This application claims the benefit of PCT International Patent Application No. PCT/KR2010/007746, filed Nov. 4, 2010, and Korean Patent Application No. 10-2009-0115488, filed Nov. 27, 2009, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a phase shifter using a substrate integrated waveguide (SIW), and more particularly, to a phase shifter implemented through the formation of air holes and dielectric insertion in an SIW.
2. Description of the Related Art
A phase shifter is a device that changes or adjusts the phase of an electrical signal. It is widely used in microwave system applications such as wireless communication, radar, and measurement equipment. Phase shifters can be implemented in various ways. In particular, phase shifters using a substrate integrated waveguide (SIW) have recently been developed.
An SIW includes columns of via walls, which are arranged parallel to each other, on a dielectric substrate. Thus, it has a similar function to a conventional waveguide. In addition, the SIW has the advantages of both the conventional waveguide and a microstrip transmission line, like high Q factor, high power capacity, smaller size, and the possibility of integration. These advantages enable the SIW to be widely used in microwave and millimeter-wave circuits such as resonators, filters, and antennas. Phase shifter recently developed using this SIW are implemented by inserting ferrite toroid into the SIW or inserting a metal pole into the middle of the SIW.
Phase shifters must be designed to meet various performance requirements in terms of insertion loss, bandwidth, power capacity, size, weight, phase error, and the like. However, phase shifters using ferrite toroid are difficult to manufacture and are large in size and weight. On the other hand, phase shifters having a metal pole inserted into the middle of an SIW can easily adjust an amount of phase change by changing the position of the metal pole. However, since insertion loss increases as the amount of phase change increases, there is a limit to the amount of phase change.
The following description relates to a phase shifter which can be simply manufactured by forming air holes in a substrate of a substrate integrated waveguide (SIW) and inserting a dielectric material whose dielectric constant is different from that of the substrate into each of the air holes and which can be designed to provide a required amount of phase shift by adjusting a size of the air holes, a gap between the air holes, and the number of the air holes.
The following description also relates to a balun which can be simply manufactured by forming air holes in a substrate of an SIW and inserting a dielectric material whose dielectric constant is different from that of the substrate into each of the air holes and which can be designed to make conversion between an unbalanced signal and a balanced signal in the SIW by adjusting a size of the air holes, a gap between the air holes, and the number of the air holes.
The following description also relates to a directional coupler which can be simply manufactured by forming air holes in a substrate of an SIW and inserting a dielectric material whose dielectric constant is different from that of the substrate into each of the air holes.
The following description also relates an SIW which can vary a phase of a signal.
In one general aspect, there is provided a phase shifter using a substrate integrated waveguide (SIW). The phase shifter includes: a substrate; and a waveguide integrated on the substrate, wherein the waveguide includes an input port, an out port, two columns of via walls which are separated by a width of the waveguide and are arranged parallel to each other, and either a plurality of air holes which are formed to shift a phase of a signal between the input port and the output port or a plurality of rods, each including an air hole and a dielectric material inserted into the air hole.
When the waveguide includes the air holes, an amount by which the phase of the signal is shifted between the input port and the output port may vary according to at least one of a diameter of the air holes, a distance between the air holes, and the number of the air holes. When the waveguide includes the rods, the amount by which the phase of the signal is shifted between the input port and the output port may vary according to at least one of a diameter of the rods, a distance between the rods, and the number of the rods.
The amount by which the phase of the signal is shifted may increase in proportion to an increase in the diameter of the air holes.
The amount by which the phase of the signal is shifted may increase in proportion to an increase in at least one of the diameter of the rods and the number of the rods.
Each of the rods may have a structure in which the dielectric material is inserted into the air hole by using a male-female screwing method.
The amount by which the phase of the signal is shifted between the input port and the output port may increase in proportion to an increase in a depth to which the dielectric material is inserted into the air hole in each of the rods.
In another aspect, there is provided a balun using an SIW. The balun includes: a substrate; and a waveguide integrated on the substrate, wherein the waveguide includes two columns of via walls which are separated by a width of the waveguide and are arranged parallel to each other, an input port, a power divider which divides power of a signal input to the input port, first and second branches of the power divider, and a first output port and a second output port which are connected respectively to the first branch and the second branch, wherein any one of the first and second branches has a plurality of rods, each including an air hole and a dielectric material inserted into the air hole, and the other one of the first and second branches has a plurality of air holes or no air holes.
In another aspect, there is provided a directional coupler using an SIW. The directional coupler includes: a substrate; and a waveguide integrated on the substrate, wherein the waveguide includes a first input branch, a second input branch, a first output branch, a second output branch, a first column of via walls which is located between the first input branch and the second input branch, a second column of via walls which is located between the first output branch and the second output branch, an input port which is connected to one of the first input branch and the second input branch, and an isolated port which is connected to the other one of the first input branch and the second input branch, a power divider which divides power of a signal input to the input port between the first output branch and the second output branch, and a first output port and a second output port which are connected respectively to the first output branch and the second output branch, wherein any one of the first and second output branches has a plurality of rods, each including an air hole and a dielectric material inserted into the air hole, and the other one of the first and second branches has no air holes.
In another aspect, there is provided an SIW including: a substrate; and a waveguide integrated on the substrate, wherein the waveguide includes two columns of via walls which are separated by a width of the waveguide and are arranged parallel to each other and a plurality of rods, each including an air hole and a dielectric material inserted into the air hole by using a male-female screwing method to variably shift a phase of a signal.
Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.
A phase shifter which can be simply manufactured by forming air holes in a substrate of a substrate integrated waveguide (SIW) and inserting a dielectric material whose dielectric constant is different from that of the substrate into each of the air holes and which can be designed to provide a required amount of phase shift by adjusting a size of the air holes, a gap between the air holes, and the number of the air holes can be implemented.
In addition, a balun which can be simply manufactured by forming air holes in a substrate of an SIW and inserting a dielectric material whose dielectric constant is different from that of the substrate into each of the air holes and which can be designed to make conversion between an unbalanced signal and a balanced signal in the SIW by adjusting a size of the air holes, a gap between the air holes, and the number of the air holes can be implemented.
Further, a directional coupler can be simply implemented by forming air holes in a substrate of an SIW and inserting a dielectric material whose dielectric constant is different from that of the substrate into each of the air holes.
Further, a plurality of dielectric rods formed in an SIW can variably shift a phase of a signal, wherein each of the dielectric rods includes an air hole and a dielectric material inserted into the air hole using by a male-female screwing method.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
a),
a),
a) and
Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience.
Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.
An SIW has a TEm0 mode only. Wavenumber (k) in the TEm0 mode is proportional to the square root of a dielectric constant, and a propagation constant β may be defined by
A guided wavelength λg is in inversely proportional to the propagation constant β. Thus, when an effective dielectric constant inside the waveguide changes, a phase velocity vp of a wave also changes, thereby shifting an insertion phase of the waveguide as illustrated in the drawing. A reduction in the phase velocity vp resulting from an increase in the effective dielectric constant is referred to as a “slow-wave effect,” and the opposite is referred to as a “fast-wave effect.”
A phase shifter using substrate air holes and dielectric insertion is based on the above two principles (i.e., the fast-wave and slow-wave effects). When air holes are formed in a substrate with a relatively high dielectric constant (k), they are filled with air having a dielectric constant of 1. If the air holes are filled with a relatively low-k material, an effective dielectric constant of the entire substrate is reduced. This increases the phase velocity of a wave, causing a negative (−) phase shift. Conversely, after air holes are formed in a substrate with a relatively low dielectric constant, if the air holes are filled with a high-k material, the slow-wave effect may occur, leading to a positive (+) phase shift.
Referring to
The amount by which the phase of a signal is shifted between the input and output ports 4 and 5 may vary according to at least one of a diameter dh of the air holes 6, a gap phx,y between the air holes 6, and the number (m×n) of the air holes 6. Basically, the amount by which the phase of a signal is shifted increases in proportion to an increase in the diameter dh of the air holes 6. Further, the amount by which the phase of the signal is shifted is mostly proportional to the number (m×n) of the air holes 6 and can be adjusted by the gap phx,y between the air holes 6. Ultimately, the amount by which the phase of the signal is shifted can be adjusted using at least one of the diameter dh of the air holes 6, the gap phx,y (distance) between the air holes 6, and the number (m×n) of the air holes 6.
Actual implemented examples of the phase shifter according to the current exemplary embodiment will now be described. Phase shifters providing general phase shift values, e.g., 11.25°, 22.5°, and 45°, respectively, at a center frequency of 15 GHz were designed, and their characteristics were identified. A substrate used for each of these phase shifters was Rogers Corporation's Duroid 6010 (∈T=10.2, tan δ=0.0023) with a thickness of 0.635 mm. In addition, values of basic waveguide design variables were a=5 mm, dv=0.5 mm, pv=1 mm, It=5 mm, wt=2.1 mm, and ws=0.5 mm, and design variables for achieving a required amount of phase shift, such as a the diameter dh of air holes, the gap phx,y between the air holes, and the number (m×n) of the air holes, are listed in Table 1 below. For design and interpretation, high frequency structural simulator (HFSS) 10 of Ansoft Corporation was used. HFSS 10 is a commonly used simulation tool that is based on a finite element method (FEM).
Real models of the phase shifters designed using the simulation tool were made and are illustrated in
A phase shifter using an SIW according to another exemplary embodiment of the present invention may have a rod structure in which a dielectric material is inserted into each of the air holes 6 of the phase shifter according to the embodiment of
That is, the phase shifter using the SIW according to the current exemplary embodiment may include a substrate and a waveguide integrated on the substrate. The waveguide may include an input port, an output port, two columns of via walls which are separated by a width of the waveguide and are arranged parallel to each other, and a plurality of rods, each including an air hole formed in the substrate and a dielectric material inserted into the air hole to shift the phase of a signal between the input and output ports. The amount by which the phase of a signal is shifted between the input and output ports may vary according to at least one of a diameter of the rods, a distance between the rods, and the number of rods. The amount by which the phase of the signal is shifted may increase in proportion to an increase in the diameter of the rods. In addition, the amount by which the phase of the signal is shifted may increase as the number of rods increases.
A dielectric constant of the dielectric material inserted into each air hole may be different from that of the substrate, and each of the input and output ports may have a transition structure to a microstrip line for measurement. The transition structure may be tapered.
To identify characteristics of the phase shifter according to the current exemplary embodiment, phase shifters providing general phase shift values, e.g., 11.25°, 22.5°, and 45°, respectively, at a center frequency of 15 GHz were designed, and their characteristics were identified. A substrate used for each of these phase shifters was Rogers Corporation's Duroid 4003 (∈T=3.38, tan δ=0.0027) with a thickness of 0.813 mm, and a high-k material inserted into each air hole of the substrate was Duroid 6010 (∈T=10.2, tan δ=0.0023). In addition, values of basic waveguide design variables were a=8 mm, dv=0.5 mm, pv=1 mm, It=8 mm, wt=3 mm, and ws=1.74 mm, and design variables for achieving a required amount of phase shift, such as a diameter dr of rods, a gap prx,y between the rods, and the number (m×n) of the rods, are listed in Table 3 below.
Real models of the phase shifters having the high-k material inserted into each air hole were made and are illustrated in
Phase shift values of these phase shifters were measured, and the measurement results are illustrated in
Like the above-described phase shifters using only substrate air holes, the phase shifters using dielectric insertion exhibit superior characteristics in terms of phase error, insertion loss, and reflection loss as illustrated in
Meanwhile, a dielectric material may be inserted into each of a plurality of air holes by using a male-female screwing method, an embodiment of which is illustrated in
An SIW for a variable phase shift is illustrated in
A phase shifter using an SIW according to yet another exemplary embodiment of the present invention may be configured to perform a balun function. Here, the term “balun” is an abbreviation of “balance-unbalance.” It is a circuit or structure that converts a balanced signal into an unbalanced signal and vice versa.
To understand balun, an understanding of a balanced signal and an unbalanced signal is essential. Examples of the balanced signal and the unbalanced signal are illustrated in
Referring to (b) of
A radio frequency (RF) circuit includes both a part (such as a mixer or a surface acoustic wave (SAW) filter) using the balanced signal and a part (such as an antenna) using the unbalanced signal. Thus, a matching unit must sometimes be operated like a balun to connect these parts. That is, a balun is not the name of a certain device but refers to all entities used for conversion between the balanced signal and the unbalanced signal, as illustrated in
Generally, a balun is a three-port passive device that consists of one input port and two output ports. When a signal is transmitted to the input port, signals having the same amplitude and a phase difference of 180 degrees (±90°) are output from the two output ports, respectively. Therefore, electrical characteristics of the balun may be evaluated in terms of insertion loss (how small the loss of signal power between the input and output ports is, phase difference (how close the phase difference between the two signals at the output ports is to 180 degrees), insertion loss difference (how similar the amplitudes of the two signals at the output ports are to each other), and the like.
The conceptual configuration of the balun is illustrated in
Referring to
The amount by which the phase of a signal, which passes through the rods and is divided by the power divider 14, is shifted may vary according to at least one of a diameter dh or dr of the air holes or the rods, a gap phx,y or prx,y between the air holes or the rods, and the number of the air holes or the rods. The amount by which the phase of the signal is shifted may increase in proportion to an increase in the diameter dh of the air holes. In addition, the amount by which the phase of the signal is shifted may increase as the number of the rods increases. Each of the rods may have a structure in which a dielectric material is inserted into a corresponding air hole by using a male-female screwing method. Here, the amount by which the phase of the signal is shifted may increase as the dielectric material is inserted deeper into the corresponding air hole. The dielectric constant of the substrate 10 may be different from that of the dielectric material inserted into each air hole. Each of the input port 13, the first output port 17, and the second output port 18 has a transition structure to a microstrip line for measurement, and the transition structure may be tapered.
The balun illustrated in
Measurement results of the balun designed using an HFSS will now be described.
Referring to
Each of the rods 29 may have a structure in which a dielectric material is inserted into a corresponding air hole by using a male-female screwing method. The magnitude of the phase of a signal that passes through the rods 29 structured in this way may increase in proportion to an increase in a depth into which the dielectric material is inserted into each of the rods 29. Further, the dielectric constant of the substrate 20 is different from that of the rods 29.
Each of the input port 22, the first output port 27, and the second output port 28 has a transition structure to a microstrip line for measurement, and the transition structure may be tapered.
To identify characteristics of this directional coupler, a real model of the directional coupler was made. For, this model directional coupler, a Duroid 5880 substrate with a thickness of 0.508 mm and a relative dielectric constant of 2.2 was used. After air holes are formed in the substrate, a dielectric material with a high dielectric constant of 10.2 was inserted into each of the air holes, thereby increasing the effective dielectric constant of the substrate to reduce phase velocity. In addition, different numbers of air holes were used for impedance matching. The simulation results of the directional coupler structured as described above are illustrated in
Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Number | Date | Country | Kind |
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10-2009-0115488 | Nov 2009 | KR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/KR2010/007746 | 11/4/2010 | WO | 00 | 5/24/2012 |
Publishing Document | Publishing Date | Country | Kind |
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WO2011/065681 | 6/3/2011 | WO | A |
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Number | Date | Country | |
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20120274419 A1 | Nov 2012 | US |