JP2003023304A - Microwave filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave filter with which frequency characteristics can be adaptively changed to become optimal, production is facilitated and an entire area can be made small. SOLUTION: In the microwave filter with which one-side terminals 51A and 52A of respective stabs 51 and 52 composed of a pair of microstrip lines for different lengths are connected to a signal line 3 composed of a microstrip line, as switch means which can be respectively turned on/off, diodes 71 and 72 are connected to other-side terminals 51B and 52B of the respective stabs 51 and 52 and grounded and a switch control circuit 9 is provided as a switch control means for controlling the ON/OFF of the diodes 71 and 72 as respective switch means.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a microwave filter used in a high frequency band.

[0002]

2. Description of the Related Art A conventional microwave filter used in a high frequency band comprises a signal line composed of microstrip lines installed on a substrate and a microstrip line installed on a pair or a plurality of pairs of substrates. Some have stubs connected. One of the stubs in the pair or the plurality of pairs is grounded to form a short stub, and the other is opened to form an open stub.

FIG. 7 shows an example of a conventional microwave filter in which a plurality of pairs of stubs are connected. Microwave filter 1
01 includes a signal line 103 formed of a microstrip line installed on the substrate.
, And short stubs 151, 153, ... And open stubs 152, 154 ,. The signal line 103 includes a signal input terminal 103A to which a signal is input and a signal output terminal 10 to which a signal is output.
3B is provided.

Here, the electrical characteristics of the stub will be described with reference to FIG. λ0 is the wavelength of the signal of frequency f0. As shown in FIG. 2A, a short stub having an electrical length of λ0 / 4 is electrically equivalent to an open circuit, and
As shown in (b), an open stub having an electrical length of λ0 / 4 is electrically equivalent to a short circuit. Also, FIG.
As shown in (c), the short stub shorter than the electrical length λ0 / 4 is electrically equivalent to the inductor, and
As shown in (d), the open stub shorter than the electrical length λ0 / 4 is electrically equivalent to a capacitor.

A resonator is formed by a short stub functioning as an inductor and an open stub functioning as a capacitor. For example, as shown in FIG. 7, the resonator 10 includes a short stub 151 and an open stub 152.
4 is formed. The resonator 104 functions as a bandpass filter. The resonance frequencies of the resonator 104 are the short stub 151 and the open stub 152.
Depends on the length of. Then, by combining the short stubs 151, 153, ... And the open stubs 152, 154, ... With different lengths, a plurality of resonators are formed, and a filter satisfying a desired frequency characteristic is realized. You can

[0006]

However, the short stubs 151, 153, ... And the open stub 15 are to be solved.
The combination with 2, 154, ... And the length thereof are fixed, and it is impossible to adaptively change the frequency characteristic. Further, in order to realize the adaptive frequency variable filter, a complicated circuit configuration with high component cost is required.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional technique and to adaptively change the frequency characteristics so that the frequency characteristics are optimum, and the production is easy.
An object of the present invention is to provide a microwave filter which can reduce the entire area.

[0008]

The invention according to claim 1 is
In a microwave filter in which one end of a stub consisting of a pair of microstrip lines having different lengths is connected to a signal line consisting of a microstrip line, the other end of each stub is connected to a switch means capable of turning on and off, and grounded. A switch control means for controlling ON / OFF of each switch means is provided.

According to a second aspect of the present invention, there is provided a microwave filter in which one end of a stub composed of a plurality of pairs of microstrip lines having different lengths is connected to a signal line composed of a microstrip line, and the other end of each stub is connected to the other end. The present invention is characterized by including switch control means for controlling on / off of each switch means by connecting switch means capable of turning on / off and grounding.

According to a third aspect of the present invention, in the second aspect of the invention, each of the stubs connected to the signal line is located substantially on the same line in each pair.

According to a fourth aspect of the present invention, in the second aspect of the invention, one end of each of the stubs connected to the signal line is arranged close to each other.

The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the switch means is
It is characterized by being a diode.

According to a sixth aspect of the invention, in the invention according to the fifth aspect, the switch control means connects a capacitor for cutting a direct current between each of the stubs and each of the diodes, and each of the diodes is connected. And a connection point between each capacitor and each of the capacitors, an on-off control unit for controlling a DC voltage to be applied to each of the diodes is connected via a choke coil. .

In the invention according to any one of claims 1, 2, 5, or 6, since the frequency characteristic changes depending on whether the switch means is turned on or off, the frequency is controlled by controlling the on / off of the switch means by the switch control means. It can be adaptively changed so that the characteristic becomes optimum.

According to the third aspect of the invention, since each stub connected to the signal line is located on the substantially same line in each pair, the production is easy.

According to the invention described in claim 4, since one end of each stub connected to the signal line is arranged close to each other, the entire area can be reduced.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[A] First Embodiment FIG. 1 shows a circuit diagram of a microwave filter according to a first embodiment. Reference numeral 1 denotes a microwave filter used in a high frequency band. The microwave filter 1 includes a signal line 3 composed of a microstrip line installed on a substrate and a microstrip installed on a pair of substrates having different lengths. Line stubs 51 and 52, diodes 71 and 72 as switching means, and diode 7
And a switch control circuit 9 as a switch control means for selectively turning on and off 1,2. The signal line 3 includes a signal input terminal 3A to which a signal is input and a signal output terminal 3B to which a signal is output. One ends 51A and 52A of the stubs 51 and 52 are connected to the signal line 3, and the other ends 51B and 52B of the stubs 51 and 52 are grounded via the diodes 71 and 72.

Here, the electrical characteristics of the stub will be described with reference to FIG. λ0 is the wavelength of the signal of frequency f0. As shown in FIG. 2A, a short stub having an electrical length of λ0 / 4 is electrically equivalent to an open circuit, and
As shown in (b), an open stub having an electrical length of λ0 / 4 is electrically equivalent to a short circuit. Also, FIG.
As shown in (c), the short stub shorter than the electrical length λ0 / 4 is electrically equivalent to the inductor, and
As shown in (d), the open stub shorter than the electrical length λ0 / 4 is electrically equivalent to a capacitor. A resonator is formed by the short stub that functions as an inductor and the open stub that functions as a capacitor. This resonator functions as a bandpass filter.

In FIG. 1, when the diodes 71 and 72 are turned on, the stubs 51 and 52 become short stubs, and when the diodes 71 and 72 are turned off, the stub 5 is turned on.
1, 52 are open stubs. Here, the switch control circuit 9 switches between the case where the diode 71 is on and the diode 72 is off, and the case where the diode 71 is off and the diode 72 is on. As a result, the stubs 51 and 52 are selectively switched between a short stub that functions as an inductor and an open stub that functions as a capacitor. The resonator 4 is formed by the short stub and the open stub.

Since the stub 51 and the stub 52 have different lengths, the stub 51 functions as an inductor and the stub 52 functions as a capacitor, and the stub 51 functions as a capacitor and the stub 52 functions as an inductor. The resonance frequency differs depending on the case. Therefore, by switching the diodes 71 and 72 on and off, the bandpass filter has a frequency characteristic that is switched.

Next, the structure of the switch control means will be described with reference to the circuit diagram shown in FIG. FIG. 3 shows a switch control circuit 9 as a switch control means. For example, a case where the diode 71 as a switch means is on / off controlled will be described.

As shown in FIG. 3, a capacitor 11 for cutting direct current is connected between the stub 51 and the diode 71. The capacitor 11 has a large capacity that does not affect the frequency characteristics. At a connection point A between the diode 71 and the capacitor 11, an on / off control unit 15 for generating a DC voltage and controlling the DC voltage to be applied to the diode 71 is connected via a choke coil 13. The capacitor 11 prevents a direct current component from flowing to the signal line 3 via the stub 51 when a direct current voltage is applied to the diode 71 by the on / off control unit 15. Further, the choke coil 13 prevents the AC component from the stub 51 from flowing to the on / off control unit 15.

When the diode 71 is turned on, a direct current voltage is generated by the on / off control section 15 and the connection point A
A DC voltage is applied to. Then, a DC voltage is applied to the diode 71 so that the diode 71 becomes conductive. When turning off the diode 71, the application of the DC voltage by the on / off control unit 15 may be stopped.

In the case where the diode 72 is on / off controlled, the on / off control section 15 controls the on / off as in the case of the diode 71.

According to the first embodiment, the signal line 3 made up of microstrip lines is provided with the stubs 51 made up of a pair of microstrip lines having different lengths.
One end 51A, 52A of 52 is connected, and stubs 51, 52 are connected.
To the other ends 51B and 52B of the diodes 71 and 72, respectively.
Is connected to ground, and the switch control circuit 9 controls ON / OFF of the diodes 71 and 72. By selectively switching between a short stub that functions as an inductor and an open stub that functions as a capacitor, the frequency characteristic is The frequency characteristics can be changed, and the frequency characteristics can be adaptively changed so as to be optimum.

[B] Second Embodiment FIG. 4 shows a microwave filter according to a second embodiment of the present invention, and is a circuit diagram when a plurality of pairs of stubs are connected to signal lines. In this second embodiment,
The same parts as those in the first embodiment are designated by the same reference numerals and omitted.

As shown in FIG. 4, the microwave filter 10 includes a signal line 3 composed of a microstrip line.
And stubs 51, 52, 53, 54, 55, 56, which consist of a plurality of pairs of microstrip lines having different lengths.
..And diodes 71, 72 as switching means
73, 74, 75, 76, ... and the diode 71,
Switch control circuit 9 as switch control means for selectively turning on / off 72, 73, 74, 75, 76, ...
(FIG. 3).

Stubs 51, 52, 53, 54, 55, 5
6, one end 51A, 52A, 53A, 54A, 5
5A, 56A, ... Are connected to the signal line 3 and the other ends 51B, 52B, 53B, 54B, 55B, 56B ,.
.... Diodes 71, 72, 73, 74, 75, 7
It is grounded through 6, ... Where each stub 5
1, 52, 53, 54, 55, 56, ... are stubs 51, 52, stubs 53, 54, stubs 55, 56, ...
.. are paired and are arranged so as to be located on substantially the same line in each pair, and each pair is arranged in parallel.

As the switch control means, the switch control circuit 9 shown in FIG. 3 controls not only the diode 71 but also the diodes 72, 73, 74, 75, 76, ... This diode 71,
The frequency characteristics are changed by changing the combination of the open stub and the short stub by the on / off control of 72, 73, 74, 75, 76, .... For example, when there are two types of combinations of open stubs and short stubs, by changing the combination of open stubs and short stubs, for example, as shown in FIG.
The frequency characteristics are changed by switching between the types of frequency characteristics (a) and (b). Here, there are two types of combinations of the open stub and the short stub, but two or more types of combinations are possible, and the frequency characteristic is changed according to this combination.

Therefore, according to the second embodiment,
The same effect as that of the first embodiment is obtained, and further, each stub 51, 52, 53, 54, 55, 56, ...
Stubs 51, 52, stubs 53, 54, stubs 55, 5
6 ... form a pair, and are arranged so as to be located on substantially the same line in each pair, and each pair is arranged in parallel, which facilitates production.

In the second embodiment, each stub 51, 5
2, 53, 54, 55, 56, ... are stubs 51,
52, the stubs 53, 54, the stubs 55, 56, ... Form a pair, and the pairs are arranged so as to be located substantially on the same line, and the respective pairs are arranged in parallel. Stubs 51, 52, 53, 54 connected to the signal line 3 like the microwave filter 20 shown in FIG.
One end of 55, 56, ... 51A, 52A, 53A, 5
4A, 55A, 56A, ... May be arranged close to each other. In this case, there is an effect that the entire area can be reduced.

Although the present invention has been described based on the embodiment, the present invention is not limited to this.

[0034]

The frequency characteristics can be adaptively changed so as to be optimum, production is easy, and the entire area can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a microwave filter according to the present invention.

2A and 2B are diagrams showing electrical characteristics of a stub. FIG. 2A is a short stub having an electric length of λ0 / 4, FIG. 2B is an open stub having an electric length of λ0 / 4, and FIG. Long λ
In the case of the short stub shorter than 0/4, (d) is a diagram showing the case of the open stub shorter than the electrical length λ0 / 4.

FIG. 3 is a circuit diagram showing switch control means.

FIG. 4 is a circuit diagram showing a second embodiment of a microwave filter according to the present invention.

FIG. 5 is a diagram showing an example of changing frequency characteristics.

FIG. 6 is a circuit diagram showing a second embodiment of a microwave filter according to the present invention.

FIG. 7 is a circuit diagram showing a conventional microwave filter.

[Explanation of symbols]

1 Microwave Filter 3 Signal Line 9 Switch Control Circuit (Switch Control Means) 10 Microwave Filter 11 Capacitor 13 Choke Coil 15 On / Off Control Unit 20 Microwave Filter 51, 52, 53, 54, 55, 56 Stubs 51A, 52A, 53A , 54A, 55A, 56A One end 51B, 52B, 53B, 54B, 55B, 56B Other end 71, 72, 73, 74, 75, 76 Diode (switch means) A Connection point

Claims (6)

[Claims] 1. A microwave filter in which one end of a stub composed of a pair of microstrip lines having different lengths is connected to a signal line composed of a microstrip line, and a switch means capable of being turned on and off is provided at the other end of each stub. A microwave filter comprising switch control means for connecting and grounding and controlling ON / OFF of each switch means. 2. A microwave filter in which one end of a stub composed of a plurality of pairs of microstrip lines having different lengths is connected to a signal line composed of a microstrip line, and a switch means capable of being turned on / off at the other end of each stub. A microwave filter comprising switch control means for controlling ON / OFF of each switch means by connecting to each other and grounding. 3. The microwave filter according to claim 2, wherein the stubs connected to the signal line are located on substantially the same line in each pair. 4. The microwave filter according to claim 2, wherein one ends of the stubs connected to the signal line are arranged close to each other. 5. The microwave filter according to claim 1, wherein the switch means is a diode. 6. The switch control means connects a capacitor that cuts direct current between each stub and each diode, and a choke coil is provided at a connection point between each diode and each capacitor. The microwave filter according to claim 5, wherein an on / off control unit that controls to generate a DC voltage and apply the DC voltage to each of the diodes is connected.