RU1774281C - Spectrum analyzer - Google Patents

Abstract

The invention relates to a radio metering technique and can be used in devices with which it is possible to observe on a screen of a cathode ray tube (CRT) a spectrum of pulse signals under investigation. The purpose of the invention is to increase the noise immunity and resolution is achieved by introducing a filter 16, a quadratic detector 17 and a key 18. The spectrum analyzer also contains an input unit 1, a calibrator 2, a sweep generator 3, a sweep generator 4, a mixer 5, an intermediate frequency amplifier 6 , quadratic detector 7, frequency detector 8, differentiation unit 9, valve 10, matching unit 11, DC amplifier 12, key 13, and CRT 14. 5 of FIG.

Description

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The invention relates to radio-measuring technology and can be used in devices with which you can observe on the screen of a cathode ray tube (CRT) the spectrum of the studied signals

An object of the present invention is to increase noise immunity and resolution.

Figure 1 shows a block diagram of a device; Fig. 2 is a frequency diagram explaining the formation of additional reception channels; Figs. 3-5 are timing diagrams explaining the operation of the device.

The spectrum analyzer contains an input unit 1, a calibrator 2, a surge driver 3, i an oscillating frequency operator 4, a mixer 5, the second input of which is connected to the output of a calibrator 2, an intermediate frequency amplifier 6, a quadratic detector 7, a frequency detector 8, a differentiation unit 9 , valve 10, coincidence unit 11, the second input of which is connected through the quadratic detector 7 to the output of an intermediate frequency amplifier 6, a constant current amplifier 12, a key 13, a cathode ray tube (CRT) 14, the horizontal deflecting plates of which are connected s with the first output of the 3 sweep generator. The third input of the mixer 5 through the oscillating frequency generator 4 is connected to the second output of the sweep generator 3. A multiplier 15 is connected to the output of the input unit 1, the second input of which is connected to the output. An intermediate frequency amplifier G, a bandpass filter 16, a quadratic detector 17, a key 18, the second input of which is connected to the output of a quadratic detector 7, and an amplifier

12 direct current, the output of which is connected to the second input of the key 13. The spectrum analyzer operates as follows.

The specified frequency range Df is viewed using a sweep generator 3, which periodically changes the frequency of the oscillating frequency generator 4 according to a sawtooth law. At the same time, the sweep generator 3 forms a horizontal sweep of the CRT 14, which is used as the frequency axis. The keys

13 and 18 in the initial state are always closed.

A pulse signal is received

Uc (t) Uc cos (2 fct + pc), 0 t g and, where Uc, fc. , ty - amplitude, carrier frequency, initial phase and signal duration.

0

5

0

5

0

5

0

5

at.

- rate of change

0

5

from the output of the input unit 1, it enters the first input of the mixer 5, the second input of which is supplied with frequency labels from the output of the calibrator 2, and the voltage of the oscillating frequency generator 4 is supplied to the third input

Ur (t) UrCos (2 7Tfr t -f-yryi t2),

About t Tn

where Ur, fr, pr Tn is the amplitude, initial frequency, initial phase and generator voltage repetition period; Df Affl Tn Tn generator frequency;

Dtd - frequency deviation.

At the output of the mixer 5, voltages of combination frequencies are generated:

fd fr + Y11 fnp + / 1 1,

fc2 2fr + Yl t fc,

where the first index denotes the channel through which the signal is received, the second index denotes the harmonic number of the generator frequency involved in the conversion of the carrier frequency of the received signal

2fr, uh is the second harmonic of the generator frequency and its rate of change (fi 2 y {).

The tuning frequencies fHi, W and the passband D f i, D f2 of the amplifier 5 and the bandpass filter 16 are respectively selected as follows:

fH2 fr, A fc 2fnp

fHi fnp, Afi 2fnp.

However, only the voltage with frequency fci falls into the passband D f-i of the intermediate frequency amplifier 5

Unpi (t) Unp cos (2 rfnp t + y t2 + + pnp), 0 t ty

Unp - KiUcUr,

where Ki is the transfer coefficient of the mixer; fnp fr fc - intermediate frequency;

(fhp (fir - (pc.

This voltage is a frequency converted linear frequency modulated signal (LFM). The voltage Unp (t) from the output of the intermediate frequency amplifier 5 is supplied to the second input of the multiplier 15, the first input of which receives the received signal Uc (t) from the output of the input unit 1. The voltage is generated at the output of the multiplier 15

Ui (t) Ui cos (2jrfrt + ray t2 4+ pr), 0 t Tn,

where Ui have K2 Uc Unp j

"2 - transmission coefficient of the multiplier:

which is extracted by a band-pass filter 16. is detected by a quadratic detector 17 and is fed to the control input of the key 18, opening it.

The voltage Unp (t) (Fig. 4a) from the output of the intermediate frequency amplifier 5 simultaneously enters the inputs of the quadratic 7 and frequency 8 detectors. The quadratic detector 7 extracts the pulse envelope (Fig. 4a), which is supplied to the first input of the coincidence unit 11. From the output of the frequency detector 8, a video signal (Fig. 4d), the shape of which corresponds to the law of variation of the pulse frequency fci (Fig. 46), is input to the differentiation unit 9, the output signal of which (Fig. 4e) is supplied to the input of the valve 10. The valve 10 passes only positive impulses. The output pulse (Fig. 4e) of the valve 10 is supplied to the second input of the matching unit 11. Since the voltages (Figs. 4c, e) applied to the two inputs of the coincidence unit 11 occupy the same interval on the time axis, the coincidence unit 11 (Fig. 4g) enters the control input of the key 13, opening it. In this case, the components whose frequency lies in the passband Afi of the intermediate-frequency amplifier 5 are amplified and, after being detected in the quadratic detector 7 and amplified in the amplifier 12, are supplied through the public keys 18 and 13 to the vertically deflecting plates of the CRT 14, on the screen of which my image of the spectrum of the received signal. The operation of the spectrum analyzer described above corresponds to the case of receiving pulsed signals along the main channel at a frequency fc (FIG. 3a).

If a false signal (interference) is received on the mirror channel at the frequency fa (Fig. 36)

Ua (t) Uz cos (2 rz t + rz), 0 t so that in mixer 5 it is converted to the voltages of the following frequencies:

fs1 fa-fr--} 1 t t, fs2 2fr + Y2 t - f3.

However, only the voltage with frequency fai falls into the passband Afi of the intermediate frequency amplifier 5

Unpi (t) Unpi cos (2, Tfnpt +

 ), 0 t GI

where Unpi -r- Ki Uz Ur,

fnp fa fr - intermediate frequency j vip1 fb - fi

The voltage Unpi (t) from the output of the intermediate frequency amplifier 5 is supplied to the second input of the multiplier 15, the first input of which receives the received false signal (interference) U - (t) from the output of the input unit 1. The voltage is generated at PYOCHR

U2 (t) - U cog, (2 l-frt .v) i t

-I f,). About t GI

where U2 is K2 U3 Unpi,

which is extracted by a band-pass filter 6. is detected by a quadratic detector 17 and is fed to the control input of the key 18,

0 opening it. The voltage Unpi (t) (Fig. Be) from the output of the intermediate frequency amplifier 5 is simultaneously supplied to the inputs of the quadratic 7 and frequency 8 detectors. Quadratic detector 7 extracts the envelope

5 of the signal (Fig. Bb) which is supplied to the first input of the coincidence unit 11. From the output of the frequency detector 8, a video signal (Fig. 5g), the shape of which corresponds to the law of frequency change f3i (Fig. 56), is fed to the input of the differentiation unit 9, the output signal of which (Fig. 2d) is not passed by the valve 10. The key 13 does not open and a false signal (interference) received on the mirror channel at the FC frequency; 5 is suppressed. If a false signal (interference) is received on the first combinational channel at a frequency fKi (Fig. Sv),

UK1 (T) Yk1 COS (2 JTk1 t +),

Oh t ti

0 then in the mixer 5 it is converted to the voltages of the following frequencies fn tk1 - fr-yi t; fi2 2fr + yat - fKi fnp + yat. However, only a voltage with a frequency of 5 fi2 falls into the passband Afi of the intermediate frequency amplifier 5

Unp2 Unp2 COS (2 JT fnpt + ЯУ2Т.2 + +), 0 t Ги

0 where Unp2-g- Ki UK1 Ur;

fnp 2fr - tk1 - intermediate frequency, - (Pnp2 - fV - pk1.

The voltage Unp2 (t) from the output of the intermediate frequency amplifier 5 is fed to the second input of the multiplier 15, the first bypass of which receives the received spurious signal (interference) UK1 (t) from the output of the input unit 1. At the output of the multiplier 15, the voltage 0U3 (t) U3 cos (4, -r frt + l-} t2 +

+). About t TI

where U3-g- K2 UK1 Unp2,

which does not fall into the passband Af2 of the band-pass filter 16, the Key 18 does not open and the spurious signal (interference) received on the first combinational channel at a frequency fKi is suppressed. For a similar reason, false is suppressed.

the signal (interference) received on the second combinational channel at a frequent 1k2 (Fig. Zg).

Claims (1)

The claims Spectrum analyzer by ed. St. Mp 1187095, characterized in that, with the purpose of increasing noise immunity and resolution, introduced into it K, p fni) i f / 7D ffff fr fr 2fr 7 " fr jf bfl fr 2f }1 a series-pass multiplier, a second quadratic detector, and a second switch, the second input of which is connected to the output of the first quadric detector and the output is connected to the input of a DC amplifier, the second input is connected to the output of the intermediate frequency amplifier, and the input of the multiplier is connected to the output input block. f rffp fnp Zfr fa / 8a fm 2f, ftl f3 fr fc T -fr ; fc F 2 t 2f. / f, 2 fi f uf fiif