Systems and methods for using a phase locked loop (PLL) to provide multiple output signals
A phase locked loop (PLL) provides output signals at multiple frequencies. In particular, the PLL includes a phase detector and two voltage controlled oscillators (VCOs). One of the VCOs is selectively enabled depending on a desired output signal. The phase detector receives a reference signal and a feedback signal from the enabled one of the two VCOs. The phase detector outputs a control signal that controls the VCO that provided the feedback signal.
1. A wireless distribution system (WDS), comprising:
a plurality of remote units comprising a transceiver comprising a phase locked loop (PLL) comprising:
a phase detector configured to:
receive a reference input signal and one of two feedback signals; and
output a control signal;
a first voltage controlled oscillator (VCO) configured to:
receive the control signal and output a first one of the two feedback signals; and
receive a first enable signal that activates the first VCO; and
a second VCO configured to:
receive the control signal and output a second one of the two feedback signals; and
receive a second enable signal that activates the second VCO such that only one of the first VCO and the second VCO are active at a time; and
a central unit coupled to the plurality of remote units via a plurality of optical fiber-based communications media, respectively, and configured to:
distribute a plurality of downlink optical communications signals to the plurality of remote units via the plurality of optical fiber-based communications media, respectively;
receive a plurality of uplink communications signals from the plurality of remote units via the plurality of optical fiber-based communications media, respectively; and
generate a plurality of communications signals based on the plurality of uplink communications signals, wherein each of the plurality of communications signals corresponds to a signal channel and a remote unit among the plurality of remote units communicating on the signal channel.
2. The WDS of claim 1 , wherein each remote unit comprises at least one electrical-to-optical converter.
3. The WDS of claim 2 , wherein the PLL further comprises a loop filter.
4. The WDS of claim 2 , wherein the first VCO comprises a voltage controlled crystal oscillator.
5. The WDS of claim 2 , wherein the HEU is further configured to:
receive a plurality of radio frequency (RF) downlink communications signals;
convert the plurality of RF downlink communications signals into a plurality of optical downlink communications signals, respectively;
distribute the plurality of optical downlink communications signals to the plurality of remote units via the plurality of optical fiber-based communications media, respectively;
receive a plurality of optical uplink communications signals from the plurality of remote units via the plurality of optical fiber-based communications media, respectively; and
convert the plurality of optical uplink communications signals into a plurality of RF uplink communications signals, respectively.
6. The WDS of claim 5 , wherein the plurality of remote units is further configured to:
receive the plurality of optical downlink communications signals via the plurality of optical fiber-based communications media, respectively;
convert the plurality of optical downlink communications signals into the plurality of RF downlink communications signals, respectively;
receive the plurality of RF uplink communications signals;
convert the plurality of RF uplink communications signals into the plurality of optical uplink communications signals, respectively; and
provide the plurality of optical uplink communications signals to the central unit via the plurality of optical fiber-based communications media, respectively.
7. A wireless distribution system (WDS), comprising:
at least one remote unit comprising a transceiver comprising a phase locked loop (PLL) comprising:
a phase detector configured to:
receive a reference input signal and one of two feedback signals; and
output a control signal;
a first voltage controlled oscillator (VCO) configured to:
receive the control signal and output a first one of the two feedback signals; and
receive a first enable signal that activates the first VCO; and
a second VCO configured to:
receive the control signal and output a second one of the two feedback signals; and
receive a second enable signal that activates the second VCO such that only one of the first VCO and the second VCO are active at a time;
a central unit coupled to the at least one remote unit via a plurality of optical fiber-based communications media, respectively, and configured to:
distribute a plurality of downlink communications signals to the plurality of remote units via the plurality of optical fiber-based communications media, respectively;
receive a plurality of uplink communications signals from the at least one remote unit via the plurality of optical fiber-based communications media, respectively; and
generate a plurality of communications signals; and
a signal processing circuit comprising a signal input communicatively coupled to a plurality of signal sources, respectively.
8. The WDS of claim 7 , wherein each remote unit comprises at least one electrical-to-optical converter.
9. The WDS of claim 8 , wherein the PLL further comprises a loop filter.
10. The WDS of claim 8 , wherein the first VCO comprises a voltage controlled crystal oscillator.
11. The WDS of claim 8 , wherein the central unit is further configured to:
receive a plurality of radio frequency (RF) downlink communications signals;
convert the plurality of RF downlink communications signals into a plurality of optical downlink communications signals, respectively;
distribute the plurality of optical downlink communications signals to the at least one remote unit via the plurality of optical fiber-based communications media, respectively;
receive a plurality of optical uplink communications signals from the at least one remote unit via the plurality of optical fiber-based communications media, respectively; and
convert the plurality of optical uplink communications signals into a plurality of RF uplink communications signals, respectively.
12. The WDS of claim 11 , wherein the at least one remote unit is further configured to:
receive the plurality of optical downlink communications signals via the plurality of optical fiber-based communications media, respectively;
convert the plurality of optical downlink communications signals into the plurality of RF downlink communications signals, respectively;
receive the plurality of RF uplink communications signals;
convert the plurality of RF uplink communications signals into the plurality of optical uplink communications signals, respectively; and
provide the plurality of optical uplink communications signals to the central unit via the plurality of optical fiber-based communications media, respectively.
13. A wireless distribution system (WDS), comprising:
a plurality of remote units comprising a transceiver comprising a phase locked loop (PLL) comprising:
a phase detector configured to:
receive a reference input signal and one of two feedback signals; and
output a control signal;
a first voltage controlled oscillator (VCO) configured to:
receive the control signal and output a first one of the two feedback signals; and
receive a first enable signal that activates the first VCO; and
a second VCO configured to:
receive the control signal and output a second one of the two feedback signals; and
receive a second enable signal that activates the second VCO such that only one of the first VCO and the second VCO are active at a time; and
a central unit, the central unit coupled to the plurality of remote units via a plurality of optical fiber-based communications media, respectively, and configured to:
distribute a plurality of downlink communications signals to the plurality of remote units via the plurality of optical fiber-based communications media, respectively; and
receive a plurality of uplink communications signals from the plurality of remote units via the plurality of optical fiber-based communications media, respectively.
14. The WDS of claim 13 , wherein each remote unit comprises at least one electrical-to-optical converter.
15. The WDS of claim 14 , wherein the central unit is further configured to generate a plurality of communications signals based on the plurality of uplink communications signals, wherein each of the plurality of communications signals corresponds to a signal channel and a remote unit among the plurality of remote units communicating on the signal channel.
16. The WDS of claim 15 , wherein the PLL further comprises a loop filter.
17. The WDS of claim 15 , wherein the first VCO comprises a voltage controlled crystal oscillator.
18. The WDS of claim 15 , wherein the central unit is further configured to:
receive a plurality of radio frequency (RF) downlink communications signals;
convert the plurality of RF downlink communications signals into a plurality of optical downlink communications signals, respectively; and
distribute the plurality of optical downlink communications signals to the plurality of remote units via the plurality of optical fiber-based communications media, respectively.