WIRELESS MODEM HAVING COMMON TRANSMITTING AND RECEIVING UNITS

摘要

PURPOSE: A wireless modem is provided to be commonly used in data transmission having two kinds of transmission speeds. CONSTITUTION: The modem comprises a transmitting unit and a receiving unit. The transmitting unit comprises: a switch(SW1) for selecting first or second feedback resistance for deciding an amplifying ratio of a transmitting data, an amplifier for amplifying an input transmitting data. The receiving unit comprises a narrow band pass filter(46-1) for filtering an intermediate frequency signal in a narrow band of 6KHz, a wide band pass filter(46-2) for filtering the intermediate frequency in a wide band of 13KHz; a first pin diode(PD-1) whose anode terminal is connected to the output terminal of the narrow band pass filter through a first capacitor(C1) and cathode terminal is connected to a demodulator(47) through a third capacitor(C3); a second pin diode(PD-2); and a second switch(SW2) for selectively supplying a switching voltage to the anode of the first pin diode and the anode of the second pin diode.