Patent Publication Number: US-2021194107-A1

Title: T-junction with high isolation and method for fabricating the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of Korean Patent Application No. 10-2019-0173654, filed on Dec. 24, 2019, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     Example embodiments relate to a T-junction with high isolation and a method for fabricating the same. 
     2. Description of Related Art 
     A transmission array antenna requires a power divider, and a reception array antenna requires a power combiner. The power divider and the power combiner are the same in terms of shape, and are merely different from each other in terms of the return loss of respective ports or isolation requirements between the respective ports as necessary. The power divider and power combiner have a feature of radio waves thereof having directions opposite to each other. In the case of an active phased array antenna for reception, a beamforming module for controlling a phase and a magnitude of power is combined after each antenna element, followed by the power combiner. When a signal from the beamforming module is inputted to the power combiner, return loss needs to be low as well as it is necessary not to input the inputted signal back to the surrounding beamforming module. That is, isolation between respective input ports of the power combiner needs to be good. 
     SUMMARY 
     Aspects, which relate to a T-junction, provide a technology for improving isolation between individual ports while maintaining return loss of all ports by inserting a dielectric substrate on which a resistor is formed in a direction perpendicular to a plane of the power combiner/divider. 
     According to an aspect, there is provided a T-junction including a power divider/combiner configured to divide or combine power, a dielectric substrate disposed perpendicular to a lower plane of the power divider/combiner, and a dielectric holder configured to dispose the dielectric substrate. 
     The dielectric substrate may include a resistor formed on a portion of the substrate. 
     The dielectric holder may include a first dielectric holder and a second dielectric holder. 
     The first dielectric holder may include a plate, a first body positioned on a lower side of the plate to be in contact with a lower surface of the plate, the first body having a longitudinal direction, and a second body bent to extend from one side of the first body. 
     The first dielectric holder may include a substrate mount portion, the substrate mount portion having one surface formed to be recessed from a bent portion where the first body and the second body are connected. 
     The first dielectric holder may include a first stopper, the first stopper having one surface formed to protrude from the other side of the first body, and a second stopper, the second stopper having one surface formed to protrude from one side of the second body. 
     The second dielectric holder may include a first body having a longitudinal direction, and a second body bent to extend from one side of the first body. 
     The second dielectric holder may include a substrate mount portion, the substrate mount portion having one surface formed to be recessed from a bent portion where the first body and the second body are connected. 
     The second dielectric holder may include a first stopper insertion portion, the first stopper insertion portion having one surface formed to be recessed from the other side of the first body, and a second stopper insertion portion, the second stopper insertion portion having one surface formed to be recessed from one side of the second body. 
     The power divider/combiner may include a holder insertion portion positioned on an upper surface thereof, and the dielectric holder may be inserted into the holder insertion portion in a vertical direction. 
     According to another aspect, there is provided a dielectric holder including a plate, a substrate male holder including a first male holder body positioned on a lower side of the plate to be in contact with a lower surface of the plate, the first male holder body having a longitudinal direction, and a second male holder body bent to extend from one side of the first male holder body, and a substrate female holder including a first female holder body positioned on the lower plate of the plate to be in contact with the lower surface of the plate, the first female holder body having a longitudinal direction, and a second female holder body bent to extend from one side of the first female holder body. One surface of the male holder and one surface of the female holder may be in contact with each other, and a substrate insertion space into which a substrate is inserted may be formed therebetween. 
     The substrate male holder may further include a male substrate mount portion, the male substrate mount portion having one surface formed to be recessed from a bent portion where the first male holder body and the second male holder body are connected, and the substrate female holder may further include a female substrate mount portion, the female substrate mount portion having one surface formed to be recessed from a bent portion where the first female holder body and the second female holder body are connected so as to correspond to the male substrate mount portion. 
     The male substrate mount portion and the female substrate mount portion may fluidly communicate with each other to form a substrate insertion space. 
     The substrate male holder may include a first stopper, the first stopper having one surface formed to protrude from the other side of the first male holder body, and a second stopper, the second stopper having one surface formed to protrude from one side of the second male holder body. The substrate female holder may include a first stopper insertion portion, the first stopper insertion portion having one surface formed to be recessed from the other side of the first female holder body, and a second stopper insertion portion, the second stopper insertion portion having one surface formed to be recessed from one side of the second female holder body. 
     The first stopper and the second stopper may be respectively inserted into the first stopper insertion portion and the second stopper insertion portion. 
     Additional aspects of example embodiments will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects, features, and advantages of the invention will become apparent and more readily appreciated from the following description of example embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a diagram illustrating an example of a general T-junction constituting a power combiner/divider; 
         FIGS. 2A to 2C  are graphs illustrating insertion loss, return loss, and isolation of the T-junction illustrated in  FIG. 1 ; 
         FIG. 3  is a diagram illustrating a binary power combiner implemented through the T-junction illustrated in  FIG. 1 ; 
         FIGS. 4A to 4C  are diagrams illustrating an example of a conventional T-junction with improved isolation; 
         FIG. 5  is a diagram illustrating a T-junction according to an example embodiment; 
         FIGS. 6A to 6C  are graphs illustrating isolation of the T-junction illustrated in  FIG. 5 ; 
         FIG. 7  is a diagram illustrating a structure of the T-junction illustrated in  FIG. 5 ; 
         FIGS. 8A to 8C  are diagrams specifically illustrating a structure of the dielectric holder illustrated in  FIG. 7 ; 
         FIG. 9  is a diagram illustrating a method for assembling the dielectric holder and the combiner illustrated in  FIG. 7 ; 
         FIG. 10  is a diagram illustrating an assembled shape of the T-junction illustrated in  FIG. 7 ; and 
         FIG. 11  is a diagram illustrating a power combiner/divider implemented through the T-junction illustrated in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, example embodiments will be described in detail with reference to the accompanying drawings. The scope of the right, however, should not be construed as limited to the example embodiments set forth herein. Various modifications may be made to the example embodiments. Here, examples are not construed as limited to the example embodiments and should be understood to include all changes, equivalents, and replacements within the idea and the technical scope of the example embodiments. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood. that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used herein, specify the presence of stated features, integers, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, operations, elements, components, and/or groups thereof. 
     Although terms such as “first,” “second,” and “third” may be used herein to describe various members, components, regions, layers, or sections, these members, components, regions, layers, or sections are not to be limited by these terms. Rather, these terms are only used to distinguish one member, component, region, layer, or section from another member, component, region, layer, or section. Thus, a first member, component, region, layer, or section referred to in examples described herein may also be referred to as a second member, component, region, layer, or section without departing from the teachings of the examples. 
     Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those skilled in the art to which the example embodiments pertain. Terms, such as those defined in commonly used dictionaries, are to be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art, and are not to be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Regarding the reference numerals assigned to the components in the drawings, it should be noted that the same components will be designated by the same reference numerals, wherever possible, even though they are shown in different drawings. Also, in the description of example embodiments, detailed description of well-known related structures or functions will be omitted when it is deemed that such description will cause ambiguous interpretation of the example embodiments. 
       FIG. 1  is a diagram illustrating an example of a general T-junction constituting a power combiner/divider, and  FIGS. 2A to 2C  are graphs illustrating insertion loss, return loss, and isolation of the T-junction illustrated in  FIG. 1 . 
     A T-junction  100  may constitute a power divider or a power combiner. 
     The T-junction  100  may include three ports. For example, the T-junction  100  may include a first port Port  1 , a second port Port  2 , and a third port Port  3 . 
     In the case of the T-junction  100  constituting the power combiner, the T-junction  100  may combine and output signals inputted to two ports to one common port. For example, signals inputted to the second port Port  2  and the third port Port 3  may be combined and outputted to the first port Port  1 . 
     In the case of the T-junction  100  constituting the power divider, the T-junction  100  may separate and output a signal inputted to one port to two different ports. For example, when a signal is inputted to the first port Port  1 , signals having a same magnitude and a phase difference of 180 degrees may be outputted to the second port Port  2  and the third port Port  3 . 
     Referring to  FIG. 2C , it can be seen that ½ (−3 dB) of the signal inputted to the first port Port  1  of the T-junction  100  is outputted to the second port Port  2 , and vice versa. Accordingly, a sum of signals inputted to the second port Port  2  and the third port Port  3  in the same manner may be outputted to the first port Port  1 . 
     Referring to  FIG. 2B , it can be seen that ¼ (−6 dB) of the signal inputted to the second port Port  2  of the T-junction  100  is reflected. In addition, it can be seen that a remaining ¼ (−6 dB) of the signal inputted to the second port Port  2  is outputted to the third port Port  3 . Accordingly, isolation between the second port Port  2  and the third port Port  3  of the general T-junction  100  may be −6 dB. 
       FIG. 3  is a diagram illustrating a binary power combiner implemented through the T-junction illustrated in  FIG. 1 . 
     When one T-junction  100  is used, a 2-way combiner may be designed. In addition, when three T-junctions  100  are used, a 4-way combiner may be designed. That is, when 2 N −1 T-junctions  100  are used, a 2 N -way combiner may be designed. 
       FIG. 3  illustrates an 8-way binary combiner using seven T-junctions  100 . In order for the binary combiner to have 2N input ports, 2N−1 T-junctions  100  may need to be used. 
       FIGS. 4A to 4C  are diagrams illustrating an example of a conventional T-junction with improved isolation. 
     In the case of the combiner/divider illustrated in  FIG. 3 , the isolation between the second port Port  2  and the third port Port  3  or isolation between a fourth port Port  4  and a fifth port Port  5  may be −6 dB. The combiner/divider may generally need to have an isolation of −20 dB or less. 
     In order to improve the isolation, the conventional T-junction  200  may insert a microstrip line into an intersection point thereof, and may connect a matched load to the microstrip line to implement an isolation of −20 dB or less between the second port Port  2  and the third port Port  3 . 
     The T-junction  200  may be fabricated as two parts by separating a part intermediate in a height direction of a waveguide. In one part of the T-junction  200 , a dielectric substrate with the microstrip line and the load assembled at the intersection point may be fixed with silver-loaded epoxy. The T-junction  200  may be fabricated by assembling a corresponding part and a remaining part. 
     The T-junction  200  may require replacement of the dielectric substrate due to a fabricating error or tolerance of the microstrip line, and may have a short-coming in that workability is poor since the dielectric substrate is bonded with epoxy. In addition, the T-junction  200  may need be connected to the load by using a bonding wire, which may lead to different results for each component or for each operator, and thus it may be difficult to implement consistent performance. 
       FIG. 5  is a diagram illustrating a T-junction according to an example embodiment, and  FIGS. 6A to 6C  are graphs illustrating isolation of the T-junction illustrated in  FIG. 5 . 
     In a T-junction  300  constituting a power combiner or power divider, a dielectric substrate  500  on which a resistor  600  is formed may be inserted in a direction perpendicular to a lower plane of the power combiner or power divider to improve isolation between two input ports or output ports. 
     For example, the power combiner of the T-junction  300  may improve the isolation between the two input ports, and the power divider of the T-junction  300  may improve the isolation between the two output ports. 
     The T-junction  300  may include a power combiner/divider  400 , dielectric substrate  500 , and resistors  600 - 1  and  600 - 2 . 
     The power combiner/divider  400  may be a power combiner or a power divider depending on how to use. Hereinafter, for use of description, the power combiner/divider  400  will be collectively referred to as the combiner  400 . 
     The combiner  400  may be implemented as a waveguide. 
     The resistors  600 - 1  and  600 - 2  may be thin film resistors  600 - 1  and  600 - 2 . The thin film resistors  600 - 1  and  600 - 2  may be formed on the dielectric substrate  500 . 
     The dielectric substrate  500  may be inserted in a direction perpendicular to a plane of the combiner  400 . For example, the dielectric substrate  500  on which the film resistors  600 - 1  and  600 - 2  are formed may be inserted in a direction perpendicular to the plane of the combiner  400  to improve the isolation between the ports of the T-junction  300 . 
     That is, the T-junction  300  may insert the dielectric substrate  500  including the thin film resistors  600 - 1  and  600 - 2  into an intersection point thereof to improve the isolation. 
     In addition, the T-junction  300  may allow the dielectric substrate  500  to be easily replaced, thereby facilitating a tuning operation required by a fabricating error or design error. 
       FIGS. 6A to 6C , which are examples in which the T-junction  300  is implemented in a frequency band having a center frequency of 30 GHz and a bandwidth of 2 GHz, illustrate insertion loss, return loss, and isolation, respectively. 
       FIG. 6A  illustrates insertion losses S 12  and S 13  of a signal inputted to the first port Port  1  of the T-junction  300 . As illustrated in  FIG. 2A , the general T-junction  100  may exhibit an insertion loss of 3 dB, while the T-junction  300  may exhibit an insertion loss of 3.25 dB. A difference of 0.25 dB may be caused by the thin film resistors  600 - 1  and  600 - 2 . 
       FIG. 6B  illustrates that the first port Port  1  and the second port Port  2  have a return loss of 21 dB or more.  FIG. 6B  illustrates that the isolation between the second port Port  2  and the third port Port  3  is 21 dB or more. The T-junction  300  may improve the isolation by 15 dB or more in comparison to the general T-junction  100  having an isolation of 6 dB through the dielectric substrate  500  and the thin film resistors  600 - 1  and  600 - 2 . 
       FIG. 7  is a diagram illustrating a structure of the T-junction illustrated in  FIG. 5 . 
     The T-junction  300  may include the combiner  400 , dielectric substrate  500 , dielectric holder  800 , dielectric holder assembly bolts  711 - 1  and  711 - 2 , and combiner assembly bolts  710 - 1  to  710 - 6 . 
     The combiner  400  may include a combiner upper portion  410  and a combiner lower portion  430 . 
     The resistors  600 - 1  and  600 - 2  may be formed on opposite surfaces of the dielectric substrate  500 . 
     The dielectric holder  800  may be disposed perpendicular to the plane of the combiner  400  by fixing the dielectric substrate  500 . The dielectric holder  800  may include a first dielectric holder  810  and a second dielectric holder  830 . 
     The first dielectric holder  810  and the second dielectric holder  830  may contact the opposite surfaces of the dielectric substrate  500  to fix the dielectric substrate  500 . 
     The first dielectric holder  810  and the second dielectric holder  830  may be assembled by the dielectric holder assembly bolts  711 - 1  and  711 - 2 .  FIG. 7  illustrate two dielectric holder assembly bolts  711 - 1  and  711 - 2 , but the number of the dielectric holder assembly bolts is not necessarily limited thereto, and the appropriate number of the dielectric holder assembly bolts for assembling the dielectric holder  800  may be used. 
     The combiner assembly bolts  710 - 1  to  710 - 6  may fix the dielectric holder  800 , the combiner upper portion  410 , and the combiner lower portion  430 .  FIG. 7  illustrates six combiner assembly bolts  710 - 1  to  710 - 6 , but the number of the combiner assembly bolts is necessarily limited thereto, and the appropriate number of the combiner assembly bolts for assembling the dielectric holder  800 , the combiner upper portion  410 , and the combiner lower portion  430  may be used. 
       FIGS. 8A to 8C  are diagrams specifically illustrating a structure of the dielectric holder illustrated in  FIG. 7 . 
     The dielectric substrate  500  may be fixed by the first dielectric holder  810  and the second dielectric holder  830 . The dielectric holder  800  with the first dielectric holder  810  and the second dielectric holder  830  combined to fix the dielectric substrate  500  may be inserted into the combiner upper portion  410 . 
     The first dielectric holder  810  may include a plate, a first body positioned on a lower side of the plate to be in contact with a lower surface of the plate, and a second body bent to extend from one side of the first body. For example, the first body may have a longitudinal direction, and may horizontally contact the lower side of the plate, and the second body may extend in a direction perpendicular to the plate. 
     The first dielectric holder  810  may include a substrate mount portion  815  having one surface formed to be recessed from a bent portion where the first body and the second body are connected. The dielectric substrate  500  may be inserted into the substrate mount portion  815 . 
     The first dielectric holder  810  may include a horizontal stopper  811  having one surface formed to protrude from the other side of the first body, and a vertical stopper  813  having one surface formed to protrude from one side of the second body. 
     The horizontal stopper  811  and the vertical stopper  813  may fix the dielectric substrate  500  in a horizontal direction and a vertical direction, respectively. 
     The second dielectric holder  830  may be combined with the first dielectric holder  810  to fix the dielectric substrate  500 . 
     The second dielectric holder  830  may include the first body having a length direction and the second body bent to extend from one side of the first body. 
     The second dielectric holder  830  may include a substrate mount portion  835  having one surface formed to be recessed from the bent portion where the first body and the second body are connected. The dielectric substrate  500  may be inserted into the substrate mount portion  835 . 
     The second dielectric holder  830  may include a horizontal stopper insertion portion  831  having one surface formed to be recessed from the other side of the first body, and a vertical stopper insertion portion  833  having one surface formed to be recessed from one side of the second body. 
     When the first dielectric holder  810  and the second dielectric holder  830  are combined, the horizontal stopper  811  and the vertical stopper  813  may be inserted into the horizontal stopper insertion portion  831  and the vertical stopper insertion portion  833 , respectively. 
     The first dielectric holder  810  and the second dielectric holder  830  may be fixed by the dielectric holder assembly bolts  711 - 1  and  711 - 2 . 
       FIG. 9  is a diagram illustrating a method for assembling the dielectric holder and the combiner illustrated in  FIG. 7 , and  FIG. 10  is a diagram illustrating the T-junction illustrated in  FIG. 7 . 
     The dielectric holder  800  may be inserted into the combiner upper portion  410  in a vertical direction. For example, a portion of the dielectric holder  800  other than the plate may be inserted into a hole formed in the combiner upper portion  410 . That is, the dielectric holder  800  may be inserted into the combiner upper portion  410  in a vertical direction and fixed by the plate of the first dielectric holder  810 . 
     The dielectric substrate  500  fixed by the dielectric holder  800  may be inserted in a direction perpendicular to the plane of the combiner  400 . For example, the dielectric substrate  500  on which the film resistors  600 - 1  and  600 - 2  are formed may be inserted in a direction perpendicular to the plane of the combiner  400  to improve the isolation between the ports of the T-shaped junction  300 . 
     A resistance element may be inserted into the intersection point of the T-junction  300 , and thus the isolation between the ports may be 20 dB or more. 
     In addition, the dielectric substrate  500  may be easily replaced by using the dielectric holder  800 , thereby facilitating a tuning operation required by a fabricating error or design error of the T-junction  300 . 
     That is, since the dielectric substrate  500  on which the resistor  600  is implemented is designed as a separate module (for example, the dielectric holder  800 ), the dielectric substrate  500  may be easily assembled into the combiner  400 , and thus the T-junction  300  may easily replace the resistor  600 . In addition, when an error is found in a magnitude or resistance value of the resistor  600  after assembly, the error may be easily corrected. 
     The T-junction  300  may be implemented even when a gap between waveguides constituting the combiner  400  is narrow since the dielectric substrate  500  on which the resistor  600  is implemented is inserted in a direction perpendicular to the plane of the combiner  400 . 
       FIG. 11  is a diagram illustrating a power combiner/divider implemented through the T-junction illustrated in  FIG. 7 . 
     A portion indicated by a broken line in  FIG. 11  is too close to other portions of a waveguide, and thus interference may occur when the dielectric substrate  500  is inserted into the plane. However, when the dielectric substrate  500  is vertically inserted, such a problem may not occur. 
     The components described in the example embodiments may be implemented by hardware components including, for example, at least one digital signal processor (DSP), a processor, a controller, an application-specific integrated circuit (ASIC), a programmable logic element, such as a field programmable gate array (FPGA), other electronic devices, or combinations thereof. At least some of the functions or the processes described in the example embodiments may be implemented by software, and the software may be recorded on a recording medium. The components, the functions, and the processes described in the example embodiments may be implemented by a combination of hardware and software. 
     Although the example embodiments have been described with reference to the limited drawings as described above, various modifications and changes may be made from the foregoing descriptions by those skilled in the art. For example, suitable results can be achieved even if the described techniques are performed in a different order, and/or even if components of the described system, structure, device, circuit, and the like are coupled or combined in a different manner, or are replaced or substituted by other components or their equivalents. 
     Therefore, other implementations, other example embodiments, and equivalents to the claims are also within the scope of the following claims.