CROSS REFERENCE TO RELATED APPLICATIONS

This application is a no-provisional of Application Ser. No. 62/642,066, filed Mar. 13, 2018, which is hereby incorporated by this reference in its entirety.

BACKGROUND OF THE INVENTION

Field

The present invention relates to wireless communications, and more particularly, to antennas that employ integrated phase shifters.

Related Art

Cellular antennas typically have a Remote Electrical Tilt (RET) mechanism that provides a controlled phase delay differential between antenna dipoles (or dipole clusters) along a vertical axis. In doing so, the RET mechanism enables tilting the antenna gain pattern along the vertical axis, which has the effect of sweeping the gain pattern toward or away from the cell tower on which the antenna is mounted. This allows a network operator to expand or contract the antenna's gain pattern, which may be important for controlling cellular coverage and preventing interference with the gain patterns nearby antennas. RET devices typically employ one or more phase shifters to perform this function.

FIG. 1illustrates a conventional phase shifter100. Phase shifter100comprises an outer conductive trace105, an inner conductive trace110, and a reference conductive trace120. Phase shifter100further comprises a wiper arm125, which includes a wiper arras trace130, an inner wiper arm capacitive contact135, and an outer wiper arm capacitive contact140. Reference conductive trace120is electrically coupled to wiper arm trace130via pivot point contact115. Reference conductive trace120is coupled to an RF signal input at Port 1, and to phase reference port (or middle port) at Port 4. Further illustrated inFIG. 1is wiper arm motor145, which in a conventional phase shifter100must be powered by a standalone DC signal input150.

FIG. 2illustrates a how a phase shifter may be employed in a RET system to control the tilt of a cellular antenna gain pattern. Illustrated inFIG. 2is an antenna array face200having a plurality of dipole sets210arranged along a vertical axis. Further illustrated a phase shifter, with Ports 1-6. Port 1 may be coupled to an RF signal input source, and the remaining Ports 2-6 are coupled to a respective dipole set210via corresponding signal lead202-206.

FIG. 2provides a very simplified depiction of three exemplary antenna gain patterns220a,220b, and220c. According to the principles of an antenna phase shifter, the angle of wiper arm125imparts different phase changes to the RF signal from RF signal input at Port 1 to each of ports 2, 3, 5, and 6. The phase at Port 4 (the phase reference port) remains unchanged. The differential phase shifts imparted on the RF signal as a function of Port results in a tilting of the antenna gain pattern such that a given position of wiper arm125corresponds to a specific tilt angle of the antenna gain pattern.

One disadvantage of conventional phase shifter100is that it requires a separate dedicated DC power line to drive wiper arm motor145. One solution to this is to integrate a Bias-T circuit into the phase shifter so that, given a combined RF and DC signal at the RF signal source, and split off a portion of that DC signal to dedicate it to driving the wiper arm motor.

FIG. 3illustrates another conventional phase shifter300, which incorporates a Bias-T circuit305, which splits a portion of the DC signal to drive wiper arm motor145. This solution creates two problems. First, a portion of the DC signal remains with the RF signal that is applied to the phase reference Port 4. One solution to this is to add an additional DC block to either side of Port 4. This adds complexity and cost to phase shifter300, and increases the real estate taken up on an array antenna. Second, by splitting the DC signal, less power is available to wiper arm motor145, and power is wasted at the DC block that might otherwise be channeled to wiper arm motor145.

FIG. 4illustrates a conventional wiper arm pivot point115. As illustrated, the input signal from input at port 1, coupled via reference conductive trace120, is directly coupled to wiper arm pivot point115and middle port trace410, which is directly coupled to reference port 4. Accordingly, the DC portion of the input signal is directly coupled to Bias-T305and reference port 4.

Accordingly, what is needed is a phase shifter that more efficiently powers its wiper arm motor, with fewer additional components, while providing RF signals to ports 2-6 with minimal insertion loss.

SUMMARY OF THE INVENTION

An aspect of the present invention involves a phase shifter for an antenna. The phase shifter comprises an outer conductive trace, an inner conductive trace, a wiper arm having a wiper arm conductive trace wherein the wiper arm has a pivot point, and a capacitive coupler. The capacitive coupler capacitively couples the input port to a phase reference port to provide DC blocking to the phase reference port.

