RU2099729C1 - Noise characteristics meter of superhigh and high-frequency transmitters - Google Patents

Abstract

FIELD: measurement technology, tests of generators, amplifiers, radio communication complexes and radio stations. SUBSTANCE: expansion of amplitude-dynamic range of measurement of phase noises with simultaneous provision for measurement of amplitude noises of transmitters are achieved by insertion of compensation channel of suppression of carrier of transmitter. EFFECT: expanded amplitude-dynamic range of measurement of phase noises. 3 dwg

Description

 The invention relates to measuring equipment and can be used for testing generators, amplifiers, radio complexes and radio stations.

 A number of schemes are known that provide the ability to measure the noise characteristics of transmitters.

 The closest in technical essence to the proposed device is a device for measuring noise and background of radio transmitters according to the copyright certificate N 159885 and an autocorrelation bandpass noise meter in the vicinity of the carrier according to the copyright certificate N 1734052.

 The device for measuring noise and background of radio transmitters according to copyright certificate N 159885, consisting of channels of constant (low-pass filter and switch) and variable (switch and logarithmic amplifier) component, whose signals are alternately fed to the vertical plates of the cathode ray tube. The disadvantage is the low accuracy and limited amplitude-dynamic measurement range.

 The autocorrelation bandpass noise meter in the vicinity of the carrier, according to the copyright certificate N 1734052, allows to increase the accuracy of measurements due to the possibility of using a synchronous detector that provides optimal processing of the noise signal. However, the dynamic range of measurements is thus limited due to the fact that it is impossible to supply high-level signals to the input of the device (diode detector). This device does not allow measurement along with the amplitude noise of the phase noise of the transmitters.

 The aim of the invention is to expand the amplitude-dynamic range of phase noise measurements while providing the ability to measure the amplitude noise of the transmitters.

 This goal is achieved by the fact that in the meter of noise characteristics of microwave and high-frequency transmitters, consisting of a power divider connected in series to a balanced mixer, a narrow-band low-pass filter, UPT, the first ADC and computer, as well as a broad-band low-pass filter and a second ADC, a directional coupler, a delay line, adjustable attenuator, two adjustable phase shifters, low-frequency switch with 3 inputs and one output, amplifier with adjustable transmission coefficient, three bandpass filters, microwave adder, power divider by 3, while the input device The input of the directional coupler is used, the first output of which is connected to the input of the power divider, and the second through the first adjustable phase shifter with a heterodyne input of the balanced mixer, while the first output of the power amplifier through the delay line and the second adjustable phase shifter is connected to the first input of the microwave adder, and the second output power divider through an adjustable attenuator with the second input of the microwave adder, the output of which is the signal input of the balanced mixer, while the output of the balanced mixer is also through With a broadband low-pass filter and an adjustable amplifier, it is fed to the input of a power divider by 3, each of whose outputs is connected through a corresponding band-pass filter to the corresponding input of the low-frequency switch, the output of which through the first ADC is connected to a computer that controls the control inputs of the low-frequency switch and the adjustable amplifier.

 Figure 1 presents the structural diagram of the proposed meter noise characteristics of microwave and low-frequency transmitters.

 The meter of noise characteristics of microwave and low-frequency transmitters consists of a directional coupler 1, a power divider 2, a controlled attenuator 3, a first controlled phase shifter 4, a delay line 5, a microwave adder 6, a second controlled phase shifter 7, a balance mixer 8, a broadband low-pass filter 9, an amplifier with an adjustable a transmission coefficient of 10, a power divider by 3 11, bandpass filters 12, 13, 14, a low-pass switch for 3 inputs and one output 15, a computer 16, a second ADC 17, a narrow-band low-pass filter 18, a converter 19, a second ADC 20.

 The meter works as follows.

 The s / n ratio is measured in the carrier generation mode from the transmitter.

где A₀-амплитуда генерации несущей передатчика;
m_i-индекс паразитной амплитудной модуляции;
m_k-индекс паразитной угловой модуляции;
ω_o/2π -паразитная девиация частоты;
Ω/π- частота паразитной модуляции;
DW/2π-дискрет частотной отстройки анализируемого спектра;
w₀/2π-частота несущего колебания;
Для простоты восприятия рассмотрим работу устройства для однотонального сигнала, представив выражение (1) следующим образом:
a₂(t) = A₀[1+m_icosΩ_it]cos[ω₀t+m_kcosΩ_kt] (2)
Сигнал данного вида, пройдя направленный ответвитель 1, поступает на вход делителя мощности 2, где делится по мощности пополам (по амплитуде 2).The input signal of the carrier oscillation is described by the expression:

where A ₀ is the generation amplitude of the transmitter carrier;
m _i is the parasitic amplitude modulation index;
m _{k is the} index of spurious angular modulation;
ω _o / 2π-parasitic frequency deviation;
Ω / π is the frequency of spurious modulation;
DW / 2π-discrete frequency tuning of the analyzed spectrum;
w ₀ / 2π-frequency of the carrier oscillation;
For ease of perception, we consider the operation of the device for a single-tone signal, presenting expression (1) as follows:
a ₂ (t) = A ₀ [1 + m _i cosΩ _i t] cos [ω ₀ t + m _k cosΩ _k t] (2)
A signal of this type, passing a directional coupler 1, is fed to the input of a power divider 2, where it is divided in half in power (in amplitude 2).

где K_x-вносимое затухание трактом (линия задержки и фазовращатель);
τ- время задержки, вносимой линией задержки;
v- дополнительный сдвиг фаз, вносимый управляемым фазовращателем.The signal at the first input of the microwave adder is described by the expression:

where K _{x is the} path attenuation (delay line and phase shifter);
τ is the delay time introduced by the delay line;
v is an additional phase shift introduced by the controlled phase shifter.

K_x-затухание тракта (регулируемый аттенюатор) подбирается равным предыдущему тракту.At the second input of the microwave adder, the signal has the form:

K _x - path attenuation (adjustable attenuator) is selected equal to the previous path.

The value of the phase shift ω ₀ τ + Φ = π characterizes the antiphase of the two described two described paths; antiphase is provided by an adjustable phase shifter.

Учитывая, что m_i< 1, Ωτ/2 < 1, ω_qτ < 1 и пренебрегая членами второго порядка малости сигнала на входе балансного смесителя можно представить в виде:

Сигнал на гетеродинном входе балансного смесителя, прошедший второй управляемый фазовращатель, можно описать выражением:
a₇(t) = C₀(1+m_icosΩ_it)sin[ω₀t+m_kcosΩ_kt] (7)
После перемножения сигналов (6) и (7) в балансном смесителе и выделения разностной частоты результирующий сигнал можно представить

или для линейного участка характеристики:

Обычно ω_q/2π в области СВЧ и ВЧ составляет десятки или сотни кГц, а τ выбирается от 0,1 до 0,01 мкс.In this case, the output of the microwave adder signal is described by the expression:

Given that m _i <1, Ωτ / 2 <1, ω _q τ <1 and neglecting the terms of the second order of smallness of the signal at the input of the balanced mixer can be represented as:

The signal at the heterodyne input of the balanced mixer, passing the second controlled phase shifter, can be described by the expression:
a ₇ (t) = C ₀ (1 + m _i cosΩ _i t) sin [ω ₀ t + m _k cosΩ _k t] (7)
After multiplying the signals (6) and (7) in a balanced mixer and extracting the difference frequency, the resulting signal can be represented

or for the linear portion of the characteristic:

Typically, ω _q / 2π in the microwave and high frequency regions is tens or hundreds of kHz, and τ is selected from 0.1 to 0.01 μs.

 From the expression (8) it can be seen that the circuit described above plays the role of a frequency detector with an increased slope of the discriminatory characteristic.

раз (рис. 2,3), где ω₀/2π -частотная точка испытательного сигнала; ω₁/2π частотная точка первого нуля дискриминационной характеристики.The steepness of the frequency detector response depends on A ₀ , K _x, and t. For 0.1 μs delays, the damping coefficient of the delay line is 5–6 dB, and the steepness in the linear part of the characteristic grows in

times (Fig. 2,3), where ω ₀ / 2π is the frequency point of the test signal; ω ₁ / 2π is the frequency point of the first zero of the discriminatory characteristic.

For example, at τ 0.1 μs, K _x = 6 dB, w ₀ / 2π 1 GHz, the slope of the characteristic increases by 40 dB. In this case, a signal with a level of several tens of watts can be supplied to the input of the circuit, which does not interfere with the normal operation of the balanced mixer, since the level of the signal supplied to the signal input is less than 1 mW, and to the local oscillator up to 10 mW, the attenuation of the noise component is K _x times (attenuation coefficient of the delay line).

 Next, the signal (9) is amplified and passes through one of the bandpass filters (depending on the analyzed frequency band) and through the switch goes to the ADC, where it is converted to digital form.

According to the adopted implementation, the computer calculates the frequency spectrum using the inverse Fourier transform. The calculated values of ω _q / 2π at the corresponding frequencies Ω _k / 2π are assigned to ω ₀ / 2π and a histogram of the phase noise of the transmitter is constructed in a given frequency range in the vicinity of the carrier.

 When measuring amplitude noise, the balanced mixer operates in the amplitude detector mode, in-phase signals are applied to both inputs (phase shift is controlled by two controlled channel phase shifters). To measure the signal level, a constant-component channel is used, consisting of a narrow-band low-pass filter, a converter, and an analog-to-digital converter. The level of the carrier wave, relative to which the measured values of the noise components are normalized, is recorded in the computer memory.

Claims (1)

 A meter of noise characteristics of microwave and high-frequency transmitters, consisting of a power divider connected in series to a balanced mixer, a narrow-band low-pass filter, a direct current amplifier, the first analog-to-digital converter and an electronic computer, and also a wide-band low-pass filter and a second analog-to-digital converter characterized in that a directional coupler, a delay line, an adjustable attenuator, two adjustable phase shifters are inserted, neither 3-way switch with three inputs and one output, an amplifier with an adjustable transmission coefficient, three band-pass filters, an microwave combiner, a power divider by three, while the meter input is a directional coupler input, the first output of which is connected to the input of the power divider, and the second through the first adjustable a phase shifter with a heterodyne input of a balanced mixer, the first output of the power divider through the delay line and the second adjustable phase shifter is connected to the first input of the microwave a matrator, and the second output of the power divider through an adjustable attenuator with the second input of the microwave adder, the output of which is connected to the signal input of the balanced mixer, the output of the balanced mixer through a series-connected broadband low-pass filter and an adjustable amplifier connected to the input of the power divider into three, each of which outputs through the corresponding band-pass filter is connected to the corresponding input of the low-frequency switch, the output of which through the first analog-to-digital converter The index is connected to an electronic computer, the outputs of which are connected to the control inputs of a low-frequency switch and an adjustable amplifier.

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