Generation of Multi-Gigabit-per-Second MQAM/MPSK-Modulated Millimeter-Wave Carriers Employing Photonic Vector Modulator Techniques

In this paper, two photonic vector modulator (PVM) architectures are presented, and their use in generating multi-gigabit-per-second M-ary quadrature amplitude modulation/M-ary phase shift keying modulated RF carriers in the millimeter-wave frequency regime is experimentally demonstrated. First, a highly scalable photonic quadrature amplitude modulation (QAM) architecture based on vector summation and dispersive delay lines, which directly generate multilevel signals from parallel in-phase and quadrature components, is proposed and experimentally demonstrated by generating up to 3-Gb/s quadrature phase shift keying (QPSK), four-level amplitude shift keying, and eight-level QAM at 39-GHz-modulated carriers. The possibility of also detecting the baseband components is shown, which allows the simultaneous feeding of baseband/RF signals over the same infrastructure. This architecture is limited to a certain length of fiber, as the quadrature condition is obtained for a certain aggregated dispersion. To overcome this limitation, a second PVM architecture is proposed, which is based on the use of two Mach-Zehnder modulators in parallel and an optical delay line to obtain the quadrature condition. The generation of a 2-Gb/s QPSK signal is experimentally demonstrated, including a 1-km standard single-mode-fiber transmission.     

Direct 16 QAM six-port modulator

A direct 16 quadrature amplitude modulation (QAM) modulator based on the six-port technique is proposed. It uses a six-port passive microwave network to implement the modulation scheme with suitable terminations. A microwave prototype was built to validate the 16 QAM modulation up to 200 Mbit/s data rate at 4.2 GHz carrier frequency. The error vector magnitude and local oscillator (LO) power testing show that this six-port 16 QAM modulator has wide dynamic range capability to overcome the LO power variation. It has potentially low cost and low power consumption for RF communications applications.     

A multicarrier QAM modulator for WCDMA base-station with on-chip D/A converter

In this paper, design and implementation of a multicarrier quadrature amplitude modulation (QAM) modulator for a wideband code division multiple access (WCDMA) base-station with a 14-bit on-chip D/A converter is described. The modulator is capable of modulating four carriers with four independent in phase (I) and quadrature (Q) data streams. The proposed modulator structure consists of an interpolation chain for data streams and four digital frequency synthesizer/modulators, which are based on a coordinate rotation digital computer (CORDIC) vector rotation algorithm. The interpolation chain consists of a root-raised cosine pulse shaping filter and three half-band filters for image filtering. The modulated carriers are combined to form a multicarrier WCDMA signal. The SINC-attenuation effect of a digital/analog (D/A) converter is canceled by an inverse-SINC predistortion filter. The multicarrier signal is converted to the analog domain with a 14-bit current steering D/A converter, which is integrated on the same silicon chip. The modulator is implemented with a 0.35-mum BiCMOS process with CMOS transistors only     

A frequency-agile single-chip QAM modulator with beamformingdiversity

Architecture and circuit design techniques for VLSI implementation of a single-chip quadrature amplitude modulation (QAM) modulator with frequency agility and antenna beamforming characteristics are presented. In order to achieve reliable wireless communication modem function, the single chip all-digital QAM modulator implements various features, including high data rates with bandwidth efficiency, flexibility, meeting a wide variety of user throughput requirements with variable and width and data rates in a multi-user system, and robustness, incorporating diversity and redundancy techniques to guarantee robust communication for various operating environments. The modulator components consist of several digital processing building blocks, including various finite-impulse-response (FIR) filters, an innovative variable interpolation filter, a four-channel frequency translator with quadrature mixer for antenna beamforming diversity, a quadrature direct digital frequency synthesizer (QDDFS), a numerically controlled oscillator (NCO), a QAM formatter, a pseudorandom noise (PN) generator, an x/sinx filter, and a microcontroller interface. An optimized architecture and chip implementation for the variable modulator is derived and evaluated which will support symbol rates from 6 kBaud to 8.75 MBaud continuously and digitally flexible IF frequencies up to 70 MHz with four-channel antenna beamforming function     

Design of Broadband Highly Linear IQ Modulator Using a 0.5$mu$m E/D-PHEMT Process for Millimeter-Wave Applications

A broadband highly linear IQ modulator using a 0.5-mum enhancement/depletion-pseudomorphic high-electron mobility transistor process is presented in this letter. An innovative broadside/edge coupler is proposed to apply to the IQ modulator. The chip size is only 1times1 mm², including radio frequency and baseband PADs. The sideband and local oscillation suppressions of the modulator are better than -33 and -15 dBc, respectively. At a carrier frequency of 60 GHz with a 64 quadrature amplitude modulation (QAM) modulation, the modulator demonstrates an error vector magnitude of within 3%, and an adjacent channel power ratio of better than -40 dBc. To the best of the authors' knowledge, this work demonstrates the best modulation quality with a 64 QAM modulation up to 60 GHz among all the reported reflection-type IQ modulators.     

Some effects of delay and modulation-index mismatch on cochannel FM interference

The baseband distortion resulting from the cochannel interference of two FM carriers nominally carrying the same modulation is considered. Such distortion was observed to plague VHF mobile telephone service in Phoenix, Ariz. This distortion arises when the landline audio delay and modulation indices of the two transmitters are not closely equalized. Both sinusoidal and Gaussian modulation age analyzed. Curves presented indicate that baseband distortion power as large as 20 percent of baseband signal power may occur for an RF carrier amplitude ratio of 0.7 and an unequalized delay of the order of 200 µs when the minimum rms transmitter phase deviation is 2 rad. Increasing the deviation to 4 rad reduces the distortion to the 5-percent range. The desirability of large index modulation in this context is thus apparent.     

High Average-Efficiency Multimode RF Transmitter Using a Hybrid Quadrature Polar Modulator

This paper presents a hybrid quadrature polar modulator (HQPM) to drive the power amplifier (PA) highly efficiently in a wireless RF transmitter required for multimode operation. For enhancing the transmit efficiency, a switching-mode PA realized as Class-E design is used in the transmitter. The HQPM consists of a quadrature modulator for processing the RF modulated carrier and a Class-S modulator for processing the supply-voltage signal. The quadrature modulator and the Class-S modulator deliver the output signals with proportional envelope variation before being inserted into the RF-input terminal and the supply-voltage terminal of a Class-E PA, respectively, causing the double envelope modulation to distort the modulated RF signal at the PA output. Therefore, a digital predistorter is embedded in the HQPM for compensation. The proposed HQPM-based transmitter can help reducing the average dc and input RF powers and the output feedthrough levels so as to enhance power added efficiency and adjacent channel power rejection remarkably.     

Linearization of 1.3-μm MQW electroabsorption modulators usingan all-optical frequency-insensitive technique

A novel all-optical linearization technique has been developed for discrete multiquantum-well electroabsorption modulators by exploiting the wavelength dependence of the quantum-confined Stark effect. The correcting signal for a particular order of nonlinearity is generated by the same modulator at a detuned optical wavelength, canceling the undesired order of nonlinear distortion via coherent RF recombination at the photodetector. This dual-wavelength approach is simple and insensitive to the microwave subcarrier frequency. A dramatic 30-dB reduction in the third-order nonlinear distortion at 10 GHz and 8-dB increase in the suboctave link dynamic range were achieved experimentally     

超宽带射频发射机中直接正交调制模块的研制

研制了应用于多带-正交频分复用(MB-OFDM UWB)射频发射机中的直接正交调制模块,分析了直接正交调制方案应用于MB-OFDM UWB系统中的优势。设计出的直接正交调制模块具有体积小、功耗低等特点,满足FCC规定的射频指标要求,并已成功应用于MB-OFDM UWB的演示系统中。     

基于CPLD的64QAM解调器的实现

针对QAM调制解调技术在移动通信中的应用,提出了一种基于Altera公司的CPLD器件和Micro-devices公司的RF2713（单片集成正交调制解调芯片）器件,用VerilogHDL硬件描述语言实现64QAM（正交幅度调制）解调器后端编码设计的思想和方法.该方法具有一定的扩展性,并且用EPM7128SLC84-15实现了该设计.通过修改VerilogHDL程序可以适应256制式的QAM解调.     

A 3.1-4.8 GHz transmitter with a high frequency divider in 0.18 μm CMOS for OFDM-UWB

A fully integrated low power RF transmitter for a WiMedia 3.1-4.8 GHz multiband orthogonal frequency division multiplexing ultra-wideband system is presented. With a separate transconductance stage, the quadrature up-conversion modulator achieves high linearity with low supply voltage. The co-design of different resonant frequencies of the modulator and the differential to single (D2S) converter ensures in-band gain flatness. By means of a series inductor peaking technique, the D2S converter obtains 9 dB more gain without extra power consumption. A divided-by-2 divider is used for carrier signal generation. The measurement results show an output power between -10.7 and -3.1 dBm with 7.6 dB control range, an OIP3 up to 12 dBm, a sideband rejection of 35 dBc and a carrier rejection of 30 dBc. The ESD protected chip is fabricated in the Jazz 0.18/zm RF CMOS process with an area of 1.74 mm~2 and only consumes 32 mA current (at 1.8 V) including the test associated parts.     

Full constellation phase detector for carrier recovery in high-order QAM systems

A full constellation phase detector that improves carrier acquisition performance in high-order quadrature amplitude modulation (QAM) is proposed. The weighting function of the phase detector is mathematically derived, and simulated phase detector characteristics are presented for 256QAM. The results of an experimental evaluation are also reported, which show that the carrier recovery loop based on the proposed phase detector has a large frequency acquisition range and low phase tracking error in high-order QAM.     

A closed form to predict outage of digital radio

A simplified formula for predicting the outage probability of an unprotected high capacity line-of-sight digital radio link operating under frequency-selective fading conditions is presented. First, the propagation anomaly is modeled as a linear in-band amplitude dispersion in conjunction with a transmission minimum (notch) frequency located within or outside the signal band of interest. A simplified expression for the outage probability of the radio system under these conditions is then obtained. This expression is based on the fade occurrence factor in the climatic region of interest, the bandwidth of the transmitted signal, the carrier frequency of operation, the modulation scheme employed and the length of the link under consideration. The formula is applied to predict the outage probability of 4 phase shift keying (PSK), 8-PSK, and 16 quadrature amplitude modulation (QAM) high capacity radio links with specified parameters. The results obtained compare favorably with measured data     

基于单边带调制的直接探测光OFDM-RoF系统研究

研究基于单边带调制(SSB)的直接探测光正交频分复用-光载射频(OFDM-RoF)系统的性能。10Gbit/s的二进制数据信号经过QAM符号映射和OFDM调制后,与10GHz射频信号混频并驱动双电极LiNbO3马赫-曾德尔调制器(LN-MZM)产生SSB-OFDM信号,调制信号通过光纤传输至基站,进行直接探测转换为毫米波电信号后再无线发送到用户端。仿真结果证实,OFDMRoF系统在4QAM和16QAM两种调制格式下的EVM都满足FEC的要求。同时,理论分析并仿真验证存在一个最佳调制指数可以使信号传输性能达到最佳,并且最佳调制指数与光纤长度无关。     

Effects of radio-frequency exposure (100-kHz to 500-kHz) onvery-high-speed digital data transmission system using a copperloop

This paper describes our investigation of the effect of radio frequency (RF) exposure on the performance of a very-high-speed digital data transmission system called the Asymmetrical Digital Subscriber Lines (ADSL) using the uncoded quadrature modulation (QAM) scheme at a rate of approximately 1.6 Mb/s and which operates within the 100- to 5OO-kHz frequency band. The effect of different wideband emissions within the ADSL band, including the background radio noise in the environment and emissions from light dimmers, fluorescent lamps, motors, and other household appliances on the customer's premises were investigated. Also, the effect of RF exposure caused by radiation from high-power licensed transmitters, such as LORAN-C, coastguard transmitters, and radiobeacons, were investigated. A complete database of information for these transmitters was acquired. The coupled voltage caused by radiation from the transmitters was predicted by using a detailed electromagnetic interference (EMI) model that was developed and experimentally verified. Field surveys near LORAN-C stations in New York, New Jersey, and California were performed. For the study on spurious emission-like background radio noise, light dimmers, invisible fences, and emission from diesel engines, it was found that these sources inside the customer's premises may not generate potential interference to the system. Minimum distances (critical distance) that should be maintained between the ADSL receiver and the interfering radio transmitters (LORAN-C radiobeacons) were obtained for the 18 ADSL test loops. Initial study of multiple exposure caused by several transmitters radiating at different frequencies, but all within the ADSL band, showed that such an effect should not generate any potential interference within the 100- to 500-kHz band     

110 GHz vector modulator for adaptive software-controlledtransmitters

A 110 GHz MMIC vector modulator for use in low-cost, high-performance, radar and communication transmitters is presented. The circuit consists of two push-pull (bi-phase) attenuators arranged in phase quadrature and has dimensions of 1.7× 1.4 mm². The fabricated MMIC has been characterized by means of static S-parameter measurements and shows a minimum insertion loss of 12 dB at 110 GHz, Using these measurements, the required baseband input levels for a 64-QAM static constellation were determined. These levels were then applied at 10 MSample/s, by an arbitrary waveform generator, to demonstrate a 60 Mb/s data rate transmitter operating at 110 GHz. To date, this represents the highest reported RF frequency for direct multilevel carrier modulation using monolithic technology     

基于电流矢量和的多模QAM直接数字调制器

 本文提出了一种新型直接数字正交幅度调制器(QAM),可用于4-QAM,16-QAM或更高阶调制方式.其基于电流矢量相加的原理,首次采用一对跨导可调的高速运算跨导放大器产生幅值可控的基本电流矢量,开关网络在电流域中选择矢量相加,减小了非线性失真.该芯片采用0.13μm CMOS工艺进行流片.在5.4GHz载波频率、16Mbps数据率时的测试结果显示,16-QAM调制的EVM为6.2%,芯片面积0.09mm²,在1.2V电源电压下总直流功耗为20mA.     

利用基带直调信号注入锁定半导体激光器产生全光上变频信号的研究

提出了一种将低速基带信号直调产生的宽谱信号,注入至用于上变频的分布反馈式半导体激光器(DFB-LD),利用调制信号光谱中的高阶分量对从激光器进行相位锁定,从而产生光学上变频信号的方法。对直调信号注入锁定DFB-LD产生光学上变频信号的机理进行了理论分析,完成了2.5Gb/s伪随机码基带信号通过直调并注入从激光器,分别产生了30,35,40GHz副载波频率的全光上变频信号的实验,并在时域和频域上,对上变频信号的特征进行了研究。该方案结构简单,无需高速外调制器及高频本振,具有集成潜力,理论上可产生更高载频(如60GHz),对目前的光-无线混合接入提供了一种可行的解决方案。     

Bit-Based SLM Schemes for PAPR Reduction in QAM Modulated OFDM Signals

In this paper, we propose two bit-based selected mapping (SLM) schemes for reducing peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals with quadrature amplitude modulation (QAM), called bitwise SLM (BSLM) and partial bit inverted SLM (PBISLM). Contrary to the conventional SLM which rotates the phases of QAM symbols in the frequency domain, the proposed schemes change the magnitudes as well as the phases of QAM symbols by applying binary phase sequences to the binary data sequence before mapped to QAM symbols. Simulation results show that the proposed schemes have better PAPR reduction performance with shaping gain than the conventional SLM scheme for the QAM modulated OFDM signals, especially for the small number of subcarriers.      

All-optical photonic signal processors with negative coefficients

A new technique to generate all-optical negative coefficients in photonic signal processors is presented. It is based on using a dual-output Mach-Zehnder modulator, excited with two wavelengths, to obtain radio-frequency (RF) signal modulated optical carriers in opposite phase, together with a wavelength selection scheme to separate each wavelength and to perform the function of producing negative taps. This eliminates the need to convert to the electrical domain to obtain subtraction and also eliminates the speed, noise, and distortion limitations of previous optical cross-gain modulation approaches. Experimental results on a high-skirt-selectivity bandpass filter demonstrate the all-optical negative coefficient generation mechanism and show the synthesis of high-speed negative taps in the optical domain.