| 摘要 |
An antenna assembly (12), a receiver (14), and a system (10) configured to superimpose a first received signal (32) from a first antenna (26) and an intermediate signal (52) based on a second received signal (34) from a second antenna (28) onto a single cable (40). The antenna assembly (12) includes a mixer (48) and an adjustable local oscillator (54) (ALO (54)) that frequency shift the second received signal (34) to generate the intermediate signal (52). The output frequency of the ALO (54) is controlled by a control signal (56) superimposed on the single cable (40) that is output by the receiver (14). With this arrangement, a plurality of antennas or antenna elements (26. 28. 30) can be connected to a receiver (14) using a single coaxial cable. Such an arrangement is particularly desirable to manufacturers of automobiles and other vehicles. Also, the receiver (14) can detect if the output frequency of the ALO (54) needs to be adjusted, and so close-loop control of the output frequency is possible. |
