A Digitally Programmable Polyphase Filter for Bluetooth By Hussain Alzaher & Noman Tasadduq King Fahd University of Petroleum & Minerals KFUPM, Department of Electrical Engineering

2 OUTLINE INTRODUCTION  Motivation  Research goals BLUETOOTH RECEIVER PROPOSED APPROACH CMOS IMPLEMENTATION  Current Follower (CF)  Introducing the tuning element (DCCF)  Voltage Follower (VF) PROPOSED FILTERS  Filter 1  Filter 2 EXPERIMENTAL RESULTS CONCLUSION

3 INTRODUCTION Motivation  Use of active polyphase filters is renewed as they provide the solution for image rejection in low-IF wireless applications.  Active-RC filters. High dynamic range. Capacitor and/or resistor arrays (matrices) for tuning require relatively large silicon area. Switching transistors, associated with finite non-linear resistances, degrade the linearity.  gm-C filters Digitally programmable. Poor linearity. Limited dynamic range.

4 INTRODUCTION Research Goals  Design Voltage-Mode Polyphase Filter. Simple active elements; Current follower (CF) and Voltage follower (VF).  Introduce the Programmability Feature. Use highly linear current division network (CDN)  Investigate the Characteristics of the Proposed Filter.  Implement and Experimentally Test the Fully Differential Version for Low-IF Bluetooth receiver.  Compare Proposed Design with Existing Solutions.

5 Low-IF Receiver Architecture 1MHz < IF < 10MHz Image problem LOW-IF BLUETOOTH RECEIVER

6 PROPOSED APPROACH Systematic Approach  Lowpass filter can be converted to a bandpass polyphase filter centered at ω c.  General Transfer Function of a polyphase filter:

7 CMOS IMPLEMENTATION Current Follower (CF) I x = I z V x = 0

8 CMOS IMPLEMENTATION Introducing the Tuning Element  Current Division Network (CDN) Inherently linear. Input current is binary weighted. Output current can be expressed as:

9 CMOS IMPLEMENTATION Introducing the Tuning Element  Digitally Controlled CF (DCCF) with

10 CMOS IMPLEMENTATION Voltage Follower

11 PROPOSED FILTERS Filter 1  Independent control of ω c only using capacitor arrays.

12 PROPOSED FILTERS Filter 2  Independent control of ω c by adjusting the gain (  ). Q by adjusting R. Filter gain by adjusting Ri.  Internal nodes either at virtual ground or low impedance.

13 EXPERIMENTAL RESULTS Fully balanced 6th-order polyphase filter for a low-IF Bluetooth receiver is designed for Filter 2.  TSMC CMOS 0.35  m (MOSIS)  Supply Voltage ±1.35V.  Total Supply Current 1mA.  6-bit CDN used for tuning.  Center frequency 3MHz.  Bandwidth 1MHz.  Total Area 0.65mm 2.

14 EXPERIMENTAL RESULTS Magnitude response showing center frequency tuning

15 EXPERIMENTAL RESULTS

16 COMPARISON WITH LITERATURE 1.B. Shi, W. Shan, and P. Andreani, 2002, “A 57dB image band rejection CMOS gm-C polyphase filter with automatic frequency tuning for Bluetooth,” Proc. Int. Symp. Circuits and Systems, ISCAS’ 2002., vol. 5, pp. V II-172, A. Emira, and E. Sánchez-Sinencio, “A pseudo differential complex filter for bluetooth with frequency tuning,” IEEE Trans. Circuits and Syst.-II, vol. 50, pp. 742 – 754, October B. Guthrie, J. Hughes, T. Sayers, and A. Spencer, “A CMOS gyrator Low- IF filter for a dual-mode Bluetooth/ZigBee transceiver,” IEEE J. Solid-State Circuits, vol. 55, no. 9, pp , Sep C. Psychalinos, “Low-voltage log-domain complex filters,” IEEE Trans. Circuits and Syst.-II, vol. 55, no. 11, pp , Dec

17 COMPARISON WITH LITERATURE

18 COMPARISON WITH LITERATURE REMOVE IT IF YOU WANT TO KEEP THE PREVIOUS SLIDE

19 CONCLUSION xxxxxx