SU1241451A1 - Demodulator of width-modulated signal - Google Patents

Abstract

The invention can be used in multi-channel information processing and transmission systems, as well as for demodulation of signals with pulse-width modulation (PWM) and variable pulse repetition period. The purpose of the invention is to improve the accuracy of demodulation of signals from PWM is achieved by adjusting the result of demodulation with a change in the repetition period of the signal. For this purpose, differentiating elements 1 and 3, one-shot 2 transfer and one-shot 4 reset are introduced into the demodulator. The device also contains key elements 5, 7, 19, and 22, capacitors: storage 6, memory 9 and 23, emitter followers 8 and 21, controlled constant current source 10, Tiny: input II, output 12, coincidence element 13, integrator 14 , a one-shot 15 delay, a differentiating element 16, a one-shot 17 correction, an element 18 OR-NOT, a current stabilizer 20. The introduction of these new elements into a demodulator of signals with PWM and new connections has made it possible to improve the accuracy of demodulation of signals in the presence of spurious frequency module ii. 2 Il. (L 1C NU 4 recounted

Description

The invention relates to a pulse technique and can be used in multi-channel information processing and transmission systems, for demodulating signals with pulse-width modulation and a variable pulse repetition period.

The purpose of the invention is to improve the accuracy of the demodulation of a pulse-width signal by correcting the demodulation result with changes in the repetition period of the signal.

FIG. I shows the functional diagram of the demodulator of the width-modulated signal; in fig. 2 - time diagrams of his work.

The demodulator of a width-modulated signal contains differentiating element 1, one-shot 2 overwrites, differentiating element 3, one-shot 4 reset, key element 5, storage capacitor 6, key element 7, emitter follower 8, storage capacitor 9, controlled source 10 stabilized current, input busbar 11, output bus 12, coincidence element 13, integrator 14, delay one-shot 15, differentiating element 16, correction one-shot 17, OR-NOT 18 element, key element 49, current stabilizer 20, emit The black repeater 21, the key element 22, the storage capacitor 23, between the input bus 11 and the control input of the key element 5 are connected in series differentiating element 1, one-shot 2 rewrites, differentiating element 3 and one-shot 4 reset, between the power supply buses and the common the bus includes connected in series controlled source 10 of stabilized current and storage capacitor 6, in parallel with which key element 5 is connected, between the output of the differentiating element and I and the first input of the element OR NOT 19 include a delayed one-shot 15, a differentiating element 16 and a correction one-shot 17, the control input of which is connected to the combined terminals connected in series and connected between the output of the emitter follower 21 and the common bus of the key: element 22 and memory capacitor 23, and the control input of the key element 22 is connected to the output of the one-shot 15 delay and the second input of the element OR NOT 18, the output of which is connected to the control input to A secondary element 19, the output of which is connected via a current stabilizer to a common bus, and the input is connected to the input of the emitter follower 21, the output of a controlled constant current source 10 and the input of the integrator 14, the reset input of which is connected to the output of the single-vibration 4 reset, and the output to the input emitter

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a repeater 8, between the output of which and the bus, connected in series are the key element 7 and the storage capacitor 9, the combined outputs of which are connected to the output bus 12, and the control input of the key element 7 is connected to the output of the one-shot 2 rewriting and the inverting input of the coincidence element 13 The noninverting input of which is connected to the input bus 11, and the output to the control input of the controlled source 10 of a stabilized current.

The demodulator of the width-modulated signal works as follows.

The positive front of the next input pulse (Fig. 2 a) through the differentiating element 1 triggers a single-vibrator 2 rewriting, which produces a rewriting pulse of a few microseconds duration (Fig. 26). The negative edge of the rewrite pulse through the differentiating element 3 triggers a one-shot reset 4, which produces a short reset pulse (Fig. 2c). The reset pulse opens the key element 5, through which the storage capacitor 6 is discharged to zero voltage. The input positive pulse simultaneously arrives at the non-inverting input of the element 13 coincidence, the inverting input of which receives a positive rewrite pulse from the output of the one-shot 2 rewriting, as a result a positive pulse is formed at the output of the element 13 coincidences relative to the beginning of the input pulse at the time of rewriting (Fig. 2l). This pulse turns on the controlled source 10 of a stabilized current, the current of which charges the storage capacitor 6 to a voltage proportional to the duration of the input width-modulated pulse. Simultaneously with the launch of the one-shot dubbing 2, a one-shot delay jerk 15 is triggered, producing a delay pulse (Fig. 2 g), which opens the key element t 22. The delay pulse duration is slightly longer than the maximum possible width of the input pulse width pulse. By the end of the delay pulse on the storage capacitor 23, the emitter follower 21 and the open key element 22 are set to a voltage (FIG. 2 d) proportional to the duration of the converted PWM pulse, which remains until the next delay pulse is formed. The negative front of the same delay pulse through the differentiating element 16 triggers a one-shot correction 17, producing a pulse whose duration is proportional to the voltage supplied to the control input of the one-shot correction 17 from the storage capacitor 23 (Fig. 2e). Due to the delay pulse, the one-shot correction 17 is triggered after the conversion of the input signal is completed, when a constant voltage level is determined on the storage capacitor 23, which determines the duration of the single-vibration pulse 17 of the correction.

The output pulses of the one-shot 17 correction and one-shot 15 delay arrive at the inputs of the element 18 OR NOT, at its output a correction pulse is formed, the positive edge of which coincides in time with the negative edge of the one-shot 17 correction, and the negative edge of the next front modulator of the impulse (Fig. 2 g), i.e. the duration of the correction pulse depends on two parameters: on the voltage on the storage capacitor 23, proportional to the duration of the input width-moduli o- vannogo pulse and the magnitude of the repetition period of the input signal at the time of demodulation. The correction pulse opens a key element 19 through which the storage capacitor 6 is discharged by an amount proportional to the duration of the correction pulse. The discharge current is stabilized by the current stabilizer 20 (Fig. 2 h).

The voltage from the storage capacitor b is integrated over a period of a width-modulated signal using an analog integrator 14 (Fig. 2 and). The initialization of the integrator 14 is performed by a reset pulse simultaneously with the discharge of the storage capacitor 6.

The pulse from the one-shot rewriter 2 opens the key element 7 and the voltage from the output of the integrator 14 through the emitter follower 8 is stored on the storage capacitor 9 until the next PWM pulse arrives, i.e. until the next conversion cycle. A step voltage is removed from the output of the storage capacitor 9 (Fig. 2k), corresponding to an input signal converted into analogue form, in which there is no distorting component from the change in the period of the width-modulated signal. This is achieved by selecting a conversion factor between the control voltage of the one-shot correction 17 and the duration of the pulse generated by it so that the increment (decrease) in the area of the pulse voltage on the storage capacitor 6 caused by the increase (decrease) in the repetition period of the input signal is fully compensated by an additional discharge this capacitor through key element 19 and stabilizer 20

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current, as a result, the area of the pulse voltage on the storage capacitor 6 becomes what it would be if there were no changes in the period of the input width-modulated signal.

Thus, the introduction of a new modulated signal and links into a demodulator of a pulse-width modulated signal makes it possible to improve the accuracy of signal demodulation in the presence of spurious frequency modulation.

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Claims (1)

Invention Formula A demodulator of a width-modulated signal containing connected between the input bus and the control input of the first key element connected in series the first differentiating element, one-shot rewrite, second differentiating element and one-shot reset, connected between the power supply and common buses, connected in series by a controlled source stabilized current and a storage capacitor, in parallel with which is connected the first key element, the first emitter follower, between the output The one of which and the common bus include the second key element connected in series and the first storage capacitor, the combined outputs of which are connected to the output bus, and the control input of the second key element are connected to the output of the single-rewrite vibrator, and the third differentiating element in order to improve accuracy, a coincidence element, an integrator, a delay one-shot, a one-shot correction, an element ORI, a third key element, a current stabilizer, a second em An iterator repeater, between the output of which and the common length, are connected in series the fourth key element and the second storage capacitor, the combined outputs of which are connected to the control input of the one-shot correction, the input of which is connected to the output of the third differentiating element and the output to the first input of the OR-NOT , the second input of which is connected to the output of the one-shot delay, the input of the third differentiating element and the control input of the fourth key element, and the output from the control named by the input of the third key element, the output of which is connected via a current stabilizer to the common bus, and the input to the input of the second emitter follower, the output of a controlled stabilized current source and the input of the integrator, the output of which is connected to the input of the first emitter Horo repeater, and the reset input to the output one-shot reset, while the control input of the controlled stabilized current source is connected to the output of the coincidence element, inverting  ,, nft}, i, the input of which is connected to the output of the one-shot rewriter, and the non-inverted input is connected to the input of the first differentiating element, the output of which is connected to the input of the one-shot vibrator. a 5 g de f 3 and k l FIG. 2