JPH03253105A - Filter resonator - Google Patents

Abstract

PURPOSE:To obtain an easily adjustable resonator for a column line BPF by arranging a ground rod to be vertically moved through the cylindrical inside of a cylindrical resonance rod vertically fixed on the lower plate of a case. CONSTITUTION:The resonance rod 8 is cylindrically formed and its lower end part is fixed on the lower plate 10 of the case by a screw 11. On the other hand, the leading part of the rod 8 is supported by a cylindrical bushing 6 formed by an insulating material and a flange 3 fixed on the upper end face of the bushing 6 is fixed on an upper plate 9 by a screw 1. The ground rod 5 having a function capable of changing or finely adjusting tuning frequency is screwed into the rod 8 from the upper part of the rod 8 and the bottom metal of a cylindrical bushing 7 formed by an insulating substance to prevent the lower end part of the rod 5 from being inclined and having an outer diameter is slightly smaller than the inner diameter of the cylinder of the rod 8 is fixed to the lower end of the rod 5. Thus, stable characteristics can be obtained also from a signal with large power and the resonator can easily respond to a frequency changing request.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a resonator of a comline bandpass filter (BPF) used in a VHF or UHF band wireless communication device.

(Prior Art and Its Disadvantages) FIG. 2 is a side view showing a resonator portion of a conventional combline BPF. In the figure, 103 and 105 are the upper and lower plates of the case for arranging and fixing a plurality of resonators in parallel. The tuning frequency of this resonator is determined by the case lower plate 105.
A tuning screw 101 is provided with a space gap g at the tip of a resonance rod 104 fixed by a screw 106 to
The size of the space gap g is changed by turning the , moving it up and down as shown by the arrow, and the capacitance value due to this gap g is determined.

The length l and the tuning frequency f of the resonant rod 104. The relationship between is determined by the following formula.

However, v: 3xloll (mm/5ee) Zo
: Characteristic impedance of the resonator (Ω) △C: Capacitance of the tip gap of the resonant rod (pF) This relationship shows that the tuning frequency can be further lowered by adding . However, such a conventional structure has the following problems, which are obstacles to practical use.

(2) When ΔC is increased, the gap g becomes smaller and the withstand voltage decreases, so that it cannot be used in devices that apply large amounts of power.

■ Temperature characteristics are poor because the tuning frequency changes greatly due to a slight change in gap g. To improve temperature characteristics, a special and expensive material with a small coefficient of linear expansion, such as invar, a type of nickel steel, is used. It was necessary to make the resonant rod 104 by using the following method.

■ Since the resonant rod 104 is fixed to the case lower plate 105 at one point, it has poor vibration resistance, so it could only be used in radio equipment mounted on aircraft.

■ In order to obtain the desired filter characteristics, it is necessary to finely adjust the distance between the adjacent resonant rods arranged in parallel.
The solution was to make the hole where it is fixed into an elongated hole so that it can be moved left and right as shown by the arrow. However, with this structure, when the resonant rod 104 is moved from side to side, the opposing area between the tip of the resonant rod 104 and the gap g between the screw 101 changes, which changes the tuning frequency significantly, making adjustment difficult and reducing production efficiency. It wasn't from above.

(Object of the Invention) The object of the present invention is to solve the above-mentioned conventional problems and provide a resonator for a column line BPF that is resistant to vibration, has good temperature characteristics, can be used with high power, and is easy to adjust. It's about doing.

(Structure and operation of the invention) A wave resonator according to the present invention includes a case having an upper plate and a lower plate arranged at a predetermined interval, and a case having a length shorter than the interval and fixed perpendicularly to the lower plate of the case. A cylindrical resonance rod with an open bottom and an upper end portion of the resonance rod formed into a cylindrical shape with an insulating material, passing through a hole provided in the upper plate of the case, and a stepped portion provided at the lower end portion. a first bushing that is slightly smaller than the inner diameter of the resonator rod and is disposed to fit into the upper end portion of the resonant rod; a flange fixed to the flange and having a tapped hole in the center; a grounding rod that is screwed into the tapped hole of the flange and is movable up and down while loosely passing through the central axis inside the cylinder of the first bushing and the resonance rod; The ground rod is fixed to the lower end of the ground rod, and is molded from an insulating material and has an outer periphery in contact with the inner wall surface of the resonant rod in order to maintain a predetermined distance between the outer circumferential surface of the ground rod and the inner wall surface of the resonant rod. and a lock nut that locks the ground rod by being screwed onto the ground rod and tightened to the flange when the ground rod is moved up and down and reaches a predetermined position. It is characterized by this.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 (AXB) is a plan view and a partially sectional front view showing an embodiment of a resonator according to the present invention.

In the figure, the resonance rod 8 has a cylindrical shape, and its lower end is fixed to the case lower plate 10 by a screw 11.

On the other hand, the tip of the resonance rod 8 is supported by a cylindrical bushing 6. That is, the outer diameter of the stepped portion provided at the lower end of the bushing 6 is slightly smaller than the inner diameter of the resonant rod 8, and is fitted into the resonant rod 8 to support the upper end of the resonant rod 8.

A flange 3 is fixed to the upper end surface of this bushing 6 with countersunk screws 2, and the protruding portion of the flange 3 is screwed into
It is fixed to the upper plate 9 by.

The grounding rod 5, which has the function of changing or finely tuning the tuning frequency, has a thread cut on its outer periphery, and a groove is cut on its upper end protruding from the upper surface of the case to facilitate rotation. The lower end of the grounding rod 5, which is screwed and inserted into the resonant rod 8 from above, has a concave cross section made of an insulating material such as Teflon so that the lower end does not slope, and the outer diameter is smaller than the cylindrical inner diameter of the resonant rod 8. The bottom of a slightly smaller cylindrical bushing 7 with a bottom is attached with a screw.

The hole into which the screw 1 for fixing the flange 3 to the case top plate 9 is inserted is an elongated hole, so that it can be moved left and right together with the resonance rod 8 when finely adjusting the coupling by changing the distance between adjacent resonators. It has become. Therefore, the hole in the case top plate 9 into which the bushing 6 is inserted is an elongated hole that is larger than the outer circumference of the flange 6.

The procedure for assembling the resonator is as follows: 7. After attaching the resonance rod 8 to the case lower plate 10. 6. 3. 4. Insert the parts assembled in order 5 from the top of the case and fix with screws 1. Therefore, if the frequency of the filter is changed, the resonant rod 8 remains fixed to the lower plate 10 of the case, and 7.
6. 3. 4. It has the feature that it can be handled by simply removing the assembly part of 5 and replacing it with a grounding rod 5 of a different length.

In addition, the resonance rod 8. Since the ground rods 5 are fixed at both ends, the structure is strong against vibration.

Furthermore, the resonance rod 8. Since the edge of the end face of the grounding rod 5 is covered with the insulating bushing 7.6, it has high withstand voltage and can apply a large amount of power.

Capacitance △C of the tip gap of the resonant rod in the conventional structure
1. That is, in the case of the present invention, the resonator tip load capacity is the capacitance due to the gap between the inner surface of the resonant rod 8 and the outer surface of the ground rod 5, and because of the cylinder trimmer structure, the part forming ΔC, Resonant rod8. Ground rod5. By appropriately selecting the material of the case, a filter resonator with good temperature characteristics can be constructed.

Fig. 3 is a side view of the transmission characteristics of a six-stage BPF using six resonators of the present invention, and Fig. 4 is a side view of the transmission characteristics of a six-stage BPF using six resonators of the present invention. FIG. 3 is a side view of temperature characteristics of a filter using a resonator.

In these characteristic diagrams, the horizontal axis indicates frequency and the vertical axis indicates response. Pass band width is 100MH indicated by Δ mark
z ~150 MHz, the characteristic S 2+ indicates the transmission characteristic, and SI+ indicates the reflection characteristic. Transmission characteristics S 21 no 0
, 1 dB/div are enlarged changes in the pass band, and the example in FIG. 4 shows how excellent the temperature characteristics are.

This example operated without any problem even with a signal power of 3KW.

(Effects of the Invention) As described above in detail, the following effects can be achieved by implementing the present invention.

■ Stable characteristics can be achieved even for high power signals.

■ Easily respond to requests for frequency changes.

■ Good temperature characteristics can be maintained without using expensive materials.

■ Has vibration resistance that can be used in aircraft-mounted radio equipment.

[Brief explanation of drawings]

FIG. 1 is a plan view and a partial vertical sectional view showing an embodiment of the present invention,
FIG. 2 is a side view showing an example of a conventional structure, and FIGS. 3 and 4 are side views showing characteristics of a BPF to which the present invention is applied. 1, 2.11...screw, 3...flange, 4...
・Earth rod locking nut, 5...Earth rod, 6, 7...
・Bushing, 8...Resonance rod, 9...Case top plate,
lO... Case lower plate, 101... Tuning screw 102... Tuning screw lock nut, 103
...Case top plate, 104...Resonance bar, 105...
Case lower plate, 106...Screw. Agent: Patent attorney Otsuka, 1 person from outside the university, Figure 2, Figure 3, MyL Akira

Claims (1)

[Scope of Claims] A case having an upper plate and a lower plate arranged at a predetermined interval; an open-bottomed cylindrical resonant rod fixed perpendicularly to the lower plate of the case and having a length shorter than the interval; The upper end of the resonant rod is formed into a cylindrical shape from a material and passes through a hole provided in the upper plate of the case, and the outer diameter of the stepped portion provided at the lower end portion is slightly smaller than the inner diameter of the upper end portion of the resonant rod. a flange fixed to the upper end surface of the first bushing, a peripheral portion of which is fixed to the upper surface of the peripheral edge of the hole in the upper plate, and a flange having a tapped hole in the center; a grounding rod that is screwed into the tapped hole of the flange and is movable up and down by passing loosely through the first bushing and the center axis inside the cylinder of the resonance rod; a second bushing molded from an insulating material and having an outer periphery in contact with the inner wall surface of the resonant rod in order to maintain a predetermined distance between the outer circumferential surface of the ground rod and the inner wall surface of the resonant rod; A resonator for a filter, comprising a lock nut that locks the ground rod by being screwed onto the ground rod and tightened to the flange when the ground rod is moved up and down and reaches a predetermined position.