SU21277A1 - The method of turning on the electric filter - Google Patents

Description

. The role of quartz in modern radio engineering is becoming increasingly important every day. But while its use in the field of radio transmission as a frequency stabilizer has long justified itself, quartz resonators in radio technology are not widely used. The main reason for this is the extremely narrow band of transmitted frequencies, not allowing high transmission speeds. The method proposed in accordance with the invention for switching on an electric filter with two quartz (piezo-electric) plates is aimed at increasing the frequency bandwidth.

In FIG. 1 shows a diagram of an apparatus for carrying out the proposed method; FIG. 2-resonance filter curves.

The filtered voltage is applied to the primary winding 3 of the transformer, the ends of the secondary winding 4 of which are connected to electrodes 5 and b of quartz plates 1 and 2. The anti-shielding electrodes of these plates are enclosed in one common electrode for both plates 7 (or connected to each other). Between this electrode 7 and the middle point of the secondary winding 4 of the transformer is included a wadded or inertia resistance 8. The voltage drop across this resistance caused by the geometric sum of the currents through both plates is the output voltage equal to that of the filter. If the frequency of natural oscillations of the first quartz plate / 1 is greater than the second- / 2 (the other properties of both quartz plates are the same), and the frequency of the exciting voltage is less than / b or greater than / 2, then the phase shift angles (between the current through the plate and the voltage across it will differ little for both plates; (and the smaller, the smaller the difference. Ug-L).

Since the voltages on apastins are in opposite phases, the currents through the plates will be in phases close to the opposite, and will partially compensate each other (compensation will be complete with / i - / i).

It is easy to see that for frequencies between L and / 2, the effect will be the opposite. The frequency of forced oscillations will then be greater than the natural frequency for the first plate and less for the second. Therefore, the phase shift angles (between the current through the plate and the voltage across it) for both plates will be of a different sign, and since the voltages on the plates are supplied in opposite phases, the currents through both plates will add.

If the detuning is correctly selected (/ 2- / i), then in this way one can obtain a significantly better curve than with a single quartz plate. FIG. Figure 2, which illustrates the above, shows the dependence of the input voltage of the filter on the detuning at a constant input voltage (curve 1) and the same dependence for one plate (curve 2). “Thus, with the aid of the proposed device, it is possible to increase the width of the transmitted parts, increase the slope of the meat and reduce the gain at frequencies lying outside the passed band.

The subject matter of the invention.

A method of switching on an electric filter using piezoelectric plates, characterized in that the electrical voltages on the plates 1, 2, the natural oscillation periods of which are different from each other, are given in opposite phases, and in the receiver 8 the geometric sum of the currents flowing through both plates.