Low-loss, low-profile digital-analog phase shifter
A phase shifter having both digital and analog shifting components is disclosed. The digital-analog phase shifter includes an input/output port configured, in part, for receiving an input radio frequency (RF) signal from an external source and outputting a phase shifted RF signal. A digital shifter performs coarse phase shifts of the input RF signal, while an analog shifter variably shift the phase of the input RF signal relative to the coarse phase shift. This produces a phase shifted RF signal having a total phase range that is output is continuously variable from 0° to 360°.
1. A method comprising:
receiving an input radio frequency (RF) signal from an external source, at an input/output port;
performing coarse phase shifts of the input RF signal using a digital shifter;
variably shifting the phase of the input RF signal within a predetermined range, relative to the coarse phase shift, to produce the phase shifted RF signal using an analog shifter; and
outputting a phase shifted RF signal through the input/output port,
wherein the total phase range of the phase shifted RF signal that is output is continuously variable from 0° to 360°.
2. The method of claim 1 , wherein the digital shifter comprises a two bit digital shifter configured to provide four discrete states corresponding to four coarse phase shifts.
3. The method of claim 2 , wherein performing coarse phase shifts comprises:
providing four phase delay loads for shifting the phase of the input RF signal by preset values; and
engaging pairs of the phase delay loads to selectively impart one of the four coarse phase shifts to the input RF signal.
4. The method of claim 3 , wherein:
the first phase delay load is λ/16;
the second phase delay load is λ/16;
the third phase delay load is 3λ/16; and
the fourth phase delay load is 5λ/16,
where λ=360°.
5. The method of claim 1 , wherein:
the analog shifter comprises a varactor; and
variably shifting comprises supplying an input voltage to variably control capacitance of the varactor.
6. The method of claim 1 , wherein a total loss of the phase shifted RF signal is between 0 dB and −3.6 dB.
7. An apparatus comprising:
an input/output port configured, in part, for receiving an input radio frequency (RF) signal from an external source and outputting a phase shifted RF signal;
a digital shifter for performing coarse phase shifts of the input RF signal; and
an analog shifter for variably shifting the phase of the input RF signal within a predetermined range, relative to the coarse phase shift, to produce the phase shifted RF signal,
wherein the total phase range of the phase shifted RF signal that is output is continuously variable from 0° to 360°.
8. The apparatus of claim 7 , wherein the digital shifter comprises a two bit digital shifter configured to provide four discrete states corresponding to four coarse phase shifts.
9. The apparatus of claim 8 , wherein the two bit digital shifter comprises:
four phase delay loads for shifting the phase of the input RF signal by preset values; and
a plurality of switching elements for engaging pairs of the phase delay loads to selectively impart one of the four coarse phase shifts.
10. The apparatus of claim 9 , wherein:
the first phase delay load is λ/16 transmission line;
the second phase delay load is λ/16 transmission line;
the third phase delay load is 3λ/16 transmission line; and
the fourth phase delay load is 5λ/16 transmission line,
where λ=360°.
11. The apparatus of claim 7 , wherein the analog shifter comprises:
a varactor; and
a voltage controller for supplying an input voltage to variably control capacitance of the varactor.
12. The apparatus of claim 7 , wherein the analog shifter variably shifts the phase of the input RF signal ±40° to ±50° from the coarse phase shift performed by the digital shifter.
13. The apparatus of claim 7 , wherein a total loss of the phase shifted RF signal is between 0 dB to −3.6 dB.