JPS581317A - Surface acoustic wave filter device - Google Patents

Abstract

PURPOSE:To obtain a surface acoustic wave filter device of simple circuit constitution by using distribution amplifying circuits, and obtaining constant characteristics over a wide frequency range. CONSTITUTION:A band-pass type surface acoustic wave filter 10 is provided with the 1st distribution amplifying circuit 11 as a driving circuit at its front stage, and the 2nd distribution amplifying circuit 12 as a circuit to be driven at its rear stage, thus constituting a surface acoustic wave filter device. The 1st and 2nd distribution amplifying circuits 11 and 12 consist of transistors Q1 and Q2, capacitors C1-C9, coils L1-L6, and resistances R1-R5 as shown in a figure. The amplifying circuit 11 has output impedance adjustable through the capacitor C4 and coil L3 of the output stage, and the amplifying circuit 12 has input impedance adjustable through the capacitor C7 and coil L4 of the input stage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface acoustic wave filter device suitable for a filter circuit in a tester for a television receiver.

Conventionally, the filter circuit built into the test equipment for the TVILON wingman is usually constructed by combining six or nine sets of tuned circuits.
However, recently, a surface acoustic wave filter device using a surface acoustic wave filter has been developed, and this surface acoustic wave filter device can be used as a filter in the above test machine. (b) By applying it as a road, the above-mentioned drawbacks can be eliminated.

However, in such a surface acoustic wave filter device, the output impedance of the drive circuit placed before the surface acoustic wave filter and the input impedance of the driven circuit placed after the surface acoustic wave filter are If these do not exist within a predetermined impedance range in a predetermined frequency range, there is a problem that the original design characteristics of the surface acoustic wave coil cannot be satisfied. That is, FIG. 1 shows the measurement results of the frequency characteristics of the surface acoustic wave filter when the output impedance of the driving circuit is varied in, for example, five steps under the condition that the input impedance of the driven circuit is constant, and Figure 2 shows the measurement results of the frequency characteristics of the surface acoustic wave filter when the input impedance of the driven circuit is varied, for example, in five stages under the condition that the output impedance of the drive circuit is constant. As is clear from FIGS. 1 and 2, in order to obtain the desired frequency characteristics, the output impedance of the drive circuit and the input impedance of the driven circuit are adjusted by providing matching circuits 2 and 5 at the subsequent stage, respectively. The output impedance of the driving circuit 5 consisting of the matching circuit 2 and the amplifier circuit 4 for signal loss compensation, and the human power impedance of the driven circuit 7 consisting of the matching circuit 5 and the amplifier circuit 6 for signal loss compensation are set to predetermined values. There is a round version with a configuration that can be set to . When applying a surface acoustic wave filter device having such a configuration to a testing machine for a television receiver, it is required to exhibit constant frequency characteristics over a wide frequency range, and therefore the output impedance of the drive circuit 5 and It is desirable that the input impedance of the driven circuit 7 does not change over a wide frequency range.

However, since the amplifying circuit 4.6 is normally constructed from a tofunister circuit and its internal impedance changes in response to frequency changes, the result is that the driving circuit 5 does not operate over a wide frequency range. In order to keep the output impedance and the input impedance of the driven circuit 7 constant, the design and adjustment of the matching circuits 2 and 5 becomes extremely troublesome. As shown in Figure 4, emitter follower circuits 8 are installed after the amplifier circuits 4 and 6, respectively.
.

The present invention has been made in view of the above circumstances, and its purpose is to obtain constant characteristics over a wide frequency range, simplify the circuit configuration, and improve ease of design. The purpose of the present invention is to provide a surface acoustic wave coiling device that can perform

An embodiment of the present invention will be described below with reference to FIGS. 5 and 6.

@ In Figure 5, 10 is a band-pass type surface acoustic wave coil, with a first distributed amplification circuit 11 as a driving circuit in the front stage, and a second distributed amplifier circuit 11 as a driven circuit in the rear stage.
A distributed amplification circuit 12 is provided. Each of the above distributed amplifier circuits 11
．． 12 are each constructed as shown in FIG. That is, each distributed amplification circuit 11.12 includes a Y fungistor Q1.
Q, z, capacitors C1 to C? , Carp A/Ll to L
6. Resistors R1 to R@ are connected as shown in the figure, and the first
The output impedance Za can be adjusted by changing the capacitance of the capacitor C4 or the inductance of the coil A/Ls in the output stage of the distributed amplifier circuit 11 of the i9 second distributed amplifier circuit 12. In mind, the capacitor V resistance of the capacitor C7 in the input stage can be adjusted to reduce the input impedance Z1 by changing the inductance of the coil *L4.In this case, the capacitor C*, Os' The capacitance is cd, the capacitor Cm, and the inductance of μLx is 41.
vLa.

I L6 inductance /2, coil pvLs
When the inductance of is set to Ll, the output impedance Zd and the human power impedance z1 are respectively expressed by the following equations.

That is, the output impedance Za and the input impedance Z1 exhibit constant values regardless of the frequency. Therefore, according to the surface acoustic wave filter device shown in FIG. 5, Ca w La + Ctr Lt is appropriately selected. In particular, it is possible to always obtain constant characteristics over a wide frequency range. In addition, matching circuits and emitter follower circuits that were conventionally required can be eliminated.

As is clear from the above description, according to the present invention, constant characteristics can always be obtained over a wide frequency range, and the 6-9 matching circuit and emitter follower circuit that were conventionally required can be eliminated. As a result, it is possible to provide an inertial surface wave filter device which has excellent effects such as simplifying the circuit configuration as shown in FIG. 9 and improving ease of design.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the frequency characteristic measurement results of a surface acoustic wave filter, and FIGS. 3 and 4 are block diagrams showing a conventional example. FIG. 5 is a block diagram showing an embodiment of the present invention, and FIG. 6 is an electric circuit diagram showing the main parts of the embodiment. In the figure, 10 is a surface acoustic wave filter, 11 is a first distributed amplifier circuit, and 12 is a second distributed amplifier circuit. Applicant Mayasu Kogyo Co., Ltd. Kinsha M+ [i2] 2nd M N30 7 4th M 7 512I Ka 6 M

Claims (1)

[Claims] 1. A bandpass type surface acoustic wave filter, and a first distributed amplifier circuit that drives the surface acoustic wave filter with a predetermined output impedance in a predetermined frequency range;
a second distributed layer S circuit driven with a predetermined input impedance in a predetermined frequency range by the output of the surface acoustic wave filter, and the signal loss of the surface acoustic wave filter is reduced by each of the distributed amplifier circuits. 9. An elastic plain wave filter device configured to compensate. 2. The surface acoustic wave filter device according to claim 1, wherein the first distributed amplifier circuit includes at least one of an inductance and a cavacidance for output impedance adjustment at its output stage. . 5. The surface acoustic wave according to claim 1, wherein the second distributed amplification circuit is provided with at least one of an inductance and a capacitor Vtance at its input stage for adjusting input impedance. Flip device.