SU1631731A1 - Single-sideband radio receiver - Google Patents

Abstract

The invention relates to a rational technique. The purpose of the invention is to reduce the level of nonlinear distortion. A single band radio transmitter contains a single sideband shaper 1, limiters 2, 8 and 12, phase detector 3, low pass filter 4, controlled oscillator (UG) 5, frequency converters 6 and 11, amplitude modulator 7, power amplifier 9, synthesizer 10 frequencies , operational amplifier (OU) 13, amplifier 14, direct current, demodulators 15 and 16 and attenuator 17. At the same time filter 4, UG 5, converters 6 and 11, amplitude modulator 7, limiters 8 and 12, amplifier 9, synthesizer 10 and the attenuator 17 form a phase locked loop. The output oscillation of the UG 5 is transferred to a predetermined frequency range, modulated, limited, amplified. Part of the output power is transferred by means of the converter 11 to a low intermediate frequency, at which the single-band signal is divided into phase and amplitude components. The amplitude components of the input and output single-band signals are formed by demodulators 15 and 16. They are compared in the op-amp 13, the resulting signal is fed to an amplitude modulator 7, in which the original single-band signal is restored but shifted along the frequency axis. 3 il. & (L

Description

Phys. 1

The invention relates to radio engineering and can be used in various radio stations.

The aim of the invention is to reduce the level of non-linear distortion.

Figure 1 shows the structural electrical circuit of the single sideband transceiver; in figure 2 (a, b, c) and 3 (a, b, c, d, d) - work diagrams.

Single-band radio transmitter shaper 1 single-sided ignal, first limiter 2, phase detector (PD) 3, low pass filter (LPF) 4, controlled oscillator (UG) 5, second frequency converter 6 clock, amplitude modulator 7, three limiter 8, amplifier 9 power, frequency synthesizer 10, first frequency inverter 11, second limiter 12, operational amplifier (OU) 13, direct current amplifier (DCA) 14, first demodulator 15, second demodulator 16, attenuator 17. The single-band radio transmitter works as follows in a way.

LPF 4, UG 5, second transducer 6, amplitude modulator 7, third limiter 8, amplifier 9, frequency synthesizer 10 first converter 11, second limiter 12, attenuator 17 and phase detector 3 form a phase self-tuning ring. Using the second converter 6, to the second input of which an auxiliary oscillation is received from the second output of the frequency synthesizer 10, the output oscillations of the UG 5 are transferred to a predetermined frequency range, modulated by the amplitude modulator 7, limited by the third limiter 8, amplified in the amplifier 9 A portion of the output power is supplied to the second input of the first converter 11, with which the signal is transferred to a fixed (relatively low) intermediate frequency at which separation of one band signal phase and amplitude components. The phase component through the second limiter 12 is fed to the input of PD 3, the reference signal for which is the phase component of the original single sideband signal formed in the imaging unit 1, and is fed to the input of the PD 3 through the first limiter 2. The amplitude components of the input and output single sideband signals are formed respectively, by the first and second demodulators 15 and 16, they are matched at op-amp 13, which operates in linear mode. The output difference signal of the op-amp 13 is the envelope of the single-band signal and is fed to the control input of the amplitude modulator 7, through the DCA 14 to the second input of the amplifier 9. Figures 2 (a, b, c) present the signals at the outputs, respectively OA 13, the amplitude modulator 7, the third limiter 8, when the single-band radio transmitter forms a two-tone test signal, the amplitude component of which is the envelope of this signal, which

0 Form is a straightened differential frequency sine wave. The difference component is understood to be the frequency, equal to the frequency difference between the two spectral components of the feed (two-tone) signal. The two-tone test signal envelopes are extracted by the first and second demodulators 15 and 16 of the forward path (the second transducer

Q 6) and the inverse transform (first transducer 11). The differential amplified signal at the output of the op-amp 13 (Fig. 2a) is also a straightened sinusoid, which is fed to an amplitude modulator 7, in which amplitude modulation of the input phase-controlled signal, which is the phase component of the single-band signal, enveloping it, those.

0 there is essentially a restoration of the original (unsplit) single-band signal, but shifted along the frequency axis (vnr.26). Fig. 3 shows one period of the envelope of a two-tone single-sided signal at the output of amplifier 9 at different offsets on the grids of the lamps of this stage (Fig. 3, d, e). For comparison, the ideal envelopes are given (also for one period). 4 The least nonlinear distortion amplifier 9 has at offset Ucw, which corresponds to FIG. Above, signal distortions occur at the phase of the envelope, varying within 0 - Qt, and C0t2 - / i | J, i.e. have a zero envelope. Distortions consist in reducing the modulation depth in these zones. Eliminate distortion can be, if the input of the amplifier 9 does not submit

0

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high-frequency (rf) oscillation constant in amplitude, and rf the oscillation modulated by amplitude in the zero region (when the oscillation phase changes from 0 to G3t and (dtg to 0). At the same time, the amplitude of the HF oscillation applied to the input of amplifier 9 should not change within the variation of the envelope phase of COt, - CiHg. This is achieved by limiting the amplitude of the pre-simulated oscillator in the amplitude modulator 7. The limit of the limit (cut-off angle) must correspond to the change in the envelope phase COt, -GJtg. Then the output oscillation of the amplifier 9, obtained by multiplying (modulating) the input preliminary but modulated and limited in amplitude of the rf oscillation (fig. Sv) and the envelope of the single-band signal (fig. Za) supplied when the lamps of the amplifier 9 are shifted to the grids (fig. Za), in shape approaches an undistorted sinusoid and, therefore, there is a decrease in the level of nonlinear distortion.

Claims (1)

Invention Formula A single-band radio transmitter comprising a series-connected common-band signal generator, a first limiter, a phase detector, a low-pass filter and a controlled oscillator, serially connected frequency synthesizer, the first G6 a frequency converter and a second limiter whose output is connected to the second input of the phase detector, a first demodulator that is connected between the output and the input of the first limiter, a second demodulator that is connected between the output and the input of the second limiter, an operational amplifier and an attenuator that is connected between the output a power amplifier and another input of the first frequency converter, while the outputs of the first and second demodulators are connected respectively to the first and second inputs of the operational amplifier, the output of the second limiter is connected to another input of the phase detector-, and the output of the power amplifier is the output of a single-band radio transmitter, characterized in that, in order to reduce the level of non-linear distortion, between the output of the controlled oscillator and The first input of the power amplifier is a serially connected second frequency converter, an amplitude modulator and a third limiter. And a DC amplifier is also inserted, which is connected between the output of the operational amplifier and the second input of the power amplifier, while the second output of the frequency synthesizer is connected to the second input of the second a frequency converter, and the control input of the amplitude modulator is connected to the output of the operational amplifier. a Fm.1 U four five g one .. b S & I wt 0 f C | eg # I about tt ffitt 4 g 4