JP2780166B2 - Stripline filter bandwidth adjustment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the bandwidth of a stripline filter usable in a high-frequency band exceeding 100 MHz, and more particularly to a stripline having a conductor pattern of one or more turns formed on the surface of a dielectric substrate. The present invention relates to a bandwidth adjustment method that can be performed even after a filter is assembled.

[0002]

2. Description of the Related Art There is an increasing demand for resonators and filters that can be used in a band of several hundred MHz, such as mobile communication devices. Conventionally, helical resonators (filters), dielectric resonators (filters), and the like have been used. However, the size is limited by the wavelength of the resonance frequency, and thus there is a limit to miniaturization. Adjustment is often required due to the problem of dimensional accuracy during firing. In addition, there are demands for resonators and filters that require a large number of man-hours in an assembling process and the like, and that are accurate and easy to manufacture.

[0003] Further, in the helical filter and the dielectric filter, there is a problem that a harmonic that is three times the fundamental frequency is generated, and a major problem is how to remove the harmonic.

The inventor of the present application has disclosed in Japanese Patent Application No. 3-183290 that a plurality of orbiting conductor patterns for inductors are provided on at least one surface of a dielectric substrate, and the conductor patterns are arranged close to each other. One end of the conductor pattern is connected to an input / output end, and the other end is proposed as a strip line filter grounded.

FIGS. 3A and 3B are plan views of the strip line filter, in which FIG. 3A shows the upper surface and FIG. 3B shows the lower surface. Conductor striplines 11 and 12 are formed on the front and back surfaces of a ceramic substrate 10 having a dielectric constant of about 20. The strip lines 11 and 12 of the conductor are connected by through holes 17 formed in the substrate 10 to form one continuous strip line.

The conductor strip line 11 is formed as a conductor pattern that circulates about one and a half turns on the front side. Conductor strip line 12 on the back side connected by through hole 17
Is also formed as a conductor pattern that makes a slight turn around two turns, and the end is drawn out to the side surface of the substrate. The front and back conductor patterns are formed so as to overlap on the front and back surfaces and face each other.
Since the conductor patterns are formed to extend in the same direction, it is impossible for all the conductor patterns to overlap and face each other, but most of them can be overlapped. This is for providing capacitance between the conductor patterns. Of course, it is desirable that the conductor patterns are arranged close to each other so that a capacitance can be obtained between the conductor patterns on the same surface.

The ends of the conductor strip lines 11 and 13 face the conductor films 15 and 16 to obtain input / output coupling capacitance. As shown in FIG. 4, the dielectric substrate 10 is bonded and laminated so as to be sandwiched between two thick dielectric substrates 20a and 20b. Then, the conductor films 15, 16 for obtaining the input / output coupling capacitance are connected to the input / output terminal electrodes 18, 19. The input / output terminal electrodes 18 and 19 are formed so as to straddle the surfaces of the two dielectric substrates with the side surfaces of the laminate of the three dielectrics as the center. Thereby, it can be directly mounted and connected on the printed wiring board. Also,
It is desirable to form a ground electrode 21 on the surface and side surfaces other than the input / output terminal electrodes 18 and 19 and shield them.

[0008]

There is a pass band width as one of the characteristics of the filter, and it may be necessary to adjust the band to a constant band with respect to the center frequency. However, it could not be adjusted after forming the terminal electrode and the ground electrode.

The present invention provides a method for adjusting the pass bandwidth even after assembling a filter and forming electrodes.

[0010]

The present invention solves the above-mentioned problems by adjusting the distance between the input / output terminal electrode and the ground electrode.

That is, conductor patterns for inductors which are connected to the front and back surfaces of the dielectric substrate by through holes and are bent at a right angle and circulate in the same direction are arranged at intervals, and each of the conductor patterns is removed except for the vicinity of the bent portion. The other end of the conductor pattern facing the other side of the inductor is grounded, and the other end of the conductor pattern for the inductor located at both ends of the dielectric substrate is grounded. The end on the side not facing the conductor pattern is connected to the input / output terminal via a capacitor, and an LC parallel resonance circuit is constituted by the inductance of each conductor pattern and the line capacitance of the conductor pattern. Are sandwiched between two dielectric substrates and integrated, and the surfaces of those two dielectric substrates and three dielectric In a method of adjusting the bandwidth of a strip line filter in which input / output terminals are formed to extend over end faces of a laminate of plates, other than the end faces on which input / output terminal electrodes of the laminate of three dielectric substrates are formed. A ground electrode insulated from the input / output terminal electrode is formed on the end face and the surface of the two dielectric substrates, and by removing the conductor film facing the input / output terminal electrode of the ground electrode, the input / output terminal electrode It is characterized in that the bandwidth is adjusted by adjusting the distance from the ground electrode.

[0012]

Although the principle of the present invention has not been fully elucidated, the bandwidth is changed by adjusting the distance (distance) between the input / output terminal electrode and the ground electrode, and the bandwidth is reduced by increasing the distance. It was confirmed that.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention. Dielectric substrate sandwiched between two dielectric substrates 20a and 20b
The strip line electrode and the input / output coupling electrode as described above are formed on the reference numeral 10, and are connected to the input / output terminal electrodes 18 and 19. The input / output terminal electrodes are the dielectric substrates 20a, 20b
The dielectric substrate 10 is formed so as to extend on the surfaces of the dielectric substrates 20a and 20b with the side surfaces of the laminate of the three dielectric substrates as the center.

A ground electrode 21 is formed on the other side surface of the dielectric substrate laminate and on the surfaces of the dielectric substrates 20a and 20b.
The ground electrode 21 is insulated from the input / output terminal electrodes 18 and 19 and formed so as to straddle between the input / output terminal electrodes 18 and 19 to prevent signal leakage between the input / output terminal electrodes 18 and 19. May be.

In this example, the dielectric substrate is 5.0 m long.
m, 5.7mm wide and dielectric constant of 20
0.2 mm, and the thickness of the two sheets on both sides was 1.2 mm. The size of the exposed portion of the dielectric on the surface of the dielectric substrates 20a and 20b, that is, the portion where no electrode is formed, is 0.7 mm x 2.4 mm, and the distance (distance) d between the tip of the input / output terminal electrode and the ground electrode is changed. The change in bandwidth was measured.

That is, the conductor film 22 at the end of the ground electrode 21 on the input / output terminal electrode side was removed to gradually increase the interval, and the frequency bandwidth at that time was measured. FIG. 2 shows the result of the measurement, and is an example in which the measurement was initially expanded from 0.2 mm to 0.5 mm and 1.0 mm. Filter with center frequency 883MHz, d
Is 0.25 mm, the bandwidth (Bw) is 35.6 MHz and the center frequency ratio is 4.03%. However, when the bandwidth is 0.5 mm and 1.0 mm, the bandwidth (Bw) is 34.0 MHz and 31.6 MHz, respectively.
%, And the result gradually narrowed.

[0018]

According to the present invention, it is possible to adjust the frequency pass bandwidth of the stripline filter to a desired characteristic.

Further, the adjustment can be performed after the assembly and the formation of the electrodes, so that the number of steps can be reduced and the yield can be greatly improved in terms of manufacturing.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a change in characteristics.

FIG. 3 is a plan view of a main part of a strip line filter to which the present invention is applied.

FIG. 4 is a perspective view when a strip line filter to which the present invention is applied is assembled.

[Explanation of symbols]

 18, 19: I / O terminal electrode 20: Dielectric substrate 21: Ground electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01P 1/20-1/219 H01P 7/00-7/10 H03H 7/00-7/13

Claims (1)

(57) [Claims] 1. An inductor connected to the front and back surfaces of a dielectric substrate by through holes, bent at a right angle, and circling in the same direction.
Are arranged at intervals.
Conductor pattern is on the front and back, except near the bend
Conductors for those inductors that are arranged to overlap
The side of the pattern facing the other conductor pattern for inductor
Is grounded, and the inductors located at both ends of the dielectric substrate
And other inductor conductor patterns.
The opposite end is connected to the I / O terminal via a capacitor.
The inductance of each conductor pattern and its
The LC parallel resonance circuit is configured by the line capacitance of the body pattern.
Form, the dielectric substrate are integrated pinched on two sheets of dielectric substrate, extending over input and output end faces of the stack of those two surfaces of the dielectric substrate and three sheets of the dielectric substrate In the method of adjusting the bandwidth of the stripline filter in which the terminals are formed, on the other end surface and the surface of the two dielectric substrates except for the end surface on which the input / output terminal electrodes of the laminate of the three dielectric substrates are formed, A ground electrode insulated from the input / output terminal electrode is formed, and by removing the conductive film facing the input / output terminal electrode of the ground electrode, the distance between the input / output terminal electrode and the ground electrode is adjusted to increase the bandwidth. A method for adjusting the bandwidth of a stripline filter, the method comprising adjusting.