RU2013875C1 - Phase-manipulated signals demodulator - Google Patents

Abstract

FIELD: computer technology. SUBSTANCE: demodulator has frequency-by-two multiplier 1, multiplier 2, band-pass filter 3, frequency-to-two divider 4, two phase shifters 5 and 8, solving blocks 9 and 10, code converter 11, EXCLUSIVE-OR gates. EFFECT: improved efficiency. 1 dwg

Description

 The invention relates to radio engineering and can be used in the equipment of communication systems with phase shift keying.

 The purpose of the invention is to increase noise immunity while simplifying it.

 The drawing shows a structural electrical circuit of the proposed demodulator.

 The demodulator contains a frequency multiplier 1 by two, a multiplier 2, a bandpass filter 3, a frequency divider 4 by two, the first phase shifter 5, the first, second phase detectors 6, 7, the second phase shifter 8, the first, second decision blocks 9, 10, code converter 11 , element EXCLUSIVE OR 12.

 The demodulator works as follows.

At the input of the demodulator, a four-phase phase-shifted signal is received, which can be represented as
S _in = A cos ω _o t + B sin ω _o t (1) where A and B are the transmitted binary symbols selected from the set {-1, +1};
ω _o - carrier frequency of the signal.

In accordance with the expression (1), at the output of the frequency multiplier 1 by two, we have:
S _s = S _in ² (2)
Having reduced expression (2) to another form, we can write
S _s = 1 + AB sin 2 ω _o t (3)
Since the data at the output of the demodulator are presented, as a rule, in binary code, that is, the demodulated values A and B are selected from the set {0, 1}, then at the output of the element EXCLUSIVE OR 12 we have a signal of the form
S ₂ = A + B (4)
Given that between the logical and analog levels in the demodulator there is a correspondence defined by the following rule: {0 - -1; 1 - 1, we can rewrite expression (4) in the form
S ₂ ^' = AB (4')
Given the expressions (3) and (4 ^' ), the signal at the output of the multiplier 2 has the form
S ₁ = AB + (AB) ² sin 2 ω _o t (5)
It can be seen from expression (5) that the component with doubled frequency does not contain manipulation and now it can be distinguished by band pass filtering.

Then at the output of the bandpass filter 3, the signal has the form
S ₅ = sin 2 ω _o t, (6)
and at the output of the divider 4 frequencies into two - type
S ₆ = sin ω _o t (7)
The signal defined by expression (7) then goes through the phase shifter 5 to the reference inputs of the quadrature phase detectors 6 and 7, where it is used for coherent demodulation of the phase-shifted signal (1).

Claims (1)

 A PHASOMANIPULATED SIGNAL DEMODULATOR comprising a bandpass filter, a first phase shifter, the output of which is connected to the second input of the first phase detector and through the second phase shifter with the second input of the second phase detector, the first inputs of the first and second phase detectors are connected and are the input of the demodulator, and their outputs, respectively, through the first and the second decision blocks are connected to the inputs of the code converter, the output of which is the output of the demodulator, characterized in that, in order to increase noise immunity and at the same time, a frequency multiplier by two, a multiplier, a frequency divider by two, and an EXCLUSIVE OR element are introduced, whose inputs are connected to the outputs of the first and second decision blocks, and the output is connected to the first input of the multiplier, the second input of which is connected to the output of the frequency multiplier by two, whose input is the input of the demodulator, the output of the multiplier through a series-connected bandpass filter and a frequency divider into two is connected to the input of the first phase shifter.