An open-loop octave-phase local-oscillator generator with high-precision correlated phases for VHF/UHF mobile-TV tuners

An octave-phase local-oscillator (LO) generator for 170-to-860-MHz mobile-TV tuners is described. It is intended to incorporate with a polyphase mixer scheme for rejecting the 3
^rd
and 5
^th
harmonics of the LO that is critical for wideband reception. The circuit is structured by a cascade of 7 inverter-based phase correctors to generate a set of LO signals with octave phases in an open-loop formation, resulting in 4times relaxation of the synthesizer's operating frequency when comparing with the conventional closed-loop form that requires the use of a div-by-4 frequency divider. Optimized in a 90-nm CMOS process, the achieved phase precisions are plusmn0.8deg in VHF III (170 to 245 MHz) band and UHF (470 to 860 MHz) band while drawing 2.3 to 5.1 mA from a 1-V supply.