JPS6123883B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave integrated circuit, and more specifically, to a microwave integrated circuit having a microstrip structure in which a ground conductor is provided on the lower surface of a dielectric substrate and a strip conductor is provided on the upper surface. This relates to a microwave integrated circuit in which a planar circuit having a semiconductor element or the like as a component is mounted on the strip conductor of a transmission line, and is particularly aimed at improving the shielding structure to reduce loss due to transmission signal radiation. .

In a microwave integrated circuit whose basic configuration is a transmission line with a microstrip structure, when the signal frequency becomes high, the microwave signal is radiated into the space from the space above the integrated circuit, causing a large loss.
In order to reduce loss due to this radiation, conventional methods have been adopted in which microwave integrated circuits are mounted inside a sealed metal case. FIG. 1 shows a partially exploded perspective view of a conventional microwave integrated circuit with a sealed structure. A microwave transmission line consisting of a strip conductor 2 provided on the upper surface of a dielectric substrate 1 and a ground conductor 3 provided on the lower surface is constructed such that as the frequency of the transmitted signal increases, the signal from the strip conductor 2 on the upper surface to the space above increases. radiation increases, and the loss of the transmitted signal increases rapidly. Therefore, the radiation loss has been reduced by sealing it with a metal shielding case 4. In order to reduce this radiation loss, it is necessary to place the metal plate of the shielding case 4 at a certain distance from the strip conductor 2. The above-mentioned shielding case 4 is provided separately from the housing case for the purpose of blocking interference waves from the outside.

FIG. 2 shows a cross-sectional view of a conventional microwave integrated circuit separately provided with a shielding case and a housing case. A shielding case 4 suppresses radiation loss of the microwave integrated circuit 6, and a housing case 5 that surrounds the entire device is provided separately. In the space above the microwave integrated circuit 6, the distance to the housing case 5 is too long, so the radiation loss cannot be reduced by the housing case 5 alone. Therefore, a shielding case 4 is required near the microwave integrated circuit 6 to seal it.

However, the conventional microwave integrated circuit having the above structure requires (1) a double sealed case of the shielding case 4 and the housing case 5, which is expensive, and (2) a sealed shielding case. The case has cavity-shaped resonance characteristics, and when transmitting signals near the resonance frequency of the case, the loss of the microwave integrated circuit increases abnormally, making it impossible to obtain circuit characteristics. In particular, case resonance (2) significantly increases circuit loss, so conventional countermeasures include inserting screws into the shielding case to change the resonance characteristics, and dividing the shielding case into small rooms. However, both had the disadvantage of complicating the structure.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microwave integrated circuit having a simple structure, no case resonance, and a structure capable of reducing radiation loss by eliminating the disadvantages of the prior art described above.

A feature of the present invention is that, in order to suppress radiation from a microwave integrated circuit, it is sufficient to provide a shielding metal plate in the upper space, and there is no need to seal it. The structure is such that a shielding band-shaped metal plate is arranged approximately parallel to the dielectric substrate in the space above only the circuit portion where the signal frequency is high in a planar circuit formed by attaching as a component element.

The present invention will be explained below with reference to the drawings.

FIG. 3 is a perspective view of an embodiment of the present invention, where 7 is a grounded metal plate, 8 is a main transmission line of a microwave transmission line, 9 is a 1/2 wavelength terminated open line, and 10 and 11 are input/output connectors, respectively. , 12 are shielding metal plates. The 1/2 wavelength terminated open line 9 has a 1/4 wavelength portion from one end thereof approaching the main transmission line 8 in parallel. This main transmission line 8 and 1/
The two-wavelength terminated open line 9 constitutes a band rejection filter that obtains maximum attenuation at the resonant frequency f ₀ of the 1/2-wavelength terminated open line 9, and the filter characteristics between the input and output connectors 10 and 11 in this case are as follows: is shown in Figure 4.
In FIG. 4, the broken line indicates the case where there is no shielding metal plate 12 in FIG. 3, and the solid line indicates the shielding metal plate 12.
This is the filter characteristic when . If the shielding metal plate 12 is not provided in the space above the band-elimination filter, as shown by the broken line in FIG. 4, the loss will increase due to the influence of radiation, the Q of the circuit will decrease, and the maximum attenuation will be small. On the other hand, if the shielding metal plate 12 is provided in the space above the band rejection filter, the characteristics shown by the solid line in Figure 4 will be obtained, the loss due to radiation will be reduced, the Q of the circuit will be high, and the maximum attenuation will be high. . In this way, simply by placing the shielding metal plate 12 in the space above the main transmission line 8 of the microwave transmission line, the radiation loss can be significantly reduced.Moreover, in the configuration shown in FIG. Instead, both end faces in the front and rear directions remain open, so there is no resonance caused by the closed case as in the conventional case. Furthermore, the shielding metal plate 12 placed in the upper space is
It has been confirmed through experiments that the same shielding effect can be obtained even if the potential is not the same as that of the ground metal plate 7.

A perspective view of an embodiment of the present invention obtained by applying this to a microwave integrated circuit is shown in FIG. 5, and a sectional view thereof is shown in FIG. In Figures 5 and 6, 13
is a band-shaped metal plate for shielding provided in the present invention, and is arranged parallel to the dielectric substrate 7. 14 is a housing case (not shown in FIG. 5), 15 is a frequency converter, and 16 is an amplifier. The present embodiment is a frequency conversion device supported by a grounded metal plate 7, which is composed of a frequency conversion section 15 that converts a high frequency signal into a low frequency signal, and an amplification section 16 that amplifies the converted low frequency signal. Since the radiation increases as the frequency increases, only in the space above the frequency converter 15 that handles high frequency signals,
It is sufficient to dispose the band-shaped metal plate 13 that suppresses radiation, and since the amplification section 16 that handles low-frequency signals emits small radiation, there is no need to provide the band-shaped metal plate. The housing case 14 has the function of blocking interference waves from the outside, as in the conventional case. Any supporting structure can be used to support the shielding band-shaped metal plate 13 in the space above the circuit, since the potential of the band-shaped metal plate 13 does not need to be set to the ground potential.

As explained above, according to the present invention, the shielding band-shaped metal plate is arranged in the space above only the circuit portion with high signal frequency among the planar circuits constituting the microwave integrated circuit. , the structure is simplified, case resonance is eliminated, and radiation loss can be reduced.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view of a conventional microwave integrated circuit with a sealed structure, Fig. 2 is a sectional view thereof, Fig. 3 is a perspective view of an embodiment of the present invention, and Fig. 4 shows a comparison of filter characteristics. FIG. 5 is a perspective view of another embodiment of the present invention, and FIG. 6 is a sectional view thereof. Explanation of symbols, 1... Dielectric substrate, 2... Strip conductor, 3... Ground conductor, 5, 14... Housing case, 7... Ground metal plate, 8... Main transmission line, 9
... 1/2 wavelength terminated open line, 10, 11 ... Input/output connector, 12 ... Shielding metal plate, 13 ... Shielding band metal plate, 15 ... Frequency conversion section, 16
...Amplification section.

Claims (1)

[Claims] 1. In a microwave integrated circuit comprising a microwave transmission line having a structure in which a ground conductor is provided on the lower surface of a dielectric substrate and a strip conductor is provided on the upper surface, a planar circuit having semiconductor elements, etc. as constituent elements is mounted on the strip conductor. . A microwave integrated circuit, characterized in that a shielding band-shaped metal plate is arranged substantially parallel to the dielectric substrate in a space above only the circuit portion with a high signal frequency of the planar circuit.