SU720676A1 - Device for producing amplitude modulated oscillations - Google Patents

Description

one

The invention relates to radio engineering and can be used as a source of amplitude-modulated oscillations, for example, in testing and calibrating modulation depth gauges and sinusoidal ratio meters.

A device for receiving amplitude-modulated oscillations, containing a source of modulated sinusoidal signal, a source of manipulating video pulses, the output of which is connected to a control input of a frequency divider with a variable division factor, and an amplifier 1, is known. However, the known device does not provide for the establishment of the required constant modulation factor with a step. change the amplitude of the output signal.

The purpose of the invention is to establish the required constant modulation factor with a stepwise change in the amplitude of the output signal.

To do this, in a device for obtaining amplitude-modulated oscillations, containing a source of modulated sinusoidal signal, a source of manipulating video pulses, the output of which is connected to a control input of a frequency divider with a variable division factor, and an amplifier, between the output of the source of a modulated sinusoidal signal and another input of a frequency divider with a threshold element is introduced by a variable division factor, and a variable division divider output is connected to the amplifier input, the output of which is connected additionally introduced bandpass filter.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 - timing charts of the device.

The device contains a source of 1 modulated sinusoidal signal, a threshold element 2, a frequency divider with a variable division factor (DCD) 3, an amplifier 4, a band-pass filter 5 and a source 6 of manipulating video pulses.

The device works as follows.

Claims (1)

The sinusoidal voltage U: (Fig. 2a from source 1 enters threshold element 2, the response threshold of which is Un, and the release threshold is Uo. At the same time, and Un. At the output of element 2, pulses are formed (Fig. 2.6) arrive at the DPKD 3, to the control input of which the manipulating video ports Us from the source6 (Fig. 2, c) with a given manipulation frequency are supplied. The ultrasonic signal at the output of the PDKD 3 is shown in Fig. 2, d for case n 2, where n is DCFD division ratio. Pass through amplifier 4, video pulses And 4 are amplified (Fig. 2, e) and fed to band-pass filter 5. On The output of filter 5 is a sinusoidal signal Us (Fig. 2, e) modulated in amplitude by square pulses with a modulation factor equal to where n 2 (in general, 2,3,4 ...). 4, the sequence of video pulses U 4 (Fig. 2, e) is two successive sequences of identical video pulses with different repetition frequencies; the first sequence with a repetition frequency w (period T); second with repetition frequency (period pT) Let the video impulse be described by the function f (t). By decomposing the first sequence of the function f (t) with the repetition frequency (O in the Fourier series, we get | (t) dt, a. (T) SinmMtdt, fi (i) Cosmcotdt. Harmonic amplitude, which has a frequency to the first harmonic (tn 1 ), is equal to: A, x / af-f ЬГ / ($ (t) Si ina) tdt) 2-f (5f (t) .Cosa) tdt) 2. i Ha the output of the bandpass filter 5 is the voltage Us KA I, where K is the filter transmission coefficient. When decomposing in the Fourier series of the second sequence f (t) with a repetition frequency (i.e. with a period of pT), the frequency co has an n-harmonic (t n) ,, .SW; ± S -7 - V (% f (t ) Sin) 2 + ((t) Cosn-tdt) 4 At the output of the band-pass filter 5, the voltage is Kap. Hence: Thus, at the output of filter 5, there will be a signal modulated in amplitude by square-wave pulses and with a ratio of greater amplitude to less than n. The amplitude-modulated signal is usually characterized not by the ratio of maximum amplitude to minimum, but by modulation factor M. amplitudes to the minimum in the modulation coefficient M we get m -.-JU n T Thus, the resulting amplitude-modulated signal has a well-defined reference modulation coefficient. An apparatus for producing amplitude-modulated oscillations, comprising a source of a modulated sinusoidal signal, a source of manipulating video pulses, the output of which is connected to a control input of a frequency divider with a variable division factor, and an amplifier, characterized in that, in order to establish the required constant modulus, the step ratio the change in the amplitude of the output signal between the output of the source of the modulated sinusoidal signal and the other input of the divider is often You have a threshold element with a variable division factor, and a variable division frequency divider output is connected to the amplifier input, to the output of which an additionally introduced band-pass filter is connected. Sources of information taken into account in the examination. Mashbits L.M. Digital processing of wireless telephony signals. M., “Holy, 1974, p. 82 (prototype). ppppppppppppppppppp. p p p ppp ppp p p p p ppppp p p p p ppppp. l l l l l l  J J J J J figure 2.