Gain Imbalance Research Articles

A 38-GHz High-Speed I/Q Modulator Using Weak-Inversion Biasing Modified Gilbert-Cell Mixer

A 90-nm CMOS I/Q modulator with low dc-power consumption, low local oscillator (LO) power requirement, and high image reject ratio (IRR) is proposed in this letter. To minimize dc-power consumption and LO power requirement, the weak-inversion biasing technique is adopted in the switching transistors and the modified Gilbert-cell mixer structure is also applied to solve the voltage headroom problem in conventional Gilbert-cell mixer. Moreover, to demonstrate high IRR, a four-way quadrature signal generator with low phase and gain imbalance is implemented. With only 28.8-mW dc consumption and 0-dBm LO driving power, this I/Q modulator performs −2 ± 1-dB conversion gain and better than −35-dBc IRR from 34 to 39 GHz at 0.5-GHz IF frequency. Furthermore, due to the high IRR performance, 16-quadratic-amplitude modulation (QAM) and 256-QAM measurements with data rate of 4 and 1.6 Gb/s are successfully demonstrated at 38 GHz.

A $K\text{-}/Ka$ -Band Concurrent Dual-Band Single-Ended Input to Differential Output Low-Noise Amplifier Employing a Novel Transformer Feedback Dual-Band Load

A concurrent dual-band single-ended input to differential output (single-ended-to-differential) low-noise amplifier (LNA) employing a novel transformer feedback single-ended-to-differential dual-band load is proposed. The developed LNA topology is flexible in controlling the stopband notch frequency by optimizing the transformer’s self-inductance and coupling coefficient. It also has a unique advantage in controlling both the stopband rejection and passband gain balance, simultaneously. The LNA is designed using a 0.18- $\mu \text{m}$ BiCMOS process and exhibits the same single-ended-to-differential peak gains of 19.2 dB at 21.5 and 36 GHz in the low- and high-passband, respectively, with the stopband rejection ratio of 37.1 dB. In the single-ended input to single-ended output (single-ended) mode operation, the designed LNA exhibits the measured peak gains of 15.7/16.6 dB at 21.5 GHz and 15.7/16.7 dB at 36 GHz for the two signal paths. It achieves the best measured single-ended noise figures of 4.3/4.0 and 4.3/4.2 dB for the two signal paths in the respective low and high passbands. The LNA also attains the measured differential gain and phase imbalances of 0.9/1.0 dB and 0.5/10.4 degree in the low/high passband, respectively. This LNA is the first concurrent dual-band single-ended-to-differential LNA integrated on-chip operating in ${K}$ - and Ka -band.

Markov mode-multiplexing mode in OFDM outphasing transmitters

Outphasing transmitters have been explored to study the trade-off between linearity and efficiency. The outphasing technique enhances efficiency by operating two amplifiers at lower output amplitudes, using two constant envelope signals. Their major drawback is the inherent sensitivity to gain and phase imbalances between the two amplifier branches. Another important issue is related to the degradation of efficiency, especially in isolated combiners. This paper presents a Statistical Markov-Chain Mode-Multiplexing (MM) transmitter which combines features of the MM and Reverse MM-LINC. Commercial analog devices and a digital platform for signal processing purposes are used to test the performance with an orthogonal frequency multiplexing modulation (OFDM), which is one of the most used modulation schemes in wireless communication systems.

Active balun using resistive feedback for low gain imbalance

AbstractAn active balun using current steering topology is presented for phase and amplitude corrections. The proposed active balun is constructed with two different unit balun structures based on resistive feedback to reduce phase and amplitude errors. The first unit balun composed of the common source configuration provides a main transconductance stage for the proposed active balun. The second unit balun using common source and common gate configurations works for phase and gain error reduction. The resistive feedback proposed here leads to mitigation of phase error and then amplitude error, and an equation for deciding the feedback resistance is successfully deduced. The value of a feedback resistor is determined to provide the least phase and amplitude errors by optimizing the derived design equation. Designed and fabricated active balun in 65 nm CMOS process operates over 1.0–1.2 GHz band, showing input and output reflection coefficients under –10 dB, phase error under 3.5° and gain error under 1.4 dB over the frequency of interest. Moreover, the gain is measured to be 4 dB maximum and power consumption of 2.6 mW is measured.

Built-in-Self-Calibration for I/Q Imbalance in Wideband Millimeter-Wave Gigabit Transmitters

This paper addresses the estimation and compensation of I/Q imbalance, one of the most prominent impairments found in wideband zero-intermediate frequency transceivers (TRxs). The I/Q imbalance encountered in this kind of TRx comprises not only frequency-selective gain and phase imbalance but also delay imbalance. Unless appropriate compensation is applied, the I/Q imbalance significantly degrades the performance of a communication system. This paper presents a novel compensation technique for transmitter I/Q imbalance based on built-in-self-calibration, a low cost and robust compensation technique that enables manufacturing as well as in-field calibration with low computational complexity. The method’s performance is evaluated in a TRx with 64-quadratic-amplitude modulation and 2 GHz of bandwidth implemented with real hardware. The measurements show that the proposed technique achieves an image rejection ratio greater than 35 dB in the entire 2 GHz bandwidth and an error vector magnitude lower than 3%.

Research on the [formula omitted]-OTDR fiber sensor sensitive for all of the distance

In this paper, a modified construction for the traditional ϕ-OTDR fiber sensor sensitive for all of distance is presented, the related numerical simulation and experiment analysis results show that this construction can reduce the gain imbalance for all of the distance along the fiber caused by the Rayleigh scattering loss of the fiber and the gain imbalance of Raman fiber amplifier in this fiber sensor system. In order to improve further the vibration sensitivity of this system, the possible methods to restrain the influences of modulation instability effect, Stimulated Brillouin effect, reduce the amplified spontaneous emission (ASE) noises of Raman laser (RL) and Erbium3+-doped fiber amplifiers (EDFA), double Rayleigh backscattering noise in this system are discussed, which will offer a great reference value for the science research and engineering application in the field of fiber sensor as we believe.

Hardware Impairment Detection and Prewhitening on MIMO Precoder for Spectrum Sharing

Multiple input multiple out (MIMO) cognitive radio offer the spatial degree of freedom that can be used to share the spectrum with less interference via Precoding Technique. Many precoding techniques in the literature assume that the underlying hardware is ideal. In the practical case, hardware adds many impairments at both the transmitter and receiver side. Such hardware impairments degrade the performance of the MIMO system. This impairment introduces additional interference to the primary user in minimum interference precoder of MIMO cognitive radio and spoils the objective of the precoder. This paper analyzes the performance of the cognitive radio with minimum interference MIMO precoding in the presence of hardware impairment. Detecting the presence of hardware impairment and its exact variance is required to mitigate the impairment by prewhitening. In general all prewhitening work, it is assumed that the transmitter knows the presence of impairments and the exact variance of it. This work presents support vector machine (SVM) based hardware impairment detection technique on the real-time acquired data by using national instruments, vector signal generator (VSG) 5673. The VSG is configured in 2 × 2 MIMO setup to acquire the transmitter data without impairment and with injected impairment like DC offset, phase noise, I/Q gain imbalance, quadrature skew and frequency offset. After detecting the presence of hardware impairment by SVM, the variance of the data is calculated using Error Vector Magnitude (EVM) to enable prewhitening. The results show that the detection of hardware impairment can be possible with 100% of accuracy and the prewhitening scheme completely removes the impact of it.

Low power ultra wide-band balun LNA using noise cancellation and current-reuse techniques

A low power, single to differential (balun) low noise amplifier (LNA) using noise cancellation and current re-use techniques is presented for ultra wide-band applications. An upsurge balun LNA is designed using UMC 0.18-μm RF CMOS technology with an emphasis on the covenant between gain, bandwidth and power dissipation. The proposed balun exerts a differential stage on top of common gate-common source (CG-CS) stage. A CG-CS stage exploits amalgamation of CG stage (for wide-band impedance matching) and CS to curtail gain and phase imbalance, while simultaneously negating the noise and distortion of input matching transistor. The escalation of bandwidth has been accomplished using staggered tuning on CG-CS and differential stages. The stacked differential amplifier does cancellation of self noise as well as supply noise. The proposed UWB balun LNA achieves 14dB voltage gain with agreeable input reverse isolation (S11) of <-8dB over the frequency range of 3.19–8.8GHz. The minimum noise figure of 3.9dB and P1dB of −10.5dBm while exhausting 3.8mW from 1.2V supply. The superlative performance of balun LNA is accomplished between 3.19 and 8.8GHz with gain and phase errors below 0.2dB and 0.40 respectively. The layout occupying 0.77mm2 area. The overall pre and post layout simulations of proposed LNA shows admissible agreement with theoretical predictions.

A 2–15-GHz Accurate Built-in-Self-Test System for Wideband Phased Arrays Using Self-Correcting Eight-State $I/Q$ Mixers

A built-in-self-test (BIST) system for wideband phase arrays channels is presented. The BIST is implemented using an on-chip in-phase/quadrature ( $I/Q$ ) receiver with an integrated ring oscillator that provides both the channel test signal and the mixer local oscillator (LO). The BIST achieves wideband accuracy for relative phase and gain measurements at 2–15 GHz with a one-time self-correction algorithm with eight LO phases. The sequential algorithm determines the $I/Q$ errors, such as dc offset, gain and phase imbalances from the $I/Q$ outputs resulting from different LO phase states. An rms power detector network is also implemented for absolute gain measurements. The BIST can operate at rates >1 MHz (less than 1- $\mu \text{s}$ sampling time) with signal-to-noise ratio greater than 50 dB and provides measurements that agree well with the vector network analyzer S-parameter data over a wide frequency range. To the best of our knowledge, this is the first implementation of high accuracy wideband BIST system for phased-array channels.

Receiver Architecture for Frequency Offset Correction and I/Q Imbalance Compensation in Equal Bandwidth Contiguous Carrier Aggregation

A highly efficient receiver architecture for intraband contiguous carrier aggregation (CA) is described. The downconversion architecture is done in two stages; the first stage is done in the analog domain using a direct-conversion receiver, whereas the second stage is done in the digital domain using offset frequency digital mixing to separate the carriers. The novelty in the architecture stems from its ability to compensate for the different carrier frequency offsets (CFOs) between the two transmitted carriers, and unlike traditional approaches, the receiver uses a single complex digital mixer for baseband carrier separation. The receiver architecture also compensates for in-phase and quadrature gain and phase imbalance (IQI) inherent in direct-conversion receivers. It is shown that, in our new architecture, IQI compensation can be done post the digital mixer, thus enabling a low-power implementation to this impairment.

Optimal Multilevel ASK With Noncoherent Diversity Reception in Uncorrelated Nonidentical and Correlated Rayleigh Fading

A noncoherent quadratic diversity reception system for multilevel amplitude-shift keying (ASK) signals in Rayleigh fading with different cases of the channel covariance matrix is considered. These include the important case of distributed antennas, which exhibit uncorrelated fading with distinct mean-squared channel gains (uncorrelated nonidentical fading) and weighted energy detectors, and the cases of exponentially correlated and uniformly correlated channels with equal mean-squared channel gains. For these cases, closed-form expressions for the symbol error probability (SEP) of the system are derived using the decision statistics obtained from the maximum likelihood receiver. The problem of determining the optimal amplitude levels that minimize the SEP under a total signal energy constraint is formulated and solved analytically for the high signal-to-noise ratio (SNR) configuration and numerically for the general configuration. For the high SNR configuration, it is shown that the optimal ASK levels should follow an approximately geometric progression. It is also observed that an equally spaced ASK constellation is not optimal in terms of achieving the minimum SEP. Numerical results are presented to highlight performance trends for channel gain imbalance and correlation.

Phase and Gain Imbalance Compensation in Low-IF Receivers

Phase and Gain Imbalance Compensation in Low-IF Receivers

BER minimization for dual‐polarized wireless systems with polarization‐domain rotation

SummaryWe consider the problem of bit error rate (BER) degradation because of the power gain imbalance between horizontal (H)‐polarization and vertical (V)‐polarization components in an orthogonal dual‐polarization transmission system. To alleviate the aforementioned BER degradation problem, we propose a non‐orthogonal polarization‐domain rotation scheme where the axes of H‐polarization and V‐polarization components are rotated with different angles at the transmitter and de‐rotated at the receiver. In addition, in order to assess the effectiveness of the polarization‐domain rotation scheme, we derive the closed‐form BER expression under a practical dual‐polarized channel model, which is represented by cross‐polarization ratio and co‐polarization ratio (CPR). We also derive the approximated BER expressions for the two asymptotic values of CPR: balanced CPR and infinite CPR. With the derived BER expressions, we find the optimal rotation angles that jointly minimize the BER. According to the numerical results, it is shown that about 3dB Eb/N0 gain is obtained at the BER of 10−4 and the CPR of 10dB by the polarization‐domain rotation scheme with optimal rotation angles compared with the conventional orthogonal dual‐polarization transmission. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Abstract 3268: Gene expression associated to relapsing disease in Wilms tumor indicates a more differentiated phenotype unveiling a distinct transformation process for patients with a higher risk of relapse

Abstract Wilms Tumor (WT), originating through perturbation of developmental processes in embryonic kidney, is the most frequent pediatric genitourinary malignancy. Despite its overall survival rate has reached 90%, several patients develop relapses and, among them, approximately 50% will suffer of fatal disease. Hence, reduction of the relapse burden is key to improve WT outcome, and incorporation of novel prognostic markers is currently explored to achieve this goal. Chromosomal alterations and gene expression signatures in WT cohorts are thus examined to identify patients with risk disease. By evaluating gene expression profiles of 58 untreated primary tumor tissues from patients enrolled in the AIEOP multicenter protocol, we could identify four WT subtypes displaying enrichment for genes that were differentially expressed, and divergent clinical outcome. These patterns were validated against a previously published large WT cohort, confirming the accuracy of the prediction. A correlation analysis based on the expression of WT1, which deregulation is a crucial event in this disease, allowed us to verify known WT1 targets and to identify novel potential effectors implicated in this disease. However, although the majority or primary tumors from relapsing patients (7 out of 11) features lower WT1 level and increased 11p13 copy number (CN) losses, its expression did not significantly correlate with specific pathological parameters, confirming its poor prognostic impact as an independent disease predictor. Therefore, in order to reliably associate the risk of recurrence to a specific gene signature, we performed class comparison analysis of primary tumors between relapsing and non-relapsing patients. Unexpectedly, the pattern of genes up-regulated in relapsing tumors showed a negative enrichment of genes expressed in early embryonic kidney structures, such as the metanephric and cap mesenchyme, and a positive enrichment for genes expressed in nephrogenic structures developed upon mesenchymal-to-epithelial transition. These findings underscore the clinical heterogeneity of the disease and indicate that disruption of post-inductive renal processes occurs in high-risk WTs. Moreover, a few transcripts mapping at chromosome 1q21-44, with CN gain or allelic imbalance in 5/11 relapsing vs. 6/47 non-relapsing tumors, were found up-regulated in these patients. Remarkably, a few genes known to be implicated in metastatic disease in adult cancers, including SPP1, MUC1, MYC, CLDN1, and MAOA, showed up-regulation in relapsing WTs. Overall, our data suggests a gene signature associated to naive primary recidivant tumors, to be exploited as a potential predictor of disease at higher risk of relapse. Citation Format: Antonio Fiorino, Loris De Cecco, Beatrice Gamba, Edoardo Marchesi, Paola Collini, Andrea Pession, Marilina Nantron, Maurizio Bianchi, Filippo Spreafico, Silvana Canevari, Paolo Radice, Daniela Perotti. Gene expression associated to relapsing disease in Wilms tumor indicates a more differentiated phenotype unveiling a distinct transformation process for patients with a higher risk of relapse. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3268. doi:10.1158/1538-7445.AM2015-3268

On Small Terminal MIMO Antennas, Harmonizing Characteristic Modes With Ground Plane Geometry

multiple input–multiple output (MIMO) antenna systems are defined by fundamental figure of merits (FoM), such as branch imbalance, total efficiency, mean effective gain (MEG), and the correlation coefficient. Those FoM requirements are challenging, specially when applied to electrically small mobile devices, i.e., smart-phones, due to the form factor-reduced dimensions and multiplicity of adjacent frequency bands of operation. Uncorrelated antennas are especially important for MIMO antenna systems; other than few exceptional cases, the reduction of magnitude of complex correlation coefficient will increase the system capacity and data throughput. This work proposes an MIMO antenna system for mobile terminals, based on a realistic form factor and packaging implementation, with a very low magnitude of the complex correlation coefficient and an impressive isolation. An isolation better than 20 dB has been achieved using a folded monopole and a commonly adopted planar inverted F antenna (PIFA) on a platform with a very small form factor ( ${\bf{100}}\times {\bf{50}}\times {\bf{10}}\;\bf{mm}$ ). The proposed implementation is based on the synergy of two known techniques that consists in the: 1) reference ground plane geometry manipulation and 2) in the application of the characteristic mode theory to obtain orthogonal radiation modes. Since MIMO antenna systems at frequencies higher than 1.7 GHz are naturally proper isolated and decorreleated, this work demonstrates the proposed antenna topology enabling higher isolation and uncorrelated antenna system at 750 MHz, which is more difficult to achieve in form factors smaller than ${\bf{1}}\boldsymbol{\lambda}$ , while maintaining high total efficiency and adequate gain imbalance. In this paper, a simulation model and prototype ( ${\bf{1/4}}\boldsymbol{\lambda}$ long) measurement results are presented, demonstrating the implementation feasibility of such antenna system in realistic mobile device embodiment.

Built-In Self-Test of Transmitter I/Q Mismatch and Nonlinearity Using Self-Mixing Envelope Detector

Built-in self-test (BiST) for transmitters is a desirable choice since it eliminates the reliance on expensive instrumentation to perform radio-frequency signal analysis. Existing on-chip resources, such as power or envelope detectors or small additional circuitry, can be used for BiST purposes. However, due to limited bandwidth, measurement of complex specifications, such as in-phase and quadrature (IQ) imbalance, and third-order intermodulation intercept point (IIP3) is challenging. Since IQ imbalances are most amenable for digital compensation, their characterization and monitoring are desirable. In this paper, we propose a multistep BiST technique for transmitter IQ imbalance and nonlinearity using a self-mixing envelope detector. We derive analytical expressions for the output signal in linear and nonlinear modes. Using linear mode expression, we devise test signals to isolate the effects of gain and phase imbalances, dc offsets, and time skews from other parameters of the system in low-power mode. Once isolated, these parameters are calculated easily with a few mathematical operations. In the next step, using a higher power test signal, the nonlinear behavior of the transmitter is excited and the IIP3 of the transmitter is computed based on the analytical expressions. Simulations and hardware measurements show that the technique can provide accurate characterization of the path.

Practical Analysis of Impact of Transmitter Hardware Impairments for MIMO Channel Measurement

Multiple Input Multiple Output MIMO is one of the promising technologies for the high data rate wireless Communication and adapted in many wireless standards. MIMO Channel measurement is an essential process based on which the decoding of symbols, equalization and adaptive transmission can be implemented. Hence, real time measurement of MIMO channel response and characterization is important one. Many research works has been carried out in the area of MIMO channel estimation and measurements under the assumption of no hardware impairment. But the practical hardware suffer from hardware impairments like IQ gain imbalance, skew and phase noise. MIMO systems are very sensitive for the above impairments which degrades the achievable capacity of the MIMO system. This paper presents an experimental real time study of indoor MIMO capacity measurement incorporating the hardware impairments. Algorithms are written in LABVIEW and implemented in SDR platform of National Instrument 6.6 GHz vector signal generator PXIe 5673 and vector signal analyzer PXIe 5663.

An anti-image interference quadrature IF architecture for satellite receivers

Since Global Navigation Satellite System (GNSS) signals span a wide range of frequency, wireless signals coming from other communication systems may be aliased and appear as image interference. In quadrature intermediate frequency (IF) receivers, image aliasing due to in-phase and quadrature (I/Q) channel mismatches is always a big problem. I/Q mismatches occur because of gain and phase imbalances between quadrature mixers and capacitor mismatches in analog-to-digital converters (ADC). As a result, the dynamic range and performance of a receiver are severely degraded. In this paper, several popular receiver architectures are summarized and the image aliasing problem is investigated in detail. Based on this analysis, a low-IF architecture is proposed for a single-chip solution and a novel and feasible anti-image algorithm is investigated. With this anti-image digital processing, the image reject ratio (IRR) can reach approximately above 50dB, which relaxes image rejection specific in front-end circuit designs and allows cheap and highly flexible analog front-end solutions. Simulation and experimental data show that the anti-image algorithm can work effectively, robustly, and steadily.

A Wideband Inductorless Single-to-Differential LNA in &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$0.18 \mu{\rm m}$&lt;/tex&gt; &lt;/formula&gt; CMOS Technology for Digital TV Receivers

This study presents an inverter-based inductorless single-to-differential (S2D) wideband low-noise amplifier (LNA). The proposed LNA has three inverter-based gain stages with a global shunt feedback resistor for wideband input impedance matching. Moreover, a shunt capacitor with a current bias transistor in the third gain stage enhances the gain/phase imbalances and the linearity of the pseudo-differential outputs. When implemented in a TSMC $0.18$ - $\mu {\rm m}$ CMOS process, this wideband LNA covering DC-1.4 GHz achieves a ${\rm S}_{21}$ of 16.4 dB, a minimal input third-order intercept point (IIP3) of $ -13.3~{\rm dBm}$ , and a minimal noise figure (with output buffers) of 3 dB. The output gain and phase imbalances are less than 1 dB and 2.5 $^{\circ}$ , respectively, within 1 GHz. The chip consumes 12.8 mW from a 1.8 V supply.

Blind Self-Calibration Technique for I/Q Imbalances and DC-Offsets

The gain/phase imbalances and DC-offsets in the in-phase and quadrature branches in direct conversion transmitters (DCTs) are main sources of errors, especially at microwave frequencies and above. These impairments distort the spectrum of the transmitted signal and degrade the communications performance. In this paper, a blind technique based on higher order statistics is proposed to estimate the calibration parameters in order to compensate for these impairments. By minimizing a cost function composed of second and fourth moments of the modulator output signal, the DC-offsets, gain imbalance, and phase imbalance can be successively calibrated. The convergence of the proposed technique is also analyzed. This technique is blind in the sense that it does not require any prior knowledge about the DCT input signal, and is applicable to many communications systems including QAM, OFDM, and SC-FDMA. Computer simulations and experiments at 20 GHz demonstrate that the proposed technique can significantly improve the DCT performance in terms of local oscillator leakage and image suppressions.