Title :
Amplitude modulator utilizing a high-Q Class-E DC-DC converter
Author :
Cantrell, W.H. ; Davis, W.A.
Author_Institution :
Motorola Res. & Dev. Center, Fort Worth, TX, USA
Abstract :
A high-level amplitude modulator is designed and tested utilizing a high-Q Class-E DC-DC converter operating at a nominal switching frequency of 30 MHz. The output power is a maximum of 16.1 W and the efficiency is as high as 77.9%. The switching frequency is varied to control the output amplitude of the modulator. It is shown theoretically that the maximum useful dynamic range is 12.0 dB. An equation is derived that predicts the amount of frequency variation necessary to vary the output amplitude by a specific amount, based on the loaded Q of the circuit design. A RHP zero in the control-to-output transfer function is shown to have a detrimental effect on the modulation frequency to switching frequency ratio. The modulator is used to generate a DC-offset triangle-wave at frequencies as high as 500 kHz.
Keywords :
DC-DC power convertors; Q-factor; VHF amplifiers; amplitude modulation; circuit tuning; modulators; power amplifiers; transfer functions; waveform generators; 16.1 W; 30 MHz; 500 kHz; 77.9 percent; DC-offset triangle-wave generation; MRF183S n-channel enhancement-mode RF power LDMOS FET; RHP zero; control-to-output transfer function; frequency variation; high-Q Class-E DC-DC converter; high-level amplitude modulator; linear power amplifiers; loaded Q; maximum useful dynamic range; modulation frequency to switching frequency ratio; nominal switching frequency; output amplitude control; output power; variable frequency tuning; Amplitude modulation; Circuit synthesis; DC-DC power converters; Dynamic range; Equations; Power generation; Switching converters; Switching frequency; Testing; Transfer functions;
Conference_Titel :
Microwave Symposium Digest, 2003 IEEE MTT-S International
Conference_Location :
Philadelphia, PA, USA
Print_ISBN :
0-7803-7695-1
DOI :
10.1109/MWSYM.2003.1210471
