This paper prcscnts a dual-loop Automatic Gain Control (AGC) errrploj-ed i n l0hlbps infrared corrmunication syst e m T h e AGC is composed of an exponenbial-type variablegain amplifier. a shaping filter. il gain/hufSer stage, a n u m coherent etivelupc dctcctor, n~~d a pair uf intcgrators that providc d d loop band\vidths. Thc swit,ch and two iiitegr;rtors are realiaed by a proposed switclied integrator tcchirique. The fast, acquisiI.ion is accoiiiplished by a 5OU K H s loop bandmidt,h at, the init,ial acquisition stat.e aid followed by a 50 KHz loop bandwidth at t,he steady state. The AGC is implertierited ill 0.6Lirn SPThI Ch'IOS technology. According to the past-layout simnlat,ion, it aclii timt: of 5,rs and provides a constant out,put or lV,, at a 5Un load for 20dH iiiput signal amplitude ratige. The dual-loop AGC cu~~siiiiies 88 m W puwur fiuiri il single 3.3-V supply and occiipies 1.8 x 1.8 mnL2 uta.

This paper prcscnts an all digital US-CDMA upstream trailsmittcr. and a head-eml bascband recciwr for upstream cnlde/HFC networks. The upstrcam transmitter supports freit,y of t,hc carrier, QPSK and QAM constellat,ions A\I: variable symhol lat,cs from ltiUkchip/s to S.l2h~lchip/s incrcasing by power of i,rol and direct-digital iq-convcrsiion to achieve a~~u r a t~) arnplitnde and pilase of moduIatiw1. The trnnsnritter connist,s of pulse shaping tilt,er; half-band filter, ciiscadcd intcgrator-comb (CIC) filter-. and iiiverse SINC fillcr. The all digital ~~~~~~~~end hascband reccivcr snpport,s prug~ammable rltiadrnt,urc amplit tide modulntim up t,o (;4QAhl. Fast, t,iming and carrier recovery algorithms a r adoptcd for hnrst, inodc transmission Cudc acquisit,ion can bc iic1iievt.d wit,lrin 2 syiiibols: and tlrc carrier acqtiisitim CAN lie achicicd wit,hin 31 symbols. All digil al 1.iiiiiiig recovery is designed with ~21101,prn syrnhol t i n -ilOOppiri of carrier frcqrieiicy offset. . .illg "trSset tuicrilllce alld tile CBrI.iCr rccuvery cal, collrljcrrs:,tc