In this letter, a 38–40 GHz high-speed IQ modulator using sub-harmonically injection-locked quadrature frequency-locked loop (FLL) is proposed. The IQ modulator consists of a quadrature FLL and four reflection-type modulators and it is implemented in a 90-nm complimentary metal–oxide–semiconductor (CMOS) process. With a sub-harmonic number of four, the proposed modulator features a locking range wider than 2 GHz, a maximum data rate of higher than 8 Gbps, and low error vector magnitudes (EVMs), among high-level QAM modulations. The modulation scheme can be up 128 QAM due to the low phase noise and low quadrature error of the FLL. The measured 128-QAM EVM is within 3%. With a data rate of 8 Gbps, the measured 16-QAM EVM is within 6%.

中文翻译：

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38–40 GHz 高速 2ⁿ-使用次谐波注入锁定正交 FLL 的 QAM 调制器

在这封信中，提出了使用次谐波注入锁定正交锁频环 (FLL) 的 38–40 GHz 高速 IQ 调制器。IQ 调制器由一个正交 FLL 和四个反射型调制器组成，采用 90 nm 互补金属氧化物半导体 (CMOS) 工艺实现。所提出的调制器的次谐波数为 4，在高级 QAM 调制中具有比 2 GHz 更宽的锁定范围、高于 8 Gbps 的最大数据速率和低误差矢量幅度 (EVM)。由于 FLL 的低相位噪声和低正交误差，调制方案可以达到 128 QAM。测得的 128-QAM EVM 在 3% 以内。数据速率为 8 Gbps 时，测得的 16-QAM EVM 在 6% 以内。