Low passive intermodulation chokes for electrical cables
This disclosure relates to chokes for suppressing undesired signals such as such as common mode electromagnetic interference (EMI) and/or radio frequency interference (RFI). The chokes can include an electro-conductive sleeve disposed over an electrical cable and the sleeve can be configured to suppress an undesired signal. In some embodiments, the electro-conductive sleeve and have a half-wave sleeve, which can be electrically open at both ends. Additional insulating material can be included between the electrical cable and the sleeve. Multiple electro-conductive sleeves and be disposed substantially concentrically over the cable. The chokes can be configured to reduce passive intermodulation (PIM). The sleeve can have a longitudinal slot that extends the length of the sleeve. The sleeve can include multiple slots that separate the sleeve into multiple panels, which can be configured to suppress different signals.
1. A cellular antenna array comprising:
at least two antenna sub-arrays, wherein each of the at least two antenna sub-arrays comprises at least two antenna elements;
a splitting module configured to couple the at least two antenna sub-arrays to at least one feed line;
at least two electrical cables coupling the splitting module to the at least two antenna sub-arrays;
wherein each of the at least two electrical cables has a first choke at or near a first end of the electrical cable and a second choke at or near a second end of the electrical cable;
wherein each of the first and second chokes is configured to suppress undesired radiofrequency (RF) current, each of the first and second chokes are configured to exhibit low passive intermodulation (PIM), each of the first and second chokes comprising:
a first electro-conductive sleeve disposed over an outer surface of the corresponding electrical cable, wherein a first longitudinal slot is disposed between ends of the first electro-conductive sleeve, and wherein the first longitudinal slot extends the full longitudinal length of the first electro-conductive sleeve;
a second electro-conductive sleeve disposed over the first electro-conductive sleeve, wherein a second longitudinal slot is disposed between ends of the second electro-conductive sleeve, and wherein the second longitudinal slot extends the full longitudinal length of the second electro-conductive sleeve; and
an insulating layer disposed between the first electro-conductive sleeve and the second electro-conductive sleeve;
wherein the first electro-conductive sleeve and the second electro-conductive sleeve are insulated from the electrical cable.
2. The cellular antenna array of claim 1 , wherein the second electro-conductive sleeve has a length that is shorter than the first electro-conductive sleeve.
3. The cellular antenna array of claim 1 , further comprising additional insulating material disposed between the first electro-conductive sleeve and an insulating outer jacket of the electrical cable.
4. The cellular antenna array of claim 1 , wherein the ends of the first electro-conductive sleeve overlap such that an area near a second end is disposed over an area near a first end.
5. The cellular antenna array of claim 4 , wherein an insulating material is disposed between the area near the first end and the area near the second end.
6. The cellular antenna array of claim 4 , wherein the area near the first end and the area near the second end are capacitively coupled.
7. The cellular antenna array of claim 1 , further comprising
a radiating component coupled to one of the at least two electrical cables, the radiating component configured to emit energy; and
a shield member disposed over the radiating component, the shield member configured to suppress at least some of the energy emitted by the radiating component;
wherein one of the first and second chokes is coupled to the shield member such that positioning the shield member over the radiating component causes the choke to be disposed over the electrical cable.
8. The cellular antenna array of claim 7 , wherein the choke that is coupled to the shield member is electrically insulated from the shield member.
9. The cellular antenna array of claim 1 , wherein at least one of the first electro-conductive sleeve and the second electro-conductive sleeve is a half-wave sleeve.
10. The cellular antenna array of claim 1 , wherein at least one of the first and second chokes further comprises additional insulating material disposed between an insulating outer jacket of the electrical cable and the first electro-conductive sleeve, wherein the additional insulating material is configured to increase suppression of EMI and/or RFI by the choke.
11. The cellular antenna array of claim 10 , wherein the electrical cable has a radius and wherein the additional insulating material has a thickness of about 25% to about 200% of the radius of the electrical cable.
12. The cellular antenna array of claim 10 , wherein the electrical cable has a radius and wherein the additional insulating material has a thickness of about 50% to about 100% of the radius of the electrical cable.
13. The cellular antenna array of claim 1 , wherein the first electro-conductive sleeve is not shorted, and wherein the second electro-conductive sleeve is not shorted.