JP2000101304A - Bandpass filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bandpass filter that can be configured on a plurality of stages and miniaturized further. SOLUTION: This bandpass filter is provided with a dielectric board 10, at least one conductor line 14 that is formed on one side of the dielectric board 10 and extended in directions of edges opposed to each other, an inner ground conductor that is formed on one side of the dielectric board 10 and in existence on both sides in the directions of the extension of the conductor line 14, slot lines 11, 12 that are specified by the conductor line 14 and the inner ground conductor, formed on one side of the dielectric board 10 and extended in parallel, and 1st and 2nd existing means that excite slot propagation mode to the slot lines 11, 12. The bandpass filter has a resonance point by each slot propagation mode generated in the slot lines 11, 12 and a coplanar propagation mode generated in the conductor line 14 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band-pass filter using a planar waveguide used for a high-frequency circuit in radio communication equipment such as mobile communication equipment and radar equipment.

[0002]

2. Description of the Related Art In recent years, with the spread of mobile communication devices,
There is an increasing demand for miniaturization of microwave components. Coplanar waveguides have attracted attention as waveguides constituting these microwave components, and are expected to be applied to bandpass filters using coplanar resonators.

[0003] As is well known, a coplanar resonator forms a plurality of slots in a conductor film on a dielectric substrate in parallel with each other, and connects one conductor film separated by these slots to one.
Shorting means is provided so as to short-circuit at / 4 wavelength intervals, and a coplanar propagation mode is excited and resonated on a conductor line formed between a plurality of slots.

[0004]

However, a band-pass filter using such a coplanar resonator is
Since only the resonance in the coplanar propagation mode propagating on the conductor line formed between the slots is used, at least three slots are required to form a two-stage bandpass filter. , It is necessary to form at least four slots on the conductor film. As described above, forming a large number of slots on the substrate is very disadvantageous for miniaturizing the bandpass filter. In particular, in mobile communications in the future, each mobile terminal is required to cover two use frequency bands, and thus miniaturization of a dual-band bandpass filter has become essential.

Accordingly, an object of the present invention is to provide a bandpass filter having a plurality of stages which can be further reduced in size.

[0006]

According to the present invention, there is provided a dielectric substrate, at least one conductor line formed on one surface of the dielectric substrate and extending in the direction of opposite edges, and a dielectric substrate. An internal ground conductor formed on the surface of the body substrate and present on both sides in the extending direction of the conductor line, and extending parallel to each other and defined by the conductor line and the internal ground conductor and formed on the surface of the dielectric substrate First and second slot lines, and first and second exciting means for exciting a slot propagation mode in the first and second slot lines. The present invention provides a bandpass filter having a resonance point in each of a slot propagation mode generated in the above and a coplanar propagation mode generated in a conductor line.

In this case, it is preferable to further include an external ground conductor formed on all other surfaces of the dielectric substrate.

Further, according to the present invention, there are provided two dielectric substrates fixed to each other in close contact with each other, and at least one conductor line formed on the contact surfaces of the dielectric substrates and extending in the direction of the edges facing each other. First and second parallel ground conductors defined by an external ground conductor formed on all surfaces of the two dielectric substrates, a conductor line and an external ground conductor, and extending in parallel with each other and formed on the contact surfaces of the dielectric substrates. , And first and second exciting means for exciting the slot propagation mode in the first and second slot lines most in a plane perpendicular to the direction in which the conductor line extends. And a band-pass filter having a resonance point in each of a slot propagation mode generated in the second slot line and a coplanar propagation mode generated in the conductor line.

Further, according to the present invention, a dielectric substrate, at least one conductor line formed on one surface of the dielectric substrate and extending in the direction of the edge facing each other, A first external ground conductor formed on all surfaces of the dielectric substrate, a second external ground conductor connected to the first external ground conductor and covering one surface of the dielectric substrate via a gap, and a conductor line First and second slot lines defined by the first and second external ground conductors and extending parallel to each other and formed on the surface of the dielectric substrate; and slots in the first and second slot lines. A first and a second pumping means for pumping a propagation mode, having a resonance point in each of a slot propagation mode generated in the first and second slot lines and a coplanar propagation mode generated in a conductor line. Van Pass filter is provided.

[0010] The first and second slot lines are excited so as not to provide a short-circuit path for short-circuiting the internal ground conductors separated by the slot line at quarter-wave intervals. Three resonance points are obtained by intentionally generating the first and second slot lines and by using these slot propagation modes and the coplanar propagation modes generated in the conductor lines. That is, it is possible to configure a three-stage bandpass filter only by providing two slots on the substrate. As a result, it is possible to further reduce the size and weight of the multi-stage bandpass filter.

It is preferable that each of the first and second excitation means is a feed line connected to the above-described conductor line via an air bridge.

[0012]

FIG. 1 is a perspective view schematically showing a configuration of a bandpass filter according to an embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes a dielectric substrate, and reference numeral 11 denotes a conductive film formed over substantially the entire surface 10a of the dielectric substrate 10. Conductive film 11
Are not formed in portions of the surface 10a which extend in the direction of the opposite edges and extend in parallel with each other, and these portions constitute the first and second slot lines 12 and 13. In addition, the first and second conductive films 11
The portion sandwiched between the slot lines 12 and 13 constitutes one conductor line 14. Further, other portions of the conductive film 11 constitute an internal ground conductor. Conductor line 14
Are connected to the internal ground conductor, and therefore, this bandpass filter is formed of a resonator having both ends grounded.

Feed lines 15 and 16 are formed at a predetermined distance from the short-circuited end of the resonator. The feed lines 15 and 16 and the conductor line 14 are connected to the air bridge 1.
7 and 18 respectively. As a result, a signal from an external circuit provided via the feed line 15 and the air bridge 17 causes the first slot line 1
2, the resonance of the slot propagation mode is excited.

The resonance in the slot propagation mode propagating in the first slot line 12 excites the coplanar propagation mode propagating on the adjacent conductor line 14, and further excites the coplanar propagation mode propagating on the conductor line 14. The resonance excites the resonance of the slot propagation mode propagating in the adjacent second slot line 13. The resonance in the slot propagation mode propagating through the second slot line 13 excites a signal in the air bridge 18 and the feed line 16, which is output to an external circuit. In FIG. 1, reference numeral 19 denotes an external ground conductor formed on all surfaces except the surface 10a of the dielectric substrate 10. The external ground conductor 19 is not essential in theory, but is required for shielding as an actual bandpass filter.

As described above, in the present embodiment, three resonances, one resonance in the coplanar propagation mode and two resonances in the slot propagation mode, are generated to form a three-stage bandpass filter. The resonance frequency in the coplanar propagation mode is determined by appropriately selecting the dielectric constant and thickness of the dielectric substrate 10, the length and width of the conductor line 14, and the widths of the first and second slot lines 12 and 13. Can be set. The resonance frequency in the slot propagation mode depends on the dielectric constant and thickness of the dielectric substrate 10,
And the lengths of the first and second slot lines 12 and 13 and the widths of the first and second slot lines 12 and 13 can be set as appropriate.

By way of example only, the relative permittivity of the dielectric substrate 10 is ε _r = 10.5, and the thickness is h = 0.3-6.0 m.
m, the conductor line 14 and the first and second slot lines 1
The length of 2 and 13 is L = 16 mm, the width of the conductor line 14 is W = 0.1-2.4 mm, and the width of the first and second slot lines 12 and 13 is S = 0.2-1.2 mm. When the feeder lines 15 and 16 are provided at a position 0.8 mm from the short-circuited end of the resonator and the height of the air bridges 17 and 18 is set to 0.2 mm, resonance occurs in both the coplanar propagation mode and the slot propagation mode. Bandpass characteristics are obtained.

By providing two slots, three resonances including different propagation modes can be excited, so that a more compact three-stage bandpass filter can be provided.

FIG. 2 is a perspective view schematically showing the configuration of another embodiment of the bandpass filter of the present invention. FIG. 3 is an exploded perspective view showing the internal configuration of the embodiment of FIG. FIG. 3 is a sectional view taken along line AA of FIG. 2.

In these figures, reference numeral 20 denotes a dielectric block in which two dielectric substrates 20a and 20b are fixed in close contact with each other, and reference numeral 24 denotes a direction in which the contact surfaces 21 of both dielectric substrates 20a and 20b face each other. One extending conductor line 29 indicates an external ground conductor formed on all surfaces of the dielectric block 20. On both sides of the conductor line 24 on the contact surface 21, first and second slot lines 22 and 23 which are sandwiched between the conductor line 24 and the external ground conductor 29 and extend in parallel with the conductor line 24 are formed. ing. Both ends of the conductor line 24 are connected to the external ground conductor 29. Therefore, this bandpass filter is formed of a resonator of both ends grounded.

Feed lines 25 and 26 are formed at a predetermined distance from the short-circuited end of the resonator. The feed lines 25 and 26 and the conductor line 24 are connected to the air bridge 2.
7 and 28, respectively.

A signal from an external circuit provided through the power supply line 25 and the air bridge 27 excites the slot propagation mode resonance in the first slot line 22.
The resonance of the slot propagation mode propagating in the first slot line 22 excites the coplanar propagation mode propagating on the adjacent conductor line 24,
The resonance of the coplanar propagation mode propagating above excites the resonance of the slot propagation mode propagating in the adjacent second slot line 23. The resonance in the slot propagation mode propagating in the second slot line 23 excites a signal in the air bridge 28 and the feed line 26, and this is output to an external circuit.

As described above, also in the present embodiment, three resonances, one resonance in the coplanar propagation mode and two resonances in the slot propagation mode, are generated to form a three-stage bandpass filter. As in the case of the embodiment of FIG. 1, the resonance frequency in the coplanar propagation mode depends on the dielectric constant and thickness of the dielectric substrates 20a and 20b,
It can be set by appropriately selecting the length and width of the conductor line 24, and the widths of the first and second slot lines 22 and 23. As in the case of the embodiment of FIG. 1, the resonance frequency in the slot propagation mode depends on the permittivity and thickness of the dielectric substrates 20a and 20b, the lengths of the first and second slot lines 22 and 23, and First and second
Can be set by appropriately selecting the widths of the slot lines 22 and 23.

FIG. 5 is a perspective view schematically showing a configuration of still another embodiment of the bandpass filter of the present invention, and FIG. 6 is a sectional view taken along line BB of FIG.

In these figures, 50 is a dielectric substrate,
Reference numeral 51 denotes a conductor case that covers one surface 50a of the dielectric substrate 50, and 59 denotes an external ground conductor formed on the other surface of the dielectric substrate 50. Although not all shown, on the surface 50a of the dielectric substrate 50, as in the case of the embodiment of FIG. 2, one conductor line 54, first and second slot lines, a feed line and An air bridge is formed.

That is, in the present embodiment, while the embodiment of FIG. 2 tightly fixes two dielectric substrates,
It is configured such that a conductor case 51 is put on one dielectric substrate 50. Therefore, as shown in the cross-sectional view of FIG. 6, in the present embodiment, the lower portion of the filter is made of a dielectric material, and the upper portion is made of air. Other configurations and operations are exactly the same as those in the embodiment of FIG.

The embodiments described above all illustrate the present invention by way of example and not by way of limitation, and the present invention can be embodied in various other modified and modified forms. Therefore, the scope of the present invention is defined only by the appended claims and their equivalents.

[0028]

As described in detail above, according to the present invention, the first and second internal ground conductors separated by the slot line are not provided with a short-circuit path for short-circuiting them at quarter-wave intervals. By exciting the second slot line, a slot propagation mode is intentionally generated in the first and second slot lines, and the three resonance points are generated by the slot propagation mode and the coplanar propagation mode generated in the conductor line. Have gained. That is, it is possible to configure a three-stage bandpass filter only by providing two slots on the substrate. As a result, it is possible to further reduce the size and weight of the multi-stage bandpass filter.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a configuration of a bandpass filter according to an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing a configuration of another embodiment of the bandpass filter of the present invention.

FIG. 3 is an exploded perspective view showing an internal configuration in the embodiment of FIG.

FIG. 4 is a sectional view taken along line AA of FIG. 2;

FIG. 5 is a perspective view schematically showing a configuration of still another embodiment of the bandpass filter of the present invention.

FIG. 6 is a sectional view taken along line BB of FIG. 5;

[Explanation of symbols]

 10, 20a, 20b, 50 Dielectric substrate 10a One surface 11 Conductive film 12, 13, 22, 23 Slot line 14, 24, 54 Conductive line 15, 16, 25, 26 Feed line 17, 18, 27, 28 Air Bridge 19, 29, 59 External ground conductor 21 Close contact surface 51 Conductor case

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J006 HB02 HB12 HC03 JA01 LA21 NA02 NA08 NB05 PA01 PA03

Claims (5)

[Claims] 1. A dielectric substrate, at least one conductor line formed on one surface of the dielectric substrate and extending in a direction of edges facing each other, and formed on the surface of the dielectric substrate. And an internal ground conductor present on both sides in the direction of extension of the conductor line, and a second conductor defined by the conductor line and the internal ground conductor and extending in parallel with each other and formed on the surface of the dielectric substrate. A first and a second slot line, and a first and a second pumping means for exciting a slot propagation mode in the first and the second slot line. A band-pass filter having a resonance point in each of a slot propagation mode generated in the conductor line and a coplanar propagation mode generated in the conductor line. 2. The bandpass filter according to claim 1, further comprising an external ground conductor formed on all other surfaces of said dielectric substrate. 3. Two dielectric substrates which are fixed to each other in close contact with each other, at least one conductor line formed on a contact surface of said dielectric substrate and extending in a direction of an edge facing each other, External ground conductors formed on all surfaces of the dielectric substrate, first and second parallel conductors defined by the conductor line and the external ground conductor and extending in parallel with each other and formed on the contact surface of the dielectric substrate; Two slot lines,
A first and a second excitation means for exciting a slot propagation mode in the first and second slot lines in a plane perpendicular to the direction in which the conductor line extends,
A band-pass filter having a resonance point in each of a slot propagation mode generated in the first and second slot lines and a coplanar propagation mode generated in the conductor line. 4. A dielectric substrate, at least one conductor line formed on one surface of the dielectric substrate, and extending in a direction of edges facing each other, and all other surfaces of the dielectric substrate. A first external ground conductor formed on the first external ground conductor, a second external ground conductor connected to the first external ground conductor and covering the one surface of the dielectric substrate with a gap therebetween, and the conductor line First and second slot lines defined by the first and second external ground conductors and formed on the surface of the dielectric substrate and extending in parallel with each other;
And first and second excitation means for exciting a slot propagation mode in the second slot line, and a slot propagation mode generated in the first and second slot lines and a first mode in the conductor line. A band-pass filter having a resonance point for each of the coplanar propagation modes. 5. Each of said first and second excitation means comprises:
5. A power supply line connected to the conductor line via an air bridge.
The bandpass filter according to the paragraph.