SU1665530A1 - Frequency modulator - Google Patents

Abstract

The invention relates to radio engineering and can be used to generate frequency-modulated signals in various radio devices. The purpose of the invention is to reduce the effective spectral width of the output signals. The frequency modulator contains a voltage source 1, an integrator 2 with a reset, a comparison block 3, a time sampler 4, a memory block 5, a counter 6, a Walsh function generator 7. The introduction of a square wave oscillator 8, a switch 9, a multiplier 10 provides a reduction in the spectrum width of the output signals, which increases the efficiency of using a frequency band. 2 Il.

Description

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ON ON

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The invention relates to radio engineering and can be used to generate frequency modulated signals in various radio devices.

The purpose of the invention is to reduce the effective spectral width of the output signals.

Fig. 1 shows the functional electrical circuit of the frequency modulator; figure 2 - timing charts of the device.

The frequency modulator contains a voltage source 1, an integrator 2 with a reset, a comparison block 3, a time sampler 4, a memory block 5, a counter 6, a Walsh function generator, a square-wave oscillator 8, a switch 9, a multiplier 10.

The frequency modulator operates as follows.

At the moment, the quantizer 4 (Fig. 26) reads the value of the signal at the input of the frequency modulator. The voltage obtained is stored in the storage unit 5 (Fig. 2B). At the output of the integrator 2 (Fig. 2g), a linearly increasing voltage is formed. Comparison unit 3 (Fig. 2d) compares this voltage with the voltage at the output of memory unit 5 and returns the integrator, 2, to its original state, when the voltages are the same. As a result, a sawtooth voltage is formed at the output of the integrator 2. The amplitude and duration of the teeth of this saw are proportional to the voltage at the output of the storage unit 5. From the output of the comparison unit 3, the pulses that return the integrator 2 to the initial state are also fed to the input of the counter 6. At the nth output of the counter (Fig. 2e), where is the number of Walsh function elements generated by the Walsh function generator 7, a pulse appears if 2p pulses are obtained from the comparison block 3. This pulse returns the storage unit 5 to the initial state and writes down a new count of the signal values using the quantizer 4. In this case, the distance between sample points depends on the magnitude of the signal values at times of samples. After generating this pulse, the counter returns to its original state, when all the bits of the counter are reset,

The pulses from the output of the comparison unit 3 also arrive at the clock input of the generator 7 Walsh functions, at the output of which a certain Walsh function is formed (Fig. 2g) arriving at the first input of the multiplier 10.

The pulses from the output of the comparison unit 3 also arrive at the clock input of the rectangular oscillator 8 (FIG. 2h), with the result that the duration of the rectangular pulses at its output is equal to the duration of the Walsh function elements.

The switch 9 is designed so that when a zero potential arrives at its control input, a signal arrives at its output, arrives at the first information input, and when a positive potential arrives at its control input, a signal is generated at its output

arriving at the second information entry. The voltage at the output of source 1 is shown in Fig. 2i.

Since the control input of the switch 9 is connected to the output of the (n − 1) th digit of the counter 8 (FIG. 2d), during the first half-cycle of forming the Walsh function at the output of the generator 7 of the Walsh functions, the rectangular oscillation is formed at the output of the switch 9 and during the second half period on

The output of the switch 9 is formed by a negative voltage (Fig. 2k).

Thus, over a period of time & t, the Walsh function arrives at the first input of the multiplier 10, and the second input of the multiplier 10 receives a signal from the output of the switch 9. As a result, a frequency-modulated output signal is generated at the output of the multiplier 10 (Fig. 2L) .

The output signal system formed by the proposed frequency modulator, as well as the output signal system formed by a known modulator, is orthogonal, which is easily seen by multiplying two signals that are included in

one system.

If all the spectra of the signals entering the system have the same width and occupy the same frequency band, then RShst. F (where Rsist. Bandwidth occupied by the system of signals, F - width of the spectrum of a single signal). With different spectral widths of the RSIST. - the maximum width of the spectrum,

The more blocks a signal has (the block is a sequence of identical elements), the more effective is the width of the signal spectrum.

The output signals described by the Walsh functions have the number of blocks:

1.2 „3N.

Therefore, 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 N 2P (i.e. square wave),

mLeff - / gg :,

where At is the duration of the element.

The output signals generated by the proposed modulator have a number of blocks

, Nn + 2

/ u YM / 1M / 2

and the value of the maximum effective width of the output spectrum, taking into account

N + 2 / and -tu- is determined according to the expression:

"MF-f T.

where Dg - the duration of the signal element; // - number of blocks;

N is the number of elements.

The use of the invention allows the creation of frequency modulators that provide a reduction in the width of the spectrum of the output signals, which increases the efficiency of use of the frequency band.

Claims (1)

Invention Formula A frequency modulator containing a serially connected time directer and a storage unit, as well as a reference voltage source, a reset integrator, a comparator unit and a Walsh function generator, as well as a counter, are connected in series; the output of the comparator unit is connected to the counter input and the integrator installed input with a reset, the output of the nth counter meter is connected to the installed temporary inputs and a storage unit, the output of which is connected to another input of the comparison unit, characterized in that, in order to reduce the width of the spectrum of the output signals, sequentially connected generator Rectangular oscillation and a switch whose other input is connected to the output of a voltage source, as well as a multiplier, one input of which is connected to the output of the Walsh function generator, another input to the output of the switch, the control input of which is connected to the output (n-1) th digit of the counter, wherein the clock input of the square wave oscillator is connected to the output of the comparison unit, and the multiplier output is the output of the device. b about WRITES I AND I I MISHI : i elII l , fl,), Wofft.gtj i U l and TPLP-Ll ./iS. S (5.ei) pi-tt ealt vT1