JPS5915417B2 - RF speech processor circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the configuration of a circuit in an SSB transceiver that uses two filters to operate as a variable bandwidth intermediate frequency amplifier during reception and as an RF speech processor during transmission.

Regarding the variable band circuit using two filters in the intermediate frequency amplification stage of the SSB receiver, which is the basis of this invention, the present applicant has filed Utility Model Registration Application No. 132110 of 1982.
The application has been filed as "Variable Bandwidth Circuit for SSB Receiver" and its outline is as follows. In FIG. 1, a USB filter 1 and an LSB filter 2 of an intermediate frequency amplification stage are connected in cascade, and switch circuits 3 and 4 are provided to bypass unnecessary filter signals as necessary.

The USB filter and the LSB filter may be arranged in a different order, and a buffer or an amplification stage may be added as necessary. The characteristics of this filter are as shown in Figure 2.
For B, the USB carrier is placed on the slope of the low frequency side of the filter with a high center frequency, and for LSB, the LSB carrier is placed on the slope of the high frequency side of the filter with a low center frequency.
B carrier is used, and when LSB, LSB filter and L
Since the SB carrier is used, the reception bandwidth is the same as the bandwidth of the filter used. Next, when both filters are used in cascade, the total bandwidth is only the portion where the bands of both filters overlap, so the bandwidth is narrowed by the difference between the center frequencies of both filters.

At this time, since the frequency of the filter is shifted so that the bands overlap on the side of the slope where the carrier is located, the characteristics hardly change, and only the slope on the other side has a narrow band width. It is effective in removing signal interference and high-frequency components of noise that are easily perceived by the ears. Furthermore, when the band is narrowed in this way, the attenuation characteristics of both pools overlap, so the amount of out-of-band attenuation increases additively, making it even more effective in eliminating interference, which is the objective of the narrow band. In the present invention, the two filters described above are effectively used during SSB transmission. Generally, most SSB transmitters use an intermediate frequency carrier and an audio signal to generate an SSB signal. In addition to the balanced modulator, a DSB signal with reduced carrier is created, and this is further converted to 2 to 31(]I
An intermediate frequency SSB signal is created by attenuating unnecessary sidebands and carriers through a z-width filter.

In the case of an SSB transmitter/receiver, the carrier oscillator (BFO) and intermediate frequency filter used for reception are usually used for transmission as well. In this case, it is natural to use a combination of an LSB carrier and an LSB filter to generate an LSB wave, and a combination of a USB carrier and a USB filter to generate a USB wave. In the present invention, an RF speech signal is added to the transmitting intermediate frequency stage.
A processor is provided to effectively utilize unused filters. The RF speech processor in the SSB transmitter is a circuit that passes the DSB signal output from the balanced modulator through a filter to produce an SSB signal, cuts off the peak portion of the signal amplitude using a limiter, and supplies the signal through the filter again to the next stage.

The purpose of this is that the amplitude-modulated signal waveform of the audio signal has a large peak amplitude but an extremely short duration, so cutting it off will not significantly reduce intelligibility and will not overload the transmitter's power amplifier. The reason is that the average transmission power that can be output can be increased. However, it is necessary to add a filter to remove various strain components generated by passing through the limiter, which poses a problem of increased manufacturing costs. In normal AM and FM transmitters, the audio signal before modulation is normally applied to a limiter, but with SSB
Since the waveforms of the modulating signal and the modulated signal are not similar, as far as a power amplifier that handles SSB signals is concerned,
Recognizing the effectiveness of the RF sweep processor that limits the SSB signal stage, a filter has been installed to be used only for this circuit. The present invention is based on the above-mentioned utility model registration application No. 132110 of 1982 "SSB
In an SSB transmitter/receiver that applies a "receiver variable bandwidth circuit", the DSB signal output of the balanced modulator is converted into an SSB signal through the USB filter 1 during reception, and is converted into an SSB signal through the limiter 5 during transmission, as illustrated in FIG. Furthermore, the spurious generated by the limiter is removed through the LSB filter 2 at the time of reception, and the speech processor is operated as an RF speech processor to be sent to the subsequent stage, making effective use of the two filters used for reception. , an RF speech processor circuit can be formed by simply adding a limiter stage between them.

Note that the order in which signals pass through the two filters is reversed depending on whether the signal passes in the same direction or in the opposite direction during reception and transmission, but this does not pose any problem in operation.

Also, as a result of using two filters in cascade, the overall passband width becomes narrower for the same reason as when receiving.
RF speech processors are used when communication conditions are poor, and the receiving side also tries to reduce noise by narrowing the band and cutting out the high frequency range, so the narrow band for transmission is effectively It doesn't really matter. Further, although distortion is likely to occur due to the fact that the transmission power stage is fully driven, there is also the advantage that distortion is somewhat less if the drive signal band is narrower. When the RF speech processor is not used, switch 3 in FIG. 3 for USB is opened to operate USB filter 1, and switches 4 and 6 are closed to allow the other stages to pass. For LSB, the switch is opened to operate the LSB filter 2, and the switches 3 and 6 are closed to allow the other stages to pass. The interlocking operation of these switches 3, 4, 6 and the LSB carrier and USB carrier switches would be complicated if they were mechanical switches, and if there is a problem of leakage between circuits, electronic switches may be used.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a receiving bandwidth variable circuit of an SSB transmitter/receiver to which the present invention is applied, Fig. 2 is a diagram explaining the operation of the circuit in Fig. 1, and Fig. 3 is a block diagram of an SSB signal generation circuit to which the present invention is applied. Show the diagram. 1, 2...SSB filter, 3, 4, 6...
...Switch, 5...Limitsuta.

Claims (1)

[Claims] 1 SSB that uses an intermediate frequency amplification stage for both transmission and reception
In the intermediate frequency amplification stage of the transmitter/receiver, two filters with approximately equal bandwidths are connected in cascade during reception. The LSB carrier is set on the high frequency side of the low filter, and the center frequency difference between the two filters is set to be approximately equal to the frequency at which the bandwidth is desired to be reduced, and the desired side hand filter and carrier are used during wideband reception. The unnecessary sideband filter bypasses the signal, and during narrowband reception, both filters are used in cascade to form a bandwidth switching circuit that operates the carrier of the desired sideband, and when transmitting, the intermediate frequency stage is balanced. Commonly used to shape and amplify the DSB signal from the modulator into an SSB signal,
A circuit system for an SSB transceiver, characterized in that an RF speech processor circuit is formed by providing a limiter stage between two filters.