Analysis of Internally Bandlimited Multistage Cubic-Term Generators for RF Receivers

Abstract

Abstract-Adaptive feedforward error cancellation applied to correct distortion arising from third-order nonlinearities in RF receivers requires low-noise low-power reference cubic nonidealities. Multistage cubic-term generators utilizing cascaded nonlinear operations are ideal in this regard, but the frequency response of the interstage circuitry can introduce errors into the cubing operation. In this paper, an overview of the use of cubic-term generators in receivers relative to other applications is presented. An interstage frequency response plan is presented for a receiver cubic-term generator and is shown to function for arbitrary three-signal third-order intermodulation generation. The noise of such circuits is also considered and is shown to depend on the total incoming signal power across a particular frequency band. Finally, the effects of the interstage group delay are quantified in the context of a relevant communication standard requirement.

Digitally Enhanced Alternate Path Linearization of RF Receivers

“…Values for γ and E sat were extracted from simulated device models and found to be 0.55 and 1.8 V/µm, respectively. Although γ is traditionally thought to be greater than unity in submicron devices, this result is consistent with other recent reports of noise in submicron CMOS devices [39,41]. H (ω LO − ω 2 )/H (ω LO − ω 1 ) was simulated and found to be equal to 0.8.…”

Mitigation of Reverse Intermodulation Products at Colocated Base Stations

“…j2π∆fû n/fs (19) where (12) and (19) shows that the synthesization process would further require a frequency offset ∆f correction such that, ∆fû − ∆f = ∆f u (20) and a gain-phase correction ρ such that,…”

“…If the auxiliary receivers include noise (and other error) terms, n a and n b , from receiver Rx1 and Rx2 respectively, then equation (19) becomes:…”

“…Similar circuits can be used to linearize receivers. The authors [18] and [19] used analog circuits to synthesize a distortion estimate for use in a digital adaptive postdistortion cancellation technique. Analogue squaring and cubing circuits often have inherent complexities such as direct feed-through, DC-offsets, temperature drifts and poor noise performance.…”

A rail-to-rail input receiver employing successive regeneration and adaptive cancellation of intermodulation products

“…The odd path IM term generator utilizes a multistage architecture as in [4] but with a CMOS input stage in order to increase the dynamic range for a given current. The even path IM term generator consists of a buffered canonical squaring transconductor that feeds directly into a TIA.…”