High linearity integrated silicon bipolar modulator for wideband FM CATV transmission

TitleHigh linearity integrated silicon bipolar modulator for wideband FM CATV transmission
Publication TypeConference Paper
Year of Publication1999
AuthorsRosales, R., and M. K. Jackson
Conference NameNanostructures and Quantum Dots/WDM Components/VCSELs and Microcavaties/RF Photonics for CATV and HFC Systems, 1999 Digest of the LEOS Summer Topical Meetings
PaginationIV11 -IV12
Keywordsbipolar analogue integrated circuits, cable television, circuit tuning, current mirror, differential amplifiers, driver circuits, dynamic response, emitter-coupled multivibrator core, fully-differential circuits, high linearity, high-frequency layout, impedance-matched linearized amplifier, integrated silicon bipolar modulator, intensity modulation, limiter circuits, linear transadmittance amplifier, modulators, multivibrators, optical communication equipment, optical fibre subscriber loops, output driver circuits, phase noise, Si, single-ended multitransistor circuit, static tuning, time-domain waveform, wide linear tuning range, wideband FM CATV transmission

Lightwave CATV transmission based on intensity modulation by a multichannel CATV signal is simple, but requires very linear components and high received powers. Alternatively, the multichannel signal can be FM-modulated onto one RF carrier, and transmitted with conventional intensity modulation. However, optoelectronic modulators reported to date are complex and bulky, and an electronic approach is needed. We describe a wideband FM modulator with record linearity over a wide tuning range, and phase noise equal to the best optoelectronic modulator results. An emitter-coupled multivibrator (ECM) core coupled to a linear transadmittance amplifier drives fully-differential limiter and output driver circuits. With an ECM very wide linear tuning range can be achieved if appropriately-designed collector loads are used. The circuit was fabricated in Nortel's NT-25 silicon bipolar process; the high-frequency layout is fully differential and physically symmetric. The ECM core operates at currents around 1 mA, optimized in conjunction with transistor sizing, and a -4.5 V power supply is used. The linearized transadmittance amplifier is a single-ended multitransistor circuit with passive feedback and single-pole stabilization. We report results for two versions: in mod1a the ECM current is set by a current mirror, while mod2a includes the 50 Omega;-matched linearized amplifier, which consumes 150 mW total


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