Outline Introduction. Paper: Design of GFSK Demodulator. Dong - PowerPoint PPT Presentation

Paper presentation – Ultra-Portable Devices Outline • Introduction. Paper: • Design of GFSK Demodulator. Dong Han, Yuanjin Zheng. An Ultra Low Power GFSK Demodulator for Wireless Body Area Network, Inst. • Phase Domain ADC. of Microelectron., A*STAR (Agency for Sci., Technol. & Res.), Singapore, Solid-State Circuits Conference, • Frequency to Voltage Converter. 2008. ESSCIRC 2008. 34th European,15-19 Sept. 2008,on page(s): 434 - 437 • Dynamic Threshold Slicer. Presented by: • Measurement Results. S. M. Yasser Sherazi • Summary. 2009-08-27 Paper Presentation - Ultra Portable Devices 1 2009-08-27 Paper Presentation - Ultra Portable Devices 2 ” Introduction 1/2” ” Introduction 2/2” • Modulation index for the demodulator is 0.2. • A novel ultra low power GFSK demodulator. • Symbol rate is up to 1.17Mbps and the carrier frequency is from 1MHz to • Efficient input DC offset cancellation. 4MHz. • Frequency offset cancellation for (WBAN) application. • SNR for 0.1% BER with 250kbps symbol rate and 0.28 modulation index is 16.7dB. • The demodulator uses a new multi-threshold PDADC. Implemented in a 0.18 μ m digital CMOS process with only 0.11mm 2 chip • area. • Improves the phase accuracy of the zero crossing detection. • Drains 350 μ A current from a 1.8V power supply. • Smaller modulation index and robust demodulation performance. 2009-08-27 Paper Presentation - Ultra Portable Devices 3

’’Design of GFSK’’ ’Design of GFSK’’ • GFSK demodulator is a new kind of zero crossing based • PDAC demodulator. – Performs input DC offset cancellation – High accuracy zero crossing setection – Convets input differential analog FSK signal to high freq FSK pulse. • Four main building blocks: – The input PDADC, • One Shot – One shot, – Regulates the width of the FSK pulse to a fixed value – Low pass filter (LPF) and – Dynamic threshold slicer. ’’Design of GFSK’’ ’’Design of GFSK” • The low-IF receiver front end and the GFSK demodulator. • LPF – It averages the fixed width FSK pulse over the equal symbol period to produce the output voltage – Presenting the freq information of the carrier signal. • Threshold Slicer – Makes binary decision on the LPF output to produce the demodulated data.

’’The Freq. to Voltage Converter’’ ”The PDADC” • FVC consists of PDADC, one shot, and LPF. • PDADC has 60 degree phase accuracy and 3 thresholds. • High immunity to the input DC offset in PDADC. • Input freq 2MHz, output pulse train is 12MHz. • Input voltage range of 0.3V to 1.5V. • Cancels DC offset up to 550mV with 600MV peak to peak signal swing. ’’The Freq. to Voltage Converter’’ ’’The Freq. to Voltage Converter’’ • One Shot circuit is a rising edge triggered pulse generator. • Pluse with can be turned from 5ns to 400ns. • For 2MHz input carrier frequency, T ON is set to 50ns. • The LPF is a 2-stage 4th-order filter, bandwith of 800kHz. • The first stage is a 2 nd -order passive RC LPF. • The second LPF is a single ended 2 nd -order Gm-C Butterworth low pass biquad

’’The Dynamic Threshold Slicer’’ ’’Measurement Results’’ • DTS is a single threshold SPADC without the output • Measured carrier signal and demodulated data from DTS. combiner. • Transistors M R1 ,M R2 , M S1 , and M S2 are replaced by the high threshold transistors to extend the holding time to 50 μ s. • DTS has a wide input range from 0.2V to 1.6V. • It can handle large DC offset of the LPF output. ’’Measurement Results’’ ’’Measurement Results’’ • Measured baseband data, Carrier, demodulated and • Measured BER of the demodulator with 0.28 modulation resampled data, and the extracted symbol rate (clk). index.

”Summary” ”Papers to Look into” • Due to multi thresolding in PDADC zero crossing is improved. • Bo Xia, Chunyu Xin, Wenjun Sheng, Valero-Lopez A.Y., and Sanchez- Sinencio E., "A GFSK demodulator for low-IF Bluetooth receiver,“ IEEE Journal of Solid-State Circuits, vol. • PDACD relaxes the LPF requirments for DC offset immunity. 38, Aug. 2003, pp. 1397-1400. • Helps in achieving small area and low power. • Tai-Cheng Lee, and Chin-Chi Chen, "A mixed-signal GFSK demodulator for Bluetooth," IEEE Transactions on Circuits and Systems–II, vol. 53, No. 3, Jun 2006, pp. 197-201. 2009-08-27 Paper Presentation - Ultra Portable Devices 17