RU2136115C1 - Device for demodulation of multiple-position signals - Google Patents

Abstract

FIELD: signals with quadrature amplitude manipulation. SUBSTANCE: phase tuning circuit of voltage controlled oscillator has additional controlled amplifier which gain K(t) is equal to K_oS(t), while S9T) is equal to

, where

and

Description

 The invention relates to radio engineering and can be used in discrete message transmission systems.

A device [1] is known, comprising a splitter, the outputs of which are connected respectively to common-mode and quadrature signal processing channels, each of which consists of a series-connected multiplier, a low-pass filter, a level quantizer, a subtractor and a low-frequency multiplier, with a low-pass filter output in each channel additionally connected to the second input of the subtractor, and the second output of the level quantizer with the second input of the low-frequency multiplier of another channel. The output of the low-frequency multiplier of each channel is connected to the corresponding input of the third subtractor, the output of which is connected to the voltage-controlled generator through a proportional-integrating filter. The output of the voltage-controlled generator is connected to the second input of the multipliers, directly in the in-phase channel of signal processing, and in quadrature through the phase shifter by π / 2.
The disadvantage of this device is the presence of a manipulation component in the frequency control circuit of the voltage-controlled generator, which causes additional dispersion of the phase of the reference oscillation and reduces the noise immunity of the reception.

The closest in technical solution is a carrier synchronization device and detecting KAM signals [2], containing a splitter, the outputs of which are connected respectively to common-mode and quadrature signal processing channels, each of which consists of a series-connected multiplier, low-pass filter, level quantizer, low-frequency a multiplier, and in each channel, the output of the low-pass filter is additionally connected to the second input of the low-frequency multiplier of another channel. The output of the low-frequency multiplier of each channel is connected to the corresponding input of the subtractor, the output of which is connected to the voltage-controlled generator through a proportional-integrating filter. The output of the voltage-controlled generator is connected to the second input of the multiplier, directly in the in-phase channel of signal processing, and in quadrature through the phase shifter by π / 2.
The disadvantage of this device is the presence of a large-level manipulation component in the frequency control circuit of the voltage-controlled generator, which reduces the quality of the reference oscillation and, therefore, the noise immunity of the device.

 The aim of the invention is to increase noise immunity by improving the quality of the reference oscillation.

где

оценки синфазной и квадратурной составляющих сигнала на интервале длительности символа, - соединенный с выходом квантователей уровня и регулируемый усилитель с коэффициентом передачи K(t):
K(t) = K_oS(t),
где L²=M - позиционность сигнала, - сигнальный вход которого соединен с выходом вычитателя, вход управления - с выходом формирователя сигнала, а выход с пропорционально-интегрирующим фильтром.This goal is achieved by the fact that in a known device containing a splitter, the outputs of which are connected respectively to in-phase and quadrature signal processing channels, each of which consists of a series-connected multiplier, a low-pass filter, a level quantizer, a low-frequency multiplier, with a filter output in each channel low-frequency is additionally connected to the second input of the low-frequency multiplier of another channel, and the output of the low-frequency multiplier is connected to the corresponding input of the subtractor , a proportional-integrating filter, the output of which is connected to a voltage-controlled generator connected to the second input of the multipliers, directly in the in-phase channel of signal processing, in quadrature through the phase shifter to π / 2, the signal conditioner S (t) is additionally introduced:

Where

estimates of the in-phase and quadrature components of the signal over the symbol duration interval, is an adjustable amplifier connected to the output of the level quantizers and with the transmission coefficient K (t):
K (t) = K _o S (t),
where L ² = M is the positionality of the signal, - the signal input of which is connected to the output of the subtractor, the control input is the output of the signal conditioner, and the output is with a proportionally integrated filter.

 Comparative analysis with the prototype shows that the inventive device is characterized by the presence of a signal shaper and an adjustable amplifier with corresponding connections and is unknown from the prior art.

 Thus, the invention meets the criterion of "novelty."

 Analysis of known technical solutions in the studied and related fields allows us to conclude that the introduced functional units are known. However, introducing them into a carrier frequency synchronization device and demodulating signals with quadrature amplitude manipulation with the indicated relationships gives this device new properties. The introduced functional units interact in such a way that the signal transmission coefficient in the voltage-controlled generator control circuit changes inversely with the signal level at the input of the device. This leads to a decrease in the level of the manipulation component in the control circuit of the voltage-controlled generator, and therefore to a decrease in the phase dispersion of the generated oscillation.

 Thus, the invention meets the criterion of "Inventive step", because it does not explicitly follow from the prior art for a specialist.

 The invention can be used in digital information transmission systems using signals with quadrature amplitude manipulation (QAM).

 Thus, the invention meets the criterion of "Industrial applicability".

 The drawing shows a structural diagram of the proposed device demodulation of multi-position signals.

 The device comprises a splitter 1, multipliers 2 and 3, a phase shifter by π / 2 4, low-pass filters 5 and 6, a voltage-controlled oscillator 7, level 8 and 9 quantizers, a proportionally integrated filter 10, an adjustable amplifier 11, a signal conditioner 12, low-frequency multipliers 13 and 14, subtractor 15.

 The input of splitter 1 is the input of the device. The outputs of the splitter 1 are connected respectively to the first input of the multipliers 2 and 3.

 The output of the voltage-controlled generator 7 is connected to the second input of the multiplier 2 and the input of the phase shifter by π / 2 4, the output of which is connected to the second input of the multiplier 3. The outputs of the multipliers 2 and 3 are respectively connected to the low-pass filters 5 and 6, the output of which is the outputs of the device and connected respectively to quantizers of level 8 and 9 and the second input of low-frequency multipliers 14 and 13. The output of quantizers to levels 8 and 9, respectively, connected to the first input of low-frequency multipliers 13 and 14 and the inputs of signal former 12. Output n of the frequency multipliers 13 and 14 are respectively connected to the inputs of the subtractor 15, the output of which is connected to the signal input of the adjustable amplifier 11. The output of the signal shaper 12 is connected to the control input of the adjustable amplifier 11, the output of which is connected to the proportional-integrating filter 10. The output of the proportional-integrating filter 10 connected to a voltage controlled generator 7.

 The device operates as follows.

A voltage controlled oscillator 7 (VCO) generates a reference oscillation y (t):
y (t) = cosω _o t,
where ω _o is the frequency of free oscillations of the VCO 7.

где a, b = -(L-1), -(L-3), ... (L-1) - амплитуды квадратурных составляющих сигнала;
ω, φ - частота и начальная фаза сигнала;
α(t), β(t) - амплитуды квадратурных составляющих шума с дисперсией σ².
В результате квадратурного детектирования при ω = ω_o на выходе фильтров нижних частот 5 и 6 формируются сигналы
I(φ) = acosφ+bsinφ+α(t); (2)
Q(φ) = bcosφ-asinφ+β(t), (3)
которые соответственно поступают на квантователи уровня 8 и 9 и вторые входы низкочастотных умножителей 14 и 13.Received with additive interference M-position QAM signal U (t) at intervals of the duration of the symbol T can be represented by the following expression

where a, b = - (L-1), - (L-3), ... (L-1) are the amplitudes of the quadrature components of the signal;
ω, φ - frequency and initial phase of the signal;
α (t), β (t) are the amplitudes of the quadrature noise components with dispersion σ ² .
As a result of quadrature detection at ω = ω _o , signals are generated at the output of low-pass filters 5 and 6
I (φ) = acosφ + bsinφ + α (t); (2)
Q (φ) = bcosφ-asinφ + β (t), (3)
which respectively go to the quantizers of level 8 and 9 and the second inputs of the low-frequency multipliers 14 and 13.

и квадратурной

составляющих сигнала, которые соответственно поступают на первый вход низкочастотных умножителей 13 и 14 и входы формирователя сигнала 12, с выхода низкочастотных умножителей 13 и 14 сигналы подаются на соответствующие входы вычитателя 15, а затем на вход регулируемого усилителя 11. На выходе регулируемого усилителя 11 формируется сигнал оценки начальной фазы сигнала f(φ):

который через пропорционально-интегрирующий фильтр 10 поступает на вход ГУН 7, подстраивая его частоту.At the output of quantizers of level 8 and 9, in-phase evaluation signals are generated

and quadrature

signal components, which respectively enter the first input of the low-frequency multipliers 13 and 14 and the inputs of the signal shaper 12, from the output of the low-frequency multipliers 13 and 14, the signals are fed to the corresponding inputs of the subtractor 15, and then to the input of the adjustable amplifier 11. At the output of the adjustable amplifier 11, a signal is generated estimates of the initial phase of the signal f (φ):

which through a proportional-integrating filter 10 enters the input of the VCO 7, adjusting its frequency.

где

(6)
При вероятности ошибки P ≥ 10^-2 оценки синфазной и квадратурной составляющих сигнала

и для КАМ-16:

F(φ) ≈ 3K_osinφ;
D(φ) ≈ 1,03K $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ sin²φ+K $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ σ²;
D(φ)/F¹²(O) ≈ 0,114sin²φ+0,11σ². (7)
Для аналога:
f_a(φ) = (I(φ)-a)sgnb-(Q(φ)-b)sgna;
F_a(φ) = 4sinφ;
D_a(φ) = 8sin²φ/2+2σ²;
D_a(φ)/F $\genfrac{}{}{0ex}{}{\text{12}}{\text{a}}$ (O) = 0,5sin²φ/2+0,125σ². (8)
Для прототипа:
f_n(φ) = I(φ)•b-Q(φ)a;

D_n(φ) = 32sin²φ+10σ²;
D_n(φ)/F $\genfrac{}{}{0ex}{}{\text{12}}{\text{n}}$ (O) = 0,32sin²φ+0,1σ². (9)
Анализ выражений (7), (8), (9) показывает, что заявляемое устройство при примерно одинаковом уровне шумовой составляющей имеет выигрыш по уровню манипулярной составляющей: по отношению к прототипу на 4,5 дБ, к аналогу 3,6 дБ - таким образом, формирует более качественное опорное колебание, а следовательно, обладает более высокой помехоустойчивостью.The quality of the generated reference oscillation is determined by the dispersion of the signal f (φ):

Where

(6)
When the error probability P ≥ 10 ^{-2, the} estimates of the in-phase and quadrature components of the signal

and for KAM-16:

F (φ) ≈ 3K _o sinφ;
D (φ) ≈ 1.03K $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ sin ² φ + K $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ σ ² ;
D (φ) / F ¹² (O) ≈ 0.114 sin ² φ + 0.11σ ² . (7)
For analog:
f _a (φ) = (I (φ) -a) sgnb- (Q (φ) -b) sgna;
F _a (φ) = 4sinφ;
D _a (φ) = 8sin ² φ / 2 + 2σ ² ;
D _a (φ) / F $\genfrac{}{}{0ex}{}{\text{12}}{\text{a}}$ (O) = 0.5sin ² φ / 2 + 0.125σ ² . (eight)
For prototype:
f _n (φ) = I (φ) • bQ (φ) a;

D _n (φ) = 32sin ² φ + 10σ ² ;
D _n (φ) / F $\genfrac{}{}{0ex}{}{\text{12}}{\text{n}}$ (O) = 0.32sin ² φ + 0.1σ ² . (nine)
An analysis of expressions (7), (8), (9) shows that the claimed device with approximately the same level of noise component has a gain in the level of the manipulated component: relative to the prototype by 4.5 dB, to the analogue of 3.6 dB - thus , forms a better reference oscillation, and therefore has a higher noise immunity.

 The proposed device is implemented at an intermediate frequency of 160 MHz using analog and digital element base.

 Splitter 1, multipliers 2 and 3, phase shifter 4, low-pass filters 5 and 6, voltage-controlled oscillator 7, proportional-integrating filter 10 are implemented on analog elements, while AD 834 integrated quadrature multipliers are used as multipliers 2 and 3.

 Quantizers 8 and 9, low-frequency multipliers 13 and 14, a subtractor 15, a signal conditioner 12 and an adjustable amplifier 11 are implemented on digital integrated elements: ADC AD 9058, ROM 27C128, DAC AD 7524.

 Practical use of the proposed device can improve the noise immunity of receiving signals with quadrature amplitude manipulation.

Claims (1)

A device for demodulating multiposition signals containing a splitter, the outputs of which are connected respectively to common-mode and quadrature signal processing channels, each of which consists of a series-connected multiplier, a low-pass filter, a quantizer, a low-frequency multiplier, and in each channel the output of the low-pass filter is additionally connected to the second the input of the low-frequency multiplier of another channel, and the output of the low-frequency multiplier is connected to the corresponding input of the subtractor, the proportion an onal-integrating filter, the output of which is connected to a voltage-controlled generator connected to the second input of the multipliers, in the in-phase channel of signal processing - directly, in quadrature - through a phase shifter by π / 2, characterized in that it further comprises a signal conditioner

Where

estimates of the in-phase and quadrature components of the signal over the symbol duration interval connected to the output of the level quantizers, and an adjustable amplifier with the transmission coefficient k (t): k (t) = K _o s (t), whose signal input is connected to the subtractor output, the control input - with the output of the signal conditioner, and the output with a proportional-integrating filter.