Equalization of Third-Order Intermodulation Products in Wideband Direct Conversion Receivers

This paper reports a SAW-less direct-conversion receiver which utilizes a mixed-signal feedforward path to regenerate and adaptively cancel IM3 products, thus accomplishing system-level linearization. The receiver system performance is dominated by a custom integrated RF front end implemented in 130-nm CMOS and achieves an uncorrected out-of-band IIP3 of -7.1 dBm under the worst-case UMTS FDD Region 1 blocking specifications. Under IM3 equalization, the receiver achieves an effective IIP3 of +5.3 dBm and meets the UMTS BER sensitivity requirement with 3.7 dB of margin

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

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

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

A direct conversion receiver is demonstrated which operates in the presence of a rail-to-rail (+12.4dBm) out-of-band blocker and a -16.3dBm blocker, where the ICP1 is +12.5dBm and the uncorrected extrapolated IIP3 is +33.5dBm. IM distortion is adaptively cancelled via feedforward loops which are digitally expanded to reproduce higher order nonlinear reference terms. Cancellation improves input-referred total IM distortion by over 24dB, resulting in an extrapolated IIP3 of +45.3dBm

Digitally-Assisted Linearization of Wideband Direct Conversion Receivers

A SAW-less direct-conversion receiver is presented which utilizes a mixed-signal feedforward path to regenerate and equalize IM3 products, thus accomplishing system-level linearization. The receiver system performance is dominated by a custom integrated front end realized in 130nm CMOS and achieves an uncorrected out-of-band IIP3 of -7.1dBm under the worst-case UMTS FDD Region 1 blocking specifications. IM3 equalization results in an effective IIP3 of +5.3dBm and reduces total input-referred error by over 23dB

Acknowledgements

To my parents. i

Low power, low area digital to analog conversion

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 199-204).by Edward A. Keehr.M.Eng

Successive Regeneration and Adaptive Cancellation of Higher Order Intermodulation Products in RF Receivers

In this paper, a general framework for the adaptive feedforward cancellation of higher order intermodulation distortion (IMD) products is presented. By generating only second-order and principal-odd-order IMD reference products in the RF/analog domain and reproducing higher order IMD reference products at digital baseband, the proposed reference distortion scheme minimizes the analog hardware burden on the system. Inherent in this procedure is an approximation that the profile of blocking signals causing IMD is dominated by one very large blocker. The limitations imposed by this approximation are quantitatively examined and shown to permit cancellation ratios of nearly the square of the ratio between the dominant and nondominant blocking signal RMS amplitudes. An experimental receiver employing the proposed technique was constructed utilizing a wide-swing low-noise transconductance amplifier in order to accommodate a rail-to-rail (+12.4 dBm) out-of-band blocker and a -16.3-dBm nondominant blocker. The measured receiver out-of-band 1-dB desensitization point is +12.5 dBm and the peak uncorrected two-tone third-order intermodulation intercept point (IIP3) is +33.5 dBm. Utilizing the proposed IMD cancellation scheme in the presence of a modulated dominant blocker improves the total input-referred IMD error power by over 24 dB, resulting in an extrapolated IIP3 metric of +43.5 dBm