A CMOS Low Power Current-Mode Polyphase Filter By Hussain Alzaher & Noman Tasadduq King Fahd University of Petroleum & Minerals KFUPM, Department of Electrical Engineering

2 OUTLINE INTRODUCTION  Bluetooth receiver  Available solutions PROPOSED APPROACH CURRENT AMPLIFIER  Introduction  Fully differential current amplifier (FDCA) BASIC PRINCIPLE PROPOSED FILTER  Single ended realization  Fully differential realization EXPERIMENTAL RESULTS COMPARISON WITH THE LITERATURE CONCLUSION

3 Low-IF Receiver Architecture  Unlike zero-IF: Low-IF = No DC offset and flicker noise problems  Image problem  Solution: Polyphase bandpass filter INTRODUCTION

4 Available Solutions  Active-RC filters. High dynamic range. Limited bandwidth. Relatively high power consumption.  gm-C filters High frequency. Programmable. Poor linearity=Limited dynamic range.

5 PROPOSED APPROACH Design new polyphase filter based on optimum active element  Higher bandwidth than op-amp  lower power  Better linearity than gm  better DR

6 PROPOSED APPROACH  Current-mode processing inherently possess High BW + Low voltage  Low Power High signal swing  High linearity  Current Amplifier based Filter Simple filter topology  Low power

7 CURRENT AMPLIFIER (CA) Introduction  Conveys input current from a low impedance input terminal (X) to a high impedance output terminal (Z).  Gain=K, (sizing of current mirror transistors).  Two types: positive CA (input and output currents are both going in the same direction) and negative CA (having currents in opposite directions). CA with +ve output CA with -ve output

8 Single Input/Dual Output CA Core Input Stage Class-AB Output Stage Current Mirrors CURRENT AMPLIFIER (CA)

9 H. Alzaher, N. Tasadduq, “Realizations of CMOS fully differential current followers/amplifiers," IEEE International Symposium on Circuits and Systems (ISCAS 2009), pp Details available in: Four terminal device, with two input and two output currents. (Ideally common mode gain is zero) CURRENT AMPLIFIER (CA) Fully Differential Current Amplifier (FDCA)

10 BASIC PRINCIPLE General Transfer function Image Rejection

11 BASIC PRINCIPLE Systematic Design  Lowpass filter can be converted to a bandpass polyphase filter centered at ω c.  Complex poles are achieved by using cross-coupling between I and Q paths.

12 PROPOSED FILTER Single Ended Realization  Independent control of ω c without changing Q using R and/or C. Simple LP filter to complex filter

13 PROPOSED FILTER Nominal Values  6 th order polyphase filter is implemented.  The nominal center frequency of 3MHz and overall bandwidth of 1MHz are achieved by selecting R 1 =13k , C 1 =8.5pF and K 2 =2.1.  K 1 is 1 to achieve a gain of unity.

14 PROPOSED FILTER Fully Differential Realization FDCA

15 PROPOSED FILTER FDCA with four outputs

16 FOUR OUTPUT CA REALIZATION Core biasing circuit of I B =9  A and I SB =3  A is shared for all FDCA Total biasing current is

17 EXPERIMENTAL RESULTS  Standard 0.18  m CMOS process.  Supply Voltage ±1.35V.  Total Supply Current 0.88mA.  Center frequency 3MHz.  Bandwidth 1MHz.  Center frequency tuning using capacitor arrays.

18 EXPERIMENTAL RESULTS Signal magnitude response showing center frequency tuning

19 EXPERIMENTAL RESULTS

20 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

21 COMPARISON WITH LITERATURE

22 COMPARISON RESULTS Power consumption/pole  Proposed filter and [3] Image rejection  Propsed filter and [2] SFDR  Proposed filter

23 CONCLUSION CA based filters inherently exhibit higher bandwidth than active-RC and better linearity than gm-C. This is demonstrated by a new polyphase filter with improved SFDR and IRR while using relatively lower power.

24 Thank You,