JPH0262102A - Short stub matching device - Google Patents

Abstract

PURPOSE:To cancel an inductive reactance with a desired frequency by serially connecting a capacitor to the inductive reactance incidental to a short stub used for an impedance matching circuit. CONSTITUTION:A capacitor 12 is connected serially between a microstrip line 5 and a reactance 9. At this time, when the static capacity of a capacitor 12 is C, a load ZL' in a B point can be shown by an expression. Provided that omegais an angle frequency and an L is an inductance incidental parasiticly to a short stub. Here when the static capacity C of the capacitor 12 is selected to C=1/omega<2>L, the load ZL' in the B point becomes zero. Consequently, in the desired frequency, the short stub to show the input impedance equal to a complete short stub can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a short stub matching device used in impedance matching circuits of microwave amplifiers, mixers, etc.

Conventional technology Conventionally, microwave integrated circuits have used hybrid integrated circuit technology in which active elements such as field effect transistors and individual components such as microstrip lines are mounted on an insulating substrate, but in recent years monolithic integrated circuit technology has been used, which is suitable for mass production. Microwave integrated circuits have come into practical use. Conventional examples of short stubs in this monolithic microwave integrated circuit are shown in FIGS. 3 and 4. FIG. 3 is a plan view of a short stub in a monolithic microwave integrated circuit, and FIG. 4 is an equivalent circuit diagram of FIG. 3.

In these figures, (1) is a semi-insulating semiconductor substrate, and on the surface of the substrate (1) there are active elements (2) such as field effect transistors, microstrip lines (3) (
4), (5), etc. are integrated, and one end of the microstrip line (5) is connected to a grounding base plate (not shown) with a bonding wire (6).

In such a configuration, a parasitic inductive reactance is created by the bonding wire (6).

The dotted line frame (8) in FIG. 4 indicates the inductive reactance (9) parasitically attached to the short stub consisting of the microstrip line (5) by the bonding wire (6).

Since the conventional short stub matching device that is intended for this purpose has a configuration as shown in FIGS. 3 and 4, there is a problem that it does not become a perfect short stub due to the inductive reactance (9) caused by the bonding wire (6). was there.

Generally, as shown in FIG. 5, one end (B
), if the load θ0 is connected to the transmission line 00)
The input impedance (Zin) at the other end (A) can be expressed by the following equation.

Zin=Zo(Zt+jZotanθ)/(Zo+jZ
Ltanθ) However, Zo is the characteristic impedance of the transmission line 0ω+ZL is the impedance of the load θ0, and θ is the phase angle between AB of the transmission line 00).

When zL=0, the transmission line ODD becomes a complete short stub, but in the case of Figures 3 and 4, if the inductance of the bonding wire (6) is (L), the load ZL at point B is ZL = jωL (where ω is the angular frequency), so it is not a perfect short stub. The larger the inductance (L) of the bonding wire (6) and the higher the frequency, the more the input impedance (Zin) deviates from the input impedance of a perfect short stub.

The present invention was made to solve the above problems, and an object of the present invention is to provide a short stub matching device that exhibits an input impedance equivalent to that of a complete short stub.

In order to solve the above-mentioned problems, the present invention aims to eliminate the inductive reactance associated with the short stub at a desired frequency in a short stub matching device used in an impedance matching device for a monolithic microwave integrated circuit. A capacitor exhibiting such a capacitance is connected in series with the inductive reactance.

- ■ Therefore, if we understand the capacitance of the capacitor and use the capacitance to cancel the inductive reactance associated with the short stub at a desired frequency, the load Z connected to the short stub at that frequency can be reduced.
L can be made approximately zero, and characteristics equivalent to those of a complete short stub can be obtained.

Back JLJL FIG. 1 is an equivalent circuit diagram of an embodiment of the present invention.

In FIG. 1, parts corresponding to the conventional example shown in FIG. 3 are given the same reference numerals.

The embodiment of the present invention shown in FIG. 1 differs from the conventional example shown in FIG. 3 in that a capacitor Q2) is connected in series between the microstrip line (5) and the actance (9). In this case, assuming that the capacitance of the capacitor 021 is C, the load ZL' at point B can be expressed by the following equation.

ZL'=j(ωL-π) However, ω is the angular frequency, and L is the inductance parasitically attached to the short stub.1 Note that the inductance parasitically attached to the short stub 0ω is, for example, This is the inductance exhibited by the bonding wire itself.

In the above equation, if the capacitance of capacitor 021 is chosen to be C@C=1/ω2L, the load Z at point B is
L' becomes zero. Therefore, it is possible to obtain a short stub that exhibits the same input impedance as a complete short stub at a desired frequency. Incidentally, an example of a structure in which the capacitor 021 is provided is shown in FIG. 3A is a plan view of the short stub matching circuit, and FIG. 1B is a cross-sectional view of the short stub matching circuit. In this embodiment, the end portion (5a) of the short stub (5) is a lower layer metal, the grounding bonding wire (6) is a rising metal, and an insulator 03) is arranged between them. ) end (5
The vertical positions of a) and the bonding wire (6) may be interchanged.

According to the present invention, with a simple configuration in which a capacitor is connected in series with an inductive reactance attached to a short stub used in an impedance matching circuit, the capacitance of the capacitor can be canceled out by the reactance at a desired frequency. By setting the input impedance to a value that is equal to or greater than 1, it is possible to obtain a short stub with an input impedance equivalent to that of a complete short stub, and the reliability of the impedance matching circuit is improved.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a structural example of the present embodiment, FIG. 3 is a plan view of a conventional example, FIG. 4 is an equivalent circuit diagram of a conventional example, and FIG. FIG. 5 is an explanatory diagram of the operation of FIG. 4. (2)--Load, (3) (4) (5)--Transmission line. (6) --- Bonding wire. (9) - Inductive reactance parasitically attached to the short stub. 02)...~Capacitor, Q3)--Insulator. Applicant Sharp Corporation

Claims (1)

[Claims] (1) In a short stub matching device used in an impedance matching circuit of a microwave circuit, a capacitor exhibiting a capacitance that can cancel the inductive reactance accompanying the short stub at a desired frequency is placed between the short stub and the reactance. A short stub matching device is provided.