Control system and method for diversity antenna system
A control system and method for controlling switching between and among multiple antennas in a diversity antenna system comprising a radio head unit associated with a radio receiver; two or more antennas, either located in separate antenna modules or co-located in the same antenna module; a switch circuit; and a single cable. Control signals for controlling switching are provided as changes in a DC power supply signal carried on the single cable. In the case of multiple antenna modules, the radio head unit and the antenna modules are connected by the single cable using a daisy-chain architecture.
1. A control system for selectively controlling switching in a diversity antenna system, the control system comprising:
a radio head unit alternatively coupled to first and second antennas, and configured to:
deliver a DC power supply signal to and receive a return signal from a selected one of the antennas,
determine a signal quality of the received return signal based on a determined actual bit error rate, and
generate a control signal when a pre-established threshold bit error rate value is exceeded by modifying the DC power supply signal, wherein said control signal is operable to cause the radio head unit to switch from the selected one of the antennas to the other of the antennas, when the signal quality of the received signal exceeds a pre-established threshold value;
a switch circuit intermediately and communicatively coupled between the unit and each of the antennas, wherein the circuit includes an RF switch and a switch controller having a voltage limiting device and a current amplifying device, and is configured to receive the control signal and toggle between the first and second antennas, so that the radio head delivers the DC power supply signal and receives a return signal from the other of the antennas; and
a single daisy chain cable interconnecting the radio head unit to the switch circuit, so as to carry the received signal and the control signal therebetween.
2. The control system as set forth in claim 1 , wherein the control signal is a steady change in the DC power supply signal.
3. The control system as set forth in claim 1 , wherein the control signal is a pulse change in the DC power supply signal, and the switch circuit includes an electronic latch that is switched as a result of the pulse change.
4. The control system as set forth in claim 1 , wherein the switch circuit is located in an antenna module with the first antenna and includes an RF switch and a switch controller, the RF switch is a single-pull, double-throw switch that switches in response to a switch signal provided by the switch controller, and the switch signal is a transistor-transistor logic signal.
5. The control system as set forth in claim 1 , wherein the switch circuit is located in an antenna module with the first and second antennas.
6. A diversity antenna system, having closed loop feed back control, said system comprising:
first and second antennas;
a radio head unit communicatively coupled to the first antenna, adapted to determine a signal quality of a received signal provided by the first antenna, and to generate a control signal for switching from the first antenna to the second antenna when the signal quality of the received signal exceeds a pre-established threshold value;
a switch circuit including a single RF switch, a Schmitt trigger having a Darlington level shifter, and Zener diode, and adapted to receive the control signal and to switch to the second antenna only upon receipt of the control signal; and
a single cable adapted to connect the radio head unit to the switch circuit and to carry the received signal, the control signal, and a DC power supply signal therebetween,
said unit including a control circuit having a plurality of low noise amplifiers operable to eliminate thermal tailing and impedance mismatching.
7. The diversity antenna system as set forth in claim 6 , wherein the radio head unit determines the signal quality of the received signal based on a determined actual bit error rate, such that when a pre-established threshold bit error rate value is exceeded, the control signal is generated to switch to the second antenna.
8. The diversity antenna system as set forth in claim 6 , wherein the control signal is a change in the DC power supply signal carried on the single cable.
9. The diversity antenna system as set forth in claim 8 , wherein the control signal is a steady change in the DC power supply signal.
10. The diversity antenna system as set forth in claim 8 , wherein the control signal is a pulse change in the DC power supply signal, and the switch circuit includes an electronic latch that is switched as a result of the pulse change.
11. The diversity antenna system as set forth in claim 8 , wherein the switch circuit and the first antenna module are both located in a first antenna module, and the second antenna is located in a second antenna module that is spaced apart from the first antenna modules, and the radio head unit, the first antenna module, and the second antenna module are connected by the single cable using a daisy chain architecture.
12. The diversity antenna system as set forth in claim 8 , wherein the switch circuit, the first antenna, and the second antenna are all located in a single antenna module.
13. A method of controlling switching in a diversity antenna system, the method comprising the steps of:
(a) connecting a radio head unit to a first antenna module having a first antenna and a second antenna module having a second antenna with a single cable using a daisy chain architecture;
(b) determining a signal quality of a received signal provided by a first antenna and carried on the single cable;
(c) generating a control signal for switching from the first antenna to the second antenna when the signal quality of the received signal is below a pre-established threshold value, and wherein the control signal is a change in a DC power supply signal that is also carried on the single cable;
(d) receiving the control signal at a switch circuit located in the first antenna module with the first antenna; and
(e) switching from the first antenna to the second antenna in response to the control signal.
14. The method as set forth in claim 13 , wherein determining the signal quality of the received signal is based on an actual bit error rate, such that when a pre-established threshold bit error rate value is exceeded by the actual bit error rate, the control signal is generated to switch to the second antenna.
15. The method as set forth in claim 13 , wherein the generated control signal is a steady change in the DC power supply signal.
16. The method as set forth in claim 13 , wherein the generated control signal is a pulse change in the DC power supply signal, and the switch circuit includes an electronic latch that is switched by the pulse change.