Tunable radio frequency (RF) equalizer
View Patent ↗A radio frequency (RF) equalizer includes a coupler including an input port, an output port, a coupling port, and an isolation port; a combination circuit including; a coupling node electrically coupled to the coupling port; a first digitally controlled capacitor (DTC) connected between the coupling node and ground; a resistor connected between the coupling node and ground for controlling a quality factor (Q) of resonance of the equalizer; an isolation node coupled to the isolation port; and a second DTC connected between the isolation node and ground. A system and a method of operation are provided.
1. An equalizing system, comprising:
a wireless communication system for receiving at least one service, the wireless communication system comprising a plurality of optical fiber cables and a plurality of remote units connected by the optical fiber cables, the plurality of remote units being distributed over a deployment site, at least one service being routed to the plurality of remote units; and
a RF equalizer comprising:
a coupler comprising an input port, an output port, a coupling port, and an isolation port; and
a combination circuit, comprising:
a coupling node electrically coupled to the coupling port;
a first digitally tunable capacitor (DTC) connected between the coupling node and ground;
a resistor connected between the coupling node and ground that controls a quality factor of resonance;
an isolation node coupled to the isolation port; and
a second DTC, wherein
one of the first DTC and the second DTC is configured as a coarse DTC and the other one of the first DTC and the second DTC is configured as a fine DTC.
2. The equalizing system of claim 1 , wherein the coarse DTC provides wide tuning equalization and the fine DTC provides narrow tuning equalization.
3. The equalizing system of claim 2 , wherein the coupler is a directional coupler.
4. The equalizing system of claim 2 , wherein each of the first DTC and the second DTC is controlled by a digital serial peripheral interface bus.
5. The equalizing system of claim 1 , wherein limiting flow of current across the first DTC affects the quality factor of the resonance of the first DTC and the resistor.
6. The equalizing system of claim 5 , wherein a lower resistance of the resistor reduces an amount of equalizer correction in a given frequency range and a higher resistance increases an amount of the equalizer correction in a given frequency range.
7. The equalizing system of claim 1 , further comprising a second coupler comprising a second input port coupled to the input port, a second output port, a second coupling port, and a second isolation port.
8. The equalizing system of claim 7 , further comprising a second combination circuit, comprising:
a second coupling node electrically coupled to the second coupling port;
a third DTC connected between the second coupling node and ground;
a second resistor connected between the second coupling node and the ground for controlling a quality factor of a second resonance;
a second isolation node coupled to the second isolation port; and
a fourth DTC connected between the second isolation node and the ground.
9. An equalizing system, comprising:
a wireless communication system for receiving at least one service from at least one source, the wireless communication system comprising:
a head end unit;
a plurality of optical fiber cables; and
a plurality of remote units connected to the head end unit by the optical fiber cables, the plurality of remote units being distributed over a deployment site, the head end unit being configured for routing the at least one service to the plurality of remote units; and
a RF equalizer comprising:
a coupler comprising an input port, an output port, a coupling port, and an isolation port; and
a combination circuit, comprising:
a coupling node electrically coupled to the coupling port;
a first DTC connected between the coupling node and ground;
a resistor connected between the coupling node and ground that controls a quality factor of resonance;
an isolation node; and
a second DTC connected between the isolation node and ground.
10. The equalizing system of claim 9 , wherein the remote units are deployed over multiple floors at the deployment site.
11. The equalizing system of claim 10 , wherein one of the first DTC and the second DTC is configured as a coarse DTC and the other one of the first DTC and the second DTC is configured as a fine DTC.
12. The equalizing system of claim 11 , wherein the coarse DTC provides wide tuning equalization and the fine DTC provides narrow tuning equalization.
13. The equalizing system of claim 11 , wherein each of the first DTC and the second DTC is controlled by a digital serial peripheral interface bus.
14. The equalizing system of claim 11 , wherein limiting flow of current across the first DTC affects the quality factor of the resonance of the first DTC and the resistor.
15. The equalizing system of claim 14 , wherein a lower resistance of the resistor reduces an amount of equalizer correction in a given frequency range and a higher resistance increases an amount of the equalizer correction in a given frequency range.
16. The equalizing system of claim 10 , further comprising:
a second coupler comprising a second input port coupled to the input port, a second output port, a second coupling port, and a second isolation port;
a second combination circuit, comprising:
a second coupling node electrically coupled to the second coupling port;
a third DTC connected between the second coupling node and ground;
a second resistor connected between the second coupling node and the ground for controlling a quality factor of a second resonance;
a second isolation node coupled to the second isolation port; and
a fourth DTC connected between the second isolation node and the ground.
17. An equalizing system, comprising:
a wireless communication system for receiving at least one service from at least one source, the wireless communication system comprising:
a head end unit;
a plurality of optical fiber cables; and
a plurality of remote units connected to the head end unit by the optical fiber cables, the head end unit being configured for routing the at least one service to the plurality of remote units; and
a RF equalizer disposed in at least one of the head end unit and one of the plurality of remote units, the RF equalizer comprising:
a coupler comprising an input port, an output port, a coupling port, and an isolation port; and
a combination circuit, comprising:
a coupling node electrically coupled to the coupling port;
a first DTC connected to the coupling node and ground;
a resistor connected between the coupling node and ground that controls a quality factor of resonance;
an isolation node coupled to the isolation port; and
a second DTC coupled to the isolation node and ground.
18. The equalizing system of claim 17 , wherein:
limiting flow of current across the first DTC affects the quality factor of the resonance of the first DTC and the resistor; and
a lower resistance of the resistor reduces an amount of equalizer correction in a given frequency range and a higher resistance increases an amount of the equalizer correction in a given frequency range.
19. The equalizing system of claim 17 , further comprising:
a second coupler comprising a second input port coupled to the input port, a second output port, a second coupling port, and a second isolation port;
a second combination circuit, comprising:
a second coupling node electrically coupled to the second coupling port; and
a third DTC connected between the second coupling node and ground.