JPS59218002A - Resistive terminator for strip line - Google Patents

Abstract

PURPOSE:To apply the resistive terminator to a microwave IC in terms of the circuit and manufacture by matching the resistance value of a thin film resistor to the characteristic impedance and inserting a prescribed value of capacitor in parallel with a thin film resistance part. CONSTITUTION:The end of a strip line having a characteristic impedance Z0 is short-circuited through a thin film resistor 4 and the resistance value of the resistor 4 is matched to the characteristic impedance Z0. Further, the width of the resistor 4 is expanded optionally so as to establish nearly the relation of [L0l/(C0l+Ca0)]<1/2>=Z0/(3)<1/2> and a required capacitance Ca satisfying the equa tion above is inserted to a projection 9, where L0 is the inductance per unit length, C0 is the capacitance and (l) is the length.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-reflection termination for a strip line used in a microwave 10 or the like.

Currently, microwave devices are becoming significantly smaller and more reliable through the use of ICs using microphone D-strip lines and the like. In such a microwave IC circuit, a non-reflection termination with very strict characteristics is required for converting a circulator into an isolator or for an isolation port of a directional coupler.

For example, when a circulator is turned into an isolator, the reflection characteristics of the non-reflection termination directly become the isolation solar characteristics, and very good characteristics are required. For example, if the input vSW of the non-reflection termination is 1.2, it is no longer possible to obtain isolation of 20 dB or more. Also, when measuring the characteristics of coaxial-stripline converters, it would be good to be able to use IC-based non-reflective terminations, but in that case, it would be better to use non-reflective terminations that are much better than the reflection V8WR of these converters. is necessary.

Figure 1 shows a conventional thin film non-reflective termination, in which a grounding conductor film 2 and a line conductor film 3 are formed on the lower surface of a dielectric substrate 1. At the end of a microstrip line, a characteristic impedance (usually 50Ω) is applied. Thin film resistors 4 having equal resistance values were formed and grounding was performed using a shorting conductor 5. In this case, the shape of the thin film resistor is designed without regard to the high frequency characteristics; it may be simplified by making it the same width as the microstrip conductor as shown in (a), or it may be made into a mesh-like diamond shape as shown in (bl) to improve the power characteristics. However, the resistive film itself has a small amount of inductance, and there is also a small amount of capacitance between it and the ground conductor. Therefore, at very low frequencies, these unnecessary reactances can be ignored. However, at high frequencies such as microwaves, the resistance value cannot be ignored and unnecessary reflections occur, which is a problem.

Even at low frequencies such as the UHF band, the size of high-power non-reflection terminations increases, and as a result, their unnecessary inductance or unnecessary capacitance cannot be ignored.

Conventionally, it has been unclear how to design a non-reflection termination including these, so it has not been possible to use a non-reflection termination for an IC with guaranteed characteristics that are sufficiently good in the microwave band. Therefore, the non-reflection termination shown in Figure 1 is used only in places where very strict characteristics are not required, and in places where strict characteristics are required, after converting to coaxial using a connector, a coaxial type non-reflection termination is used. was often used.

The purpose of this application is to provide a non-reflection termination with extremely good characteristics that can be applied to microwave ICs in terms of circuitry and manufacturing, based on a design method for a non-reflection termination that includes unnecessary reactance. It is in.

According to the present invention, in the non-reflection termination in which the terminal end of a strip line with a characteristic impedance Zo is short-circuited through a thin film resistor, the resistance value of the thin film resistor is adjusted to the characteristic impedance zo, and the thin film resistor is connected in parallel to the thin film resistor part. When replacing with a conductor film of the same shape, the inductance per unit length is 0, the capacitance is co, and the length is l,
A reflection-free termination for a strip line is obtained, which is characterized in that a capacitor Ca is inserted so that the outline holds true.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a perspective view showing a non-reflective termination used to explain the present invention. In the figure, the non-reflective termination is comprised of a dielectric substrate 1, a grounding conductor film 2, a line conductor film 3, a thin film resistor 4, and a shorting conductor 5.

Now, consider a thin film resistor of length l as shown in Figure (a) as a lossy distributed constant line, and calculate its input impedance Z.

When calculating, zi=ZB tanh rll (
1), where ZR is the resistance characteristic impedance, γ is its propagation constant, angular frequency is ω, resistance per unit length of the thin film resistor is the formula, inductance is Lo, and capacitance with ground is co. Then) γ=6−translator■δ (3). However, v''T=j.

Now l is sufficiently small and considering that the thin film resistance is a lumped constant, γl
If <A, equation (1) is transformed as follows using equations f2) and f3). (4) Furthermore, in equation (4), since the propagation constant value is small, it is transformed as follows. .

From the above equation, the thin film resistor section can be completely represented by an isometric circuit as shown in FIG. 3 using lumped constant LC elements.

In this case, if the relationship oz=zo+61 is maintained, a good reflection-free termination can be obtained. 5゜Ω) When using a thin film resistor coaxial with the IJ tube line conductor, the reason why unnecessary glue actance occurs is due to the capacitance in this case,
This is probably because Col is not large enough to satisfy equation (7).

Therefore, by adding another parallel adjustment capacitor Ca to the thin film resistor section as shown by the dotted line in Figure 3, and formula 6) is obtained, even when the width of the thin film resistor section is arbitrary, , a good reflection-free termination can be obtained.

FIG. 4 1a) is a diagram showing a first embodiment of the present invention based on the above-mentioned principle, in which the width of the thin film resistor 4 is arbitrarily widened and the convex portion 9 is used to provide the required capacitance Ca that satisfies the equation (8). It is something that

(bl is another dielectric material lo placed on the thin film resistor 4 to provide the required capacitance Ca, tc) is this adjustment dielectric material l
A thin film resistor 4 is formed on O, and it is easy to put it into practical use if the thickness and dielectric constant of the dielectric 10 are adjusted and formula 8) is satisfied.

FIG. 5 is a diagram showing still another second embodiment, in which equation (6
), the adjustment screw 11 is brought close to the top of the thin film resistor 4 that satisfies (8), and the required capacitance Ca that satisfies equation (8) is added. In this case, Lol also changes.

It is practical because the required iCa can be provided while observing the characteristics from the screw number without having to strictly design the pattern. 55 is a short circuit terminal.

Although FIGS. 4 and 5 only show the implementation of either the microstrip type or the suspended triplate type, the principles of the present application can also be applied to the triplate type and microstrip type, respectively, other than those shown. Needless to say.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional thin film non-reflective termination (a). (bl is separate plan view, (C) is their center line AA'
FIG. 1 is a dielectric substrate, 2 is a grounding conductor film, 3 is a line conductor film, 4 is a thin film resistor, and 5 is a shorting conductor film. FIG. 2 is a perspective view showing a non-reflective termination used to explain the present invention. Components that are the same as those for the first factor are indicated with the same symbols. (Similarly below) FIG. 3 is an explanatory equivalent circuit diagram. FIG. 4 is a diagram showing the first embodiment, in which ta), (bl
is a plan view, and (C) is a cross-sectional view. 9 is a line conductor convex portion;
10 is a dielectric. FIG. 5 is a sectional view showing the second embodiment, in which 6.6' is a grounding conductor, 11 is an adjustment screw, and 55 is a shorting terminal. Figure 71 AA' cross section Figure 2 Figure 73

Claims (1)

[Claims] The resistance value of the thin film resistor is adjusted to the characteristic impedance Zo at the non-reflection termination where the end of the strip line with the characteristic impedance Zo is short-circuited through the thin film resistor, and the same thin film resistor is connected in parallel to the thin film resistor part. A non-reflection termination for a strip line, characterized in that a capacitance Ca is inserted so that an outline holds true when the inductance per unit length is Lo, the capacitance is co, and the length is l when replaced with a shaped conductor film.