A Ka-Band Low-EVM Subharmonically Injection-Locked FLL IQ Modulator Using Stacked-Boosting and Dual-Injection Technique

In this letter, a $Ka$ -band low error-vector-magnitude (EVM) subharmonically injection-locked frequency-locked loop (SILFLL) in-phase and quadrature (IQ) modulator is proposed using 0.18- $\mu \text{m}$ CMOS process. The proposed circuit consists of an SILFLL and four reflection-type modulators. A stacked-boosting technique is employed in the oscillation core to further extend the frequency up to 28 GHz, and a dual-injection technique is employed in the SILFLL to significantly widen the lock range. As the subharmonic number is 3, the measured phase noise at 1-MHz offset and jitter integrated from 1 kHz to 40 MHz are better than −120 dBc/Hz and 95 fs, respectively. Between 26.6 and 28.2 GHz, the proposed SILFLL IQ modulator features an EVM of within 8%, a phase error of 2°, and a magnitude error of 2% for various quadrature amplitude modulations (QAMs), and the modulation can be up to 64-QAM scheme. The work is suitable for a few advanced digital communications due to its high modulation quality.