Switched antenna diversity algorithm employing received signal strength, phase errors and recovered clock

A method for selecting between first and second antennas in a communication device, the communication device currently receiving a signal at the first antenna, the method comprising the steps of:

• receiving a signal at the communication device;
• measuring characteristics of the received signal including:
• received signal strength, phase error, and recovered clock of the received signal;
• establishing a received signal strength threshold, a phase error threshold, and a recovered clock threshold;
• comparing the received signal strength, the phase error and the recovered clock of the received signal with the received signal strength threshold, the phase error threshold, and the recovered clock threshold, respectively;
• and
• toggling from the first antenna to the second antenna when at least one of the measured characteristics of the received signal exceeds the received signal strength, phase error, and recovered clock thresholds.

A method for switching between two antennas in a communication unit, the communication unit receiving a signal at a currently selected antenna, and the signal being characterized by receive signal strength, phase error, and recovered clock, the signal also being received in a plurality of receive frames, the method comprising the steps of:

• loading a first, second and third register with a receive signal strength threshold, a phase error threshold, and a recovered clock threshold, respectively;
• comparing the signal being characterized by receive signal strength, phase error, and recovered clock to the first three registers, respectively;
• determining which of the thresholds has been exceeded;
• loading a fourth register with a recovered clock hysteresis limit;
• loading a fifth register with a receive signal strength and phase error hysteresis limit;
• counting the number of receive frames for recovered clock;
• comparing the number of receive frames for recovered clock to the fourth register;
• determining if the number of receive frames for recovered clock exceeds the recovered clock hysteresis limit;
• counting the number of receive frames for phase error and receive signal strength;
• comparing the number of receive frames for phase error and receive signal strength to the fifth register;
• determining if the number of receive frames for phase error and receive signal strength exceeds the phase error and receive signal strength hysteresis limit;
• switching from the currently selected antenna when both the recovered clock threshold has been exceeded and the recovered clock hysteresis limit has been exceeded;
• and
• switching from the currently selected antenna when both the phase error and receive signal strength threshold has been exceeded and the phase error and receive signal strength hysteresis limit has been exceeded.

A method for changing from a current antenna selection to a subsequent antenna in a communication unit that is receiving a signal at the current antenna, the method comprising the steps of:

• measuring receive signal strength, phase error, and recovered clock of the signal at the current antenna;
• determining limits for received signal strength, phase error, and recovered clock;
• determining if each of the receive signal strength, the phase error, and the recovered clock exceeds its respective limit;
• toggling to the subsequent antenna when each of the receive signal strength, the phase error, and the recovered clock exceeds its respective limit;
• and
• maintaining the current antenna selection when all of the receive signal strength, the phase error, and the recovered clock do not exceed their respective limits.

A method for changing from a current antenna selection to a subsequent antenna in a communication unit that is receiving a signal at the current antenna, the communication unit receiving the signal for a receive period comprising a plurality of receive frames, the method comprising the steps of:

• measuring receive signal strength, phase error, and recovered clock of the signal at the current antenna;
• determining limits for received signal strength, phase error, and recovered clock;
• determining if at least one of receive signal strength, phase error, and recovered clock exceeds its limit;
• setting a threshold for the number of receive frames received during the receive period;
• monitoring the number of receive frames throughout the receive period;
• comparing the number of receive frames to the threshold;
• toggling to the subsequent antenna when at least one of receive signal strength, phase error, and recovered clock exceeds its limit;
• and
• maintaining the current antenna selection when all of the receive signal strength, phase error, and recovered clock do not exceed their respective limits.

An apparatus for selecting one of at least two antennas in a communication device comprising a currently selected antenna and providing a means for determining received signal quality and for toggling from the currently selected antenna to a subsequent antenna based on the received signal quality, the apparatus comprising:

• a receiver for receiving a signal from the currently selected antenna;
• a switch for electrically coupling the currently selected antenna to the receiver;
• a phase lock loop circuit coupled to the receiver for providing a receive signal strength indicator signal, a phase error signal, and a recovered clock signal;
• and
• a controller coupled to the receiver for determining the received signal quality of the signal based on the receive signal strength indicator signal, the phase error signal, and the recovered clock signal, and providing a control signal when the receive signal strength indicator signal exceeds a receive signal strength threshold and the phase error signal exceeds a phase error signal threshold and the recovered clock signal exceeds a recovered clock threshold, the switch being operatively responsive to the control signal for toggling from the currently selected antenna to the subsequent antenna.