A new direct-digital quadrature amplitude modulation (QAM) modulator is presented in this paper, which can be reconfigured between 4-QAM, 16-QAM and higher modulation formats. Based on current vector sum, this paper first employs two high-speed Operational Transconductance Amplifiers (OTAs) to generate a set of quadrature basis current vectors whose amplitudes are tunable. A pair of vectors is selected by the switch network to be added in current domain, which reduces the nonlinearity.The chip was fabricated in 0.13 μm CMOS technology.The measured data throughput at 5.4GHz carrier frequency is 16Mbps. Experimental results show that the error vector magnitude (EVM) is 6.20% in the 16-QAM modulation state.The chip core occupies an area of 0.09mm2. The circuit consumes 20mA of dc current from a 1.2V supply.%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.
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