A Closed-Form Input Admittance Solution for RF and Microwave Switched Capacitor Arrays

The parallel equivalent circuit for radio-frequency and microwave single-ended switched capacitor arrays (SSCAs) is investigated. In particular, the SSCA equivalent capacitance and resistance are highlighted and predicted by new closed-form mathematic expressions. The behavior of the SSCA with the control input and frequency is also analyzed in detail. The proposed model shows that the SSCA admittance depends on frequency, integration technology parameters, circuit size and control input. An ultra-wide-band SSCA, designed with standard 0.35 mum 2P4M mixed-signal CMOS technology, is also presented and used to assess the model accuracy. The model predictions match the computer simulations.