JP3408386B2 - Polarized band-stop filter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarized band stop filter using a coupled line and a resonator.

[0002]

2. Description of the Related Art Conventionally, band stop filters in which a resonance circuit is directly connected to an input and an output of a line are known.

[0003]

With the recent digitization of signals, there has been a demand for a narrow-band band-elimination filter with a high frequency and a good rise attenuation characteristic.
There was a problem that it was difficult to realize.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a band elimination filter capable of solving such a problem.

[0005]

In order to achieve the above-mentioned object, the invention of claim 1 has a first line (1) and a second line (2) coupled to each other on a ground plate (3). The center frequency (f ₀ ) of the band which is arranged and blocks as a filter at both terminals (4) and (5) of one of these two lines (1) and (2) is referred to as an anti-resonance frequency. The resonator (6) (6) to be connected and the other line (1)
Is a polar band stop filter characterized in that each of the ends (7) and (8) thereof is used as an input and an output, respectively. Claim 2
The invention provides a polarized band stop filter according to claim 1,
A coupling line consisting of a first line (1) and a second line (2)
Within the band where the line length of the path (9) is blocked as a filter
Characterized by setting the wavelength to approximately 1/4 of the heart frequency (f ₀ ).
It is what The line length is f as in the design example described later.
_{It is preferable to set it to} a quarter wavelength of ₀ (λ 0/4 ). Claim 3
The invention provides a polarized band stop filter according to claim 1,
A coupling line consisting of a first line (1) and a second line (2)
Within the band where the line length of the path (9) is blocked as a filter
Other than near 1/2 wavelength of the heart frequency (f ₀ ) and its integral multiples
It is characterized in that it is set to the value of. Coupled line
The line length (L _c ) in (9) is centered as in the design example described later.
Toka to frequency 1/4 wavelength of _{(f 0) (λ 0/} 4),
FIG. 6 which will be described with reference to the configuration principle of the filter of the present invention described later.
As described above, the electrical angle βL _c of the coupled line (9) is 0 and π, and
Attenuation becomes large except for the vicinity of integer multiples
It is good to set the track length. That is, the electrical angle βL _c becomes 0
Since it has no meaning for direct current, it is not applicable, and the electrical angle βL _c is
As the line length excluding the frequency around π and its integral multiple
Te, half wavelength of the center frequency _{(f 0) (λ 0/} 2) and
The value excluding the vicinity of the integer multiple.

According to a fourth aspect of the invention, in the polarized band stop filter according to the second or third aspect , the resonators (6) and (6) are parallel circuits of a coil (L) and a capacitor (C) of a lumped constant circuit. It is characterized by being configured.

According to a fifth aspect of the present invention, in the polarized band stop filter according to the fourth aspect , a short-circuit stub (12) having a line length (Lr) is used instead of the coil (L) of the lumped constant circuit. It is what

The invention of claim 6 is the same as claim 2 or
In the polarized band stop filter of No. 3 , the resonator (6)
(6) is characterized in that is constituted by a length of a quarter wavelength of the center frequency of the band to prevent (lambda _0/4) of the short-circuit stub (13).

[0009]

[Example 1]

FIG. 1 corresponds to claims 1 , 2 and 3 , wherein a first line 1 and a second line 2 which are coupled to each other are arranged on a ground plate 3, and among these two lines 1 and 2, Connected to both terminals 4 and 5 of one line 2 are resonators 6 and 6 each having a center frequency f ₀ of a band to be blocked as a filter as an anti-resonance frequency, and each end 7 and 8 of the other line 1 It has an input and an output.

[0010] Design Example reference numeral 9 indicates a bond line made of a first line 1 and the second line 2 which, the line length, to be described later
As shown in, in a quarter wavelength lambda _0/4 of the center frequency f ₀
Or, as described in the filter configuration principle described later.
And the electrical angle βLc of the coupled line is π
, And frequencies near its integral multiple are excluded.
That is, half the wavelength of the center frequency f ₀ of the line length (lambda ₀ /
2) and a value other than an integer multiple thereof. The actual input signal is applied between the input terminal 10 connected to the one end 7 of the line 1 and the ground portion 10 '. The output signal is output from the output terminal 11 connected to the other end 8 of the line 1 and the ground portion 1.
1 '.

The resonators 6 and 6 are composed of a lumped constant circuit, a distributed constant circuit or a combination thereof, and are inserted and connected between the terminals 4 and 5 of the line 2 and the ground plate 3. [Second Embodiment] As shown in FIG. 2, the resonators 6 and 6 of the first embodiment shown in FIG. Is tuned to the center frequency of the band that blocks as a filter. This embodiment corresponds to the invention of claim 4 .

Third Embodiment As the resonators 6 and 6 of the first embodiment shown in FIG. 1, instead of the coil L of the resonator 6 of FIG. 2, the characteristic impedance is Wr and the line length Lr is shorter than ¼ wavelength. One end of the distributed constant line 12 is connected to one end of the capacitor Cr as shown in FIG. 3, and the other end of the line 12 is connected to the ground plate 3 for short circuit. Therefore, this line 12 is called a short-circuit stub.

With the capacitor Cr and the short-circuit stub 12,
The resonator 6 having the center frequency of the stop band of the filter as the anti-resonance frequency is configured. The third embodiment corresponds to claim 5 .

[Embodiment 4] As the resonators 6 and 6 shown in FIG. 1, a short-circuit stub 13 having a length of 1/4 of the wavelength λ ₀ of the center frequency of the stop band of the filter is provided as shown in FIG. And corresponds to the invention of claim 6.

[Principle of Construction of Polarized Band Stop Filter of the Present Invention] As shown in FIG. 5 (a), a circuit in which both ends of one line 2 constituting the coupled line 9 are open is shown in FIG. The characteristic impedance W ₀ shown is equivalent to one line 14 on the ground plate 3 with W ₀ = Wu + Wb / 4.

Note that Wu is a characteristic impedance of unbalanced transmission of the coupling line 9, and Wb is a characteristic impedance of balanced transmission. Therefore, the equivalent characteristic impedance can be made sufficiently larger than the load resistance in the coupled line in which Wu is increased, and in this case, the transmission characteristic of the circuit in FIG. 5A is βLc 0 as shown in FIG. Attenuation becomes large except for the vicinity of π and a frequency that is an integral multiple thereof, and the circuit becomes an attenuator.

Lc is the length of the coupled line, and βLc is the connection length.
It is the electrical angle of the junction line . Further, as shown in FIG. 7A, a circuit in which one end of one line 2 constituting the coupling line is grounded has a characteristic impedance Ws as shown in FIG. 7B.
Is equivalent to one line 15 on the ground plate 3 with Ws = 4WbWu / (Wb + 4Wu), and if W
If u is set to a sufficiently large value, the line has a characteristic impedance close to Wb. Therefore, by setting Wb to the same value as the load resistance, this circuit becomes an all-pass type circuit and no attenuation occurs.

From these points, FIG. 5 (a) and FIG.
It is understood that various filters can be obtained by switching the circuit of (a) on the frequency. In the circuit of FIG. 1, the switching for switching to the band stop filter uses the resonator 6 of FIG. 2, FIG. 3 or FIG.

In the vicinity of the anti-resonance frequency of the resonator 6, FIG.
The circuit shown in FIG. 7A serves as an attenuation band, and the circuit shown in FIG. 7A serves as a pass band at frequencies far apart from the antiresonance frequency. Then, when changing from the pass band to the attenuation band and from the attenuation band to the pass band, the transmission mode of the coupling line 9 is switched, so that the transmission of the signal almost stops at that frequency, and an attenuation pole that greatly attenuates is generated.

Based on such a principle, a polarized band stop filter having an attenuation characteristic as shown in FIG. 8 can be obtained. In order to calculate the attenuation characteristic, the operation attenuation amount is calculated from the basic four-terminal parameter of the circuit of FIG. 1 shown in [Equation 1].
However, the resonator uses the circuit using the circuit of FIG. 3 as an example.

Since the circuit of FIG. 1 is a symmetrical circuit,

[0022]

[Equation 1]

Then, A = a + b ₂ c ₂ Zr / d B = j (b ₁ -b ₂ ² / d) C = j (c ₁ + c ₂ ² Zr ² / d), where a = cos βLc b ₁ = Wu (1 + Wb / 4Wu) sin βLc b ₂ = Wu (1-Wb / 4Wu) sin βLc c ₁ = {(1 / 4Wu) + (1 / Wb)} sin βLc c ₂ = {(1 / 4Wu)- (1 / Wb)} sin βLc d = 2 a Zr + b ₁ −c ₁ Zr ² Zr = j Wrtan βLc / (1-ωCrWrtan β
Lr).

[Design Example] FIG. 9 shows calculated values of the attenuation characteristics of the polarized band stop filter of FIG. 1 using the resonator 6 of FIG. For the frequency, the center frequency f ₀ of the stop band is standardized as 1, and each element value also has a load resistance of 1
Is shown as a standardized value.

As is apparent in the design example of the element values Wu = 6 Wb = 1.0435 Lc = λ 0/4 Wr = 0.1 Lr = λ 0/20 Cr = 30.8 Figure 9, the recent signal A filter characteristic for blocking a specific narrow-band signal accompanying digitization, that is, a band-stop filter of two adjacent poles with good rising attenuation poles in an attenuation amount within a range that has little influence on both adjacent passband signals, It can be realized in the range of MHz to GHz.

[0026]

Since the polarized band stop filter of the present invention is constructed as described above, it is possible to meet the recent demand for a narrow band stop filter that accompanies digitalization, and to put the digital signal technology into practical use, Contribute to promotion.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a resonator used in a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a resonator used in a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a resonator used in a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram for explaining the configuration principle of the present invention, (a)
Is a circuit when both ends of one line are opened, and (b) is an equivalent circuit of FIG.

FIG. 6 is a characteristic diagram of the circuit of FIG.

FIG. 7 is a circuit diagram illustrating a configuration principle of the present invention, (a)
Is a circuit when both ends of one line are grounded, and (b) is an equivalent circuit of FIG.

FIG. 8 is an attenuation characteristic diagram of the polarized band stop filter of the present invention.

FIG. 9 is a diagram of a design example of the attenuation characteristics of the polarized band stop filter of the present invention, in which the frequency is standardized.

[Explanation of symbols]

1, 2 Line 3 Ground plate 4, 5 Terminal 6 Resonator 7, 8 End 9 Coupling line 10 Input terminal 11 Output terminal 12, 13 Short circuit stub C, Cr Capacitor Lc Length of coupling line Lr Line length of short circuit stub 12 ₀ wavelength

Claims (6)

(57) [Claims] 1. A first line (1) and a second line coupled to each other.
Of the two lines (1) and (2) of the two lines (1) and (2) are blocked by both ends (4) and (5) of the two lines (1) and (2) as a filter. Resonator (6) (6) having the center frequency (f ₀ ) of the band as the anti-resonance frequency
And the other end (7) of the other line (1)
A polarized band stop filter having (8) as an input and an output, respectively. 2. A first line (1) and a second line (2)
The length of the coupled line (9) consisting of
Center frequency of stop band (f ₀ ) Fixed to about 1/4 wavelength
The polarized band stop filter according to claim 1, wherein
Ilta. 3. A first line (1) and a second line (2)
The length of the coupled line (9) consisting of
Center frequency of stop band (f ₀ ) 1/2 wavelength and its
A value other than a value in the vicinity of an integral multiple is set.
Polarized band stop filter described. 4. The polarized band stop according to claim 2, wherein the resonators (6) (6) are constituted by a parallel circuit of a coil (L) and a capacitor (C) of a lumped constant circuit. filter. 5. The polarized band stop filter according to claim 4, wherein a short circuit stub (12) having a line length (Lr) is used instead of the coil (L) of the lumped constant circuit. 6. A claim, characterized in that is constituted by the resonator (6) 1/4 length of the wavelength of the center frequency of the band to prevent (6) (lambda _0/4) of the short-circuit stub (13) 2 or 3
Polarized band stop filter described.