SU1231624A1 - Device for demodulating signals with minimum-shift keying - Google Patents

Abstract

The invention relates to electrical communication. Noise immunity increases. The device contains the elements EXCLUSIVE OR 1 and 14, the adder 15, the decisive unit (RB) 16, the information channel (IR) 2, consisting of a phase shifter 3, two delay elements 4 and 7, a phase detector 5, an imager 6 information signal and an element EXCLUSIVE OR 8, and test channels (PCs) 9 and 17, each consisting of a delay element 10, a phase detector I1, a checker signal I2, an EXCLUSIVE item OR 13, a decoder 18, a turntable 19, the weighting factor of ntbv and a delay block 20 and signal correction . The RF signal with the manipulated minimum shift is supplied to IR 2 and PC 9 & 17, where the input signal is demodulated by the autocorrelation method. Elements EXCLUSIVE OR 1 and 14, connected to IR 2, generate test signals at their codes that are sent to the PCS9 and 17. PC9 and 17 generate error correction signals in the case of a single symbol failure in IR 2. These signals are sent to adder 15 and then to RB 16. When the set threshold is reached, RB 16 produces a signal. (Ls

Description

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the corresponding corresponding symbol OR 8 IR 2. The goal is achieved by introducing an information signal by acting on the elements EXCLUSIVE OR 14, summing the output element EXCLUDING the matrices 15, RB 16 and PK 17. 3 Il.

The invention relates to telecommunications and can be used in radio receivers of signals manipulated by a minimum shift (MMC). ,

The purpose of the invention is to improve the noise immunity of the device.

Fig. 1 shows a structural electrical circuit of a device for demodulating signals with a minimum shift shift; in fig. 2 shows an example of implementation of a delay unit and a signal correction; in fig. 3 is an illustration of the law of phase change. signal from MMS.

A device for demodulating signals with a minimum shift provides the main element EXCLUSIVE OR 1, information channel 2, including phase shifter 3, first delay element 4, phage detector 5, driver 6; information signal, second delay element 7 and output element EXCLUSIVE OR 8 and the main test channel 9, which includes a delay element 10, a phase detector 11, a forg-meter 12 of the test signal and an element IS1Sh10CH10-ALSE OR 13, and also contains additional elements EXCLUSIVE OR 14, adder 15, re This unit 16, additional test channels 17 and one input to each test channel decoder 18, shaper 19 weights and block 20 delay and signal correction.

. The delay and signal correction unit (Fig. 2) contains delay elements 21 and EXCLUSIVE OR element 22.

The device works as follows.

The operation of the device for demodulating signals from the MMC is based on the property of these signals, namely, that the phase of the transmitted signal at the time of transition from one transmission to another does not change abruptly, as in

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five

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conventional systems with phase manipulation, and smoothly. The value of the phase of the transmitted signal from the MMS at the end of the current burst with respect to the beginning increases by and / 2 with a single sending of the information signal or decreases with a zero sending. This is illustrated by the diagrams in FIG. 3 for a specific implementation of the information signal (0110). Oblique lines depict the possible course of a change in the phase of a transmitted signal in any possible realizations of the information signal. The points of intersection of the inclined lines with horizontal lines give the resolved values of the phases of the signal from the MMC at the boundaries of the parcels with respect to the reference point taken as zero. The presence of the forbidden phase values of the signal from the MMC at the boundaries of the parcels is used to correct the errors, which makes it possible to increase the noise immunity of the communication without introducing any additional coding.

. The radio frequency signal from the MMC is fed from the output of the matched filter (not shown) to the phase shifter 3 at “/ 2”, to the second input of the phase detector 5 of information channel 2, to the second and third inputs of the main test channel 9 and all even additional test channels 17, as well as on the third inputs of all odd additional check channels. The purpose of the phase shifter 3 is to eliminate the uncertainty of the phase of the signal with a multiple of 90 MMS. The delay interval element A (T) and the phase detector 5 of information channel 2 are the simplest autocorrelation demodulator of signals with MMC. The voltage at the output of this. demodulator of torus is equal to U U sineiT. The sign of the specified voltage is determined by the phase shift between the current and time delayed T packages. AT

31231624

the information signal shaper 6 a decision is made on the value of the current-parcel in accordance with the rule

and 11 but shch

 - {i;

if u, 0

if u, 0.

The received sequence of information parcels V from the output of the information signal generator 6 is delayed by K + 1 clock intervals by the second delay element 7 and through the output element EXCLUSIVE OR 8 is fed to the output of the device (here K denotes the total number of test channels, including the main one).

In the test channels, the input signal is also demodulated by the autocorrelation method. However, in contrast to the information channel, the amount of delay by the delay elements 10 depends on the number of the test channel. So in the main test channel this time is

two clock intervals - 2T, in the first25 which corrects the corresponding

additional test channel - ST, in the second channel - 4T, etc. In the future, the operation of the device will be considered for the case of three test channels (the main 9 and 30 are two additional 17). In the main test channel 9, the test signal generator 12 makes decisions according to the same rule as the information signal generator 6. In the additional test channels 17, the decision is made in accordance with the rule

V V 1 O 4 about.

if Ugjj Oh if Ug Oh.

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At the same time, the main I and additional 14 elements EXCLUSIVE 1SPI, connected to the second delay element 7, having taps at the clock interval T, test their 45 outputs with test signals which, in the absence of errors, completely coincide with the signals received in the corresponding test channels.

At the same time, at the outputs of the EXCLUSIVE-DULYU elements, two combinations of one O are appearing in the EXTENDANT OR SINGLE OR 13 element in the test channels. In the case of a single character failure in the information channel 2 and no-ss signals, the signals errors of the form: in the main test channel 9 - 0011, in the first test canape - 0111

22. A correction symbol with a signal error allows to eliminate the appearance of false errors in the test channels that occur when characters are missing in the information channel separated by a small number of clock intervals. Dp pov11eki accuracy of the device all the elements of the delay

and in the second test channel, 1111. The error of the information signal is detected using decoders 18. In view of this.

that the probabilities Pg of the occurrence of errors in the test channels with 2T, 3T, and 4t delays are different, the shaper coefficients 19 are introduced. The signals generated by them are proportional to the average probability of error in the corresponding channels. In the case of independent errors in the test channels, the probability of Royen detecting an error is

ovi. Thus increasing the number

The check marks increase the likelihood of detecting errors in the information signal.

Error correction signals from the outputs of the test channels are fed to the adder 15, and then to the decision block 16. When the threshold is exceeded, a control signal is generated.

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the symbol of the information signal by acting on the second input of the output element UNSOLVING OR 8. With a fixed threshold of the decision block 16, the formers of the 19 weight coefficients allow to obtain two decision algorithms. In the first algorithm, the error is fixed when it is detected in all the test channels, and in the second, the error is fixed in a majority way, i.e. when it is detected by most check channels.

At the same time, the correction signal from the decision block 16 enters the elements SPARE OR 22 blocks 20 of the delay and signal correction (Fig. 2) of all the check channels. In each test channel, the EXCLUSIVE OR 22 element is included between (n-k) and (n-k + l) delay elements 21, which is due to the difference in the structure of the error signals, as already mentioned above. Addition by clap two in the element SPARKING OR

22. A correction symbol with an error signal allows to eliminate the appearance of false errors in test channels that occur when characters in the information channel are broken, separated by a small number of clock intervals. Dp pok11eki accuracy of the device all the elements of the delay

They can be clocked and synchronized by a clock synchronization unit connected to the input of the device or to the output of the phase detector 5 of the I-channel 2.

As the simulation has shown, the probability of errors in the information signal with three test channels (as compared with the prototype having one test channel) decreases; about 2 times in the area of small signal / shzga relations,

Claims (1)

Formula Invention A device for demodulating signals with a minimum shift manipulation, containing the main element of an IC1CO101CEE OR, an information channel consisting of serially connected phase shifters, a first delay element, a phase detector, an information signal generator, a second delay element, and an output element EXCLUSIVE SH and the main test channel, consisting of series-connected delay element, phase detector, shaper of the test signal and the ORDER element, in the second input is connected to the output of the EXCLUSIVE OR main element and is the first input of the main test channel, the second and third inputs of which are respectively the input of the delay element and the second input of the phase detector, the second and third inputs of the main verification channel and the second the input of the phase detector of the information channel is connected to the input of the device, the first input of the main element EXCLUSIVE 1 BUS is connected to the output of the information signal generator, and the output of the output channel SPEAKER of the information channel is the output of the device, characterized in that, in order to increase the noise immunity, additional connected elements EXCLUSIVE OR, consecutively connected adder and decisive unit and additional Bepo4iuie channels are introduced into it, and in each test channel entered sequentially connected decoder and form-. The weighting factor and the delay and correction unit, the information input of which is connected to the output of the EXCLUSIVE OR element, the inputs of the decoder are connected to the outputs of the delay and correction signal, whose control input and output of the weighting factor are the control input and the test channel output The inputs of the adder are connected to the outputs of the check channels, the output of the decision block is connected to the second input of the output element EXCLUSIVE OR, and the control the inputs of the check channels, the outputs of the Additional elements EXCLUSIVE OR are connected to the first inputs of the corresponding additional test channels, while the output of the main element EXCLUSIVE OR is connected to the first input of the first additional element EXCLUSIVE OR, the corresponding outputs of the second delay element of the information channel are connected to the second inputs of the main and additional EXCLUSIVE OR elements, the outputs of additional elements EXCLUSIVE OR are connected to the first inputs of the corresponding olnitelnyh parity channel, the second and third inputs of odd parity iyh additional channels are respectively connected to output and input of the phase shifter informa- | insulating channel, and the second and third inputs of the even parity additional channels are combined with the input device. Iff sr ff -f -rt Compiled by V. Zenkin Editor A. Revin Tekhred O. Gorta au Corrector L. P Lipenko Order 2662/58 Circulation 624 Subscription VNIIPI USSR State Committee. for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 "UMtJ