JPS61208322A - Speech processor circuit - Google Patents

Abstract

PURPOSE:To attain adjustment of attenuation of a low or high frequency modulation component of a signal to be modulated by providing a frequency converting circuit to the input and output of an SSB speech processor circuit, applying a local oscillating frequency injected it from one local oscillator and adjusting minutely the frequency of the local oscillator. CONSTITUTION:A DSB obtained by a modulation signal and an output of a carrier oscillator 24 to a balanced modulator 22 is given to an SSB filter 25 to obtain an SSB signal, which is given to a speech processor circuit 1, an output of the oscillator 24 is injected to the demodulator 23 to apply product detection. As the demodulator 23, it is desired to use a double balanced demodulator eliminating a spurious output. The tone control of high/low cut of the modulation signal is applied by adjusting minutely the frequency of the oscillator 24, and since the output of the demodulator 23 is a sound signal whose amplitude and frequency characteristic are adjustable, and it is used to constitute an independent device as an adaptor to modulate other than the SSB.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a peach processor circuit for improving speech intelligibility by increasing the average modulation degree of a modulated signal in a transmitter used for wireless communications.

[Prior art and problems]

Many wireless communication devices are equipped with a tone control that changes the frequency characteristics of the reproduced sound in order to make the received sound easier to hear, but a similar tone control on the transmitter side may also be effective. In communication equipment, clarity or intelligibility is more important than so-called sound transmission, so it is better to cut out the audio band, so microphone amplifiers generally attenuate frequencies below about 300 Hz, and attenuate frequencies from 1000 to 2000 Hz to some extent. Enhancement improves clarity, but causes unnecessary sidebands.3
000 Hz and above are cut through as sharply as possible. The tone control circuit for this purpose is a simple CR that allows gradual increases and decreases of 6 dB or less in octave heat.
This can be achieved with a circuit, but in order to cut the low and high frequency ends sharply, a filter using LC or an active filter using transistors and CR is required.
There are problems in terms of cost and space.

[Purpose of the invention]

An object of the present invention is to provide a speech processor circuit that can sharply cut the low end or high end of modulated sound and vary the cut frequency by using the speech processor circuit used in an SSB transmitter. shall be.

[Summary of the invention]

This invention is described in claim 1, and as shown in FIG. By supplying frequencies 41 and 42 from the same local oscillator 4 and finely adjusting the frequency of the local oscillator 4, the relative frequency relationship between the modulated signal 21 passing through the speech processor 1 and the filter 12 of the speech processor 1 is changed. In amateur radio communication, which aims at long-distance communication with low power, transmission The SSB communication method is often used in the machine output stage, which transmits only one sideband wave by removing one of the carrier wave and the upper and lower sideband waves, which have a large power burden. A means is used to increase the average modulation depth by compression or restriction to increase the reception output and extend the communication distance even with the same antenna power, and is called a speech processor.

FIG. 4 shows the general configuration of the SSB speech processor circuit. In a general SSB transmitter, the output 51 of the microphone amplifier 5 and the output 61 of the local excavator (also called a carrier oscillator) 6 are connected to a balanced modulator (hereinafter referred to as a carrier oscillator). (hereinafter abbreviated as BM)22, the resulting DSB signal is removed by a BPF to obtain an SSB signal, which is then subjected to frequency conversion and amplification.The average modulation degree of the audio signal is Since it is less than 30% of the peak value, if a small amount of the peak portion is cut, the average modulation degree becomes 50-60%, and the same effect as doubling the transmission power can be obtained.

However, if a limiter is installed in the microphone amplifier to cut the peak, harmonic distortion will occur that cannot be removed by a filter, so a complex amplitude compression circuit is required.
In SSB, the modulation signal waveform and the SSB signal waveform do not match because the carrier wave and undefined sideband waves are removed.
There is a special situation in which a sufficient effect cannot be obtained by limiting the amplitude in a microphone amplifier circuit. Therefore, in the SSB speech processor, amplitude compression or amplitude limitation is performed in the SSB signal part, and one part of the IE4 diagram is an example of this. IIA is a variable gain amplifier, IIB is an amplitude limiter, and the gain of IIA is If the output amplitude of IIA is smaller than the limit level of 11B, the limiter will not operate,
If you increase the gain of IIA and increase the output amplitude, IIB
The dyne adjuster of 11A can be used to adjust the speech processor operation since the average inflection level becomes deeper by clipping above the limit level of . Distortion caused by waveform clipping is removed by passing it through BPF' 12. In this case, since the passband width is narrower than the center frequency of the BPF, no problem arises in removing harmonics.

As shown in Fig. 5, the relationship between the SSB filter or the 111PF 12 and the passing signal is based on the relationship between the bandpass frequency (8) of the filter and the carrier (suppressed by about 20 dB by BM) frequency of the DSB signal CB). It depends on the location, but usually the center frequency of the BPF is placed 1500 Hz above or below the carrier frequency, and if the BPF bandwidth is 2400 Hz, the sideband (in the case of the figure, the upper sideband) is 300-2700Hz. , and the carrier is 15 dB or more, no! ! Sideband waves are suppressed by more than 40 dB. (q is when the carrier frequency is brought close to the filter, (to) is when it is far away, in (C) the high frequency side (shaded area) of the sideband is suppressed, and in p) the low frequency is 11tll
(shaded area) is suppressed, so it can be seen that in the case of (C), the treble part is cut, and in the case of (■), the bass part is cut. Therefore, by slightly changing the carrier frequency, high-cut or low-cut of the modulated sound can be easily achieved, but since a change in the carrier frequency results in a change in the transmission frequency, it is inconvenient to use this for tone control. be.

In the present invention, when the SSB signal 21 shown in FIG. 1 passes through the BPF 12 of the speech processor 1, by finely adjusting the local oscillation frequency 41 of the frequency conversion circuit 2 on the input side,
Tone control is performed by finely adjusting the carrier frequency position of the SSB signal 21, and the output frequency can be kept constant by supplying the local oscillation frequency 42 of the output side frequency conversion circuit 30 from the same local oscillator 4 as 41. . This means that the input frequency to frequency converter 2 is f
If the local oscillation frequency is fo, the output frequency is f1
±f0, which is again f in the frequency conversion circuit 3.

If mixed with
or f1±2f0...(2)
It is proved that (2) is easily removed because the frequencies are greatly different, and that the same f as the input is output from (1).

Note that since the balanced modulation circuit and balanced demodulation circuit (or product detector) that inject local oscillation are a kind of frequency conversion circuit, claim 2 states that the input side of the SSB speech processor is a balanced modulation circuit. , the case where the output side is a balanced demodulation circuit or a product detector is disclosed. The details will be described in the following section of the embodiments of the invention.

Claim 3 provides that the local oscillator includes a BF of the receiving section.
A configuration using a local oscillator including O is disclosed, and the details thereof will be described in the section of other embodiments.

[Embodiments of the invention]

FIG. 2 is a block diagram of an SSBS bispeech processor control circuit to which the present invention is applied, in which the DSB obtained by adding the modulation signal and the output of the carrier oscillator 24 to the balanced quality amplifier 22 is passed through the SSB filter 25 to produce the SSB signal. Then, product detection is performed by injecting the output of the oscillator 24 into the demodulator 23 through a speech-grossing circuit. Preferably, the demodulator 23 is a double-balanced demodulator capable of removing unnecessary outputs.

In this configuration, it is clear from the above description that high-cut/low-cut tone control of the modulation signal can be achieved by finely adjusting the frequency of the oscillator 240.
The output of No. 3 has amplitude and frequency characteristics of 'v? Since it is a 4-way adjustable audio signal, it is also possible to configure an independent device as an adapter that can perform modulation in formats other than SSB.

[Other Examples]

(SSB) In Lancers, the transmitting circuit and the receiving circuit often have the same frequency configuration, and the intermediate booster stage or local oscillator is often used for both transmission and reception, but the configuration of the present invention also uses a local oscillator that finely adjusts the tone control. In many cases, the local oscillator of the receiving section can be shared.

FIG. 3 is a block diagram of an embodiment of the present invention in which the BFO of the receiving circuit and the carrier oscillator of the transmitting circuit are shared. The transmission signal circuit in the figure is the same as the configuration in Figure 2,
If the frequencies of BPF 31 and BPF 25 of the receiving section (other than BPF 31, intermediate frequency amplifier 32, and product detector 33 are omitted) are the same (often the same), then the receiving BFO 34 is Since the frequency is the same as the carrier oscillation for transmission, the output of the BFO 34 is sent to the balanced modulator 22 via buffer amplifiers 26 and 27, if necessary.
- It is injected into the balanced demodulator 23 and finely adjusts its frequency to perform tone control of the transmitted modulated sound. The receiving BFO is usually a crystal oscillator with a fixed frequency, but by inserting a reactance (mainly a capacitor) in parallel or series with the crystal oscillator [by changing its constant, the oscillation frequency can be finely tuned. , it is easy to vary the frequency by several hundred Hz, which is necessary for the purpose of the present invention.

In this example, the receiving BFO is shared with the transmitting carrier oscillator, but the frequency conversion circuit shown in Fig. 1 can also be used directly or multiplied if the transmitting and receiving local oscillation frequencies match or have an integral multiple relationship. Alternatively, it is possible to divide the frequency and share the oscillator.

〔Effect of the invention〕

As described in the claims and summary of the invention,
According to the present invention, it is possible to easily perform low-cutting of the modulated signal by using an existing or additional SSB speech processor circuit. This configuration can be applied to transmitters with modulation formats other than SSB as an independent speech processor and tone control adapter, and can be used in a wide range of applications.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the configuration of the present invention, Fig. 2 is a schematic diagram of an implementation circuit of the invention, Fig. 3 is a block diagram of another implementation circuit of the invention, and Fig. 4 is a block diagram of an SSB speech process. FIG. 5 is an explanatory diagram of the operation of the present invention. l... Speech processor section, 11... Amplitude compressor or amplitude limiter, 12, 25... BPF, 2.3.
...Frequency converter, 22...Balanced modulator, 23
...Balanced demodulator, 24...Carrier oscillator, 34.
...BFO14...Local oscillator.

Claims (3)

[Claims] (1) BP after compressing or limiting the amplitude of the modulated signal
A frequency conversion circuit is provided on the input side and output side of an SSB speech processor circuit that removes harmonic distortion components through F or LPF, and the local oscillation frequency to be injected into the circuit is supplied from the same local oscillator, and the local oscillation frequency By finely adjusting the filter, the relative frequency relationship between the modulated signal and the filter can be changed, thereby making it possible to adjust the degree of attenuation at the low frequency end or high frequency end of the modulation component of the modulated signal. speech processor circuit. (2) The speech processor circuit according to claim 1, wherein the input side frequency conversion circuit is a balanced modulator, and the output side frequency conversion circuit is a balanced demodulator or a product detector. (3) The speech processor circuit according to claims 1 and 2, in which the local oscillator includes a BFO of the receiving section.