Patent ID: 6185201
Filing Date: 2001-02-06
Classification: H04B,H04J

Abstract:
A multiplex radio transmitter which multiplexes a plurality of channel signals having different frequencies and transmits the multiplexed signal, said multiplex radio transmitter being in a multiple form composed of a plurality of transmission sections provided one for each of a plurality of radio frequency channels, each of said transmission sections comprising:a modulation section which modulates a data signal and outputs the modulated signal as a first intermediate frequency signal;a first frequency conversion section which converts the frequency of the first intermediate frequency signal outputted from the modulation section, through use of a first local signal to thus output a second intermediate frequency signal which is higher in frequency than the first intermediate frequency signal by only the frequency of the first local signal;a first filter which eliminates a frequency component of the first local signal from the second intermediate frequency signal outputted from the first frequency conversion section;a second frequency conversion section which has an oscillator operable to output a plurality of second local signals, for converting the frequency of a signal outputted from the first filter, through use of a second local signal to thus output a radio frequency signal as an upper side signal higher in frequency than the second intermediate frequency signal by only the frequency of the second local signal, an image frequency signal as a lower side signal obtained by addition of both a first harmonic signal, which is expressed by an integral multiple of the second intermediate frequency signal outputted from said first frequency conversion section, and a second harmonic signal, which is expressed by an integral multiple of the second local signal, the lower end of a radio frequency signal band being higher than the upper end of a second local signal band, the upper end of an image frequency signal band being smaller than the lower end of said second local signal band, said radio frequency signal band, said second local signal band and said image frequency signal band being separated without overlapping one another; anda second filter having at least a band-pass characteristic such as to pass radio frequency signals of a plurality of channels to be used, said second filter being operable to filter out the radio frequency signal as the upper side signal outputted from the second frequency conversion section and to eliminate a frequency component of the second local signal as the lower side signal.