JPS6216561B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-high frequency circuit composed of a plurality of semiconductor circuits including semiconductor elements or internal matching circuits.

Semiconductor circuits, so-called microwave integrated circuits, which incorporate a semiconductor element and an internal matching circuit into one package, can eliminate the harmful effects of stray capacitance parasitic on the package, so they are small, high-performance, and highly reliable. Can configure high frequency circuits.

However, when configuring an ultra-high frequency circuit by putting the semiconductor circuit and the line connecting the circuits in one shield case, when the dimensions inside the shield case are large, especially when the frequency is about half a wavelength or more of the required frequency, There were problems such as adverse effects such as abnormal resonance on the circuit operation. This is because the inside of the shield case operates as one waveguide, and the high frequency signal radiated from the connection between the semiconductor circuits is propagated without using the connection line.

Traditionally, the way to solve such problems is to
Various methods have been used to attach resistors or radio wave absorbers inside the shield case to absorb unnecessary propagation signals. However, these methods inherently require NF to absorb the desired signal as well.
This has caused problems such as deterioration of the power supply and reduction of output power.

The present invention solves the above problems, and its purpose is to eliminate unnecessary waveguide mode propagation without any loss of the required signal, and to achieve stable operation and reproducibility. Our goal is to provide high-quality ultra-high frequency circuits.

In order to achieve the above object, the ultra-high frequency circuit according to the present invention connects a semiconductor circuit in which a semiconductor including a semiconductor element and an internal matching circuit is hermetically sealed with a TEM mode transmission line such as a microstrip line,
In an ultra-high frequency circuit consisting of an outer core that electrically shields these, the semiconductor circuit is fixed with a metal fitting having a width of 1/4 wavelength in a direction substantially orthogonal to the transmission path, and the transmission path of the semiconductor circuit portion is By setting a large ratio between the height of the transmission line and the height of the transmission line in which the metal fitting is arranged, the propagation of signals due to unnecessary waveguide modes generated in the ultra-high frequency circuit is prevented.

According to the above configuration, the object of the present invention can be completely achieved.

The present invention will be described in more detail below with reference to the drawings and the like.

Figure 1 is a diagram of the semiconductor circuit inside the shield case as seen in the direction of the signal transmission path, where 1 is the semiconductor circuit, 2
Reference numeral 3 indicates a shield case housing the semiconductor circuit 1, and 3 indicates a lid of the shield case.

The part indicated by L in the figure is the longest, and when the inside of the case is used as a waveguide for propagating ultrahigh frequencies in the direction of the signal transmission path, this part becomes the determining factor for the low limit frequency. When the transmission band of the tube mode and the required signal frequency are so close that they overlap, unnecessary propagation occurs.

Figure 2 is a diagram showing an embodiment of the ultra-high frequency circuit according to the present invention, in which figure a is a cross-sectional view of the ultra-high frequency circuit seen from a direction perpendicular to the transmission line, and figure b is a cross-sectional view seen in the direction of the transmission line. It is. In the figure, parts corresponding to those in FIG. 1 are designated by the same reference numerals.

In order to prevent the above-mentioned unnecessary propagation, a metal fitting 6 having a shape as shown in FIGS. 2a and 2b is attached to the semiconductor circuit 1 connected to the connection lines 4 and 5.

When considering the waveguide impedance by considering the inside of the shield case as one waveguide, as shown in FIG. Since the waveguide is mounted with a small gap, the waveguide impedance in the mounting bracket section is sufficiently small compared to other parts.

This impedance relationship will now be expressed by a formula with reference to FIG. 2a. Semiconductor circuit 1 and mounting bracket 6
The waveguide impedance formed _by
c (Here, Z _c 〓Z _0. ) Mounting bracket 6 and lid 3
Let Z _l be the waveguide impedance formed by (Z _l ≪ _{Z 0.} ) If Z _s is the impedance seen from one side of the mounting bracket 6 toward the mounting bracket 6 side, and assuming that the propagation path is lossless, λ represents the wavelength of that frequency. Then, Z _s = Z _l [Z ₀ /Z _l +jtan (2πl/λ)] / [1+jZ ₀ /Z _l tan (2πl/λ)] ...(1) Z _s /Z ₀ = (Z _l / Z ₀ ) [Z ₀ /Z _l +jtan (2πl/λ)]/[1+jZ ₀ /Z _l tan (2πl/λ)] ...(1)'.

Therefore, from formula (1)′, l=(1/4+n/2)λ(n=0, 1, 2,
3,...) Z _s /Z ₀ =Z _l ² /Z ₀ ² ...(2) Since Z _l /Z ₀ <<1, Z _s /Z ₀ <Z _l /Z ₀ <<1 ...(3) Become.

If the height of the waveguide at the Z ₀ section is H ₀ and the height of the waveguide at the Z _l section is H _l , then H _l /H ₀ =Z _l /Z ₀ ...(4), so the propagation loss Calculating the loss, loss=1−|[Z ₀ /Z _s −1]/[Z ₀ /Z _s +1]| ² …(5) loss=1−|[(H ₀ /H _l ) ² −1 ] / [(H ₀ /H _l ) ² +1] | ² ...(5)' From equation (5)', when H ₀ /H _l = 2, loss = 0.64 (approximately -1.94dB) H ₀ /H _l = 4, loss = 0.022 (approximately -6.55dB). To prevent unnecessary propagation, Z ₀ and Z _s
It is good if the ratio of is large and mismatched, so
From (5) and (5)', the ratio of Z _l and Z ₀ is large, that is, H _l and
Since the ratio of H ₀ is large, the length l of the mounting bracket 6 is (1/4+n/2)λ (n=0, 1, 2, 3,...
), unnecessary propagation can be prevented.

By configuring the mounting bracket in this way, when applied to an amplifier with the semiconductor circuit structure described above in an ultra-high frequency circuit, for example, coupling due to signal radiation from the input/output connection line due to unnecessary waveguide mode can be removed. This is effective in reducing input/output interference, which was a problem in the past, and allows the characteristics of semiconductor circuits to be fully utilized without impairing signal loss due to ultra-high frequency absorbers.

It is also highly effective in preventing abnormal resonance and abnormal oscillation, which often occur in high-gain multi-stage amplifiers.

If such unnecessary waveguide mode propagation can be removed, the size of the shield case can be increased, which increases the degree of freedom in designing the shield case and improves work efficiency. In addition, by selecting the length of the mounting bracket 6 to be 1/4 wavelength, the effect of equation (3) can be expected, so the gap between the lid 3 and the mounting bracket 6 does not need to be highly accurate, and in terms of dimensional accuracy. It can also be expected to have production effects such as increased tolerance.

FIG. 3 is a diagram showing another embodiment of the present invention.
Even when two or more mounting brackets are attached to a semiconductor circuit as in this example, the object of the present invention can be achieved.

FIG. 3 is a cross-sectional view seen in the direction of the transmission line, and parts corresponding to those in FIG. 2 are given the same reference numerals.

With such a structure, the effect shown in FIG. 2 is doubled at 6' and 6'', so that the effect of blocking unnecessary waveguide mode propagation becomes even greater.

As explained above, according to the present invention, unnecessary propagation modes can be effectively removed without any loss of the required signal, and since the structure can be constructed with good productivity, a high-performance and inexpensive ultra-high frequency circuit can be constructed. There are advantages.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the semiconductor circuit inside the shield case as seen in the direction of the signal transmission path, Figure 2 is a diagram showing an embodiment of the ultra-high frequency circuit according to the present invention, and figure a shows the semiconductor circuit with mounting brackets attached. A cross-sectional view of the circuit viewed from a direction perpendicular to the signal transmission path, and FIG. FIG. 3 shows a second embodiment of the present invention, and is a sectional view of a semiconductor circuit with two mounting fittings, viewed from a direction perpendicular to the signal transmission path. 1... Semiconductor circuit, 2... Shield case, 3
... Lid, 4, 5 ... Connection wire, 6, 6', 6'' ... Mounting bracket.

Claims (1)

[Claims] 1. In an ultra-high frequency circuit consisting of a semiconductor circuit in which a semiconductor including a semiconductor element and an internal matching circuit is hermetically sealed, connected by a TEM mode transmission line such as a microstrip line, and an outer shell that electrically shields these, Fixing the semiconductor circuit with a metal fitting having a width of 1/4 wavelength in a direction substantially perpendicular to the transmission line, and increasing the ratio between the height of the transmission line in the semiconductor circuit portion and the height of the transmission line on which the metal fitting is arranged. An ultra-high frequency circuit characterized in that the ultra-high frequency circuit is configured to prevent signal propagation due to unnecessary waveguide modes generated within the ultra-high frequency circuit.