RU2269207C2 - RECEIVER OF SIGNALS WITH ABSOLUTE PHASE MANIPULATION FOR ANGLE 140°≤2φ≤60° - Google Patents

Abstract

FIELD: engineering of signal receivers with absolute phase manipulation.

SUBSTANCE: one input of phase detector is connected to linear portion of receiver, and another input is also connected to linear portion receiver, but through narrowband (~300Hz) filter, phase shifter for 90, limiter amplifier, while narrowband filter is also connected to linear portion of receiver. In construction of receiver device phase detector has no reverse operation, because its bearing oscillation is formed by component of bearing frequency of input phase manipulated signal, which for aforementioned angle of manipulation is present in signal.

EFFECT: increased interference resistance of signals receipt with absolute phase manipulation.

1 cl, 1 dwg

Description

The invention relates to the field of radio receivers, and more specifically to signal detectors with absolute phase shift keying.

Known sources that describe the receivers (detectors) of phase-shift oscillations that do not have “reverse operation” [1, 2, 3].

By technical nature, the closest to the invention is the device described in the source [1], which for this reason is taken as its prototype.

The prototype consists of a linear part of a radio signal receiver, a frequency detector and a trigger.

An input signal with absolute phase shift keying (QPSK) at an angle of 140 ° ≤2φ≤160 ° (radio signal) is filtered, amplified, and frequency converted in the linear part of the receiver and fed to the input of the frequency detector. As you know, any frequency detector is a time differentiating device. Therefore, when the phase of the input signal jumps at an angle of + φ, a short positive pulse appears at the output of the frequency detector, and when the phase of the input signal jumps by -φ, a short negative pulse appears at the output of this detector. These short pulses arrive at the inputs of the RS-flip-flop, which is why rectangular pulses that were transmitted appear on its output.

The frequency detector is incoherent. It does not have a reference channel where random jumps in the phase of the reference oscillation occur by 180 °, and therefore its “reverse operation” is excluded in principle.

The main disadvantage of the prototype is the low noise immunity of receiving a signal from the absolute PSK to the specified angle, since it is incoherent and the pulses controlling the operation of the trigger are short.

The technical result of the claimed object is to increase the noise immunity of receiving signals from the absolute PSK to an updated angle of 140 ° ≤2φ≤160 ° by switching to a coherent reception free of “reverse work”.

The essence of the invention lies in the fact that in the prototype, consisting of the linear part of the receiver, a narrow-band filter-separator of carrier frequency oscillations from the input PSK signal, a 90 ° phase shifter, an amplifier-limiter and a phase detector are introduced, and the signal input of the phase detector is connected to the linear output parts of the receiver directly and to its second input (reference) through a narrow-band filter, a 90 ° phase shifter, an amplifier-limiter.

A significant difference of the invention is the combination of the introduced elements and their connections, since only they can increase the noise immunity of reception to almost the maximum possible value and simplify the coherent detector.

In [2], it was proposed to divide the phase shift by 180 ° of the input PSK oscillation by a factor of 2, so that a carrier frequency oscillation appears as a reference oscillation. However, in practice it is difficult to implement. In [3], they switched from absolute QPSK to 180 ° to relative QPSK to exclude “reverse operation”, which is why the probability of a reception error increased by a factor of 2 and the detector became more complicated.

The drawing shows a structural diagram of the proposed receiver, which consists of a linear part 1, a phase detector 2, a narrow-band filter 3, a phase shifter 4 by 90 °, an amplifier-limiter amplitude 5. Blocks 3-5 form a reference channel. Block 5 may be a synchronized oscillator.

The operation of the receiver is as follows.

At the input of block 1, a phase-shifted (QPSK) signal is received, which is filtered out of it in it, amplified in amplitude, and converted in frequency. Analytically, the FMN signal has the form u _FM (t) = Usin [ωt + γ (t) φ], where γ (t) = ± 1, and φ is selected from the specified range of 60 ° ≤φ≤80 °.

Given the value of γ (t) according to the rules of trigonometry, we have:

u _FM (t) = Ucos [γ (t) φ] · sinωt + Usin [γ (t) φ] · cosωt = U [cosφ · sinωt + γ (t) · sinφcosωt].

It can be seen that the component of the carrier frequency (the first term) is proportional to cosφ, the value of which is 0.5≥cosφ≤0.1736. The lower relative level of 0.1736 is the same as the maximum level of the third harmonic at the optimum cutoff angle at which the frequency tripler operates. A frequency counter is usually not used in practice. This determines the maximum angle of manipulation 2φ = 160 °.

The lower angle of manipulation 2φ is determined by the permissible excess of the probability of error compared with the minimum at 2φ = 180 °. Allowable excess P _2φ / P _{180 °} = 2, as with OFMn. If it is> 2, then it is advisable to use OFMn.

The probability of receiving an elementary binary symbol with PSK

P _fm = V (√ (2E / N _o ) · sinφ),

- дополнение к интегралу вероятности до единицы (табулированное);Where

- addition to the probability integral up to unity (tabulated);

E is the energy of the package;

N _o is the spectral power density of Gaussian interference.

Take 2E / N _o = 10 or √ (2E / N _o ) = 3.15.

At 2φ = 180 °, the probability is P _{180 °} = 9.3 · 10 ^-4 , and at 2φ = 160 °. The value of P _{160 °} = 9.676 · 10 ^-4 . Exceeding P _{160 °} / P _{180 °} = 1.05

The remaining calculations are summarized in table 1.

It follows from the table that the manipulation angle is in the range 140 ° ≤2φ <160 °, when the level of the carrier is sufficient to exclude "reverse operation", and the loss in noise immunity is less than with OFMn. At 2φ = 160 °, these losses are almost completely absent (P _{160 °} / P _{180 °} = 1.05≈1).

From the output of unit 1, the QPSK signal is fed to the signal input of the phase detector 2 directly and to its reference input through a filter 3, a phase shifter 4 by 90 °, an amplifier-limiter of amplitude 5. Filter 3 passes to its output only the oscillation of the carrier frequency, which in blocks 4 , 5 is formed into a reference oscillation u _o (t) = U _o cosωt, where U _o = Ucosωt.

Phase detector 2 consists of a signal multiplier and a low-pass filter.

Oscillator output

u _p (t) = u _FM (t) u _o (t) = Usin [ωt + γ (t) φ] · U _O cosωt = 0.5UU _O {sin [γ (t) φ] + sin [2ωt + γ (t) φ]}.

The second term at the doubled intermediate frequency 2ω of the low-pass filter is filtered out and only the first term u _Ф (t) = 0.5U _o Usin [γ (t) φ] - alternating square-shaped pulses, that is, takes place at its output transmitted signal.

The technical and economic effect of the invention is to eliminate reverse work while reducing the probability of signal reception errors by almost 2 times and simplifying the detector.

Information sources

1. A.S. USSR No. 10038. Reception of phase telegraphy without a synchronous local oscillator / Yaroslavsky L.S. et al., 1952.

2. RF patent No. 2113062. Reference oscillator for detecting phase-shift keyed signals / Volkov A.A. Priority from 09/28/1994.

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

Claims (1)

A signal receiver with absolute phase shift keying at an angle of 140 ° ≤2φ≤60 °, consisting of its linear part, characterized in that a phase detector, an intermediate frequency oscillation filter, a 90 ° phase shifter, an amplitude limiter are introduced into it, and the signal input a phase detector is connected to the output of the linear part of the receiver directly and to its second (reference) input through an intermediate frequency oscillation filter connected in series, a 90 ° phase shifter, and an amplitude limiter amplifier.