SU1415197A1 - Frequency marker former - Google Patents

Abstract

The invention relates to a radio measuring technique and serves to improve the accuracy of the formation of frequency marks. The shaper contains a mixer I, filters 2 and 5 low frequencies, a generator of 3 harmonics and a filter 6 high frequencies. The introduction of key 4, detector 7, and the formation of new functional connections exclude false labels from reaching the output of the imager. 2 Il.

Description

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The invention relates to a radio measuring technique and can be used in instruments for measuring frequency characteristics.

The aim of the invention is to improve the accuracy of the formation of frequency I tags.

I FIG. 1 is a block diagram of a frequency tag former; in fig. 2 - timing diagrams that show the work of the driver.

Shaper frequency labels (Fig. 1) contains a mixer 1, the first low-pass filter 2 (LPF), 3 harmonic generator, key 4, the second low pass filter I 5 (LPF), the upper filter 6 I frequency (HPF) and the detector 7

I The first input of the mixer 1 is connected to the I with the output of the generator 3 harmonics, and; the second input is the input of the frequency marker generator, the output of the mixer-body 1 is connected to the input of the low-pass filter 2, the output of which is connected to the signal input of the key 4 and the input of the high-pass filter 6, the output of which through the detector 7 is connected to the control input of the key 4, output which is connected to the input of the low-pass filter 5, the output of which is the output of the frequency tag generator.

The shaper works as follows.

The first input of the mixer I is a sequence of short pulses c. repetition frequency f from the harmonic generator 3, and to its second input an input signal from the sweeping frequency generator with a linearly varying frequency is applied (Fig. 2a)

The transformation equation in mixer 1 relating the input frequency to the fundamental frequency of the harmonic generator 3 is

f, i mf +,

(one)

where f is the frequency of the converted

signal;

then - the harmonic number of the input

signal;

n is the harmonic number of the signal of the harmonic generator 3; f - the main frequency of the generator

ra 3.

The results of the stroboscopic conversion of the mixer 1 are enough - with the first low-pass filter with bandwidth

 i.e. No components with higher frequencies are passed through LPF 2.

 "

The signal component at the output of the first # 2, used to form frequency marks, has a frequency f, (Fig. 2b), defined by the formula (1) with m 1:

+ f ± nf.

(2)

At the points where f nf (n is an integer), the frequency f is zero. Since mixer I is a non-linear element, the higher harmonics of the input signal are involved in the conversion, so for m 2 (Fig. 2c)

fj. ± 2f ± nf, m 3 (Fig. 2d)

fa ± 3f ±.

(3)

(BUT)

From consideration of FIG. 2b-d, the nature of the occurrence of false marks on the output of the device is visible, they are formed by zero beats, when the frequencies f, f are less than F, and the frequency f, F, and the correct marks (Fig. 2e, solid lines) form, when f, -. F and frequencies f and} are also close to zero.

The signal from the output of the low-pass filter 2 is supplied via switch 4 to the second low-pass filter 5, having

bandwidth F 2 -, Key control 4 is carried out using a chain of series-connected HPF 6 and detector 7. HPF 6. has a cutoff frequency equal to F. Key 4 is open when there is no signal at the HPF 6 output. In this case, the voltage of the tag in the form of zero beats from the LPF 2 passes to the output of the second low-pass filter 5 (Fig. 2e). At the time of the occurrence of zero beats of false labels on the output of LPF 2, key 4 is closed, since at the output of the HPF 6 there is a high-frequency signal, which envelopes the detector 7 in the form of a constant voltage and keeps the key 4 in a closed state, thus , false labels do not enter the driver's output.

Claims (1)

The invention of the frequency label shaper -containing serially connected