A radio frequency beacon device for use with a backscatter interrogator
includes a processor; a receiver coupled to the processor; a backscatter
modulator coupled to the processor; and an active transmitter coupled to
the processor, the active transmitter being configured to transmit an RF
signal, in response to a trigger signal, regardless of whether the
interrogator is providing a carrier wave for backscatter modulation by
the backscatter modulator. Other methods and apparatus are provided.