Direct RF sampling mixer with recursive filtering in charge domain

On the Suitability of Discrete-Time Receivers for Software-Defined Radio

“…A typical RF charge sampler is shown in Fig. 5, consisting of transconductor (G m ), pseudo-differential T/H stages with a pair of history capacitors (C h ) and rotating capacitors (C r ) [5]. Impedance Z p models the finite output impedance of G m together with all the parasitic impedance at node X.…”

“…due to the excellent component matching of capacitors [5] and the programmability to account for spread in process, voltage and temperature (PVT) and imperfections in simulation models [6]. These properties and especially the programmability feature can be very attractive for SDR applications.…”

RF Technology Enablers for Software-Defined Radios

“…Clearly, one of the major "pressure points" in future Sub-sampled quadrature downconverting mixer [8], [9]. The transfer function can be altered by changing the timing of the switches and the sub-samping ratio.…”

“…Clearly, a "breakthrough" in ADC performance would remove a significant barrier to the implementation of these multi-standard and reconfigurable systems. One final monolithic receiver approach that has recently been proposed utilizes sub-sampling, combined with a passive switched-capacitor FIR filter for downconversion [8], [9], one example of which is shown in Fig. 4.…”

Frequency-translation techniques for interference-robust software-defined radio receivers

“…Direct RF-sampling receivers seem to be a good candidate, both for better compatibility with CMOS scaling [47] However, all of these RF-sampling receivers are dedicated to one narrowband standard and all the aforementioned wideband receivers in Section 1.3.1 are based on RF mixing. Further research is needed to evaluate the suitability of RF sampling for SDR applications, and we will address this subject in Chapter 2.…”