KR20110093315A - Radio frequency filter with bypass path - Google Patents

Abstract

PURPOSE: A wireless frequency filter with a bypass path is provided to combine with a hybrid coupler filter, thereby providing a new kind of filter and reducing path loss of a signal. CONSTITUTION: A coupler(10) outputs an input signal to a second port and third port by being supplied the input signal from a first port. The input signal inputted from the second port and third port is composed according to a corresponding phase. The composed signal is outputted through a fourth port as an output signal of a wireless frequency filter or the first port. An input and output port of a filter part(30) is connected to the second and third port of the coupler. The filter part has a predetermined frequency filtering property. A first, and second switch part(21,22) is respectively formed in each connection path between the input and output port of the filter part and the second and third port of the coupler.

Description

RADIO FREQUENCY FILTER WITH BYPASS PATH}

The present invention relates to a radio frequency filter used in a wireless communication system, and more particularly to a radio frequency filter having a bypass path.

In general, a filter is an essential component in a radio frequency (RF) system for passing or stopping a specific frequency band. Types include, but are not limited to, BPF (Band Pass Filter), BRF (Band Rejection Filter), HPF (High Pass Filter), LPF (Low Pass Filter). These filters are designed and installed to meet the frequency pass or stop characteristics required by the RF system. Once installed, these filters are difficult to change unless they are replaced. For example, if the BRF needs to be reinstalled in an RF system in which the BPF is installed, the BPF should be removed and then replaced with the BRF. This has a problem in that communication loss and cost increase due to filter replacement.

An object of the present invention is to provide a radio frequency filter having a bypass path which minimizes signal loss.

Another object of the present invention is to provide a radio frequency filter capable of selecting one of two filters having different pass bands with minimal signal loss.

Another object of the present invention is to provide a radio frequency filter that reduces path loss.

Another object of the present invention is to provide a radio frequency filter for improving band edge characteristics.

Another object of the present invention is to provide a radio frequency filter capable of easily inverting signal characteristics.

Another object of the present invention is to provide a radio frequency filter that can easily design the notch characteristics.

In order to achieve the above object, the present invention, in the radio frequency filter having a bypass path, receives the input signal to the first port and distributes it to output to the second port and the third port, the second port and the third port A coupler for synthesizing the signals input through the three ports according to the corresponding phases and outputting them to the fourth port as an output signal of the first port or the radio frequency filter; A filter unit connected to each of the second and third ports of the coupler and an input / output port to have a predetermined frequency filtering characteristic; And a first switch and a second switch unit formed in each connection path between the second and third ports of the coupler and the input / output port of the filter unit to conduct or block the corresponding path according to an external switching control signal.

In the present invention, by providing a new type of filter in combination with a hybrid coupler and a filter, it is possible to reduce signal path loss, improve band edge characteristics, easily invert signal characteristics, and easily design notch characteristics. In addition, a hybrid coupler can be used to implement a path through which the processed signal can bypass the filter with minimal loss.

1 is a block diagram of a radio frequency filter having a bypass path according to an embodiment of the present invention.
FIG. 2 is a schematic perspective view of an essential part of an embodiment of the first and second switch parts of FIG. 1; FIG.
FIG. 3 is a schematic perspective view of a main part of another embodiment of the first and second switch parts of FIG. 1; FIG.
4 is a block diagram of a radio frequency filter having a bypass path according to another embodiment of the present invention.
5A and 5B are comparison signal waveform diagrams of a general filter and a filter according to embodiments of the present invention.
6A and 6B illustrate output waveforms of a filter according to embodiments of the present invention.
7 is a schematic perspective view of a filter unit according to still another embodiment of the present invention;
8 is a side view of FIG. 7

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, specific matters such as specific elements are shown, which are provided to help a more general understanding of the present invention. It is self-evident to those of ordinary knowledge in Esau.

In the present invention, a combination of a hybrid coupler (hybrid coupler) and a filter to change the original filter characteristics, so-called chameleon filter having a new characteristic will be described. That is, in the present invention, for example, the BPF and the hybrid coupler may be combined to form a chameleon BRF, and the LPF and the hybrid coupler may be combined to form a chameleon HPF. Of course, the reverse is also possible.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a block diagram of a radio frequency filter having a bypass path according to an embodiment of the present invention. Referring to FIG. 1, the chameleon filter according to the first embodiment of the present invention has a structure in which a 3 dB hybrid coupler 10 and a filter unit 30 are connected through first and second switch units 21 and 22. That is, the filter according to the present invention comprises a port 1 of the hybrid coupler 10 as an input terminal, a port 4 is configured as an output terminal, and a port 2 of the hybrid coupler unit 10 to the first switch unit 21. Port 1 of the filter unit 30 (for example, input port) through the port 3 of the hybrid coupler 10 through the second switch unit 22 through the number 2 of the filter unit 30 It has a structure connected to a port (for example, an output port). Here, the filter unit 30 may be implemented as various types of filters such as BPF, BRF, HPF, LPF. If the filter unit 120 is implemented as a BPF, the chameleon filter has a characteristic of BRF.

When both the first and second switch units 21 and 22 are in an on state, the characteristics of the filter unit 30 when the filter unit 30 is implemented as BPF will be described again with reference to FIGS. 5A and 5B. 5A illustrates waveforms of a signal S21 passing through a general BPF and a signal S11 returned. 5B illustrates a signal waveform of the chameleon filter of the present invention in which the hybrid coupler 10 and the filter unit 30 implemented with the BPF are coupled to the RF system. As shown in FIG. 5B, unlike in FIG. 5A, the phases of the pass signal S21 and the return signal S11 are inverted, the filter unit 120 is implemented as a BPF in the chameleon filter of the present invention. Appears to have

In more detail, in general, a hybrid coupler has a function of distributing one signal power, for example, to two or more signal powers having a phase difference of 90 degrees with each other. For example, in FIG. 1, when a signal is input to port 1 of the hybrid coupler 10, the signal is divided in half, and the signal is output to ports 2 (0 degrees) and 3 ports (-90 degrees) with a phase difference of 90 degrees. And provided to ports 1 and 2 of the filter unit 30. At this time, the signal of the pass band of the filter unit 30 passes through the filter unit 30 and is re-input to the ports on the other side of the hybrid coupler 10, that is, the ports 3 and 2, and these are caused by the phase difference. The synthesized signal is output to port 1 of the hybrid coupler 10 without a signal output to port 4 of the hybrid coupler 10. On the other hand, the signal outside the pass band of the filter unit 30 does not pass through the filter unit 30 and is returned from ports 1 and 2 of the filter unit 30 to be returned to ports 2 and 3 of the hybrid coupler 10, respectively. They are synthesized by phase difference and output to port 4.

In conclusion, in the entire filter structure of the present invention, the signal of the pass band of the filter unit 30 is again reflected to the input terminal among the signals input to the input terminal (port 1 side of the hybrid coupler), and is outside the pass band of the filter unit 30. It can be seen that the signal is output to the output terminal (port 4 side of the hybrid coupler) in the overall filter structure.

Such components that distribute / synthesize the signal power by the phase difference include hybrid ring, branch line directional coupler, 3 dB directional coupler, magic tea, etc., and when these components are used instead of the hybrid coupler 10 May further have a phase shifter to adjust the phase of the signal. For example, when using a magic tea instead of the hybrid coupler 110, a phase shifter is provided between the connection path between the second (or third) port of the magic tea and the filter unit to shift the pass signal by 90 degrees. Can be implemented.

The chameleon filter of the present invention, which can be implemented as described above, may be more useful when the whole is implemented in BRF, that is, in the case of 'hybrid coupler + BPF'. In other words, in case of general BRF, each resonator is designed by connecting 50 ohm line. This structure not only requires a relatively large size and a complicated structure, but also has good coupling of each resonant period. It is difficult to reject a wide frequency band above a certain level because it is not supported. In contrast, the chameleon filter of the present invention is relatively easy to implement and simply implements the BRF using a BPF structure that can process a wide frequency band can solve this problem. In addition, the chameleon filter of the present invention having such a structure can significantly reduce the path loss caused by increasing the total length of the 50 Ohm line as the number of resonators increases in the conventional BRF.

In addition, in order to implement the notch characteristic in a typical BRF, it is difficult to implement the notch characteristic because the length of the 50 ohm line has to be increased or shortened relative to the corresponding frequency, but the chameleon filter according to the present invention implements the notch characteristic in the BPF. Since the BPF is implemented as a whole, the notch characteristic of the BRF can be easily implemented and the skirt characteristic can be improved.

On the other hand, the chameleon filter according to the present invention, it is possible to implement the HPF structure as a whole using the LPF structure, in this case, it is possible to easily implement the HPF which is relatively difficult to manufacture.

In this configuration, the first and second switch units 21 and 22 installed between the hybrid coupler 10 and the filter unit 30 operate on / off by an external control signal Ctl to perform hybrid coupler operation. A signal path between the 10 and the filter unit 30 is blocked or conducted. In this case, when the first and second switch units 21 and 22 are in an on state, the input signal is provided to the filter unit 30 to undergo the filtering process as described above, but the first and second switch units 21 and When 22) is in the off state, the input signal is bypassed without being provided to the filter unit 30 and is output as it is.

In more detail, when the first and second switch units 21 and 22 are in an off state, the signal input through the first port of the hybrid coupler 10 has a phase difference of 90 degrees, and the signal power is halved. Each of them is distributed and output through ports 2 and 3, and are totally reflected by the first and second switch units 21 and 22, and are re-entered into ports 2 and 3, respectively. The re-inputted signals are synthesized by the phase difference between them and outputted to port 4.

As described above, when the first and second switch units 21 and 22 are in the off state, the input signal is output as it is without any signal processing, so that the filter according to the present invention bypasses the input signal without filtering the signal. It can be seen that it has further structure.

As described above, the filter according to the present invention having a bypass path may be suitable for use in a wireless communication system that does not require filtering processing in an initial use environment and then needs to perform filtering processing in a use environment.

For example, in a mobile communication base station system, it may be necessary to return some of used frequency bands for each service provider. For example, a specific service provider may use the 800 to 825 MHz band in the current year and then use only the 810 to 825 MHz band in the next year, that is, return the band from 800 MHz to 810 MHz before.

In such a case, the service provider should install a BRF that blocks the previous 800MHz to 810MHz band of all processed base stations or a BPF that passes only the 810 ~ 825MHz band. At this time, it is almost impossible to simultaneously perform the above filter installation work on all base stations installed nationwide. Therefore, the filter installation work is sequentially performed in advance on all base stations for a relatively long time (for example, six months) until the next year.

However, in this case, a problem occurs that the base station in which the above filter installation is performed in advance cannot serve the previous band from 800 MHz to 810 MHz even in the current year. In such a case, if the above-described filter of the present invention is applied, the signal can be bypassed even if the filter is installed in each base station in advance, so that all the serviceable bands can be used even in the current year. It can be solved. Then, when the next year arrives, the processing signal passes through the filter through the switching control of the filters installed in all the base stations, so that the service bands of all the base stations can be (almost) simultaneously changed to the 810-825 MHz band.

FIG. 2 is a schematic perspective view of an essential part of an embodiment of the first and second switch parts of FIG. 1. Referring to FIG. 2, the structures of the first and second switches 21 and 22 according to the exemplary embodiment of the present invention have a general contact switch structure, in which connection portions of terminals transmit signals by capacitance coupling. It can be seen that it has a non-contact switch structure. When implemented as a non-contact switch, it is possible to improve the Passive Inter Modulation Distortion (PIMD) characteristics, to prevent the loss of the switch signal, and to the spark generated in the contact switch structure, compared to the general touch switch. It is possible to reduce the possibility of damage due to the back.

Referring to FIG. 2, the structure of the first and second switches 21 and 22 according to an exemplary embodiment of the present invention will be described in more detail. First, a coupler connection is connected to two terminals, namely, a hybrid coupler, for input and output. Terminals and first and second terminal pins 201 and 202 connected to the filter connection terminal connected to the filter unit, respectively, and the first terminal pin 201 and the first terminal pin 202 are each formed in a plate shape. Is connected to the terminal members 211 and 212. In addition, at a position where capacitance coupling with at least one of the terminal members 211 and 212 is not made at least while having a portion capable of capacitance coupling with the terminal members 211 and 212 simultaneously, the terminal members ( 211 and 212 and the plate-shaped coupling member 220 comprised so that a movement to a position where capacitance coupling is made is provided. In addition, the motor 230 generating the driving force for the movement of the coupling member 220 by the switching control signal Ctl and the moving member for moving the coupling member 220 according to the driving force generated in the motor 230. An instrument structure 232 composed of various structures such as a gear is provided.

Through the above structure, the signal is transmitted or blocked in the capacitance coupling manner according to the moving position of the coupling member 220 between the first and second terminal pins 201 and 202, thereby turning on the overall switch. The on / off operation is performed.

In this case, the coupling member 220 should be floated in the air or shorted to the ground.

3 is a schematic perspective view of a main part of another embodiment of the first and second switch parts of FIG. 1. Referring to FIG. 3, the structure of the first and second switches 21 and 22 according to another embodiment of the present invention will be described in detail. The first terminal pin 201 connected to the hybrid coupler and the filter unit may be connected to each other. The second terminal pin 202 is connected to the terminal member 241, 242 of the cylindrical or cylindrical shape, respectively. In addition, the terminal member 241 and 242 may have a shape that surrounds the terminal member 211 and 212 and at the same time having a portion capable of capacitive coupling, at least one of the terminal members 211 and 212 and the capacitance. A cylindrical coupling member 250 configured to be movable to a position where capacitance coupling is performed with both the terminal members 211 and 212 in a position where no coupling is performed is provided. In addition, the motor 230 generating the driving force for the movement of the coupling member 250 by the switching control signal Ctl and the moving member for moving the coupling member 250 according to the driving force generated in the motor 230. Instrument structure 234 is provided.

Through the above structure, the signal is transmitted or blocked in the capacitance coupling manner according to the movement position of the coupling member 250 between the first and second terminal pins 201 and 202, thereby turning on / off the overall switch. Off operation is performed.

In this case, the coupling member 220 should be floated in the air or shorted to the ground.

4 is a block diagram of a radio frequency filter having a bypass path according to another embodiment of the present invention. Referring to FIG. 4, the chameleon filter according to the second embodiment of the present invention includes a hybrid coupler 10, first and second switch parts 21 and 22, and at least two identical filter parts, that is, a first filter. The unit 31 and the second filter unit 32 and a phase shifter 40 are included. That is, the filter according to the second embodiment of the present invention comprises the first port of the hybrid coupler 10 as an input terminal, the fourth port as an output terminal, the second switch of the hybrid coupler 10, the first switch Port 21 of the first filter unit 31 is connected to the port 1 (eg, an input port) through the unit 21, and the port 3 of the hybrid coupler 10 is connected to the second port through the second switch unit 22. It has a structure connected to the first port (for example, input port) of the filter unit 32. In addition, the second port (eg, the output port) of the first filter unit 31 is implemented in an open state, and the second port (eg, the output port) of the second filter unit 32 is a phase shifter ( 40) has a structure connected to one end. The other end of the phase shifter 40 is implemented in an open state.

In the above configuration, the operation when the first and second switch units 21 and 22 are in the mode on state, the signal input through the port 1 of the hybrid coupler 10 has a phase difference of 90 degrees, The signal power is divided by half and output through ports 2 and 3, and the signals of the pass bands of the filter parts are input to the first filter part 31 and the second filter part 32, respectively, and are outside the pass band. The signal is reflected. The first filter unit 31 and the second filter unit 32 may be configured with the same filter as described above, and may be implemented with various types of filters such as BPF, BRF, HPF, LPF.

Signals outside the pass band of the first and second filter units 31 and 32 are reflected by the first and second filter units 31 and 32, and are returned to ports 2 and 3 of the hybrid coupler 10. It is input, and is output through the port 4 of the hybrid coupler 10.

Meanwhile, since the phase shifter 40 is connected to the second port of the second filter unit 32, the phase shift amount of the signal of the pass band passing through the second filter unit 32 may be variably adjusted. Accordingly, the signal of the pass band of the second filter unit 32 is reflected at the open port of the phase shifter 40 while the phase shifted through the phase shifter 40, and then the second filter unit 32 is returned. The signal is re-input to the third port of the hybrid coupler 10, and the signal of the pass band of the first filter unit 31 is reflected by the open port of the second filter unit 32 and input again to the second port. As described above, the signals of which the phase shift amount is not adjusted (the signal input from the second filter unit side) and the variably adjusted signal (the one signal input from the second filter unit side) are ports 2 and 3 of the hybrid coupler 10, respectively. Since the phase difference between the two signals is not exactly 90 degrees when the signal is input through the signal, signals are distributed and output to both ports 1 and 4 of the hybrid coupler 10 according to the phase difference.

In conclusion, in the chameleon filter according to the third embodiment of the present invention illustrated in FIG. 4, a part of the passband signals of the first and second filter units 320 and 330 is adjusted by the phase shifter 40. It can be seen that the leakage to the port 4 of the hybrid coupler 10 according to the amount of variation. Thus, for example, when the first and second filter units 31 and 32 are implemented as BPFs, the entire chameleon filter operates as BRF, where the chameleon filter is adjusted by the amount of phase shift controlled by the phase shifter 340. The loss band (dB) of the cut-off signal is different. This type of filter can be applied to a system that needs to adjust the amount of cutoff of the signal in the cutoff band.

6A and 6B are diagrams illustrating output waveforms of a filter according to embodiments of the present invention, and FIG. 6A illustrates an example of a waveform of an output signal passing through a bypass or a filter unit when the filter of the present invention is implemented as a BPF. 6B illustrates an example of a waveform of an output signal passing through a bypass or a filter unit when the filter of the present invention is implemented as a BRF. As shown in FIGS. 6A and 6B, the filter according to the embodiments of the present invention may bypass or band pass / band stop a signal, and minimize signal loss in the signal passing through the bypass signal and the filter unit. Able to know.

7 is a schematic perspective view of a filter unit according to still another embodiment of the present invention. FIG. 8 is a side view of FIG. 7, and the filter unit 50 illustrated in FIGS. 7 and 8 is the present invention shown in FIG. 1. In the structure according to the first embodiment of the filter unit 30, or in the structure according to the second embodiment of the present invention shown in Figure 4 corresponding to each of the first filter unit 31 or the second filter unit 32 Can be. In addition, the filter unit 50 illustrated in FIG. 7 may replace filters generally applied to various devices.

In more detail, the filter unit 50 illustrated in FIG. 7 basically includes first and second filter units 51 and 52 having different filtering characteristics, that is, different pass bands or cutoff bands. It is implemented to select a filter having desired filtering characteristics among these first and second filter units 51 and 52 by an external control signal. In some cases, one of the first and second filter units 51 and 52 may be implemented as a BPF, and the other may be implemented as a BRF.

At this time, since the selection structure of the first and second filter parts 51 and 52 has a general contact switch structure, the connection part of the terminals has a non-contact switch structure in which signals are transmitted by capacitance coupling. First, first and second terminals 511 and 512, which are two terminals for input and output of the first filter unit 51, and first and second terminals for input and output of the second filter unit 52. The terminals 521 and 522 are each implemented in the form of a plate.

In addition, a first coupling member having a plate shape configured to be movable to a capacitance coupling position with a selected one of the first terminals 511 and 521 of the first and second filter units 51 and 52 ( 551 is provided, and similarly, a plate-shaped member configured to be movable to a position capable of capacitance coupling with a selected one of the first terminals 511 and 521 of the first and second filter units 51 and 52. Two coupling members 552 are provided.

On the other hand, the input terminal 1 of the filter unit 50 is implemented in the form of a plate and is always installed to enable capacitance coupling even when the first coupling member 551 is moved, and the output end of the filter unit 50 ( 2) is installed so as to allow capacitance coupling with the second coupling member 552 at all times.

In addition, the motor (not shown) generating driving force for the movement of the first and second coupling members 551 and 552 according to an external control signal and the first and second coupling member according to the driving force generated in the motor. There is provided an instrument structure (not shown) composed of various structures such as gears for moving the 551 and 552, wherein the first and second coupling members 551 and 552 are attached together to a single instrument structure, It can be implemented to be movable at the same time by the driving of a single motor.

As described above, the configuration and operation of the radio frequency filter according to the present invention can be made. Meanwhile, although the above description has been given of the embodiments of the present invention, there can be various modifications of the present invention. For example, the above-described BPF, BRF, or the like may be implemented as a frequency variable filter capable of varying the filtering band. In addition, there can be various modifications and changes of the present invention, and therefore, the scope of the present invention should be determined by the claims and the equivalents of the claims.

Claims (6)

In a radio frequency filter having a bypass path,
Receives an input signal through the first port and distributes it to the second port and the third port, and synthesizes the signal input through the second port and the third port according to the phase to the first port or the wireless A coupler outputting to the fourth port as an output signal of the frequency filter;
A filter unit connected to each of the second and third ports of the coupler and an input / output port to have a predetermined frequency filtering characteristic;
And a first switch and a second switch unit formed in each connection path between the second and third ports of the coupler and the input / output port of the filter unit to conduct or block the corresponding path according to an external switching control signal. Frequency filter.
In a radio frequency filter having a bypass path,
Receives an input signal through the first port and distributes it to the second port and the third port, and synthesizes the signal input through the second port and the third port according to the phase to the first port or the wireless A coupler outputting to the fourth port as an output signal of the frequency filter;
A first filter part having a predetermined frequency filtering characteristic in which one port is connected to the second port of the coupler and the other port is opened;
A second filter part connected to the third port of the coupler and having one port, and having the same frequency filtering characteristic as that of the first filter part;
A phase shifter having one end connected to the other port of the second filter part and the other end opened;
And a first switch and a second switch unit formed in each of the connection paths of the second and third ports of the coupler and the first and second filter units to conduct or block the corresponding path according to an external switching control signal. Radio frequency filter.
3. A radio frequency filter according to claim 1 or 2, wherein the coupler is a hybrid coupler.
The radio frequency filter as claimed in claim 1 or 2, wherein the first and second switch parts have a non-contact switch structure in which a connection portion of terminals transmits a signal by capacitance coupling.
The method of claim 4, wherein the first and second switch unit
First and second terminal pins;
First and second terminal members having a plate shape connected to the first and second terminal pins, respectively;
The first and second terminal members at a position where capacitance coupling is not performed with at least one of the first and second terminal members while having a portion capable of capacitive coupling at least simultaneously with the first and second terminal members. A plate-shaped coupling member configured to be movable to a position where both and capacitance coupling are made;
A motor generating a driving force for the movement of the coupling member by the switching control signal;
And a mechanism structure for moving said coupling member in accordance with a driving force generated in said motor.
The method of claim 4, wherein the first and second switch unit
First and second terminal pins;
First and second terminal members having a cylindrical or cylindrical shape connected to the first and second terminal pins, respectively;
Capacitive coupling with the at least one of the first and second terminal members, having a shape surrounding the first and second terminal members, and having a portion capable of capacitance coupling with at least the first and second terminal members. A cylindrical coupling member configured to be movable to a position where capacitance coupling with both the first and second terminal members is made at a non-positioned position;
A motor generating a driving force for movement of the coupling member by the switching control signal;
And a mechanism structure for moving said coupling member in accordance with a driving force generated in said motor.

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