SU455351A1 - Device for simulating a digital signal transmission path - Google Patents

Description

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The proposed device relates to the field of computer technology and can be used, in particular, for analyzing the noise immunity of various transmission systems, reception and processing of digital signals.

A device for simulating a digital signal transmission path is known by phase-pulse modulation of the leading and trailing edges of the input signal. The device consists of a generator of pseudo-random sequences of impulses, including the p-cascade shift register, connected through a block of the modular floor with a block of binary adders. The generator outputs are connected to the inputs of the noise voltage shaping unit, the outputs of which are connected to the control inputs of the phase pulse modulation unit, consisting of the front and rear edges of the signal and the output trigger, the output of the device as a whole. The other inputs of the phase-modulation unit of the modulation are connected to the inputs of the input stage, consisting of a differentiating circuit and signal edge detection schemes. The input of the input stage is connected either to the external input of the device or to one of the outputs of the geerator.

However, the obtained pa outputs of such a device, distributing the distortions of the front and rear edges of the signal, do not have ha-acter for real swing paths of the transfer of the groups of front edges of the signal due to different speeds of changing the signal propagation time on the communication channel. Such swings of the front groups take place, for example, when digital signals are not distributed over HF channels, due to the nonstationarity of the ionosphere.

As a result, the device does not provide a sufficiently complete simulation of the real properties of 1 B-paths and the possibilities of using it are limited to 1H for assessing the noise immunity of various transmission systems and digital signals.

The purpose of the invention is to decompose a class of tasks in terms of simulating random time fluctuations of a widespread signal due to the stationarity of the ionosphere in HF communication.

This is achieved due to the fact that in the proposed distribution between the device input and its input cascade, serially connected buffer accumulator and readout circuit are connected, the clock input of which through the sequential control connected1 the 1st divider and the add-exclude unit from the ONE} from geyerator frequency outputs.

The other output of this generator is connected to the inputs of two keys, the outputs of which are connected to different inputs of the add-exclusion unit through the speed shaping unit, and the control inputs of the keys are directly from one, and the other is NOT connected to the sensor output at random time intervals. The input of this sensor is connected to the additional output of the frequency grid generator.

The advantages of this device are the possibility of modeling non-stationary communication channels with randomly varying signal propagation time; good repeatability of the statistical properties of simulated oscillations of the propagation time, which is especially valuable when conducting comparative tests of various digital devices; and the possibility of its use for the technical diagnostics of digital devices sensitive to changes in signal propagation time (for example, digital signal regenerators).

The drawing shows the block diagram of the proposed device.

The device consists of a generator of 1 pseudo-random pulse sequences, the outputs of which are connected through the noise voltage generation units 2 to the inputs of the unit 3 of the phase-pulse modulation. The other two inputs of block 3 are connected to the outputs of the input stage 4. Output 5 of the phase-pulse modulation unit is the output of the entire device.

The input of the input stage is connected in series through the readout circuit 6 and b) the storage drive 7 is connected to the input 8 of the device. The clock input of the readout circuit is connected through a successively connected divider 9 and block 10 for adding and removing pulses to one of the outputs of the frequency grid generator 11. The exclusion inputs are connected to the outputs of the keys 12, whose inputs are interconnected as well as through the adjustment speed shaping unit 13 with the additional output of the frequency grid generator. The control inputs of one key directly and the other through the element are NOT connected to the output of the sensor 14 pseudo-random time intervals, the input of which is connected to the additional output of the frequency grid generator.

The proposed device works as follows.

Non-random and sequential pulses, generated by generator 1, are fed to the inputs of the block of formation of silt stresses, where they are formed and limited by the spectrum. From the outputs of this unit, noise pairs arrive at the inputs of the phase-pulse modulation unit, to the other two inputs of which pulses are applied.

front and rear edges, selected INPUT11Y.M cascade of the digital signal being input to ertj.

In block 3, the modulation is carried out

Froite N1umovye voltage, resulting in its output 5, which is the output of the entire device, produces an output digital signal with random temporal distortions (correlated or uncorrelated) of the leading and trailing edges.

The signal at the input of the input stage comes from the readout circuit 6, which reads the digital signal from the buffer accumulator to

the input of which is connected to the source of digital information. As the latter, both an external digital signal sensor and a pseudo-random sequence generator can be used, connected via a switch to the input of the device.

A clock signal on the input of the readout circuit is supplied from the frequency grid generator via a serially connected controlled divider and a pulse addition / deactivation unit. The inputs of the exclusion and addition of this device through the keys 12 receive a sequence of pulses, the following frequency (determining speed

changing the phase of the clock signal.) can be changed using the trimming speed shaping unit.

The time intervals during which pulses are applied to the inputs of the addition-exclusion of emulsions are interleaved by sensors of a pseudo-random interval. In time, they produce pulses of variable polarity and of various durations. In spite of this, if a positive potential arrives from the sensor, then the right-hand key 12 is activated (both keys open at positive potentials and close when negative), skipping a sequence of pulses from the output of block 13 to the addition input of block 10. These impulses are folded with a comb pulses from a generator of a frequency grid, lead to a phase shift of the clock frequency supplied to the course of the readout circuit, and the speed

the phase shift is determined by block 13, and the value by the duration of the time interval specified by sensor 14.

In the case of the negative potential sensor 14, the right but the diagram

the key 12 is closed, and the left, connected to the output of the sensor, is opened through the NOT 15 element. A sequence of pulses from the output of the current of 13 is supplied on the input of unit II, excludes pulses in

the sequence of the i-generator of the frequency grid, which leads to the opposite phase shift of the clock frequency, and the magnitude and speed of the variables are still determined by the corresponding sensor 14 with block 13.

Thus, the clock signal, with which the circuit 6 reads information from the buffer accumulator to the input of the input stage, receives alternating changes of different speed and magnitude. So, in the wrong way, the digital signal at the output of the device, in addition to the distortion of the leading and trailing edges, has the characteristic ground pulses of code pulses for swing radio channels due to a change in the propagation time of the signal in the communication channel.

This property of the proposed device indicates the expansion of the class of tasks in terms of simulating changes in signal propagation time, due to the nonstationarity of the ionosphere in HF communication channels.

Subject invention

A device for simulating a digital signal transmission path, comprising a pseudo-random pulse sequence generator, connected through noise voltage generation units to one input of a phase pulse modulation unit, to the other inputs of which outputs of a pulse edge selection unit are connected.

the output of the phase-modulation modulation unit is connected to the output of the output unit, (this is because, in order to expand the class of the peeiaMbix task, it contains serially connected buffer accumulators and a readout circuit, the output of which is connected to the input of the selection unit of the pulse fronts, and the input of the buffer connector with the output of the pseudo-random | 51X pulse train sequence and with the input of ycTpoii, connected in series the unit for adding-eliminating pulses and controlling a divider whose output is connected to the second input reading schemes, first

and the second keys, the outputs of which are connected to the first and second inputs of the addition-exclusion pulse unit, the trimming speed shaping unit whose output is connected to the first inputs of the first and second keys, the element "NOT and a pseudo-random time sensor, the output of which is connected to the second input of the first key and through the element "NOT to the second input of the second key, and the frequency grid generator,

the outputs of which are connected respectively to the third input of the pulse addition-exclusion unit, to the input of the trimming speed forming unit, and to the input of the pseudo-random time sensor.