A broadband polynomial predistorter for reconfigurable radio

Abstract

Abstract

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

“…Predistortion circuits using cascaded Gilbert cell multipliers have been implemented with discrete components [17] and in BiCMOS [18] and CMOS [19] processes. Nielsen et al [20] propose the use of multipliers modified from [21] that are based on a sum-and-difference squaring technique which utilizes the square-law dependence of the MOS transconductance but have not reported on a complete predistortion circuit to the knowledge of the authors of this paper.…”

“…3 was implemented for the receiver in [9] and will be the focus of this paper. Like those of [17]- [19], it utilizes multiple nonlinear operations to generate third-order distortion, and hence, much of the analysis in this paper applies to these architectures as well. The first nonlinear operation in this case is performed by the simple MOS squaring transconductor in the lower left-hand corner of the schematic.…”

“…Another important requirement in systems only correcting for third-order nonlinearities is to minimize the ratio of fifth-order intermodulation (IM5) to IM3 products [10], [16], although the authors of [17] have shown that even an ideal cubic predistorter affects the IM5 products at the output of the amplifier and limits the performance of the system in their work. Cubing gain has also been mentioned as important in order for the predistorter to more easily match the amplitudes of the IM3 products in the PA [13], [16].…”

“…This was done as the simulation models available for this work permitted a more realistic and constant value of the noise parameter over than did the short-channel noise model. In this case, the PSD at the input of the balun is given by (17), where is the transconductance of one of the input devices and is the Boltzmann's constant. Note that the dummy input devices contribute to this quantity as well (17) As shown in Fig.…”

“…In this case, the PSD at the input of the balun is given by (17), where is the transconductance of one of the input devices and is the Boltzmann's constant. Note that the dummy input devices contribute to this quantity as well (17) As shown in Fig. 8, the thermal noise of the input devices referred to the input of the Gilbert multiplier has a bandpass characteristic due to the frequency response discussed in the previous section.…”