Method and apparatus for predictably switching diversity antennas on signal dropout

A method of selectively coupling at least one of at least first and second antennas to a radio receiver comprising the steps of:

• a) obtaining a first sample of a relative radio frequency signal strength received by said radio receiver from the first antenna;
• b) calculating a running average signal strength received by said radio receiver from said first antenna;
• c) calculating a radio frequency signal strength threshold signal level, below which signals from said first antenna are to be gradually attenuated prior to being coupled into said radio receiver while signals from said second antenna are to be gradually de-attenuated prior to be coupled into said receiver, wherein the radio frequency signal strength threshold signal level is dynamically adjusted using a current value of said relative radio frequency signal strength;
• d) when the relative radio frequency signal strength received from said first antenna drops below said radio frequency signal strength threshold signal level, increasing a signal level input to said radio receiver from said second antenna and decreasing a signal level input to said radio receiver from said first antenna.

A diversity receiving apparatus for coupling signals from at least one antenna of at least first and second antennas to a radio receiver, said diversity receiving apparatus comprised of:

• a. a first variable, RF signal level attenuator having an input coupled to receive RF signals from said first antenna and having an output coupled to a RF signal summing node;
• b. a second variable, RF signal level attenuator having an input coupled to receive RF signals from said second antenna and having an output coupled to said RF signal summing node;
• c. a radio receiver having an RF input coupled to said summing node;
• d. at least one variable RF signal level attenuator controller, coupled to at least said first variable attenuator so as to control attenuation levels of said RF signal level attenuators;
• whereby RF signals received at said first and second antennas and coupled to said RF summing node can be selectively coupled to said radio receiver by controlling at least said first variable RF signal level attenuator, and
• wherein said at least one variable RF signal level attenuator controller includes a microprocessor that monitors historical signal levels from a first antenna, and, when an average of said historical signal levels from said first antenna drops below a predetermined threshold signal level, said microprocessor supplies a control voltage to a first and a second reactive networks in order to substantially continuously increase attenuation of the currently received signal delivered to said summing node from said first antenna and to substantially continuously decrease attenuation of the currently received signal delivered to said summing node from said second antenna.

A diversity receiving method for coupling signals from at least one antenna of at least first and second antennas to a radio receiver, said diversity receiving method comprised of the steps of:

• a. using a first variable, RF signal level attenuator having an input coupled to receive RF signals from said first antenna to couple said RF signals to a radio receiver input;
• b. using a second variable, RF signal level attenuator having an input coupled to receive RF signals from said second antenna to couple said RF signal signals to a radio receiver input;
• and
• c. using at least one variable RF signal level attenuator controller to control attenuation levels of at least one RF signal level attenuator;
• whereby RF signals received by at said first and second antennas can be selectively coupled to said radio receiver input by controlling at least said first variable RF signal level attenuator, and
• wherein said at least one variable RF signal level attenuator controller includes a microprocessor that monitors historical signal levels from said first antenna drops below a predetermined threshold signal level, said microprocessor supplies a control voltage to a first and a second reactive networks in order to substantially continuously increase attenuation of the currently received signal delivered to said summing node from a first antenna and to substantially continuously decrease attenuation of the currently received signal delivered to said summing node from said second antenna.