RU2007885C1 - Device for reception of signals having linear frequency modulation - Google Patents

Abstract

FIELD: radio engineering. SUBSTANCE: device has receiver 1, two mixers 2 and 3, two heterodynes 4 and 5, two multipliers 6 and 21, narrow-band filter 7, four wide-band filters 8, 9, 10 and 22, three compressing filters 11, 16 and 25, three frequency detectors 12, 17 and 26, three differentiating units 13, 18, and 27, three surge injectors 14, 19, and 28, three solving units 15, 20 and 29, phase inverter 23, adder 24. EFFECT: increased range of working frequencies due to use of first and second mirrored receiving channels. 2 dwg

Description

 The invention relates to radio engineering and can be used in radio communication systems and radio telemetry, where broadband signals with linear frequency modulation (LFM) are widely used.

 Of the known devices, the closest to the proposed device is for receiving broadband signals with linear frequency modulation [1].

 The specified device provides suppression of the mirror channel of the reception.

 However, from the point of view of expanding the operating frequency range, it is advisable not to suppress the mirror receiving channel, but to use it.

 The aim of the invention is to expand the frequency range of the device.

 The goal is achieved by the fact that the first multiplier is connected in series to the device, to the inputs of which the second inputs of the first and second local oscillators are connected, a narrow-band filter, the second multiplier, to the second input of which the output of the second broad-band filter, the third broad-band filter, adder, and the second frequency detector are connected, a second differentiating unit, a second pulse shaper and a second decision unit, a phase inverter, the input and output of which are connected respectively to the output of the first broadband fil three, which is connected to the input of the first frequency detector, and with the second input of the adder, the third compression filter, the input and output of which are connected respectively to the output of the adder and the second input of the second decision unit, and the fourth broadband filter is connected in series, the output of the second is connected to the input of the second a mixer, a third frequency detector, a third differentiating block, a third pulse shaper, and a third decision block, to the second input of which an output is connected, a second compression filter, the input of which is connected inen with the fourth broadband filter output.

 In FIG. 1 shows a block diagram of the proposed device; in FIG. 2 is a frequency diagram illustrating the formation of additional receive channels; in FIG. 3 is a timing diagram explaining the operation of the device.

 A device for receiving broadband signals with linear frequency modulation comprises a receiver 1, first and second mixers 2 and 3, first and second local oscillators 4 and 5, a first multiplier 6, a narrow-band filter 7, a first, second and third broad-band filters 8, 9 and 10, the first compression filter 11, the first frequency detector 12, the first differentiating unit 13, the first pulse generator 14, the first decoding block 15, the second compression filter 16, the second frequency detector 17, the second differentiating block 18, the second pulse former 19, the second decisive block 20, the second multiplier 21, the fourth broadband filter 22, the bass reflex 23, the adder 24, the third compression filter 25, the third frequency detector 26, the third differentiating block 27, the third pulse shaper 28 and the third decision block 29. Moreover, the output of the receiver 1 is connected in series to a mixer 2, the second input of which is connected to the first output of the local oscillator 4, a broadband filter 8, a frequency detector 12, a differentiating unit 13, a pulse shaper 14 and a deciding unit 15, the second input of which is connected through a compression filter 11 to the course of the broadband filter 8. A mixer 3 is connected in series to the output of the receiver 1, the second input of which is connected to the first output of the local oscillator 5, a broadband filter 10, a frequency detector 17, a differentiating unit 18, a pulse shaper 19 and a deciding unit 20, the second input of which is through a compression filter 16 is connected to the output of the broadband filter 10. A multiplier 6 is connected in series to the second output of the local oscillator 4, the second input of which is connected to the second output of the local oscillator 5, a narrow-band filter 7, the multiplier 21, the second in the path of which through a broadband filter 9 is connected to the output of the mixer 3, a broadband filter 22, an adder 24, a second input of which through a phase inverter 23 is connected to the output of a broadband filter 8, a frequency detector 26, a differentiating unit 27, a pulse shaper 28 and a deciding unit 29, the second input which through a compression filter 25 is connected to the output of the adder 24.

 The device operates as follows.

- скорость изменения частоты внутри импульса;
Δf_g - девиация частоты.From the output of the receiver 1 to the first inputs of the mixers 2 and 3 receives the received signal with linear frequency modulation (LFM) U _o (t) = V _o ˙cos (2πf _o t + πγt ² + φ _o ),
0≅t≅T _o , where V _o , f _o , φ _o , T _o - amplitude, initial frequency, initial phase and signal duration;
γ =

- rate of change of frequency inside the pulse;
Δf _g - frequency deviation.

Voltage is applied to the second inputs of the mixers 2 and 3 from the first outputs of the local oscillators 4 and 5
U _g1 (t) = V _g1 ˙cos (2πf _g1 t + φ _g1 ),
U _r2 (t) = V _r2 ˙cos (2πf _{r2 r2} t + φ) where V _r1, V _r2, f _r1, f _r2, φ _r1, φ _r2 - amplitude, frequency and initial phase of oscillators stresses.

Moreover, the frequencies f _g1 and f _{g2 of the} local oscillators 4 and 5 are spaced apart by a double value of the intermediate frequency (see Fig. 2)
f _r2 - f _r1 = 2f and _straight symmetrical selected frequency f _o fundamental channel
f _o - f _g1 = f _g2 -f _o = f _ave . This circumstance leads to the appearance of a second mirror channel at a frequency f _g2 .

_H1 tuning frequency f and the bandwidth Δ f ₁ 9 broadband filter chosen from the expressions (see Figure 3a..) F _H1 = f _ave; Δf ₁ = 2f _ave .

The tuning frequency f _n2 and the passband Δ f _{2 of the} broadband filters 8, 10 and 22 are selected from the expressions
f _2n = 3f _straight; Δf ₂ = 2f _ave .

f_пр. В смесителях 2 и 3 принимаемый ЛЧМ сигнал преобразуется в напряжения следующих частот (см. фиг. 3а):
f_o1= f_o+γt-f_г1= f_пр+γt;
f_o2= f_г2-f_o-γt= f_пр-γt. где первый индекс обозначает канал, по которому принимается сигнал:
второй индекс обозначает номер гетеродина, участвующего в преобразовании несущей частоты принимаемого сигнала. Однако только напряжение с частотой f_o2 попадает в полосу пропускания Δ f₁широкополосного фильтра 9:
U_пр1(t)= V_пр1˙cos(2πf_прt-
-πγt²+φ_пр1); 0≅t≅T_o где U

=

K₁U_o·U

,
К₁ - коэффициент передачи смесителей;
f_пр= f_г2-f_o - промежуточная частота;
φ_пр1= φ_г2-f_o. Это напряжение поступает на первый вход перемножителя 21. Напряжение U_г1(t) и U_г2(t) с вторых выходов гетеродинов 4 и 5 одновременно поступают на два входа перемножителя 6, на выходе которого образуется напряжение U_г(t)= V_г˙cos(4πf_прt+φ_г), где U_г=

K₂·U

U

,
К₂ - коэффициент передачи перемножителя;
2f_пр= f_г2-f_г1;
φ_г= φ_г2-φ_г1, которое выделяется узкополосным фильтром 7 и подается на второй вход перемножителя 21, на выходе которого образуется напряжение
U₁(t)= V₁˙cos(6πf_прt-
-πγt²+φ₁);
0≅t≅T_o, где U₁=

K₂·U_пр·U_г,
φ₁= φ_пр1+φ_г, которое выделяется широкополосным фильтром 22 и подается на первый вход сумматора 24. Так как в полосу пропускания Δ f₂ широкополосного фильтра 8 напряжение не попадает, то на втором входе сумматора 24 напряжение отсутствует. Напряжение U₁(t) с выхода широкополосного фильтра 22 через сумматор 24 одновременно поступает на входы сжимающего фильтра 25 и частотного детектора 26. На выходе частотного детектора 26 образуется напряжение соответствующей формы, которое подается на вход дифференцирующего блока 27. На выходе последнего образуются прямоугольные импульсы. На выходе формирователя 28 импульсов образуются короткие импульсы в моменты времени, соответствующие моментам смены знака наклона функции частотной модуляции ЛЧМ-сигнала. Эти импульсы вместе с информационными импульсами с выхода сжимающего фильтра 25 поступают на соответствующий вход решающего блока 29, обеспечивая тактовую синхронизацию при приеме решения.The tuning frequency f _n and the passband Δ f of the narrow-band filter 7 are selected from the expressions
f _n = 2f _straight; Δf =

f _pr In mixers 2 and 3, the received LFM signal is converted to the voltages of the following frequencies (see Fig. 3a):
_{f o1 = f o + γt-} f _r1 = f _ave + γt;
f _o2 = f _r2 -f _o -γt = f _ave -γt. where the first index indicates the channel through which the signal is received:
the second index denotes the number of the local oscillator involved in the conversion of the carrier frequency of the received signal. However, only the voltage with a frequency f _o2 falls into the passband Δ f _{1 of the} broadband filter 9:
U _pr1 (t) = V _pr1 ˙cos (2πf _pr t-
-πγt ² + φ _pr1 ); 0≅t≅T _o where U

=

K ₁ U _o · U

,
To ₁ - gear ratio of the mixers;
f _CR = f _g2 -f _o - intermediate frequency;
_pr1 cp = φ _r2 -f _o. This voltage is supplied to the first input of the multiplier 21. The voltage U _g1 (t) and U _g2 (t) from the second outputs of the local oscillators 4 and 5 are simultaneously fed to the two inputs of the multiplier 6, the output of which produces the voltage U _g (t) = V _g ˙ cos (4πf _pr t + φ _g ), where U _g =

K ₂ · U

U

,
K ₂ is the transmission coefficient of the multiplier;
2f _ave = f _r2 -f _r1;
φ _g = φ _g2 -φ _g1 , which is allocated by a narrow-band filter 7 and is fed to the second input of the multiplier 21, the output of which is generated
U ₁ (t) = V ₁ ˙cos (6πf _pr t
-πγt ² + φ ₁ );
0≅t≅T _o , where U ₁ =

K ₂ · U _pr · U _g ,
φ ₁ = φ _pr1 + φ _g , which is allocated by the broadband filter 22 and supplied to the first input of the adder 24. Since the voltage does not enter the passband Δ f _{2 of the} broadband filter 8, there is no voltage at the second input of the adder 24. The voltage U ₁ (t) from the output of the broadband filter 22 through the adder 24 simultaneously enters the inputs of the compression filter 25 and the frequency detector 26. At the output of the frequency detector 26, a voltage of the corresponding form is generated, which is fed to the input of the differentiating unit 27. At the output of the latter, rectangular pulses are generated . At the output of the pulse shaper 28, short pulses are formed at time instants corresponding to moments of changing the sign of the slope of the frequency modulation function of the chirp signal. These pulses together with information pulses from the output of the compression filter 25 are fed to the corresponding input of the decision unit 29, providing clock synchronization when making a decision.

The described operation of the device corresponds to the case of receiving LFM signals on the main channel at a frequency f _o .

If the chirp signal is received by the first image channel at frequency f _P1, U _P1 (t) = V _P1 ˙cos (2πf _P1 t + πγt ² + φ _P1); 0≅t≅T _P1, the mixers 2 and 3 is converted into a voltage following frequencies (see Figure 3b..):
f ₁₁ = f _r1 -f _P1 -γt = f _ave -γt;
f ₁₂ = f _r2 -f _P1 -γt = 3f _straight -γt.

=

K₁·U

U

,
φ_пр2= φ_г2-φ_з1.
Это напряжение через сжимающий фильтр 16 поступает на информационный вход решающего блока 20 и через последовательно включенные частотный детектор 17, дифференцирующий блок 18 и формирователь 19 импульсов на вход синхронизации решающего блока 20.However, only a voltage with a frequency f ₁₂ misses the bandwidth Δ f ₂ broadband filter 10: U _np2 (t) = V _np2 ˙cos (6πf _pr t-πγt ²⁺
+ φ _pr2 ); 0≅t≅T _P1, where U

=

K ₁ · U

U

,
_WP2 cp = φ -φ _{r2 P1.}
This voltage is supplied through the compression filter 16 to the information input of the deciding unit 20 and through the series-connected frequency detector 17, the differentiating unit 18 and the pulse shaper 19 to the synchronization input of the deciding unit 20.

K₁·U

U

U

=

K₁·U

U

φ_пр3= φ_з2-φ_г2;
φ_пр4= φ_з2-φ_г1. Напряжение U_пр3(t) с выхода широкополосного фильтра 9 поступает на первый вход перемножителя 21, на второй вход которого подается напряжение U_г(t) с выхода узкополосного фильтра 7. На выходе перемножителя 21 образуется напряжение
U₂(t)= V₂˙cos(6πf_пр+πγt²+
+φ₂); 0≅t≅T_з2, где U₂ =

K₂·U

U_г;
φ₂= φ_пр3+φ_г, которое выделяется широкополосным фильтром 22 и подается на первый вход сумматора 24.If the LFM signal is received via the second mirror channel at a frequency f _s2 , U _s2 (t) = V _s2 ˙cos (6πf _s2 t + πγt ² +
+ φ _z2 ); 0≅t≅T _P1, the mixers 2 and 3 is converted into a voltage following frequencies (see Figure 3c..):
f ₂₂ = f _s2 + γt-f _r2 = f _ave + γt;
f ₂₁ = f _s2 + γt-f _r1 = 3f _pr + γt. These voltages fall into the passband Δf ₁ and Δf _{2 of the} broadband filters 9 and 8, respectively:
_PR3 U (t) = V _PR3 cos (2πf _ave t + πγt ²⁺
+ φ _pr3 ); U _pr4 (t) = V _pr4 ˙cos (6πf _pr t + πγt ² +
+ φ _pr4 ); 0≅t≅T _s2, where U

K ₁ · U

U

U

=

K ₁ · U

U

φ _pr3 = φ _z2 -φ _g2 ;
φ _pr4 = φ _s2 -φ _g1 . The voltage U _pr3 (t) from the output of the broadband filter 9 is supplied to the first input of the multiplier 21, the second input of which is supplied with the voltage U _g (t) from the output of the narrow-band filter 7. A voltage is generated at the output of the multiplier 21
U ₂ (t) = V ₂ ˙cos (6πf _pr + πγt ²⁺
+ φ ₂ ); 0≅t≅T _s2, where U ₂ =

K ₂ · U

U _g ;
φ ₂ = φ _pr3 + φ _g , which is allocated by the broadband filter 22 and fed to the first input of the adder 24.

The voltage U _CR4 (t) from the output of the broadband filter 8 through the compression filter 11 is supplied to the information input of the decision block 15 and through the series-connected frequency detector 12, the differentiating block 13 and the pulse shaper 14 to the synchronization input of the decision block 15. The voltage U _CR4 (t ) output from wideband filter 8 simultaneously input to phase inverter 23, the output of which is formed _np5 voltage U (t) = -V _WP4 ˙cos (6πf _ave t + πγt ²⁺
+ φ _CR4 ), which is supplied to the second input of the adder 24. The _voltages U ₂ (t) and U _CR5 (t) supplied to the two inputs of the adder 24 are compensated at its output.

If the LFM signals simultaneously arrive through the main channel at a frequency f _o , through the first mirror channel at a frequency f _s1 and through a second mirror channel at a frequency f _s2 , then in mixers 2 and 3 they are converted to voltages of the following frequencies:
_{f o1 = f o + γt-} f _r1 = f _ave + γt;
f _o2 = f _r2 -f _o -γt = f _ave -γt;
f ₁₁ = f _r1 -f _P1 -γt = f _ave -γt;
f ₁₂ = f _r2 -f _P1 -γt = 3f _straight -γt;
f ₂₂ = f _s2 + γt-f _r2 = f _ave + γt;
f ₂₁ = f _s2 + γt-f _r1 = 3f _pr + γt, which fall within the bandwidth Δf ₁ and Δf ₂ broadband filters 9, 8 and 10. In this case, the work involved in all blocks of the device.

 Thus, the proposed device in comparison with the prototype provides an extension of the range of operating frequencies by 3 times due to the use of the first and second mirror receiving channels. (56) 1. USSR author's certificate N 1109936, cl. H 04 L 27/00, 1983.

Claims (1)

 DEVICE FOR RECEIVING WIDE-BAND SIGNALS WITH LINEAR FREQUENCY MODULATION, containing a receiver, the output of which is connected to the first inputs of the first and second mixers, the second inputs and outputs of which are connected respectively to the first outputs of the first and second local oscillators and to the inputs of the first and second wide-band filters, connected in series to the first and second broadband filters a frequency detector, a first differentiating block, a first pulse shaper and a deciding block, to the second input of which the output of the first compression filter is connected, and t also a second compression filter, characterized in that, in order to expand the frequency range of the device, a first multiplier is connected in series, to the inputs of which are connected the second outputs of the first and second local oscillators, a narrow-band filter, a second multiplier, to the second input of which the output of the second wide-band filter is connected, third broadband filter, adder, second frequency detector, second differentiating unit, second pulse former and second decision unit, phase inverter, input and output of which respectively, connected to the output of the first broadband filter, which is connected to the input of the first frequency detector, and to the second input of the adder, a third compression filter, the input and output of which are connected respectively to the output of the adder and the second input of the second decision unit, and the fourth broadband filter is connected in series, to the input of which the output of the second mixer, the third frequency detector, the third differentiating unit, the third pulse shaper and the third decision unit are connected, to the second input in which the output of the second compression filter is connected, the input of which is connected to the output of the fourth broadband filter.

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