SU1753600A1 - One band compacted signals receiver - Google Patents

Abstract

The use of radio technology in receiving devices The essence of the invention is a receiver of single sideband companions containing a linear receiving path 1, a sideband filter 2 amplifier 3 with automatic gain control, an expander 4, a coherent detector 5, a pilot bandpass filter 6, a frequency detector 7 and an exponential converter 8 Sideband filter 2 contains in-phase channel 9, quadrature, channel 10, local oscillator 11 and adder 12 Each of channels 9, 10 contains an input mixer 13, a notch filter 14 pilot signal, 15 low-pass filter and output mixer 16 Purpose — reduction of non-linear distortions with increasing noise immunity — achieved in the pre-detector expansion of a signal with a certain performance of the sideband filter and connecting a band-pass pilot filter to the output of the input mixer 13 of the common-mode channel 9 2 or 15 With tw in

Description

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This invention relates to a single-band radio and wireline communication.

Known receivers single band compand AM signals.

The closest to the technical essence of the invention is a receiver, which contains serially connected linear receiving path and sideband filter, serially connected amplifier with automatic gain control and expander, serially connected bandpass filter filter, frequency detector and exponential converter The output of which is connected to a control expander, as well as a coherent detector.

The main disadvantage of the prototype is the relatively high level of non-linear distortion of its output signal, a mirror image. The first is determined by the fact that the non-linear operation (expansion) is subjected to a broadband signal (voice), and the second is not sufficiently complete suppression of the mirror noise by the sideband filter. Therefore, the noise immunity of reception will be low.

The aim of the invention is to reduce non-linear distortion — with increasing noise immunity,

The goal is achieved by the fact that the receiver contains a serially connected linear receive path and a sideband filter, a serially connected amplifier with automatic gain control and an expander, a serially connected bandpass filter filter, a frequency detector and a potential converter, the output of which is connected to the expander input, as well as a coherent detector, the output of the sideband filter is connected to the amplifier input with automatic gain control, the output of the expander The adapter is connected to the input of the coherent detector, the sideband filter is made in the form of phase and quadrature channels, the inputs of which are connected, and each channel is made in the form of serially connected input mixer, rejector filter of the pilot signal, low-pass filter and output mixer The other inputs of the mixers are the heterodyne input of the channel, the adder, whose inputs are connected to the outputs of the output channel mixers, and the local oscillator with a signal frequency equal to the average frequency of the sideband filter, the output and vadraturny oscillator output connected to the local oscillator phase and quadrature inputs of canals of, respectively, the input

The band-pass filter pilot is connected to the common-mode channel input mixer output.

FIG. Figure 1 shows the structural and electrical circuit of the receiver; in fig. 2 - spectra of signals explaining his work.

The receiver contains a linear receiving path 1, a sideband filter 2, an amplifier 3 with AGC, an expander 4, a coherent detector 5. Block 2 includes a series-connected pilot-band filter 6, a frequency detector 7, an exponential converter 8, in-phase 9 and quadrature 10 channels, each of which consists of a series-connected signal multiplier 13, a pilot notch filter 14, a low-pass filter 15, an output multiplier (mixer) 16 signals, an adder 12, one input of which is connected to the output of block 9, the other - to the output unit 10, a local oscillator 11 with phase 90 °, which in-phase output is connected to the hf the input of the input mixer 13 block 9, and quadrature - to the H. the input of the mixer 13 of the block 10, the output of the block 1 is connected with n.ch. the inputs of the blocks 13, the output of the block 13 of the in-phase channel is connected to the input of the block 6, the output of the block 8 is connected to one input of the expander 4, and the output of the adder 12 is connected to the other input through block 3, h.ch. the inputs of the blocks 16 are connected to the VC. the inputs of blocks 13 of their channels.

The receiver works as follows.

The input signal of a single sideband, for example, the lower one, consists of a single sideband compressed signal and a single sideband signal formed by the FM oscillation, carrying the envelope

UBx (t) - p (t) +

+ KUcos urt - Qjt + mcos # (t), where m is the FM index;

i / (t) is the envelope phase;

K 1 is a constant.

These single band signals are formed on a single carrier, and their spectra are shown in FIG. 2a, the mirror disturbance shown in the suppressed side (upper) band is also shown there. Both the signal and the interference are filtered, amplified and transferred to the intermediate frequency in the linear receiving path 1, and then fed to one input of the mixers 13 of the two channels 9, 10. The oscillation of the local oscillator 11 is fed to the second input of the block 13 of the channel 9 directly, and to the second the input of block 13 of channel 10 is shifted in phase by 90 ° (in quadrature), the oscillation frequency of the local oscillator is selected

equal to the average frequency of the compressed single-band information signal, i.e. f0 fnp - 0.5 (Pmax + Pmin) fnp -1526 Hz. As a result, at the output of each mixer 13 there will be a speech signal, the frequency band of which is broken at its average frequency PCp fnp - f about 1526 Hz and folded in half, occupying the frequency band from 0 to 1250 Hz, i.e. 2 times the smaller band, plus the mirror noise, which is frequency-separated from the speech signal by 2Rmin 600 Hz. This FM waveform is between the speech signal and the mirror noise, as shown in FIG. 26, the average frequency of which is 1325 Hz, and not 2850 Hz, but a band of 120 Hz. All this is part of the lower sideband at the output of the mixers 13. The upper sideband is the input signal at the frequency fnp + fo 2fnP, which is easily eliminated by the simplest filter and is therefore not shown in FIG. 26, Notch filters 14 of both channels exclude FM oscillation and, therefore, only voice signal and a mirror disturbance are fed to the inputs of the LPF 15. This selection of the conversion frequency in blocks 13 makes it possible to minimize the steepness of the decay characteristic of the low-pass filter, which is about 2 dB by one percent of the frequency change, and its passband, which allows you to completely filter out the mirror noise. Therefore, in FIG. 2b shows only the signal at the output of the low-pass filter 15 of channel 9, and the signal at the output of the low-pass filter 15 of channel 10 is shown in fig 2d. The phases of the halves of the strips in fig. 2c are the same (zero), and in FIG. 2g - antiphase (-90 °, + 90 °). From the output of the low-pass filter 15, the signals are fed to the H.H. inputs of the output mixers. 16 They are included in the H. inputs of blocks 13 of their channels 9 and 10, respectively. The output spectrum of block 16 of channel 9 is shown in FIG. 2d, and the output signal of block 16 of channel 10 in fig 2e. These are two-band signals. Since the input n.ch. Since the signals are at the minimum frequency of PMin 0, the sidebands in FIG. 2d and 2e merge with each other in these figures and the phases of the side bands are shown. In the adder 12, the spectra of the signals from the blocks 16 are added together to form an undistorted upper sideband on the carrier fH fo Pep. as shown in FIG. 2y. By subtracting from the signal of block 16 of channel 9 the signal of block 16 of channel 10, the lower sideband on the carrier fo + Pep is obtained. The signal from the output of the adder 12 after amplification and level adjustment in block 3 is shown at one input of the expander 4. The second input of the signal is supplied from the output of the mixer 13 of channel 9 through the successively connected filter 6 of the pilot signal, frequency detector 7, exponential converter 8. The output of block 7 is logarithm

the envelope because it was logarithmized at the transmitting side. The exponential transducer 8 eliminates this logarithm and an undistorted envelope arrives at the input of the expander 4. So,

At the first input of the expander a single-band information signal takes place, which is narrow-band (its band is much less than the average frequency), then the harmonics are n.ph. components of the input spectrum

during expansion (non-linear conversion) do not fall into the frequency band of the expander output signal. This minimizes the level of non-linear distortion. Single-band signal with reconstructed envelope U (t) U (t) cos ohm + pn (t) from the output of block 4 is fed to one input of the multiplier coherent detector 5 Its second input (not shown) oscillates the reference frequency Uo (t)

 and cos um. By multiplying these signals and filtering, the output of block 5 yields a modulating signal with a reconstructed envelope, having minimal nonlinear distortions at

no mirror interference.

The technical and economic effect of the invention is to minimize non-linear distortion and eliminate the mirror noise in the output signal, which increases

communication immunity

Claims (1)

Claims of the Invention A single-band companion signal receiver comprising a series-connected linear receive path and a sideband fltr, an amplifier connected in series with an automatic gain control and an expander connected in series a pilot filter, a frequency detector and an exponential converter, the output of which is connected to an expander control input, as well as a coherent detector, characterized in that reducing nonlinear distortion with increased noise immunity, the output of the sideband filter is connected to the amplifier input with automatic gain control, the expander output is connected to the input of a coherent detector, the sideband filter is made in the form of in-phase and quadrature channels, the inputs of which are connected, and each of the channels is designed as serially connected input mixer, notch filter filter, low pass filter and output mixer; the other inputs of the mixers are heterodyne in Odom channel adder whose inputs are connected to outputs of the mixers output channels, and the local oscillator signal with frequency equal to the center frequency of the sideband filter, the output and the quadrature outputs of the local oscillator are connected to the heterodyne inputs of the in-phase and quadrature channels, respectively, while the input of the band-pass filter of the pilot signal is connected to the output of the input mixer of the in-phase channel. t / M ЈL OBP Erk P fo f $ 7Ji /) ftf fa + F / nin five ff -I / fo f yo W Erk interference: f e C ± I ± (no. fo f Fsiao0 - & f sfiffjff 180