Analytical and Experimental Study on Suppression of Electromagnetic Interference on High Speed Printed Circuit Board for Wireless Communication Systems

In this paper, a novel routing topology is proposed to reduce crosstalk between parallel links used for high data rate application. Generally, microstrip lines are used in high frequency RF printed circuit boards for propagating high speed signals in wireless communication. Since RF front end modules in wireless system supports a wide ultra wide band frequency range from 700 MHz to 12 GHz, package density parasitic effects have been a major issue which degrades system performance. The close proximity of signal transmission lines with a high packing density results signal integrity problems such as crosstalk and timing jitter. A modified coupled microstrip line is proposed to reduce crosstalk by means of increasing capacitive coupling ratio. Our proposed structure reduced far end crosstalk by 4 dB and near end crosstalk by 4 dB than existing structures. The proposed microstrip line increased the maximum data rate from 1 to 3.3 Gb/s and reduced timing jitter by 51 ps at 3.3 Gb/s.     

一种无线宽带收发机I/Q失配校准和补偿技术

本文提出一种基于数字基带的无线宽带收发机中的发射链路I/Q失配的校准和补偿技术。数字基带发射用于I/Q失配校准的信号,经过RF收发机的发射链路、由平方功率检测器、带通滤波器组成的校准通路以及RF接收机的可变增益放大器,数字基带采集此信号并估计I/Q失配的大小,完成I/Q失配的校准和补偿,此技术相比于射频的自校准节省了面积和功耗。本技术已经成功用于IEEE802.11n,可以实现50dB以上的镜像抑制,完全满足了系统要求。     

Impact of pointing errors and turbulence effects on POLSK and coherent OWC-based FSO system over generalized turbulence channel model

The emerging technology in wireless communication, free space optics (FSO) offers a myriad of merits over current radio frequency links due to its wide license-free bandwidth, ease of installation, high security features and viable cost for short-distance communication. Its unparallel high-speed data rate and immunity against electromagnetic interference makes FSO the emerging technology of today. Atmospheric conditions like absorption, scattering, turbulence and pointing error prevail during wireless transmission. Through this paper we aim at elucidating the effect of the error introduced by misalignment between the transmitter and receiver that are ideally required to be in the line of sight rendering pointing error. Pointing error and turbulence effects are the main limitation parameters for our analysis. For this purpose, we have taken into consideration three different modulation techniques polarization shift keying, coherent OWC and on–off keying FSO communication system. We derived the novel expressions for the average spectral efficiency (ASE) over the generalized turbulence model for these modulation techniques. The ASE is analyzed against average transmitted optical power with the maximum ASE of 50 bits/s/Hz at the transmitted power of 10 dBm for coherent OWC technique.     

5~6GHz自适应线性化偏置的InGaP/GaAs HBT功率放大器

针对高质量无线局域网的传输需求,设计了一款工作在5~6 GHz的宽带磷化镓铟/砷化镓异质结双极型晶体管(InGaP/GaAs HBT)功率放大器芯片。针对HBT晶体管自热效应产生的非线性和电流不稳定现象,采用自适应线性化偏置技术,有效地解决了上述问题。针对射频系统的功耗问题,设计了改进的射频功率检测电路,以实现射频系统的自动增益控制,降低功耗。通过InGaP/GaAs HBT单片微波集成电路(MMIC)技术实现该功率放大器芯片。仿真结果表明,功放芯片的小信号增益达到32 dB;1 dB压缩点功率为28.5 dBm@5.5 GHz,功率附加效率PAE超过32%@5.5 GHz;输出功率为20 dBm时,IMD3低于-32 dBc。     

Performance of orthogonal frequency division multiplexing based M-ary quadrature amplitude modulation in asymmetrical dual-hop mixed RF-FSO transmission system

This paper investigates the performance of a dual-hop mixed relay system with radio frequency (RF) and free-space optics (FSO) communication under the effect of pointing error (PE) and atmospheric turbulence (AT). This paper considers a system where RF and FSO links are cascaded. The RF link is modeled by Nakagami-m fading, and the FSO link is modeled as gamma–gamma (G-G) fading channel. Both the channel models use orthogonal frequency division multiplexing (OFDM) with M-ary quadrature amplitude modulation (QAM). The expressions for probability density function, cumulative distribution function, signal-to-noise ratio, and ergodic capacity are derived. The moment generating function (MGF) of fading and the bit error rate (BER) of the OFDM-based M-ary QAM scheme is derived in terms of Meijer's G-function. It has been observed that, in fixed gain relay systems, the modulation scheme's BER is dominated by the SNR of the RF link. While in a variable gain relay system, the turbulence conditions of the FSO system affect the SNR and the BER of the modulation method. The feasibility of heterodyne detection and intensity modulation direct detection (IM/DD) is analyzed in terms of outage probability and ergodic capacity. The results can be used to choose the optimal modulation order and relay system for QAM-OFDM-based optical wireless systems.     

A novel full-wave rectifier/sinusoidal frequency doubler topology based on CFOAs

In this paper, a high-efficiency class-F power amplifier (PA) is designed using integration between a low voltage p-HEMT transistor and a miniaturized microstrip suppressing cell. It results in nth harmonic suppression and high power added efficiency (PAE) under low radio frequency (RF) input powers. The simulation is performed based on harmonic balance analysis. The proposed power amplifier is fabricated, and measurements results validated the simulations. The proposed power amplifier operates at 1.8 GHz with 100 MHz bandwidth and an average PAE of 71.1%, with very low drain voltage of 2 V. At fundamental frequency of 1.8 GHz, the maximum measured PAE is 73.5% at about 12 dBm RF input power. The maximum output power and gain are 23.4 and 17.5 dBm in RF input power ranges of 0–12 dBm, respectively. The fabricated class-F PA with such characteristics can be used for power amplifications in wireless transmitters such as 4G (4th generation)-LTE (long term evolution) communication systems.     

InGaP/GaAs HBT射频功率放大器在片温度补偿电路研究

本文针对无线通信应用的InGaP/GaAs HBT射频功率放大器,提出一种新型的在片温度补偿电路。该温度补偿电路由一个GaAs HBT和五个阻值大小不同的电阻组成,结构简单,可实现性强。通过调整偏置电路中参考电压的方法调节功率放大器静态偏置电流,有效地实现补偿功率放大器功率增益和输出功率随温度变化的特性,优化了射频功率放大器的热特性,性能随温度只有略微的退化。将该温度补偿电路置入一个无线通信应用的三级单片集成功率放大器,温度在-20℃到＋80℃范围内变化时,增益随温度变化的变化量从4.3dB提高到只有1.1dB。     

软切换链路下的混合编码与副载波调制方案

为了提高自由空间光/射频（FSO/RF）混合通信链路的性能，采用混合低密度奇偶校验（LDPC）编码与副载波相移键控/正交振幅调制（PSK/QAM）联合调制的方法，对不同传输比例下混合系统的误比特率性能进行了仿真分析，取得了不同信道条件下单链路和混合链路传输方案的误比特率数据。结果表明，在弱中强湍流条件下采用副载波二进制相移键控（BPSK）调制，相比开关键控（OOK）调制可获得大约4.4dB~5.2dB的增益。采用软切换的混合LDPC编码与副载波BPSK/16QAM调制方案，依据链路状态调整比例为1:1和3:1时，不同湍流强度下可获得大约0.3dB~7.4dB的性能增益。这一研究结果对于提高FSO/RF混合通信系统的全天候高效可靠传输性能具有重要的参考价值。     

Performance Characterization of Spatial Diversity Based Optical Wireless Communication over Atmospheric Turbulence Channels

Optical wireless communication is regarded as the next-generation high-speed technology. It has demonstrated its capability to deliver data faster than any other state-of-the-art wireless communication technique. This technology has drawn attention as a means of implementing reliable high capacity outdoor systems that cannot be implemented by conventional fiber optics. It has emerged recently as an efficient solution to match the larger bandwidth and high data rates requirement of the upcoming wireless communication systems. However, although FSO (free space optics) system has many appealing features, it has rather disappointing performance for long links due to the degrading effects of atmospheric turbulence-induced fading. In the presence of such type of performance impairments, the received signal exhibits random intensity fluctuations, which increase the BER (bit error-rate), where the severe weather conditions can have a detrimental impact on the performance, which may result in an inadequate availability. The MIMO wireless optical procedure, in which the spatial dimensions are used to improve the reliability and spectral efficiency of point-to-point links, provides a promising approach to mitigate turbulence effects due to its powerful performance enhancing capabilities.In this paper, we investigate a terrestrial atmospheric FSO communication system operating under the influence of strong atmospheric turbulences. Additionally, the MIMO technique with equal gain combining (EGC) is used in this work to enhance the data rate of the proposed system. Atmospheric turbulence impacts are modeled as a lognormal channel with due regard for geometric losses. With the use of NRZ line coding, an FSO highly sensitive receiver using either avalanche photodetector (APD) or PIN is designed and simulated for best system performance. The preference is achieved by using Bessel and Gaussian filters. It has been found that APD receiver using Gaussian filter is suitable for long-range links with APD gain value of 3. Also, the selection of APD gain is critical to the system performance. In addition, the optimal value of APD gain required for best system performance decreases as the size of the MIMO technique increases. The achievable performance improvements including received power levels, BER and Q-factor are also discussed. The results show that the system with optical amplifier at the transmitter gives an optimum performance. In addition the system performance is enhanced in most weather conditions by using an amplified 2×2 MIMO-FSO system with booster amplifier.     

Linearity improvement of cascode low-noise amplifiers using double DS method with a tuned inductor

We propose a highly linear low-noise amplifier (LNA) using the double derivative superposition method with a tuned inductor. This topology has an auxiliary common gate stage of the cascode amplifier to cancel each third-order intermodulation distortion (IMD3) component and can provide a high third-order input intercept point (IIP3) for the 5.25 GHz frequency band. From the simulation results using the TSMC 0.18 μm RF CMOS process, the IIP3 in the proposed cascode LNAs can be improved by 9 dB, compared with the conventional derivative superposition method. The proposed LNA achieves an IIP3 of + 15 dBm with a gain of 10.5 dB, a noise figure of 2.4 dB, and a power consumption of 6 mA at 1.5 V.     

基于交叉增益调制的全光单边带上变频研究

提出了一种基于交叉增益调制的全光单边带上变频新技术,对射频信号的全光处理具有独特优势,设计了单边带上变频的光载无线通信系统,并进行实验验证,仿真结果表明,在光纤上传输前后的眼图无明显差异,在经过长度超过25 km 的光纤传输后,系统光功率损耗为1．8 dB,系统误码率为10－9。     

CMOS phase-shifting circuits for wireless beamforming transmitters

Two phase-shifting techniques for wireless beamforming transmitter applications are presented. The first performs quadrant selection using phase-offset local oscillators and fine-grain phase-shifting using RF phase shifters; a 5.2 GHz narrowband phase shifter is designed and fabricated in the CMOS subset of a 0.25 μm SiGe BiCMOS process. Using a tunable all-pass filter topology, it achieves a wide phase-shift range with low loss, and minimizes the number of on-chip passive elements. Measurement results show an insertion loss of 2 dB, an IIP3 of 1 dBm, and a total phase-shift range of 240°; power consumption of the core circuitry is 36.3 mW from a 2.5 V supply. The second approach, a phase-shifting up-converter based on Cartesian combining, achieves a 360° phase shift range that is independent of the operating frequency. Fabricated in 0.18 μm CMOS, it achieves 8 dB conversion gain, 4 dBm OP1 dB, 28 dB sideband rejection, and a 360° phase-shift range at 5.2 GHz without the explicit use of RF phase shifters. The power consumption of its core circuitry is 46.5 mW.     

Design of a high gain and highly linear common-gate UWB mixer in K-band

In this paper, in order to design a K-band common-gate Gilbert-cell mixer via a 0.18 μm CMOS technology, the π-Network and post-distortion cancellation (PDC) techniques are implemented simultaneously, resulting in the improvement of gain, bandwidth, noise figure and linearity. Also, a new method for implementing the π-Network, using the parasitic capacitances between RF and LO stage nodes, is proposed which improves the mixer performance and makes the mixer design possible at high frequencies. It is shown that the π-Network enhances the gain and bandwidth by generating complex poles in system frequency response without the need for extra power consumption. The suitable location of these poles, which gives rise to high gain and high bandwidth, is discussed and determined by MATLAB simulation. Results of simulation illustrate 3.36 dB improvement in power conversion gain and 2 dB reduction in noise figure at the same power consumption with LO power of ?1 dBm in comparison with the case when PDC technique is used only. Compared to conventional mixer, it improves the IIP3 by 6 dB. Also, the power consumption of the mixer together with the designed bias circuit is 9.68 mW at 1.8 V.     

Erratum to: Using Improved Product-Coded Modulation Codes to Reduce the Peak-to-Average Power Ratio in Single-Carrier Frequency Division Multiple Access Systems

A new ultra-wideband common gate low noise amplifier (LNA) for 3–6 GHz WLAN and WPAN applications is presented in which a current reused noise canceling structure utilized in the first stage not only provides a suitable noise performance, but also enhances the linearity characteristics of the LNA in a power efficient manner needed by WLAN/WPAN applications. The overall structure of the proposed LNA, consisting of three stages, namely input matching common gate stage with noise canceling, gain stage, and buffer one, is designed, laid out, and analyzed in 0.18 µm RF CMOS process. The LNA has a noise figure of 3.5–3.6 dB, a high and flat power gain of 20.27 ± 0.13 dB, and input and output losses of better than ?11 and ?14 dB, respectively, over the entire frequency band of 3–5 GHz, while these parameters are 3.5 dB, 20.75 ± 0.25 dB, ?15 and ?9 dB for the frequency band of 5–6 GHz, respectively. IIP2 and IIP3 of the proposed topology are equal to 25.9 and ?1.85 dBm, respectively, at 4 GHz frequency. The proposed LNA has 15.3 mW power dissipation from a 1.8 V supply.     

简洁构型与馈电的宽带双极化金属锥阵列天线北大核心CSCD

本文提出了一种宽带双极化金属锥阵列天线。该阵列天线以传统的旋转体天线结构为主体,通过在锥体底部开设四道正交的直通槽,以便在锥状单元内部形成可与地板间构成匹配谐振腔的开放式空腔结构。在阵列中,任意两个相邻的锥状单元之间可形成类似于Vivaldi天线的辐射缝隙结构。馈电采用同轴馈电方式,探针无弯折结构,金属锥体无弯折过孔。每个金属锥状单元独立,可极大简化加工、装配和维护过程。该天线具有两个正交极化,分别由左右和前后相邻单元构成。仿真结果表明,在频率范围为2～8GHz内,阵列大部分有源VSWR小于2,小部分端口有源VSWR小于2.5 (相对带宽为120%)。     

一种无线宽带收发机载波泄漏校准和补偿技术

A carrier leakage calibration and compensation technique based on digital baseband for a wideband wireless communication transceiver is proposed. The digital baseband transmits a calibration signal, samples the signal which passes through the transmitter path and the calibration loop in the RF chip, measures the carrier leakage by analyzing the sampled data and compensates it. Compared with a self-calibration technique in the RF chip, the proposed technique saves area and power consumption for the wireless local area network （WLAN） solution. This technique has been successfully used for 802.1 In system and satisfies the requirement of the standard by achieving over 50 dB carrier leakage suppression.     

A low-power,wide-range variable gain CMOS RF transmitter for 900 MHz wireless communications

This paper presents a low-power, wide-range variable gain RF transmitter for 900 MHz-band wireless communication applications based on a standard 0.18 μm CMOS technology. A very wide-range variable gain and high linearity up-conversion mixer is obtained by using a newly transconductance stage. High linearity at low power dissipation driver amplifier can be obtained by adopting a folded cascode topology with an additional gate-source capacitor. The measured results show conversion gain of 16 dB, dB-linear gain variation of 47 dB with the linearity error less than ±0.5 dB, output P-1 dB of 2 dBm, and OIP3 of 12 dBm while dissipating 4 mA from 1.25 V supply.     

42GHz 波段接收机前端的设计与研制*

伴随着无线通信技术日新月异的发展,人们对宽频带、高速率、大容量通信系统的需求也日益增大.毫米波由于自身具有波长短、传输容量大等优点,日益受到研究人员的广泛关注和青睐.本文针对42GHz频段点对点高速通信应用,设计研制了该频段的毫米波接收机前端.该前端由三级低噪声放大器(LNA)、一级混频器和一个基片集成波导(siw)镜像抑制滤波器构成.射频(RF)信号工作在40.8GHz～ 42.8GHz频段内,中频(IF)固定在3.5GHz.测试结果显示,在工作频段内其变频增益大于15dB,射频输入功率ldB增益压缩点不低于-30dBm,接收机前端的噪声系数(NF)小于6dB.     

A gm-boosted common-gate CMOS low-noise amplifier with high P1dB

A 2.4-GHz transconductance (g_m)—boosted common gate (CG) low-noise amplifier (LNA) with a high 1-dB compression point (P1dB) is proposed. To overcome the constraint of conventional CG LNA for input-mismatching, RF filters consisting of band-stop and high-pass filter are used as a load and inter-stage matching components, respectively. Therefore, the g _m can be freely increased for a high gain and low noise figure (NF) without decreasing input impedance. Moreover, the linearity is also enhanced because band-stop filter load can reduce 2nd harmonics. The fully integrated LNA implemented by 0.18-µm RF CMOS technology delivers an input P1dB of ?1 dBm, a power gain of 14.8 dB and a NF of 3.7 dB. The LNA consumes 8.2 mA at a supply voltage of 1.8 V.     

An on-chip temperature compensation circuit for an InGaP/GaAs HBT RF power amplifier

A new on-chip temperature compensation circuit for a GaAs-based HBT RF amplifier applied to wireless communication is presented.The simple compensation circuit is composed of one GaAs HBT and five resistors with various values,which allow the power amplifier to achieve better thermal characteristics with a little degradation in performance.It effectively compensates for the temperature variation of the gain and the output power of the power amplifier by regulating the base quiescent bias current.The temperature compensation circuit is applied to a 3-stage integrated power amplifier for wireless communication applications,which results in an improvement in the gain variation from 4.0 to 1.1 dB in the temperature range between -20 and +80℃.