The demodulator shestnadtsetirichnoe quadrature amplitude manipulation

 

(57) Abstract:

The inventive demodulator contains two four-phase detector 1, 2, two regeneration unit 3, 4, two modulator 5, 6, two vicites 7, 8, two unit generating control signals 9, 10, an adder 11, a filter 12, a voltage controlled oscillator 13. 1 - 3 - 5 - 7 - 9 - 11 - 12 - 13 - 1, 13 - 5, 13 - 9, 13 - 10 - 11, 13 - 2 - 4 - 6 - 8 - 10, 7 - 2, 13 - 6. 2 the sludge.

The invention relates to radio engineering.

The purpose of the invention is the increased robustness.

In Fig. 1 shows a block electrical diagram of the proposed demodulator of Fig.2 is a block circuit diagram form the control signal.

The demodulator contains the first, second, four phase detectors 1, 2, first, second blocks 3, 4 regeneration, the first, second modulators 5, 6, the first, second myCitadel 7, 8, the first, second, blocks 9, 10 forming the control signal, the adder 11, a filter 12, the oscillator (VCO) 13, a voltage controlled. Blocks 9, 10 contain the first, second phase detectors 14, 15, the first, second filters 16, 17 of the lower frequencies, the first multiplier 18, the first comparator 19, the second multiplier 20, the second comparator 21, a phase shifter 22, myCitadel 23.

The demodulator is ISE

SI=A+ cos0t+B+ sin0t, (1) whereo- carrier frequency signal;

A,B,C,D is selected from the set {-1, +1} is the transmitted symbols.

At the output of the VCO 13 is the reference oscillation

Sop= Cos(ot + ), (2) received at the reference input of the phase detector 1.

In this sense the phase detuning between the supporting oscillations, and the first output of the phase detector is formed fluctuation

SI1=A+ cos B+ sin, (3) and at its second output oscillation

SI1I=A+ sin+B+ cos, (4)

Expressions (3) and (4) is obtained after multiplying the oscillation (2) and quadrature him on the input signal SIdefined by the expression (1) and after filtering component at frequency 2o. At small angles at the first and second outputs of the regeneration unit 3 is formed signals A and B respectively, i.e., senior debit transmitted bits of Fallot. Similarly to the first and second outputs of the block and regeneration will be generated signals C and D, respectively, i.e., younger debit transmitted bits of Fallot. Then, in accordance with the signals at the output of unit 3 at the output of the modulator 5 is formed fluctuation

S5= ACos(ot + ) + BSin(ot + ) (5) subject pemeriksa transformation in accordance with formula (1) and (5) output vicites 7 is formed fluctuation

S7=A+ -Acos-Bsincos0t+B+ Bcos+Asinsinot (6)

This variation (6) is supplied to the second input unit 9 provide a control signal at the first input of which receives the oscillation Sop.

Taking into account expressions (6) and (2) it can be shown that the output of filter 16 is formed fluctuation

S16= A+ -Acos-Bsincos-B+ Bcos+Asinsin, (7) and the output of filter 17 is the fluctuation of the form

S17=A+ -Acos-Bsinsin+B+ Bcos+Asincos (8)

Opening parentheses in expressions (7) and (8), we obtain

S16=A+ cos B+ sin A (9)

S17=A+ sin+B+ cos-B (10)

In this case, after a simple trigonometric transformations get that output vicites 23, i.e., the output of block 9 provide a control voltage will be generated oscillation is defined by the expression

S9= + + sin+ - (1-cos)

(11)

In the expression (11) is a component that is not associated with the manipulation, namely sin . . It is in these circumstances, the voltage S9can be used as a control voltage for a phase lock loop frequency. The fluctuation of S9supplied to the first input of the adder 11 having a transfer ratio of this input V1.

Analyzing the similar expressions (3)-(12) can sin+ - (cos-1)

(12) In this signal also has a component that is not related to manipulation, namely 2Sin whereby the voltage S10can also be used as the control voltage in the circuit of the phase-locked loop. The fluctuation of S10supplied to the second input of the adder 11 having a transfer ratio of this input V2.

The analysis of expressions (11) and (12) shows that the noise processes are determined by the same modulating signal:

+ -

In this case, there is a principal possibility to compensate the phase noise caused by the manipulation component expressions (11) through manipulation components of the expression (12).

For these purposes, the proposed demodulator is used, the adder 11, having at its first input transfer ratio V1and on the second input transfer ratio V2.

Consider the resulting discriminatory characteristics of the demodulator, i.e., the dependence of

S12= f () , where S12= V1.S9+ V2.S10.

It should be noted that the output of the formulas (11) and (12) was carried out for small values>> 0.

After coherent demodulation of St. overall, the estimates may differ from the true values of the transmitted symbols as a result of noise, and also due to the fact that the reference oscillation used for demodulation, has some phase shift , which for large values (for ensemble QAM-16 > 16aboutleads to erroneous decisions of the Comparators included in the regeneration unit.

Because the Comparators 19 and 21 and comparator block regeneration is written paralytically a discontinuous function Sig n(x), i.e., the sign function

sign(x)= to obtain the analytical form of discriminatory characteristic for any values not possible.

A computer simulation is a set of coefficients V1and V2minimising the variance of the resulting discriminatory features: V1= -0,5; V2= 1.

1. The DEMODULATOR SHESTNADTSETIRICHNOE QUADRATURE AMPLITUDE MANIPULATION, containing the first and second four-way phase detectors, the first regeneration unit, the first modulator, the first myCitadel and connected in series filter and a voltage controlled oscillator, the output of which is connected with the control inputs of the four-phase detector and the first modulator, the output of which is connected to the first input of the first visitated the input of the demodulator, the output of the first vicites connected to the information input of the second four-way phase detector, and the outputs of the first four-way phase detector through the first regeneration unit connected to the information input of the first modulator and are among the outputs of the demodulator, characterized in that, to improve noise immunity, entered the second regeneration unit, the second myCitadel, the second modulator, two block form the control signal, and the adder, the output of which is connected to the input of the filter, and the first and second inputs with the outputs of the first and second blocks forming control signal, respectively, the input of which is connected to the output of the generator is controlled voltage, and second inputs with the outputs of the first and second vychitala respectively, and the first input of the second myCitadel is the input of the demodulator, and the second input is connected to the output of the second modulator, a reference input connected to a reference input of the first modulator, the outputs of the second four-way phase detector through a second regenerator connected to information inputs of the second modulator are other outputs of the demodulator.

2. Demodulate the United first phase detector, the first lowpass filter and the first multiplier, the output of which is connected to the first input of vicites whose output is the output processing unit control signal, connected in series to the second phase detector, a second low pass filter and the second multiplier, the output of which is connected to a second input of myCitadel, the output of the first lowpass filter through the first comparator is connected to a second input of the second multiplier, the output of the second lowpass filter via a second comparator connected to the second input of the first multiplier, the first inputs of the phase detectors are connected and are the second input of the block form the control signal, the first input of which is the second input of the first phase detector and the input of the phase shifter, the output of which is connected to a second input of the second phase detector.

 

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