基于2μm的In Ga P/Ga As异质结双极晶体管(HBT)工艺设计了一种可应用于IEEE802.11 b/g/n无线局域网(WLAN)的高线性度射频功率放大器。为了提高射频功率放大器的线性度,采用了负反馈镜像电路提供直流工作点,设计了良好的输入、输出和级间匹配电路来提高射频功率放大器的线性输出功率。流片结果表明,在工作电压为3.3 V时,射频功率放大器的1 d B线性压缩输出功率(P1d B)可达27 d Bm,当误差向量幅度(EVM)为3%时,2.4 GHz64 QAM激励下,输出功率可达19.8 d Bm,满足标准规范要求。
A three-stage power amplifier(PA) for WLAN application in 2.4-2.5 GHz is presented.The proposed PA employs an adaptive bias circuit to adjust the operating point of the PA to improve the linearity of the PA.Two methods to short the 2nd harmonic circuit are compared in the area of efficiency and gain of the PA.The PA is taped out in the process of 2 μm InGaP/GaAs HBT and is tested by the evaluation board.The measured results show that 31.5 dB power gain and 29.3 dBm P_(1dB) with an associated 40.4% power added efficiency(PAE) under the single tone stimulus.Up to 26.5 dBm output power can be achieved with an error vector magnitude(EVM) of lower than 3% under the 64 QAM/OFDM WLAN stimulus.
Increasingly,mobile communications standards require high power efficiency and low currents in the low power mode.This paper proposes a fully-integrated multi-mode and multi-band power amplifier module(PAM)to meet these requirements.A dual-path PAM is designed for high-power mode(HPM),medium-power mode(MPM),and low-power mode(LPM) operations without any series switches for different mode selection.Good performance and significant current saving can be achieved by using an optimized load impedance design for each power mode.The PAM is tapeout with the In Ga P/Ga As heterojunction bipolar transistor(HBT) process and the0.18-m complementary metal-oxide semiconductor(CMOS) process.The test results show that the PAM achieves a very low quiescent current of 3 m A in LPM.Meanwhile,across the 1.7–2.0 GHz frequency,the PAM performs well.In HPM,the output power is 28 d Bm with at least 39.4% PAE and –40 d Bc adjacent channel leakage ratio1(ACLR1).In MPM,the output power is 17 d Bm,with at least 21.3% PAE and –43 d Bc ACLR1.In LPM,the output power is 8 d Bm,with at least 18.2% PAE and40 d Bc ACLR1.
由于高速移动,车车、车路通信信道存在较大多普勒频移,同时接收信号到达角不符合均匀分布。针对该特点,采用了两种方法进行信道建模,一种是采用R.von Mises提出的概率密度谱函数对多径散射信号到达移动接收机的角度进行建模,另一种是通过研究接收机和发送机之间相对运动进行建模。采用自回归模型法,根据不同的到达角平均方向、发射机和接收机速度比率和到达角宽,建立了不同的车车信道。仿真结果表明所建立的信道理论值与仿真值基本一致,同时揭示了3个参数对车车、车路信道模型二阶特性的影响。为了进一步验证不同信道模型对车车、车路通信的影响,搭建了下一代智能交通通信协议IEEE 802.11p系统测试平台,结果表明在最大多普勒频移为790 Hz、信噪比为5 d B时,简单二维各向异性散射信道比AKKI信道的系统误比特率低17.17 d B,三种信道的误比特率随着移动速度、调制阶数的提高而提高。仿真结果为研究智能交通系统稳定通信建立了基础。
