Error Vector Magnitude Measurements Research Articles

A 1024-QAM Analog Front-End for Broadband Powerline Communication Up to 60 MHz

A high performance analog front-end (AFE) for broadband powerline communication between 1.6 and 60 MHz is presented. The frequency division multiplexing AFE supports optimum channel selection, avoids disturbing RF signals and allows co-existence with other users of the spectrum. The direct-conversion receiver operates linearly up to a + 18 dBm input level. Tunable low-pass filters, integrated into the receive path, support a wide class of service requirements by channel bandwidth selection. The dynamic range is 99.5 dB for 2 MHz channels, and 90.5 dB for 16 MHz channels. Error vector magnitude measurements are presented for a single-carrier 1024-QAM and a 1024-carrier 64-QAM signal as function of frequency and channel attenuation. For 1024-QAM, the error vector magnitude (EVM) is below or equal to 1.2% rms up to 60 dB of attenuation, whereas the 1024-carrier 64-QAM performs well up to 80 dB of attenuation. The presented chip was fabricated in a 0.25 mum SiGe BiCMOS process, and the measured power consumption from a single 2.5 V supply is 668 mW.

Crossover Digital Predistorter for the Compensation of Crosstalk and Nonlinearity in MIMO Transmitters

This paper proposes a novel crossover digital predistorter (CO-DPD) model to compensate for crosstalk and nonlinearity in multiple-input multiple-output (MIMO) radio systems. Crosstalk can take place before or after the power amplifiers, designated herein as nonlinear and linear crosstalk, respectively. This paper demonstrates that, contrary to linear crosstalk, nonlinear crosstalk significantly affects the performance of the digital predistortion algorithm; and, it cannot be embedded and compensated for by the conventional channel matrix inversion algorithm at the receiver side of MIMO links. Based on a parametric study of system-level simulations and measurements, it was found that for a -20-dB nonlinear crosstalk level, the use of a memory multibranch polynomial predistorter, along with the channel matrix inversion algorithm, bounds the adjacent channel power ratio (ACPR) for a wideband code division multiple access (WCDMA) signal to -46 dBc and the error vector magnitude (EVM) for a world interoperability for microwave access (WiMAX) signal to -43 dB in MIMO links. The proposed CO-DPD was investigated and analyzed for the MIMO transmitter with N = 2, where N is the number of RF front-ends. Its performance was evaluated through measurements, the experimental results obtained show that, in the presence of -20-dB nonlinear crosstalk, the proposed CO-DPD improve the ACPR of the WCDMA signal by 13 dB to -56.81 dBc from those obtained using a conventional digital predistorter. The same improvement was observed in the EVM measurement of the WiMAX signal, where the EVM decreases from -21.22 dB for the conventional DPD to -49.71 dB for the proposed CO-DPD.

Digital Baseband Predistortion Based Linearized Broadband Inverse Class-E Power Amplifier

A newly introduced inverse class-E power amplifier (PA) was designed, simulated, fabricated, and characterized. The PA operated at 2.26 GHz and delivered 20.4-dBm output power with peak drain efficiency (DE) of 65% and power gain of 12 dB. Broadband performance was achieved across a 300-MHz bandwidth with DE of better than 50% and 1-dB output-power flatness. The concept of enhanced injection predistortion with a capability to selectively suppress unwanted sub-frequency components and hence suitable for memory effects minimization is described coupled with a new technique that facilitates an accurate measurement of the phase of the third-order intermodulation (IM3) products. A robust iterative computational algorithm proposed in this paper dispenses with the need for manual tuning of amplitude and phase of the IM3 injected signals as commonly employed in the previous publications. The constructed inverse class-E PA was subjected to a nonconstant envelope 16 quadrature amplitude modulation signal and was linearized using combined lookup table (LUT) and enhanced injection technique from which superior properties from each technique can be simultaneously adopted. The proposed method resulted in 0.7% measured error vector magnitude (in rms) and 34-dB adjacent channel leakage power ratio improvement, which was 10 dB better than that achieved using the LUT predistortion alone.

다중 대역 송신을 위한 디지털 사전 왜곡 기법을 이용한 비선형 전력 증폭기의 고조파 신호 선형화

본 논문에서는 입력 복소 포락선 신호와 m차 고조파 대역의 출력 복소 포락선 신호 사이의 비선형성 관계를 이론적으로 분석하고, 이를 모델링하기 위하여 AM/<TEX>$AM_m$</TEX>, AM/<TEX>$PM_m$</TEX>을 정의하였다. 제안된 모델을 측정 데이터로부터 추출하는 방안을 제안하였고, InGaP 전력 증폭기에 대하여 기본 주파수 대역과 3차 고조파 대역에서의 신호를 측정하여 제안된 모델 및 기법의 유효성을 검증하였다 또한, 제안된 고조파 신호 대역에 대한 모델을 기반으로 고조파 대역 신호의 선형화를 위한 디지털 사전 왜곡 기법을 제안하였다 디지털 사전 왜곡기에서 비선형역함수 구현을 위해 수치 해석적인 방법과 Look-Up Table(LUT) 방식을 이용하였다. 고조파 신호 선형화를 위한 디지털 사전 왜곡기를 포함하는 송신기를 구현하고 16-QAM과 64-QAM의 입력 신호에 대해서 3차 고조파 출력신호의 스펙트럼과 I/Q 신호 성상도를 측정하였다. 고조파 대역에서 비선형 왜곡에 의해서 의미 없는 신호는 제안된 기법으로 구성된 송신기에 의해 선형화되었으며, 그 결과 각 신호에 대한 Error-Vector Magnitudes(EVM)이 6.4 %와 6.5 %로 측정되었다. 제안된 기법은 향후 SDR과 CR 등의 차세대 다중 대역 송신 시스템에 적용될 수 있을 것으로 사료된다. In this paper, a nonlinear relationship between an input complex envelope and an output complex envelope of m-th harmonic zone is theoretically analyzed, and AM/<TEX>$AM_m$</TEX> and AM/<TEX>$PM_m$</TEX> are defined. A scheme to extract these characteristics from measured in-phase and quadrature-phase data is suggested. The proposed analysis is verified with a fundamental-fundamental and fundamental-third harmonic measurements for a InGaP power amplifier(PA). Based on the harmonic-band nonlinear analysis and extraction scheme, a new technique to send a signal in m-th harmonic band with a harmonic signal Linearization Digital Predistortion(DPD) scheme is presented. A numerical analysis and a Look-Up Table(LUT) based DPD algorithms to linearize output signal on m-th harmonic zone are developed. For a 16- and a 64-QAM input signals, a DPD for third harmonic signal linearization is implemented, and output spectrum and signal constellation are measured. The wholly distorted signals are linearized, and thus the measured Error Vector Magnitudes (EVM) are 6.4 % and 6.5 % respectively. The results show that a proposed scheme linearizes a nonlinearly distorted harmonic band signals. The proposed nonlinear analysis and predistortion scheme can be applied to multiband transmitter in next generation software defined radio(SDR)/cognitive radio(CR) wireless system.

High-Efficiency Hybrid EER Transmitter Using Optimized Power Amplifier

This paper describes a new design approach for a power amplifier (PA) of the highly efficient hybrid envelope elimination and restoration (H-EER) transmitter. Since the PA operates mostly at the average power region of the modulation signal, power-added efficiency (PAE) of the PA at the average drain voltage is very important for the overall transmitter PAE. Accordingly, the PA is designed to have a maximum PAE in that region. The performances of the proposed PA and a conventional PA under H-EER operation are evaluated via ADS and MatLab simulations using a behavioral large-signal model of a silicon LDMOSFET, which verifies that the proposed PA has significant advantages for the H-EER transmitter in both PAE and output power. A saturated amplifier, inverse class F, has been implemented using a 5-W peak envelope power LDMOSFET for 3GPP forward-link single-carrier wideband code-division multiple-access at 1 GHz with a peak-to-average power ratio of 9.8 dB. An envelope amplifier is built that has an efficiency of above 68% and peak output voltage of 31 V for an interlock experiment. The overall PAE of the transmitter with a conventional PA is 35.5% at an output power of 29.2 dBm. On the other hand, the transmitter with the proposed PA delivers significantly improved performances: PAE increased by 4% and output power by 2.5 dB. The H-EER transmitter has been linearized by the digital feedback predistortion technique. The measured error vector magnitude is reduced to 1.47% from 6.4%. These results clearly show that the proposed architecture is a good candidate for efficient linear transmitters.

Transmission of Multi-Band OFDM and Impulse Radio Ultra-Wideband Signals Over Single Mode Fiber

In this paper we examine the transmission of two types of ultra-wideband (UWB) signals, multiband orthogonal frequency division multiplexing (MB-OFDM) and impulse radio ultra-wideband (IR-UWB), over single mode fiber at 1550 nm. In order to investigate the impact of optical components such as laser diode, external modulator and single mode fiber on UWB signals, we develop mathematical models for these components. These models are experimentally verified and corresponding numerical parameter values are obtained by experiment. Using these models we discuss the transmission of two types of UWB signals over single mode fiber. A new figure of merit namely distortion factor is defined. Using this figure of merit the direct modulation of distributed feedback (DFB) laser diode and the external modulation with Mach-Zehnder modulator (MZM) are compared in terms of their impact on UWB signals. Using intensive simulation we also compare MB-OFDM and IR-UWB in terms of their sensitivity to the distortions of a UWB over fiber link using error vector magnitude (EVM) as a figure of merit. An EVM measurement is accomplished for a MB-OFDM over fiber link. The impact of IR-UWB pulse shape on its resistance to the nonlinearity of modulation transfer function is also investigated.

Optical multicarrier generator for radio-over-fiber systems

We propose an optical multicarrier generation method for radio-over-fiber (ROF) systems. The multicarrier generator is composed of a phase-modulated laser and two chirped fiber Bragg gratings used as flattening filters. The chirped gratings are spectrally tailored to equalize the intrinsically uneven envelope of the phase-modulated laser spectrum. A flattened multicarrier spectrum with 7 carriers at a frequency spacing of 12.5 GHz is demonstrated with less than 2 dB peak-to-peak variations and 40 dB optical signal-to-noise ratio (OSNR). We evaluate the quality of the multicarrier generator by using it as an externally modulated source for 802.11 compliant signals. We performed error vector magnitude (EVM) measurements on each of the filtered carrier and found an average value of 32.8 dB compared to 36.2 dB for a tunable laser source. The results show that the multicarrier source could be used for error free transmission.

Transmission of Multiple HD-TV Signals Over a Wired/Wireless Line Millimeter-Wave Link With 60 GHz

For the first time to our knowledge, we demonstrate a transmission of 37 channels a 64 quadratic-amplitude-modulation (QAM)-coded high-definition television (HD-TV) signal over a fiber-optic millimeter-wave link. The 60-GHz upconverter/downconverter is implemented based on a Gunn oscillator and a nonradiative dielectric waveguide. For the remote delivery of 37 channels of HD-TV signal through 20 km of single-mode fiber, we use a laser diode operating at 1554 nm and an electroabsorption modulator. We evaluate the performances of HD-TV by measuring error vector magnitude and confirm transmission qualities by observing video contents coded with moving picture expert group-2 (MPEG-2).

Design of an All-Digital Transmitter Architecture via Binary Sequence Search and a Look-Up Table Approach to Modulation

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents a practicable scheme for building a high-frequency direct-digitizing transmitter. The transmitter uses a simple look-up table to generate a binary output stream, which is then filtered to produce a radiated signal, so that there is no need for precise digital-to-analog converters. The data in the look-up table is produced by a new constrained-list-decoding algorithm operating over the real alphabet. The transmitter can only be a modulator, or a combined encoder and modulator. The technology presented in this paper supports the generation of RF signals for commercial applications. The 10-Gbit DSP architectures currently produced for ethernet, for e.g., can be used directly to transmit these binary sequences. The paper concludes with spectra and error vector magnitude measurements for Gaussian minimum shift keying (GMSK) and quadrature phase shift keying (QPSK) with frequencies over 10 GHz. </para>

Radio‐optic demonstrator for distributed antenna system indoor wireless applications using low‐cost VCSELs

AbstractIntegration of wireless and optical networks would offer a potential solution for high bandwidth, mobility and cost reduction in the access networks. Radio over optical fibre (RoF) combines the capacity of optical networks with the flexibility and mobility of wireless access networks. In this paper, an economic demonstrator for RoF indoor applications is proposed using in‐building pre‐installed multimode fibre (MMF), low cost 850 nm VCSELs and 50 µm MMF pigtailed photodiodes. The system is dedicated to Distributed Antenna System (DAS) indoor wireless applications. To evaluate our system, error vector magnitude (EVM) measurements and eye‐diagrams have been demonstrated. Copyright © 2007 John Wiley &amp; Sons, Ltd.

High-Efficiency Envelope-Tracking W-CDMA Base-Station Amplifier Using GaN HFETs

A high-efficiency wideband code-division multiple-access (W-CDMA) base-station amplifier is presented using high-performance GaN heterostructure field-effect transistors to achieve high gain and efficiency with good linearity. For high efficiency, class J/E operation was employed, which can attain up to 80% efficiency over a wide range of input powers and power supply voltages. For nonconstant envelope input, the average efficiency is further increased by employing the envelope-tracking architecture using a wide-bandwidth high-efficiency envelope amplifier. The linearity of overall system is enhanced by digital pre-distortion. The measured average power-added efficiency of the amplifier is as high as 50.7% for a W-CDMA modulated signal with peak-to-average power ratio of 7.67 dB at an average output power of 37.2 W and gain of 10.0 dB. We believe that this corresponds to the best efficiency performance among reported base-station power amplifiers for W-CDMA. The measured error vector magnitude is as low as 1.74% with adjacent channel leakage ratio of -51.0 dBc at an offset frequency of 5 MHz

Simultaneous Dual Band Transmission Over Multimode Fiber-Fed Indoor Wireless Network

Performance measurements of different combinations of digital enhanced cordless telecommunications packet radio service, global system for mobile communications, universal mobile telecommunication service, and 802.11g (54 Mbps) signals in a dual band configuration transmitted over an indoor wireless network fed by a low-cost 850-nm vertical-cavity surface-emitting laser (VCSEL)-300m multimode fiber link are presented. The feasibility of such a system is demonstrated with error vector magnitude measurements which are within the required specifications.

ソフトウェア無線受信機用０．８‐５．２ＧＨｚ帯広帯域ＳｉＧｅ‐ＭＭＩＣ直交ミクサ

For the next generation wireless terminals used in the software defined radio (SDR), multi-band / multi-mode transceivers and their MMIC are required which cover the wide RF frequency range from several hundreds MHz up to several GHz. In this paper, 0.8-5.2GHz broad-band SiGe-MMIC quadrature mixer (Q-MIX) for multi-band / multi-mode direct conversion receiver has been developed. By using a static type frequency divider as a 90 degrees local (LO) power divider, measured error vector magnitude (EVM) of less than 3.1% can be achieved in the cases of 0.8/2.1GHz W-CDMA and 5.2GHz wireless Local Area Network (LAN) (IEEE 802.11a) reception. This Q-MIX also shows broad-band characteristic for base-band signal and is applicable for 4G cellular. By using fabricated Q-MIX, a multi-band / multi-mode (1.9GHz (3rd generation cellular (W-CDMA)) / 5.2GHz (4th generation cellular (Multi-Carrier (MC)-CDMA))) receiver has been developed and it has firstly demonstrated the successful reception of motion picture via W-CDMA and MC-CDMA.

All-optical frequency up-conversion for WLAN over fiber applications

This paper investigates up-conversion of a 54-Mb/s 802.11a WLAN signal in a radio-over-fiber (RoF) link. The frequency conversion is realized using either a DFB laser diode or an electro-optical modulator (EOM) (both biased in nonlinear regimes). Very low error-vector magnitude (EVM) measurements are reported at minimum of transmission of electro-optical modulator for a large 802.11a input power range, and an acceptable EVM degradation is obtained using the cost-effective LD mixing technique, but with a limited input power range. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 421–424, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21369

PER and EVM Measurements of a Radio-Over-Fiber Network for Cellular and WLAN System Applications

This paper investigates the transmission characteristics of an optical signal that is modulated by a radio-frequency signal using an electroabsorption modulator (EAM). The transmission performances of the radio-over-fiber (ROF) system were evaluated at cellular bands of 900 MHz, 1.8 GHz, 1.9 GHz, and 2.1 GHz and at ISM bands of 2.4 GHz and 5.8 GHz for wireless local area network and intelligent transportation systems applications. Error vector magnitude (EVM) and packet error rate (PER) measurements were carried out to evaluate the performance. Bias voltages of the EAM and bias currents of a distributed feedback laser diode were varied for the evaluation of the optical power measurements.

Broad-band HBT BPSK and IQ modulator MMICs and millimeter-wave vector signal characterization

Reflection-type binary phase-shift keying and in-phase and quadrature modulator monolithic microwave integrated circuits (MMICs) are reported in this paper. These MMICs are fabricated by 1-/spl mu/m HBT process and evaluated successfully under vector signal characterization. A cold-mode HBT device model with varying bias conditions is proposed, which is suitable for millimeter-wave circuit design and simulation. The analysis and design equations of imbalance effects for the reflection-type modulators are also presented. These MMICs demonstrate measured error vector magnitude of less than 12%, a carrier rejection of better than 15 dB, and an adjacent channel power ratio of better than -21 dBc from 50 to 110 GHz.

Direct radio-frequency digital angle modulator

A radio frequency angle modulator is proposed with a direct digital data interface using 0.18 µm CMOS technology. It consumes 42 mW, occupies a chip size of 0.936×0.935 mm, and shows a measured error vector magnitude of 0.55% at 2.468 GHz with 5.5 Mbit/s data rate.