Impact Of Nonlinear Distortion Research Articles

Performance analysis of M ‐ary OQAM/FBMC with impact of nonlinear distortion over compound Rician K ‐factor unshadowed/κ−μ shadowed fad ing channels

Performance analysis of <i>M</i> ‐ary OQAM/FBMC with impact of nonlinear distortion over compound Rician <i>K</i> ‐factor unshadowed/κ−μ shadowed fad ing channels

Bidirectional radio-over-fiber system based on optical coupling single-sideband modulation

We demonstrate a bidirectional radio-over-fiber system based on optical coupling sing-sideband modulation, which can effectively reduce the impact of nonlinear distortion in transmission. With sidebands heterodyne detection, the system achieves 60-GHz wireless coverage. By optical carrier reusing, the base station can omit the laser source to make the system colorless. Through simulation analysis, the system has the credible transmission property both in downlink and uplink transmissions.

Performance analysis of orthogonal frequency division multiplexing‐based cooperative amplify‐and‐forward networks with non‐linear power amplifier over independently but not necessarily identically distributed Nakagami‐ m fading channels

In this study, performance analysis of variable-gain amplify-and-forward relaying orthogonal frequency division multiplexing-based systems over independently but not necessarily identically distributed Nakagami-m fading channels using non-linear power amplifier (PA) at the relay and maximal ratio combining scheme at destination. Specifically, novel closed-form expressions of outage probability and asymptotic outage probability are investigated for the considered system model. Further, an average symbol error rate (ASER) expression is derived for general-order rectangular quadrature amplitude modulation (RQAM) scheme using cumulative distribution function-based approach, which is also the novel contribution of the work. Since the transfer function of PA used at relay is nonlinear, this introduces non-linear distortion (NLD) in the considered system model. Thus, the impact of NLD and fading parameters on outage probability, diversity gain of the system and ASER performances are analysed. Further, the impact of NLD on constellation order for RQAM scheme is also discussed. The theoretical results are compared with computer simulations to verify the accuracy of the derivations. The derived expressions are generalised over variety of fading environments for integer-valued fading parameter.

Error Vector Magnitude Analysis of Uplink Multiuser OFDMA and SC-FDMA Systems in the Presence of Nonlinear Distortion

We analyze the impact of nonlinear distortion on the performance of uplink multiuser orthogonal frequency division multiple access and single carrier-frequency division multiple access systems in terms of the error vector magnitude (EVM). Based on the power spectrum density of the distortion noise, we derive a unified framework of theoretical EVM for both systems. The obtained results provide us approaches to evaluation of both the self-distortion and the inter-distortion interference from other users. In addition, simulation results agree well with our theoretical analyses.

WDM–OFDM–RoF system based on optical coupling tandem single-sideband modulation

The authors report on a WDM–OFDM–RoF system based on a novel optical coupling tandem single-sideband (O-TSSB) transmitter for one wavelength carrying two radio frequency signals. The impact of nonlinear distortion consisting of harmonic distortion and intermodulation distortion in this system is theoretically investigated and it has been found that the O-TSSB transmitter can reduce the nonlinear distortion effectively. Transmission over 25 and 50 km of standard single mode fiber is successfully demonstrated and it indicates that the modulation index 0.6 is more adapted to O-TSSB transmitter. The error vector magnitude of the system based on O-TSSB transmitter after transmission over 25 km is $$<$$ 0.05, relative to the traditional electric coupling tandem single-sideband transmitter. For O-TSSB transmitter, all channels after 25 km transmission achieve performance below the $$10^{-3}$$ forward error correction limit.

Impact of Nonlinear Distortion on Acoustic Radiation Force Elastography

High-intensity focused ultrasound (HIFU) produces an acoustic radiation force that induces tissue displacement, which can be measured by monitoring time shifts in the backscattered signals from interrogation pulses. If the pulse occurs simultaneously with the HIFU, the arrival time of the backscatter will be biased because nonlinearity associated with the HIFU changes the local sound speed. Measurements of the pressure field using 1.1 MHz HIFU and a 7.5 MHz pulse in water exhibited a nonlinearly induced apparent displacement (NIAD) that varied with the HIFU pressure, propagation distance and the timing of the pulse relative to the HIFU. Nonlinear simulations employing the KZK equation predicted NIADs that agreed with measurements. Experiments with chicken breast demonstrated a NIAD with magnitude similar to that expected from the radiation force. Finally it was shown that if two pulses were fired with different phases relative to the HIFU, then upon averaging, the NIAD could be mitigated.

Impact of nonlinear distortion in radio over fiber systems with single-sideband and tandem single-sideband subcarrier modulations

In radio over fiber (RoF) systems, two subcarrier modulations (SCMs), i.e., single-sideband (SSB) and tandem single-sideband (TSSB), have been widely used. Both SSB and TSSB SCMs can be obtained using optical Mach-Zehnder modulators. In this paper, the authors theoretically investigate the impact of harmonic distortion and intermodulation distortion in RoF systems for one wavelength carrying two radio frequency (RF) signals with either SSB or TSSB SCM. It is found that nonlinear distortion can be reduced when the frequency difference of two RF signals is /spl sim/ 1 GHz compared with /spl sim/ 2 GHz and higher for both TSSB and SSB SCMs, particularly for large modulation indexes. When the frequency difference of RF signals is /spl sim/ 2 GHz and beyond, either a small modulation index or a medium modulation index combined with a minimum RF of 6 GHz must be used, and a large modulation index cannot be used due to serious nonlinear distortion. Comparison of SSB and TSSB SCMs with uniform distribution of optical signal subcarriers in a dense wavelength-division-multiplexing RoF system with channel spacing of 12.5 GHz shows by simulation that SSB SCM is better (worse) than TSSB SCM for small (large) modulation indexes.