JPH0117852Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to the structure of an AGC circuit in a radio receiver that amplifies and processes the carrier and sideband separately.

It is well known that the SSB (A3J) method is superior to the DSB (A3) method in reducing the effects of selectivity fading. However, in SSB,
Since it is necessary to take a large holding time constant of AGC,
It has the disadvantage that it is difficult to respond to sudden changes in strength. Furthermore, even in a normal A3 wave receiver, the followability of AGC is limited due to the time constant of the filter circuit to prevent modulation components from entering the AGC circuit.

In this device, the carrier and sideband are received through separate selective amplifiers in the intermediate frequency stage of the radio receiver, and the carrier is rectified.
AGC voltage and AGC obtained by rectifying sidebands
By adopting a structure in which the AGC voltage synthesized through separate time constant circuits is applied to each of the carrier amplifier, sideband amplifier, and shared amplifier, the AGC voltage by the carrier is first
Since the voltage does not include a modulation component, the time constant of the filter can be set to an extremely small value to remove the carrier component, and the follow-up performance of this AGC is quick.
Next, the AGC voltage obtained by rectifying the sideband or the AGC voltage obtained by rectifying the audio signal detected by the sideband is passed through the fast attack/slow release time constant circuit as in the case of SSB. By mixing different types of AGC voltages in appropriate proportions (through an AGC amplifier if necessary) and applying them to each of the carrier amplifier, sideband amplifier, and shared amplifier, AGC by carrier
Since the time constant of the circuit is small, it can follow fast changes in signal strength well. Also, AGC using sidebands is useful when the sidebands suddenly become stronger due to selective fading, and is effective when receiving SSB signals without carriers with this circuit.

Next, an example of an applied circuit will be explained with reference to FIG. 1
is an antenna, and 2 is a high frequency amplifier, which is a shared amplifier for the carrier and sideband. 3 is converted to an intermediate frequency by a mixer, and is applied to a product detector 6 and an AGC rectifier 7 through a sideband filter 4 and an amplifier 5. Carrier is carrier filter 8
and is applied to the AGC rectifier 10 through the amplifier 9.
As mentioned above, in the sideband AGC and carrier AGC, the outputs passed through appropriate time constant circuits are combined and output as an AGC voltage (amplified if necessary) to the high frequency amplifier 2, the sideband amplifier 5, and the carrier amplifier 9. In addition to this, perform AGC operation.

FIG. 2 shows an example of a circuit configuration in which the sideband AGC voltage generation circuit is different from that in FIG. 1, and the audio signal demodulated by the product detector 6 is rectified (amplified if necessary) by the AGC rectifier 11. and AGC
The only difference from Fig. 1 is that it uses an audio hang AGC method to obtain voltage, and everything else is the same as Fig. 1.

[Brief explanation of the drawing]

Figure 1 shows an example of the circuit configuration of the present invention;
The figure shows another example of the circuit configuration. 2, 5, 9...Amplifier, 3...Mixer, 4...Sideband filter, 6...Product detector, 7,
10, 11...AGC rectifier, 8...Carrier filter.

Claims (1)

[Claims for Utility Model Registration] (1) In the intermediate frequency stage of a radio receiver, the carrier and sideband are received through separate selective amplifiers, and the AGC voltage obtained by rectifying the carrier;
The AGC voltage obtained by rectifying the sideband was synthesized through separate time constant circuits.
A structure of a receiver circuit characterized in that an AGC voltage is applied to each of a carrier amplifier, a sideband amplifier, and a shared amplifier. (2) The structure of the receiving circuit according to claim 1 of the utility model registration claim, wherein the AGC obtained by rectifying the sideband is obtained by rectifying the intermediate frequency output. (3) The structure of the receiving circuit according to claim 1 of the utility model registration, wherein the AGC obtained by rectifying the sideband rectifies the audio signal obtained by detecting the sideband.