JPS59128804A - Inter-digital connector - Google Patents

Abstract

PURPOSE:To vary the connection degree by forming an epitaxial layer under the fingers opposite to each other and then forming a Schottky and ohmic junction surfaces alternately to the interface between the opposite fingers and the epitaxial layer. CONSTITUTION:The metallic films are formed on a dielectric substrate 10 by a vapor deposition process, etc. to obtain terminal lines 5 and 6, fingers 7 and 8 and an earth surface 9. An epitaxial layer 19 is provided under the fingers 7 and 8, and at the same time a Schottky junction surface and an ohmic junction surface are formed to the interfaces between the finger 7 and the layer 19 and between the finger 8 and the layer 19 respectively. The extension of a depletion layer 21 is varied with control of a bias power supply. Such an inter-digital connector is used to vary the voltage impressed between the opposite fingers 7 and 8, and therefore the connection degree can be varied.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in interdigital couplers for use in microwave integrated circuits, including monolithic microwave integrated circuits.

The structure of a conventional interdigital coupler is shown in FIGS. 1 and 2. FIG. 1 is a perspective view, and FIG. 2 is a sectional view of FIG. 1 taken along the plane AA'. In Figure 1, (1) is the first terminal, (2) is the second terminal, (3) is the third terminal, (4) is the fourth terminal, and (5) is the first terminal line. , (6) is the second terminal line.

(7) is the first finger. (8) is the second finger.

(9) is the ground plane, and QG is the dielectric substrate. A first terminal line (5), a second terminal line (6),
The first finger (71, second finger (8), and ground plane (9) are constructed by providing a metal film on the dielectric substrate (I) by vapor deposition or the like.
) is an input terminal, the second terminal (21 is an isolation terminal, and the third terminal (3) and fourth terminal (4) are output terminals.

FIG. 3 is an even mode equivalent circuit diagram of the first terminal line (5), and FIG. 4 is an odd mode equivalent circuit diagram of the first terminal line (51).

In Fig. 3, αl) is the even mode equivalent terminal line, (+2 is the even mode inductance Le, α3 is the even mode capacitance Ce, and 041 is the connection between the first terminal line (5) and the first finger (7). This is the expected even mode finger admittance Yfe.In addition, in Fig. 4, +149 is the odd mode equivalent terminal line, Tsukuda is the odd mode inductance LOt, αη is the odd mode capacitance CO, and a・ is the first terminal line (5). is the odd mode finger admittance Yfo looking into the first finger (7) from .

Note that even mode finger admittance (141), odd mode finger admittance (141), or first finger (7
This is caused by the bond between the first and second fingers (8).

Even-7-dead equivalent terminal line α11. Even mode characteristic impedance Zce of odd mode equivalent terminal line a5,
The odd mode %41 impedance ZCO is given by the following formula (21).

zQe” 5 pieces; 7 fertilizers 1〒 side y ... (1) zo.=
j ”o' (j ”'O+”fO) −12
1 The coupling degree of the interdigital coupler when the length l in Fig. 1 is 1λg (where λg is the propagation wavelength) is
It is given by equation (3) using zco and zCO.

By the way, when using the above-mentioned interdigital coupler in a microwave integrated circuit, it may be necessary to vary the degree of coupling.

However, in the conventional interdigital coupler.

There was a drawback that the degree of bonding could not be easily changed.

In order to eliminate this drawback, the present invention provides an epitaxial layer at the bottom of the finger, and forms a Schottky junction surface and an ohmic junction surface alternately at the interface between the opposing finger and the epitaxial layer, thereby easily increasing the degree of bonding. This allows k to be changed.

FIG. 5 is a perspective view of an interdigital coupler according to the present invention, and FIG. 6 is a sectional view taken along the line AA' in FIG.

In FIG. 6, alpha layer is an epitaxial layer, and wire is a semi-insulating substrate. FIG. 7 is an enlarged view illustrating the principle of operation of a pair of fingers. In Figure 7, can is the depletion layer, and ■ is the bias power supply and dust.

A Schottky junction surface is formed at the interface between the first finger (7) and the epitaxial layer Ql, and an ohmic junction surface is formed at the interface between the second finger (8) and the epitaxial layer α9. Furthermore, the depletion layer C! The magnitude of the spread of υ is changed by adjusting the bias power supply port.

Changing the extent of the depletion layer (21) changes the depletion layer capacitance, and as a result, the coupling capacitance between the first finger (7) and the second finger (8) changes.

Also, as a result, the even mode finger admittance Yfe of the pot finger and the odd mode finger admittance Yfo
changes.

From the above, by adjusting the bias power supply @, Yf
It is possible to change the magnitude of e+ Yfo and 1
It can be seen from the results of equations (1) to (3) that the degree of coupling k can be changed.

Note that the case where the number of fingers is 8 and the shape of the fingers is a straight line has been described for 1 or more, but the present invention is not limited to this, and the number of fingers can be arbitrary.

It may be used when the shape of the finger is a curved line, a bent line, etc.

As described above, in the ink digital coupler according to the present invention, the degree of coupling can be changed by changing the applied voltage between the opposing fingers.
When this is used in a microwave integrated circuit including a monolithic microwave integrated circuit, there is an advantage that a coupler can be constructed whose coupling capacitance can be easily varied simply by changing the applied voltage.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a perspective view showing the structure of a conventional ink-digital coupler of this type, FIG. 2 is a sectional view taken along the plane A-A' of FIG. 3 and 4 are equivalent circuit diagrams of FIG. 1, FIG. 5 is a perspective view of an interdigital coupler according to the present invention, and FIG. 6 is a sectional view of FIG. 5 taken along the plane A-A''. Figure 7 is an explanatory diagram of the operating principle. In the figure, (1) is the first terminal, (21 is the second terminal, (3
) is the third terminal, (4) is the fourth terminal, (5) is the first terminal line, (6) is the second terminal line, (7
) is the first finger, (8) is the second finger, (
9) is the ground plane, α0 is the dielectric substrate, 'Qll is the even mode equivalent terminal line, (12 is the even mode inductance, 03 is the even mode, capacitance, α4 is the even mode finger admittance, α is the odd mode equivalent terminal line, +161 is odd mode inductance, a is odd mode capacitance, αQ is odd mode finger admittance, y is epitaxial layer, (a) is semi-insulating substrate, Qll
is the depletion layer and @ is the bias source. Note that in FIG. 1, the same or corresponding parts are designated by the same reference numerals. Agent Makoto Kuzuno - Figure 1 Figure 2 □lθ Figure 3 Figure 4 Figure 5 Figure 6 - 2θ

Claims (1)

[Claims] In an interdigital coupler used in a microwave integrated circuit, an epitaxial layer is provided at the bottom of opposing fingers, and a Schottky junction surface is provided at the interface between one of the fingers and the epitaxial layer. An interdigital coupler characterized in that an ohmic junction surface is formed on the other side.