RU-1841399-C - Spectrum optimization device

Abstract

FIELD: special radio engineering. SUBSTANCE: invention relates to special radio engineering and can be used in radar, radio communication, as well as in special areas of radio engineering, where syrdine (autogeterodine) reception and frequency shift of the retransmitted signal in a wide range of input frequencies are widely used. The claimed device is based on a traveling wave tube and contains a sawtooth oscillator connected to the modulating input of the traveling wave tube. The output of the mixer of the superheterodyne receiver is connected in parallel to the filters of the first and second harmonics of the modulating voltage, with opposite-polarity detectors at their outputs. The outputs of the opposite-polarity detectors are connected through a summator and a modulator to the control input of the sawtooth oscillator, and the output of the sawtooth oscillator is connected to an amplitude meter. EFFECT: technical result of the invention is the creation of a small-sized device that automatically maintains the constancy of the output spectrum during syrdine conversion (frequency shift) in a wide range of input frequencies, using the same device to approximately determine the carrier frequency of the input signal. 1 cl, 2 dwg

Inventors

• GUSEV YURIJ STEPANOVICH
• Kucheryavenko Andrej Vladimirovich
• Mlechin Viktor Volfovich

Assignees

• Акционерное общество "Центральный научно-исследовательский радиотехнический институт имени академика А.И. Берга"

Dates

Publication Date

20260506

Application Date

19710126

Claims (1)

1. A frequency conversion device for an autoheterodyne receiver, implemented on a traveling wave tube and containing a sawtooth oscillation generator connected to the modulating input of the traveling wave tube, characterized in that, for the purpose of stabilizing the spectrum of the modulated signal and measuring the carrier frequency, filters of the first and second harmonics of the modulating voltage with heteropolar detectors at their outputs are connected in parallel to the output of the mixer of the autoheterodyne receiver, the outputs of the heteropolar detectors are connected through a summer and a modulator to the control input of the sawtooth oscillation generator, to the output of which an amplitude meter is connected.

Description

The invention relates to special radio engineering and can be used in radar, radio communications, as well as in special areas of radio engineering where serodyne (autoheterodyne) reception and frequency shift of the retransmitted signal in a wide range of input frequencies are widely used. The main task in frequency shifting is to maintain a constant ratio of the powers of the spectral components of the output signal, multiples of the modulation frequency (signal magnitude) in a wide range of input frequencies, and, as a special case, to suppress the remainder of the carrier and side harmonics, which is currently carried out manually. The aim of the present invention is to create a small-sized device that automatically maintains the constancy of the output spectrum during serial conversion (frequency shift) over a wide range of input frequencies, using the same device for approximately determining the carrier frequency of the input signal. It is known [L1] that in TWT the steepness of the phase characteristic is directly proportional to the input signal frequency, and for ideal transfer it is necessary to maintain a phase modulation index of 2π during phase modulation with sawtooth oscillations. Therefore, with a constant amplitude of sawtooth oscillations and a change in the input signal frequency, the phase modulation index will change, as a result of which the spectrum of the shifted signal will change [L2]. Fig. 1 shows the dependence of the carrier residue, the first (useful) and second harmonics of the spectrum when changing the phase modulation index. The graph shows that at lower input signal frequencies (modulation index less than 2π), the carrier frequency residual increases sharply while the second harmonic slowly increases. As the input signal frequency increases, the second harmonic in the spectrum increases more sharply. At a modulation index of 2π, the carrier frequency residual and the second harmonic are equal to zero. A device is proposed that maintains the modulation index constant with changes in the input signal frequency by automatically varying the sawtooth oscillation amplitude. The initial modulation index value can be selected at any value. The error signal of the automatic control circuit is formed by bipolar detection and subsequent summation of equal powers from the first and second harmonics of the modulation frequency in the output spectrum. When the modulation index deviates from the selected value in either direction, the error signal changes sign, and its magnitude is directly proportional to the deviation of the modulation index from the selected value. The error signal controls the amplitude of the sawtooth oscillations in the generator of these oscillations, which is part of the automatic control circuit, until the voltage at the adder output is zero. The phase modulation index is selected based on the required ratio of the first to the second harmonic. Fig. 1 shows two cases of the ratio of the specified harmonics and their corresponding modulation indices. Fig. 2 shows a block diagram of the device. Elements that distinguish the device from prototypes are outlined with a dotted line. The signal arriving at the TWT input (I) is phase-modulated by sawtooth oscillations with a frequency F VLF , supplied from the sawtooth oscillator (2). The input frequency signal as a result of modulation at the output of the TWT changes and has the form: Where - residual power on the carrier; , - amplitudes of the corresponding harmonics. After the mixer (3) the component with amplitude enters the first harmonic filter (4), and the component with amplitude - into the second harmonic filter (5). The specified signals, after detection in the bipolar detectors (6), (7), are summed in the adder (8) in the required ratio. In this case, the detected voltage of the first harmonic is divided in the voltage divider by such a number as to ensure the specified value of the phase modulation index and the corresponding spectrum. The difference signal from the adder output is amplified in the DC amplifier (10) and fed to the modulator (11), from the output of which the voltage is fed to the sawtooth oscillator to change the amplitude of the oscillations it generates. Thus, if the second harmonic exceeds the divided first harmonic, a negative voltage proportional to the difference between these harmonics after equalization is removed from the adder output. This voltage, after amplification, reduces the amplitude of the sawtooth oscillations (the phase modulation index) until the second harmonic decreases and equals the divided amplitude of the first harmonic. In the case of a decrease in the second harmonic relative to the divided value of the first harmonic, a positive voltage is supplied from the adder output, increasing the amplitude of the sawtooth oscillations until the increasing value of the second harmonic and the divided amplitude of the first harmonic become equal and the modulation index be