RU124461U1 - Coherent Signal Detector with 180 ° Phase Manipulation - Google Patents

Abstract

A 180 ° coherent signal detector with absolute phase shift keying (QPSK), consisting of a signal multiplier, a reference oscillator (FOC), a low-pass filter (LPF) connected to the output of the signal multiplier, the information input of which is connected to its reference input through the FOC, characterized in that it additionally introduces a digital signal regenerator (DS), a 180 ° phase manipulator, a quadrator, a unit for extracting the square root of the input signal, a trigger frequency divider for two, a signal multiplier, phase the first detector (PD) and three time delay blocks, with a central regenerator, a 180 ° phase manipulator, a quadrator, a square root extractor, a trigger, a signal multiplier, and a phase detector connected to the LPF output in series; the second input of the phase manipulator is connected to the output of the FOC through the first time delay unit, the second input of the introduced multiplier is connected to the quadrator output through the second time delay unit, and the second PD input is connected to the phase manipulator 180 ° through the third time delay unit.

Description

The utility model (PM) relates to the field of receiving radio signals.

Known coherent signal detectors with absolute phase shift keying (PSK) at 180 °, described in various sources, for example in:

1. Okunev Yu.B. Digital transmission of information by phase-shifted signals. - M .: Radio and communications, 1991.

2. Gorelov G.V., Volkov A.A., Shelukhin V.I. Channel-forming devices of railway telemechanics and communications. - M .: GOU. 2007.

By its technical nature, the coherent detector described in the first source, which for this reason is taken as its prototype, is closest to PM. In another source, an analogue of PM is described.

The prototype is a utility model (PM) consists of a signal multiplier, a reference oscillator (FOK), a low-pass filter (low-pass filter), and a low-pass filter is connected to the output of the multiplier, the inputs of which are interconnected via the FOK.

The generated reference oscillation from the input QPSK to the 180 ° signal has 180 ° phase jumps in time, at which the CS at the output of the low-pass filter is accepted on the contrary: units are zeros and zeros are units. This phenomenon is called the reverse operation of a coherent signal detector with an absolute QPS of 180 °, which completely breaks the connection and therefore this type of modulation is not used in practice. Instead of absolute, in practice they use a relative QPSK (OFMn) of 180 °, which does not completely eliminate the reverse operation, provides a probability of signal reception error 2 times greater than the absolute QPSK of 180 ° in the absence of reverse operation.

The main disadvantage of the prototype is the presence of reverse operation of a coherent signal detector with an absolute PSK of 180 °, which does not allow its use in practice to obtain the maximum possible noise immunity of receiving these signals. The OFMn used in practice provides a 2-fold higher probability of signal reception error compared to the absolute FMN and does not completely eliminate the reverse operation of the coherent detector.

The technical result of PM is the realization of the maximum possible noise immunity of signal reception due to the exclusion of the reverse operation of the coherent signal detector with an absolute QPS of 180 °, which allows its use in practice.

The essence of PM consists in the fact that in a coherent signal detector with absolute phase shift keying (PSK) by 180 °, consisting of a signal multiplier, a reference oscillator (FOK), a low-pass filter (LPF) connected to the output of the signal multiplier, the information input of which connected to its reference input through the FOC, additionally introduced a digital signal regenerator (DS), a 180 ° phase manipulator, a quadrator, a square root extractor from the input signal, a trigger - a frequency divider by two, a signal multiplier, ph a call detector (PD) and three time delay blocks, moreover, a central regenerator, a 180 ° phase manipulator, a quadrator, a square root extractor, a trigger, a signal multiplier, a phase detector are connected in series to the LPF output; the second input of the phase manipulator is connected to the output of the FOC through the first time delay unit, the second input of the introduced multiplier is connected to the quadrator output through the second time delay unit, and the second PD input is connected to the phase manipulator 180 ° through the third time delay unit.

A significant difference between the PMs is the introduced elements and their relationships, since only they can completely eliminate the reverse operation of the coherent signal detector with an absolute PSK of 180 ° and achieve the indicated technical effect - ensuring the maximum possible noise immunity of signal reception.

The utility model is illustrated by drawings of figures 1, 2.

Figure 1 presents the structural diagram of the PM, and figure 2 is a timing diagram explaining its operation.

In figure 1 is indicated:

1, 12 - signal multipliers;

2 - shaper reference oscillations;

3 - low-pass filter (low-pass filter);

4 - digital signal regenerator;

5, 9, 10 - time delay blocks;

6 - phase manipulator signal 180 °;

7 - block squaring the input signal (quad);

8 - block extract square root of the input signal;

11 - trigger - frequency divider by 2;

13 - phase detector.

Entered elements are outlined with a dashed line.

The operation of the circuit is as follows.

The input signal u _in (t) with an absolute QPS of 180 °, shown in Fig. 1b and corresponding to the transmitted one (Fig. 2a), is fed to the information input of the signal multiplier 1 directly and in parallel to its reference input through the FOC 2 in the form of a carrier frequency oscillation u ₂ (t) = U ₂ sinώt. In the expanded form, U _in (t) = Usin (ωt + γ (t) Δφ-Δφ). Since γ (t) = ± 1 is the sign of the modulating signal, a change in the phase of the oscillation of the carrier frequency from 0 to 180 ° is given by the expression γ (t) Δφ-Δφ, where Δφ = 90 °. At the output of the multiplier 1 there is a fluctuation

u ₁ (t) = u _in (t) u ₂ (t) = Usin (ωt + γ (t) Δφ-Δφ) U ₂ sinωt =

= 0.5UU ₂ Cos (γ (t) Δφ-Δφ) -0.5UU ₂ Cos (2ώt + γ (t) Δφ-Δφ).

Low-pass filter 3 passes on its output only the first term, which is why at the output of the phase detector, consisting of blocks 1, 2, 3, there will be a low frequency CS u ₃ (t) = U ₃ cos (γ ₁ (t) Δφ-Δφ) = U ₃ sin (γ ₁ (t) Δφ) = γ ₁ (t) U ₃ , since Δφ = π / 2 and U ₃ = 0.5UU ₂ . Due to spontaneous jumps by 180 of the reference oscillation U ₂ (t), the regularity γ (t) is violated, which is shown in Fig. 2c in the form of a cross and is marked with a subscript 1 of γ (t). When detecting using such a reference oscillation with a cross, the CS at the output of block 6 is distorted (Fig. 2d), not matching the transmitted one (Fig. 2a). In addition, the detected DS from (1) is distorted by interference and transmission conditions. Therefore, in the regenerator 4, the DS from (1) is freed from interference and distortion and then fed to the information input of the phase manipulator 6 by 180 °, to the high-frequency input of which reference oscillation is supplied from the output of block 2 through the time delay unit 5. Phase manipulator 180 ° 6 is made in the form of a multiplier of an alternating CS u ₄ (t) and a reference oscillation u ₂ (t), therefore, at its output, the signal u ₆ (t) = u ₄ (t) u ₂ (t) = U ₆ sin (ωt + γ (t) Δφ-Δφ), which coincides with the input signal u _in (t). Here U ₆ = U ₄ U ₂ .

Random phase jumps at 180 ° of the reference oscillation u ₂ (t) cause the same phase jumps of the low frequency signal u ₃ (t) and u ₄ (t) (figv, d). Therefore, in block 6, the signals u ₄ (t) and u ₂ (t) of the same sign are multiplied between themselves, caused by a random phase jump of 180 ° of the reference oscillation u ₂ (t), which eliminates these jumps in the signal u ₆ (t). Such an ideal QPSK at 180 ° signal u ₆ (t) is fed to the input of a quadrator 7, at the output of which there are unipolar sinusoidal half-waves, as at the output of a half-wave rectifier (Fig.2d).

Этими острыми концами запускается триггер 11, который делит их частоту в 2 раза, как показано на фиг.2е в виде знакопеременных прямоугольных импульсов. Эти прямоугольные импульсы поступают на один вход перемножителя сигналов 12, на другой вход которого подаются однополярные синусоиды с выхода квадратора 7 через блок задержки по времени 9. При перемножении положительных полусинусоид с отрицательными значениями этих импульсов полусинусоиды меняют свой знак на отрицательный, отчего на выходе блока 12 образуется гармоническое колебание несущей частоты (фиг.2ж), которое является опорным для фазового детектора 13. На информационный вход блока 12 подается идеальный сигнал с ФМн на 180° с выхода блока 6 через блок задержки по времени 10. Фазовый детектор 13 состоит из перемножителя сигналов и ФНЧ на его выходе. Поэтому на выходе его ФНЧ имеет место цифровой сигнал (фиг.2з), точно совпадающий с переданным ЦС фиг.2а. Согласно вышеизложенному обратная работа блока 13 исключена.These half-waves arrive at the reference input of block 8 for extracting the square root from them, at the output of which the sharp ends of the half-sine waves increase according to the expression

These sharp ends trigger 11, which divides their frequency by 2 times, as shown in Fig.2E in the form of alternating rectangular pulses. These rectangular pulses are fed to one input of the signal multiplier 12, to the other input of which unipolar sinusoids are fed from the output of quad 7 through a time delay unit 9. When multiplying positive half-sine waves with negative values of these pulses, the half-sine waves change their sign to negative, which is why at the output of block 12 a harmonic oscillation of the carrier frequency is generated (FIG. 2g), which is a reference for the phase detector 13. An ideal signal from the PSK 180 ° from the output of the block is fed to the information input of block 12 6 through a time delay unit 10. The phase detector 13 consists of a signal multiplier and a low-pass filter at its output. Therefore, at the output of its low-pass filter there is a digital signal (fig.2z), exactly coinciding with the transmitted CA figa. According to the foregoing, the reverse operation of block 13 is excluded.

We also note that as a block of FOK 2 can be any known shaper according to the methods of Pistolkors, Siforov, Ageev, Kostas, etc.

The technical and economic effect of the invention is to ensure the maximum possible noise immunity of signal reception by eliminating the reverse operation of a coherent signal detector with an absolute FMN of 180 °. Compared to the relative FMN (OFMn) at 180 °, which is the most noise-resistant of all used in practice, the gain is 2 dB.

Claims (1)

A 180 ° coherent signal detector with absolute phase shift keying (QPSK), consisting of a signal multiplier, a reference oscillator (FOC), a low-pass filter (LPF) connected to the output of the signal multiplier, the information input of which is connected to its reference input via the FOC, characterized in that it additionally introduces a digital signal regenerator (DS), a 180 ° phase manipulator, a quadrator, a unit for extracting the square root of the input signal, a trigger frequency divider for two, a signal multiplier, phase the first detector (PD) and three time delay blocks, with a central regenerator, a 180 ° phase manipulator, a quadrator, a square root extractor, a trigger, a signal multiplier, and a phase detector connected to the LPF output in series; the second input of the phase manipulator is connected to the output of the FOC through the first time delay unit, the second input of the introduced multiplier is connected to the quadrator output through the second time delay unit, and the second PD input is connected to the phase manipulator 180 ° through the third time delay unit.

Images