| 摘要 |
A radio frequency transmitter-receiver alternately transmits signal pulses of frequency F1 and receives return echo signals of frequency F1. The transmitter signal of frequency F1 is generated by mixing signals of frequencies F2 and F3. A signal of frequency F3 is generated by mixing signals of frequencies F4 and F5. The return signal of frequency F1 is mixed with frequency F2 which is continuously generated by the transmitter to produce a signal of intermediate frequency F3. Frequency F5 and therefore frequencies F3 and F1 are only generated during signal transmission and therefore do not interfere with the return signal of frequency F1 and the produced intermediate frequency F3.
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