JPH028402Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a microwave board circuit with a suspended substrate stripline structure using a dielectric substrate whose back surface is covered with a conductor whose back surface is at least 1/3 grounded. be.

Conventionally, this type of microwave board circuit has a structure as shown in the perspective view of FIG. In addition, if high line impedance is required, the second
As shown in the figure, if the ground conductor on the back side is removed and low line impedance is required, the third
As shown in the figure, the structure was such that a ground conductor was left on the back side. This structure has the characteristic that it is possible to realize an extremely wide range of line impedances compared to a circuit with a microstripline structure. This circuit is used in microwave filters, etc., and although it has better characteristics than microwave filters with a microstripline structure, its application range is limited to extremely narrow areas such as filters. Ta.

More specifically, as shown in Fig. 2, conventional microwave circuits with a suspended substrate stripline structure do not originally place conductors on the back side of the board, but instead place conductors on the front or back side of the board circuit, or on the back side of the board circuit. A microwave circuit is constructed by placing circuit patterns on both sides. However, as shown in Figure 3, as a structure for supporting microwave board circuits, sometimes a conductor is placed on a part of the back side of the board circuit (for example, about 1/10 area of the back side), and this conductor is By soldering or brazing the microwave circuit board and the substrate support, a structure may be obtained in which the microwave circuit board is fixed. In this case, the part of the front surface corresponding to the part where the conductor is placed on the back side is an ineffective area that cannot be used as a microwave circuit with a conventional suspended substrate stripline structure. Conventionally, the design was to minimize the amount of noise as much as possible. This ineffective area is 1/10 or less of the back surface, and does not exceed 1/5 at most.

The microwave circuit of the present invention has a suspended substrate stripline structure, in which a ground conductor (ground part) is placed on the back side of the board, and a board surface conductor is placed on the surface corresponding to that part. It is possible to make the impedance a capacitive low impedance. Furthermore, by arranging a substrate surface conductor on the back surface of the substrate corresponding to a portion (open portion) where no ground conductor is provided, it is possible to make the characteristic impedance of the conductor high inductance. By utilizing the feature that this characteristic impedance can be set to a low value or a high value, a microwave circuit with good characteristics that could not be realized with conventional microwave circuits can be realized. However, if the ground conductor of the board is less than 1/3, the surface conductor of the board with low characteristic impedance becomes extremely small, and these characteristics of the microwave circuit cannot be achieved with the conventional structure described above. There will be virtually no difference.

Therefore, the purpose of this invention is to install components such as diodes, transistors, capacitors, and resistors on a dielectric substrate whose back surface is covered with a grounding conductor, and thereby create circuits such as microwave mixers and amplifiers. The purpose is to provide a microwave board circuit with good characteristics.

The microwave board circuit devised in this application has 1/3 on the back side.
The low-pass filter has a suspended substrate stripline structure using a dielectric substrate composed of a grounded part and an open part, and the low-pass filter is connected to the ground part facing the ground part. It consists of a capacitive low impedance line section formed on the upper surface of the dielectric substrate, and an inductance high impedance line section formed on the upper surface of the dielectric substrate facing the open section.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 4 is a perspective view of an embodiment of the present invention, in which a microwave mixer is constructed by a low-pass filter and a diode connected to this filter.
5 is a plan view of the front conductor of FIG. 4, and FIG. 6 is a plan view of the back conductor. In the figure, 1 is a ground conductor, 2 is a dielectric substrate, 3 is a front conductor, 4 is a back conductor, 5 is a through hole, 6 is an external diode,
7 represents a strip conductor.

FIG. 7 is a diagram showing the attenuation characteristics of the low-pass filter used in this embodiment, showing good blocking characteristics of the filter up to high frequencies, showing the characteristics of a suspended substrate stripline circuit. Furthermore, Fig. 8 is an actual measurement characteristic diagram of the conversion loss of the microwave mixer according to the embodiment of this invention.
The band is wider than 1 GHz compared to 500 MHz or below, making the most of the wide band characteristics of the low-pass filter.

That is, in the measured characteristic diagram of FIG. 8, when looking at the frequency range where the conversion loss of the mixer according to the present invention is 5.5 dB or less, a band of 4.0 GHz to 5.3 GHz, which is 1 GHz or more, is obtained. However, in conventional microwave circuits with a suspended substrate stripline structure, it is not possible to use surface conductors with a wide range of characteristic impedances, so the mixer's conversion loss
Bandwidth below 5.5dB can only be obtained below 500MHz,
A mixer with good characteristics over a wide band like the embodiment of the present invention cannot be realized. In the figure, _L is the local frequency. As shown in the above embodiments, the microwave circuit of the suspended substrate stripline structure of the present invention has much better characteristics than conventional ones.

By attaching external parts in this way, it is possible to construct various microwave circuits that effectively utilize the characteristics of the suspended substrate stripline circuit.

As is clear from the above description, application of the present invention enables a microwave circuit with a suspended substrate stripline structure that can be widely applied and has good characteristics.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional suspended substrate stripline structure in which more than 1/3 of the back surface is covered with a ground conductor, and Figures 2 and 3 are
4 is a perspective view of an embodiment of the present invention,
Fig. 5 is a plan view of the front conductor in Fig. 4, Fig. 6 is a plan view of the back conductor in Fig. 4, Fig. 7 is an attenuation characteristic diagram of the low-pass filter used in this example, and Fig. 8 is an actual measurement characteristic diagram of the conversion loss of the mixer of the example. In the figure, 1... ground conductor, 2... dielectric substrate, 3... board surface conductor, 4... board back conductor,
5...Through hole, 6...External diode, 7
...It is a strip conductor.

Claims (1)

[Claims for Utility Model Registration] A low-pass filter has a suspended substrate stripline structure using a dielectric substrate composed of a grounded part and an open part whose back side is grounded at least 1/3, and the above-mentioned The low-pass filter includes a capacitive low-impedance line portion formed on the upper surface of the dielectric substrate facing the ground portion, and an inductance low-impedance line portion formed on the upper surface of the dielectric substrate facing the open portion. A microwave board circuit comprising a high impedance line section.