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

Paper presentation – Ultra-Portable Devices

Paper: Presented by:

Dong Han, Yuanjin Zheng. An Ultra Low Power GFSK Demodulator for Wireless Body Area Network, Inst.

• f Microelectron., A*STAR (Agency for Sci., Technol. &

Res.), Singapore, Solid-State Circuits Conference,

• 2008. ESSCIRC 2008. 34th European,15-19 Sept.

2008,on page(s): 434 - 437

• S. M. Yasser Sherazi

2009-08-27 1 Paper Presentation - Ultra Portable Devices

Outline

• Introduction.
• Design of GFSK Demodulator.
• Phase Domain ADC.
• Frequency to Voltage Converter.
• Dynamic Threshold Slicer.
• Measurement Results.
• Summary.

2009-08-27 2 Paper Presentation - Ultra Portable Devices

” Introduction 1/2”

• A novel ultra low power GFSK demodulator.
• Efficient input DC offset cancellation.
• Frequency offset cancellation for (WBAN) application.
• The demodulator uses a new multi-threshold PDADC.
• Improves the phase accuracy of the zero crossing detection.
• Smaller modulation index and robust demodulation performance.

2009-08-27 3 Paper Presentation - Ultra Portable Devices

” Introduction 2/2”

• Modulation index for the demodulator is 0.2.
• Symbol rate is up to 1.17Mbps and the carrier frequency is from 1MHz to

4MHz.

• SNR for 0.1% BER with 250kbps symbol rate and 0.28 modulation index

is 16.7dB.

• Implemented in a 0.18μm digital CMOS process with only 0.11mm2 chip

area.

• Drains 350μA current from a 1.8V power supply.

’’Design of GFSK’’

• GFSK demodulator is a new kind of zero crossing based

demodulator.

• Four main building blocks:

– The input PDADC, – One shot, – Low pass filter (LPF) and – Dynamic threshold slicer.

’Design of GFSK’’

• PDAC

– Performs input DC offset cancellation – High accuracy zero crossing setection – Convets input differential analog FSK signal to high freq FSK pulse.

• One Shot

– Regulates the width of the FSK pulse to a fixed value

’’Design of GFSK’’

• 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.

’’Design of GFSK”

• The low-IF receiver front end and the GFSK demodulator.

”The PDADC” ’’The Freq. to Voltage Converter’’

• 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’’

• One Shot circuit is a rising edge triggered pulse generator.
• Pluse with can be turned from 5ns to 400ns.
• For 2MHz input carrier frequency, TON is set to 50ns.
• The LPF is a 2-stage 4th-order filter, bandwith of 800kHz.
• The first stage is a 2nd-order passive RC LPF.
• The second LPF is a single ended 2nd-order Gm-C

Butterworth low pass biquad

’’The Freq. to Voltage Converter’’

’’The Dynamic Threshold Slicer’’

• DTS is a single threshold SPADC without the output

combiner.

• Transistors MR1,MR2, MS1, and MS2 are replaced by the high

threshold transistors to extend the holding time to 50μs.

• DTS has a wide input range from 0.2V to 1.6V.
• It can handle large DC offset of the LPF output.

’’Measurement Results’’

• Measured carrier signal and demodulated data from DTS.

’’Measurement Results’’

• Measured baseband data, Carrier, demodulated and

resampled data, and the extracted symbol rate (clk).

’’Measurement Results’’

• Measured BER of the demodulator with 0.28 modulation

index.

”Summary”

• Due to multi thresolding in PDADC zero crossing is improved.
• PDACD relaxes the LPF requirments for DC offset immunity.
• Helps in achieving small area and low power.

2009-08-27 17 Paper Presentation - Ultra Portable Devices

”Papers to Look into”

• 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. 38, Aug. 2003, pp. 1397-1400.

• 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.