| 摘要 |
A radio frequency modulator is provided to remove a high frequency harmonics component generated in a low frequency band by operating a low pass filter in a VHF output. The radio frequency modulator(10) modulates a video/audio signal of a baseband of a received cable broadcasting or a satellite broadcasting into a carrier wave of a high frequency band. An output circuit(20) is maintained a signal level when a first channel outputs in one or higher frequency bands modulated from a radio frequency modulator. The output circuit removes a high frequency harmonics component when a second channel outputs. An output circuit comprises a trap filter(21), a low pass filter(22), and a switching unit(23). The trap filter blocks a specific frequency band signal in one or more high-frequency band signals outputted from the output terminal(RF-OUT) of the radio modulator through the coupling condenser(C1,C3). The low pass filter removes the high frequency harmonics component of the specific frequency band in one or more high-frequency band signals. The switching unit controls an operation of the low pass filter according to one of the band selected among high-frequency band signals.
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