JPS61230512A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To realize low loss and low ripple over a wide frequency range by applying complex number conjugate matching when viewing an irradiation conductance from a conductance of an external circuit and also applying complex number conjugate matching vice versa at the same time. CONSTITUTION:A matching capacitive element 5, a matching capacitive element 3, and a stray capacitance 7 of a pin and package part are connected to a connecting point of a series connecting body comprising a matching inductive element 4 and a wire inductance inductive element 6 and other ends to form a matching circuit as shown in an equivalent circuit. In this circuit, each imaginary part of an admittance Yin viewed from the conductance Gl of a power supply 1 and of an admittance YOUT viewed from an irradiation conductance Ga of an electrode is zero, the real part of the admittance Yin is equal to the conductance Gl and the real part of the admittance YOUT is equal to the conductance Ga by selecting each matching element.

Description

[Detailed Description of the Invention] "Field of Application of the Invention" The present invention relates to an elastic long-plane wave device that aims at low loss and low ripple, and particularly to easily achieve low loss and low ripple at high frequencies. Background of the Invention Regarding the method of designing a good matching circuit °1 surface acoustic wave device [Background of the Invention] Conventionally, matching circuits using O, R, and For example, in the method disclosed in JP-A-56-1575015, a conductor that has an inductance characteristic is connected in parallel to a surface acoustic wave device.However, in this method, if the imaginary part Even if it is possible to cancel, when matching the real part,
For example, for an external circuit Gl of 50Ω, the radiation conductance 0α of '#L must be designed to be 20 mlr, which necessitates making the opening of the electrode larger and increasing the substrate area.

In addition, the method shown in Japanese Patent Application Laid-Open No. 56-27525 is 2
It describes how to achieve matching using a linear actance element. However, this method targets surface acoustic wave devices with a normal two-electrode configuration, and if the value of the reactance element is determined so that complex conjugate matching is achieved when viewed from the power supply side, low loss can be achieved.
Surface acoustic wave device for low ripple, example #f3'
In the four-love configuration, another radiation conductance G is added to ′.
a to 111LTJ1. Since it is necessary to obtain complex conjugate matching by looking at Itll, it is not possible to achieve low loss and low ripple in the above-mentioned published patent.

Furthermore, at high frequencies, the inductance of the bonding wire that electrically connects the surface acoustic wave element chip to the package pin cannot be ignored. Also, it is necessary to consider the stray capacitance that occurs between the package pin and the surface where the surface acoustic wave element chip is attached. It won't happen.

There is no mention of these in the two published patents.

[Purpose of the invention]

An object of the present invention is to provide a surface acoustic wave device that eliminates the drawbacks of the prior art and at the same time exhibits low loss and low ripple over a wide frequency range.

[Summary of the invention]

In the present invention, from the conductance Gl of the external circuit to 11c
Complex conjugate matching is achieved by looking at the radiation conductance Ga of the pole, and at the same time, i-line conjugate matching is achieved when looking at the conductance Gl of the external circuit from the radiation conductance Ga of the pole. At this time, the inductance of the wire and the pins and chips of the package We have developed a matching circuit that also takes into account the stray capacitance of the mounting surface.

The basic configuration is shown in FIG. 1 and will be explained.

FIG. 1 is an equivalent circuit diagram of a central electrode of a 3% polar surface acoustic wave device including an external circuit and a matching element. Here, 1 is the signal source, 2 is the conductance Gl of the signal source (external circuit),
3 is a capacitive element for matching 01% 4 is an inductive element for manufacturing L1.5 is a second capacitive element C2, 6 is a second inductive element L2.7 is [Other 11p Kameyodo Ct , 8 is the radiation conductance Ga of the electrode.

In addition, Yin shown in the figure is the conductance G of the external circuit.
t represents the admittance seen from 1iLu, and Yout represents the admittance seen from the radiation conductance side of the 'vL pole.

In Figure 1 (at the center frequency) near 1nYou
The imaginary part of t becomes zero, and the real part of Yin becomes (equal to Jt.
, Yout is equal to Ga. The value of each matching element is determined so that the real part of , Yout is equal to Ga.

Here, at high frequencies, the second capacitive element C2 of 5 and the second capacitive element C2 of 6
The inductive element L2 may be included in the mounted state of the surface acoustic wave device as the stray capacitance of the device and the inductance of the wire, respectively [Embodiments of the Invention] Specific embodiments of the present invention will be shown below.

First, an example of the overall device configuration is shown in FIG. 2. What is shown in FIG. 2 is a 3% deaf configuration example, which is an example of a low-loss surface acoustic wave device. 10 is a piezoelectric substrate, 11 is an input electrode with electrode cross width weighting, 12.12' is an output electrode without electrode cross width weighting, and 15 and 13' are shield electrodes. The equilateral circuit diagram shown in the first factor shows the 11 input WL poles shown in FIG. 2, their external circuits, and the rectifying circuit.

Here, we prototyped the 311L other type configuration shown in Fig. 2 as a surface acoustic wave device with a center frequency of 400 MH2.
- Using the equivalent circuit shown in Figure 1, the electrostatic capacitance Hot of electrode 7 and the radiation conductance Ga of electrode 8 are set to 2.2 at the center frequency from the design values.
9 (PF), and 2.55 (mv), giving 5 ￥
1 (PF) and 4 (no) were given to the capacitive element C2 of No. 2 and the second inductive element L2 of No. 6, respectively.

In this example, 02 in 5 is the stray capacitance in the hidden state of the surface acoustic wave device, and L2 in 6 is the inductance of the wire. Under these conditions, the capacitive element C1 for matching in 5 is 15.4 (PF) and the matching inductive element Ll of 4 is 29.5 (nH), the imaginary parts of Yin and You t are each t4 at the center frequency.
(=υ)apl(m), and the real part of Yin is 21 (mv), and the conductance of the external (b) path is 20
(Close to mri(, Yout's real part is 15 (mrito 1!!
This corresponds to the radiation conductance of 2.55 (-). From this, the frequency characteristics of the input electrode during matching in this example are as shown in FIG. 3, with a loss of 0.0 at the center frequency.
18 (αβ), and multiple reflected waves between electrodes (hereinafter abbreviated as TTE) that cause ripples can be suppressed to 47αβ.

In FIG. 3, the solid line shows the loss, and the broken line shows the TTE suppression.

Next, another example will be shown. The overall device configuration is the same as that of the first embodiment, but using the equivalent circuit shown in FIG.
The capacitance at of electrode 7 and the radiation conductance Ga of electrode 8 are 2.29 at the center frequency from the design value.
(PF) and 255 (mv), 3 (PF) to the second capacitive element C2 of 5, and the second inductive element L2 of 6
4 (no) is given for ・Under this condition, the matching capacitive element Os of 3 is
．． 7 (Pk"), and the matching inductive element L2 of 4 is set to 2.
3.4 (nH), the loss at the center frequency is 0.
18 (αβ), and 46 (αβ) for TTE suppression. Furthermore, (as shown in the frequency characteristics shown in Fig. 4), the frequency bandwidth when the TTE suppression amount is 20 (αβ) is compared with that of the first embodiment. The second capacitive element L2 can be widened by approximately s MHz.
If it is greater than fI', the frequency bandwidth at the TTE suppression amount of 20 (αβ) will become narrower, so it is desirable to set it to a value less than fI'.

The present invention has been described in detail using the above two embodiments, and each element for matching has been designed. The radiation conductance Qa and the capacitance Ct of the pole are determined, and it is sufficient to take a value that satisfies the above-mentioned complex conjugate matching.In addition, the capacitance C1 described in the present invention includes, for example, the electrode portion and the package. If there are stray capacitances between the two parts, they may be added to form Ct.

In addition, since the above explanation is for a high frequency, the inductive element IJ2 is a part or all of the inductance and capacitive element C2 of the wire as a stray capacitance, but the invention is not limited to this. When used at low frequencies where capacitance and the like are not a big problem, the frequency bandwidth with low ripple can be widened by providing the capacitive element C2 and the inductive element L2.

Further, although the above description describes a three-electrode type configuration, it may be used for other elastic surface fL iron-clad pots aimed at low loss and low ripple.

〔Effect of the invention〕

According to the present invention, by a simple matching method, the test conjugate matching seen from the conductance of the external circuit and the complex conjugate matching seen from the radiation conductance of xm can be simultaneously achieved, and a frequency band with low ripple can be achieved. Since it can be made wider, it can contribute to lower loss and ripple in surface acoustic wave devices.

[Brief explanation of the drawing]

FIG. 1 is a basic equivalent circuit diagram of the matching method according to the present invention, and FIG.
The figure is a basic configuration diagram of a surface acoustic wave device using a 3'IE other type m configuration, Figure 3 is a frequency characteristic diagram of the first embodiment when matching is performed using the equivalent circuit according to the present invention, and Figure 4 is a frequency characteristic diagram according to an embodiment. 2...Electric? l@(external circuit) 1111J conductance 3... Capacitive element for matching 4... Inductive element for matching 5... Capacitive element for matching 6 ... Stray capacitance between pin and package 7...
... Wire inductance 8 ... Electrode capacitance 9 ... Electrode radiation conductance is extremely large, T lower E
Its pq total (09ri)

Claims (1)

[Claims] 1. A first wave transmitting/receiving electrode in which one or more comb-shaped electrode groups are electrically connected is provided on a piezoelectric substrate, and an elastic surface is connected to the first wave transmitting/receiving electrode. In a surface acoustic wave device comprising a second wave transmitting/receiving electrode electrically connected to one or more comb-shaped electrode groups for transmitting and receiving waves, at least the first wave transmitting/receiving electrode and the wave transmitting/receiving electrode are A first inductive element L_1 and a second inductive element L_2 connected in series between a connected external circuit having a conductance Gl.
is connected in series between the wave transmitting/receiving electrode and the conductance Gl of the external circuit, and the second inductive element L_
the first inductive element L_1 on the side that is not the connection point with 2;
and a capacitive element L in parallel with the conductance Gl of the external circuit at the connection point with the conductance Gl of the external circuit.
_1 is connected, and a capacitive element L_2 is connected in parallel to the conductance Gl of the external circuit to the connection point between the first inductive element L_1 and the second inductive element L_2, and the The admittance seen from the radiation conductance Ga of the first wave transmitting/receiving electrode to the conductance Gl side of the external circuit, the radiation conductance Ga, and the capacitance Ct of the first wave transmitting/receiving electrode constitutes complex conjugate matching. , the inductive element and the capacitive element are determined, or the inductive element and the capacitive element are determined and used as a matching circuit, and the radiation conductance Ga and the electrostatic capacitance Ct are determined. surface wave device. 2. The second inductive element L_2 is the inductance of the wire connecting the bonding pad of the electrode part and the input/output pin of the package, the inductance printed on the piezoelectric substrate, or both. A surface acoustic wave device according to claim 1. 3. The surface acoustic wave device according to claim 1, wherein part or all of the second capacitive element L_2 is a stray capacitance between a pin of the package and a surface of the package on which the device is mounted. . 4. The second inductive element L_2 is the inductance of the wire connecting between the bonding pad of the electrode part and the input/output pin of the package, or the inductance printed on the piezoelectric substrate, or both, and the second inductive element L_2 is 2. The surface acoustic wave device according to claim 1, wherein part or all of the elastic element L is a stray capacitance of a pin of the package and a surface of the package on which the device is mounted. 5. Claim 1 or Claim 2 characterized in that the number of the first wave transmitting/receiving electrode is one, and the second wave transmitting/receiving electrode is arranged on both sides of the first wave transmitting/receiving electrode. A surface acoustic wave device according to claim 3 or claim 4.