JPS62233910A - Band-pass filter using two-port crystal resonator - Google Patents

Abstract

PURPOSE:To obtain a band-pass filter by connecting in parallel two tow-port crystal resonators having different frequencies so that the phase shift between both input/output terminals differs by (2n+1)pi. CONSTITUTION:In forming a new two-port circuit by connecting input/output terminals of two two-port crystal resonators 4,5 in parallel constituted by arranging two pairs of electrodes to both face of an AT-cut crystal substrate to cause the energy confinement, the combination of the output terminals is made different from that of the input terminals. The design stated above offers an equivalence of the adoption of a transformer 11 applying 180 deg. phase shift to one resonator to form a band-pass filter. In applying the band-pass filter to multi-stage cascade connection or parallel connection, the band-pass fitler is realized without using an expensive large-sized hybrid transformer with very simple method and the inexpensive band-pass filter of small size whose specific band is set optionally is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a nine-band pass filter using a two-port crystal resonator, which constitutes a band-pass filter without using a hybrid transformer.

(Prior art) Conventionally, a bandpass filter using a crystal resonator has two crystal resonators 1 and 2 with different frequencies as shown in Fig. 2.
Generally, the resonators are connected in parallel so that the phases of the signals input to each resonator differ by 180 degrees from each other by a hybrid transformer 3 inserted at the input end of the resonator.

However, the above-mentioned hybrid transformer (Object of the Invention) The present invention has been made in view of the above circumstances, and uses a simple method to eliminate the need for a hybrid transformer that is difficult to implement. The aim is to provide a full range of Misaki Iba/Dobus filters.

(Summary of the Invention) Therefore, in the present invention, a two-port resonator is used as the crystal resonator, and the structure is as follows.

That is, by connecting two two-port crystal resonators having different resonance frequencies in parallel so that the combinations of input terminals or output terminals are different from each other, the output of each resonator is synthesized at the output terminal. The filter is configured so that the phase relationship of the signals actually differs by (2n+1)π.

(In order to create a 2-port crystal bandpass filter 1f:trIt, which has the bandwidth and attenuation characteristics of a new house, connect an arbitrary number of them in cascade in multiple stages using these basic sections. Also, connect these in parallel in multiple stages to achieve one pass band. A wide filter makes up the whole thing.

(Example) The present invention will be described in detail below based on an illustrated example.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the same figure, 4 and 5 are two pairs of ! to create energy confinement on both sides of the AT' cut crystal substrate, respectively! Two two-port crystal resonators configured by arranging poles,
When connecting the input and output terminals of each resonator in parallel to form a new two-voice circuit, the combination of output terminals is connected in a manner different from that of the input terminals.

The phase shift (-9) between the input and output terminals of the two two-port crystal resonators thus combined is as follows.

That is, if we look at the two-port crystal resonator connected as shown in Figure 1 individually, the polarities of the output terminals 8, 8' and 10°10' are reversed, so that the output terminals for the same signal It is easy to understand that the phase difference in the two directions is 180°.

Therefore, if Fig. 1 is expressed as an equivalent circuit, as shown in Fig. 3, a transformer 11 with a phase shift of 1800 in one resonator.
is equivalent to the one inserted, and by further equivalent conversion, it can be expressed as a lattice circuit as shown in Figure 4,
This is a bandpass filter as is well known.

Similarly, the equivalent circuit elements L1 and L2 in FIGS. 3 and 4 above. C
I, C2 and Co + , Co 2 , Col'
, Co z' are the equivalent inductance, equivalent capacitance, and parallel capacitance of the input and output electrodes of the two two-port crystal resonators, and f+=1/2π, / L+C+ , fz=1
/ 2πV/TF has the relationship.

As explained above, a bandpass filter can be realized by combining and connecting the input and output terminals of two two-port crystal resonators having the same phase relationship.

In the embodiments described above, two resonators are connected in parallel, but the present invention does not need to be limited to this. As with general filters, each of the above-mentioned filters is used as a basic section, and these are connected in multi-stage cascade. This results in even steeper cutoff characteristics and greater guaranteed attenuation! ? It is possible to realize a band-pass filter with high performance. Furthermore, by connecting a plurality of two two-port crystal resonators in parallel with opposite phases, it is possible to realize a filter metal having an even wider pass band.

The structure of the filter according to the present invention described in one or more embodiments is shown in which each resonance 3 is formed on an independent crystal plate, but the resonator is an energy trap type resonator. Therefore, the vibrations are concentrated on the electrodes and confined in an area that is very small compared to the size of the blank plate.If we do our best, we can create two resonators that resonate on the same blank plate, as shown in Figure 5. Vessel 1
A second-order bandpass filter can be constructed with one blank plate by forming the filters sufficiently far apart from each other so as not to cause the acoustic coupling described in (2). By incorporating this into a three-terminal type holder and connecting the connection buttons on the surface with a conductive adhesive or the like so as to make them conductive, the structure 11i3Ee shown in FIG. 1 can be realized with one blank plate and one case. At this time, the frequency difference between the two resonators can be adjusted to a desired value by fine adjustment of the circumference e of the crystal resonator, as well as by fine adjustment vapor deposition, etc.

Furthermore, it is also possible to form a multi-stage cascade or parallel connection of these on the same base plate. With such a structure, the number of parts can be reduced and the manufacturing process can be simplified.

(Effects of the Invention) The present invention is constructed as described above and realizes a bandpass filter using an extremely simple method without using an expensive and large hybrid transformer. This is very effective in obtaining a bandpass filter with arbitrarily set bands at a very low cost.

Note that the present invention need not be limited to the embodiments described above, and it is clear that various modifications can be made to the piezoelectric substrate material, electrode arrangement, etc.

[Brief explanation of drawings]

Figure 1 shows a two-port crystal resonator e01 according to the present invention.
A connection diagram of a band-pass filter. Figure 2 is a connection diagram of a conventional crystalline filter. Figures 3 and 2g4 are both shown in the first picture above. FIG. 5 is a perspective view showing another embodiment of the present invention. 1.2...Crystal resonator, 3...
...Hybrid transformer, 4,5...
...2-port crystal resonator, 7.7' to 1
0.10'・・・・・・Input/output terminal of 2-port crystal resonator. 11......Trance.

Claims (4)

[Claims] (1) When two two-port crystal resonators with different frequencies are connected, the amount of phase shift between their input and output terminals is (2n+1)π(n=
A bandpass filter using two-port crystal resonators, characterized in that they are connected in parallel so that they are different (0, 1, 2, etc.). (2) In the two two-port crystal resonators, the polarity of the input and output terminals of one of the resonators is inverted and connected in parallel, so that the phase of the output signal of both resonators is combined at the output terminal. 2. A bandpass filter using a two-port crystal resonator according to claim 1, characterized in that the filters are configured such that they differ from each other by (2n+1)π. (3) A band-pass filter characterized in that the band-pass filter according to claim 1 or 2 is connected in cascade in multiple stages as a basic section. (4) A bandpass filter using a two-port crystal resonator, characterized in that the bandpass filters according to claims 1 and 2 are connected in parallel in multiple stages as basic sections.