| In the thesis, a high efficiency linear AM amplifier is developed, which is based on the basic theory of EER linearization amplifier technique[1]. The high efficiency digital audio amplifier technology [2]is adopted to develop the power supply modulator and the Class-D switching amplifier technology[3] is adopted to develop the high efficiency RF amplifier.Because of the using of interpolation, noise shaping and switching amplification in the digital audio amplifier technology, the power supply modulator is not only much efficient but also behaving good in envelope amplification, this advantage is hard to implemented with conventional technology.The Class-D voltage switching amplifier technology is adopted to develop the RF amplifier. In order to obtain ideal efficiency, the RF MOSFET SD2918 [4] is used. Also, the Dead-Time is inserted between the drive signals of MOSFETS, which is effective for reducing the shot-through loss and drain-source capacitor Cds loss. According to the EER theory, using the amplified envelope signal as the power supply of the Class-D amplifier, the envelope will modulate the magnitude of the RF signal. The modulated impulse RF signal is added to the impedance match circuit, so the amplified AM signal is achieved. In the thesis, the high efficiency AM amplifier is developed, and the following specifications are achieved. AM range: 0~98%; Output Power: 15W; Efficiency: higher than 63%; Envelope Distortion: lower than 4%; Harmonious: lower than -38dBc; Spurs: lower than -50dBc. It is the first time to applying the digital audio amplifier technology to the amplification in RF field. A high efficiency linear AM amplifier is developed successfully. It is a useful exploration. The Amplifier is high efficiency, low cost and small, it has certain value for using and spreading... |
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