SU1378068A1 - Apparatus for displaying and measuring amplitude-phase in modem with multiple phase- or amplitude-phase modulation - Google Patents

Abstract

The invention relates to telecommunications. The purpose of the invention is to reduce the measurement time by simultaneously indicating the vector of amplitude-phase relations both in the modulator and in the detector. The device contains an amplitude-phase meter 1, a modem 5 under test, containing a modulator 6, a coherent signal extraction unit 7 and a multiphase phase detector 8. A mixer 2, a local oscillator 3 and a ring switch 4 are entered into the device. Vector diagram the resulting AFM signal contains all the information about the amplitude-phase relations in the modulator and demodulator. The amplitudes and phases of the resultant vector can simultaneously judge the accuracy of the installation of the necessary phase shifts between the vectors and the magnitude of the parasitic AM. 1 tab., 2 Il. (Oh (L

Description

SAE

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The invention relates to telecommunications and can be used for tuning and operative control of modems with multiple phase (FM) or amplitude base modulation (AFM), designed to transmit information via radio channels.

The purpose of the invention is to reduce the measurement time by simultaneously indicating the vector of amplitude-phase relations both in the modulator and in the detector.

Fig. 1 shows the structures; - the electrical circuit of the device for displaying and measuring amplitude-phase relationships in a modem with multiple FM or AFM; in fig. 2 time diagrams of the device operation using the example of measuring amplitude-phase relations in a modem with dual phase modulation.

A device for displaying and measuring amplitude-phase relationships in a multiple FM or AF modem contains an amplitude-phase meter 1, a mixer 2, an LO 3 and a ring switch 4. Modem 5 under test contains a modulator 6, a coherent signal extraction unit 7 and a multiphase phase detector AT.

The device works as follows.

The output signal of the modulator 6, converted to an intermediate frequency using a mixer 2, and generated as a result of multiplying the multiphase reference signal (from the output of block 7) and the signal of the local oscillator 3 output signal of the multiphase phase detector 8 using (n + 1) -input ring switch 4 is converted into units of an amplitude-phase modulated (AFM) signal containing all information about the amplitude-phase characteristics of the tested blocks of modem 5.

The corresponding AFM signal vector is measured and induced in the amplitude-phase meter 1. In this case, one of the output signals of the modulator 6 is used as a reference signal of the amplitude-phase meter.

In the control mode, the frequency difference between the carrier signals and the local oscillator must satisfy the relation

4f (f whitefish, - frer) аР „, лР„ „,

(one)

0

0

five

0

five

0

five

- the maximum frequency in the spectrum of the modulating signal when transmitting standard information.

Condition (1) is fulfilled so that the beat frequency between the input signal and the local oscillator falls into the demodulator filter band.

The clock frequency of transmission of information in the measurement mode should satisfy the relation

fr Rms, kc / (5-10).

When condition (1) is fulfilled, beat signals are generated at the outputs of the multiphase phase detector 8, the amplitudes and phases of which are determined by the amplitude and phase characteristics of the multiphase phase detector 8 and block 7. Thus, in the switching circuit (Fig. 1) the multiphase phase detector 8 operates in the multiphase frequency converter mode, at the outputs of which, at the expense of a low-pass filter with a Rfnz RMPKS band, the signals of the difference frequency are selected, the amplitudes and phases of which are determined by the amplitude-phase errors of the cycles under study.

At the output of the mixer 2 obraziz-c modulated signal with the same frequency, which makes it possible to compare the phases of all signals supplied to the inputs of the ring switch 4.

Consider the time and vector diagrams of signals using the example of a dual phase modulated modem (DPS).

FIG. 2a shows a DFM signal corresponding to the modulator operation logic shown in the table.

Fig. 2b shows signals corresponding to the quadrature and in-phase outputs of the DFM phase demodulator (shifted relative to each other in the ideal case by f / 2 and by a multiple of a / H / V relative to the demodulator input signal).

The signals depicted in FIG. 2a, b, are applied to the signal inputs of a three-input switch, which are respectively switched by controlling the switch signals. The switching frequency (Fig. 2c) of the master oscillator of the switch should ensure switching of signals at its input at a speed sufficient to perceive the pattern on the indicator screen as continuous:

f 7 lO (n-H), Hz.

The signal in FIG. 2 g is the resulting AFM signal at the switch output. The vector diagram of this signal contains all the information about the amplitude-phase relations in the modulator and demodulator.

From the amplitudes and phases of the resulting vector, it is possible to simultaneously judge the accuracy of the installation of the necessary phase shifts between the vectors and the magnitude of the parasitic AM.

As the modulation rate increases, the accuracy requirements for setting the amplitude-phase relations increase dramatically, since, for example, depending on the magnitude of the phase error, the energy losses in a system with n-fold FM increase by the law

8in 5 (/ n-4)

The display on the meter screen 1 of a single vector containing all information about the amplitude-phase relations in the modem reduces the measurement process of setting or controlling the modem while increasing the resulting accuracy, since separate setting implies a multiple (iterative) procedure for establishing amplitude-phase relations.

The amplitudes and phases of the vectors in real devices are interdependent (especially in the microwave range) and the adjustment of the parameters of the signals observed and regulated in this

moment, leads to the departure of the parameters of the signals at the moment uncontrolled.

Claims (1)

Invention Formula Device for displaying and measuring amplitude-phase relations in a modem with a multiple phase or amplitude-phase module - containing an amplitude-phase meter, the first input of which is the output of the reference signal of the modem being tested, characterized in that, in order to shorten the measurement time by simultaneously indicating vectors of amplitude-phase ratios both in the modulator and in the detector of the modem being tested, the mixer, the local oscillator and the ring switch, the mixer output is connected to the control input of the ring switch, the information inputs of which are the corresponding outputs the detector of the modem being tested, the output of the local oscillator is connected to the first input of the mixer and is the input of the modem being tested, the second input of the mixer is the output of the modulator the modem under test, the output of the ring switch is connected to the second input of the amplitude-phase meter. four - i, I 5 " "Uh + VE Oj I s  / I s / WITH) cm Cha "Si