SU379881A1 - SYNCHRONO-PHASE FILTER - Google Patents

Description

The invention relates to the analysis technique of analysis, in particular, to synchronous phase filters that perform narrowband filtering while simultaneously transferring the resulting spectrum to an arbitrary frequency range.

Synchronous 10 phase filters (SFF) are known, containing two key multiplier circuits controlled by rectangular voltages shifted-and 90 ° using a phase shifter, two low-pass filters connected to the output, m multiplier circuits, secondary unit spectrum conversions, which include two multipliers, each of which is connected to the output of the corresponding low-pass filter and to the harmonic source: apr 1 (frequency synthesizer) directly and through phases and the adder. In order to suppress the influence of odd ga.m. control voltage, the spectrum of the analyzed voltage is transferred to the high-frequency region by means of a primary spectrum conversion connected to the input of the unit. Voltages are needed. For transferring the input voltage spectrum, key management of the multiplication circuit, and for secondary spectrum transfer, are generated by a frequency analyzer. The band-pass of such a synchronous-phase filter is determined by the passband of the low-pass filter, and the tuning frequency is determined by the frequency of the control voltage.

Such a synchronous-phase filter circuit has a high selectivity, ease of adjustment over the frequency range and provides the possibility of the resulting spectrum with an arbitrary center frequency. However, when measuring the Mast frequency, the filter bandwidth remains unchanged, which limits its application in the Spectral Analysis Area and other related areas of technology ;.

The purpose of the invention is to change the filter bandwidth.

This is achieved by including a pulse-width modulator connected to the second output of the synthesizer in the key management circuit of the first multiplier circuits.

This makes it possible to adjust the SFF pass-through band smoothly, according to an arbitrary law, by changing the porosity of the HJHIDOTHO impulses modulated control voltage.

Pa figs. 1 shows the circuit B-proposed synchronous-phase filter; on fi. 2, a-g are the forms of voltages at various points of the device-a.

The synchronous phase filter consists of a block / primary spectrum transform.

2 multiplication key schemes and 3 low-pass filters (LPF), two consecutive odpaisywiunx circuits, (Connecting from one side to the output of the block / and, on the other hand, to two multipliers 4 .block 5 of the secondary npeoiepasoBaHiHH spectrum. adder 6, the Output of which is the output of block 5.

The auxiliary harmonic frequency (/ o) required for the transfer of an aerated bandwidth is fed (to the block / from the synthesizer 7.

The control voltage fi delivers the synthesizer a 7 from the second output through the pulse-width modulator 8 to the control input of the circuit 2 directly and through (the phase shifter through 90 °. The impulse voltage / 2 required for the secondary spectrum transfer, passes va multipliers 4 blocks 5 directly and through the phase shifter 9.

The proposed filter p. Works as follows.

Let the sinusoidal voltage FC (Fig. 2, a) be applied to the input of block 1. On its output the voltage shown in FIG. 2.6. This voltage commutes with the keys of the multipliers (-fig. 2.0). During the time in, the keys are closed at a frequency of / for a period of time they are connected. In the sequence of the circuit formed by the key, the multiplier and the low-pass filter, a current flows, the low-frequency component of which forms at the output of the low-pass filter the frequency beat fi- / o --- c. The magnitude of these beats, in contrast to the Known SPPs, is determined not only by the passband of the .AF LPF, but also by the duty cycle

T

control pulses y -.

and

The bandwidth of the transmission band of the serial key-low-pass filter is equal to. gd

on . To exclude cell discharge 7

during the open state of the key, the output of the key is not shunted by a resistor, yy. E. Key and low pass filter form a serial circuit. Due to this, the transmission coefficient does not depend on ck: importance 7- Thus, in the proposed FFF, increasing or decreasing the duty cycle Y reduces the bandwidth.

The beats at the output of both filters 5, differing by 90 °, are multiplied in two multipliers 4, respectively, sine and cosine

frequencies fz and summed. As a result, at the output of block 5, a monochromatic voltage (Fig. 2, d) of the frequency / 2 + (fi- - / o-FC, the value of which is determined by the degree of coincidence of the frequency is analyzed, is formed.

FC voltages with a frequency of / i - / o- The more the same resultant bandwidth of the low-pass filter A / p, the more accurate this coincidence should be. When acting at the input of a block / voltage, which is a random wideband process, the output voltage of the SPF turns out to be a narrowband random process, the width of the spectrum, which is equal to Afp, and the center frequency / 2-

the voltage depends both on the power spectral density at the fi-fo frequency and on the magnitude of AFp.

Subject invented and

.The synchronous-phase filter containing a primary spectral conversion unit connected via two key multiplication circuits controlled by rectangular voltages shifted by 90 ° using a phase shifter, filters And the second key multiplying circuits with the adder, synthesizer associated with the block primary transformations, as well as with the second key schemes, multiplication, and with one directly, and on the other through a phase shifter, characterized in that, in order to change the filter bandwidth, into the control circuit

the keys of the first multiplier circuits include a pulse-width modulator connected to the second output of the synthesizer.

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