Intermodulation Distortion Components Research Articles

Distortion Product Otoacoustic Emissions in Mice Above and Below the Eliciting Primaries.

Normal hearing is associated with cochlear nonlinearity. When two tones (f1 and f2) are presented, the intracochlear response contains additional components that can be recorded from the ear canal as distortion product otoacoustic emissions (DPOAEs). Although the most prominent intermodulation distortion component is at 2f1-f2, other cubic distortion products are also generated. Because these measurements are noninvasive, they are used in humans and in animal models to detect hearing loss. This study evaluated how loss of sensitivity affects DPOAEs with frequencies above and below the stimulating primaries, i.e., for upper sideband (USB) components like 2f2-f1 and for lower sideband (LSB) components like 2f1-f2. DPOAEs were recorded in several mouse mutants with varying degrees of hearing loss associated with structural changes to the tectorial membrane (TM), or with loss of outer hair cell (OHC) somatic electromotility due to lack of prestin or to the expression of a non-functional prestin. In mice with changes in sensitivity, magnitude reductions were observed for 2f1-f2 relative to controls with mice lacking prestin showing the greatest changes. In contrast, 2f2-f1 was minimally affected by reductions in cochlear gain due to changes in the TM or by the loss of OHC somatic electromotility. In addition, TM mutants with spontaneous otoacoustic emissions (SOAEs) generated larger responses than controls at 2f2-f1 when its frequency was similar to that for the SOAEs. Although cochlear pathologies appear to affect USB and LSB DPOAEs in different ways, both 2f1-f2 and 2f2-f1 reflect nonlinearities associated with the transducer channels. However, in mice, the component at 2f2-f1 does not appear to receive enhancement due to prestin's motor action.

Linearized microwave downconversion link based on fast and intelligent impairment equalization for noncooperative systems

We experimentally demonstrated the use of intelligent impairment equalization (IIE) for microwave downconversion link linearization in noncooperative systems. Such an equalizer is realized based on an artificial neural network (ANN). Once the training process is completed, the inverse link transfer function can be determined. With the inverse transformation for the detected signal after transmission, the third-order intermodulation distortion components are suppressed significantly without requiring any prior information from an input RF signal. Furthermore, fast training speed is achieved, since the configuration of ANN-based equalizer is simple. Experimental results show that the spurious-free dynamic range of the proposed link is improved to 106.5 dB · Hz2/3, which is 11.3 dB higher than that of a link without IIE. Meanwhile, the training epochs reduce to only five, which has the potential to meet the practical engineering requirement.

Performance projection of multi‐bias and nonlinear distortion for gallium arsenides nano‐pHEMT

AbstractIntermodulation distortion tests using the two‐tone technique with an extensive bias range were used to demonstrate the nonlinearity in terms of frequency for active devices like nano pHEMT based on gallium arsenide semiconductor material. It is demonstrated that the intermodulation distortion components are directly connected to the RF transconductance derivatives calculated using the two‐tone test. Furthermore, it was discovered that the third‐order intermodulation distortion power is lowest when the second derivative of the transconductance Gm3 is zero. To emphasize the influence of RF transconductance, a two‐tone approach has been presented as an empirical, analytical explanation for this device's nonlinearity. The modeled data is demonstrated to agree with the results of the measurements, making it a helpful tool for analyzing these devices.

RF/Linearity figures of merit estimation for GaAs and GaN/SiC-based Nano-HEMTs

The performance of three transistors, a GaAs HEMT, a pHEMT and a GaN/SiC HEMT, was compared. Measurements of the standard device properties have been performed on DC, RF, and nonlinearity characteristics to provide more linear design solutions, which helps the entire system perform properly. The GaAs pHEMT experienced a more comprehensive flat band transconductance profile. Still, the GaN HEMT showed higher power and frequency operation capability in terms of modified Johnson's figure of merit based on the cut-off frequency. In addition, the intermodulation distortion (IMD) components, third-order intercept point, IP3 at low frequencies, i.e., 53 MHz and increasing up to higher frequencies, 3.6 GHz and 7.0 GHz also reported. With the need for a sophisticated semiconductor device with high linearity and excellent power handling capacity, it is essential to look at DC, RF, and nonlinearity comparisons to give more linear design solutions for improving the overall system's performance.

A dual-channel microwave photonic mixer with large dynamic range

A microwave photonic mixer has the advantages of large transmission bandwidth, good frequency tunability, high isolation, and anti-electromagnetic interference. For the practical application of the multi-input multi-output (MIMO) communication system, a dual-channel, large dynamic range microwave photonic mixer is proposed in this paper. By controlling the bias angle of the modulator and applying a dual-polarization coherent receiver, the quadrature modulation and demodulation of the dual-channel radio frequency (RF) signal is realized. By constructing a heterodyne polarization light source and adjusting the laser power difference, the third-order intermodulation distortion (IMD3) component in the dual-channel frequency conversion signal can be suppressed. Moreover, due to the balanced detection technology, the second-order spurious-free dynamic range (SFDR2) and the third-order spurious-free dynamic range (SFDR3) of the system are simultaneously improved. Simulation results show that this scheme can obtain local oscillator-radio frequency (LO-RF) isolation of more than 40 dB, SFDR2 of more than 98 dB·Hz1/2, and SFDR3 of more than 115 dB·Hz2/3. In the 16quadrature amplitude modulation (QAM) vector signal test with 450 MHz bandwidth, the adjacent channel power ratio (ACPR) of the system is up to 53 dB and the error vector amplitude (EVM) is as low as 0.3%. Finally, the error analysis of the system is also carried out.

High-performance dual-band radio-over-fiber link for future 5G radio access applications

For the fronthaul between the baseband unit and the remote radio unit (RRU), radio over fiber (RoF) is promising to replace the Common Public Radio Interface in beyond fifth-generation and the sixth-generation wireless communication systems. The weight, size, and power consumption of the RRU can be greatly reduced, along with easy support for the millimeter-wave band. In this paper, a dual-band RoF link is proposed, where flexible switching between high-frequency (28 GHz) and low-frequency (3.5 GHz) RF channels is realized through polarization control. Single-sideband modulation is performed on 28 GHz signals to avoid periodic power fading during long-distance fiber transmission. By adjusting the DC bias, the third-order intermodulation distortion component in the 3.5 GHz signal is suppressed, and the spur-free dynamic range (SFDR) is improved. Experimental results show a channel isolation of above 43 dB. The link gain of the 28 GHz signal channel is flat, and the SFDR of the 3.5 GHz signal channel can reach 118.6 d B ⋅ H z 4 / 5 . In the case of RF vector signal transmission, the adjacent channel power ratio of the 3.5 GHz signal channel is optimally up to 48 dB, and the error vector magnitude is 2.9%.

All-optical linearized Mach-Zehnder modulator.

A practical, broadband, all-optical linearization concept for a Mach-Zehnder modulator (MZM) is proposed and demonstrated. The unique transmitter design includes an amplitude modulated (AM) standard MZM with two optical outputs, where the alternative (or complimentary) output is combined with the laser carrier to create a linearizing optical local oscillator, which when coherently combined with the AM signal fully cancels 3rd order intermodulation distortion components. Using this scheme, record linearity is achieved for a non-amplified RF photonic link, with spurious free dynamic range (SFDR) of 118.5 dB.Hz2/3 and 123 dB.Hz2/3 for single and dual fiber/photodetector schemes.

Linearized phase modulated microwave photonic link based on integrated ring resonators.

An on-chip linearization method for phase modulated microwave photonic link based on integrated ring resonators is proposed. By properly tailoring the phase and amplitude of optical carrier band and second-order sidebands, the third-order intermodulation distortion (IMD3) components can be suppressed. Theoretical analysis are taken and a proof-of-concept experiment is carried out. Experimental results demonstrate that IMD3 is suppressed by 21.7 dB. When the noise of the link is properly optimized, an SFDR of 112.7 dB·Hz2/3 can be achieved. This opens the possibility of integrating linearization into a functional photonic integrated circuit.

Experimental insight into the third‐order intercepts and nonlinear distortion of GaN HEMTs

This research is about investigating the third-order intercept point (TOI) and nonlinear distortion level (NDL) for two GaN HEMTs of different gate lengths with temperature and frequency. As a multi-biasing, input power, frequency and temperature-dependent term; the TOI point and as well as the nonlinear distortion level are particular figures merit relevant to the third-order intermodulation distortion (IMD3) product. The primary results are the output referenced TOI reduced whereas the input referenced TOI raised as the frequency goes higher and the lower gated device exhibits a bit greater magnitude. Over the temperature range measured; the magnitude of TOI and nonlinear distortion considerably changed in accordance to the performance of third order intermodulation distortion (IMD3) component. This investigation of TOI is used to determine what extent distortion is generated, and comparing that to the entryway of the antenna provides a clear strategy for determining if the spec can be met or not. However, distortion level investigation is a critical point to choose the best biasing preference with the device's inlet measurements to establish a solution that fits with the intended usage.

Improved Error Correction Methods for Filterless Digital Class D Audio Power Amplifier Based on FCLNF

Aiming at correcting the error caused by the nonlinear and power supply noise of the bridge-tied-load (BTL) power stage of the filterless digital class D power amplifier, an error correction method was proposed based on feedforward power supply noise suppression (FFPSNS) and first-order closed loop negative feedback (FCLNF) techniques. This method constructed the first-order LCLNF loop for the power stage and further reduced the impact of the power supply noise on the power amplifier output by using FFPSNS technology to introduce the power supply noise into the feedback loop at the same time. The 0.35 μm CMOS process is used for analysis and comparison in Cadence. Cadence simulation results indicate that PSRR at the power supply noise frequency of 200 Hz is improved with 36.02 dB. The power supply induced intermodulation distortion (PS-IMD) components are decreased by approximately 15.57 dB and the signal-to-noise ratio (SNR) of the power amplifier is increased by 17 dB. The total harmonic distortion + noise (THD + N) of the power amplifier is reduced to 0.02% by FCLNF + FFPSNS.

A Wideband Highly Linear Distributed Amplifier Using Intermodulation Cancellation Technique for Stacked-HBT Cell

In this article, a wideband linearization technique for distributed amplifiers (DAs) is presented. In particular, an auxiliary transistor is employed to create additional intermodulation distortion components that will be feed-forwarded to the output of each gain unit cell to significantly suppress the third-order intermodulation (IM3) distortion. To verify the concept, two DAs are fabricated in an indium phosphide (InP) process. One amplifier employs a conventional stacked-heterojunction bipolar transistor (HBT) gain unit cell, and the other linearized amplifier utilizes the proposed technique. The linearized DA exhibits a measured gain of 10.5 dB with a 3-dB gain bandwidth from dc to 90 GHz. The maximum 1-dB gain compression output power ( $P_{\text {1 dB}}$ ) is 20.5 dBm, and the third-order intercept point (OIP3) is 33 dBm. Compared to the conventional amplifier, the two values are improved by 3.5 and 4.5 dB on average, respectively. Moreover, the linearization technique only increases very little dc power consumption at high power and has the same chip size as compared to the conventional design. To the best of the authors’ knowledge, compared to published state-of-the-art DAs, the proposed DA achieves among the highest OIP3 over a wide bandwidth.

Study of third-order intercepts and nonlinear distortion level for S-H GaAs HEMTs

Third-order intercept (TOI) and nonlinear distortion level (NDL) are studied for two GaAs based single heterostructure HEMTs of different gate width such as (200 μm × 0.5 μm) and (150 μm × 0.5 μm). The TOI being a specific figure of merit is a biasing, input power, frequency-dependent term which is related to the third-order intermodulation distortion (IMD3) component and the study extended from low to high temperatures. The main findings are that the output referenced TOI decreased while the input referenced TOI increased with frequency. Within the measured temperature range, the TOI and NDL change significantly following the behaviour of the IMD3 component. This data would offer assistance in a way that enhances insight of the performance of the GaAs based device working at high frequency and temperature to evaluate the impacts of device nonlinearity on the affectability of the radio and to identify a distortion-free operation.

Third-order intercepts and nonlinear distortion level investigation for pre and post multilayer pHEMTs

Investigation of the third-order intercept point, IP3 and nonlinear distortion level, NDL for pre-and post-multilayer processed GaAs pHEMTs has been accomplished by employing two-tone intermodulation distortion measurements. The third-order intercept point is a biasing, input power, frequency-dependent term, particularly related to the fundamental and third-order intermodulation distortion component and the study extended from low to high temperatures. The main findings are that the output referenced OIP3 decreased while the input referenced IIP3 increased with frequency at peak transconductance condition and the study further extended to multi-bias operation condition. Within the measured temperature range, the IP3 and NDL modified significantly following the behaviour of IMD3 distortion. This investigation of IP3 is utilized to measure how much distortion is created and referring this to the antenna input gives a straightforward strategy to decide whether or not the spec can be met. On the other hand, analysis of NDL is vital for choosing the most excellent biasing alternative with the entryway measurements of the device to create a compromise agreeing to the desired utilization.

Digitally Assisted Harmonic Cancellation for Multi-Octave Filter-Less Transmitter

This paper presents and demonstrates the design of a filter-less transmitter architecture with digitally assisted harmonic cancellation. A neural network is used to model the harmonics as well as IMD for digital predistortion applications. This neural network-based harmonic modeling does not require any reference signal to be injected at the input of PA, thereby reducing the complexity in characterizing the harmonics. An in-house 10 W PA operating from VHF to L-band has been designed and characterized for its harmonic suppression. This PA is used along with agile RF transceiver AD9361 from Analog Device and Xilinx embedding platform using Zynq ZC-706 system-on-chip for implementing the entire transmitter. The receiver of AD9361 captures the nonlinearity of the PA in terms of harmonics as well as intermodulation distortion (IMD) components for modeling and predistortion. The proposed architecture can handle all types of distortions due to hardware as well as PA nonlinearity. Besides, it is also able to cancel the harmonics using a harmonic injection in the feed-forward configuration. This transmitter architecture has the advantages of being low cost, filter-less, wideband, frequency agile, reconfigurable and less bulky compared to the conventional scheme. The proposed scheme is demonstrated to transmit 5 MHz LTE signal at different frequencies over the range of 100 MHz to 400 MHz. In such a case, the second and third harmonics appear over the frequency range from 200 MHz to 1.2 GHz, which are within the amplification range of PA, yet they are suppressed without using any filter at the output. More than -40 dBc harmonic rejection is achieved over the entire operating range of this filter-less transmitter. The adjacent channel leakage ratio (ACLR) is always better than -45 dBc after applying digital predistortion.

Thermal response for intermodulation distortion components of GaN HEMT for low and high frequency applications

Thermal effect on intermodulation distortion (IMD) behavior of GaN based high-electron mobility transistor (HEMT) have been researched over input power and frequency using a two-tone technique. A significant modification was observed in terms of magnitude on the linear component and the magnitude as well as the position and appearance of the nulls/notches of the nonlinear components was changed conspicuously. The parasitic resistances and as well as the output current were affected when applied input power increases. As a result, an increase in the output IMDs found and the device threshold voltage VT moves towards more negative of Vgs trace which in turn shifts the notch points of the nonlinear IMDs towards lower values of applied bias Vgs. The values of the output IMDs degrades with the increment of temperature and frequency. The output IMD products also reduced following the transconductances response to temperature. On the other hand, the notch/null's position of the nonlinear IMDs also moves following the thermal response of threshold voltage. This authentic and exhaustive study is crucial to figure out the minimum distortion, maximum gain bias option for active devices.

Analysis of nonlinear distortion and its reduction using feedback injection schemes in an [formula omitted] transistor laser

In this work, we analyze the third and fifth order intermodulation distortion components and its reduction in an 1.3μm transistor laser by feedback harmonic injection technique. The device is modeled by rate equations, which are numerically solved by fourth order Runge–Kutta method. The second harmonic and IMD3 components available at the collector are added with the base current separately, to reduce the distortions. Modulation Bandwidth of 11 GHz and modulation depth of 92.1% are obtained for Ib=7.5 mA. An improvement of 12.64 dB and 4.3 dB are obtained for IMD3 and IMD5, under second harmonic injection scheme, at a bias current of 7.5 mA. In the case of combined second harmonic and IMD3 feedback injection, a reduction of 13.33 dB and 4.49 dB is obtained. Similarly, SFDR of 63.7 dB/Hz2∕3 and 64 dB/Hz2∕3 are obtained for the first and second schemes respectively.

2D curtailed harmonic memory polynomial for reduced complexity in concurrent dual‐band modelling and digital predistortion with the second band at harmonic frequency

Multi-band transmitter systems are evolving to support the smooth transition from 4G to 5G communication systems. Moreover, recent developments of multi-band and ultra-wideband power amplifiers have led to a possible scenario where the second carrier signal is transmitted at the harmonic frequency of the first carrier signal. This results in harmonic interference from the first carrier signal as well as additional cross-modulation and intermodulation distortion (IMD) components, which cannot be filtered out. The computational and memory requirements for digital predistortion (DPD) in such scenario increase drastically to include all interference terms. This study presents a novel two-dimensional curtailed harmonic memory polynomial (2D-CHMP) model to capture harmonic interferences, cross-modulation and IMDs. The model complexity and memory requirement of 2D-CHMP are very less as compared to the state-of-the-art two-dimensional harmonic memory polynomial (2D-HMP) model. For proof-of-concept, it is shown with two different measurement setups that the proposed 2D-CHMP DPD provides similar linearisation performances as compared to the 2D-HMP DPD with less number of coefficients and computational complexity. As a study, it is shown that the proposed model can be further adapted to a low-precision (low-bit) environment by utilising principal component analysis.

Photonic receiving and linearization of RF signals with improved spurious free dynamic range

A linearization scheme for receiving broadband radio frequency (RF) is theoretically analyzed and experimentally demonstrated. The system uses three intensity modulators (IMs) to impose a two-tone RF signal on an optical carrier. We demonstrate that the linearization technique can be used to suppress the third-order inter-modulation distortion (IMD3) and the five-order inter-modulation distortion (IMD5) components simultaneously. An improvement of the spurious free dynamic range (SFDR) as large as 112.13 dB in 1-Hz bandwidth is achieved, which is 13.5 dB higher than the SFDR of a conventional intensity-modulated scheme.

Design techniques for mitigation of intermodulation distortion components in CMOS RF receiver front-end circuits with subthreshold operation

This paper provides an overview of target applications and design aspects for emerging radio frequency front-end circuits with subthreshold biasing to reduce power consumption. Design methods are described to linearize a subthreshold pseudo-differential common-source cascode low-noise amplifier (LNA) and a subthreshold active mixer. The linearization techniques can improve the third-order intermodulation intercept point (IIP3) through the use of passive components, which implies that they do not require auxiliary amplifiers to suppress third-order distortion components, and therefore do not incur any extra power consumption. A 1.95 GHz receiver front-end chip with a narrowband LNA and down-conversion mixer was designed and fabricated in 110 nm CMOS technology. Measurement results show that the linearized low-power front-end has a 20.6 dB voltage gain, a 9.5 dB double sideband noise figure, and a − 10.8 dBm IIP3 with a power consumption of 0.9 mW.

Linearized phase-modulated analog photonic link with the dispersion-induced power fading effect suppressed based on optical carrier band processing.

A linear phase-modulated photonic link with the dispersion-induced power fading effect suppressed based on optical carrier band (OCB) processing is proposed. By introducing a proper phase shift to the OCB, the third-order intermodulation distortion (IMD3) component of the signal transmitted over a length of fiber is effectively suppressed, while the fundamental component is shifted to be away from the notch point of the transmission response. The IMD3 and the dispersion-induced power fading effect are effectively suppressed simultaneously to realize a linear phase-modulated photonic link, and the simplicity is preserved. Theoretical analyses are taken and an experiment is carried out. Simultaneous suppression of IMD3 and dispersion-induced power fading effect is achieved. An improvement of larger than 10 dB in third-order spurious-free dynamic range (SFDR3) for both the RF frequency around the notch point and the peak point of the transmission response curve for a 20-km link is realized, as compared with the traditional phase-modulated photonic link without the OCB processing.