection stage 6 is fed back to the ordinary filter 1.3.

The high frequency amplification stage 2, mixer 4', and IF amplification stage 5, which are the conventional main circuits of the communication device, do not require any modification.

The capacitor potentials of filters 1 and 3, which receive 〇C voltage from the ac circuit, are converted into degrees and the filter passband is shifted to obtain gain reduction for two filters. For normal input, filter l
, 3 (7) The g range is tuned to the LI target frequency o, and when the input level increases and becomes a strong input above a certain level, the detection voltage ratio should be adjusted according to the above feedback voltage so that 6 < constant. If the Luther band shifts, see Figure 2 [A and B]. The tracking error caused by the filter is instantaneous and has no effect on peripheral circuits.

The relationship between the front end band and gain shown in Figure 3 is well known.The reduction rail used in the filter system is determined by the performance and number of stages of the filter, and in the case of the communication device in this example, 60~80dB
To some extent. The passband shift voltage 1) for this is also:
It can be determined by the performance of the filter and the number of stages, and in the case of the communication device in this example, there are

In this example, by shifting the front end in the range f) to 3v, 0 to 80 d [3)/injection can be obtained continuously. The dissipation c in the figure is calculated from the gain (dB) of the amplification element to the filter loss (dB).
).

Part 4 shows an example of creating a band control 1-luminium voltage Vc from the AGC voltage. Is it the detection voltage of detection stage 6? ,IV.
Since the OJ distortion of the detected waveform was low, I used dividing resistors rL and r2 to set the voltage to +, tV for 70 operational amplifiers under these conditions. O for lV tonneau F
dDetermine the exclusiveness of the 21st incubation so that it will be the reaction of B. The ten terminals Vl of the operational amplifier 7 are connected to the dividing ends of the dividing resistors r1.1 and r2, and one terminal V2 is connected to the detection stage 6, respectively. A transistor 9 provided at the output end of the operational amplifier 7 outputs a voltage range control voltage Vc.

Figures 5(A> and 3) show the relationship between the filter 10 and the band control voltage Vc.

FIG. 5(A) is an example of a lower heterodyne zero-matching circuit. A band control voltage Vc is inputted via a diode 8 between the capacitor 10c and the varicap 10a with a voltage of χ·1 to a filter 10 composed of a capacitor 10c and a varicap lOa and a coil 10b. A diode 8'i is also provided on the setting line G that provides the maximum gain setting voltage to ensure independence between both input lines.

Therefore, the band control voltage Ve acts to add a voltage to the maximum gain setting voltage, and the filter 10 band h11! ++ Shift 1 te. This maximum gain setting voltage is a setting value to obtain the maximum gain for the average intensity input of the target frequency (band kJi) fo, for example, a variable control oscillator used in frequency or amplitude modulation of communication equipment. (It is best to create it by taking the voltage from V C (J).

In the case of the upper heterodyne shown in FIG. 5(B), the band control voltage VC is input to the base of the transistor 11 whose collector is connected to the setting line G. This band control voltage Vc (, which controls the collector-emitter voltage) acts to lower the maximum gain setting voltage, effecting a downward shift of the filter passband.

As described above, in the present invention,
- One feedback circuit for the Lumi pressure Vc is shared with the maximum gain setting line G as is. Auto gain control (
When the maximum gain of A G (,:) is exceeded by 1, the band control voltage Vc obtained from this AGC voltage causes a band tracking error in the filter, and the L: It attenuates a strong input with a uniform dark wave number fO.This feedback loop 1ij3144 is superior to the conventional bias variation flip-flop operation of the amplification stage.

The comparative S/N curve shown in FIG.
dO is quite stable. The A + and C voltages vO are completely stable within the standard or specified value, and there is no possibility of instability in one movement. When the input level is 50tJB or more, the band control voltage Vc follows this f, 'Ii1 function, and the east limit 1 is over 50tJB. The AGC output fy is stabilized, and the S/N ratio remains constant.

The effective diagram of the conventional feedback circuit shown in FIG. 7 [11] shows the actual situation where the AGC voltage distortion curve (j) changes with respect to the RF input, and the same figure [11] shows the RF input without the feedback circuit. A G C voltage V for
and the distortion curve d0 shows large fluctuations.

The bell controller of the present invention, which stabilizes the output and distortion over a wide range of input conditions, is commonly applied to the fall, and its true value is clearly demonstrated.

[Invention 0 Effect Song] The level controller of the present invention changes the attenuator potential of the 1° filter and attenuates the strong input of the target frequency 8fO. It is far superior to feedback in that it has less signal distortion and is more stable, and the stability of the output when the strong input tolerance is expanded is far superior to the conventional U, 71.

A t that utilizes the characteristics of this level controller:
; C-controlled communication equipment performs stable signal amplification under more expanded input conditions than conventional ones, and filter band shift control further reduces the influence of incidental image waves in the terodyne system. The stable signal amplification characteristics with low single-word distortion can dramatically increase the reliability of communication devices as well as expand the strong input range.

[Brief explanation of drawings]

Figure 1 [AI, [B] is an electrical block circuit diagram showing an embodiment of the present invention, Figure 2 [AJ, [B] is a graph showing the RI range shift, and Figure 3 is a graph showing the filter W function. basic diagram,
FIG. 4 shows an example of the main part of the feedback circuit, FIG. 5 (A), (B) shows an example of filter fi control, and FIG.
1-band control voltage VC and distortion characteristics ti o
Graphs [1] and [11] in FIGS. 7A and 7B are graphs showing the conventional bias feedback effect and the case without feedback, respectively, and FIG. 8 is an electric circuit block diagram of a conventional communication device. 1. 3: Filter vOl v: AGC voltage vc: Band control voltage (1o1 1d: Distortion characteristics

Claims (1)

[Claims] 1) For a strong input that exceeds the specified gain of an amplifying element having a filter that defines a pass frequency band on the input side, the attenuation of the filter is adjusted in response to a signal from a feedback circuit that detects the gain output of the amplifying element of the strong input. Nuator
While changing the potential and attenuating the input, the permissible strong input range of the amplifying element is expanded in accordance with the total attenuation force of one or more filters used on the input side of the amplifying element, and amplification for the strong input is performed. Level controller 2) AG characterized by keeping the output within a specified range
In a C-controlled heterodyne communication device, AGC voltage changes are applied to a feedback circuit that gives a band tracking error of a high frequency filter to cause a tracking error in the high frequency filter, and the tracking error is shifted upward in the case of a lower heterodyne system. In the case of the upper heterodyne method, the lower shift is performed to avoid amplification of the image wave by shifting the tracking band away from the image wave generated in the heterodyne method, and to reduce the attenuation force of the shifted error tracking band. to reduce the input strength of the target frequency and
An AGC-controlled communication device characterized in that voltage is controlled within regulations.