RU2425457C1 - Device of quadrature reception of frequency-manipulated signals - Google Patents

Abstract

FIELD: radio engineering. ^ SUBSTANCE: device of quadrature reception of frequency-manipulated signals comprises a unit of cophased component formation and a unit of quadrature component formation, including serially connected mixers and low-pass filters, a unit of reference signals generation, a voltage divider, a differentiating device, four multipliers, a unit of clock synchronisation, a delay line, a filter amplifier, a phase changer, a phase detector, an adjustable reference signal generator, a low-pass filter of a reference signals unit and the third low-pass filter. ^ EFFECT: simplification without reduction of noise immunity. ^ 6 dwg

Description

FIELD OF THE INVENTION

The invention relates to radio engineering and can be used to receive frequency-manipulated signals with a continuous phase and frequency manipulation index β = 0.5 in systems for transmitting and receiving discrete information.

State of the art

Known devices for receiving frequency-manipulated signals, the principle of which is described in a number of works. For example, in the books of Kantor L.Ya., Dorofeev V.M. Immunity to receiving FM signals. - M .: Communication, 1977; Aeronautical Radio Communication Devices, ed. V.I. Tikhonova. - M .: ed. VVIA them. prof. N.E. Zhukovsky, 1986; Tikhonov V.I. Optimum signal reception. - M .: Radio and communications, 1983; Tikhonov V.I., Kulman N.K. Nonlinear filtering and quasi-coherent signal reception. - M .: Owls. radio, 1975; Murota K., Hirade U. "GMSK - modulation for digital mobile radiotelephony" IEEE Transactions on Communications, vol. com. - 29, 1081, No. 7, p. 1047; as well as in copyright certificates for inventions and patents: Receiver with frequency modulation (Patent No. 1496567, IPC H04B 17/00 of 12.30.77. Author Hiroshi Furano); A device for suppressing threshold noise (Author's certificate No. 270006, IPC Н04В 15/00 of 08/13/70. Authors Yu.A. Afanasyev, V. M. Dorofeev); Demodulator of frequency-manipulated signals (Copyright certificate SU No. 1311585 A, IPC H04L 27/14 of 12.29.84. Author A.S. Garanin. Particleboard); Demodulator of frequency-manipulated signals (Copyright certificate SU No. 1461358 A1, IPC H04L 27/14 of 04/01/85. Author A.S. Garanin. Particleboard); A device for receiving frequency-modulated signals (Patent No. 2179786, IPC H04B 1/10 of 07/13/99. Authors A.M. Karlov, E.V. Volkhonskaya, E.N. Avdeev); The method of quadrature reception of frequency-manipulated signals with minimal shift (Patent No. 2192101 dated 07/13/1999, IPC 7 H04L 27/14. Authors A.M. Karlov, E.V. Volkhonskaya, E.N. Avdeev).

The closest analogue in terms of the set of essential features and the achieved positive effect is a device for quadrature reception of frequency-manipulated signals (prototype), implemented in a technical solution (Patent for invention No. 227474 from 06/19/2003, IPC7 H04L 27/14. Authors AM Karlov, E. V. Volkhonskaya). The device for receiving frequency-manipulated signals described in the prototype is based on the method of quadrature receiving frequency-manipulated signals with differentiation of the obtained quadrature components and their subsequent processing. The functional diagram of this device receiving frequency-manipulated signals is shown in figure 1. and contains:

1 - block forming the in-phase component;

2 - block forming a quadrature component;

3 - block forming the reference signals;

4 - the first differentiating circuit;

5 - the second differentiating circuit;

6 - the first multiplier;

7 - the second multiplier;

8 - the third multiplier;

9 - subtractive device;

10 - block clock synchronization;

11 - delay line;

12 - the fourth multiplier;

13 - strip amplifier;

14 - phase shifter;

15 - phase detector;

16 - the third low-pass filter of the block of reference signals;

17 - tunable reference signal generator;

18 - phase shifter block reference signals;

19 - mixers of the blocks for the formation of in-phase and quadrature components;

20 - low-pass filters of the blocks for the formation of in-phase and quadrature components;

21 - low pass filter.

, модулированный по фазе информационной последовательностью. Причем сигналы полутактовой частоты при «единичной» и «нулевой» посылках отличаются по фазе на 180° и противоположны на интервале длительности информационной посылки T_n. Сигнал полутактовой частоты с выхода перемножителя 8 подается на вход фазового дискриминатора 15, на второй вход которого с блока тактовой синхронизации 10 подается сигнал полутактовой частоты, сдвинутый по фазе на π/2 в фазовращателе 14. С выхода фазового дискриминатора 15 сигнал подается на последовательно соединенные фильтр нижних частот 16 и перестраиваемый генератор 17 для фазовой автоматической подстройки частоты опорных сигналов.The principle of operation of this device is as follows: the input signal is divided into two channels and fed to the in-phase component generating unit 1 and the quadrature component generating unit 2, to which harmonic reference signals are received from the reference signal generating unit 3. The frequency of the reference signals is equal to the average frequency of the received FM signal, and the phase of the reference signal supplied to the quadrature component generating unit 2 differs by π / 2 from the phase of the reference signal supplied to the in-phase component generating unit 1. The phase shift of the reference signals is carried out by the phase shifter 18. In blocks 1 and 2, by multiplying (blocks 19) the input and reference signals and low-pass filtering (blocks 20), two quadrature low-frequency signals are obtained at the output of blocks 1 and 2. Quadrature low-frequency signals are multiplied in the multiplier 8, the output of which produces a signal half-cycle frequency

modulated by phase information sequence. Moreover, the signals of the half-cycle frequency with "single" and "zero" transmissions differ in phase by 180 ° and are opposite in the interval of the duration of the information parcel T _n . The half-cycle frequency signal from the output of the multiplier 8 is fed to the input of the phase discriminator 15, the second input of which from the clock synchronization unit 10 is fed with a half-clock signal shifted in phase by π / 2 in the phase shifter 14. From the output of the phase discriminator 15, the signal is fed to a series-connected filter low frequencies 16 and tunable generator 17 for phase automatic tuning of the frequency of the reference signals.

Clock synchronization is performed in block 10. The output of the multiplier 8 is supplied to the delay line 11 polutaktovoy manipulated frequency signal in phase by a time T _of forming a demodulated signal. The delayed half-clock frequency signal is fed to the first input of the multiplier 12, to the second input of which a demodulated signal generated during the delay time is supplied from the output of the low-pass filter 21. As a result of multiplication, phase shift keying is removed from the delayed signal, and the half-clock frequency signal is fed from the output of the multiplier to a strip amplifier 13. From the output of the strip amplifier, the half-cycle signal is fed to the input of the phase shifter 14.

To demodulate the received FM signal, the signal from the output of the in-phase 1 and quadrature 2 components is fed to the inputs of the differentiating circuits 4 (in-phase component) and 5 (the quadrature component) and to the first inputs of the multipliers 6 and 7. From the output of the differentiating circuits 4 and 5, the differentiated in-phase and quadrature components are fed to the second inputs of multipliers 6 and 7 for multiplying the in-phase and differentiated quadrature components (block 7) and multiplying the quadrature component with differentiation inphase component (block 6). The voltages from the outputs of blocks 6 and 7 are fed to a subtractor 9, the output signal from which is filtered in block 21. The received demanipulated signal is fed to the second input of the multiplier 12 of the clock synchronization block 10 and simultaneously to the output of the quadrature receiving device of frequency-manipulated signals (FM).

The disadvantage of this device is that the circuitry of this device is quite complex.

SUMMARY OF THE INVENTION

The proposed device for quadrature reception of FM signals in technical implementation is simpler in comparison with the prototype.

Functional diagram of the proposed device quadrature reception of frequency-manipulated signals is shown in figure 2 and contains:

1 - block forming the in-phase component;

2 - block forming a quadrature component;

3 - block forming the reference signals;

4 - voltage divider;

5 - differentiating device;

6 - the first multiplier;

7 - the second multiplier;

8 - the third multiplier;

9 - block clock synchronization;

10 - delay line;

11 - the fourth multiplier;

12 - strip amplifier;

13 - phase shifter;

14 - phase detector;

15 is a first low-pass filter block reference signals;

16 - tunable reference signal generator;

17 - phase shifter block of reference signals;

18 - mixers of the blocks for the formation of in-phase and quadrature components;

19 - second low-pass filters of the in-phase and quadrature components;

20 is a third low pass filter.

Timing diagrams explaining the principle of demodulation of the frequency-manipulated signal and the formation of voltage half-cycle frequency of the proposed device are shown in Fig.3.

The input signal can be represented as the sum of the FM signal and narrowband noise.

u _in (t) = A _m cos [ω ₀ t + φ _M (t)] + E (t) cos [ω ₀ t + φ (t)],

where E (t) and φ (t) are the random envelope and phase of the narrow-band noise;

φ _M (t) = ± ω _d t = ± βΩ _M t is the phase change of the signal over a time interval equal to the duration of the transmission T _p ;

ω _d - the frequency deviation of the FM signal;

ω ₀ - the frequency of the carrier oscillation equal to the center frequency of the spectrum of narrow-band noise;

- индекс частотной манипуляции;

- index of frequency manipulation;

Ω _M is the frequency of manipulation.

Let the FM signal be manipulated by the information sequence of voltage pulses shown in Fig. 3, a.

за время длительности посылки Т_п фаза ЧМ сигнала получает приращение на

(фиг.3, b).When receiving frequency-manipulated signals with a minimum shift β = 0.5 and

during the duration of the sending T _{p the} phase of the FM signal is incremented by

(figure 3, b).

The reference signal generation unit generates harmonic oscillations with a frequency equal to the frequency of the FM carrier signal ω ₀ and shifted relative to each other by

;

.

;

.

At the output of the in-phase and quadrature components, after mixing the input signal with the reference signals and filtering out the components with a double frequency of 2ω _0, we obtain low-frequency voltages of the in-phase and quadrature components

,

,

,

,

where E _c (t) = E (t) cosφ (t); E _s (t) = E (t) sinφ (t) are the quadrature noise components.

We introduce the notation E _c = E _c (t) and E _s = E _s (t).

Timing diagrams of changes in terms

и

and

are shown in figure 3, c, d.

At the output of the divider 4, the voltage can be written as

.

.

The timing diagram of the voltage at the output of the divider in the absence of noise is shown in figure 3, e.

At the output of the differentiating device 5, the voltage will be equal to

- производная фазы частотно-манипулированного сигнала;Where

- derivative of the phase of the frequency-manipulated signal;

и

- производные синфазной и квадратурной составляющих узкополосного шума.

and

- derivatives of common-mode and quadrature components of narrow-band noise.

The timing diagram of the voltage at the output of the differentiating device is shown in figure 3, f.

At the output of the multiplier 6 we have a voltage of the form

u ₅ (t) = A _m ² cos ² φ _M (t) + 2A _m E _c cosφ _M (t) + E _c ² .

Figure 3, g shows a timing diagram of the voltage at the output of the multiplier 6.

When multiplying the signals u ₄ (t) and u ₅ (t) at the output of the multiplier 7, we obtain a voltage of the form

The first term in the voltage u ₆ (t) is informational, its timing diagram is shown in figure 3, h. When transmitting “single” and “zero” parcels, it takes the value ± A _m ² ω _d . The remaining terms in the expression u ₆ (t) determine the noise at the output of the device for quadrature reception of FM signals.

To form a half-cycle frequency, the in-phase and quadrature components are multiplied in the third multiplier (block 8) and as a result of multiplication, a voltage is obtained

As can be seen from the timing diagram (figure 3, i), the first term in u ₇ (t) is a half-cycle frequency signal, phase-manipulated information sequence.

₇ voltage u (t) output from the third multiplier 8 is supplied to the input of the delay line 10 for delaying the phase manipulated polutaktovoy signal frequency for the time T _of forming a demodulated signal. The phase-delayed phase-manipulated signal of the half-cycle frequency signal is fed to the first input of the fourth multiplier 11, the second input of which is supplied with a demodulated signal generated during the delay time from the output of the low-pass filter 20. As a result of multiplying the demodulated signal and the delayed phase-shifted signal of the half-cycle frequency in the fourth multiplier 11, phase manipulation information sequence is removed and at the output of the multiplier it turns out tense Ie

17 на второй вход смесителя 19 блока формирования квадратурной составляющей 2.The first term in u ₈ (t) is the generated half-cycle frequency signal (Fig. 3, j). From the output of the fourth multiplier 11, the half-cycle frequency signal is amplified and filtered in a strip amplifier 12, the output of which is fed to the input of the phase shifter 13. From the output of the phase shifter, the filtered half-cycle frequency signal is fed to the second input of the phase discriminator 14 for comparison with the phase-manipulated half-cycle signal. The mismatch signal from the output of the phase discriminator 14 is fed to the input of the low-pass filter of the reference signal block 15, the output of which is allocated a voltage proportional to the deviation in frequency and phase of the oscillation of the adjustable generator of the reference signal 16 from the carrier frequency of the input FM signal. From the output of the tunable generator 16, the signal is supplied to the second input of the mixer 19 of the in-phase component forming unit 1 and through the phase shifter to

17 to the second input of the mixer 19 of the block forming the quadrature component 2.

The noise immunity of the proposed device quadrature reception of frequency-manipulated signals is determined by the ratio of the amplitude of the pulses at the output of the low-pass filter 20 when receiving a "single" and "zero" parcels to the rms value of the noise.

In accordance with the voltage u ₆ (t), the amplitude of the information pulses can be taken equal to u _p = ± A _m ² ω _d . The rms value of the noise will be determined by the noise components in the voltage u ₆ (t)

To assess the noise immunity of the proposed device for quadrature receiving FM signals, we determine the correlation function and the noise energy spectrum at the output of the multiplier 7 and the signal-to-noise ratio at the output of the low-pass filter 20.

For the noise correlation function, we can write

k _w (τ) = 〈u _w (t) u _w (t + τ)〉,

where 〈〉 - angle brackets denote the averaging operation.

As a result of simple but cumbersome transformations for the noise correlation function, we obtain

- дисперсия узкополосного шума; ρ(τ) - коэффициент корреляции квадратурных составляющих шума.Where

- dispersion of narrowband noise; ρ (τ) is the correlation coefficient of the quadrature noise components.

, а также учтены равенстваWhen obtaining the formula for the noise correlation function, it was taken into account that the quadrature components of the input noise E _c (t) and E _s (t) are normal random processes with a correlation function

as well as equalities

;

;

;

;

;

;

,

,

;

.Where

;

.

The energy spectrum of noise can be calculated by the Wiener-Khinchin transformation formula

We assume that the noise at the input of the quadrature FM reception device has a Gaussian spectral density. Then the correlation coefficient of the quadrature components of the input noise will be equal to

.

.

The first and second derivatives of the correlation coefficient of the quadrature noise components are equal, respectively

;

;

.

.

After calculating the Wiener-Khinchin transform on the correlation function of the output noise for the spectral density of the noise, we obtain

.We introduce the signal-to-noise ratio at the input of the quadrature FM reception device as

.

Then the expression for the noise spectral density has the form

We assume that the passband of the amplifier of the intermediate frequency amplifier is selected from the condition

.

.

, нормированную частоту девиации вида

и нормированную частоту манипуляции

. Тогда выражение для спектральной плотности выходного шума имеет видWe introduce a frequency normalized to the passband

normalized frequency of deviation of the species

and normalized frequency of manipulation

. Then the expression for the spectral density of the output noise has the form

спектральной плотности выходного шума

при различных отношениях сигнал/шум a ² и β=0.5 от нормированного к полосе пропускания УПЧ значения частоты.Figure 4 shows graphs of the normalized to the value

output noise spectral density

at various signal-to-noise ratios a ² and β = 0.5 from the frequency value normalized to the passband of the IF amplifier.

спектральная плотность шума имеет квадратичную зависимость от частоты.The graphs show that in the low-frequency region

spectral noise density has a quadratic dependence on frequency.

The expression for the noise spectral power at the output of the proposed device is similar to the obtained expression of the noise energy spectrum for the prototype, therefore, the noise immunity of the proposed device is not inferior to the noise immunity of the claimed prototype.

When determining the noise power at the output of the low-pass filter 20, we assume that it has an ideal amplitude-frequency characteristic with a passband Ω _M. In this case, the noise power at the output can be obtained by integrating S _w (x) within the normalized passband of the low-pass filter x _M.

.Let us introduce the signal power to noise ratio at the input of the quadrature FM reception device, recalculated to the passband Ω _{M of the} low-pass filter 20 as

.

Then, for the ratio of the amplitude of the pulse of the demodulated signal to the rms value of the noise at the output of the proposed device for quadrature reception of FM signals, we obtain

Figure 5 shows graphs of the dependence of the signal-to-noise ratio at the output of the device for quadrature receiving FM signals from the signal-to-noise ratio a _Ω ² at its input at β = 0.5.

It can be seen from the graphs that this dependence is almost linear and does not have pronounced threshold properties, as is the case for a conventional frequency detector.

In the proposed device for receiving FM signals, opposite signals are formed at its output when transmitting a “single” and “zero premises”, and the spectral noise density and noise power does not change. In this case, the probability of error when receiving an elementary parcel will be determined by the formula / 1 /

,

,

- интеграл вероятности.Where

is the probability integral.

The probability of an error in the reception of an elementary packet with optimal coherent reception of orthogonal frequency-manipulated signals (β = 0.5) is determined by the formula / 1 /

.

.

The results of calculating the probability of erroneous reception of elementary premises at the optimal coherent reception of FM signals (curve 2) and the proposed device for quadrature reception of FM signals (curve 1) are shown in Fig.6.

It can be seen from the above dependences that, with a signal-to-noise ratio at the input a _Ω 〉 5 dB, the proposed device for quadrature reception of FM signals provides noise immunity higher than with optimal coherent reception. This is explained, firstly, by the fact that in the proposed device the orthogonal FM signals at its input are converted into opposite ones at its output, and secondly, by differentiating the ratios of the quadrature components, the spectral noise density at low frequencies has a parabolic dependence, and the noise power at the output of the low-pass filter (block 20) is negligible.

List of sources used

1. V.I. Tikhonov. Optimum signal reception. - M .: Radio and communications, 1983, 320 p.

2. V.I. Tikhonov, N.K. Kulman. Nonlinear filtering and quasi-coherent signal reception. - M .: Owls. Radio, 1975, 704 pp.

3. L.Ya. Kantor, V.M. Dorofeev. Immunity to receiving FM signals. - M .: Communication, 1977, 336 p.

4. Aviation and radio communication devices. Ed. V.I. Tikhonova. - Ed. VVIA them. prof. N.E. Zhukovsky, 1986, 442 p.

5. V.I. Tikhonov. Statistical radio engineering. - M .: Owls. radio, 1966, 678 p.

6. I.S. Gradstein, I.M. Ryzhik. Tables of integrals, sums, series and products. - M .: Nauka, 1971, 1108 p.

Claims (1)

A quadrature device for receiving frequency-manipulated signals, comprising a common-mode component generating unit and a quadrature component generating unit, including series-connected mixers and low-pass filters, the first inputs of the mixers being connected together and being the input of the quadrature receiving device for frequency-manipulated signals, and the low-pass filter outputs connected to the inputs of the third multiplier, one output of which is connected to the first input of the phase detector of the block is formed a reference signal, including a series-connected phase detector, a first low-pass filter, an adjustable reference signal generator and a phase shifter, the output of which is connected to the second input of the mixer of the quadrature component generation unit, and the output of the adjustable reference signal generator is connected to the second input of the mixer of the in-phase component formation unit, the second output of the third multiplier is connected to the input of the series-connected delay line, the fourth multiplier, strip the amplifier and the phase shifter of the clock synchronization unit, the output of which is connected to the second input of the phase detector of the reference signal generating unit, the second input of the fourth multiplier of the clock synchronization unit is connected to the output of the third low-pass filter, which is the output of the quadrature reception device of the frequency-manipulated signals, characterized in that the output the low-pass filter of the common-mode component forming unit is connected to the first input of the voltage divider and to the first and second input of the first trans multiplier, and the output of the lowpass filter block forming the quadrature component is connected to the second input voltage divider whose output is connected to the input of the differentiating device connected in series, the second multiplier and the third low pass filter whose output is an output device receiving the quadrature FSK signals.

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