JPS632412A - Resonator for fm discriminator - Google Patents

Abstract

PURPOSE:To make a differential gain band width wider and, at the same time, to reduce the size and cost of a resonator for FM discriminator, by providing a series and parallel resonators connected in the form of a ladder and constituting both of the resonators of piezo-resonators which utilize thickness-sheur oscillation. CONSTITUTION:A resonator 9 is constituted of piezo-resonators 91 and 92 which utilize thickness-shear oscillation. The resonator 91 is a series resonator and provided with two electrodes 912 and 913 on both main surfaces of a piezo-electric substrate 911 made of ceramics, etc., in such a state that the electrodes 912 and 913 can be overlapped each other diagonally at the central part of the substrate 911. The other resonator 92 is a parallel resonator and composed of a piezo-electric substrate 921 and electrodes 922 and 923. Then an input terminal 93 is conductively joined with the electrode 912 with solder, etc., and an output terminal is conductively joined between the electrodes 913 land 923 with solder, etc. Moreover, a grownding terminal 95 is conductively joined with the electrode 922 and the resonators 91 and 92 are adhered to each other with an adhesive 96. When the resonators 91 and 92 are connected with each other in the form of a ladder in the resonator 9, the differential gain band width of this FM discriminator can be widened and, at the same time, the resonator 9 can be reduced in size and cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resonator used in a quadrature type or differential peak value type FM discriminator for demodulating FM signals.

[Background technology]

FIG. 2 is a circuit diagram showing an example of a quadrature type FM discriminator. An FM intermediate frequency signal is applied to an intermediate frequency amplifier 2 via an input terminal 1 . The intermediate frequency amplifier 2 amplifies this FM intermediate frequency signal and provides its output to the multiplier 3, and the phase shifter 4 converts the signal into 9
The signal is shifted by 0±α (0≦α≦90) degrees and given to the multiplier 3. Multiplier 3 multiplies the FM intermediate frequency signal and the phase-shifted signal, and provides a demodulated signal FM-detected from the output beat component to low-pass filter 5 . Low-pass filter 5 removes unnecessary components contained in the demodulated signal and outputs it from output terminal 6.

The phase shifter 4 in this example has a capacitor 41 connected in series on the input side, and a resonator 42 having a dual mode configuration, a resistor 43, and an inductor 44 connected in parallel between the input and output. . The phase shifter 4 using this resonator 42 has the resonator 4
This method takes advantage of the fact that there is a phase difference of approximately 90 degrees between input and output between the resonance frequency and the anti-resonance frequency of 2.

However, in the FM discriminator using the resonator 42 as described above, there is a problem that the differential gain bandwidth is narrow, and an FM discriminator that solves this problem has been separately proposed by the same applicant.

To explain it simply, the FM discriminator uses a resonator 7 having a ladder configuration as shown in FIG. 3 instead of the resonator 42 in the phase shifter 4.

In the figure, 71 is a series resonator, 72 is a parallel resonator,
73 is an input terminal, 74 is an output terminal, and 75 is a ground terminal.

The impedance characteristic of the series resonator 71 is, for example, the fourth
The impedance characteristic of the parallel resonator 72 becomes, for example, curve b in FIG. 4. And the resonant frequency fr of the parallel resonator 72 and the series resonator 7
The above-mentioned differential gain bandwidth is determined by the interval from the anti-resonant frequency fa of 1, but since the image frequency is that of a separate resonator, it can be set freely unlike in the conventional case.
Therefore, the differential gain bandwidth can be expanded.

[Object of the Invention] By the way, the specific configuration of the resonator 7 is, for example, a piezoelectric resonator 81 that utilizes a thick vertical vibration mode as shown in FIG. 5, and a thick vertical vibration mode as shown in FIG. The piezoelectric resonator 81 is stacked with the piezoelectric resonator 82 that utilizes the vibration mode.
For example, the series resonator 71 shown in FIG. 3 has a ladder configuration in which the piezoelectric resonator 82 becomes the parallel resonator 72.

In the figure, 811 and 821 are piezoelectric substrates, 81 and 821 are piezoelectric substrates, respectively.
2.813.822.823 are counter electrodes, respectively.

However, when the piezoelectric resonators 81 and 82 as described above are used for example at 10.7 MHz, they can be constructed with dimensions of about 4 x 4 (length x width, the same applies hereinafter) mm, but For 4.5MHz frequency, 8x8m
There is a problem in that good performance cannot be obtained unless the size is about 1.5 m, and there is a problem in miniaturization and cost reduction.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a resonator for an FM discriminator that can expand the differential gain bandwidth and be downsized.

[Means to achieve the purpose]

The resonator for an FM discriminator of the present invention is characterized in that it includes a series resonator and a parallel resonator connected in a ladder shape, and both resonators are piezoelectric resonators that utilize a thickness-shear vibration mode. .

[Effect]

Since the resonator according to the present invention has a ladder configuration, the differential gain bandwidth can be expanded as described above.

Furthermore, since a piezoelectric resonator in the thickness-shear vibration mode is used as the series-parallel resonator, it is possible to reduce the size.

〔Example〕

FIG. 1 shows a resonator for an FM discriminator according to an embodiment of the present invention, and (A) is a plan view thereof;
(B) is a sectional view taken along the line 1-I. The resonator 9 of this embodiment has piezoelectric resonators 91 and 92, both of which utilize a thickness-shear vibration mode, stacked on top of each other, so that the piezoelectric resonator 91 resonates in series with the resonator 71 in FIG. 3, and the piezoelectric resonator 92 resonates in parallel. The ladder configuration is such that the child is the child 72.

To be more specific, the piezoelectric resonator 91 includes two electrodes 912., which are diagonally opposed to each other and overlapped at the center of the rectangular piezoelectric base 4H911 made of, for example, piezoelectric ceramic.
913 is provided. The piezoelectric resonator 92 also has a similar configuration, 921 is a piezoelectric substrate, 922.923
is an electrode.

Then, the input terminal 93 is connected to the electrode 912, and the electrodes 913 and 92
An output terminal 94 is conductively connected between the piezoelectric resonators 91 and 92, and a ground terminal 95 is conductively connected to the electrode 922 using, for example, solder or a conductive paste (not shown).

The resonator 9 is then packaged by known means as necessary. For example, the resonator 9 is damped with a silicone rubber dip or the like, and then covered with epoxy resin using a fluidized dipping method or the like.

The resonator 9 is a piezoelectric resonator (series resonator) 91 and a piezoelectric resonator (parallel resonator) 92 connected in a ladder manner. Thus, the differential gain bandwidth of the FM discriminator can be expanded.

Moreover, since the piezoelectric resonators 91 and 92 both utilize the thickness-shear vibration mode, their dimensions are significantly larger than those that utilize the thickness-vertical vibration mode as shown in Figures 5 and 6. Therefore, the size of the resonator 9 can be reduced, and the cost can be reduced. Simply put, when using the thick vertical vibration mode, as shown in Figure 5,
As shown in FIG. 6, counter electrodes 812, 813, 822.
823, piezoelectric substrates 811, 821 are required in a predetermined range around the piezoelectric substrate 911.
This is because 921 can be used. - For example, the dimensions of a piezoelectric resonator 91.92 are 6.5X1.92 at 4.5MHz.
The piezoelectric resonator 81 in FIGS. 5 and 6 is about 0 mm.
The area is about 1/10 compared to 82. Also, the thickness becomes thinner to some extent.

It should be noted that the structure shown in FIG. 1 is just an example, and any structure other than the above may of course be used as long as the piezoelectric resonator in the thickness shear vibration mode is configured in a ladder manner.

Furthermore, the resonator of the present invention can also be used in an impedance circuit for obtaining an output according to the input frequency in a differential peak value type FM discriminator, and even in that case, the same effect as described above can be obtained. is obtained.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to expand the differential gain bandwidth, and also to reduce the size and cost.

[Brief explanation of drawings]

FIG. 1 shows a resonator for an FM discriminator according to an embodiment of this invention, and (A) is a plan view thereof;
(B) is a sectional view taken along the line I-1. Figure 2 shows
FIG. 2 is a circuit diagram showing an example of a quadrature-type FM discriminator. FIG. 3 is a diagram showing an example of an equivalent circuit of a resonator having a ladder configuration. FIG. 4 is a diagram showing an example of impedance characteristics of a piezoelectric resonator constituting the resonator of FIG. 3. FIG. 5 shows an example of one side of the piezoelectric resonator constituting the resonator of FIG. 3, in which (A) is a front view thereof, and (B) is a back view thereof. FIG. 6 shows an example of the other side of the piezoelectric resonator constituting the resonator of FIG. 3, in which (A) is a front view thereof, and (B) is a back view thereof. 9.8 Resonator according to the example, 91... Piezoelectric resonator (
series resonator), 92... piezoelectric resonator (parallel resonator),
93...Input terminal, 94...Output terminal, 95...
Earth terminal.

Claims (1)

[Claims] (1) A resonator for an FM discriminator, comprising a series resonator and a parallel resonator connected in a ladder shape, both of which are piezoelectric resonators that utilize a thickness-shear vibration mode.