Abstract
Even-order intermodulation distortions are often considered easy to filter in narrowband radio frequency (RF) wireless systems because they are usually located far away from the desired passband and adjacent bands. However, even-order intermodulation distortions have recently attracted more interest with the increasing popularity of wideband RF applications. The authors' previous work was devoted to establishing the power spectrum model of second-order intermodulation distortion. Motivated by the latest efforts on RF power amplifier linearization with second-order and fourth-order intermodulation, our focus now is to establish a power spectrum model of fourth-order intermodulation distortion which can be used to discuss the fourth-order impacts on the passband and adjacent bands. Here, together with the authors' previous work on the odd-order intermodulation, a relatively comprehensive power spectrum model is presented here, including second-, third-, fourth-, and fifth-order intermodulation, which offers a broader view for spectrum planners and RF designers. With qualitative and quantitative reasoning, we further explain that higher-order (i.e., n > 5 ) IM distortions of a weakly nonlinear amplifier are indeed negligible. The experiment measurement at the end of this paper validates the spectrum model.
Highlights
Nonlinearity in wireless communication systems usually exists in the radio frequency (RF) front ends and is produced by nonlinear devices such as power amplifiers, low-noise amplifiers, mixers, etc. [1,2,3]
The compensation or cancellation of the second-order IM distortion was suggested for wideband applications in long term evolution advanced (LTE-A) and fifth generation new radio (5G NR) systems [5, 6]
A Tek-In this paper, we developed a power spectrum model for the fourth-order IM distortion in terms of amplifier parameters, such as bandwidth, gain, and the fourth-order intercept point
Summary
Nonlinearity in wireless communication systems usually exists in the RF front ends and is produced by nonlinear devices such as power amplifiers, low-noise amplifiers, mixers, etc. [1,2,3]. Behavioural modelling of nonlinear devices plays an important role in the design of linearization techniques used to overcome the effects of nonlinear distortion in wireless applications. The compensation or cancellation of the second-order IM distortion was suggested for wideband applications in long term evolution advanced (LTE-A) and fifth generation new radio (5G NR) systems [5, 6]. A wideband inductorless low noise amplifier (LNA) was designed using a technique for canceling second-order IM products [7]. We derived a power spectrum model of the second-order IM distortion in our previous work [9]. A power spectrum model of fourth-order IM distortion is derived in terms of the amplifier parameters such as bandwidth, gain, intercept points, etc. A comprehensive power spectrum model up to fifth order is presented, which can be viewed as a blueprint for spectrum planners
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