Strip piezoelectric filter with complex loads

 

The invention relates to electronics and can be used in the paths of the intermediate frequency receiving devices. The technical result is to reduce the deformation of the frequency characteristics of the filter. The filter contains inductance (1, 5), piezoelectric resonators (cont'd) (2, 6), capacitors (3, 4, 7-13). In the case when you want to obtain wider bandwidth, parallel to the capacitor (4) and (8) includes corresponding PR. For notch filters of high order between PR (2) and (6) are included stair units of series-connected PR and connected to the leads of PR capacitors connected to a common bus. 2 C.p. f-crystals, 4 Il.

The invention relates to electronics and can be used in tracts intermediate frequency (if) receivers.

In modern professional radio receiving devices in the paths of the inverter are used, as a rule, band quartz filters with high temporal and thermal stability, low loss in the passband and providing a high level of attenuation in the band of trapping. One such filter is described in [1] pages 124, Fig.3.10, it is

This scheme allows accurate enough to implement all the required electrical parameters in the case when the filter input and output loaded at active resistance. At the same time is often required to align the filter with complex loads, particularly loads, represented by the parallel connection of resistor and capacitor.

A shortcoming of this scheme is that with the introduction of the loads with a capacitive component can significantly distort the frequency response of the filter deteriorates the flatness, gain, attenuation in the band of trapping).

The objective of the invention is to provide a piezoelectric filter, which provides the necessary requirements given the complex values of the load equivalents.

The problem is solved in that in the filter containing the first inductor tap connected to the common bus, to the first potential, the output of which is connected to the first piezoelectric resonator and the first capacitor and the second potential output of the first inductor is connected to the first output of the second capacitor, the second the findings of the first piezoelectric resonator and the second capacitor is connected between the social output of which is connected to the second piezoelectric resonator and the third capacitor, and the second potential of the second output inductance connected to the first output of the fourth capacitor, and the second the findings of the second piezoelectric resonator and the fourth capacitor are connected to the first potential to the first output inductance connected to the fifth capacitor, the second terminal of which is connected to the input potential terminal of the filter, the first potential output of the second inductor via the sixth capacitor is connected with the output potential terminal of the filter, while the second findings of the first and second piezoelectric resonator connected to the first output of the seventh capacitor second terminal of which is connected to a common bus, the second the findings of the first and third capacitors are connected to the common bus, besides, to the input potential terminal of the filter connected to the eighth capacitor to the output terminal of the filter is connected to the ninth capacitor, the second the conclusions of the eighth and ninth capacitors connected to a common bus.

Comparative analysis shows that the proposed solution differs from the prototype in that the device introduced new communication elements: the first potential to the first output inductance connected to the fifth capacitor, the second is activity through the sixth capacitor is connected with the output potential terminal of the filter, at this second the findings of the first and second piezoelectric resonator connected to the first output of the seventh capacitor, the second terminal of which is connected to a common bus, the second the findings of the first and third capacitors are connected to the common bus, besides, to the input potential terminal of the filter connected to the eighth capacitor to the output terminal of the filter is connected to the ninth capacitor, the second the conclusions of the eighth and ninth capacitors connected to a common bus.

When comparing the proposed solutions not only prototype, but also with other known solutions in science and technology, not found solutions with similar characteristics.

In Fig.1A shows the electric circuit of the proposed device. The filter consists of a first inductor 1 having a drain connected to the common bus, the first piezoelectric resonator 2 is connected to the first potential output of the first inductor and the first capacitor 3, the second terminal of which is connected to a common bus, to the second potential to the first output inductance connected to the second capacitor 4, a second output which is connected with the second output of the first piezoelectric resonator, the filter also includes a second inductance 5, having a drain, with the General 6 and the third capacitor 7, the second output of which is connected to a common bus, to the second potential to the second output inductance connected to the fourth capacitor 8, the second terminal of which is connected with the second output of the second piezoelectric resonator to the first potential to the first output inductance connected to the fifth capacitor 9, the second terminal of which is connected to the input potential terminal of the filter, to the first output of the second inductor is connected to the sixth capacitor 10, the second terminal of which is connected with the output terminal of the filter, the second the findings of the first 2 and 6 second piezoelectric resonators connected to the first output of the seventh capacitor 11, the second terminal of which is connected to a common bus, between the input terminal of the filter and a common bus enabled eighth capacitor 12, and between the output potential terminal and a common bus connected to the ninth capacitor 13.

The filter works in the following way. The scheme shown in Fig.1A, if not to take into account it is connected to capacitors 9, 10, 11, 12, 13, is a two-tier band-pass filter, each link of which can be put into correspondence with symmetric bridge equivalent, one pair of branches which included the piezoelectric resonator and the second goat which is positive, and the other negative, and remove from the bridge circuit capacity with a positive sign, and the remaining negative capacity combine respectively with resonator and the capacity of the branches of the bridge circuit. When the value is negative capacity is greater than the value of the parallel static capacitance of the resonator and more of the nominal capacity, included in the pair of opposite branches of the bridge equivalent, will receive a new realizable values of the parameters of the resonator and capacitance of the source schema. The frequency of the serial resonancethe piezoelectric resonator is determined by the expression

and the dynamic inductance is equal to

where

fqthe frequency of the serial resonance of the original piezoelectric resonator;

Withp- static capacitance of the resonator;

With the dynamic capacity of the resonator;

Withn- the value connected in series negative capacitance;

- the ratio of negative and static tanks.

In the future, taken from the bridge circuit serial containernand some capacity With0included in parallel which can be replaced by using the known conversion Norton [2] chain, it is shown in Fig.2B.

In Fig.2 shows part of the circuit from the output load. When this ratio is determined by the expressionand value1and C2calculated as

With1=Cn+C0,

Thus, distinguishing it from the original schema serial capacitorsnand then selecting appropriate to align the filter with the load capacitance value With0replacing the chain of capacitorsnand C0a circuit consisting of a capacitor With1and C2and going from the bridge circuit of each of the links to their differential bridge equivalents, we get the diagram shown in Fig.1A.

It can be noted that the resulting T-shaped structure, consisting of three capacitors connected between the first and second link of the filter, as a rule, can be replaced with a single capacitor. Consequently, the proposed filter circuit the equivalent circuit of the selected prototype and differs in that it allows you to adjust the original filter with complex loads without deforming in this case the frequency response of the filter.

In the case when you want to get more Sirig.1B).

For notch filters of high order between the first and second links can be included stair parts, as shown in Fig.1B. The first and last parts of the filter are used to ensure alignment with the set of complex loads.

Sources of information

1. The great J. I., Gelmont Z. Y., Zeljah E. C. Piezoelectric filters. - M.: Communication, 1966.

2. Przesmycki O. the Design of electrical ladder filters. - M.: Communication, 1968.

Claims

1. Strip piezoelectric filter with integrated load containing the first inductor tap connected to the common bus, to the first potential, the output of which is connected to the first piezoelectric resonator and the first capacitor and the second potential output of the first inductor is connected to the first output of the second capacitor, the second the findings of the first piezoelectric resonator and the second capacitor are connected, in addition, the filter includes a second inductor tap connected to the common bus, to the first potential, the output of which is connected to the second piezoelectric resonator and the third capacitor, and the second potential of the second output inductance connected is vertigo capacitor are connected, wherein the first potential to the first output inductance connected to the fifth capacitor, the second terminal of which is connected to the input potential terminal of the filter, the first potential output of the second inductor via the sixth capacitor is connected with the output potential terminal of the filter, while the second findings of the first and second piezoelectric resonators connected to the first output of the seventh capacitor, the second terminal of which is connected to a common bus, the second the findings of the first and third capacitors are connected to the common bus, besides, to the input potential terminal of the filter connected to the eighth capacitor to the output terminal of the filter is connected to the ninth capacitor, second, the conclusions of the eighth and ninth capacitors connected to a common bus.

2. Filter by p. 1, characterized in that parallel to the second capacitor connected to the third piezoelectric resonator, and in parallel with the fourth capacitor is connected to the fourth piezoelectric resonator.

3. Filter by p. 1, characterized in that between the second pins of the first and second piezoelectric resonators includes an additional circuit consisting of N series-connected piezoelectric resonators, when Ammoudi capacitor, second, the findings of these capacitors are connected to the common bus.

 

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FIELD: radio engineering, possible use in radiolocation stations working with two multi-frequency generators.

SUBSTANCE: directional filter contains two low-and-high-pass filters, a T-joint and two two-channel commutators. Channels of commutator rotors are coupled with shoulders of T-joint, which amount to λ/4 or λ/2 respectively with consideration of rotor channel lengths, where λ - wave length on shoulders of the T-joint.

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