KR100313717B1 - Band Pass Filter of Dielectric Resonator Type Having Symmetrically Upper and Lower Notch Points - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric resonator type band pass filter having symmetric attenuation pole characteristics used in band pass filters and channel combiners in mobile communication or wireless communication base stations and repeater systems using high frequency.

According to an embodiment of the present invention, dielectrics are floated in input means for inputting a microwave input signal into a first metal cavity by a first loop coupling, and a second metal cavity connected in series through the first metal cavity and a window. First and second dielectric resonators forming a band pass filter for an input signal, and an output in which a frequency signal of a predetermined band is induced by electromagnetic induction coupling of the output frequency signal of the second metal cavity to a second loop coupling Means and both ends are electromagnetically inductively coupled to the first and second loop couplings to bypass a portion of the input signal to the output means so that the lower and upper attenuations are symmetrical to both ends of the band pass frequency output to the output means. And bypass means for forming the pole.

Description

Band pass filter of dielectric resonator type having symmetrically upper and lower notch points

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric resonator type band pass filter having symmetric attenuation pole characteristics, and more particularly, to a band pass filter or channel combiner used in a mobile communication or wireless communication base station and repeater system using high frequency. A dielectric resonator band pass filter having symmetric attenuation pole characteristics.

In general, since the 1930s, when Richtmyer proved that suitable shaped dielectric materials can be used as electro-magnetic resonators, in recent years they have been small, light, and high Q-factors. Has been developed for temperature stable dielectric materials have been applied to many fields.

Such dielectric resonators operate in almost all fields using high frequency (GHz band) radio waves such as mobile communication, satellite broadcasting, and broadband wireless communication networks (WLANs).

The resonator using such a dielectric is classified into a bulk type (bulk type) and a thin film type by dividing the shape of the dielectric. The present invention relates to a resonator using a bulk type dielectric.

On the other hand, a band pass filter (BPF) using a dielectric resonator combines dielectrics having different resonance and anti-resonant points, and uses components of the impedance of the combined dielectrics, for example, when the impedance is high, The frequency does not pass through and disappears, and the frequency of the low impedance band passes through.

In other words, a filter means passing only a specific frequency range among high frequencies (or low frequencies) or passing only a higher or lower frequency than a certain frequency. In the parts other than the required frequency band, the resistance is high so that the frequency is selectively passed through a method that does not pass the signal.

A band pass filter is a passive element having only a characteristic of passing only a frequency signal of a specific band and attenuating the remaining frequency signals, and it is essential to have excellent attenuation characteristics in the stop bands of the upper and lower parts of the pass band.

The band pass filter may be implemented as, for example, a circuit in which the series circuit and the parallel circuit of the inductor (L) and the capacitor (C) are connected in multiple stages, and in the case of the most common frequency band, a lumped element type using a common element is used. Will be used.

However, dielectric resonator type band pass filter products have been proposed in which a concentrated element type element cannot be used at a high frequency, particularly in the microwave band, and the dielectric is floated in the cavity of the metal.

On the other hand, the transmission or reception band pass filter used for the front end and the rear end of the antenna in the base station and repeater of various mobile communication and wireless communication system requires very low insertion loss characteristics and a rapid attenuation characteristic in the stop band.

In order to satisfy the bandpass filter specification for the base station and repeater, a bandpass filter using a dielectric resonator is used, and in this case, implementation of an attenuation pole in the stop band of the filter is very important.

On the other hand, the combiner (combiner) is a device that combines a plurality of channels to be transmitted in a communication system using a plurality of transmission channels into one, due to the increase in wireless communication capacity due to the increase in base station installation cost, wireless communication capacity increase The necessity is increased due to problems such as deterioration of radio wave quality, generation of unnecessary signals due to interference between channels, and degradation of call quality due to mutual interference between antennas.

The effect of using the combiner is to reduce unnecessary signals caused by interference between channels when using multiple channels, thus improving call quality, reducing the number of channel services in a narrow tower, and reducing mutual interference between antennas. Providing, filtering effect of a single channel. In addition, when the combiner is used, the number of antennas can be greatly reduced, thereby increasing space utilization.

The types of combiners having these functions and their advantages and disadvantages are as follows.

Conventional combiners include hybrid combiners having the advantages of narrow channel spacing and high loss; BALANCED PASS COMBINER, which has a small loss but poor utility in narrow channel spacing; BALANCED NOTCH COMBINER, which has a small loss but poor utility in narrow channel spacing; COMMUTATING LINE COMBINER, which is small in size but limited in channel spacing; There are low cost, small channel spacing, and small CAVITY-FERRITE COMBINER.

Meanwhile, a duplexer, which is used after an antenna in a base station and a repeater in a mobile communication and wireless communication system, filters a transmitted and received signal into a set frequency band range and supplies it to a system or an antenna, such as a band pass filter, with very little insertion. Loss characteristics and abrupt attenuation in the stopband are required.

In order to satisfy the duplexer specifications for base stations and repeaters, a duplexer using a dielectric resonator is used like a band pass filter. In this case, implementation of an attenuation pole in the stop band of the duplexer is very important.

A conventional dielectric resonator type band pass filter used in a band pass filter, a duplexer, a combiner, and the like will be described with reference to FIGS. 10 and 11.

The conventional three pole type band pass filter shown in FIG. 10 forms three cube cavities 2 to 4 inside a body 1 of a rectangular aluminum metal, and each cavity 2 to 4. The dielectrics 5-7 having three high load-free quality coefficients are floated by the support for dielectric support, and windows 10 and 11 are formed between the cavity 2-4, and the body ( Input and output connectors 8 and 9 are attached to both walls of 1).

The bandpass filter is used as a channel filter and uses an expensive dielectric resonator with a large no-load quality factor for low loss characteristics, and three or more dielectric resonators are used to realize an appropriate attenuation in the channel band. As a result, the overall size of the channel filter is increased.

In the conventional dielectric resonator type channel filter, as shown in FIG. 10, no attenuation poles are formed at both ends of the pass band, so that channel coupling is not easy when used as a combiner. There was this.

Therefore, conventionally, in order to solve such a problem, the number of resonators must be increased, so that the size of the filter increases, and as a result, the loss increases with the increase of the dielectric, thereby deteriorating the noise characteristics.

Accordingly, the present invention has been made in view of the problems of the prior art, and an object thereof is to provide symmetric attenuation pole characteristics at both ends of a pass band of a band pass filter of a GHz band used in various mobile communication and wireless communication base stations or repeater systems. The present invention provides a dielectric resonator band pass filter having a symmetric attenuation pole characteristic having excellent attenuation characteristics for an adjacent channel.

Another object of the present invention is to provide a channel combiner that facilitates channel combining by using a band pass filter in which attenuation poles are formed symmetrically at both ends of the pass band.

1 is an exploded perspective view showing the structure of a dielectric resonator type band pass filter according to the present invention;

2 is an assembly view showing a partial assembly state of the band pass filter shown in FIG.

3A and 3B are partially cutaway cross-sectional views of the assembled band pass filter according to the present invention, and the A-A cross-sectional view of Fig. 3A, respectively;

4 is an equivalent circuit diagram of the band pass filter shown in FIG.

5 is a graph showing the frequency characteristics of the dielectric resonator type band pass filter according to the present invention;

6 is an equivalent circuit diagram of a trielectric resonator type band pass filter according to the present invention;

7 is a graph showing the frequency characteristics of the three dielectric resonator type band pass filter according to the present invention;

8a to 8c is a block circuit diagram when a two-channel combiner is configured using a band pass filter according to the present invention, a graph showing the frequency characteristics of the first and second channels,

9 is a cross-sectional view of a conventional three dielectric resonator type band pass filter,

10 is a graph showing the frequency characteristics of a conventional three dielectric resonator type band pass filter.

Explanation of symbols on the main parts of the drawings

20, 21: dielectric resonator 22: nut

23,23a: tuning screw 24: fixing bolt

25: both nuts 26: support bolt

27: coaxial cable 28: left end core wire

29: right end core wire 30: input connector

31: first coupling copper plate 35: output connector

36: second coupling copper plate 40: body

41: first cavity 42: second cavity

43: window 44: the first connector accommodating groove

45: second connector receiving groove 46: cover

47: coaxial cable receiving groove 48: housing groove cover

50,60: first and second dielectric resonators 51,61: parallel resonant circuit

70: channel combiner 71,72: first and second channel filters

73: junction 74: antenna

In order to achieve the above object, the present invention provides a metal body and cover for forming the first and second metal cavities interconnected through the window, and to input a microwave input signal into the first metal cavity. First and second dielectric resonators each having an input terminal, a dielectric floating in the first and second metal cavities to form a band pass filter for the input signal, and a first dielectric resonator coupled to the input terminal to couple the input signal. A first coupling means for electromagnetically inductively coupling to the second coupling means for electromagnetically inductively coupling the output frequency signal of the second metal cavity, one side being electromagnetically inductively coupled with the first coupling means, and the other Electromagnetic inductively coupled to two coupling means to bypass the first and second dielectric resonators to bypass a portion of the input signal to the second coupling means. A dielectric resonator having a symmetric attenuation pole characteristic comprising a bypass means for turning on, and an output terminal for supporting the second coupling means and outputting a frequency signal of a set band induced in the second coupling means. Provides a band pass filter.

The invention further comprises coupling coefficient adjusting means for adjusting the coupling coefficient between the first and second dielectric resonators to adjust the bandwidth of the band pass filter in the window between the first and second metal cavities.

The bypass means is made of a coaxial cable, and both cores of the coaxial cable are electromagnetically inductively coupled to the first and second coupling means at a predetermined distance.

The first and second coupling means may each have a loop coupling structure having a predetermined spacing with opposing opposite side wall bodies, and the bypass means may include a coaxial cable embedded in the cover and the coaxial cable. It is composed of both cores extending and inserted between the opposing opposing side wall bodies and the loop coupling.

According to another feature of the present invention, the present invention provides an input means for inputting a microwave input signal into a first metal cavity by a first loop coupling, and a second connected in series through the first metal cavity and a window. First and second dielectric resonators each having a dielectric floating in the metal cavity to form a band pass filter for an input signal, and an output frequency signal of the second metal cavity is induced by electromagnetic induction coupling to a second loop coupling. Output means for outputting a frequency signal of a band, and both ends of the band pass frequency, which are inductively coupled to the first and second loop couplings, respectively, to bypass a part of the input signal to the output means and output to the output means. A symmetric attenuation pole, characterized in that it is composed of bypass means for forming a lower and upper attenuation pole symmetric to each other in the A dielectric resonator type band pass filter is provided.

Furthermore, the present invention may further include a third dielectric resonator installed in a third metal cavity formed between the first and second metal cavities to form a band pass filter together with the first and second dielectric resonators.

The band pass filter of the present invention may be used as a channel filter for outputting only a specific channel frequency signal, and may be used as a channel combiner by setting different pass band frequencies of the channel filters and connecting their output terminals in parallel. Can be.

As described above, the channel combiner using the dielectric resonator type band pass filter and the band pass filter of the present invention has better attenuation characteristics at adjacent channel frequencies than the conventional dielectric resonator type band pass filter and channel combiner. The size of the pass filter is remarkably small, and only two dielectric resonators can be used to form an attenuation pole having almost perfect symmetry, so that the loss is small and the cost can be realized.

(Example)

Hereinafter, with reference to the accompanying drawings showing a preferred embodiment of the present invention described above in more detail.

1 is an exploded perspective view showing a structure of a dielectric resonator type band pass filter according to the present invention, FIG. 2 is an assembled view showing a partially assembled state of the band pass filter shown in FIG. 1, and FIGS. 3A and 3B are respectively A partially cutaway cross-sectional view of the assembled band pass filter according to the present invention and the AA line cross-sectional view of FIG. 3A, FIG. 4 is an equivalent circuit diagram of the band pass filter shown in FIG. 1, FIG. 5 is a dielectric resonator type band pass filter according to the present invention. Is a graph showing the frequency characteristics.

As shown in FIGS. 1 to 3B, the dielectric resonator type band pass filter according to an exemplary embodiment of the present invention is a two-pole type band pass filter, and has two inside rectangular aluminum (Al) or duralumin metals. A body 40 having first and second cavities 41 and 42 in the form of a cube, each of the first and second dielectrics 20 having two high load-free quality factors in each cavity 41 and 42. , 21, is floated by a dielectric support support to form two first and second dielectric resonators 50,60.

Each dielectric resonator 50, 60 is a dielectric having a low loss of dielectric constant such as Teflon, PE, or rexolator, using a metal support bolt 26 made of aluminum or the like on the bottom surface of the body 40. A dielectric fixing bolt 24 made of a low dielectric constant material having the same low dielectric constant as the both nuts 25 with both the nuts 25 fixed thereto and the dielectrics 20 and 21 positioned on the upper ends of the nuts 25. The dielectrics 20 and 21 are floated in the center of the first and second cavities 41 and 42 by penetrating through the dielectrics 20 and 21 to both nuts 25 using. In addition, a window 43 for transmitting a resonance signal of the first dielectric resonator 50 to the second dielectric resonator 60 is formed between the adjacent cavity and the cavity.

In addition, the cover 46 coupled to the upper portion of the body 40 is made of brass or invar at a position opposite to the dielectrics 20 and 21, and the nut 22 is provided with a tuning screw 23 having a distal end thereof having a disk shape. ), And tune using the tuning screw 23 when tuning the resonance frequency.

In addition, both side surfaces of the body 40 are provided with first and second connector accommodating grooves 44 and 45 to which the input and output connectors 30 and 35, which are signal input / output terminals, are mounted. The input and output connectors 30 and 35 are N (F) -B / H type connectors.

First and second coupling copper plates used for electromagnetic field coupling toward the dielectrics 20 and 21 in the input and output connectors 30 and 35 mounted in the first and second connector accommodation grooves 44 and 45, respectively. (31, 36) are connected. Here, as shown in the cross-sectional view of FIG. 3B, the first and second coupling copper plates 31 and 36 have a first coupling copper plate 31 of the input connector 30 on the left side (or right side). And the second coupling copper plate 36 of the output connector 35 is attached to the right side (or the left side) at an angle of 30 °.

The first and second coupling copper plates 31 and 36 are usually of a plate type, but may be in the form of rods in some cases.

The cover 46 coupled to the upper portion of the body 40 has a coaxial cable receiving groove 47 in which a coaxial cable 27 is embedded, and the coaxial cable receiving groove 47 has a coaxial cable 27. ) Is accommodated and covered with the receiving groove cover 48.

The left end core 28 of one end of the coaxial cable 27 is in contact with the first coupling copper plate 31 connected to the input connector 30 at a predetermined distance, and the right end core 29 of the other end thereof is the output. The second coupling copper plate 36 of the connector 35 is contacted at a predetermined distance to bypass the high frequency input signal input through the input connector 30 to the output connector 35.

As shown in FIG. 4, the equivalent circuit of the two-pole type band pass filter includes the parallel resonant circuits of the inductors L1 and L2 and the capacitors C4 and C5, respectively. 51 and 61, a coupling capacitor C2 by the window 43 is connected between the parallel resonant circuits 51 and 61, and an input / output connector between the input / output stage and the resonant circuits 51 and 61. Capacitors C1 and C3 by 30 and 35 are connected.

In the equivalent circuit, the bypass coaxial cable 27 may be represented as an inductor Lr connecting the input terminal and the output terminal. Thus, the equivalent circuit of the two pole type band pass filter according to the present invention is represented as a two stage parallel resonant circuit having a bypass circuit between input / output.

The dielectric resonator type band pass filter having the symmetric attenuation pole characteristics according to the present invention configured as described above operates as follows.

First, the pair of dielectric resonators 50 and 60 form a band pass filter of a desired bandwidth by appropriately adjusting the coupling coefficient between the resonators.

In the present invention, when the input signal is applied to the first dielectric resonator 50 formed in the first cavity 41 through the first coupling copper plate 31 of the input connector 30, the high frequency input signal to be input is the first dielectric After being incident to the resonator 50 to firstly resonate, it is incident through the window 43 to the second dielectric resonator 60 of the second cavity 42 in which the second dielectric 21 is installed to perform secondary resonance.

At this time, if the coupling coefficient between the resonators 50 and 60 is adjusted by adjusting the tuning screw 23a installed in the window 43, the second coupling copper plate 36 having a band pass signal having a desired bandwidth connected to the output connector 35 is provided. ) Is obtained by electromagnetic field induction.

In this case, the core wires 28 and 29 at both ends of the input and output connectors 30 and 35 at a predetermined distance from the first and second coupling copper plates 31 and 36 having a loop coupling structure. In this contacting coaxial cable 27, a part of the input signal is bypassed without passing through the first and second dielectric resonators 50 and 60 through electromagnetic induction coupling, and a second coupling copper plate connected to the output connector 35 ( 36, which is mixed with the band pass signal passing through the first and second dielectric resonators 50 and 60, in the process of greatly attenuating the frequencies of the adjacent channels.

Through this process, the output signal obtained at the output of the band pass filter of the present invention has the attenuation poles UNP1 and LNP1 having almost complete symmetry and rapid attenuation in the upper and lower stop bands of the pass band as shown in FIG. 5. Formed to achieve good bandpass filtering.

In the present invention, as shown in Fig. 5, -19.336 dB is attenuated at mark 1 (1.790 GHz), but -4.5579 dB is attenuated at mark 1 (1.967 GHz) as in Fig. 10. It can be seen that the abrupt attenuation is significantly superior to that in comparison.

In addition, since the frequency characteristic curve described above is small in number of dielectric resonators, the insertion loss in the pass band is also improved. That is, although the insertion loss was -1.1423 dB in the related art, in the case of the present invention, the insertion loss was -0.5829 dB in the case of the present invention, and the insertion loss was less than in the case of the present invention.

The position of the attenuation poles formed at both ends of the pass band is determined by adjusting the distance between the cores 28 and 29 of the coaxial cable 27 and the corresponding dielectric. The closer to the dielectric, the attenuation poles UNP1 and LNP1. ) Position is close to the pass band.

Meanwhile, in the above-described embodiment, a two-pole bandpass filter using two dielectrics 20 and 21 has been described as an example, but in some cases, the first to third dielectric resonators connected in series using three dielectrics are formed. The core wires 28 and 29 at both ends of the bypass coaxial cable 27 may be formed by electromagnetic induction coupling to the coupling copper plates 31 and 36 of the input / output connectors 30 and 35.

The three-pole dielectric resonator having the bypass structure includes three parallel resonant circuits L1, C5; L2, C6; L3, and C7, four coupling capacitors C1 to C4, and a bypass inductor Lr as shown in FIG. A band pass filter having an equivalent circuit consisting of) is formed, and the frequency characteristics thereof are symmetrical attenuation poles (UNP2, LNP2) formed at both ends of the pass band, as shown in FIG. As a result, it has a pair of peak points in the center of the pass band.

Meanwhile, in the above embodiment, the case of using the band pass filter has been described. However, the dielectric resonator type band pass filter according to the present invention may be used as a channel filter.

Therefore, the present invention may be used in a channel combiner or a duplexer configured as a plurality of channel filters.

In other words, the channel combiner 70 illustrated in FIG. 8A sets the passband frequency of the bandpass filter configured as described above for each of the channels CH1 and CH2 so that the first and second channel filters 71 and 72 are different. After forming the circuit, two filters are connected in parallel at the junction 73 and output to the same output terminal, and when connected to an antenna 74 or a band pass filter for transmission, a plurality of channels are clearly distinguished and output for each channel. will be.

In general, the channel combiner is a parallel component of channel filters, as described above. The insertion loss and attenuation characteristics of the channel filter determine the combiner's performance. In the case of a PCS mobile communication base station, the channel bandwidth is 1.23 MHz. The channel spacing is 1.25 MHz, when combining channels at least one channel is combined.

When combining channels, the difference from the center of one channel (the center frequency of the pass band) to the adjacent channel band is 1.385 MHz, and the degree of attenuation at the center of the channel filter 1.385 MHz determines the smooth channel combining. It is an important factor.

Each channel filter is formed by using the dielectric resonator type band pass filter according to the present invention, and the channel combiner configured by using the two dielectric resonators minimizes the loss due to the number of resonators. The attenuation poles are formed symmetrically so that the attenuation at 1.385 MHz at the center of the channel filter is accurate and sufficient, thereby enabling easy channel combiner with two dielectric resonators.

The frequency characteristics of the channel combiner are clearly distinguished by attenuation poles of adjacent first and second channels CH1 and CH2 as shown in FIGS. 8B (first channel) and 8C (second channel). It can be seen that each channel is output as a frequency signal.

In the above embodiment, the band pass filter and the channel combiner have been described as an example, but the dielectric resonator type band pass filter having the symmetric attenuation characteristics according to the present invention can be applied to other microwave elements such as a duplexer. The present invention is also applicable to a case having a structure other than the dielectric floating structure of the illustrated embodiment.

As described above, the dielectric resonator type band pass filter and the channel combiner using the band filter have better attenuation characteristics at adjacent channel frequencies than the conventional dielectric resonator type band pass filter and channel combiner. The size of the pass filter is remarkably small, and since only two dielectric resonators can be used to form an attenuation pole having almost perfect symmetry, the insertion loss is small.

Furthermore, in the present invention, a sufficient amount of attenuation can be ensured at adjacent channel frequencies, so that the loss due to the resonator can be reduced, so that the dielectric resonator can be configured using a common dielectric with no load quality factor. As a result, the cost can be realized while improving the electrical characteristics of the product.

In the above, the present invention has been illustrated and described by way of specific preferred embodiments, but the present invention is not limited to the above-described embodiments, and the general knowledge in the technical field to which the present invention pertains falls within the scope of the present invention. Various changes and modifications will be possible by those who have the same.

Claims (9)

Metal bodies and covers, each cavity forming a first and a second metal cavity interconnected through a window; An input terminal for inputting a microwave input signal into the first metal cavity; First and second dielectric resonators each having a dielectric floating in the first and second metal cavities to form a band pass filter for an input signal; First coupling means coupled to the input terminal for inductively coupling an input signal to a first dielectric resonator; Second coupling means for electromagnetically inductively coupling an output frequency signal of the second metal cavity; One side is electromagnetically coupled to the first coupling means, and the other side is electromagnetically coupled to the second coupling means to bypass the first and second dielectric resonators to bypass a portion of the input signal to the second coupling means. Bypass means for And an output terminal for supporting said second coupling means and outputting a frequency signal of a set band induced in said second coupling means. 2. The apparatus of claim 1, further comprising coupling coefficient adjusting means for adjusting the coupling coefficient between the first and second dielectric resonators in the window between the first and second metal cavities to adjust the bandwidth of the band pass filter. A dielectric resonator bandpass filter having symmetric attenuation characteristics. The dielectric resonator band pass filter of claim 1, wherein the first and second coupling means are installed at a predetermined angle from left to right with respect to the input terminal and the output terminal, respectively. . The symmetric attenuating electrode according to claim 1, wherein the bypass means is made of a coaxial cable, and both cores of the coaxial cable are electromagnetically inductively coupled to the first and second coupling means at a predetermined distance. Dielectric resonator bandpass filter with characteristics. The method of claim 1, wherein the first and second coupling means are each formed of a loop coupling structure having a predetermined distance from the opposite side wall body, The bypass means comprises a coaxial cable embedded in the cover, and a dielectric having symmetric attenuation poles, characterized in that it is composed of both end cores extending from the coaxial cable and inserted between the opposite side wall bodies and the loop coupling. Resonator Bandpass Filter. The dielectric resonator band pass filter of claim 1, wherein the band pass filter is used as a channel filter for outputting only a specific channel frequency signal. The dielectric resonator bandpass filter of claim 1, wherein the passband frequencies of the channel filters are set differently, and their output terminals are connected in parallel to be used as channel combiners. . Input means for inputting a microwave input signal into the first metal cavity by a first loop coupling; First and second dielectric resonators each having a dielectric floating in the first metal cavity and a second metal cavity connected in series through a window to form a band pass filter for an input signal; Output means for outputting a frequency signal of a predetermined band induced by electromagnetic induction coupling of an output frequency signal of the second metal cavity to a second loop coupling; Both ends are electromagnetically coupled to the first and second loop couplings, respectively, to bypass a portion of the input signal to the output means to form lower and upper attenuation poles symmetrical to each other at both ends of the band pass frequency output to the output means. A dielectric resonator type band pass filter having a symmetric attenuation pole characteristic, characterized by comprising bypass means. 10. The method of claim 8, further comprising a third dielectric resonator disposed in a third metal cavity formed between the first and second metal cavities to form a band pass filter together with the first and second dielectric resonators. A dielectric resonator type band pass filter having a symmetric attenuation pole characteristic.