JPH0455002B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention propagates surface waves in mutually opposing directions from input transducers provided near both ends of a substrate, facing each other. Differential Phase Shift with an output gate consisting of two tracks between their input transducers
Keying (hereinafter abbreviated as DPSK) convolver.

B. Summary of the Invention In a DPSK convolver consisting of two tracks, the two divided output gates on one track are directly connected, and the two divided output gates on the other track are connected via a balanced-unbalanced converter. A surface acoustic wave convolver is disclosed. The convolver can be an elastic convolver or a monolithic convolver made of a piezoelectric film formed on a semiconductor substrate.

C. Prior Art Conventional surface acoustic wave convolvers include (a) a separation medium convolver that couples a semiconductor and a piezoelectric material through a small gap, (b) an elastic convolver that utilizes the nonlinearity of the piezoelectric substrate itself, (c) A monolithic convolver with a layered structure in which a piezoelectric thin film is formed on a semiconductor substrate is known.

The separation medium convolver shown in (a) has the disadvantage of poor productivity because it is very difficult to control the air gap. The elastic convolver shown in (b) requires large surface acoustic wave energy to utilize the elastic nonlinearity of the piezoelectric substrate. On the other hand, unlike the separation medium female convolver, the elastic convolver and the layered structure convolver have the advantage of being easy to assemble and increasing productivity.
Furthermore, the monolithic convolver shown in (c) utilizes the nonlinearity of the depletion layer capacitance of a semiconductor, so it has a high convolution efficiency, and has the advantage of being easy to configure due to its monolithic structure. .

A cross-sectional view of the monolithic structure is shown in FIG. 4, and a top view is shown in FIG. Here, 1 is a semiconductor layer such as silicon, 2 is a piezoelectric film such as zinc oxide or aluminum nitride, 3 is an input transducer for surface acoustic waves, and 4 is a piezoelectric film such as zinc oxide or aluminum nitride.
is an output gate, and the transducer 3 and gate 4 are formed of a metal film such as aluminum.

For example, use Spread as a surface acoustic wave convolver.
It is widely known that it can be applied as a signal processing functional element such as Spectrum Communication (hereinafter abbreviated as SSC). DPSK is often used for data modulation to be transferred in SSC.

In order to convert such a DPSK-modulated signal into a matched wave using a surface acoustic wave convolver, a convolver having the structure shown in FIG. 6 has been proposed. The structure shown in Figure 6 is called a DPSK convolver, and its detailed operation is described by D. Brodtkorb.
and written by JELaynor
The magazine Ultrasonics Symbosium Proceedings was published in 1978.
Symposium Proceedings), pages 561 to 566. In FIG. 6, 5 and 6 are output gates, which are separated at the center. 7 is a hybrid for calculating the sum and difference of the signals from both gates 5 and 6. 8,
9 is the hybrid output, 8 is the sum (Σ _put ),
9 outputs the difference ( _Δput ).

D. Problems to be Solved by the Invention Since the SSC receiver using the DPSK convolver having the configuration shown in FIG. 6 uses a hybrid 7, it has the disadvantage that it is very expensive.

Therefore, it is an object of the present invention to provide an inexpensive surface acoustic wave DPSK convolver.

E. Means for Solving the Problems In order to achieve the above object, the surface acoustic wave device according to the present invention includes an output gate divided into two parts corresponding to each of the tracks, and two gates corresponding to one track. The gist of the present invention is to include a first output circuit that directly connects two output gates, and a second output circuit that connects two output gates corresponding to the other track via a balance-unbalance converter. The substrate can be a piezoelectric material or a composite layer consisting of a semiconductor layer and a piezoelectric layer.

F Effect If the two divided output gates in one track are connected directly, a sum signal will be obtained, and if they are connected through a balanced-unbalanced converter, a difference signal will be obtained.

G Embodiment FIG. 1 is a top view and electrical connection diagram of a DPSK convolver according to the present invention.
2 and 13 are output gates, 14 is a balanced-unbalanced converter, 15 is a sum output, and 16 is a difference output.

As shown in FIG.
An output gate 10 consisting of two tracks between its input transducer 3 over a crossing width of
and 11, 12, and 13 are arranged. That is, output gates 10 and 11 form one track, and output gates 12 and 13 form another track. input transducer 3,
The output gates 10, 11, 12, and 13 are made of metal such as aluminum.

In such a two-track DPSK convolver, the output gates on one track, e.g.
If 0 and 11 are concatenated, output signal 15 will be generated, and if output gates 12 and 13 in the other track are concatenated via balance-unbalance converter 14, output signal 16 will be generated.

By performing the above-described connection, the sum signal of the output gates 10 and 11 is obtained from the output signal 15, and the difference signal of the output gates 12 and 13 is obtained from the output signal 16. That is, the configuration shown in FIG. 1 makes it possible to form a DPSK convolver with equivalent functionality using a single inexpensive balanced-unbalanced converter without using the expensive hybrid 7.

The method of obtaining the sum and difference outputs using the two-track DPSK convolver shown here can be applied to both types of elastic convolver and layered structure convolver. That is, for an elastic convolver, as shown in FIG. 2, the input transducer 3 and output gates 10, 11, 12, 13 shown in FIG. 1 are formed on a piezoelectric substrate 17 made of lithium niobate or the like. good.

Regarding the layered convolver, as shown in FIG. 3, a piezoelectric film 19 made of zinc oxide, aluminum nitride, etc. is formed on a semiconductor substrate 18 made of silicon, etc., and an input transducer 3 and output gates 10, 11, etc. are formed thereon. 12 and 13 may be configured as shown in FIG.

H. Effects of the Invention As explained above, according to the present invention, a DPSK surface acoustic wave convolver can be realized using an inexpensive balanced-unbalanced converter instead of an expensive hybrid element.

[Brief explanation of the drawing]

FIG. 1 is a top view and electrical connection diagram of a DPSK convolver according to the present invention, FIG. 2 is a cross-sectional view of an elastic convolver according to the present invention, FIG. 3 is a cross-sectional view of a layered structure convolver according to the present invention, and FIG. 5 is a top view of the device shown in FIG. 4, and FIG. 6 is a sectional view of a conventional monolithic convolver.
FIG. 3 is a top view of the DPSK convolver. 3...Input transducer, 10, 11, 1
2, 13... Output gate, 14... Balanced-unbalanced converter, 15... Sum output, 16... Difference output, 1
7... Piezoelectric substrate, 18... Semiconductor substrate, 19... Piezoelectric film.

Claims (1)

[Claims] 1. Surface waves are propagated in mutually opposing directions from input transducers provided near both ends of the substrate, and two In a surface acoustic wave device used as a DPSK convolver equipped with an output gate consisting of two tracks, (a) an output gate divided in the center corresponding to each of the above tracks, (b) one track (c) a second output circuit that directly connects two corresponding output gates; and (c) a second output circuit that connects two corresponding output gates of the other track via a balanced-unbalanced converter. A surface acoustic wave device featuring: 2. The surface acoustic wave device according to claim 1, wherein the substrate is a piezoelectric material. 3. The surface acoustic wave device according to claim 1, wherein the substrate is a composite layer consisting of a semiconductor layer and a piezoelectric layer.