SU1758893A1 - Code modulator - Google Patents

Abstract

SUMMARY OF THE INVENTION: The modulator comprises a Walsh 1 function synthesizer consisting of a master oscillator 2, a Walsh 3 function generator and a frequency divider 4, a number sequence generator 5, a digital switch 6. a constant voltage source 7, a key block 8, a frequency divider 9, and keys 10. 5 Il .. 1 tab.

Description

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The invention relates to radio engineering and can be used for code modulation of signals in various radio engineering devices.

A device for amplitude modulation is known comprising a source of modulating signals, a differential amplifier, an amplitude modulator, an amplitude detector, an adjustable attenuator, and a correction signal driver.

However, the known device modulates a harmonic carrier and cannot modulate a discrete carrier.

The closest in technical essence to the invention is a code modulator comprising a Walsh function synthesizer, a numerical sequence generator, a digital switch, a constant voltage source and a key block, the first clock output of the Walsh function synthesizer being connected to the clock input of the generator the output of which is connected to the control input of the digital switch, the output of which is connected to the first input of the key unit, the input interface of which is connected to the output of the source post voltage, while the Walsh function synthesizer contains a Walsh function generating unit, a frequency divider and a master oscillator, the output of which is connected to the clock input of the Walsh function generating unit and the clock divider input, the output of which is the first clock output of the synthesizer, the second clock the output of which is the output of the master oscillator, the outputs of the Walsh function generating unit are information outputs of the synthesizer and are connected to the corresponding information inputs of the digital clock. mutator key block output is the output code of the modulator.

However, the output signals generated by the code modulator have a large effective width of the spectrum, which leads to a low bandwidth efficiency, i.e., to a deterioration in the performance characteristics of the code modulator.

The aim of the invention is to reduce the width of the spectrum of the output signals.

The goal is achieved by the fact that a known code modulator containing a Walsh function synthesizer, the first clock output of which is connected to a clock input of a number sequence generator, the output of which is connected to

the control input of the digital switch, the output of which is connected to the first input of the key unit, the second input of which is connected to the output of the constant source

voltage, while the Walsh function synthesizer contains a Walsh function generating unit, a frequency divider and a master oscillator, the output of which is connected to the clock input of the Walshe function forming unit and the frequency divider with a clock input, the output of which is the first clock output of the synthesizer, the second clock output which is the output of the master generator, the outputs of the block

The 5 Walsh function shaping functions are the information outputs of the synthesizer, the keys and the additional frequency divider are introduced, the output of which is connected to the control inputs of the keys, the information inputs of which are connected to the corresponding information outputs of the Walsh function synthesizer, the second clock output of which is connected

5 outputs of keys are connected to the corresponding information inputs of the digital switch.

Figure 1 shows the block diagram of a code modulator; figure 2 - key structure diagram; Fig. 3 shows timing diagrams illustrating the process of generating the output signal L (6, в) in the proposed code modulator; figure 4 - view of the signals at the output of the prototype; figure 5

5 shows the signals at the output of the proposed code modulator.

The code modulator contains a Walsh function synthesizer 1, consisting of a master oscillator 2, a formation unit 3

0 Walsh and divider functions 4 frequencies, 5 numerical sequence generator, digital switch 6. constant voltage source 7, key block 8, additional frequency divider 9, keys

5 10.

Each key consists of the element NOT 11, the first multiplier 12, the second multiplier 13 and the adder 14

The code modulator operates as follows.

From the beginning of the arrival of pulses from the output of the master oscillator 2 to the input of the divider 4 frequency, which has a deposition factor of 2P, the modulating number sequence g (t) is formed at the generator 5 output in the 5th sequence. Since the division ratio of the 4 divider frequency is 2P, each symbol of a numerical sequence corresponds to one period of the Walsh functions generated at the outputs of the Walsh function generating unit 3, the clock input of which receives a sequence of pulses from the output of the master oscillator 2.

The pulses from the output of the master oscillator 2 are also fed to the input of the additional frequency divider 9, which has a division factor. Thus, during the first half-period of the formation of Walsh functions, the output of the additional frequency divider 9 is generated. O arrives at the control inputs of the keys 10. During the second half-period of the formation of the Walsh functions, the output of the additional frequency divider 9 is generated 1, key inputs 10.

The keys 10 function as follows.

When a key 10 O arrives at the control input, a signal is generated at its output, which arrives at its first information input, and when it arrives at the control input of a key 10 1, a signal arrives at its output, which arrives at its second information input.

Thus, when a key 10 O is received at the control input Z (see FIG. 2), the input element NE 11 and the first input of the second multiplier 13 are received by O. As a result, the signal arriving at the first information input xi of the key 10, through the first multiplier 12 and the adder 14 is fed to the output of the key 10. The signal received at the second information input X2, does not arrive at the output of y, since the first input of the second multiplier 13 enters O from the input z of the key 10.

When a key 10 1 arrives at the control input z, the input element NO 11 and the first input of the second multiplier 13 arrive 1. As a result, the signal arriving at the second information input X2 of the key 10, through the second multiplier 13 and the adder 14 enters the output of the key 10 The signal arriving at the first information input xi of the key 10 does not arrive at the output y, since the first input of the first multiplier 12 receives 0 from the output of the element NOT 11.

Thus, during the formation of one symbol of the modulating sequence g (t) at the output of the generator. 5 numerical sequence, functions are formed at the outputs of keys 10

L (0, in L (1,6) L (2n-1. 0) with a duration of

one period.

Alphabet generator 5 numerical sequence consists of 2P characters.

Digital switch 6 generates at the output of that function L (i. C), the sequence number of which corresponds to the alphabet character, the incoming control input of switch b from generator 5, a numerical sequence of yogty.

The constant voltage source 7 and the key block 8 perform the functions of an L (i. C) signal amplifier to the level necessary for the radiation.

Fig. 3 shows temporary diagrams illustrating the process of forming the output signal L (6, 0} in the proposed code modulator.

The diagrams show the time status:

and the output of the master oscillator 2;

B of the seventh output of the Walsh function formation unit 3, on which the function Wa (6, 0) is formed:

c) a second output of the Walsh function generation unit 2, on which the function Wai (1,) is formed;

d) the output of the additional frequency divider 9;

e) the output of the seventh key 10, on which the function L (6, 9) is formed.

Figure 4 shows the Walsh functions generated by the prototype. Figure 5 shows the orthogonal functions L (i, 0) formed by the proposed code modulator.

The orthogonality of the signals generated by the proposed code modulator can be verified by multiplying any generated functions.

For undistorted transmission of signals generated by the modulator, it is necessary to provide a frequency band for transmitting the wideband signal itself.

In a code modulator, received as a prototype, output signals are generated, described by Walsh functions (see FIG. 4).

It is known that the more blocks a signal has (a block is a sequence of identical elements), the more effective is the spectral width of the signal L / „EFF

The output signals described by the Walsh functions have the number of blocks / g 1,2,3M (Fig. 4),

Consequently, the output signals generated by the prototype have a different effective width of the spectrum, while the maximum effective width of the spectrum has an output signal, which has the number of blocks fi 2 N (i.e., square wave)

BUT

At

ifl-f 2N

(one)

where At is the duration of the element.

The output signals generated by the proposed device have the number NN + 2

fi blocks

- or fi

- and meaning

the largest effective width of the spectrum

N 4-2 output signal taking into account / and - --- op2

done according to the expression

IIF-SHU

(2)

where At is the duration of the signal element;

f.i is the number of blocks;

N is the number of elements

According to the general principles of information theory, each m-ary symbol (where m is 2P) carries n (092 m binary units, i.e., a m-ary symbol is equivalent to a code sequence of n binary symbols. The duration of an m-ary symbol can be determined from ratios

logam R

(3)

where R is the information transfer rate.

From relation (3) it follows that the information transfer rate is defined as

R- lQ92m to,

I m

(four)

Thus, for a given volume of the alphabet m 2 and a given transmission rate R, the duration Tt of the prototype code sequence is equal to the duration Tt of the code sequence of the proposed code modulator.

The table shows the data for calculating the maximum effective width of the spectrum for the output signals generated by the prototype and the proposed code modulator for the case

Tm Tj 1, (5)

those. at the same information transfer rate and a given volume of the alphabet, the output signals generated by the proposed code modulator have a smaller spectrum than those generated in the known device,

As follows from the table, the output signals generated by the proposed code modulator have a spectrum width smaller than the signals generated by the prototype, with the same information transfer rate and alphabet volume m 8 by 27%, alphabet volume m 32 - by 28%, alphabet volume m 64 - by 29%, etc.

The use of the invention allows the creation of code modulators that reduce the width of the spectrum.

output signals, which increases bandwidth efficiency.

Claims (1)

The code modulator containing the Walsh function synthesizer, the first clock output of which is connected to the clock input of the number sequence generator, is output connected to the control input of the digital switch, the output of which is connected to the first input of the key block, the second input of which is connected to the output of the constant source voltage, while the Walsh function synthesizer contains a Walsh function generating unit, a frequency divider and a master oscillator, the output of which is connected to the clock input block the formation of the Walsh functions, and with a clock input frequency divider, the output of which is the first The clock output of the synthesizer, the second clock output of which is the output of the master oscillator, the outputs of the Walsh function shaping unit are information outputs of the synthesizer, characterized in that, in order to reduce the width of the spectrum of the output signals, the keys and the additional frequency divider, whose output is connected to the control key inputs, the information inputs of which are connected to the corresponding information outputs of the Walsh function synthesizer, the second clock output of which is connected to the input of the additional frequency divider, and 0 key outputs are connected to the corresponding information inputs of the digital switch FIG. J a) . Figz  WJ (6, e) Wai (e) L (6, ej