Voltage-tunable immittance functions: Linear voltage-controlled quadrature oscillator implementation

Abstract

ABSTRACT A new scheme on the realisation of voltage-tunable immittance function (VTIF) is proposed. Here two types of grounded, high-quality (Q) resonant filters and voltage-controlled quadrature oscillators (VCQO) with a linear tuning law are presented. Analysis indicates that the filter/QO parameters are impervious to the ABB parasitic components. Experimental results exhibit a VCQO-linear tuning range of fo ~14 MHz with a satisfactory phase-noise margin of immittances, viz., inductance (L) and frequency-dependent negative resistance (D) are derived using the Current Feedback Amplifier (CFA) combined with analog voltage-multiplier elements as the active building block (ABB). Subsequently, implementation of LC-bandpass and rD-band-reject selective filters, along with QO designs, is presented with low THD and phase noise of (─)104 dBc/Hz at 30 kHz offset. Experimental results of the proposed circuits had been satisfactorily verified using standard commercially available IC modules.