An integrated tunable electrical-balance filter with >60dB stopband attenuation and 1.75–3.7GHz stopband tuning range

This paper proposes the concept of electrical balance filters to enable integrated, tunable RF filters, where a pass- and stopband are designed by the change in electrical-balance across frequency. These filters can be constructed using low Q integrated LC resonators. The stopband frequency is the frequency where two on chip balance networks are tuned to be equal in impedance or `balanced', while the passband frequency is the frequency where the balance condition is disturbed as much as possible for low insertion loss. A 1.5mm2 electrical balance low-pass filter prototype is implemented in 0.18μm SOI CMOS. It has <;4dB insertion loss at 1GHz with a >60dB, >33MHz stopband tunable from 1.75 to 3.7 GHz.