Tunable active front-end realized by using zero-IF down and up converters for to be used in software defined radios

摘要

The proposed tunable Active BPF which is operating within 30-512 MHz band is realized by using the Zero-IF active Down and Up converters. The operating frequency of the circuit is adjusted by fixing the frequency of the LO which drives the both converters. The bandwidth of the circuit is adjusted by changing the band-width of the active Base-Band LPF which is placed between the two converters. The circuit behaves as a Low-Noise, Narrow-Band Tuned RF Front-End Amplifier with+17 dB Moderate Gain andHigh Selectivity. The input IIP3 is around 5dBm. A single stage NMOS common-gate balanced amplifier is situated at the input to provide the impedance matching and the sharp selectivity. The voltage-series reactive-capacitive feedback is applied to the first stage in order to raise its input impedance for the purpose of impedance matching at the input port as well as for improving its dynamic range and its bandwidth. Implemented in 0.18um CMOS process technology, a tunable, band-pass 30-to-512 MHz receiver front-end with achieves a maximum of 3.5 dB NF, +18 dB gain, +3dBm IIP3 across the operating band.