• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.603-614
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• 2005

In this paper, digital ultra-narrowband Walky-Talky using direct conversion method for CQPSK modulation scheme is implemented with satisfying the requirements of APCO P25. RF transceiver design and implementation scheme that minimize the influence of DC-offset and AC-coupling at ultra-narrowband is proposed. This scheme also minimizes the influence of nonlinear characteristic at power amplifier fir CQPSK modulation method. Test results of full system including DSP module and direct conversion RF transceiver show that FCC emission mask at 36.8 dBm PEP meets the standard requirements. The characteristic of receiver AGC by PWM control signal is linear at 40 dB dynamic range and voice communication at input power level of -116 dBm is successful. Also it is verified that the performance of BER versus frequency offset and versus SNR meets the standard requirements.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.61-70
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• 2008

This paper presents the flexible MEMS transmitter based on flexible printed circuit board or FPCB, which can be transformed to arbitrary shape. The FPCB is suitable to fabricate light weight and small size modules with the help of its thin thickness. Moreover a module based on FPCB can be attached on the arbitrary curved surface due to its flexible enough to be lolled up like paper. In this paper, the flexible MEMS transmitter integrated on FPCB for a short-distance sensor network which is based on orthogonal frequency division multiplexing(OFDM) communication system is proposed. The active device of the proposed flexible MEMS transmitter is fabricated on InGaP/GaAs HBT process which has been used for power amplifier design to take advantages of high linear and high efficient characteristics. Moreover, the passive devices such as the filter and signal lines are integrated and fabricated on the FPCB board. The performance of the fabricated flexible MEMS transmitter is analyzed with EVM characteristics of the output signal.