The signal receiver quadrature amplitude manipulation

 

(57) Abstract:

Usage: in radio engineering. The inventive receiver contains three demodulator, the sweep generator signal, two lowpass filter, two thresholds, block, item OR two blocks of code discernment, the carrier recovery block, two Phaser. 2 Il., table 1.

The invention relates to electrical engineering and can be used at the reception signals of the quadrature amplitude-shift keying (QAM).

Known receiver QAM signals containing the first block of code discernment, the first lowpass filter, the output of which is connected to the input of the first threshold unit, the sweep generator signal, the output of which is connected to the first input of the carrier recovery block, the output of which is connected to the reference input of the first demodulator, the signal input of which is connected to the second input of the carrier recovery block is the input of the receiver, the outputs of which are the outputs of the first demodulator.

A disadvantage of the known device is the low reliability of reception, due to the low reliability of detecting fraudulent grips phase when receiving QAM signals.

The aim of the invention is polysilazane block diagram of the receiver; in Fig.2 - one of the quadrants of the signal plane of the ensemble KAM.

The receiver CAM includes first, second and third demodulators 1, 2 and 3, the generator 4, the sweep signal, the first and second filters 5 and 6, the lower frequencies of the first and second threshold blocks 7 and 8, the element OR 9, the first and second blocks 10 and 11 of the code of discernment, block 12 recovery of the carrier, the first and second phasers 13 and 14.

The output of the generator 4 connected to the first input unit 12, the output of which is connected to a reference input of the demodulator 1 and to the inputs of the phasers 13, 14. Signal input of the demodulator 1 is connected to the signal inputs of the demodulators 2, 3 and to the second input unit 12 and an input of the receiver, the outputs of which are the outputs of the demodulator 1. The outputs of phasers 13, 14 are connected respectively to the control inputs of the demodulators 2, 3, the outputs of which are connected with inputs respectively of blocks 11, 10. The outputs of blocks 10, 11 through the filters 5, 6 are connected respectively to the inputs of threshold units 7, 8, and outputs them through the element OR 9 is connected to the input of the generator 4.

The principle of detection of false grips on the phase of the receiver signal CAM is that for some values of the angle of phase mismatch in some from the national point.

This condition can be detected with a device code of discernment, low pass filter and a threshold unit.

Consider the operation of the receiver on the example of the demodulation of the QAM-16, i.e., the block 12 of the carrier recovery of the QAM signals-16 is built on four scheme and, therefore, has a false captures signals in the vicinity of values = 23,2aboutand = 66,8about(according to calculations). In General, when changing from 0o90aboutthe signal receiver QAM-16 operates in the following modes (see table).

The table shows that the most extensive (and, consequently, the most suitable for work) to the range in which the shaded area (Fig.2) do not get a signal point, is the area from 32,34 to 57,66aboutcenter 45about. Therefore, if the signal recovered carrier frequency to give a certain phase shift, the value of point a false capture signal will be shifted in the range from 32,34 to 57,60aboutat work the control of the demodulator in which the shaded area of decision will contain no signal interference.

The angle by which the turn signal phasers 13 and 14, can wibig on +27aboutand the second phase shifter 14 at -27about.

The receiver operates as follows.

The demodulated data signals from the output of the first demodulator 1 (which produces coherent detection using restored in block 12 of the carrier) are fed to the output of the receiver. Simultaneously, the demodulation signal is in the second demodulator 2 and the third demodulator 3, however, are bearing offset by an angle + and - , sootvetstvenno, in the first phase shifter 13 and the second phase shifter 14. In that case, if the block 12 recovery of the carrier is in the area of the true capture ( = 0aboutor = 90about), then at = 27aboutaccording to the table, nor the first block of code discernment 10 (where1= -27aboutor1= 63about) or the second block of code discernment 11 (where2= 27aboutor2= 117aboutthrough appropriate filters 5, 6 of the lower frequencies and threshold units 7, 8 will not run the generator 4, the sweep signal. In this case the position of the working point on the axis of the second 2 and third 3 demodulators equidistant from the areas in which the sweep begins, which ensures stable operation of the unit and consequently, the first demodulator 1.

If the unit 12 (and the trace is t detected by the second unit 11 code distinguishing (where2will be equal to 23.2about+ 27about= 50,2about). Similarly, if a false capture unit 12 will occur when = 66,8aboutit will be detected through the first block 10 code distinguishing (where1will be 66,8about- 27about= 39,8about).

The detecting false signal capture and elimination occur as follows. The signal level on the output of one of the filters 5 or 6 of the lower frequencies is reduced below an acceptable level, as determined by one of the threshold blocks 7 and 8, through which the element OR 9 by a high voltage runs the generator 4, the sweep signal. This generator rebuilds the block 12 as long as they have not been ->> 0 (at the outputs of both filters 5 and 6, the lower frequencies will be high potentials; at the outputs of both threshold blocks 7 and 8 - low logic levels, and, therefore, the sweep will be terminated).

The value is chosen taking into account the specific discriminatory characteristics of the block 12 for QAM signal with any number of phases, taking into account the presence of false points of seizures.

Thus, the proposed receiver QAM signals in comparison with the prototype allows to significantly increase the reliability of determining the state of a false capture whitefish the structure (demodulator, the block of code discernment, low pass filter, threshold block in each branch) optimal working conditions in the sense of maximizing the reliability of the decisions about the presence of false capture.

The SIGNAL RECEIVER QUADRATURE AMPLITUDE MANIPULATION, containing the first block of code discernment, the first lowpass filter, the output of which is connected to the input of the first threshold unit, the sweep generator signal, the output of which is connected to the first input of the carrier recovery block, the output of which is connected to the reference input of the first demodulator, the signal input of which is connected to the second input of the carrier recovery block is the input of the receiver, the outputs of which are the outputs of the first demodulator, characterized in that, to improve the reliability of reception by increasing the reliability of detecting fraudulent grips, introduced two of the demodulator, the second block of code discernment the second low pass filter, the second threshold unit, element, OR both the first and the second phase, the outputs of which are connected to the reference inputs, respectively, of the second and third demodulators whose outputs are connected to inputs of respectively the second and first blocks of code discernment, outputs and the second threshold blocks through the element OR connected to the generator input sweep signal, the output of the carrier recovery block is connected to the inputs of the first and second phase signal input of the first demodulator connected to the signal inputs of the second and third demodulators, and the output of the second lowpass filter connected to the input of the second threshold unit.

 

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