A 2.4-GHz Wideband Open-Loop Phase Modulator with Phase Quantization Noise Cancellation

Pin-En Su
Advisor: Sudhakar Pamarti

Tuesday, November 16, 2010 at 3:00pm
Engr. IV Maxwell Room 57-124

Abstract:
Wide bandwidth phase modulator is one of the fundamental building blocks for low power wireless transmitter architectures, such as polar transmitter or out-phasing transmitter. Lower power consumption is achieved because instead of linear power amplifiers (PA), they adopt nonlinear PAs where no back-off operation is required. However, currently the adaptation of these architectures is limited to narrowband communication systems due to the difficulty of generating a wide enough phase modulation signal. For example, in existing polar transmitter applications, state of the art phase modulators have a bandwidth no greater than 2-MHz, which is just enough for narrowband systems such as EDGE. Another prior art uses an open-loop modulation technique to achieve a 6-MHz phase modulation bandwidth, but at the penalty of very high (about -25-dBr) phase quantization noise.

In this research, we propose an open-loop wide bandwidth phase modulator with a phase quantization noise cancellation technique. The open-loop modulation is achieved outside the PLL, so the modulation bandwidth is not limited by the PLL loop bandwidth and can be very wide. A 2.4-GHz phase modulator prototype is implemented in TSMC 0.18- m CMOS technology. The proposed phase quantization noise cancellation technique effectively reduce the peak out-of-band noise by 7-dB so that the measured peak out-of-band phase noise is -49-dBr when transmitting a 20-Mb/s GFSK signal with 3.2% r.m.s. error. The current consumption for the transmitter excluding the output buffer is 34.5-mA under 1.8V supply voltage. Since a big portion of the transmitter is digital, lower current consumption can be expected when migrating to a more advanced technology.

Biography:
Pin-En Su was born in Taipei, Taiwan. He received the B.S. degree in electrical engineering and the M.S. degree in communication engineering from National Taiwan University in 1999 and 2001, respectively. He joined SoC Technology Center (STC), Industrial Technology Research Institute (ITRI), Hsinchu, Taiwan in 2001 and worked on GPRS/WCDMA transmitter RFIC design. Since 2006, he joined the electrical engineering Ph.D. program at UCLA. His research interests are in the area of wireless transmitters and frequency synthesizers.