JPH09275329A - High speed tuning filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high speed tuning filter with a small occupied volume and ease of coupling in the case of multi-stage connection in which the structure of an outer conductor of the high speed tuning filter for frequency hopping communication is simplified so as to select an optional variable inductance. SOLUTION: A variable tuning circuit section consisting of series connection of plural inductance elements Z (short-circuit rods 8) and switch elements D (PIN diodes 7) is provided between an inner conductor 1 and a short-circuit face 3 of a coaxial cavity resonator consisting of the inner conductor 1, an outer conductor 2 and the short-circuit plane 3 to which one end of the conductor 2 is connected, and the switch elements D are turned on/off by a bias voltage given from a voltage application terminal of a bypass capacitor 6 to change the tuning frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed tuning filter used in a transceiver for frequency hopping communication.

[0002]

2. Description of the Related Art A high-speed tuning filter for a frequency hopping communication system, which is one of spread spectrum modulation systems that is resistant to interference and excels in confidentiality characteristics, has conventionally been mainly connected in parallel with a main capacitor to form a parallel resonant circuit. One or more series circuits in which different inductance elements and pin (PIN) diodes are connected in series are connected in parallel to a part of the inductance element, and by controlling the bias given to the PIN diode, the inductance element is It is configured to turn on / off to change the tuning frequency.

FIG. 1 is a diagram showing the principle of a circuit configuration for varying the tuning frequency of a filter. This resonance circuit is
Main tuning capacitance C ₀ between ND and inductance element L
It is a parallel resonant circuit composed of ₀₁ , L ₀₂ and L ₁ . When the switch S is open, the tuning frequency f ₁ of this circuit is expressed by the following equation (1).

[0004]

[Equation 1] The tuning frequency f ₂ when the switch S is short-circuited is expressed by the following equation (2).

[0005]

[Equation 2]

Therefore, f ₂ > f ₁ . Therefore, this circuit turns on / off the switch S so that f ₁ ,
It can be switch tuned to either of the two frequencies of f ₂ . Here the upper limit frequency f _2u of f ₂ is the case of L ₁ = 0, a _{f 2u = 1 / (2π√ (} C 0 L 01)). Therefore, the variable width of the tuning frequency is determined by the ratio of L ₀₁ and L ₀₂ , and it is possible to change the tuning frequency within the range of f ₁ <f ₂ <f _2u by setting L ₁ .

Specifically, a coaxial type cavity resonator in which one end of an outer conductor and one end of an inner conductor are short-circuited by a short-circuit surface is used as a basic structure,
Between the inner surface of the outer conductor and the inner conductor, a short-circuit rod and a PIN
A plurality of series circuits of diodes are arranged, and the short-circuit bar is turned on / off by controlling the PIN diode on / off.
A configuration in which the tuning frequency of the filter is switched according to the change in the inductance has been put into practical use. (Japanese Patent Application No. 4-1
(See No. 78843)

FIG. 2 is an equivalent circuit diagram showing a configuration example of a conventional variable tuning filter. Figure shows a BPF according to the conventional coaxial cavity resonator, L ₁ ~ connected in parallel to L ₀₂ in FIG. 1
Each switch S of L ₄ is connected to the PIN diode D ₁ ~
It has been replaced with D ₄ .

In FIG. 3, two conventional resonators are joined together,
This is an example of a two-stage configuration in which the windows are coupled by the coupling window 9. This is an example in which the principle of the lumped constant circuit shown in FIG. 2 is applied to a coaxial cavity resonator to realize a distributed constant. In FIG. 3, 1 is an inner conductor, 2 is an outer conductor, 3 is an inner conductor 1 and an outer conductor 2.
3 shows a short-circuited surface of FIG. 4 is an input / output connector, 5 is a coupling loop, 6 is a bypass capacitor (C _{1 to} C _{4 in} FIG. 2), 7
Is a PIN diode (D _{1 to} D ₄ in FIG. 2), and 8 is a short-circuit bar corresponding to the inductance elements Z _{1 to} Z ₄ in FIG. In this example, the short-circuit rods Z _{1 to} Z corresponding to L _{1 to} L _4
4 is the same value, and the position I from the short-circuit plane 3 of the cavity resonator is
_The tuning frequency is set to a predetermined value by changing _{1 to} I ₄ . Here, the short-circuit rod 8 and the PIN diode 7 are parts corresponding to the inductance element L ₁ and the switch S in FIG. 1, and constitute a variable tuning circuit section.

FIG. 4 is a partial structural sectional view of the variable tuning circuit section. The PIN diode 7 is attached to the tip of the short-circuit rod 8 and is connected to a feedthrough capacitor as the bypass capacitor 6. Reference numeral 7'denotes a bias voltage application terminal which is electrically connected to the PIN diode 7.

[0011]

However, since the variable tuning circuit is arranged on the inner surface around the outer conductor in the above-mentioned configuration, the following problems occur. (1) Since the mounting positions of the plurality of short-circuit rods 8 are scattered, the structure of the outer conductor 2 is complicated. (2) Since the plurality of short-circuit rods 8 all have the same length, an arbitrary inductance cannot be set. (3) In the case of the multi-stage structure, the resonators are coupled in the opposite directions as shown in FIG. 3, which results in a large space having a wasteful space around them. (4) In the case of a multi-stage configuration, the input / output connectors are separated as shown in FIG. (5) Maintenance is very troublesome because the variable tuning circuit units are individually independent. (6) Wiring to the bias voltage application terminal 7'is complicated.

The object of the present invention is to solve the above-mentioned conventional problems. (1) The structure of the outer conductor is simplified, and (2) an arbitrary variable inductance can be set. 3) It is possible to easily realize a multi-stage coupling of two or more stages, (4) A small space is provided even in a multi-stage configuration of two or more stages, and (5) Maintenance is facilitated. It is to provide the above high-speed tuning filter.

[0013]

A high speed tuning filter of the present invention is a coaxial cavity resonator in which one end of each of an inner conductor and an outer conductor is connected by a short-circuit surface, and the side surface of the inner conductor and the A variable tuning circuit unit is provided in which a short-circuit rod that serves as at least one inductance element and a pin diode that serves as a switch element are connected in series between the short-circuit surface and
The tuning frequency is changed by turning on / off the inductance element by controlling the bias applied to the pin diode via the voltage application terminal on the short-circuit surface.

[0014]

FIG. 5 is an equivalent circuit diagram of an embodiment of the present invention, and FIG. 6 is a structural example diagram showing a first specific example of the present invention, in which the front surface of the outer conductor 2 is removed. It is the side view which made the inside visible. In the figure, the same parts as those in FIGS. Reference numeral 9 is a coupling window portion. The high-speed tuning filter of the present invention is characterized in that the voltage applying section of the variable tuning circuit section is arranged on the short-circuit surface 3, and the coaxial cavity in which one end of the inner conductor 1 and one end of the outer conductor 2 are short-circuited by the short-circuit surface 3. A resonator, a PIN diode 7, a short-circuit rod or plate 8 of an inductance element, a bypass capacitor 6
The voltage applying terminal of the variable tuning circuit section consisting of is arranged on the short-circuit surface 3. Since the principle of frequency variable tuning is the same as that of the conventional example, no new problem arises with respect to frequency tuning.

FIG. 7 is a structural example showing the second embodiment of the present invention, and is a side view showing one side of the outer conductor 2 so that the inside can be seen. The difference from FIG. 6 is that the short-circuit rod 8 has a substantially L-shape. These have the following advantages. (1) By arranging the voltage application terminal of the tunable circuit section by moving it from the outer conductor 2 to the short-circuit surface 3, the outer conductor 2 does not require a process for arranging the voltage application terminal, which is a simple case. Therefore, it becomes possible to manufacture by inexpensive aluminum die casting. (2) Since nothing is arranged on the peripheral surface of the outer conductor 2, the two resonators can be coupled in the same direction as shown in FIGS. 6 and 7, so that a multistage configuration can be easily performed. (3) In addition, since the space occupied by the entire resonator is small and the input / output connectors can be arranged at the same positions facing each other, the volume occupied by the filter in the transceiver is reduced.

(4) Since all the voltage applying terminals are arranged on the same short-circuit surface 3, the wiring for the voltage applying terminals becomes easy when the multi-stage configuration is adopted. (5) The inner conductor 1 and the short-circuit surface 3 are integrally manufactured or assembled into one body, and the variable tuning circuit portion of the short-circuit rod (plate) 8, the PIN diode 7 and the bypass capacitor 6 is incorporated into the three bodies. Since the number of PIN diodes can be reduced to one, maintenance for damage to a plurality of PIN diodes can be easily performed by simply removing the PIN diodes from the outer conductor 2. (6) FIG. 8 and FIG. 9 are examples of arrangement of the plurality of short-circuit rods 8 on the short-circuit surface 3, and a substantially L-shaped short-circuit rod (plate) 8 arranged on the short-circuit surface 3.
May be arranged concentrically with the inner conductor 1 as shown in FIG. 8, or may be arranged at any position as shown in FIG. The inductance of can be set.

[0017]

According to the present invention, the following effects can be obtained by arranging the voltage application section of the variable tuning circuit section on the short-circuited surface. (1) The structure of the outer conductor 2 is simplified, and it is possible to manufacture by inexpensive aluminum die casting. (2) An arbitrary inductance can be set by the substantially L-shaped short-circuit bar (plate) 8. (3) Since a plurality of resonators can be coupled in the same direction, a multi-stage configuration of two or more stages is easily possible. (4) Since the resonators can be configured in multiple stages in the same direction,
The occupied volume can be made smaller than in the past. (5) Since the resonators can be configured in multiple stages in the same direction,
Wiring is easy because the applied voltage terminals are on the same surface. (6) Maintenance can be facilitated because the internal conductor, the short-circuit surface, and the variable tuning circuit unit can be integrated. As described above, by implementing the present invention, it is possible to provide the optimum BPF as the variable tuning BPF for frequency hopping.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a variable tuning circuit for explaining a frequency variable principle.

FIG. 2 is an equivalent circuit diagram of a conventional variable tuning filter.

FIG. 3 is a structural example diagram of a conventional two-stage configuration of a variable tuning filter.

FIG. 4 is an enlarged sectional view of a structure of a connecting portion of a short-circuit bar.

FIG. 5 is an equivalent circuit diagram of a variable tuning filter of the present invention.

FIG. 6 is a diagram showing a first specific structural example of the variable tuning filter of the present invention.

FIG. 7 is a diagram showing a second specific structural example of the variable tuning filter of the present invention.

FIG. 8 is a diagram showing an arrangement example of voltage application terminals on a short-circuit surface of the tunable filter of the present invention.

FIG. 9 is another layout example diagram of the voltage application terminals on the short-circuit surface of the tunable filter of the present invention.

[Explanation of symbols]

 1 Inner Conductor 2 Outer Conductor 3 Short-Circuiting Surface 4 I / O Connector 5 Coupling Loop 6 Bypass Capacitor (Voltage Applying Terminal) 7 PIN Diode 7'Voltage Applying Terminal 8 Short-Circuiting Rod (Plate) 9 Coupling Window

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinichi Kudo 3--14-20 Higashinakano, Nakano-ku, Tokyo Inside Kokusai Electric Corporation

Claims (5)

[Claims] 1. A coaxial cavity resonator in which one end of each of an inner conductor and an outer conductor is connected by a short-circuit surface, and at least one inductance element is provided between a side surface of the inner conductor and the short-circuit surface. Is provided with a variable tuning circuit section in which a short-circuiting rod and a pin diode serving as a switching element are connected in series, and the inductance element is turned on / off by controlling a bias applied to the pin diode via a voltage application terminal on the short-circuit surface. A fast tuned filter configured to turn off and change the tuning frequency. 2. The high speed tuning filter according to claim 1, wherein the short-circuit rod is formed in a substantially L shape. 3. The high-speed tuning filter according to claim 1, wherein the inner conductor, the short-circuit surface and the variable tuning circuit section according to claim 1 are integrally formed. 4. The high speed tuning according to claim 1, wherein the voltage application terminals of the variable tuning circuit unit according to claim 1 are arranged concentrically around a connection point of the inner conductor of the short-circuited surface. filter. 5. A high-speed tunable filter comprising at least two coaxial cavity resonators according to claim 1, wherein the resonators are arranged and coupled in parallel in the same direction to form a multistage structure.