JP4184326B2 - filter - Google Patents

Description

  The present invention relates to a filter, and more particularly, to a filter that is effective for realizing a wide band while satisfying the demand for small size and low loss.

  A band-pass filter for attenuating unnecessary components such as harmonics is used in a high-frequency circuit unit such as a wireless communication device. As this type of band-pass filter, a filter is mainly used by using a dielectric resonator capable of obtaining a good attenuation characteristic with a small structure. In particular, as a resonator formed in a dielectric, a distributed constant type filter using a strip line is widely used.

As this type of the distributed constant type filter, that have been known techniques for example are described in the following patent documents.
Patent Document 1 this, by combining the lambda / 4 strip line and lambda / 2 strip-line, approach to configuring the band-pass filter or a band elimination filter is disclosed.
Japanese Patent Laid-Open No. 11-17405

  In recent years, as seen in UWB (Ultra Wide Band) systems, it is required for filters to have a wider bandwidth that has a specific bandwidth (pass bandwidth / center frequency) close to 100% or higher.

  However, in the conventional bandpass filter design method and the method disclosed in Patent Document 1 described above, in order to increase the passband, it is necessary to increase the number of resonators in multiple stages. As the number of steps increases, another problem arises, such as an increase in shape and an increase in insertion loss.

  In particular, when realizing an ultra-wide band like a UWB system, it is difficult to provide a small and low-loss filter with the conventional method because a required band cannot be obtained with a 2-3 stage resonator. Met.

  Therefore, the present invention provides a filter that is effective for realizing a wide band while satisfying the requirements of small size and low loss.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a filter in which a resonance electrode is disposed between a pair of GND electrodes to form a stripline structure, wherein the resonance electrode has a wavelength corresponding to a center frequency of a filter band. It has a stripline pattern having an electrical length that is ¼ of λ, and has a plurality of λ / 4 resonant electrodes that are short-circuited at one end to the GND electrode, and an electrical length that is ½ of the wavelength λ. It comprises a stripline pattern, and comprises λ / 2 striplines each connecting the other ends of the plurality of λ / 4 resonant electrodes .

  With this configuration, when the input signal passes through the λ / 2 stripline, the phase is rotated by 180 degrees, which acts in the same manner as interdigital gap coupling. As a result, a wide band equivalent to interdigital can be obtained even in the comb line type, and a wideband bandpass filter in the gigahertz band, which was difficult to realize by interdigital coupling, can be realized.

According to a second aspect of the present invention, there is provided a filter having a stripline structure in which a resonant electrode disposed between an input electrode and an output electrode is disposed between a pair of GND electrodes, wherein the resonant electrode has a filter band. A strip line pattern having an electrical length of ¼ of the wavelength λ corresponding to the center frequency, one end of which is short-circuited to the GND electrode, a plurality of λ / 4 resonance electrodes, and 1 / of the wavelength λ A stripline pattern having an electrical length of 2 and a λ / 2 stripline connecting between the other ends of the plurality of λ / 4 resonant electrodes, and the input electrode and the output electrode are λ / 4 It is characterized by comprising a strip line .

With this configuration, as in the first aspect of the invention , the phase rotates 180 degrees each time the signal input from the outside advances by λ / 2, and a λ / 4 resonator exists at this phase rotation position. Therefore, it works in the same way as interdigital, widens the bandwidth, and by configuring the input electrode and output electrode with λ / 4 strip lines, a more consistent state can be obtained. The characteristics are improved .

According to a third aspect of the present invention, there is provided a stripline structure in which a resonance electrode formed on the first dielectric layer is sandwiched between a pair of GND electrodes formed on the second and third dielectric layers. In the configured filter, the resonant electrode includes one strip line and a strip line pattern having an electrical length of ¼ of a wavelength λ corresponding to the center frequency of the filter band, and one end is short-circuited to the GND electrode. A plurality of single-shorted λ / 4 resonators, the other end of which is connected to the stripline, and the plurality of λ / 4 resonators are the length of the stripline existing between the λ / 4 resonators. The strip line is connected at each position where the length is λ / 2, and both ends of the strip line are connected to the input electrode and the output electrode, respectively .

According to a fourth aspect of the present invention, in the third aspect of the present invention, the input electrode and the output electrode are configured by λ / 4 strip lines .

  In this way, a strip line is arranged from the input electrode to the output electrode line, and a plurality of λ / 4 resonators are hung on the strip line, so that the transmission characteristic is good and the filter is small and has a wide bandwidth. Can be obtained.

  As described above, according to the present invention, it is possible to increase the bandwidth while satisfying the demand for small size and low loss.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments described below, and can be modified as appropriate.

  FIG. 1 is a perspective view showing an external structure of a filter according to this embodiment. As shown in the figure, this filter has an input external electrode terminal 102, an output external electrode terminal 104, and GND external electrode terminals 106 a and 106 b formed on the surface of a bulk dielectric 100, via these electrode terminals. Thus, it is provided with a structure connectable to a circuit board (not shown).

  2 is a cross-sectional view taken along the line A-A 'of FIG. As shown in the figure, this filter is configured by providing a plurality of inner layer electrodes in a dielectric 100 and arranging them in a predetermined relationship. This filter has a stripline structure in which the resonance electrode 22 is sandwiched between a pair of GND electrodes 20a and 20b. The resonance electrode 22 includes an input electrode 26 connected to the input external electrode terminal 102, and an output external electrode terminal. The output electrode 28 connected to 104 is connected.

  FIG. 3 is a plan view showing a configuration around the resonant electrode 22 shown in FIG. As shown in the figure, the resonance electrode 22 has a structure in which one end of each of the λ / 4 resonance electrodes 23a to 23c is connected to a transmission line composed of λ / 2 strip lines 24a and 24b every λ / 2. .

  Here, the λ / 4 resonance electrodes 23a to 23c are formed of a one-end short-circuited stripline pattern having an electrical length of ¼ of the wavelength λ corresponding to the center frequency of the filter band, and the λ / 2 stripline 24a and 24b is formed of a stripline pattern having an electrical length of ½ of the wavelength λ.

  An input electrode 26 is connected to the start end of the λ / 2 strip line 24a, and an output electrode 28 is connected to the end of the λ / 2 strip line 24b, thereby forming a transmission line from input to output. Is done. The input electrode 26 and the output electrode 28 connected to the λ / 2 strip lines 24a and 24b are formed of λ / 4 length strip lines. The connection between the input electrode 26 and the output electrode 28 and the λ / 2 strip lines 24a and 24b may be performed in a separate layer.

FIG. 4 is a first exploded plan view showing a layer structure of the filter shown in FIG. As shown in FIG. 5A, on the first dielectric layer 100-1, an input external electrode terminal 102, an output external electrode terminal 104, and GND external electrode terminals 106a and 106b are formed. Thus, the top surface of the filter is configured.

  In addition, as shown in FIG. 5B, the GND electrode 20a is formed on the second dielectric layer 100-2 in contact with the above-described GND external electrode terminals 106a and 106b. A dielectric layer 100-2 is disposed below the first dielectric layer 100-1 shown in FIG.

  FIG. 5 is a second exploded plan view showing the layer structure of the filter shown in FIG. As shown in the figure, λ / 4 resonance electrodes 23a to 23c, λ / 2 strip lines 24a and 24b, an input electrode 26 and an output electrode 28 are formed on the third dielectric layer 100-3. Then, the third dielectric layer 100-3 is disposed below the second dielectric layer 100-2 shown in FIG.

  FIG. 6 is a third exploded plan view showing the layer structure of the filter shown in FIG. As shown in FIG. 5A, a GND electrode 20b is formed on the fourth dielectric layer 100-4 in contact with the above-described GND external electrode terminals 106a and 106b. Layer 100-4 is disposed below the third dielectric layer 100-3 shown in the previous figure.

  Further, as shown in FIG. 5B, the input external electrode terminal 102, the output external electrode terminal 104, and the GND external electrode terminals 106a and 106b are formed on the fifth dielectric layer 100-5. These constitute the bottom surface of the filter. The fifth dielectric layer 100-5 is disposed below the fourth dielectric layer 100-4 shown in FIG.

  Each of the dielectric layers 100-1 to 100-5 described above is integrally formed through a lamination / firing process, and is completed as a multilayer filter including a plurality of dielectric layers. The external electrode terminals 102 to 106 are preferably formed by coating or plating after lamination and firing, and other intermediate layers are interposed between the dielectric layers 100-1 to 100-5 described above. May be.

  FIG. 7 is a circuit diagram showing an equivalent circuit of the filter shown in FIG. As shown in the figure, in this filter, three stages of λ / 4 resonators SLa [1] to SLa [3] are connected in a ladder shape by two λ / 2 strip lines SLb [1] and SLb [2]. It becomes the equivalent configuration. SLin and SLout shown in the figure are strip lines corresponding to the input electrode 26 and the output electrode 28 described above.

  As described above, the λ / 4 resonators SLa [1] to SLa [3] are arranged at positions where the phase is rotated by 180 degrees by the λ / 2 strip lines SLb [1] and SLb [2]. Can be widened.

  FIG. 8 is a characteristic diagram comparing the pass characteristics of the filter shown in FIG. 1 with a conventional filter. In the figure, the solid line indicated by reference numeral 501 indicates the characteristics of this filter, and the solid line indicated by reference numeral 502 indicates the characteristics of the conventional comb line type filter. As shown in the figure, the pass characteristic 501 of this filter sufficiently covers a wide band of 3 GHz to 9 GHz, and a wide band more than three times the conventional pass characteristic 502 was achieved.

  FIG. 9 is an equivalent circuit diagram showing an example in which the equivalent circuit shown in FIG. As shown in the figure, in the present invention, the basic unit of the λ / 4 resonator and the λ / 2 stripline may be multistaged. In that case, as shown in the figure, λ / 4 resonators SLa [1] to SLa [N] and λ / 2 strip lines SLb [1] to SLb [N−] are provided between the input terminal and the output terminal. 1] are connected in a ladder shape.

  According to the present invention, since it is possible to achieve a wide band with a small structure, application to a communication device such as a UWB system that requires an ultra wide band is expected.

It is a perspective view which shows the external appearance structure of the filter which concerns on this embodiment. It is sectional drawing which shows the A-A 'view of FIG. FIG. 3 is a plan view showing a configuration around a resonant electrode 22 shown in FIG. 2. FIG. 2 is a first exploded plan view showing a layer structure of the filter shown in FIG. 1. FIG. 3 is a second exploded plan view showing the layer structure of the filter shown in FIG. 1. FIG. 4 is a third exploded plan view showing a layer structure of the filter shown in FIG. 1. It is a circuit diagram which shows the equivalent circuit of the filter shown in FIG. FIG. 2 is a characteristic diagram comparing the pass characteristic of the filter shown in FIG. 1 with a conventional filter. FIG. 8 is an equivalent circuit diagram showing an example in which the equivalent circuit shown in FIG. 7 is multistaged.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Filter, 20 ... GND electrode, 22 ... Resonance electrode, 23 ... λ / 4 resonance electrode, 24 ... λ / 2 strip line, 26 ... Input electrode, 28 ... Output electrode, 30 ... Coupling electrode, 100 ... Dielectric, 102 ... Input external electrode terminal, 104 ... Output external electrode terminal, 106 ... GND external electrode terminal

Claims (4)

In a filter in which a resonance line is arranged between a pair of GND electrodes to form a stripline structure,
The resonant electrode is
A plurality of λ / 4 resonant electrodes of a single short-circuit type comprising a stripline pattern having an electrical length of ¼ of the wavelength λ corresponding to the center frequency of the filter band, one end of which is short-circuited to the GND electrode;
A λ / 2 stripline comprising a stripline pattern having an electrical length of ½ of the wavelength λ, and connecting between the other ends of the plurality of λ / 4 resonant electrodes;
The filter characterized by comprising . In a filter in which a resonance electrode arranged between an input electrode and an output electrode is arranged between a pair of GND electrodes to form a stripline structure,
The resonant electrode is
A plurality of λ / 4 resonant electrodes of a single short-circuit type comprising a stripline pattern having an electrical length of ¼ of the wavelength λ corresponding to the center frequency of the filter band, one end of which is short-circuited to the GND electrode;
A λ / 2 stripline comprising a stripline pattern having an electrical length of ½ of the wavelength λ, and connecting between the other ends of the plurality of λ / 4 resonant electrodes;
Comprising
The filter according to claim 1, wherein the input electrode and the output electrode are configured by λ / 4 strip lines . In the filter having a stripline structure in which the resonance electrode formed on the first dielectric layer is sandwiched between a pair of GND electrodes formed on the second and third dielectric layers,
The resonant electrode is
One stripline,
A strip line pattern having an electrical length of ¼ of the wavelength λ corresponding to the center frequency of the filter band, one end short-circuited to the GND electrode and the other end connected to the strip line λ / 4 resonator and
With
The plurality of λ / 4 resonators are:
Connected to each position where the length of the stripline existing between the λ / 4 resonators is λ / 2,
A filter characterized in that both ends of the strip line are respectively connected to an input electrode and an output electrode . 4. The filter according to claim 3, wherein the input electrode and the output electrode are constituted by λ / 4 strip lines .

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