JPS63119302A - Strip line filter - Google Patents

Abstract

PURPOSE:To miniaturize a filter and to reduce the cost by putting a dielectric substrate, on which plural electrodes for capacity are formed, from near open ends of respective resonance electrodes to an earth electrode and conductively joining end parts of respective electrodes for capacity and parts near open ends of respective resonance electrodes. CONSTITUTION:One principal surface of a second dielectric substrate 16 is put from parts near open ends of respective resonance electrodes 8 of a dielectric substrate 2 onto a side 62 of an earth electrode 6 facing them, and plural electrodes 18 for capacity which correspond to respective resonance electrodes 8 and are extended from parts near open ends of respective resonance electrodes 8 onto the side 62 of the earth electrodes 6 facing thems are formed on the other principal surface. End parts of electrodes 18 for capacity and parts near open ends of respective resonance electrodes 8 are conductively joined with a conductive cement 14 like a solder or a conductive paste. Thus, the length of the resonance electrode 8 is shortened to miniaturize a filter, and assembling is simplified because one second dielectric substrate 16 is attached to give an overall electrostatic capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a comb-type or interdigital-type stripline filter, and particularly to improvements in miniaturization means thereof.

[Background technology]

A stripline filter has been separately proposed by the same applicant, in which the length of the resonant electrode can be shortened and the filter can be made smaller by installing a capacitor between the open end of the resonant electrode and the ground electrode facing it. ing.

An example of this will be explained with reference to FIG. 3. This is an example of a comb-shaped strip line filter, and a first ground electrode is provided on the entire surface of one main surface (back side of the page) of a rectangular plate-shaped dielectric substrate 2. 4 is formed, and this ground electrode 4 is further extended from the side surface of the dielectric substrate 2 to the periphery of the other main surface (back side of the page) to form a second ground electrode 6. The ground electrode 6 has two opposing sides 61 and 62.
has. Further, on the other main surface of the dielectric substrate 2, there are a plurality of elongated resonant electrodes 8 extending in a comb shape from side 61 to side 62 of the ground electrode 6 and having an open end, and a plurality of elongated resonant electrodes 8 at both ends. Two input/output electrodes 10 each along the resonance electrode 8
is formed.

A chip-type capacitor 1 is connected between the open end of each resonant electrode 8 and the side 62 of the ground electrode 6 facing them.
2 are electrically conductively bonded using a conductive bonding agent 14 such as solder or conductive paste.

In the above filter, the resonant frequency of the resonant electrode 8 can be lowered by the capacitance of the capacitor 12, so the length of the resonant electrode 8 can be shortened and the filter can be made smaller.

[Purpose of the invention]

However, in the above filter, since a plurality of small capacitors 12 must be attached to respective predetermined positions, assembly is time-consuming.

Therefore, the main object of the present invention is to provide a stripline filter that is further improved in this respect.

[Means to achieve the purpose]

In the stripline filter of the present invention, a second dielectric substrate is provided on the other main surface side of the dielectric substrate as described above, from near the open end of each resonant electrode to a second ground electrode opposite thereto. One main surface side is overlapped, and the other main surface of this second dielectric substrate has a second dielectric substrate corresponding to each resonant electrode and facing them from near the open end of each resonant electrode.
A plurality of capacitor electrodes are formed extending over the ground electrode, and the end portion of each capacitor electrode and the vicinity of the open end of each resonance electrode are electrically connected to each other.

[Effect]

A capacitance is generated between each capacitance electrode and the second ground electrode thereunder, and this capacitance is inserted between the vicinity of the open end of each resonant electrode and the second ground electrode. Therefore, as in the case of the previous example, the length of the resonant electrode can be shortened to reduce the size of the filter. Moreover, 1
Assembly is simple because all the capacitance can be provided by attaching two second dielectric substrates.

〔Example〕

FIG. 1 is a plan view showing a comb-shaped stripline filter according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line nn in FIG. 1. Components that are the same or equivalent to those in FIG. 3 are given the same reference numerals, and their explanations will be omitted.

In this embodiment, on the other main surface side (front side of the paper) of the dielectric substrate 2 as described above, from near the open end of each resonant electrode 8 to on the side 62 of the ground electrode 6 facing them, One main surface side of the two dielectric substrates 16 is overlapped. On the other main surface (the front side of the paper) of the dielectric substrate 16, there are a plurality of holes corresponding to the respective resonant electrodes 8 and extending from the vicinity of the open end of each resonant electrode 8 to the side 62 of the ground electrode 6 facing them. A capacitor electrode 18 is formed. Then, the end portion of each capacitor electrode 18 and the vicinity of the open end of each resonant electrode 8 are conductively bonded using a conductive bonding agent 14 such as solder or conductive paste.

In that case, a gap 20 (see FIG. 2) existing between the tip of the resonant electrode 8 and the side 62 of the ground electrode 6 may be provided as necessary.
For example, the dielectric substrates 2 and 16 may be bonded together using a glaze or the like, and in this way, the dielectric substrates 16 can be temporarily attached or attached without adversely affecting the electrical characteristics. Can be reinforced.

In the above filter, capacitance is generated between each capacitance electrode 18 and the side 62 of the ground electrode 6 located below it, and this is generated near the open end of each resonance electrode 8 and the side 62 of the ground electrode 6 located below.
The shape is inserted between 2 and 2. Therefore, as in the case of the previous example, the length of the resonant electrode 8 can be shortened to reduce the size of the filter. The size of the capacitance can be determined by appropriately selecting the opposing area between the side 62 of the ground electrode 6 and the capacitor electrode 18, the dielectric constant and thickness of the dielectric substrate 16, etc., to determine the desired frequency, etc. It can be made according to the

Moreover, unlike the case of the previous example, only one dielectric substrate 16 is used.
Since all the resonant electrodes 8 can be provided with capacitance at the same time by attaching them, assembly is easy and mass production is good, and therefore costs can be further reduced.

In addition, by doing the above, there is less variation between the capacitances inserted into each resonant electrode ε (therefore, the electrical characteristics of the filter are also improved. For example, the spurious mode of the triple harmonic is uniformly reduced). can be shifted to higher frequencies.

Although the above description has been made using a comb-shaped stripline filter as an example, it goes without saying that the present invention can also be applied to an interdigital stripline filter.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to reduce the size of the filter by shortening the length of the resonant electrode, and it is also easy to assemble, good for mass production, and further reduce costs. Further, electrical characteristics such as spurious characteristics are further improved.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a comb-shaped stripline filter according to an embodiment of the present invention. FIG. 2 is a sectional view taken along line nn in FIG. 1. FIG. 3 is a plan view showing an example of a comb-shaped stripline filter, which is the background of the present invention. 2... Dielectric substrate, 4.6... Earth electrode, 61.
62... Side, 8... Resonant electrode, 16... Second dielectric substrate, 18... Capacitor electrode.

Claims (1)

[Claims] (1) A first ground electrode is formed on one main surface of the dielectric substrate, and a second ground electrode having two opposing sides is formed on the other main surface.
and a plurality of resonant electrodes extending from at least one of the two sides toward the other and having an open end, the stripline filter having a ground electrode on the other main surface side of the dielectric substrate. One main surface side of the second dielectric substrate is overlapped from the vicinity of the open end of each resonant electrode to the second ground electrode facing them, and this second
A plurality of capacitor electrodes are formed on the other main surface of the dielectric substrate, and correspond to each resonant electrode and extend from near the open end of each resonant electrode to a second ground electrode facing them, and a strip line filter characterized in that the ends of each capacitance electrode and the vicinity of the open end of each resonance electrode are electrically connected to each other.