low-power cmos integrated circuits for radio frequency applications 01522052

CODEC 04 SPECIAL SECTION Low-power CMOS integrated circuits for radio frequency applications M.J. Deen, R. Murji, A. Fakhr, N. Jafferali and W.L. Ngan Abstract: This paper presents results for a mixer, two voltage-controlled oscillators (VCOs) and a frequency doubler (FD) suitable for low-power CMOS radio frequency (RF) systems. Results are first described for a mixer which uses the body terminal of the transistor as one of the inputs to down -conv ert a 1.9 GHz RF signa l to a 250 MHz interme diate -frequ ency signa l. Next, two VCOs are describ ed. The first VCO is an ultra-low -powe r oscil lator design ed to oper ate in the 2.4 GHz ind ust ria l sci ent ific medic al ban d with a supply of 0.4V. The second VCO descr ibe d is a fully integ rated LC-tank VCO with automati c amplit ude control operatin g at 4 GHz. Frequenc y tunin g for this VCO is performed by accessing the body of cross-coupled transistors of the VCO core. Finally, a wideband, low-power implementation of a frequency doubler is presented. The frequency do ub le r cons is ts of two id en ti ca l un ba la nc ed so ur ce -c ou pl ed pa ir s wi th di ff er en t W /L ratios, whose inputs are connected in parallel and its output taken single-ended. The FD is based on the MOS transistor in saturation. All circuits were designed in a deep n-well 0.18 mm technology, allowing application of different potentials to the body of different NMOS transistors. 1 In tr od uc ti on With the minimu m featu re size in micro electr onic devices reducing to deep submicron values, CMOS technology has be co me a vi ab le ch oi ce fo r impl ementa ti on of ra di o fre que ncy (RF ) int egr ate d cir cuits (ICs) bui ldi ng blo cks [1, 2] . In addition, portable devices are required to operate for extended periods of time without the need to charge or cha nge the bat ter y, thu s the imp ort anc e of low -po wer cir cui ts. How eve r, the red uct ion of the sup ply vo lta ge deman ded by reliab ility conce rns has caused many analo gue cir cui t solutions to be uns uit abl e for low-power app lic a- tio ns. The ref ore , new cir cui t tec hni que s and inn ova tiv e de si gn ap pr oa ches are re qu ire d to me et th e st ri ng ent requirements of today’s cutting edge wireless communica- tion systems. Two key RFICs are the mixer and the voltage-controlled osc illa tor (VCO) [3–6]. In mo de rn lo w- po we r, fu ll y integrated mixers, power consumption, linearity, conversion gain and noise figure are the key performance parameters. For VCOs, pow er consum pti on, fre que ncy tun ing ran ge and ph ase noi se are the key per for man ce parameters. In addition, as RFICs are operated at even high frequencies, low-power circuits such as the frequency doubler (FD) are becoming increasingly important for a single chip solution. For the mixer, we explore the use of the MOSFET as a tr ue fo ur -t er mi na l de vi ce by us in g th e bo dy te rmin al , thereby collapsing the RF and LO stages into a single stage. The first VCO described is an ult ra- low pow er osc ill ato r de si gn ed to op er ate in th e 2. 4 GHz in du st ri al sc ie nt ifi c medical (ISM) band. This circuit uses the MOSFET in the su bt hr es ho ld re gi on of op erat io n in or de r to ge t an enhanced pha se noi se per for man ce by filt eri ng out some of the major noise sources in the VCO. The second VCO described is one with automatic amplitude control (AAC), whi ch att emp ts to res olv e some per for man ce issu es wit h practical implementations of oscillators, such as a fast and re li ab le st ar tu p; al lo win g th e os ci ll at or to be set to its optimal bias point in terms of noise, while still biasing it with the optimal current at startup; and allowing for a well defined level of output power [7]. As the frequency of wireless communications extends to increasingly hig her frequency ban ds, the gen era tio n of hig hly sta ble loc al osc illa tor sig nal s at low cost bec ome s more and more challenging. The frequency doubler (FD) is widely used in a variety of applications in order to extend the frequency limit of fixed and varia ble low-phase -nois e oscillators [8–10] and is the final cir cui t discussed in this paper. 2 Th e bo dy -i np ut mi xe r Downconversion mixers are an important building block of the RF front-end. In the design of these mixers, there are trade-offs between conversion gain, linearity (represented by the input -refer red third -orde r interc ept poin t, IIP3) , noise figure, minimum voltage supply, and power consumption. Other importan t perfo rman ce char acter istics are the port- to- por t iso lat ion and the dyn ami c ran ge, who se req uir e- men ts are more dep end ent on spe cifi c app lic ati ons . We discuss a body-input mixer topology that is able to achieve a low-v oltag e suppl y requi remen t and low-power consu mp- tion levels, while still being able to maintain an acceptable level of performance. 2.1 Traditional mixers In circuit implementations today, the most common mixer topology used is the Gilbert cell mixer that was originally The authors are with Departmen t of Compu ter and Electric al Engine ering, McMas ter University, CRL 226, 1280 Main Street West, Hamilton, Canada ON L8S 4K1 E-mail: [email protected] r IEE, 2005 IEE Proceedings online no. 20045069 doi:10.1049/ip-cds:20045069 Paper first received 14th July 2004 and in final revised form 24th November 2004 IEE Proc.-Circuits Devices Syst., Vol. 152, No. 5, October 2005 509

low-power cmos integrated circuits for radio frequency applications 01522052

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