JP3461420B2 - Dielectric 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 1/4 wavelength resonant circuit dielectric filter.

[0002]

2. Description of the Related Art FIG. 9 is a perspective view showing the structure of a conventional dielectric filter, FIG. 10 is a cross sectional view thereof, FIG. 11 is an equivalent circuit diagram thereof, and FIG. 12 is an explanatory view showing its electric field distribution and magnetic field distribution. FIG. 13 is an explanatory diagram showing the frequency characteristic. Figure 9
As shown in FIG. 10, the substantially rectangular parallelepiped-shaped dielectric block 1 is formed with two parallelepiped bottomed holes that open at the front surface and face toward the rear surface. Inner conductors 2-1 and 2-2 are formed on the inner surfaces, respectively. Therefore, as shown in FIG. 10, the horizontal cross section of the dielectric block 1 is formed in a substantially E shape. Further, the outer conductor 6 is formed on the outer peripheral surface of the dielectric block 1, and further, the entire front surface of the dielectric block 1 is short-circuited to short-circuit the inner conductors 2-1 and 2-2 and the outer conductor 6. The conductor 5 is formed. In addition, the inner conductor 2- is provided on both side surfaces of the dielectric block 1.
Input / output electrodes 4-to connect to 1 and 2-2, respectively.
1, 4-2 are provided, a hole is formed, and connection conductors 3-1 and 3-2 are formed on the inner surface of the hole. As another conventional example, there is also known one in which the inner conductors 2-1 and 2-2 and the input / output electrodes 4-1 and 4-2 are capacitively connected instead of being directly connected. Such a dielectric block 1 is manufactured by a method such as pressing or injection molding a dielectric material for microwaves, and the conductors and electrodes are formed by baking a conductive paste or electroless plating. .

This dielectric block 1 has two inner conductors 2-
Since one end of each of 1 and 2-2 is short-circuited to the outer conductor 6 and the other end is terminated by a capacitive element, a quarter-wave type parallel resonant circuit is formed, and its equivalent circuit is resonant as shown in FIG. Track 8
-1, 8-2 and termination capacitors 7-1, 7-2. Here, the resonance lines 8-1 and 8-2 correspond to the inner conductors 2-1 and 2-2, respectively, and the terminating capacitors 7-1 and 7-2.
-2 is a capacitance formed between the open ends of the inner conductors 2-1 and 2-2 (bottom surface of the hole) and the outer conductor 6, respectively.

[0004]

FIG. 12A shows distribution curves of magnetic field and electric field at the resonance frequency f ₀ .
13B shows a distribution curve of the magnetic field and the electric field at the frequency f _t of the attenuation pole shown in FIG. FIG. 12 (a),
In (b), reference numeral 7 indicates a terminating capacitance, reference numeral 8 indicates a resonance line, the horizontal axis indicates the strength of the electric field and the magnetic field, and the vertical axis indicates the position on the line 8. The magnetic field distribution curve can be represented by a cosine wave curve whose origin is the short-circuit end 8a, and the electric field distribution curve can be represented by a sine wave curve whose origin is the short-circuit end 8a.

In this case, the areas of the shaded portions a and b represent the magnetic field strength and the electric field strength of the resonance line 8, respectively.
Further, the point c is a position where the phase at the resonance frequency f ₀ including the amount shortened by the terminal capacitance 7 becomes 90 degrees. That is, FIG. 12A shows the electromagnetic field distribution at the resonance frequency f ₀ where λ / 4 is between the short-circuited end 8a and the point c. As is clear from the figure, the shaded area a is larger than the shaded area b at the resonance frequency f ₀ . This indicates that the magnetic field coupling is dominant in the resonance line 8.

On the other hand, as shown in FIG. 12 (b), a magnetic field distribution curve and an electric field distribution curve in which the area of the shaded portion a (strength of magnetic field) and the area of the shaded portion b (strength of electric field) are equal are shown. The loss becomes infinite (attenuation pole) at the frequency that can be drawn. As is apparent from FIG. 12B, the areas of the shaded portions a and b are equal at the frequency f _{t where} λ / 4 is between the short-circuit end 8a and the point d corresponding to the length of the resonance line 8. The point d exists at a position shorter than the 90 degree position at the fundamental frequency f ₀ . That is, the attenuation pole frequency f _t exists above the pass frequency band.

FIG. 13 shows the bandpass filter (BPF) characteristic of the above conventional example, and the horizontal axis represents frequency (0 to 6 GH).
z), and the vertical axis is the attenuation amount ATT (-80 to 0 dB).
In the figure, indicates the fundamental frequency f ₀ , the second harmonic wave 2f ₀ , and the third harmonic wave 3f ₀ , respectively, and the above-mentioned attenuation poles are f ₀ <f _t <2f ₀ <3f ₀ . . However, in the dielectric BPF using the quarter-wave resonator having such a characteristic, spurious resonance occurs at a frequency that is an odd multiple of three times, five times, or the like of the fundamental frequency f ₀ and becomes a pass band.
There is a problem that the attenuation for frequencies of 2f ₀ and 3f ₀ is insufficient (in FIG. 13, 2f ₀ : -17d, respectively).
B, 3f ₀ : −8 dB). Therefore, it is necessary to actually a combination of the LPF blocks the frequency of, for example, 2f _0, 3f ₀ used.

With the recent increase in the frequency of wireless communication systems, the oscillation frequency and image (image) frequency of the local oscillator are often lower than the communication frequency, and in order to eliminate them, the frequency is lower than the communication frequency f _0. A dielectric filter having an attenuation pole is desired. However, in the above-mentioned conventional example, since there is no attenuation pole below the fundamental frequency f ₀ , this cannot be realized. Therefore, another trap circuit is required to eliminate the local oscillation frequency and the image frequency.

In view of the above-mentioned conventional problems, the present invention provides a dielectric filter capable of surely blocking frequencies above and below the fundamental frequency and realizing a bandpass characteristic of allowing the fundamental frequency to pass. With the goal.

[0010]

According to the present invention, a plurality of resonant lines that are electromagnetically coupled to each other inside a dielectric block, and one end of each of the plurality of resonant lines and an outer conductor are short. A plurality of short-circuit connection conductors that are connected in a short circuit, and a plurality of
The short-circuit connection conductors of the two reduce the electromagnetic coupling with each other
Place in decoupling state and connect multiple resonant lines and
1/4 wavelength resonant circuit with short-circuit connecting conductor
I am doing . With such a configuration , by appropriately setting the length of each resonance line, that is, its impedance, and the length of each short-circuit connecting conductor, that is, its impedance, the lower frequency region of the pass frequency and the upper frequency region
It can give rise to attenuation poles on both the number area, it
A more desired amount of attenuation can be produced.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION One dielectric filter of the present invention is provided .
The outer surface of the dielectric block except the outer surface of the
And inside the dielectric block,
A plurality of inner conductors arranged in an electrically coupled state,
Each of the one ends of the plurality of inner conductors on one outer surface
Multiple short-circuit connections that connect each of these with the outer conductor
A conductor and connected to the inner conductors and the inner conductors
1/4 wavelength resonant circuit with short-circuit connection conductor
Comprising a plurality of said shorts on said one outer surface
Part connection conductors should be electromagnetically coupled to each other.
Has a configuration that is arranged in a decoupled state to reduce
It With such a configuration, it is possible to reliably block the upper frequency and the lower frequency of the fundamental frequency and realize the bandpass characteristic of allowing the fundamental frequency to pass.

Further, the dielectric filter of the present invention has a single
An opening is provided on the outer surface, and the one outside
Faces parallel to each other and spread in the direction of the outer surface.
A dielectric block having a bottom hole and the plurality of parallel bottomed
A plurality of inner conductors formed and arranged along the inner surface of the hole,
That of one of said plurality of inner conductors on one outer surface
Multiple short-circuit connections that connect each one to the outer conductor
A plurality of inner conductors and are connected to them.
1/4 wavelength resonant circuit with short-circuit connecting conductor
And the plurality of shorts on the one outer surface.
The connection conductors of the junction are electromagnetically coupled to each other.
Has a configuration that is arranged in a decoupled state to reduce
There is. With such a configuration, it is possible to reliably block the upper frequency and the lower frequency of the fundamental frequency and realize the bandpass characteristic of allowing the fundamental frequency to pass.

In this case, in a plurality of short-circuit connecting conductors
The decoupling arrangement is on one end of the dielectric block.
And radially separate from one end of each of the inner conductors.
To extend in the direction that
Direction that radially separates from each end of the conductor
It can be placed in a recess that extends into
Direction that does not cross each other from one end of the conductor
In the state where the electromagnetic shield is formed around the
It is effective to arrange them.

[0014]

EXAMPLES Examples will be described with reference to the drawings.
1 is a perspective view showing a dielectric filter according to a first embodiment of the present invention, FIG. 2 is a cross sectional view showing the dielectric filter of FIG. 1, FIG. 3 is an equivalent circuit diagram of the dielectric filter of FIG. 4 is an explanatory diagram showing an example of an electric field distribution and a magnetic field distribution of the dielectric filter of FIG. 1, and FIG. 5 is an explanatory diagram showing an example of frequency characteristics of the dielectric filter of FIG.

As shown in FIGS. 1 and 2, the short-circuit connecting conductor 1 is formed on the front surface 1-a of the dielectric block 1 according to this embodiment.
1-1 and 11-2 (microstrip lines) are formed, and this point is a short circuit for short-circuiting the inner conductors 2-1 and 2-2 and the outer conductor 6 over the entire front surface of the dielectric block 1. This is different from the conventional example in which the conductor 5 is formed. More specifically, two parallelepiped bottomed holes that are open at the front surface 1-a of the substantially rectangular parallelepiped dielectric block 1 and extend toward the rear surface are formed along the front-rear direction. Inner conductors 10-1 and 10-2 are formed on the inner surfaces of the parallelepiped bottomed holes, respectively. Therefore, as shown in FIG. 2, the horizontal cross section of the dielectric block 1 is formed in a substantially E shape.

Outer conductors 6 are provided on the upper, lower, left, right and rear surfaces of the outer surface of the dielectric block 1 excluding the front surface 1-a.
Therefore, a capacitance is formed between the region (open end) corresponding to the bottom of the inner conductors 10-1 and 10-2 and the outer conductor 6 on the rear outer surface facing each other. Furthermore,
Inner conductors 10-are formed on both sides of the dielectric block 1.
Input / output electrodes 4-1 and 4-for connecting to 1, 10-2
2 is provided, a hole is formed, and connection conductors 3-1 and 3-2 are formed on the inner surface of the hole.

The short-circuit connecting conductors 11-1, 11-
2 so that the short-circuit connection conductor 11-1 extends from the opening of the inner conductor 10-1 to the left side on the front surface 1-a of the dielectric block 1 so as not to be electromagnetically coupled (or coarsely coupled) to each other. Also, the short-circuit connection conductor 11-2 is formed to extend rightward from the opening of the inner conductor 10-2. The method for manufacturing the short-circuit connecting conductors 11-1 and 11-2 can be formed by forming a recess on the front surface 1-a to form a conductor on the entire front surface 1-a and then performing grinding or the like. Instead of forming the concave portion, the front surface 1-a may be formed by patterning or the like. The hatching shown in FIG. 1 indicates a portion where the conductor is not formed.

As shown in FIG. 3, the equivalent circuit of this dielectric filter has short-circuit connection lines 15-1 and 15-2, resonance lines 13-1 and 13-2, and termination capacitors 12-1 and 12-.
2 is a quarter-wavelength resonance circuit having short circuit connecting lines 15-1 and 15-2 and resonance lines 13-1 and 13-2, respectively, which are short circuit connecting conductors 11-1 and 11-2 shown in FIG. And the inner conductors 10-1 and 10-2. Then, each line impedance Z of the short-circuit connection lines 15-1 and 15-2
₁ is set to be larger than each line impedance Z ₂ of the resonance lines 13-1 and 13-2 (Z ₁ >> Z ₂ ), and the resonance lines 13-1 and 13-2 are electromagnetically coupled to each other as a BPF. Operate.

The operation will be described with reference to FIGS. 4 and 5. The vertical axis and the horizontal axis shown in FIG. 4 are the same as those in FIG. 12 described above, and FIG. 4A shows a distribution curve at the resonance frequency f ₀ . 4 (b) shows the distribution curve of the first attenuation pole (see FIG. 5) at the frequency ft ₁ , and FIG. 4 (c) shows the distribution curve of the second attenuation pole at the frequency ft ₂ . There is. Further, in the figure, reference numeral 12 is a terminating capacitance, reference numeral 13 is a resonance line,
Reference numeral 15 indicates a short-circuit connection line.

Since the structure of the dielectric filter according to this embodiment is also a quarter-wavelength resonance circuit as in the conventional example, the magnetic field distribution curve can be represented by a cosine wave curve having the short-circuit end 15a as the origin, and the electric field The distribution curve can be represented by a sine wave curve whose origin is the short-circuit end 15a. Further, a point c ′ in the figure is a position where the phase at the resonance frequency f ₀ including the portions shortened by the lines 13 and 15 and the terminating capacitance 12 becomes 90 degrees. That is, the electromagnetic field distribution at the fundamental frequency f _{0 where the} distance between the short-circuit end 15a and the point c ′ is λ / 4 is shown in FIG. 4 (a). However, in the case of the above configuration, although the lines 13 and 15 are provided, only the resonance line 13 (the illustrated coupling portion 13a and non-coupling portion 15b) is coupled,
The strength of the magnetic field and the electric field in the resonance line 13 is the strength of each curve in the resonance line 13. The shaded area a in the figure
Indicates the strength of the magnetic field, the area of the shaded portion b indicates the strength of the electric field, and FIG. 4A shows the case of magnetic field coupling <electric field coupling as an example.

Here, similarly to the above-mentioned conventional example, an attenuation pole occurs at a frequency at which the area of the shaded portion a (strength of the magnetic field) and the area of the shaded portion b (strength of the electric field) are equal. Figure 4
(B) shows that the point e where the phase becomes 90 degrees occurs near the point c'at the frequency where both are equal.
In this example, the point e is located longer than the point c ′, and the attenuation pole frequency ft ₁ is below the pass frequency band f ₀ . The frequency ft _{1 of the} attenuation pole is mainly the position of the non-coupling portion 15b,
That is, it is determined by the length of the short-circuit connection lines 15-1 and 15-2 (the size of Z ₁ ), and the short-circuit connection lines 15-1 and 15-2
If is shortened, the attenuation pole frequency ft ₁
Can be moved to the upper side of the pass frequency band f ₀ .

FIG. 4C shows that the frequency at which the area of the shaded area a and the area of the shaded area b are equal is also in the vicinity of 2f ₀ , and the position where the phase becomes 90 degrees is at the point f. There is. Since this point f is located in the vicinity of 1/2 of the point c ′, the frequency ft _{2 of the} attenuation pole occurs in the vicinity of 2f ₀ , and its frequency ft
₂ is mainly the position of the coupling portion 13a, that is, the resonance line 13-
It is determined by the length of 1 and 13-2 (size of Z ₂ ). Therefore, the above structure has the short-circuit connecting lines 15-1 and 15-2.
The condition is that is not bound.

Next, a second embodiment will be described with reference to FIG. In this embodiment, the short-circuit connection lines 15-1 and 15
-2 in order to shorten the connection line 17-1, 17-
The length of 2 is set to the short-circuit connection lines 11-1 and 1 of the first embodiment.
It is shorter than 1-2, and for this reason front 1-b
Outer conductors 6-1 and 6-2 are formed by cutting out both left and right ends of the.

In the third embodiment shown in FIG. 7, in order to reduce the degree of coupling between the short circuit connecting lines 15-1 and 15-2,
The short-circuit connection conductor 19-1 is formed downward from the opening of the inner conductor 18-1, and the short-circuit connection conductor 19-2 is formed upward from the opening of the inner conductor 18-2.

Further, in the fourth embodiment shown in FIG. 8, the short-circuit connecting conductors 21-1 and 21-2 are both inner conductors 2 respectively.
The outer conductor 6 is formed in parallel downward from the openings 0-1 and 20-2, but in order to reduce the degree of coupling between the short-circuit connecting conductors 21-1 and 21-2, the outer conductor 6 is connected to the short-circuit connecting conductor 21. -1
And 21-2 (front surface portion 6-3) are formed so as to wrap around, and the front surface portion 6-3 and the short-circuit connecting conductor 2 are formed.
The outer conductor 6 is not formed between 1-1 and 21-2 (illustrated 1-d and 1-e).

According to such a structure, the lengths of the short-circuit connection lines 15-1, 15-2, etc. (that is, the size of Z ₁ ) and the lengths of the resonance lines 13-1, 13-2, etc. (that is, Z ₁ ). Z ₂ ) can be arbitrarily combined to obtain the pass frequency f ₀
It is possible to change the frequencies ft ₁ and ft ₂ of the attenuation pole without changing. Therefore, for example, as shown in FIG. 5, it is possible to construct a BPF in which the frequency ft _{2 of the} attenuation pole is between 2f ₀ and 3f ₀ such that ft ₁ <f ₀ <2f ₀ <ft ₂ <3f _0. in the 2f ₀ the example shown in FIG. 5 -
At 30 dB and 3f ₀ , an attenuation amount of −28 dB can be realized. Further, since the attenuation pole can be generated below f ₀ , the local oscillation frequency or image frequency can be cut even when the local oscillation frequency or image frequency is lower than f ₀ .

[0027]

As described above, according to the present invention, by appropriately setting the length of the resonance line, that is, its impedance, and the length of the short-circuit connecting line, that is, its impedance, the lower and upper sides of the pass frequency can be obtained. Since it is possible to generate attenuation poles on both sides of and the desired amount of attenuation, it is possible to reliably block frequencies above and below the fundamental frequency, and to provide a bandpass characteristic that allows the fundamental frequency to pass. Can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view showing a dielectric filter according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the dielectric filter of FIG.

FIG. 3 is an equivalent circuit diagram of the dielectric filter of FIG.

4 is an explanatory diagram showing an example of an electric field distribution and a magnetic field distribution of the dielectric filter of FIG.

5 is an explanatory diagram showing an example of frequency characteristics of the dielectric filter of FIG.

FIG. 6 is a perspective view showing a dielectric filter according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing a dielectric filter according to a third embodiment of the present invention.

FIG. 8 is a perspective view showing a dielectric filter according to a fourth embodiment of the present invention.

FIG. 9 is a perspective view showing a structure of a conventional dielectric filter.

10 is a cross-sectional view showing the dielectric filter of FIG.

11 is an equivalent circuit diagram of the dielectric filter of FIG.

12 is an explanatory diagram showing an electric field distribution and a magnetic field distribution of the dielectric filter of FIG.

FIG. 13 is an explanatory diagram showing frequency characteristics of the dielectric filter of FIG.

[Explanation of symbols]

1 Dielectric block 6 Outer conductors 10-1, 10-2, 16-1, 16-2, 18-1,
18-2, 20-1, 20-1 Inner conductors 11-1, 11-2, 17-1, 17-2, 19-1.
19-2, 21-1, 21-2 Short-circuit connection conductors 12-1, 12-2 Termination capacitance 13-1, 13-2 Resonance line 15-1, 15-2 Short-circuit connection line

Claims (5)

(57) [Claims] 1. An outer conductor is provided on an outer surface other than one outer surface.
The formed dielectric block and the inside of the dielectric block
Are placed in a state of being electromagnetically coupled to each other.
A number of inner conductors and the plurality of inner conductors on the one outer surface
Short-circuit each one end of the conductor and the outer conductor
A plurality of short-circuit connection conductors, and the plurality of inner conductors
1 for each of the short-circuit connecting conductors connected to them
A quarter-wavelength resonance circuit is formed on the one outer surface.
The plurality of short-circuit connecting conductors are
Placed in a decoupling state that reduces the electromagnetic coupling of
A dielectric filter characterized in that 2. The dielectric block is the one outer surface.
An opening is provided on the one outer surface from the opening.
Multiple parallel bottomed holes that widen toward opposite outer surfaces
And the plurality of inner conductors are the plurality of inner conductors.
It is formed and arranged along the inner surface of parallel bottomed holes.
The dielectric filter according to claim 1, wherein: 3. Reduction in the plurality of short-circuit connecting conductors
The combined state is determined by the one end face of the dielectric block.
At each of the one ends of the plurality of inner conductors
The dielectric filter according to claim 1 , wherein the dielectric filters are arranged so as to extend in a direction in which they are spaced apart from each other . 4. Reduction in the plurality of short-circuit connecting conductors
The combined state is determined by the one end face of the dielectric block.
At each of the one ends of the plurality of inner conductors
In a recess that extends in the direction of
The dielectric filter according to claim 3, wherein the dielectric filter is arranged . 5. A reduction in the plurality of short-circuit connecting conductors
The combined state is determined by the one end face of the dielectric block.
At one end of each of the plurality of inner conductors
Extend in a direction that does not intersect the
The contract is characterized in that the arrangement is such that
The dielectric filter according to claim 1.