New Closed-Form Expressions for the Prediction of Multitone Intermodulation Distortion in Fifth-Order Nonlinear RF Circuits/Systems

Abstract

This paper presents a rigorous analytic approach for the prediction of the in-band and out-of-band intermodulation distortion of fifth-order memoryless nonlinear RF circuits/systems modeled using a Taylor series and driven by phase-aligned or random phase multitone excitation. Nonlinear distortion figures-of-merit such as intermodulation ratio (IMR), adjacent channel power ratio, co-channel power ratio, and noise-to-power ratio, as well as the output power density can be straightforward computed using newly developed closed-form expressions. Simulation results of output power density obtained using the developed expressions for an -band commercial amplifier demonstrates the time efficiency and robustness of the proposed approach when compared to averaged data obtained using numerical simulators such as Agilent ADS. The comparison of the computed nonlinearity figures-of-merit with those previously published shows the importance of considering the fifth order when modeling nonlinear RF circuits/systems. The proposed analytical approach explicitly highlights the dependency of the normalized figures-of-merit relative to the standard two-tone IMR (IMR 2 ) to the input power and to the coefficients of the Taylor model contrary to third-order-based approaches.

Analytical performance evaluation of the OFDM systems passing through nonlinear circuits

“…In the case of OFDM and other multi-tone signals, from the above description is inferred that a large number of intermodulation distortion (IMD) products are generated. We calculate the number of IMD products using of combinatorics and of the generating function technique in particular [6]. For the assessment of a circuit's nonlinear characteristics, circuit designers make use of either the 1-dB compression point or the input/output inferred third order intercept points (IIP3/OIP3 ).…”

A Flexible Dual-Inflection Point Rf Predistortion Linearizer for Microwave Power Amplifiers

“…Predistortion linearizers [7][8][9][10][11][12][13][14][15][16] are widely used in linearizing the PAs due to, their wide bandwidth, ease of use and their ability to be appended to existing amplifiers as a separate stand-alone module. The predistortion linearizers, in fact, introduce equal and opposite gain and phase distortion at the input of the PA to correct for the actual encountered distortion in the gain and phase characteristics of the final output.…”

“…Predistortion linearizers employing a microcontroller for the control of various parameters were reported in [7,8]. These types of linearizers exhibit gain and phase characteristics opposite in orientation to that of the PAs to be characterized.…”

On the effects of memoryless nonlinearities on M-QAM and DQPSK OFDM signals

“…In [18], Liu presents an approximate SNR evaluation. In [19], Boulejfen et al applied the methodology in multitone signals through fifth-order nonlinear distortion and derived new closed-form expressions for the relevant figures-of-merit. In this study, we are mainly interested in deriving closed-form expressions for the carrier SNR to allow for using the results for BER and SER estimations.…”

“…Calculations of the number of IMD products due to thirdorder nonlinearities already exist in the literature (e.g., [16] and [19]). Extending the previous use of combinatorics, we examine the effect of IMD distortion in the presence of phase noise and of additive Gaussian noise channel.…”