JPS6121880Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a tuner printed with wiring using an insulating substrate, and particularly to a printed board high-frequency circuit device in an amplification or attenuation circuit for UHF band RF signals.

A general amplification element has a terminal or lead that should be grounded at high frequencies, and high frequency amplification is performed by grounding this terminal or lead. However, reliable and complete grounding of such a grounding terminal or lead is extremely difficult depending on the desired lead length and circuit layout, and is known to have an adverse effect on lead inductance and stray capacitance. In particular, UHF
It has been learned from experience that the adverse effect of the lead length from the circuit element to the bypass capacitor when processing band signals greatly deteriorates the circuit characteristics. This is thought to be because the terminal or lead that should be grounded becomes hot at high frequencies, and there is feedback or reverse coupling from the output side to the input side, and this is thought to be caused by stray capacitance. It will be done. For example, FET as an amplification element
When applying an AGC signal and attenuating the gain using
However, the stray capacitance is larger than 0.1PF, which is why the input and output are not separated and sufficient damping characteristics cannot be obtained.

Therefore, the object of the invention is to eliminate the above-mentioned deficiencies, and in particular to provide an improved high frequency circuit for printed wiring circuits for UHF band RF signals.

According to the present invention, there is provided a high frequency circuit in which UHF band amplification or attenuation circuit elements are printed-wired, in which both surfaces of an insulating substrate in a portion corresponding to the wiring position are substantially covered with grounding conductive patterns. . In a specific high-frequency tuner, the UHF band RF signal amplification or attenuation circuit formed by dividing the shield covers at least the entire surface of the insulating substrate on which this circuit element is placed, excluding the insertion hole for the element lead, on both the front and back surfaces of the insulating substrate. It is constructed by forming a conductive pattern and connecting this pattern to a shield partition plate by soldering and grounding. Such a structure reduces the stray capacitance generated between the terminals or leads of the frequency element and the lands for printed wiring on the insulating substrate, provides sufficient attenuation, and presents a high frequency circuit with small kinkback. accordingly
Unnecessary coupling of RF signals is suppressed, and the amplification or attenuation characteristics desired from the design point of view can be obtained. It should be noted that the present invention was discovered when processing RF signals in the UHF band, and does not pose a particularly important problem when dealing with signals in the UHF band or lower frequency bands. for example,
In the VHF band, there is less feedback due to stray capacitance and the absolute value of the amount of feedback is small.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 show a high frequency circuit device according to the present invention, and show an amplification circuit portion of a UHF band RF signal in a tuner. In the figure, a UHF band tuner 1 includes a plurality of shield compartments 2 to 5 formed by upper and lower shield covers 6 and 7 and partition plates 8 to 10. Of these, compartment 3 is UHF band RF
This is a signal amplification circuit, and is formed by printed wiring on an insulating substrate 11 placed across each compartment.

The high frequency amplification circuit device in the compartment 3 is an insulating substrate 11
The circuit elements such as the amplifying element 12 and the coil 13 arranged on the top are connected to the wiring pattern 14 on the back side by solder 15. The feature of the present invention in this circuit configuration is that the surface side, excluding the area around the lead insertion hole 16 of these circuit elements or the area 17 where it is necessary to hold the component insulatively, and the printed wiring pattern 14 and its surrounding area are Conductive patterns 18 and 19 are formed on the other side of the back surface so as to cover almost the entire surface of each conductive pattern, and these patterns 18 and 19 are connected to the solder 2.
0 and 21 to form a ground pattern. In other words, while the other compartments 2 and 4 have circuit elements placed directly on the insulating substrate 11, in the high frequency amplification circuit of the compartment 3, the circuit elements are placed on both sides of the insulating substrate 11 via grounding conductive patterns 18 and 19. Elements 12 and 13 are arranged.

In the above configuration, the high frequency amplifying element 12
The FET's ground terminal is reliably grounded, and the stray capacitance that occurs between its leads or with other conductors is extremely small, thereby preventing unnecessary coupling or feedback between input and output. Therefore, it is possible to obtain satisfactory gain attenuation characteristics in AGC operation. In other words, the part that should originally be grounded is completely grounded in terms of high frequency, and feedback from the output side to the input side or undesired coupling from the input side to the output side is eliminated, providing a high frequency circuit for the UHF band with small kink back. can.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a main part of a high-frequency amplifier circuit according to the present invention, and FIG. 2 is a plan view of the circuit with the circuit elements shown in FIG. 1 removed. 3... Compartment room, 8-10... Partition plate, 11...
Insulating substrate, 12, 13...Circuit element, 18, 19
...Conductive pattern, 20...Solder.

Claims (1)

[Scope of utility model registration request] In a tuner where circuit elements are printed on an insulating board and partitioned into shield sections by arranging partition plates,
A conductive pattern covering almost the entire area is formed on both the front and back surfaces of the insulating substrate at the corresponding position where at least the RF amplification or attenuation circuit element of the UHF band circuit is arranged, and this pattern is applied to the partition plate of the shield section. A high frequency circuit device characterized by being connected and grounded.