JPH0440701A - Phase adjustment method for dielectric filter - Google Patents

Abstract

PURPOSE:To attain the adjustment of phase of a dielectric filter without deteriorating the filter characteristic by connecting a coil between the earth and one of both input/output sides of a 1/4-wavelength type multistage dielectric resonator. CONSTITUTION:The inserting holes 28a and 28b are provided at the positions corresponding to the terminal pins 22 of a substrate 26, and a conductor rand 30 is formed through the upper and lower sides around the hole 28a. At the same time, a lead hole is formed toward the center of the substrate 26 together with another conductor rand 32 provided around the lead hole on the lower surface side of the substrate 26 respectively. Then both ends of a coil 34 are soldered to the rand 30 on the upper side and the rand 32 of the lower side respectively. Furthermore the pins 22 are soldered to the rand 32. Then grounding fitting 36 is fitted to the substrate 26 and soldered to the side face conductor film of a dielectric resonator 10 as well as to the rand 32. In such a constitution, the phase of a dielectric filter is simply adjusted by the inductance value of the connected coil.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dielectric filter mainly used in the microwave band. More specifically, the present invention relates to a technique in which an inductance is inserted between the input/output of a dielectric resonator and the ground, and the phase is arbitrarily changed depending on the value of the inductance.

INDUSTRIAL APPLICATION This invention can be utilized for the phase synthesis of the dielectric duplexer used, for example in the mobile radio|wireless apparatus of the simultaneous transmission and reception system, etc. in which a transmission frequency and a reception frequency differ.

[Prior art] As a dielectric filter, a plurality of resonator holes and coupler holes are provided alternately in the longitudinal direction of a rectangular parallelepiped dielectric block, and one of the open surfaces of the resonator holes and coupler holes is provided as an open surface. Some use a λ/4 type multistage dielectric coaxial resonator in which a conductor film is formed on the outer surface excluding the open surface and on the inner wall surface of the resonator hole.

Input/output coupling of the dielectric filter can be done by inserting coaxial resin terminals into the resonator holes located at both ends of the dielectric block, or
This is done by attaching a coupling capacitor to the open end.

In the case of a dielectric duplexer, dielectric filters such as those described above are designed to each have a predetermined resonance frequency, and are combined via a phase synthesis circuit.

[R1 that the invention attempts to solve! ] In the above dielectric filter, the phase is determined by the shape of the resonator, input/output structure, etc. This phase can be adjusted by changing the impedance by changing the input/output coupling capacitance, but this method also changes the impedance of elements other than the input/output resonant elements, which has the disadvantage of increasing the number of steps required to adjust the filter as a whole.

In the case of dielectric duplexers, this phase is particularly important, and appropriate phase synthesis must be performed between the dielectric filters on the transmitting and receiving sides, that is, from the coupling point to the center frequency of the receiving side, A complicated process is required to adjust, for example, the input/output coupling capacitance so that the impedance becomes almost infinite when looking at the filter and when looking at the receiving filter at the center frequency of the transmitting side.

It is an object of the present invention to provide a method that eliminates the drawbacks of the prior art as described above, allows the phase to be changed arbitrarily in an extremely simple manner without deteriorating the filter characteristics, and a dielectric filter using the method. The purpose of the present invention is to provide body filters and dielectric duplexers.

[Means for Solving the Problems] The present invention, which can achieve the above object, uses a 1/1 wavelength type multistage dielectric resonator, connects a coil between at least one of its input and output and the ground, This is a phase adjustment method for a dielectric filter in which the phase is adjusted by the inductance value.

In the case of a dielectric duplexer, a transmitter filter and a receiver filter with a dielectric resonator structure as described above are combined, and at least one of the input/output common coupling parts connecting the antenna terminals of both filters is connected to the ground. Connect the coil in between.

[Function] In the present invention, a coil is connected between the input/output of the dielectric filter and the ground. This means that an inductance is inserted in parallel with the dielectric filter. As the inductance value increases, the phase rotates clockwise on the Smith chart.

Therefore, by selecting an appropriate inductance value, the phase can be adjusted. In the case of a dielectric duplexer, phase synthesis is completed by connecting a coil with an appropriate inductance value and adjusting the phase, and simply connecting the transmitter and receiver filters with lead wires.

[Embodiment] FIG. 1 shows an exploded perspective view of an embodiment of a dielectric filter according to the present invention, and FIG. 2 shows an assembled vertical sectional view thereof. The basic configuration of the dielectric resonator 10 may be the same as that of the prior art, and uses a substantially rectangular parallelepiped dielectric block 12 made of a sintered body of a high dielectric constant material for microwave use. Three resonator holes 14 are formed at intervals in the longitudinal direction of this dielectric block 12, and a connector hole 16 is provided between them.

Then, one of the surfaces where the resonator hole 14 is open is an open surface (
In the drawing, the conductor film is formed on the entire outer surface of the dielectric block 12 and the inner wall surface of the resonator hole 14, with the other being the short-circuiting surface and excluding the open surface (shaded portion in the drawing). The area with small dots represents the surface where the conductive film is provided, and the surface where there is no conductive film and the dielectric base is exposed.

Note that the conductive film may be a thin layer of conductive material formed by baking silver paste, for example.

The input/output coupling terminals 20 are inserted into the resonator holes at both ends of such a dielectric resonator 10. The input/output coupling terminal 20 has a structure in which a terminal pin 22 is inserted into a resin cylinder 24. This constitutes a dielectric filter.

The invention further incorporates a substrate 26, which includes:
Insertion holes 28a, 28 are provided at positions corresponding to the terminal pins 22.
b, and conductor lands 30 are provided on the upper and lower surfaces around one insertion hole 28a. Also, a lead hole is formed near the center,
Another conductive land 32 is provided around the lead hole on the bottom surface of the board. Then, both ends of the coil 34 are soldered to the conductor land 30 on the upper surface and the conductor land 32 on the lower surface. Solder the terminal pins to the conductor lands on the bottom side as well. Finally, the grounding fitting 36 is fitted and soldered to the side conductor film of the dielectric resonator 10 and also to the conductor land 32 on the bottom surface of the substrate.

FIG. 3 shows an equivalent circuit of the dielectric filter obtained in this manner. In the figure, each parallel circuit of capacitances C3 to C1 and inductances to L, equivalently represents each resonant element of the dielectric resonator. Capacitances C, , C3 are coupling capacitances due to connector holes, and capacitances Cb and Cq are input/output coupling capacitances due to input/output coupling terminals. And L is the coil 34
is the inductance due to In this way, in the present invention, the inductance L is inserted in parallel with the input and output of the dielectric filter.

Next, the relationship between coil connection and phase characteristics will be described. g
Three-stage receiving filter developed for 11-body demultiplexer (center frequency f, = 881.5 MHz, bandwidth Bw −
The phase at 849 MHz (the center frequency of the transmitting filter) was measured for 25 M) Iz). The results are shown in Table 1.

Table 1 Note that the inductance is a measured value at 10 MHz.

In this way, by changing the inductance value of the coil inserted in parallel with the input and output of the dielectric filter, the phase can be changed freely.

FIG. 4 shows another embodiment of the invention.

In the figure, the dielectric filter 10 itself is the same as that shown in FIG. However, it is drawn upside down. In other words, the input/output coupling terminal 20 is inserted into the resonator holes at both ends of the dielectric block 12 whose upper surface is open, and the terminal pin 22 of one of the input/output coupling terminals 20 is connected to the side conductor film of the dielectric block 12. The coil 34 is directly connected by soldering between the two ends. If the input/output coupling structure uses a coupling capacitor, the connection can be easily made in this manner.

FIG. 5 is an example of a dielectric duplexer according to the present invention. A transmitter filter Tx and a receiver filter Rx having a dielectric resonator structure as shown in FIGS. 1 and 2 are combined, and at least one of the input/output common coupling parts (in this example A coil 44 is connected between the receiving filter RX) and ground.

The transmitting side filter Tx and the receiving side filter Rx used in this embodiment have impedances close to infinity when looking at the transmitting side filter Tx from the input/output common coupling point at the center frequency of the receiving side, but the receiving side filter In Rx, this is a case where the transmission frequency deviates from the infinite impedance. Therefore, phase synthesis cannot be achieved by simply combining both filters. Therefore, a coil 44 with an appropriate inductance value is connected to the receiving side filter Rx to change the filter phase, and the transmission frequency is adjusted so that the impedance is infinitely large. do.

Although the embodiments of the present invention have been described above, the present invention is not limited to only such a configuration.The structure and number of stages of the dielectric resonator used can be changed as appropriate, and the input/output coupling structure can also be modified. A coupling capacitor or the like may be used, and coils may be provided for both input and output. As a dielectric duplexer, it can be applied not only to an antenna duplexer as described above, but also to a case where it is shared with a local filter (triplexer).

[Effects of the Invention] As described above, the present invention is configured such that the coil is connected between at least one of the input and output of the multistage dielectric resonator and the ground, so that the phase can be easily adjusted by the inductance value of the connected coil. Can be adjusted. At this time, the filter characteristics do not deteriorate, and the impedance of other resonant elements does not change, so adjustment of the filter as a whole is extremely easy.

Therefore, especially when applied to a dielectric duplexer, there is an effect that the phase combination of the transmitting side filter and the receiving side filter can be performed simply and quickly.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing one embodiment of a dielectric filter according to the present invention, FIG. 2 is a vertical sectional view after assembly, and FIG.
4 is a perspective view of another embodiment of the present invention, and FIG. 5 is an explanatory diagram of a dielectric duplexer according to the present invention. 10... Dielectric resonator, 12... Dielectric block,
14...Resonator hole, 16...Coupler hole, 20...
Human output coupling terminal, 26... board, 34. 44...Coil, 36...Grounding fitting.

Claims (3)

[Claims] 1. A dielectric filter using a 1/4 wavelength type multi-stage dielectric resonator, characterized in that a coil is connected between at least one of its input and output and the ground, and the phase is adjusted according to its inductance value. Dielectric filter phase adjustment method. 2. A dielectric filter using a 1/4 wavelength type multi-stage dielectric resonator, in which a coil is connected between at least one of its input and output and ground. 3. In a dielectric duplexer that combines a transmitting side filter and a receiving side filter having a 1/4 wavelength type multi-stage dielectric resonator structure, at least one of the input/output common coupling parts connecting the antenna terminals of both filters and A dielectric duplexer with a coil connected between it and ground.