JP4114275B2 - Bandstop filter, duplexer and radio equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a band rejection filter, a duplexer, and a radio apparatus using the same, for example, used in a microwave band.
[0002]
[Prior art]
For example, in a base station in a mobile communication system, a transmission filter and a reception filter are provided between a transceiver and an antenna, but a band rejection filter is used as a reception filter in order to remove unnecessary band signals. It has been.
[0003]
As a high frequency filter that handles relatively high power and is required to be downsized, such as a high frequency filter for a base station, (1) As disclosed in Japanese Patent Laid-Open No. 5-48305, a TM mode dielectric A body resonator is used, and the dielectric resonator is multistaged in order to obtain a necessary damping characteristic in a desired band.
[0004]
Further, a band rejection filter which can be easily multistaged is disclosed in (2) Japanese Patent Laid-Open No. 10-322155.
[0005]
[Problems to be solved by the invention]
When a band-stop filter is configured by coupling a resonator to a predetermined portion of a transmission line, generally, as the number of stages of the resonator is increased, the coupling point of the resonator with respect to the transmission line increases. There is a problem that the number of parts for the entire structure increases and the size increases. In the filter of (1) using multimode dielectric resonators such as double mode and triple mode, it is possible to provide multistage resonators as a whole by using a small number of resonator units. Has a great effect. However, when the resonators of each mode of the multi-mode dielectric resonator are individually coupled to a predetermined location of the transmission line, means for coupling a plurality of resonators and the transmission line are provided in the same resonance space. There are physical limitations in arranging the coupling means, and there is a problem that it is difficult to obtain a stable resonance space. Therefore, the number of resonators that can be connected to the same part of the transmission line is limited. In addition, the number of coupling points between the transmission line and the resonator increases, so that there is a problem that the loss increases.
[0006]
An object of the present invention is to provide a band-rejecting filter, a duplexer, and a radio apparatus using them, in which resonators can be easily multistaged and low loss is achieved.
[0007]
[Means for Solving the Problems]
According to the present invention, a first resonator is coupled to a predetermined portion of a transmission line, and a second resonator is coupled to the first resonator to constitute a band rejection filter.
The present invention also uses a multi-mode dielectric resonator as the resonator, and uses the first mode resonator and the second mode resonator coupled to each other as the first and second resonators. .
Further, the present invention forms a duplexer by providing the band rejection filter in part. For example, a band-pass filter is connected to the band rejection filter having the above configuration to configure a reception filter, and a duplexer is configured by this and the transmission filter.
[0008]
Further, according to the present invention, the band rejection filter or duplexer is provided, for example, between an antenna and a transmission / reception circuit to constitute a radio apparatus.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
First, the configuration of the band rejection filter according to the first embodiment will be described with reference to FIG.
[0010]
FIG. 1 is an equivalent circuit diagram of a band rejection filter. In (A), L1 and L2 are transmission lines between the input port IN and the output port OUT. R1 is a first resonator and R2 is a second resonator. A connection point between the transmission lines L1 and L2 and the first resonator R1 are coupled via a coupling circuit K1. Further, the first resonator R1 and the second resonator R2 are coupled via a coupling circuit K2.
[0011]
A first resonator R1 second resonator R2 is for example the width x of each provided a single columnar dielectric into the cavity for instance TM ₁₁₀ mode (columnar dielectric, a depth y, the height z is a mode expressed as TMxyz). Then, the two dielectric columns are arranged in parallel, and the resonance modes generated in both are magnetically coupled to couple the resonators R1 and R2. That is, K2 is configured. Further, coaxial cables are used as the transmission lines L1 and L2, and a coupling loop that magnetically couples to the resonator R1 is provided in the cavity, and the central conductor of the coaxial cable is connected to one end of the coupling loop. This structure constitutes the coupling circuit K1.
[0012]
FIG. 1B shows an example in which a three-stage resonator is provided. Thus, by coupling the third resonator R3 to the second resonator R2, three resonators are equivalently coupled to the transmission line. Similarly, when three or more stages of resonators are provided, the resonators may be coupled sequentially. Even in this case, the first resonator R1 is the only resonator that is directly coupled to the transmission line.
[0013]
FIG. 2 is a diagram showing the pass characteristics of the band rejection filter shown in FIG. If the resonance frequencies of the resonators R1 and R2 shown in FIG. 1A are set to f1 and f2, respectively, and if these are equal, as shown in FIG. 2A, a large attenuation is obtained at the frequencies f1 and f2. It is obtained and can be used as a trap filter for trapping this frequency. Further, by making f1 and f2 different, as shown in FIG. 2B, it can be used as a band rejection filter that attenuates the band between them.
[0014]
Next, the configuration of the band rejection filter according to the second embodiment will be described with reference to FIGS.
FIG. 3 is an equivalent circuit diagram thereof. This band-rejecting filter is similar to that shown in FIG. 1 and is formed by coupling two resonators to be coupled to predetermined portions of the transmission line. That is, K1a, K2a. . . . Kna is a predetermined portion of the transmission line and resonators R1a, R2a. . . . This is a coupling circuit for coupling to Rna.
[0015]
When the wavelength on the transmission line is represented by λ, L1, L2,. . . . Ln−1 is a transmission line having a length corresponding to λ / 4. In this example, a plurality of resonators are coupled to the transmission line at intervals of λ / 4. Also, K1b, K2b. . . . Knb includes resonators R1a, R2a. . . . Rna and resonators R1b, R2b. . . . It is a coupling circuit between Rnb. In this way, one of the two resonators coupled to each other is coupled to the transmission line at an interval of λ / 4.
[0016]
FIG. 4 is a diagram illustrating an example of pass characteristics of the band rejection filter illustrated in FIG. 3. Here, an example is shown in which five sets (ten in total) of resonators are coupled to five nodes of the transmission line. When the resonance frequencies of the resonators R1a and R1b in FIG. 3 are f1a and f1b, the resonance frequencies of the resonators R2a and R2b are f2a and f2b, and similarly, the resonance frequencies of the resonators Rna and Rnb are expressed as fna and Rnb. When f1a = f1b, f2a = f2b, f3a = f3b, f4a = f4b, and f5a = f5b, the pass characteristics are as shown in FIG. In this way, a band rejection filter that greatly attenuates with a predetermined bandwidth is obtained.
[0017]
Further, if the resonance frequencies of the resonators shown in FIG. 3 are made different, pass characteristics as shown in FIG. 4B can be obtained. Since attenuation poles are generated by the number of resonators in this way, a large attenuation amount in a predetermined band can be ensured.
[0018]
Next, the configuration of the band rejection filter according to the third embodiment will be described with reference to FIGS.
FIG. 5 is a partially broken perspective view showing the structure of a TM dual mode dielectric resonator unit. In FIG. 5, 2 is a cavity made of dielectric ceramics, and an electrode film is formed on the outer surface thereof. Reference numeral 1 denotes an internal dielectric integrated with the cavity 2 in a state where the two columnar dielectrics 1a and 1b are orthogonal to each other. In the internal dielectric 1, a coupling groove 9 is formed at the intersection of the two columnar dielectrics 1a and 1b. Reference numerals 3 and 4 denote shield plates which cover the openings of the cavity 2, respectively, and an electrode film is formed on the inner or outer surface thereof. In FIG. 5, in order to clarify the shape of the internal dielectric 1, a part of the cavity 2 and a part of the shield plate 3 are broken, and the shield plate 4 is separated from the cavity 2. .
[0019]
In FIG. 5, reference numeral 5 denotes a coupling loop, which is connected between the connection body 6 and the junction box 7 and protrudes from the opening provided in the central portion of the shield plate 3 into the cavity. A semi-rigid coaxial cable 8 is connected to the junction box 7, and its central conductor is connected to the connection body 6.
[0020]
FIG. 6 is a plan view showing the relationship between the resonance mode of the TM dual-mode dielectric resonator unit and the coupling loop 5. In (A) of FIG. 6, a straight line indicated by the arrow is a columnar dielectric 1a, the electric lines of force TM ^X ₁₁₀ mode and the TM ^Y ₁₁₀ mode distributed in 1b. Because the coupling loop 5 is parallel to the direction of the electric field of the TM ^X ₁₁₀ mode, the magnetic field of the TM ^X ₁₁₀ mode TM ^X ₁₁₀ mode and magnetically coupled with interlinked to the loop plane.
[0021]
The arrows in FIGS. 6B and 6C indicate the electric lines of force in the even mode and the odd mode, which are coupled modes of the two modes. If if coupling grooves 9 are present, the TM ^X ₁₁₀ mode and the TM ^Y ₁₁₀ mode acts as two resonators independent. However, coupling grooves 9 columnar dielectric 1a, by providing to incise in the 45 ° direction in the intersection 1b, the resonance frequency of the even mode, occurs a difference in the resonance frequency of the odd mode, TM ^X ₁₁₀ mode and the TM ^Y ₁₁₀ mode are coupled.
[0022]
FIG. 7A is an equivalent circuit diagram of the band rejection filter shown in FIG. Here, Ra, Rb are TM ^X ₁₁₀ mode resonator and TM ^Y ₁₁₀ mode resonator shown in FIG. Kb indicates the coupling by the coupling groove 9. In FIG. 7A, Ka represents magnetic field coupling between the coupling loop connected to the transmission line and the resonator Ra. This band rejection filter can also be expressed as an equivalent circuit as shown in FIG. 1, and as in the case of the first embodiment, by appropriately determining the resonance frequencies of the two resonance modes, as shown in FIG. It can be used as a characteristic trap filter or a band rejection filter.
[0023]
FIG. 5 shows an example in which one TM dual-mode dielectric resonator unit is attached to the coaxial cable 8 serving as a transmission line via the junction box 7. However, the same applies at predetermined intervals of the transmission line at λ / 4 intervals. By attaching the TM dual-mode dielectric resonator unit, a band-stop filter can be configured. FIG. 7B is an equivalent circuit diagram thereof. Here, R1a and R1b are resonators according to the two resonance modes of the first TM dual mode dielectric resonator unit, and R2a and R2b are resonators according to the two resonance modes of the second TM dual mode dielectric resonator unit. , R3a, R3b are resonators having two resonance modes of the third TM dual mode dielectric resonator unit. The three TM dual mode dielectric resonator units are connected via transmission lines L1 and L2 having a length of λ / 4.
[0024]
Next, the configuration of the band rejection filter according to the fourth embodiment will be described with reference to FIGS.
FIG. 8 is a perspective view showing a configuration of a TM dual mode dielectric resonator unit connected to the transmission line 8. This unit is formed by forming electrodes on the outer surfaces (six sides) of a substantially cubic shaped dielectric block. This dielectric block is provided with a coupling hole 10 shown in the figure. Further, the outer coupling electrode 11 is formed on the upper surface in the figure separately from the electrode formed on almost the entire outer surface of the dielectric block. 8 is a coaxial cable as a transmission line, and a capacitor 12 is connected between the center conductor and the external coupling electrode 11.
[0025]
FIG. 9 shows an example of two resonance modes to be used and their coupling modes. (A), the straight line shown by the arrow is the electric lines of force TM ^X ₁₁₀ mode and the TM ^Y ₁₁₀ mode. For external coupling electrode 11 is perpendicular to the direction of the electric field of the TM ^Y ₁₁₀ mode, the external coupling electrode 11 is coupled with the TM ^Y ₁₁₀ mode.
[0026]
The arrows in FIGS. 9B and 9C indicate the electric lines of force in the even mode and the odd mode, which are coupled modes of the two modes. If the coupling holes 10 are present, the TM ^X ₁₁₀ mode and the TM ^Y ₁₁₀ mode acts as two resonators independent but, as shown in FIG., The resonance frequency of the even mode resonant frequency of the odd mode by providing the coupling hole 10 in bets on the difference occurs positions, and the TM ^X ₁₁₀ mode and the TM ^Y ₁₁₀ mode coupling.
[0027]
Such a dual-mode dielectric resonator unit is also coupled to a plurality of nodes at a predetermined interval with respect to the transmission line as in the case of the above-described embodiment, so that an equivalent circuit is shown in FIG. A band-stop filter as shown can be constructed.
[0028]
Next, the configuration of the filter according to the fifth embodiment will be described with reference to FIGS.
FIG. 10 is a block diagram of the entire filter. Here, BPF is a band pass filter that passes a predetermined frequency band, and BEF is a band rejection filter that attenuates a predetermined frequency or a predetermined frequency band. Thus, the band rejection filter BEF is connected between the transmission line to which the band pass filter BPF is connected and the ground. As the band rejection filter BEF, a double-mode dielectric resonator as shown in FIG. 5 or FIG. 8 is used, and the resonance frequency of each mode resonator is appropriately determined.
[0029]
FIG. 11 shows an example of the pass characteristic of the filter shown in FIG. (A) is the pass characteristic of the band-pass filter BPF alone, and (B) is the pass characteristic of the band-stop filter BEF alone. (C) is the overall pass characteristic. In this way, by setting the resonance frequencies f1 and f2 of the resonators in the dual mode near the boundary frequency from the pass band of the BPF to the cut-off area, as shown in FIG. Attenuation characteristics to the high band side and low band side cut-off areas can be made steep, respectively, and a large attenuation in the cut-off area adjacent to the pass band can be secured while suppressing insertion loss of the pass band.
[0030]
Next, configurations of a duplexer and a wireless device according to the sixth embodiment will be described with reference to FIG.
In FIG. 12, the duplexer includes a TX filter (transmission filter) and an RX filter (reception filter), and configures an antenna port ANT by phase-combining the output part of the TX filter and the input part of the RX filter. As shown in the figure, an antenna is connected to the antenna port ANT, a transmission circuit is connected to the input port Tx of the TX filter, and a reception circuit is connected to the output port Rx of the RX filter.
[0031]
The TX filter and the RX filter are the band rejection filters shown in the above embodiments or the band pass filters as shown in FIG.
[0032]
Thus, the base station radio apparatus in the mobile communication system is configured.
[0033]
【The invention's effect】
According to the first aspect of the present invention, a plurality of stages of resonators are coupled to the transmission line even though the number of resonators coupled to the transmission line is one. The loss at the coupling portion between the line and the resonator, which increases the number of points, does not increase. Even when three or more resonators are coupled to the same location on the transmission line, it is only necessary to sequentially couple other resonators to the second resonator, so that a predetermined number of resonators can be easily formed. Can be provided.
[0034]
In addition, the multimode dielectric resonator is used as a coupled two-stage resonator, and only one of the resonators is coupled to a predetermined part of the transmission line, so that the entire number of resonators can be increased. Reduction in the number of parts and miniaturization are facilitated.
[0035]
According to invention of Claim 2 , it can be used as a small-sized and low-loss duplexer.
[0036]
According to the third aspect of the present invention, it is possible to configure a small-sized wireless device with little power loss.
[Brief description of the drawings]
FIG. 1 is an equivalent circuit diagram of a band rejection filter according to the first embodiment. FIG. 2 is a pass characteristic diagram of the filter. FIG. 3 is an equivalent circuit diagram of a band rejection filter according to the second embodiment. 4 is a pass characteristic diagram of the filter. FIG. 5 is a partially broken perspective view of a band rejection filter according to a third embodiment. FIG. 6 is a graph showing distributions of electric lines of force in two resonance modes and a coupling mode in the filter. FIG. 7 is an equivalent circuit diagram of the filter. FIG. 8 is a perspective view of a band rejection filter according to the fourth embodiment. FIG. 9 is an electric diagram of two resonance modes used in the filter and their coupling modes. FIG. 10 is a block diagram of a filter according to a fifth embodiment. FIG. 11 is a pass characteristic diagram of the filter. FIG. 12 is a diagram of a duplexer and a radio apparatus according to the sixth embodiment. Block diagram showing configuration 【Explanation of symbols
1-Internal dielectric 2-Cavity 3, 4-Shield plate 5-Coupling loop 6-Connection 7-Junction box 8-Coaxial cable 9-Coupling groove 10-Coupling hole 11-Outer coupling electrode 12-Capacitor

Claims (3)

A transmission line; a first resonator coupled to a predetermined portion of the transmission line; and a second resonator coupled to the first resonator , wherein the first and second resonators are multimode. A band-rejecting filter characterized in that the first-mode resonator and the second-mode resonator coupled to each other of the dielectric resonator of FIG . A duplexer comprising the band rejection filter according to claim 1 in part. Wireless device comprising providing a duplexer according to a band elimination filter or claim 2 of claim 1.

Images