Rat Race Coupler

Abstract

To reduce the phase error between the two output signals of a rat-race coupler. [Solution] A rat-race coupler (200) includes an annular conductor (1), a band adjustment section (2), and ports (P1-P4), where the annular conductor includes first to fourth strip conductors (11-14). The first strip conductor has a first terminal and a second terminal. The second strip conductor has a third terminal and a fourth terminal. The first terminal is connected to the third terminal through the third strip conductor. The second terminal is connected to the fourth terminal through the fourth strip conductor. The band adjustment section includes a fifth strip conductor (22), a sixth strip conductor (23), and a seventh strip conductor (24). The seventh strip conductor has a fifth terminal and a sixth terminal. The fifth terminal is connected to the third terminal through the fifth strip conductor. The sixth terminal is connected to the fourth terminal through the sixth strip conductor. The first port is connected to the fifth terminal. The second port is connected to the first terminal. The third port is connected to the second terminal.

Description

[Technical Field]

[0001] The present invention relates to electrical components, and more particularly to rat race couplers. [Background technology]

[0002] A rat-race coupler is also called a balun or a hybrid ring coupler. An ideal rat-race coupler can be used to combine two input signals into one output signal or to split one input signal into two output signals. However, currently used rat-race couplers often have phase errors in their outputs. Therefore, how to improve the phase error of a rat-race coupler is one of the important issues in this field. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention provides a rat-race coupler that can reduce the phase error between the two output signals of the rat-race coupler. [Means for solving the problem]

[0004] An embodiment of the present invention provides a rat-race coupler including a ring conductor, a first band adjustment section, a first port, a second port, and a third port. The ring conductor includes a first strip conductor, a second strip conductor, a third strip conductor, and a fourth strip conductor. The first strip conductor has a first terminal and a second terminal. The second strip conductor has a third terminal and a fourth terminal. The first terminal is connected to the third terminal through the third strip conductor. The second terminal is connected to the fourth terminal through the fourth strip conductor. The first band adjustment section includes a fifth strip conductor, a sixth strip conductor, and a seventh strip conductor. The seventh strip conductor has a fifth terminal and a sixth terminal. The fifth terminal is connected to the third terminal through the fifth strip conductor. The sixth terminal is connected to the fourth terminal through the sixth strip conductor. The first port is connected to the fifth terminal. The second port is connected to the first terminal. The third port is connected to the second terminal. The electrical length from the first terminal to the second terminal through the first strip conductor, the electrical length from the third terminal to the fourth terminal through the second strip conductor, and the electrical length from the fifth terminal to the sixth terminal through the seventh strip conductor are all substantially 1 / 2. The electrical length from the first terminal to the third terminal through the third strip conductor and the electrical length from the second terminal to the fourth terminal through the fourth strip conductor are all substantially 1 / 4. The electrical length from the third terminal to the fifth terminal through the fifth strip conductor and the electrical length from the fourth terminal to the sixth terminal through the sixth strip conductor are all substantially n / 2, where n is a natural number.

[0005] In an embodiment of the present invention, the n is an even number.

[0006] In an embodiment of the present invention, the rat-race coupler further includes a fourth port, which is connected to the center of the first strip conductor.

[0007] In an embodiment of the present invention, the first, second, and third ports are used to connect to at least one external system having a load impedance. The impedance of the second strip conductor is 1.2 times the load impedance. The impedance of the seventh strip conductor is 0.8 times the load impedance. The impedances of the fifth and sixth strip conductors are both 2.8 times the load impedance.

[0008] In an embodiment of the present invention, the rat-race coupler further includes a second band adjustment unit. The second band adjustment unit includes an eighth band conductor, a ninth band conductor, and a tenth band conductor. The tenth band conductor has a seventh terminal and an eighth terminal. The seventh terminal is connected to the fifth terminal through the eighth band conductor. The eighth terminal is connected to the sixth terminal through the ninth band conductor. The first port is connected to the seventh terminal and to the fifth terminal through the eighth band conductor.

[0009] In an embodiment of the present invention, the first, second, and third ports are used to connect to at least one external system having a load impedance. The impedance of the tenth strip conductor is 0.8 times the load impedance. The impedance of the seventh strip conductor is 1.4 times the load impedance. The impedances of the fifth, sixth, eighth, and ninth strip conductors are 2.8 times the load impedance.

[0010] In an embodiment of the present invention, the electrical length from the seventh terminal through the tenth strip conductor to the eighth terminal is substantially 1 / 2. The electrical length from the fifth terminal through the eighth strip conductor to the seventh terminal and the electrical length from the sixth terminal through the ninth strip conductor to the eighth terminal are both substantially m / 2, where m is a natural number.

[0011] In an embodiment of the present invention, the m is an even number.

[0012] In an embodiment of the present invention, m and n are equal.

[0013] In an embodiment of the present invention, the rat-race coupler further includes a third band adjustment unit. The third band adjustment unit includes an 11th band conductor, a 12th band conductor, and a 13th band conductor. The 13th band conductor has a 9th terminal and a 10th terminal. The 9th terminal is connected to the 7th terminal through the 11th band conductor. The 10th terminal is connected to the 8th terminal through the 12th band conductor. The first port is connected to the 9th terminal and to the 5th terminal through the 11th and 8th band conductors.

[0014] In an embodiment of the present invention, the impedance of the seventh and tenth strip conductors is 1.4 times the load impedance, the impedance of the thirteenth strip conductor is 0.8 times the load impedance, and the impedance of the fifth, sixth, eighth, ninth, eleventh, and twelfth strip conductors is 2.8 times the load impedance.

[0015] In this embodiment of the present invention, the electrical length from the ninth terminal through the thirteenth strip conductor to the tenth terminal is substantially 1 / 2. The electrical length from the seventh terminal through the eleventh strip conductor to the ninth terminal and the electrical length from the eighth terminal through the twelfth strip conductor to the tenth terminal are both substantially k / 2, where k is a natural number.

[0016] In an embodiment of the present invention, the k is an even number.

[0017] In an embodiment of the present invention, k, m and n are equal. [Effects of the Invention]

[0018] Based on the above, the present invention uses a strip conductor with a specific length to form a band adjustment section, and combines the ring conductor and one or more band adjustment sections to form a multi-layer rat-race coupler, which can reduce the phase error of the two output signals of the rat-race coupler. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing a rat race coupler. [Figure 2A] FIG. 1 is a schematic diagram of a two-layer rat-race coupler according to one embodiment of the present invention. [Figure 2B] FIG. 1 is a schematic diagram of a two-layer rat-race coupler according to one embodiment of the present invention. [Figure 3] FIG. 2 is a schematic diagram of a three-layer rat-race coupler according to one embodiment of the present invention. [Figure 4]FIG. 2 is a schematic diagram of a four-layer rat-race coupler according to one embodiment of the present invention. [Figure 5] FIG. 1 is a simulation diagram of the S parameters of a two-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 6] FIG. 1 is a simulation diagram of the S parameters of a two-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 7] FIG. 1 is a simulation diagram of the S parameters of a two-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 8] FIG. 1 is a simulation diagram of the S parameters of a two-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 9] FIG. 1 is a simulation diagram of the S parameters of a three-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 10] FIG. 1 is a simulation diagram of the S parameters of a three-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 11] FIG. 1 is a simulation diagram of the S parameters of a three-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 12] FIG. 1 is a simulation diagram of the S parameters of a three-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 13] FIG. 1 is a simulation diagram of the S parameters of a four-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 14] FIG. 1 is a simulation diagram of the S parameters of a four-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 15] FIG. 1 is a simulation diagram of the S parameters of a four-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 16] FIG. 1 is a simulation diagram of the S parameters of a four-layer rat-race coupler illustrated by an embodiment of the present invention. [Figure 17] 1 is a simulation diagram of the S-parameters of a seven-layer rat-race coupler according to an embodiment of the present invention; [Figure 18] 1 is a simulation diagram of the S parameters of a three-layer rat-race coupler according to an embodiment of the present invention. [Figure 19] 1 is a simulation diagram of the S parameters of a three-layer rat-race coupler according to an embodiment of the present invention. [Figure 20] 1 is a simulation diagram of the S parameters of a three-layer rat-race coupler according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Reference will now be made in detail to the exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same element numbers are used in the drawings and the description to refer to the same or like parts.

[0021] In the following examples, two components that "connect" to each other connect to each other directly, and two components that "electrically connect" to each other connect to each other either directly or indirectly (e.g., two components connect to each other through a third component).

[0022] FIG. 1 is a schematic diagram showing a rat-race coupler 100. The rat-race coupler 100 can be a structure formed by a single annular conductor #1. Therefore, the rat-race coupler 100 can be referred to as a single-layer rat-race coupler, a balun, or a hybrid ring coupler. The annular conductor #1 is, for example, a circle or a parallelogram formed by strip-shaped conductors 11, 12, 13, and 14, where strip conductor 12 is the opposite side of strip conductor 11, and strip conductor 14 is the opposite side of strip conductor 13. More specifically, strip conductor 11 has terminals E1 and E2. Strip conductor 12 has terminals E3 and E4. Terminal E1 is connected to terminal E3 through strip conductor 13. Terminal E2 is connected to terminal E4 through strip conductor 14. Those skilled in the art will understand that the rat race coupler referred to in the present invention can be constructed by a combination of components suitable as a waveguide, a microstrip line installed on a single-layer or multi-layer substrate, a coaxial cable, or other microwave or millimeter-wave signal circuit.

[0023] The rat-race coupler 100 may include four ports made of conductive material, including ports P1, P2, P3, and P4. Port P1 may be connected to terminal E3, ports P2 and P3 may be connected to terminals E1 and E2, respectively, and port P4 may be connected to the center of the strip conductor 11. The electrical length from terminal E1 through strip conductor 11 to terminal E2 or from terminal E3 through strip conductor 12 to terminal E4 may be 1 / 2. The electrical length from terminal E1 through strip conductor 13 to terminal E3 or from terminal E2 through strip conductor 14 to terminal E4 may be 1 / 4. In each embodiment of the present invention, the electrical length is defined as the ratio of the physical length of the signal path (e.g., conductor) to the wavelength λ corresponding to the center operating frequency of the rat-race coupler 100. The wavelength referred to here is not the vacuum wavelength but the characteristic wavelength of the signal in the signal path / waveguide structure. The electrical length between port P1 and port P2 can be equal to 1 / 4 (e.g., the electrical length from terminal E1 through strip conductor 13 to terminal E3). In other words, when a signal having this operating frequency is transmitted from port P1 to port P2, it is exactly one-quarter wavelength. The electrical length between port P1 and port P3 can be equal to 3 / 4 (e.g., the electrical length from terminal E3 through strip conductor 12 to terminal E4 plus the electrical length from terminal E2 through strip conductor 14 to terminal E4). The electrical length between port P1 and port P4 can be equal to 1 / 2 (e.g., the electrical length from the first terminal E1 through strip conductor 13 to terminal E3 plus half the electrical length from terminal E1 through strip conductor 11 to terminal E2). The electrical length between port P2 and port P3 can be equal to 1 / 2 (e.g., the electrical length from the first terminal E1 through strip conductor 11 to the second terminal E2). The electrical length between port P2 and port P4 can be equal to 1 / 4 (e.g., half the electrical length from terminal E1 through strip conductor 11 to terminal E2). The electrical length between port P3 and port P4 can be equal to 1 / 4 (e.g., half the electrical length from terminal E1 through strip conductor 11 to terminal E2).

[0024] The rat-race coupler 100 can be used to split one input signal into two output signals. For example, when one input signal is input to the rat-race coupler 100 from port P1, the rat-race coupler 100 can split the input signal into two output signals and output two output signals having the same amplitude through ports P2 and P3, respectively, where the output signal output from port P2 and the output signal output from port P3 have a phase difference of 180 degrees, and port P4 is isolated so that no signal is output from port P4.

[0025] The rat-race coupler 100 can be used to combine two input signals into one output signal. For example, when two input signals are input to the rat-race coupler 100 from ports P2 and P3, respectively, the rat-race coupler 100 can combine the two input signals into one output signal. Port P4 can act as a sum port or Σ port, where the output signal output from port P4 is the sum of the two input signals. Port P1 can act as a Δ port, where the output signal output from port P1 is the difference between the two input signals.

[0026] The rat-race coupler 100 can connect a load through port P1, port P2, port P3, or port P4. In one embodiment, port P1, port P2, port P3, or port P4 is used to connect to at least one external system (not shown), which has a load impedance. The impedance of strip conductor 11, strip conductor 12, strip conductor 13, or strip conductor 14 in ring conductor #1 can be 1.2 times the load impedance. For example, if the load impedance is 50 ohms, the impedance of ring conductor #1 can be 60 ohms.

[0027] In one embodiment, one or more additional band adjustment units can be added to the structure of rat-race coupler 100 to form an A-layer rat-race coupler including one annular conductor and (A-1) band adjustment units, where A is any natural number. "a" is defined as the index of the order of the annular conductor or band adjustment unit in the A-layer rat-race coupler, and a=1, 2, ..., A. For example, a=1 is used to represent the first component of the A-layer rat-race coupler, which is the annular conductor (i.e., annular conductor #1 directly connected to port P2, port P3, or port P4); a=2 is used to represent the second component of the A-layer rat-race coupler, which is the band adjustment unit (i.e., band adjustment unit #2 directly connected to annular conductor #1 through port P2, port P3, or port P4); and a=A is used to represent the Ath component of the A-layer rat-race coupler, which is the band adjustment unit (i.e., band adjustment unit #A directly connected to port P1).

[0028] The phase error caused by the A-layer rat-race coupler can be smaller than the phase error caused by the rat-race coupler 100. For example, an additional band-adjustment section can be added to the structure of the rat-race coupler 100 to form a two-layer rat-race coupler, as shown in FIG. 2A.

[0029] 2A is a schematic diagram showing a two-layer rat-race coupler 200 according to an embodiment of the present invention. Compared with the structure of rat-race coupler 100 shown in FIG. 1, rat-race coupler 200 can further include an additional band-adjusting section #2. Band-adjusting section #2 is, for example, a U-shaped conductor formed by strip conductor 22, strip conductor 23, and strip conductor 24, where strip conductor 23 is the opposite side of strip conductor 24. Strip conductor 24 has terminals E5 and E6. Terminal E5 is connected to terminal E3 through strip conductor 23. Terminal E6 is connected to terminal E4 through strip conductor 24.

[0030] Port P1 can be connected to terminal E5, port P2 can be connected to terminal E1, port P3 can be connected to terminal E2, and port P4 can be connected to the center of strip conductor 11. Port P1 can be electrically connected to strip conductor 12 of ring conductor #1 through band adjusting section #2. Port P2, port P3, or port P4 can be electrically connected to strip conductor 23 and strip conductor 24 of band adjusting section #2 through ring conductor #1. The electrical length from terminal E5 through strip conductor 22 to terminal E6 is substantially 1 / 2, and the electrical length from terminal E3 through strip conductor 23 to terminal E5 or the electrical length from terminal E4 through strip conductor 24 to terminal E6 are both substantially n / 2. When n is a natural number, that is, when the electrical length of strip conductor 23 (i.e., from terminal E3 through strip conductor 23 to terminal E5) and the electrical length of strip conductor 24 (i.e., from terminal E4 through strip conductor 24 to terminal E6) reach an integer multiple of half wavelength λ / 2, rat-race coupler 200 can have better performance. In order to make the electrical length of strip conductor 23 or strip conductor 24 reach n / 2, strip conductor 23 or strip conductor 24 can be a conductor having a meander structure.

[0031] The rat race coupler 200 is a two-layer rat race coupler (i.e., A=2) formed by adding one additional band adjustment section #2 to the structure of the rat race coupler 100. The electrical length between port P1 and port P2 can be equal to (2n+1) / 4 (e.g., the electrical length from terminal E1 to terminal E3 plus the electrical length from terminal E3 to terminal E5). The electrical length between port P1 and port P3 can be equal to (2n+3) / 4 (e.g., the electrical length from terminal E5 to terminal E6 plus the electrical lengths from terminal E2 to terminal E4 and from terminal E4 to terminal E6). The electrical length between port P1 and port P4 can be equal to (n+1) / 2 (e.g., the electrical length from terminal E1 to terminal E3 plus the electrical length from terminal E3 to terminal E5 and half the electrical length from terminal E1 to terminal E2). The electrical length between port P2 and port P3 can be equal to 1 / 2 (e.g., the electrical length from terminal E1 to terminal E2). The electrical length between port P2 and port P4 can be equal to 1 / 4 (e.g., half the electrical length from terminal E1 to terminal E2). The electrical length between port P3 and port P4 can be equal to 1 / 4 (e.g., half the electrical length from terminal E1 to terminal E2).

[0032] The rat-race coupler 200 can connect a load through port P1, port P2, port P3, or port P4. In one embodiment, port P1, port P2, port P3, or port P4 is used to connect to at least one external system (not shown), which has a load impedance. The impedance of strip conductor 11, strip conductor 12, strip conductor 13, or strip conductor 14 in the ring conductor #1 can be 1.2 times the load impedance. The impedance of strip conductor 22 in the band adjustment unit #2 can be 0.8 times the load impedance. The impedance of strip conductor 23 or strip conductor 24 in the band adjustment unit #2 can be 2.8 times the load impedance.

[0033] For example, if the load impedance is 50 ohms, the impedance of ring conductor #1 may be 60 ohms, the impedance of strip conductor 22 may be 40 ohms, and the impedance of strip conductor 23 or strip conductor 24 may be 140 ohms.

[0034] 2B, rat-race coupler 200 may not have port P4, or port P4 of rat-race coupler 200 may not be connected to any load (e.g., port P4 is not connected to an external system). When one input signal is input to rat-race coupler 200 from port P1, rat-race coupler 200 can split the input signal into two output signals and output two output signals with the same amplitude through ports P2 and P3, respectively, with a 180-degree phase difference between the output signal output from port P2 and the output signal output from port P3. On the other hand, when two input signals are input to rat-race coupler 200 from ports P2 and P3, respectively, port P1 can function as a delta port, and the output signal output from port P1 is the difference between the two input signals.

[0035] As shown in Figure 3, a three-layer rat-race coupler can be formed by adding an additional band-adjustment section to the structure of rat-race coupler 200. Figure 3 is a schematic diagram showing a three-layer rat-race coupler 300 according to one embodiment of the present invention. Compared with the structure of rat-race coupler 200 shown in Figure 2A, rat-race coupler 300 can further include band-adjustment section #3.

[0036] Band-adjusting section #3 is, for example, a U-shaped conductor formed by strip conductors 32, 33, and 34, with strip conductor 34 being the opposite side of strip conductor 33. Strip conductor 32 has terminals E7 and E8. Terminal E7 is connected to terminal E5 through strip conductor 33. Terminal E8 is connected to terminal E6 through strip conductor 34.

[0037] Port P1 can be connected to terminal E7 and to terminal E5 through strip conductor 33. Ports P2 and P3 can be connected to terminals E1 and E2, respectively, and port P4 can be connected to the center of strip conductor 11. Port P1 can be electrically connected to strip conductor 22 of band adjusting section #2 through band adjusting section #3, and port P2, port P3, or port P4 can be electrically connected to strip conductor 33 and strip conductor 34 of band adjusting section #3 through ring conductor #1 and band adjusting section #2. The electrical length from terminal E7 to terminal E8 through strip conductor 32 is substantially 1 / 2, and the electrical length from terminal E5 to terminal E7 through strip conductor 33 or the electrical length from terminal E6 to terminal E8 through strip conductor 34 is both substantially m / 2. When m is a natural number, that is, when the electrical length of strip conductor 33 (i.e., from terminal E5 through strip conductor 33 to terminal E7) and the electrical length of strip conductor 34 (i.e., from terminal E6 through strip conductor 34 to terminal E8) reach an integer multiple of half wavelength λ / 2, rat-race coupler 300 can have better performance. To make the electrical length of strip conductor 33 or strip conductor 34 reach m / 2, strip conductor 33 or strip conductor 34 can be a conductor having a meandering structure.

[0038] Rat race coupler 300 is a three-layer rat race coupler formed by adding two additional band adjustment units #2 and #3 to the structure of rat race coupler 100 (i.e., A=3). The electrical length between port P1 and port P2 can be equal to (2n+2m+1) / 4 (e.g., the electrical length from terminal E1 to terminal E3 plus the electrical length from terminal E3 to terminal E5 plus the electrical length from terminal E5 to terminal E7). The electrical length between port P1 and port P3 can be equal to (2m+2n+3) / 4 (e.g., the electrical length from terminal E7 to terminal E8 plus the electrical length from terminal E2 to terminal E4, the electrical length from terminal E4 to terminal E6, and the electrical length from terminal E6 to terminal E8). The electrical length between port P1 and port P4 can be equal to (m+n+1) / 2 (e.g., the electrical length from terminal E1 to terminal E3 plus the electrical length from terminal E3 to terminal E5 plus the electrical length from terminal E5 to terminal E7 plus half the electrical length from terminal E1 to terminal E2). The electrical length between port P2 and port P3 can be equal to 1 / 2 (e.g., the electrical length from terminal E1 to terminal E2). The electrical length between port P2 and port P4 can be equal to 1 / 4 (e.g., half the electrical length from terminal E1 to terminal E2). The electrical length between port P3 and port P4 can be equal to 1 / 4 (e.g., half the electrical length from terminal E1 to terminal E2).

[0039] The rat-race coupler 300 can connect to a load through port P1, port P2, port P3, or port P4. In one embodiment, port P1, port P2, port P3, or port P4 is used to connect to at least one external system (not shown), which has a load impedance. The impedance of strip conductor 11, strip conductor 12, strip conductor 13, or strip conductor 14 in the ring conductor #1 can be 1.2 times the load impedance. The impedance of strip conductor 22 in the band adjustment unit #2 can be 0.8 times the load impedance. The impedance of strip conductor 23 or strip conductor 24 in the band adjustment unit #2 can be 2.8 times the load impedance. The impedance of strip conductor 32 in the band adjustment unit #3 can be 1.4 times the load impedance. The impedance of strip conductor 33 or strip conductor 34 in the band adjustment unit #3 can be 2.8 times the load impedance.

[0040] For example, if the load impedance is 50 ohms, the impedance of ring conductor #1 can be 60 ohms, the impedance of strip conductor 22 can be 40 ohms, the impedance of strip conductor 23 or strip conductor 24 can be 140 ohms, the impedance of strip conductor 32 can be 70 ohms, and the impedance of strip conductor 33 or strip conductor 34 can be 140 ohms.

[0041] In one embodiment, rat-race coupler 300 does not have port P4, or port P4 of rat-race coupler 300 is not connected to any load (eg, port P4 is not connected to an external system).

[0042] As shown in Figure 4, one additional band adjustment unit can be added to the structure of rat race coupler 300 to form a four-layer rat race coupler. Figure 4 is a schematic diagram showing a four-layer rat race coupler 400 according to one embodiment of the present invention. Compared with the structure of rat race coupler 300 shown in Figure 3, rat race coupler 400 can further include band adjustment unit #4.

[0043] Band-adjusting section #4 is, for example, a U-shaped conductor formed by strip conductors 42, 43, and 44, with strip conductor 44 being an opposing side of strip conductor 43. Strip conductor 42 has terminals E9 and E10. Terminal E9 is connected to terminal E7 through strip conductor 43. Terminal E10 is connected to terminal E8 through strip conductor 44.

[0044] Port P1 can be connected to terminal E9 and is connected to terminal E5 through strip conductor 43 and strip conductor 33. Ports P2 and P3 can be connected to terminal E1 and terminal E2, respectively, and port P4 can be connected to the center of strip conductor 11. Port P1 can be electrically connected to strip conductor 32 of band adjustment unit #3 through band adjustment unit #4, and port P2, port P3, or port P4 can be electrically connected to strip conductor 43 and strip conductor 44 of band adjustment unit #4 through ring conductor #1, band adjustment unit #2, and band adjustment unit #3. The electrical length from terminal E9 through strip conductor 42 to terminal E10 is substantially 1 / 2. The electrical length from terminal E7 through strip conductor 43 to terminal E9 and the electrical length from terminal E8 through strip conductor 44 to terminal E10 are both substantially k / 2. When k is a natural number, that is, when the electrical length of strip conductor 43 (i.e., from terminal E7 through strip conductor 43 to terminal E9) or strip conductor 44 (i.e., from terminal E8 through strip conductor 44 to terminal E10) reaches an integer multiple of half wavelength λ / 2, rat-race coupler 400 can have better performance. In order to make the electrical length of strip conductor 43 or strip conductor 44 reach k1 / 2, strip conductor 43 or strip conductor 44 can be a conductor having a meandering structure.

[0045] Rat race coupler 400 is a four-layer rat race coupler formed by adding three additional band adjusting units #2, #3, and #4 to the structure of rat race coupler 100 (i.e., A=4). The electrical length between port P1 and port P2 can be equal to (2n+2m+2k+1) / 4 (e.g., the electrical length from terminal E1 to terminal E3 plus the electrical length from terminal E3 to terminal E5, the electrical length from terminal E5 to terminal E7, and the electrical length from terminal E7 to terminal E9). The electrical length between port P1 and port P3 can be equal to (2n+2m+2k+3) / 4 (e.g., the electrical length from terminal E9 to terminal E10 plus the electrical length from terminal E2 to terminal E4, the electrical length from terminal E4 to terminal E6, the electrical length from terminal E6 to terminal E8, and the electrical length from terminal E8 to terminal E10). The electrical length between port P1 and port P4 can be equal to (n+m+k+1) / 2 (e.g., the electrical length from terminal E1 to terminal E3 plus the electrical length from terminal E3 to terminal E5 plus the electrical length from terminal E5 to terminal E7 plus the electrical length from terminal E7 to terminal E9 plus half the electrical length from terminal E1 to terminal E2). The electrical length between port P2 and port P3 can be equal to 1 / 2 (e.g., the electrical length from terminal E1 to terminal E2). The electrical length between port P2 and port P4 can be equal to 1 / 4 (e.g., half the electrical length from terminal E1 to terminal E2). The electrical length between port P3 and port P4 can be equal to 1 / 4 (e.g., half the electrical length from terminal E1 to terminal E2).

[0046] It is worth noting that the A-layer rat-race coupler of the present invention can have more than four layers. For example, one or more additional band adjustment units #b (b is a natural number greater than 4) can be arranged between band adjustment unit #4 and port P1 to connect band adjustment unit #4 to port P1, and the one or more additional band adjustment units #b can have the same structure or impedance as band adjustment unit #4, and the connection method between the one or more additional band adjustment units #b and band adjustment unit #4 can be the same as the connection method between band adjustment unit #4 and band adjustment unit #3.

[0047] The rat-race coupler 400 can connect to a load through port P1, port P2, port P3, or port P4. In one embodiment, port P1, port P2, port P3, or port P4 is used to connect to at least one external system (not shown), which has a load impedance. The impedance of strip conductor 11, strip conductor 12, strip conductor 13, or strip conductor 14 in the ring conductor #1 can be 1.2 times the load impedance. The impedance of strip conductor 22 in band adjustment unit #2 can be 0.8 times the load impedance. The impedance of strip conductor 23 or strip conductor 24 in band adjustment unit #2 can be 2.8 times the load impedance. The impedance of strip conductor 32 in band adjustment unit #3 can be 1.4 times the load impedance. The impedance of strip conductor 33 or strip conductor 34 in band adjustment unit #3 can be 2.8 times the load impedance. The impedance of strip conductor 42 of band adjuster #4 (or band adjuster #b) can be set to 1.4 times the load impedance, and the impedance of strip conductor 43 or strip conductor 44 of band adjuster #4 (or band adjuster #b) can be set to 2.8 times the load impedance.

[0048] For example, if the load impedance is 50 ohms, the impedance of band adjuster #1 can be 60 ohms, the impedance of strip conductor 22 can be 40 ohms, the impedance of strip conductor 23 or strip conductor 24 can be 140 ohms, the impedance of strip conductor 32 can be 70 ohms, and the impedance of strip conductor 33 or strip conductor 34 can be 140 ohms. The impedance of strip conductor 42 can be 70 ohms. The impedance of strip conductor 43 or strip conductor 44 can be 140 ohms.

[0049] In one embodiment, rat-race coupler 400 does not have port P4, or port P4 of rat-race coupler 400 is not connected to any load (eg, port P4 is not connected to an external system).

[0050] FIG. 5 is a graph showing the S-parameter simulation of a two-layer rat-race coupler with n=0.5 (e.g., rat-race coupler 200 having strip conductors 23 and 24 with electrical lengths of 1 / 4) according to one embodiment of the present invention, where curve 510 is the S-parameter S 11 (i.e., the input reflection coefficient or return loss of port P1), and curve 520 represents the S-parameter S 21 (i.e., the insertion loss of a signal transmitted from port P1 to port P2), and curve 530 represents the S-parameter S 31 (i.e., the insertion loss when a signal is transmitted from port P1 to port P3), curve 540 represents the phase difference between port P2 and port P3, and points 51 and 52 are the intersections of the three curves at -5 dB. Referring to points 51 and 52, the efficient operating bandwidth of the two-layer rat-race coupler is between about 18.5 GHz and 27.5 GHz, and the phase error is only about 1 degree.

[0051] FIG. 6 is a graph showing the simulation of the S-parameters of a two-layer rat-race coupler with n=1 (e.g., rat-race coupler 200 having strip conductors 23 and 24 with half electrical length) according to one embodiment of the present invention, where curve 610 is the S-parameter S 11 , and curve 620 represents the S-parameter S 21 , and curve 630 represents the S-parameter S 31 , and curve 640 represents the phase difference between port P2 and port P3. Points 61 and 62 are the intersections of the three curves at -5 dB, and points 63 and 64 are the values ​​of curve 610 at -10 dB. Referring to points 61 and 62, the effective operating band of the two-layer rat-race coupler is between about 15 GHz and 31 GHz, and the phase error is only about 2.5 degrees. Referring to points 63 and 64, the S-parameter S of the two-layer rat-race coupler in the frequency band of 15.5 GHz to 30.5 GHz is 11 has good gain characteristics.

[0052] FIG. 7 is a graph showing the simulation of the S-parameters of a two-layer rat-race coupler with n=1.5 (e.g., rat-race coupler 200 having strip conductors 23 and 24 with an electrical length of 3 / 4) according to one embodiment of the present invention, where curve 710 is the S-parameter S 11 , and curve 720 represents the S-parameter S 21 , and curve 730 represents the S-parameter S 31 , curve 740 represents the phase difference between port P2 and port P3, and points 71 and 72 are the intersections of the three curves at -5 dB. Referring to points 71 and 72, the effective operating band of the two-layer rat-race coupler is between about 19.5 GHz and 26.5 GHz, and the phase error is only about 2.5 degrees.

[0053] FIG. 8 is a simulation diagram of the S-parameters of a two-layer rat-race coupler with n=2 (e.g., rat-race coupler 200 having strip conductors 23 and 24 with an electrical length of 1) according to one embodiment of the present invention, where curve 810 is the S-parameter S 11 , and curve 820 represents the S-parameter S 21 , and curve 830 represents the S-parameter S 31 , and curve 840 represents the phase difference between port P2 and port P3. Points 81 and 82 are the intersections of the three curves at -5 dB, and points 83 and 84 are the values ​​of curve 810 at -10 dB. Referring to points 81 and 82, the effective operating band of the two-layer rat-race coupler is between about 17.5 GHz and 28.5 GHz, and the phase error is only about 2 degrees. Referring to points 83 and 84, the S-parameter S of the two-layer rat-race coupler in the frequency band 19 GHz to 27 GHz is 11 has good gain characteristics.

[0054] FIG. 9 is a graph showing the simulation of the S-parameters of a three-layer rat-race coupler with n=m=0.5 (e.g., rat-race coupler 300 having strip conductors 23, 24, 33, and 34 with electrical lengths of 1 / 4) according to an embodiment of the present invention. Curve 910 shows the S-parameters S 11 , and curve 920 represents the S-parameter S 21, and curve 930 represents the S-parameter S 31 , and curve 940 represents the phase difference between port P2 and port P3. Points 91 and 92 are the intersections of the three curves at -5 dB, and points 93 and 94 are the values ​​of curve 910 at -10 dB. Referring to points 91 and 92, the effective operating band of the three-layer rat-race coupler is between about 19 GHz and 27 GHz, and the phase error is only about 0 degrees. Referring to points 93 and 94, the S-parameter S of the three-layer rat-race coupler in the frequency band 21 GHz to 25 GHz is 11 has good gain characteristics.

[0055] FIG. 10 is a graph showing the simulation of the S-parameters of a three-layer rat-race coupler with n=m=1 (e.g., rat-race coupler 300 having strip conductors 23, 24, 33, and 34 with half electrical length) according to one embodiment of the present invention. Curve 1010 shows the S-parameters S 11 and curve 1020 represents the S-parameter S 21 and curve 1030 represents the S-parameter S 31 , and curve 1040 represents the phase difference between port P2 and port P3. Points 1001 and 1002 are the intersections of the three curves at -5 dB, and points 1003 and 1004 are the values ​​of curve 1010 at -10 dB. Referring to points 1001 and 1002, the effective operating band of the three-layer rat-race coupler is between about 14.5 GHz and 31.5 GHz, and the phase error is only about 0.5 degrees. Referring to points 1003 and 1004, the S-parameter S of the three-layer rat-race coupler in the frequency band 15 GHz to 31 GHz is 11 has good gain characteristics.

[0056] FIG. 11 is a graph showing the simulation of the S-parameters of a three-layer rat-race coupler with n=m=1.5 (e.g., rat-race coupler 300 having strip conductors 23, 24, 33, and 34 with an electrical length of 3 / 4) according to an embodiment of the present invention. Curve 1110 shows the S-parameters S 11 and curve 1120 represents the S-parameter S 21 and curve 1130 represents the S-parameter S 31, and curve 1140 represents the phase difference between port P2 and port P3. Points 1101 and 1102 are the intersections of the three curves at -5 dB, and points 1103 and 1104 are the values ​​of curve 1110 at -10 dB. Referring to points 1101 and 1102, the effective operating band of the three-layer rat-race coupler is between about 20.5 GHz and 25.5 GHz, and the phase error is only about 0 degrees. Referring to points 1103 and 1104, the S-parameter S of the three-layer rat-race coupler in the frequency band of 21.5 GHz to 24.5 GHz is 11 has good gain characteristics.

[0057] FIG. 12 is a graph showing the simulation of the S-parameters of a three-layer rat-race coupler with n=m=2 (e.g., rat-race coupler 300 having strip conductors 23, 24, 33, and 34 with an electrical length of 1) according to one embodiment of the present invention. Curve 1210 shows the S-parameters S 11 and curve 1220 represents the S-parameter S 21 and curve 1230 represents the S-parameter S 31 , and curve 1240 represents the phase difference between port P2 and port P3. Points 1201 and 1202 are the intersections of the three curves at -5 dB, and points 1203 and 1204 are the values ​​of curve 1210 at -10 dB. Referring to points 1201 and 1202, the effective operating band of the three-layer rat-race coupler is between about 17 GHz and 29 GHz, and the phase error is only about 0 degrees. Referring to points 1203 and 1204, the S-parameter S of the three-layer rat-race coupler in the frequency band of 18 GHz to 28 GHz is 11 has good gain characteristics.

[0058] FIG. 13 is a graph showing the simulation of the S-parameters of a four-layer rat-race coupler with n=m=k=0.5 (e.g., rat-race coupler 400 having strip conductors 23, 24, 33, 34, 43, and 44 with electrical lengths of 1 / 4) according to one embodiment of the present invention. Curve 1310 shows the S-parameters S 11 and curve 1320 represents the S-parameter S 21 and curve 1330 represents the S-parameter S 31, and curve 1340 represents the phase difference between port P2 and port P3. Points 1301 and 1302 are the intersections of the three curves at -5 dB, and points 1303, 1304, 1305, and 1306 are the values ​​of curve 1310 at -10 dB. Referring to points 1301 and 1302, the effective operating band of the four-layer rat-race coupler is between about 18.5 GHz and 27.5 GHz, and the phase error is only about 0 degrees. Referring to points 1303, 1304, 1305, and 1306, the S-parameter S of the four-layer rat-race coupler is 11 has good gain characteristics.

[0059] FIG. 14 is a graph showing the simulation of S-parameters of a four-layer rat-race coupler with n=m=k=1 (e.g., rat-race coupler 400 having strip conductors 23, 24, 33, 34, 43, and 44 with half electrical length) according to one embodiment of the present invention. Curve 1410 shows the S-parameters S 11 and curve 1420 represents the S-parameter S 21 and curve 1430 represents the S-parameter S 31 , and curve 1440 represents the phase difference between port P2 and port P3. Points 1401 and 1402 are the intersections of the three curves at -5 dB, and points 1403 and 1404 are the values ​​of curve 1410 at -10 dB. Referring to points 1401 and 1402, the effective operating band of the four-layer rat-race coupler is between about 15 GHz and 31 GHz, and the phase error is only about 0.5 degrees. Referring to points 1403 and 1404, the S-parameter S of the four-layer rat-race coupler in the frequency band of 15.5 GHz to 30.5 GHz is 11 has good gain characteristics.

[0060] FIG. 15 is a graph showing the simulation of S-parameters of a four-layer rat-race coupler with n=m=k=1.5 (e.g., rat-race coupler 400 having strip conductors 23, 24, 33, 34, 43, and 44 with electrical lengths of 3 / 4) according to one embodiment of the present invention, where curve 1510 is the S-parameter S 11 and curve 1520 represents the S-parameter S21 and curve 1530 represents the S-parameter S 31 , and curve 1540 represents the phase difference between port P2 and port P3. Points 1501 and 1502 are the intersections of the three curves at -5 dB, and points 1503, 1504, 1505, and 1506 are the values ​​of curve 1510 at -10 dB. Referring to points 1501 and 1502, the effective operating band of the four-layer rat-race coupler is between about 20 GHz and 26 GHz, and the phase error is only about 0 degrees. Referring to points 1503, 1504, 1505, and 1506, the S-parameter S of the four-layer rat-race coupler is 11 has good gain characteristics.

[0061] FIG. 16 is a graph showing the simulation of S-parameters of a four-layer rat-race coupler with n=m=k=2 (e.g., rat-race coupler 400 having strip conductors 23, 24, 33, 34, 43, and 44 with an electrical length of 1) according to one embodiment of the present invention, where curve 1610 is the S-parameter S 11 and curve 1620 represents the S-parameter S 21 and curve 1630 represents the S-parameter S 31 , and curve 1640 represents the phase difference between port P2 and port P3. Points 1601 and 1602 are the intersections of the three curves at -5 dB, and points 1603 and 1604 are the values ​​of curve 1610 at -10 dB. Referring to points 1601 and 1602, the effective operating band of the four-layer rat-race coupler is between about 16.5 GHz and 30.5 GHz, and the phase error is only about 0 degrees. Referring to points 1603 and 1604, the S-parameter S of the four-layer rat-race coupler in the frequency band of 18.5 GHz to 29 GHz is 11 has good gain characteristics.

[0062] FIG. 17 is a simulation diagram of the S-parameters of a seven-layer rat-race coupler with n=m=k=1 according to one embodiment of the present invention. Curve 1710 shows the S-parameters S 11 and curve 1720 represents the S-parameter S 21and curve 1730 represents the S-parameter S 31 , and curve 1740 represents the phase difference between port P2 and port P3. Points 1701 and 1702 are the intersections of the three curves at -5 dB, and points 1703 and 1704 are the values ​​of curve 1710 at -10 dB. Referring to points 1701 and 1702, the effective operating band of the seven-layer rat-race coupler is between about 14.5 GHz and 31.5 GHz, and the phase error is only about 0 degrees. Referring to points 1703 and 1704, the S-parameter S of the seven-layer rat-race coupler in the frequency band 15.5 GHz to 30.5 GHz is 11 has good gain characteristics. Figures 13 to 17 show that compared with the four-layer rat-race coupler, the seven-layer rat-race coupler does not have significant improvements in gain characteristics and phase error within the effective operating band. Therefore, when designing a circuit, users can consider using a lower-cost four-layer rat-race coupler to replace the seven-layer rat-race coupler.

[0063] FIG. 18 is a simulation diagram of the S-parameters of a three-layer rat-race coupler with n=1 and m=2 according to one embodiment of the present invention (e.g., rat-race coupler 300 having strip conductors 23 and 24 with an electrical length of 1 / 2 and strip conductors 33 and 34 with an electrical length of 1). Curve 1810 is the S-parameter S 11 and curve 1820 represents the S-parameter S 21 and curve 1830 represents the S-parameter S 31 , and curve 1840 represents the phase difference between port P2 and port P3. Points 1801 and 1802 are the intersections of the three curves at -5 dB, and points 1803 and 1804 are the values ​​of curve 1810 at -10 dB. Referring to points 1801 and 1802, the effective operating band of the three-layer rat-race coupler is between about 16 GHz and 30 GHz, and the phase error is only about 0 degrees. Referring to points 1803 and 1804, the S-parameter S of the three-layer rat-race coupler in the frequency band 19 GHz to 27 GHz is 11 has good gain characteristics.

[0064] FIG. 19 is a simulation diagram of the S-parameters of a three-layer rat-race coupler with n=2 and m=1 according to one embodiment of the present invention (e.g., rat-race coupler 300 having strip conductors 23 and 24 with an electrical length of 1 and strip conductors 33 and 34 with an electrical length of 1 / 2). Curve 1910 represents the S-parameters S 11 and curve 1920 represents the S-parameter S 21 and curve 1930 represents the S-parameter S 31 , and curve 1940 represents the phase difference between port P2 and port P3. Points 1901 and 1902 are the intersections of the three curves at -5 dB, and points 1903 and 1904 are the values ​​of curve 1910 at -10 dB. Referring to points 1901 and 1902, the effective operating band of the three-layer rat-race coupler is between about 17 GHz and 29 GHz, and the phase error is only about 0 degrees. Referring to points 1903 and 1904, the S-parameter S of the three-layer rat-race coupler in the frequency band 19 GHz to 27 GHz is 11 has good gain characteristics.

[0065] 5 to 16 and 18 to 19, it can be seen that when the electrical lengths of strip conductors 23, 24, 33, 34, and 43 meet a specific standard, the rat-race coupler not only has an extremely small phase error, but also has a wider effective operating bandwidth. Specifically, when n, m, or k is an even number, the rat-race coupler provided by the present invention can achieve both a low phase error and a wide effective operating bandwidth.

[0066] It should be noted that the impedance of each conductor in a rat-race coupler (e.g., 100, 200, 300, or 400) can be adjusted by the user as needed, and the present invention is not limited thereto. Taking the three-layer rat-race coupler 300 as an example, in one embodiment, in annular conductor #1 of rat-race coupler 300, the impedance of strip conductor 11 is 70 ohms, the impedance of strip conductor 12 is 30 ohms, and the impedance of strip conductors 13 and 14 is 60 ohms. In band-adjusting section #2, the impedance of strip conductor 22 is 35 ohms, and the impedance of strip conductors 23 and 24 is 77 ohms. In band-adjusting section #3, the impedance of strip conductor 32 is 40 ohms, and the impedance of strip conductors 33 and 34 is 85 ohms. The S-parameters of rat-race coupler 300 with the above impedance configuration are shown in FIG. 20.

[0067] FIG. 20 is a simulation diagram of the S-parameters of a three-layer rat-race coupler 300 with n=m=0.5 according to one embodiment of the present invention, where curve 2010 is the S-parameter S 11 and curve 2020 represents the S-parameter S 21 and curve 2030 represents the S-parameter S 31 , and curve 2040 represents the phase difference between port P2 and port P3. Points 2001 and 2002 are the intersections of the three curves at -5 dB, and points 2003 and 2004 are the values ​​of curve 2010 at -10 dB. Referring to points 2001 and 2002, the effective operating band of rat-race coupler 300 is between approximately 17.2 GHz and 28.8 GHz, and the phase error is only approximately 0.4 degrees. Referring to points 2003 and 2004, the S-parameter S of rat-race coupler 300 in the frequency band of 18 GHz to 28 GHz is 11 has good gain characteristics.

[0068] In summary, the present invention provides a multi-layer rat-race coupler by combining a ring conductor and one or more band-adjusting sections, and the band-adjusting sections can include strip conductors with specific lengths. Compared with conventional rat-race couplers, the rat-race coupler of the present invention provides two output signals with a smaller phase error.

[0069] Finally, it should be noted that the above embodiments are only used to explain the technical solutions of the present invention, and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that modifications can still be made to the technical solutions described in the above embodiments, or equivalent replacements can be made for some or all of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. [Industrial Applicability]

[0070] The present invention provides a rat-race coupler that can reduce the phase error between the two output signals of the rat-race coupler. [Explanation of symbols]

[0071] 100, 200, 300, 400: Rat Race Coupler 11, 12, 13, 14, 22, 23, 24, 32, 33, 34, 42, 43, 44: Strip conductors 51, 52, 61, 62, 63, 64, 71, 72, 81, 82, 83, 84, 91, 92, 93, 94, 1001, 1002, 1003, 1004, 1101, 1102, 1103, 1104, 1201, 1202, 1203, 1204, 1301, 1302, 1303, 1304, 1305, 1306, 1401, 1402, 1403, 1404, 1405, 1406, 1407, 1408, 1409, 1410, 1411, 1412, 1413, 1414, 1415, 1416, 1417, 1418, 1419, 1420, 1421, 1422, 1423, 1424, 1425, 1426, 1427, 1428, 1429, 1430, 1431, 1432, 1433, 1434, 1435, 1436, 1437, 1438, 1439, 1440, 1441, 1442, 1443, 1444, 1445, 1446, 1447, 1448, 1449, 1450, 1451, 1452, 1453, 1454, 1455, 1456, 14 402, 1403, 1404, 1501, 1502, 1503, 1504, 1505, 1506, 1601, 1602, 1603, 1604, 1701, 170 2, 1703, 1704, 1801, 1802, 1803, 1804, 1901, 1902, 1903, 1904, 2001, 2002, 2003, 2004: points 510, 520, 530, 540, 610, 620, 630, 640, 710, 720, 730, 740, 810, 820, 830, 840, 910, 920, 930, 940, 1010, 1020, 1030, 1040, 1110, 1120, 1130, 1140, 1210, 1220, 1230, 1240, 1310, 1320, 1 330, 1340, 1410, 1420, 1430, 1440, 1510, 1520, 1530, 1540, 1610, 1620, 1630, 1640, 1710, 1 720, 1730, 1740, 1810, 1820, 1830, 1840, 1910, 1920, 1930, 1940, 2010, 2020, 2030, 2040: Curve P1, P2, P3, P4: Ports #1: Ring conductor #2, #3, #4: Bandwidth adjustment section

Claims

1. an annular conductor including a first strip conductor having a first terminal and a second terminal, a second strip conductor having a third terminal and a fourth terminal, a third strip conductor, and a fourth strip conductor, wherein the first terminal is connected to the third terminal through the third strip conductor, and the second terminal is connected to the fourth terminal through the fourth strip conductor; a first band adjusting unit including a fifth band conductor, a sixth band conductor, and a seventh band conductor having a fifth terminal and a sixth terminal, the fifth terminal being connected to the third terminal through the fifth band conductor, and the sixth terminal being connected to the fourth terminal through the sixth band conductor; a first port connected to the fifth terminal; a second port connected to the first terminal; a third port connected to the second terminal; an electrical length from the first terminal to the second terminal through the first strip conductor, an electrical length from the third terminal to the fourth terminal through the second strip conductor, and an electrical length from the fifth terminal to the sixth terminal through the seventh strip conductor are all substantially 1 / 2; an electrical length from the first terminal to the third terminal through the third strip conductor and an electrical length from the second terminal to the fourth terminal through the fourth strip conductor are both substantially ¼; a rat-race coupler in which the electrical length from the third terminal to the fifth terminal through the fifth band conductor and the electrical length from the fourth terminal to the sixth terminal through the sixth band conductor are both substantially n / 2, where n is a natural number.

2. 2. The rat race coupler of claim 1, wherein n is an even number.

3. 2. The rat-race coupler of claim 1, further comprising a fourth port connected to a center of the first strip conductor.

4. 2. The rat-race coupler of claim 1, wherein the first port, the second port, and the third port are used to connect to at least one external system having a load impedance, the impedance of the second band conductor is 1.2 times the load impedance, the impedance of the seventh band conductor is 0.8 times the load impedance, and the impedances of the fifth and sixth band conductors are both 2.8 times the load impedance.

5. 4. The rat-race coupler according to claim 1, further comprising a second band adjustment section including an eighth band conductor, a ninth band conductor, and a tenth band conductor having a seventh terminal and an eighth terminal, the seventh terminal being connected to the fifth terminal through the eighth band conductor, the eighth terminal being connected to the sixth terminal through the ninth band conductor, and the first port being connected to the seventh terminal and to the fifth terminal through the eighth band conductor.

6. 6. The rat-race coupler of claim 5, wherein the first port, the second port, and the third port are used to connect to at least one external system having a load impedance, the impedance of the tenth band conductor is 0.8 times the load impedance, the impedance of the seventh band conductor is 1.4 times the load impedance, and the impedances of the fifth band conductor, the sixth band conductor, the eighth band conductor, and the ninth band conductor are 2.8 times the load impedance.

7. 6. The rat race coupler of claim 5, wherein the electrical length from the seventh terminal through the tenth band conductor to the eighth terminal is substantially 1 / 2, and the electrical length from the fifth terminal through the eighth band conductor to the seventh terminal and the electrical length from the sixth terminal through the ninth band conductor to the eighth terminal are both substantially m / 2, where m is a natural number.

8. 8. The rat race coupler of claim 7, wherein m is an even number.

9. 8. The rat race coupler of claim 7, wherein m and n are equal.

10. 6. The rat-race coupler according to claim 5, further comprising a third band adjustment section including an eleventh band conductor, a twelfth band conductor, and a thirteenth band conductor having a ninth terminal and a tenth terminal, the ninth terminal being connected to the seventh terminal through the eleventh band conductor, the tenth terminal being connected to the eighth terminal through the twelfth band conductor, and the first port being connected to the ninth terminal and to the fifth terminal through the eleventh and eighth band conductors.

11. 11. The rat-race coupler of claim 10, wherein the first port, the second port, and the third port are used to connect to at least one external system having a load impedance, the impedance of the seventh and tenth band conductors is 1.4 times the load impedance, the impedance of the thirteenth band conductor is 0.8 times the load impedance, and the impedance of the fifth, sixth, eighth, ninth, eleventh, and twelfth band conductors is 2.8 times the load impedance.

12. 11. The rat-race coupler of claim 10, wherein the electrical length from the ninth terminal through the thirteenth band conductor to the tenth terminal is substantially 1 / 2, and the electrical length from the seventh terminal through the eleventh band conductor to the ninth terminal and the electrical length from the eighth terminal through the twelfth band conductor to the tenth terminal are both substantially k / 2, where k is a natural number.

13. 13. The rat race coupler of claim 12, wherein k is an even number.

14. 13. The rat race coupler of claim 12, wherein k, m and n are equal.

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