ハイブリッド変調方式中波ラジオ送信機の性能評価 : 無線・光伝送

抄録

Described is the performance of the Medium-wave radio transmitter using Hybrid Modulation which produces AM wave directly from the digitalized audio signal. In the prototype transmitter, the efficiency of the analogue type pwer amplifier was too low to construct much higher output transmitters because the analogue signal from D/A converter was amplified by the linear amplification. Employing of a carrier PWM modulator realized a module efficiency of 80% which is 40 points higher than the conventional one. Since this transmitter has no modulator module seen in conventional transmitter. Over-all efficiency of 84%~93% (=RF output/DC input) No transient over voltages,also, has occurred with the output of the transmitter shorted, which can was obtained at the MF band. protect power devices from breakdowns. In addition, use of the serial type combiner could suppress impulse surges from the output greatly. When a impulse surge of 10kV(peak) was impressed at the output transmitter, just few volts(peak) appeared at the output of the RF power modules which means that it has 30~40 times ruggedness compared to conventional ones for lightning surges.