All-Pass Filter Based Linear Voltage Controlled Quadrature Oscillator

A linear voltage controlled quadrature oscillator implemented from a first-order electronically tunable all-pass filter (ETAF) is presented. The active element is commercially available current feedback amplifier (AD844) in conjunction with the relatively new Multiplication Mode Current Conveyor (MMCC) device. Electronic tunability is obtained by the control node voltage (V) of the MMCC. Effects of the device nonidealities, namely, the parasitic capacitors and the roll-off poles of the port-transfer ratios of the device, are shown to be negligible, even though the usable high-frequency ranges are constrained by these imperfections. Subsequently the filter is looped with an electronically tunable integrator (ETI) to implement the quadrature oscillator (QO). Experimental responses on the voltage tunable phase of the filter and the linear-tuning law of the quadrature oscillator up to 9.9 MHz at low THD are verified by simulation and hardware tests

A linear tuning ring VCO for spectrum monitor receiver in cognitive radio applications

A ring oscillator is designed and implemented on standard 130nm CMOS technology for wide range frequency tuning purpose in a spectrum monitor receiver used in cognitive radio applications. The three-stage differential ring oscillator is tuned by an array of MOS varactors, which is controlled by a novel staggered voltage offset system for improved tuning linearity. The proposed ring oscillator achieves a measured tuning range from 4.85GHz to 7.15GHz, consuming 4.2mA current from a 1.2V supply voltage. The measured phase noise is -82.5 dBc/Hz at 1MHz offset from an operating frequency of 4.88GHz. The die area of the oscillator core is about 70?m×50?m