SU420085A1 - DEVICE DEMODULATION AIM-FM-SIGNALS - Google Patents

Description

one

A device for demodulation of PAM-FMsignals is known, comprising a series-connected limiting amplifier, a control node and a distributor connected by outputs to channel integrators and a synchronization channel integrator via keys. The second inputs of the latter are connected to the output of the amplifier-limiter through a serially connected comparison circuit and a reference pulse generator. Such a device has a low sensitivity and noise immunity, as well as a significant error due to the instability of the carrier frequency of the signal.

In order to eliminate these drawbacks in the proposed device, between the output of the amplifier-limiter and the second input of the comparison circuit, the adder is connected for n periods of the carrier frequency, and the second input of the reference pulse former is connected to the integrator's output.

The drawing shows a block diagram of the proposed device.

The input signal through the amplifier-limiter 1 is fed to the inputs of the node 2 of the manager, the adder 3 n periods of the carrier frequency and the driver 4 of the reference pulse. The control unit selects the synchronization pulse and generates the control pulses of the distributor 5, the latter provides, together with

Keys 6 division ka) 1alov in time. The adder generates pulses of duration proportional to n periods of the current frequency (t: n 1Tx) of each channel. At the same time

with this, the reference pulse shaper produces a pulse equal to the duration n of the periods of the input frequency of the channel of the sync pulse, which corresponds to the pulse durability of n periods of frequency measuring

channels, in the absence of a useful signal (ts - pT,).

The reference impulse Te and pulse from the adder are compared in duration by the circuit 7,

at the output of which a pulse is formed equal to their difference Tc «((- - T.v).

The difference impulse Tc from the output of the comparison circuit through the keys 6 is fed to the corresponding channel of the 1st integrators 8 n pa and the integrator 9 of the synchronization channel. The constant component of the pulse in the channel frequency interval is equal to the useful signal.

and - and L.

° Tp / u (/ o ± DL)

When the condition is fulfilled (which is almost always the case), signal amplification is obtained, which is proportional to the frequency deviation D / ;. As can be seen from the above

The ratio, the output signal also depends on the square of the initial frequency / o; in the case of its departure, it causes considerable uncertainty. To eliminate this, the device applied a correction of the duration of the reference pulse. For this purpose, the output of the channel integrator is connected to the second input of the reference impulse generator, due to which the accuracy due to a decrease in the initial frequency of the signal decreases sharply.

The proposed device without the use of a frequency discriminator has high accuracy, stability and speed.

Subject invention

AIM-FM signal demodulation device containing serially connected limiting amplifier, control unit, distributor connected by outputs to channel integrators and synchronization channel integrator through keys whose second inputs are connected to the output of limiting amplifier through serially connected comparison circuit and reference generator impulse, characterized in that, in order to increase sensitivity, noise immunity and reduce finesse due to instability, the frequency , Between the output of limiting amplifier and a second input of the adder circuit is included for comparison periods n of the carrier frequency, and the second input of the reference pulse shaper connected to the output of the integrator siihronizatsii channel.