RF combining device and method
View Patent ↗Two or more reflective isolator elements are joined at their outputs to produce an RF combining structure. An RF circulator element is used for each input RF signal as a reflective isolator element to provide a different phase delay according to the direction of propagation of the RF wave. The output of the reflective isolator elements thus exhibits a high output impedance, when looking into the RF output port, preventing back propagation of signals from one input port to another.
1. A combiner element comprising:
an input;
a first arm having a length, the first arm coupled to an output;
a second arm coupled to the output having a first path with a first length for signals traveling from the input to the output and a second path with a second length for signals traveling toward the input from the output, wherein the second length is an odd multiple of ½ wavelength different from the first length.
2. The combiner element of claim 1 wherein the first arm and the second arm are impedance matched.
3. The combiner element of claim 1 wherein the lengths are selected as a function of a selected RF frequency.
4. The combiner element of claim 1 wherein the second arm comprises a circulator that passes signals on the first path between the input and output, and directs signals propagating toward the input to a short.
5. The combiner element of claim 4 wherein the circulator directs signals from the short along the second path toward the input.
6. The combiner element of claim 1 wherein the first arm has a length of ½λ and wherein the first path of the second arm has a length of ½λ.
7. The combiner element of claim 6 wherein the second path of the second arm has a length of ¾λ.
8. A RF combiner comprising:
multiple inputs and an output; and
a reflective element coupled between each input and the output, each reflective element comprising:
a first arm having a length, the first arm coupled to the output;
a second arm coupled to the output having a first path with a first length for signals traveling from the input to the output and a second path with a second length for signals traveling toward the input from the output, wherein the second length is an odd multiple of ½ wavelength different from the first length.
9. The RF combiner of claim 8 wherein each reflective element comprises a circulator in the second arm.
10. The combiner element of claim 8 wherein the first arm and the second arm are impedance matched.
11. The combiner element of claim 8 wherein the lengths are selected as a function of a selected RF frequency.
12. The combiner element of claim 8 wherein the second arm comprises a circulator that passes signals on the first path between the input and output, and directs signals propagating toward the input to a short.
13. The combiner element of claim 12 wherein the circulator directs signals from the RF short circuit along the second path toward the input.
14. The combiner element of claim 8 wherein the first arm has a length of ½λ and wherein the first path of the second arm has a length of ½λ.
15. The combiner element of claim 14 wherein the second path of the second arm has a length of ¾λ.
16. A method comprising:
dividing an RF signal into a first arm and a second arm;
providing two different paths for RF signals in the second arm, wherein a first forward path has a length equal to the length of the first arm, and wherein a second backward path has a length ½λ different from the length of the first arm.
17. The method of claim 16 and further comprising coming multiple input RF signals in the same manner.
18. The method of claim 16 wherein a circulator is used to direct the RF signals on respective forward and backward paths in the second arm.
19. The method of claim 18 wherein the circulator directs backward RF signals to a RF short.
20. The method of claim 19 wherein the RF short is coupled to the circulator by a line of length ¼λ.