A flexible receiver using ΔΣ modulation
This paper presents a reconfigurable 2nd/3rd-order discrete-time direct RF-to-digital ΔΣ receiver architecture for wide frequency range flexible receivers. Using 25% duty-cycle current-driven passive mixer along with RF feedback enables high-Q bandpass filtering and relaxes the linearity requirement on LNTA. Moreover, the passive/active implementation of the loop filter gives a good trade-off between power consumption, linearity and dynamic range. A design example with 10 MHz useful bandwidth and 0.4-4.0 GHz frequency range is conducted to demonstrate the feasibility and the characteristics of this proposed architecture.