King Fahd University of Petroleum Minerals KFUPM Department

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

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

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

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

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

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

CURRENT AMPLIFIER (CA) Introduction Ø Conveys input current from a low impedance input terminal (X) to a high impedance output terminal (Z). Ø Gain=K, (sizing of current mirror transistors). Ø 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 7

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

CURRENT AMPLIFIER (CA) Fully Differential Current Amplifier (FDCA) Four terminal device, with two input and two output currents. (Ideally common mode gain is zero) Details available in: H. Alzaher, N. Tasadduq, “Realizations of CMOS fully differential current followers/amplifiers, " IEEE International Symposium on Circuits and Systems 9 (ISCAS 2009), pp. 1381 -1384.

BASIC PRINCIPLE n n General Transfer function Image Rejection 10

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

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

PROPOSED FILTER n Nominal Values Ø Ø Ø 6 th order polyphase filter is implemented. The nominal center frequency of 3 MHz and overall bandwidth of 1 MHz are achieved by selecting R 1=13 k. W, C 1=8. 5 p. F and K 2=2. 1. K 1 is 1 to achieve a gain of unity. 13

PROPOSED FILTER n Fully Differential Realization FDCA 14

PROPOSED FILTER FDCA with four outputs 15

FOUR OUTPUT CA REALIZATION Core biasing circuit of IB=9 m. A and ISB=3 m. A is shared for all FDCA Total biasing current is 16

EXPERIMENTAL RESULTS ¨ Standard 0. 18 mm CMOS process. ¨ Supply Voltage ± 1. 35 V. ¨ Total Supply Current 0. 88 m. A. ¨ Center frequency 3 MHz. ¨ Bandwidth 1 MHz. ¨ Center frequency tuning using capacitor arrays. 17

EXPERIMENTAL RESULTS n Signal magnitude response showing center frequency tuning 18

EXPERIMENTAL RESULTS 19

COMPARISON WITH LITERATURE 1. 2. 3. 4. B. Shi, W. Shan, and P. Andreani, 2002, “A 57 d. B 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-169 - II-172, 2002. 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 2003. B. Guthrie, J. Hughes, T. Sayers, and A. Spencer, “A CMOS gyrator Low. IF filter for a dual-mode Bluetooth/Zig. Bee transceiver, ” IEEE J. Solid-State Circuits, vol. 55, no. 9, pp. 1872 -1878, Sep. 2005. C. Psychalinos, “Low-voltage log-domain complex filters, ” IEEE Trans. Circuits and Syst. -II, vol. 55, no. 11, pp. 3404 - 3412, Dec. 2008. 20

COMPARISON WITH LITERATURE 21

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

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

Thank You, 24