| 摘要 |
An interference attenuating remote audience survey system (42) is configured to identify radio stations (84) to which tuners (26) are tuned, the tuners (26) having local oscillator (LO) signals (30) emitted therefrom. The system (42) includes a first antenna (34) for sensing a first signal (52) at a selected LO frequency (88), the first signal (52) including one of the LO signals (30) and an interference signal (96). A second antenna (44) receives a second signal (54) at the selected LO frequency (88), the second signal (54) including an interference signal (100). A shield element (48) shields the second antenna (44) from receiving the one of the LO signals (30). The first and second signals (52, 54) are subtractively combined to produce a third signal (77), the interference signal (96) being attenuated from the third signal (77). A receiver (64) is configured to detect the one of the LO signals (30) within the third signal (77) to determine that one of the tuners (26) is tuned to the one of the radio stations (84) associated with the detected LO signal (30).
|
