| 摘要 |
Problems arise with co-sited radio communication apparatus on ships, for example, due to the presence of wide band noise generated by a transmitter interfering with a co-located receiver. Radio communication apparatus is provided comprising a transmitter including a wide band noise limiter positioned between an exciter/modulator (1) and a power amplifier (6), the wide band noise limiter comprising a first mixer (2) fed from the exciter/modulator, a band-pass filter (4) fed from the mixer (2) with a signal corresponding to the resonant frequency of the filter (4) and a second mixer (5) fed from the filter and arranged to feed the power amplifier (6) of the transmitter, the mixers being fed from a common local oscillator (3) the output frequency of which is selected in dependence upon the transmitted frequency so that the frequency fed to the band-pass filter (4) remains constant in the presence of output frequency variation, whereby the band-pass filter (4) is effective to suppress wide band noise which would otherwise be significant in a frequency band extending to each side of the transmitted frequency. The amplifier output is fed to an antenna 7 via a further filter 8. <IMAGE>
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