SU440798A1 - Device for automatic channel selection - Google Patents

Description

one

The invention relates to radio engineering, in particular, to a technique for receiving signals in communication systems with diversity reception using asynchronous demodulation methods.

A known device for automatic selection of a channel or a branch of diversity with the smallest signal distortions under the conditions of action of various additive and multiplicative.

In the known device, the automatic selection of a channel or a branch of the diversity with the smallest signal distortions under the conditions of action of various additive and multiplicative devices, which uses asynchronous modulation methods, realizes the energy criterion when the decision on choosing a channel is made by comparing the signal energy of the signal and interference present in each channel.

The known device contains a common linear path connected in parallel to the inputs of three diversity channels, each of which contains a channel filter and an asynchronous demodulator connected via a channel key to an adder, the output of which is the output of the device for automatic channel selection, each asynchronous demodulator connected through a conversion unit to a comparison unit whose outputs correspond to a given channel.

through the decision block connected to the channel keys.

However, the known device has a lack of reliability and noise immunity.

The aim of the invention is to improve the reliability and noise immunity of the device.

For this, the conversion unit contains three identical paths connected by inputs and outputs to the corresponding channel inputs and outputs of the conversion unit; in each path of the conversion unit, a double-sided limiter, a first differentiating chain and its first input and output are first connected to the second input through which the output of the double-sided limiter is connected via the NOT circuit and the second differentiating chain, the comparison block contains a Tpi version of the counter, and

the first channel input of the block C is keyed to the first input of the revue of the first channel and to the active counter tert the second second channel

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comparison is connected to the first input of the reversible counter of the third channel and to the second input of the reversible counter of the second channel, the decision block contains the first trigger, the first and second inputs of which are connected respectively to the pair of inputs of the decision block corresponding to the first channel, and the first output of the first trigger is connected in parallel to the first the inputs of the first and second circuits "And, to the second inputs of which are connected, respectively, the first and second outputs of the third trigger connected to the first and second inputs to a pair of inputs the decision block corresponding to the third channel, the output of the first circuit “And connected to the second input of the third channel key, the second circuit“ And its output connected through the first input and output circuit “OR the decision block to the second input of the second channel key, the second output of the first trigger connected in parallel to the first inputs of the third and fourth circuits “And, to the second inputs of which, through the first inputs and outputs and the second inputs and outputs of the second trigger, respectively, are connected a pair of inputs of the decoupling unit corresponding to the second one Nala, the output of the third circuit "and connected to the second input of the first channel key, and a fourth output circuit" and a second input connected to circuit "or casting unit.

The invention is illustrated in the drawings.

FIG. 1 shows a block diagram of the device; in fig. 2 - diagrams of signals at the outputs of the corresponding elements of the block diagram.

The device for automatic channel selection contains three blocks — a conversion block, a comparison block, and a decision block.

The conversion unit contains three identical paths, each of which consists respectively of two-sided terminators 1, 2, 3, the first differentiating chains 4, 5, 6, the second differentiating chains 7, 8, 9, the schemes "NOT 10, 11, 12, the first schemes “OR 13, 14, 15.

The comparator unit contains three reversible counters 16, 17, 18.

The decisive block contains triggers 19, 20, 21, And 22, 23, 24, 25 schemes and a second OR 26 circuit. In addition, the channel switches 27, 28, 29, the adder 30, the radio receiver 31, the channel filters 32 , 33, 34 and asynchronous demodulators 35, 36, 37.

With this device, the automatic selection of the channel or branch razieseni occurs at the highest signal-to-noise ratio.

The device works as follows.

The signal from the receiver 31 through the channel

filters 32, 33, 34 that separate the spectra of frequency-separated signals (AT, TH,

The FRL1, and so on) goes to the inputs of the asynchronous module 35, 36, 37, to the outputs of the circuit of the circuit of the conversion unit into a continuous unipolar sequence of short pulses.

Signals from demodulators (see Fig. 2, a, b, c) are sent to double-sided stops I, 2, 3, limited by them and fed to the first differentiating chains 4, 5, 6 and the "NOT (inventory) 10, 11 , 12, after the injection, they arrive at the second differentiating chains 7, 8, 9.

The outputs of the differentiating chains of the conversion circuit of each channel are respectively combined with the circuits OR 13, 14, 15. Two differentiation chains are needed in order to determine zero intersections of the signal distorted by interference in both positive and negative directions, since this increases by two times the number of intersections per unit of time, which allows to increase the resolving power of the entire instrument and reduce its inertia.

Positive pulses corresponding to zero intersections of the signals at the output of the demodulators from the outputs of the converter unit are fed to the corresponding inputs of counters 16, 17, 18. Entering the reversible counters 16, 17, 18 into the comparison unit allows to calculate the current difference in the number and pulse from two channels (averaging over a sliding time interval). As soon as the difference in the number of pulses exceeds the capacity of the reversible counter, a signal is immediately generated that determines which of the compared channels is better than the quality of the transmitted information.

The best of the two channels will be the one for which the algebraic difference of the number of zero crossings is negative. It does not require a special time interval sensor, and the beginning of the counting and resetting of readings in the reversing counter occurs automatically. At the moment that the installed capacity of the counter is exceeded, the comparison unit forms a single short pulse arriving at the input of the decision unit.

The state of triggers with separate start 19, 20, 21 reflects the result of comparing the channels. Channel switches 27, 28, 29, to which signals are sent from the output of the demodulators, are switched by the output signals, respectively, coming from the schemes "AND 25," OR 26, "And 23.

The decision block works as follows.

If the first channel is better than the second, then the channel key 28 is switched to the closed state; the final decision is made when comparing the first and third channels, if the first channel is worse than the second, then the key 27 is transferred to the closed state; however, the final decision is made when comparing only the second and third channels.

Let the initial state of the control triggers be 19, 20, 21 "unit at outputs 38, 39, 40 and" zero at outputs 41, 42, 43 (see

FIG. 2, 3, k, m), where the state "zero" corresponds to a higher potential. All circuits # 22, 23, 24, 26 are opened when a voltage is applied to both inputs corresponding to the state "zero. The key 28 is then closed by the output voltage of the circuit "AND 22 through the circuit" OR 26, and the keys 27 and 29 remain open.

If the first channel becomes better than the second, and the second is better than the third, then at the time point i, the overflowed counter 18 knocks over flip-flop 21 (see Fig. 2, l, m, n). The flip-flop 21 goes to the "zero" state at output 39 and a positive voltage is applied to the input of the < 25 > circuit. The scheme “And 25 is closed at another entrance. Circuit & 24 is additionally closed on input 39. The state of all other circuits remains unchanged.

At time 4 after the overflow of the counter 16, flip-flop 19 (see FIG. 2, g, h) overturns and the output 38 goes to the “zero” state. This closes the ' 22 scheme, and opens through the " OR 26 channel key 28 < / RTI > At the same time, the & 25 scheme is fully opened and closes the channel key 27.

Thus, at time 4 and the input of the adder 30, instead of the third channel of the receiver, the first channel is connected. At times tz, t, the first channel is confirmed to turn on and the channel is not switched.

If the second channel becomes better than the first, but worse than the third, in this case the circuits And 24, 25 are closed by exit 38, the opener is the channel key 27, and the circuits And 22, 23 are opened by exit 38. At the same time, the circuit 23 And closes by exit 39, and the AND circuit 22 is opened by the output 39, thereby through the circuit OR 26, the key 28 closes.

Subject invention

Device for automatic channel selection for communication systems with diversity reception for asynchronous demodulation methods, comprising a common linear path connected in parallel to the inputs of three diversity channels, each of which contains a serially connected channel filter and an asynchronous demodulator connected by its output through the first input and the output of the channel key to the corresponding input of the adder, whose output is the output of the device for automatic channel selection, each asynchronous demod l torus connected via the corresponding input and the corresponding output unit converting to the corresponding channel entry comparing unit, each pair of

whose outputs corresponding to this channel, in turn, through each pair of inputs and output of a decision unit corresponding to the given channel are connected to the second input of the channel key, characterized in that, in order to increase reliability and noise immunity, the conversion unit contains three identical paths connected the inputs and outputs to the corresponding channel inputs and outputs of the conversion unit; in each path of the conversion unit, a two-way limiter is connected in series, the first differentiating circuit of the first input and output of the first OR circuit, to the second input of which through the NOT circuit and the second differentiating chain the output of the two-way limiter is connected, the comparison block contains three reversible counters, and

the corresponding first channel input of the comparator unit is connected to the first input of the reversible counter of the first channel and to the second input of the reversible counter of the third channel, the corresponding second input of the comparison unit is connected to the first input of the reversible counter of the second channel and the second input of the reversible counter of the first channel, and the corresponding the third channel input of the comparison unit is connected to the first input of the reversible counter of the third channel and to the second input of the reversible counter of the second channel, decisive the block contains the first trigger, the first and second inputs of which are connected respectively to a pair of inputs of the decision block corresponding to the first channel, and the first output of the first trigger is connected in parallel to the first inputs of the first and second circuits "And, to the second inputs of which the first and second outputs are connected, respectively a trigger connected via the first and second inputs to a pair of inputs of the reacting unit corresponding to the third channel, output with the cxcMiji “perk And connected to the second input

The third channel key, the second circuit “And its output is connected through the first input and output of the circuit“ OR the decision block to the second VHO.DU of the second channel key, the second output of the first trigger and the keys in parallel to the first inputs of the third and fourth circuits “And, to the second inputs of which through the first inputs and outputs n the second inputs n outputs of the second trigger, respectively, a pair of inputs of the decision block corresponding to the second channel is connected, the output of the third circuit “AND connected to the second input of the first channel switch, and the output of the fourth circuit s "and is connected to the second input circuit" or casting unit.

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