PSM変調を用いた全半導体化広帯域短波送信機の開発(デジタル放送・デジタル設備,一般)  [in Japanese] Development of a Fully Solid State Wide band Short-wave Transmitter using PSM  [in Japanese]

PSM(Pulse Step Modulation)変調方式を用いて,アナログAM変調及びディジタル変調(DRM:Digital Radio Mondiale)が可能な,国際放送用短波帯(3M〜26MHz)出力1kWの全半導体化広帯域短波送信機を開発した.本機は変調部にディジタル処理化が可能で高品質化が図れるPSM変調方式を,PAには高効率化が期待できるE級増幅方式を採用するとともに,各PA(出力125W)のE級動作に必要な負荷インピーダンスにするための位相補償機能をもつ新方式出力回路を実装している.この結果,125W PA単体において3.925MHzで約95%,25.885MHzでは約86%のドレーン効率を得た.また,広帯域(3M〜26MHz)に渡って,アナログ変調特性としてS/Nは54dB以上,ひずみ率は4%以下が得られている.ディジタル変調特性においても目標性能を満足する約24.5dBのS/Nが得られた.

We developed an evolutional wideband (3M〜26MHz) short-wave transmitter with an output of 1kW using PSM (Pulse Step Modulation) that digital (DRM: Digital Radio Mondiale) and analog AM modulation are possible. This equipment employs digital processed PSM method that high sound quality can be easily achieved in the modulation section and class E amplification for obtaining higher efficiency in the PA section composed of eight 125W PA. In addition, new output circuit for phase compensation of the load impedance. As a result, in the 125W PA, a drain efficiency of 95% at 3.925MHz and 86% at 25.885MHz was obtained. As analog AM characteristics, S/N of 54dB and above, distortion factor of 4% and under were obtained ranging from 3M to 26MHz. In digital modulation (DRM), S/N of about 24.5dB that satisfies target performance sufficiently was obtained.