SU924820A1 - Frequency modulator - Google Patents

Description

(54). FREQUENCY AND MODULE YATOR

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The invention relates to radio engineering and can be used to generate frequency modulated C 11 signals in frequency modulated transmitters.

A frequency modulator is known that contains a master oscillator, the first, second, third and third comparators and a standby generator of a sawtooth, the output of which is connected to one of the inputs of the first comparator, this is the second input of the first comparator and one of the inputs of the second comparator The connections and their connection point is the input of the modulating signal of the frequency modulator 113.

However, in the frequency module tqpe constant is impossible (or an arbitrarily long time} frequency shift by any value, i.e. it has a limit on the lower modulating frequency.

and (spruce of the invention is the extension of the range of modulating frequencies.

To achieve the goal, a frequency modulator containing a master oscillator — the first, second, and third comparators and a standby sawtooth generator, the output of which is connected to one of the inputs of the first comparator, first of all the second input of the first comparator and one of the inputs of the second comparator are combined and their connection point is the input of the modulating signal of the frequency modulator, the first OR element is introduced, one input of which is connected to the output of the first compressor, the other input is connected to the output of the third comparator, and the output is connected to resetting the standby generator of the sawtooth voltage, the first and second sources onqpHoro nash, the outputs of which are connected respectively to the input of the second comparator and to one of the inputs of the third computer ,. follow up the first controllable key, whose input input is connected to the output of the second comparator, and

the second OR element, the second input of which is connected to the output of the first OR element, and between the output of the master oscillator and the input (starting the standby generator of the sawtooth voltage, we connected a series-connected counter, the input of the zero setting which is connected to the output of the first OR element, and the second controlled key , the control input of which is connected to the output of the second comparator, while the input of the first controlled key is connected to the output of the counter, the second input of the third comparator is connected to the output of the waiting saw generator shaped voltage, and the output of the second OR gate is the output of the frequency modulator.

FIG. Figure 1 shows the structural electrical circuit of the frequency modulator; in fig. 2 - timing charts of the device.

The frequency modulator contains master oscillator 1, counter 2, first and second fixed keys 3 and 4, first, second and third comparators 5-7, first and second sources 8 and 9 of the reference voltage, first and second elements OR 10 and waiting a generator 12 is a pie voltage.

The frequency modulator operates as follows.

The device produces a modulation of the period of follow-up of the output pulses by changing the period (frequency) of the following pulses of a saw-tooth voltage.

The follow-up period of the output impulses is defined as the sum of the constant period of the pulse following the output of the counter 2 () and the variable duration of the sawtooth pulse 1 DT (Fig. 2). The pulse period at the output of counter 2 determines the maximum frequency equal to; ; .Uo,

where (5 is the frequency of the input signal of the high-frequency master oscillator 1;

MQ is the capacity of counter 2 (division ratio), which, after counting the NO pulses, goes to the initial

zero state and starts a new counting cycle.

Transfer (reset) to the zero initial state can be carried out externally at the input. Setting zero.

The duration of the servo voltage following period is a function of the instantaneous value of the modulus

This is because the device is actually using the comparator 7 to produce pulse-width modulation of the saw blade. Comparator 5 for Breaking oscillations (increase of the saw) when the saw-tooth voltage reaches the maximum level (in time JTC since the start of the saw). This saw amplitude and, consequently, the duration D T c is established by the displacement magnitude from source 9. Comparator 5 generates reset pulses at the input of element OR 10 within the range of the saw voltage variation from zero to maximum, or from the lower to upper saw voltage value Therefore, if the level of the modulating voltage is above the lower threshold limit (in Fig. 2 is above zero), the comparator generates a reset pulse within a change in the modulating value from zero to the maximum saw voltage. The duration of the saw is

About DT yT „.

If the modulating voltage exceeds the voltage of the saw, then the pulse of resetting the saw fails the comparator 7 ,. The generator 12 breaks the oscillations through the element OR 1O either from the pulses of the comparator 5, or from the pulses of the comparator 7, depending on the ratio of the amplitudes of the modulating signal and the saw voltage. In general, the period of the output pulses of the device will be equal to Tg, j (Tp + 4T UMOAlt), Unt-t) j and, therefore, the frequency of short pulses

UL.bykh-G (,, T, 4- / inu o (t),

The frequency modulator has three sections of modulation characteristic (Fig. 2), linear and with upper and lower deviation constraints.

The upper limit on the deviation (lower portion of the characteristic) is as follows.

If the instantaneous value of the modulating signal 0 is less than the specified threshold limit below (the threshold is set by the signal from source 8 to the input of the comparator G}, then the comparator 6 generates a potential that opens key 3 and closes key 4. The start input of generator 12 is disconnected from the output of counter 2 and geerator 12, comparator 5 n comparator 7 are not involved in the work. Counter 2 works, output pulses with a follow-up period - NQ through the public key 3 and the OR 11 element arrive at the device output. On you, the modulator stroke through the OR 11 element 11 The following signals occur: Impulse resetting the saw from the output of the element OR 10, which is an external impulse to reset the counter 2, i.e. setting the counter 2 to the zero state. This impulse is generated in the interval of change of the modulating voltage exceeding the lower level threshold limit at the time of coincidence of the saw and the modulating signal voltage. Output reset pulse. Counter 2 used in: inside the counter circuit to set it to the zero state (reset) after filling it NQ number of pulses. This pulse enters through key 3, the open output voltage of the comparator 6, when the value of the modulating voltage is below (or equal to) the lower threshold limit (in Fig. 2, below zero). When the value of the modulating voltage is above the lower threshold of the limitation, the key 3 is closed and the internal reset pulse of the counter 2, determined by filling the counter, is not fed to the input of the element OR 1. Counter 2 is reset, zeroed by this impulse inside and begins to fill up again. At the same time, a generator 12 is started through the public key 4. When the saw blade reaches the modulating voltage level, the comparator 5 is triggered, its V-code pulse through the OR element 1O through the external input of the zero setting embeds the counter 2, at the same time this impulse enters the element input OR 11 This level of Eg (Fig. 2) triggered by the magnitude of the mixing nag from source 9 and in principle can be adjustable. If the modulating nagging is greater than the saw voltage, then when the maximum is reached, determined by the offset from source 9, the saw is broken by a pulse from the output of the comparator 7. This pulse element OR 10 will reset the counter 2 and will simultaneously arrive at the input of the element OR I. Medium UQ, i.e. if the modulating signal is zero, the saw duration will correspond to the average frequency will be: P Thus, the maximum duration of P1ShY is set by the offset from source 9 at the input of the comparator 7. The threshold for the limiting of the saw level in amplitude from above corresponds to the duration of the saw dT and the frequency of the follow-: shsh pulses will correspond to the lower frequency of the frequency To + dt will be formed if the instantaneous value of the modulating signal is greater than the maximum value of the saw. This mode provides a limitation of the deviation of the frequency deviation down. Thus, in the proposed gravitational modulator, the frequency cwig is formed at an arbitrarily low frequency up to a constant, long-term, i.e. modulator frequency and amplitude response provides low frequency transmission, up to direct current. Thus, in the proposed device, the output oscillations are excluded, and the frequency response is expanded to zero frequency, which allows for a long-term frequency shift from the carrier nominal. The device conducts frequency manipulation (frequency response) by constantly accurate visits of arbitrarily long duration without normalizing the level of the manipulation signal, the corresponding signal sending and pauses were outside the linear portion of the modulation characteristic (Fig. 2), i.e. . more Ela and less EQF O p mule of the invention Frequency modulator containing a master oscillator, first, second and third comparators and a standby sawtooth generator voltage, the output of which is connected to one ns inputs of the first comparator, U) the second input of the first compressor and one of the inputs of the second comparator is combined, and their connection point is the input of the modulating signal of the frequency modulator, characterized in that, in order to expand the range of modulating frequencies, the first OR element is introduced into it, one input of which one with the output of the first comparator, the other

Bypass - to the OUT of the third comparator, and the output is connected to the reset input, which is waiting for the sawtooth generator, the first and second sources are located on the 15) gate1, the outputs of which are connected respectively to the second input of the second comparator and one of the inputs of the third comparator, connected in series to the first utfl key, the control input of which is connected to the output of the second comparator, and the second element OR, the second input of which is connected to the output of the first element OR, and between the output driving the generator and the start input In the standby sawtooth generator, serially connected meters are introduced, the setup input zero of which is connected to the output of the first OR element, and a second control key, the control input of which is connected to the output of the second comparator, and the input of the first control key is connected to the output of the counter, the second input of the third comparator is connected to the output of the standby sawtooth voltage generator, and the output of the second battery OR is the output of the frequency modulator.

Sources of information, gfinye into account during the examination

1. Pathe- USA N ZI1633, cl. 332-23, published. 1960 (prototype).

Claims (1)

Claim A frequency modulator containing a master oscillator, first, second and third comparators and a waiting sawtooth generator, the output of which is connected to one of the inputs of the first comparator, while the second input of the first comparator and one of the inputs of the second comparator are combined, and their connection point is the input of the modulating frequency modulator signal, characterized in that, in order to expand the range of modulating frequencies, the first OR element is introduced into it, one input of which is connected to the output of the first comparator, another the first input is with the output of the third comparator, and the output is connected to the reset input, which is waiting for a sawtooth generator, the first and second sources of reference voltage, the outputs of which are connected to the second input of the second comparator and one of the inputs of the third comparator, respectively, connected in series to the first a controlled key, the control input of which is connected to the output ^{of the} second comparator, and the second OR element, the second input of which is connected to the output of the first OR element, and between the output of the generator and the input behind serially connected counter, the input of the Zero setting of which is connected to the output of the first OR element, and the second controlled key, the control input of which is connected to the output of the second comparator, the input of the first controlled key connected to the output of the counter, the second input the third comparator is connected to the output of the waiting sawtooth voltage generator, and the output of the second OR element is the output of the frequency modulator.