RU2007733C1 - Device for spectrum analyzer - Google Patents

Abstract

FIELD: radio instruments. SUBSTANCE: device has input unit 1, calibrator 2, swept circuit 3, sweep frequency generator 4, mixer 5, intermediate frequency amplifier 6, first squarer detector 7, frequency detector 8, differentiating unit 9, gate 10, matching unit 11, direct current amplifier 12, first switch 13, monitoring device (CRT) 14, multiplier 15, first band-pass filter 16, second squarer detector 17, second switch 18, second band-pass filter 19, phase inverter 20, adder 21. EFFECT: increased functional capabilities. 5 dwg

Description

 The invention relates to radio-measuring equipment 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.

 The purpose of the invention is to increase the noise immunity and resolution of the device.

 In FIG. 1 shows a structural diagram of the proposed analyzer; in FIG. 2 is a frequency diagram explaining the formation of additional receiving channels; in FIG. 3-5 are timing diagrams explaining the operation of the analyzer.

 The spectrum analyzer contains an input unit 1, a calibrator 2, a sweep generator 3, a sweep frequency generator 3, a mixer 5, an intermediate frequency amplifier 6, a first quadratic detector 7, a frequency detector 8, a differentiation unit 9, a valve 10, a matching unit 11, a constant amplifier 12 current, the first key 13, the recording device in the form of a CRT 14, the multiplier 15, the first bandpass filter 16, the second quadratic detector 17, the second key 18, the second bandpass filter 19, the phase inverter 20 and the adder 21, and b lock 1, filter 19, bass reflex 20, adder 21, the second input of which is connected to the output of block 1, the mixer 5, the second input of which is connected to the output of the calibrator 2, and the third input - through the generator 4 - with the first output of the generator 3, amplifier 6, detector 8, block 9, valve 10, block 11, the second input of which through the detector 7 is connected to the output of the amplifier 6, a key 13 and vertically deflecting plates of a CRT 14, horizontally deflecting plates of which are connected to the second output of the generator 3. To the output of the adder 21 are connected in series multiplier 15, the second input which is connected to the output of amplifier 6, a filter 16, a quadratic detector 17, a key 18, the second input of which is connected to the output of the detector 7, and an amplifier 12, the output of which is connected to the second input of the key 13.

 The spectrum analyzer operates as follows.

Viewing a given frequency range D is carried out using a sweep generator 3, which periodically with a period T _p changes the frequency of the oscillating frequency generator 4 according to a sawtooth law. At the same time, the generator 3 forms a horizontal scan of the CRT 14, which is used as the frequency axis. Keys 13 and 18 in the initial state are always closed.

Received pulse signal
U _c (t) = U _c cos (2πf _c t + φ _c ), 0≅t≅τ _u , where U _c , f _c , φ _{c and} τ _u are the amplitude, carrier frequency, initial phase, and signal duration, respectively,
from the output of the input unit 1 goes to the input of the band-pass filter 19 and to the first input of the adder 21. The tuning frequency f _{n of the} band _- pass filters 16 and 19 is chosen equal to the intermediate frequency f _pr (f _n = f _pr ), so this signal does not fall into the passband Δf _n bandpass filter 19. There is no voltage at the second input of adder 21.

=

- скорость изменения частоты генератора;
Δ f_g - девиация частоты.Therefore, the received signal from the output of the input unit 1 through the adder 21 is fed to 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 generator 4 is supplied to the third input
u _r (t) = U _r cos (2πf _g t + πγ ₁ t + φ _g ),
0≅t≅T _g , where U _g , f _g , φ _g and T _p are the amplitude, initial frequency, initial phase and the repetition period of the generator voltage, respectively;
γ ₁ =

=

- the rate of change of the frequency of the generator;
Δ f _g is the frequency deviation.

The output of the mixer 5 are formed voltage Raman frequencies
f _c1 = f _g + γ ₁ tf _c = f _ol + γ ₁ t
f _c2 = 2f _g + γ ₂ t -f _c ,
where the first index indicates the channel through which the signal is received; the second index denotes the harmonic number of the local oscillator frequency involved in the conversion of the carrier frequency of the received signal; 2f _g and γ ₂ are the second harmonic of the generator frequency and its rate of change (γ ₂ = 2 γ ₁ ).

The tuning frequency f _n1 and the passband Δ f _{1 of the} intermediate frequency amplifier 5 are selected as follows;
f _H1 = f _ave, Δ f ₁ = 2f _pr.

The tuning frequency f _n2 and the passband Δ f _{2 of the} bandpass filter 16 are selected as follows;
f _H2 = f _g , Δ f ₂ = 2f, _etc.

K₁U_сU_г ;
К - коэффициент передачи смесителя;
f_пр = f_г -f_c - промежуточная частота;
φ_пр= φ_г-φ_с.However, in the passband Δ f _{1 of the} intermediate frequency amplifier 6 only the voltage with a frequency of f _s1
u _pr (t) = U _pr cos (2πf _pr t + πγ ₁ t ² + φ _pr ),
0≅t≅τ _u , where U _pr =

K ₁ U _with U _g ;
K is the transfer coefficient of the mixer;
f _CR = f _g -f _c - intermediate frequency;
φ _CR = φ _g -φ _s .

K₂U_сU_пр ;
К₂ - коэффициент передачи перемножителя, которое выделяется полосовым фильтром 16, детектируется квадратичным детектором 17 и поступает на управляющий вход ключа 18, открывая его.This voltage is a frequency-converted signal with linear frequency modulation. The voltage u _CR (τ) from the output of the intermediate frequency amplifier 6 is supplied to the second input of the multiplier 15, the first input of which receives the received signal u _c (t) from the output of the input unit 1. A voltage is generated at the output of the multiplier 15
u ₁ (t) = U ₁ cos (2πf _g t + πγ ₁ t ² + φ _g ),
0≅t≅τ _u ,, where U ₁ =

K ₂ U _with U _ol ;
To ₂ - the transfer coefficient of the multiplier, which is allocated 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 u _pr (t) (Fig. 4a) from the output of the intermediate frequency amplifier 5 simultaneously arrives at the inputs of the quadratic 7 and frequency 8 detectors. The quadratic detector 7 selects the envelope of the pulse (Fig. 4b), which is fed 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 change of the pulse frequency (Fig. 4b), 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 positive impulses. The output pulse (Fig. 4E) of the valve 10 is supplied to the second input of the coincidence unit 11. Since the voltage (Fig. 4 c, e) supplied to the two inputs of coincidence 11 occupy the same interval on the time axis, the coincidence unit 11 is triggered. The voltage from the output of the coincidence unit 11 (Fig. 4g) is supplied to the control input of the key 13, opening it. In this case, the components whose frequency lies in the passband Δ f _{1 of the} intermediate frequency amplifier 5 are amplified and after detection in the quadratic detector 7 and amplification in the amplifier 12, through the public keys 18 and 13, they arrive at the vertically deflecting plates of the CRT 14, on the screen of which there is a direct image of the spectrum of the received signal.

The described operation of the spectrum analyzer corresponds to the case of receiving pulsed signals along the main channel at a frequency f _c (Fig. 3a).

If a false signal (interference) is received on the mirror channel at a frequency f _s (Fig. 3b)
u _s (t) = U _s cos (2πf _s t + φ _s ),
0≅t≅τ _u ,,
then in the mixer 5 is converted to the voltage of the following frequencies;
f _z1 = f _s -f _g - γ ₁ t = f _ol - γ ₁ t
f _s2 = 2f _g + γ ₂ tt _s .

However, only the voltage with a frequency of t _s1 falls into the passband Δ f _{1 of the} intermediate frequency amplifier 6
u _pr1 (t) = U _pr1 cos (2πf _pr t-πγ ₁ t ² + φ _pr1 ),
0≅t≅τ _u , where U _pr = 1/2 · K ₁ U ₃ U _g ;
f _CR = f _C -t _g - intermediate frequency;
φ _pr1 = φ _s -φ _g .

The voltage u _pr1 (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 _s (t) from the output of the input unit 1.

The output of the multiplier 15 is formed voltage
u ₂ (t) = U ₂ cos (2πf _g t + πγ ₁ t ² + φ _g ),
0≅t≅τ _u ,, where U ₂ = 1/2 · K ₂ U _з U _пр1 ,
which is allocated 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 u _pr1 (t) (Fig. 5a) from the output of the intermediate frequency amplifier 6 is simultaneously supplied to the inputs of the quadratic 7 and frequency 8 detectors. The quadratic detector 7 selects the envelope of the signal (Fig. 5c), which is fed 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 f _s1 (Fig. 5b), is fed to the input of the differentiation unit 9, the output signal of which (Fig. 5e) is not passed by the valve 10. The key 13 does not open and a false signal (interference) received on the mirror channel at a frequency f _s is suppressed.

If a false signal (interference) is received on the first combinational channel at a frequency f _k1 (Fig. 3B)
u _к1 (t) = U _к1 cos (2πf _к1 t + φ _к1 ),
0≅t≅τ _u , then in mixers 5 it is converted to the voltage of the following frequencies:
f ₁₁ = f _k1 -f _g - γ ₁ t
f ₁₂ = 2f _g + γ ₂ tf _k1 = f _ol + γ ₂ t.

However, only voltage with a frequency f ₁₂ falls into the passband Δ f _{1 of the} intermediate frequency amplifier 5
U _pr2 (t) = U _pr2 cos (2πf _pr t + πγ ₂ t ² + φ _pr2 ),
0≅t≅τ _u , where U _pr2 = 1/2 · K ₁ U _k1 U _g ;
f _CR = 2f _g -f _k1 - intermediate frequency;
φ _pr2 = φ _g -φ _k1 .

The voltage U _pr2 (t) from the output of the intermediate frequency amplifier 6 is supplied to the second input of the multiplier 15, the first input of which receives a false signal (interference) U _k1 (t) from the output of the input unit 1. A voltage is generated at the output of the multiplier 15
u ₃ (t) = U ₃ cos (4πf _g t + πγ ₂ t ² + φ _g ),
0≅t≅τ _u , where U ₃ = 1/2 · K ₂ U _k1 U _pr2 , which does not fall into the passband Δ f _{2 of the} band-pass filter 16. Key 18 does not open and the false signal (interference) received by the first Raman channel at a frequency f _k1 is suppressed.

For a similar reason, the false signal (interference) received on the second Raman channel at a frequency f _{k2 is also} suppressed (Fig. 3d).

If a false signal (interference) is received on the direct channel at a frequency f _pr
u (t) = U _n cos (2πf _pr t + φ _pr ),
0≅t≅τ _u , then it is allocated by the band-pass filter 19 and fed to the input of the bass reflex 20. The following false signal (interference) is generated at the output of the latter.
u _n = -U _n cos (2πf _pr t + φ _pr ),
0≅t≅τ _u , which is supplied to the second input of the adder 21, the first input of which gives a false signal (interference) U _n (t). False signals (interference) U _n (t) and U _u (t) received at the two inputs of the adder 21, at its output is compensated. Therefore, a false signal (interference) received on the direct channel is suppressed. (56) Copyright certificate of the USSR N 1774281, cl. G 01 R 23/16, 1990.

Claims (1)

 A SPECTRA ANALYZER containing an input unit, an intermediate frequency amplifier connected in series, a first quadratic detector, a coincidence unit, a key and a registration device, a mixer, a second mixer input connected to the output of the calibrator, and a third input through a sweep generator connected to the first output of the sweep generator, in series connected frequency detector, differentiation unit, valve, output connected to the second input of the coincidence unit, the second input of the recording device is connected to the second a sweep generator, as well as a series-connected multiplier, a first bandpass filter, a second quadratic detector, a second key and a DC amplifier, a second input of the multiplier connected to the output of an intermediate frequency amplifier, a second input of a second key connected to the output of the first quadratic detector, the output of a DC amplifier connected to the second input of the first key, characterized in that, in order to increase the noise immunity and resolution of the device, sequentially introduced Inonii second bandpass filter, a phase inverter and an adder, the second input of which is connected to the output of the input section and the input of the second bandpass filter and the output of the adder is connected to the second inputs of the mixer and multiplier.

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