SU1744789A1 - Method of transmission of stereo signal and device to implement it - Google Patents

Abstract

This invention relates to a stereo broadcasting technique. The goal is to reduce nonlinear distortion. The device J ii contains the readout of the MCH 2, the first spectrum converter 3, the intermediate frequency generator 4, the second spectrum converter 5, the carrier frequency generator 6. The goal is achieved in that the stereo signal is transmitted using amplitude modulation, the law of which is such that the spectrum of the RF signal lies below the carrier frequency and has a width equal to twice the width of the spectrum of the original signal, i.e. same as monaural broadcasting. The reduction in nonlinear distortion is due to the fact that in the low-frequency region the spectrum also coincides with the spectrum of the original audio signal. 2 sec. item f-ly, 2 ill.

Description

figure 1

This invention relates to a stereo broadcasting technique.

The purpose of the invention is to reduce nonlinear distortion.

FIG. 1 shows a block diagram of a stereo transmission device; in fig. 2 is a schematic diagram of a spectrum converter.

The device for transmitting a stereo signal contains a subtractor 1, an adder 2, a first spectrum converter 3, an intermediate frequency generator 4, a second spectrum converter 5, a carrier frequency generator 6.

Spectrum converter 3 and 5 contain an adder 7, a constant sensor 8, a subtractor 9, a high-pass filter 10, a quad 11, an amplifier 12, a delay element 13, an integrator 14, an amplitude modulator 15, a phase modulator 16.

The essence of the method is as follows.

The signal Q (ft), S (t)) has the property that, in the frequency range 0 Q, the spectrum of its envelope coincides with the spectrum of the signal S (t), as well as the fact that the spectrum of the signal Q (a), S (t)) lies below the frequency (a and has a width equal to the Omax frequency Q0 is chosen to be 2 Ocex. and the spectrum of the signal L + R + Q (Q0, LR) lies, therefore, in the spectrum from 0 to

2 Dix.

Since the maximum frequency of the signal is 2, then the signal Q (o, L + R + Q (Q0, L-R)) has a spectrum width equal to 2 Olax. those. the same as for monophonic amplitude modulation. Elimination of nonlinear distortions is ensured by the fact that the spectrum of the stereo signal envelope coincides with the spectrum of the audio signal L + R.

The device that implements the method works as follows.

The first input of the subtractor 1 receives the signal of the left stereo channel L, and the second input receives the signal of the right stereo channel R. The output signal of the subtractor 1 L-R is fed to the first input of the first converter 3 of the spectrum. At its second input, a generator 4 signal with frequency Q0 is applied. Frequency Q0 of generator 4 is chosen equal to 2 Omamax. Therefore, the signal Q (2 Oamax L-R) at the output of the first converter 3 of the spectrum has a spectrum lying in the interval интерв2 2 Oemax, and the envelope spectrum of this signal coincides with the spectrum of the signal in the frequency interval 0 Gfc. Output Q (2 Tszmaks L-R) of the first

converter, spectrum 3 is fed to the first input of adder 2, the second and third inputs of which are fed to the left and right stereo channels L and R. The output

the signal of the adder 2 L + R + Q (2 Omamax, L-R), having the specified spectrum, is fed to the first input of the second converter 5 of the spectrum, to the second input of which the signal of the generator 6 is fed at a frequency ai. At the output of the second spectrum converter 5, a signal is received, the envelope spectrum of which in the 0 0 Omax sound frequency interval coincides with the L + R sound signal spectrum, which makes it compatible with mono AM radio receivers, and in the Ommax 2 frequency range, Max coincides with the spectrum of the signal Q (2 Tszhaks, LR).

The first and second converters 3 and 5 of the spectrum operate as follows.

0 The input signal S (t) is fed to the first input of the adder 7, the second input of which receives the voltage of the sensor 8. The magnitude of the constant component, and in the converters 3 and 5 is selected different. In the converter 3 a 2 ... 2.4 Zmax, and in the converter 5 a 1 ... 1.2 Zmax, where Zmax is the maximum amplitude of the input signal S (t) of the converter 3, 5. Signal a + S (t) from the output of the adder 7 enters

0 the first input of the subtractor 9, the second input of which receives the output signal of the subtractor 9 through sequentially connected by the quad 11 with the quadratic transfer function, the amplifier 12 and

5 filter 10. The cut-off frequency of the filter 10 is chosen equal to the maximum frequency O iax of the signal spectrum S (t). Therefore, in the frequency range a, ЈWc, the spectrum of the signal a + K (t) at the output of the subtractor 9 coincides with the spectrum of the signal a + S (t) at its first input.

From the output of the quadrant 11, the signal a2 + M (t) is fed to the input of the integrator 14, which transforms the signal in a manner

five

Well

QM-jL / i ..

The output signal of the integrator 14 is supplied to the control input of the phase modulator 16, the signal input of which receives the signal of the carrier frequency co. The output signal of the phase modulator 16 is fed to the signal input of the amplitude 5 modulator 15, the control input of which is fed to the signal a + K (t) from the output of the subtractor 9 via the delay line 13 necessary to compensate for the delay of the signal in the integrator 14. Thus, the output signal

amplitude modulator 15 is determined by the expression

"..M-b to- - f -.

Claims (2)

1. A stereo signal transmission method in which the input mono signals are added and transmitted by means of an amplitude-modulated signal, characterized in that, in order to reduce non-linear distortions, simultaneously with the addition of the input mono signals, the resulting mono-signal signals are subtracted, the resulting difference signal modulate by law V Q (), where QO - under the carrier frequency ;. L and R - input mono signals;  Q (QO. L-R) is a function that solves the transcendental system of equations / Q (a.sM) - ((a "-ak o.-fr + y -Stf -dx, Baaad + hell: u & k (+ “O 2jf“ “(+ K (i) j ". where a is a constant component; Oiax is the maximum component of the signal frequency S (t). o) - carrier frequency. the received modulated signal is added to the sum of the input mono signals and the result of this addition is modulated by law U Q (u), L + R-t-V). 2. An apparatus for transmitting a stereo signal, comprising a carrier frequency generator, a subcarrier frequency generator, an adder and a first spectrum converter, characterized in that a second spectrum converter and a subtractor, with the first input of the first and second spectrum converters connected to the output from the subcarrier frequency generator and the carrier frequency generator, respectively the first and second inputs of the subtractor are connected respectively to the first and second inputs of the adder, the third input of which is connected to the output of the first spectrum converter, and the output of the adder is connected with the second input of the second spectrum converter, and the output of the subtractor is connected to the second input of the first spectrum converter., FIG. 2 Editor I. Casard Tehred M. Morgenthal Order 2203 Circulation: Subscription VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, 4/5 Raushsk nab. FM I with os (at) Proofreader E. Lonchakova