Design and Analysis of $D$ -Band On-Chip Modulator and Signal Source Based on Split-Ring Resonator

In an effort toward high-speed and low-power I/O data link in the future exascale data server, this paper presents a signal source and a modulator in the $D$ -band. The split-ring resonator (SRR) structures are used to boost both the signal power and the extinction ratio (ER). The modulator manifests itself as a compact SRR whose magnetic resonance frequency can be modulated by high-speed data. Such a magnetic metamaterial achieves a significant reduction of radiation loss with high ER by stacking two auxiliary SRR unit cells with interleaved placement. The high-Q tank for oscillation is realized by a stacked SRR decorated with slow-wave transmission line (T-line) for electric field confinement. A four-way power-combined fundamental 80-GHz coupled-oscillator network is magnetically synchronized by the slow-wave T-line, which is frequency doubled to 160 GHz. Fabricated in the 65-nm CMOS process, the measured results show that: 1) the modulator achieves 3-dB insertion loss at the on-state with 43-dB isolation at the off-state, leading to a 40-dB ER at 125 GHz within an area of only $40\,\,\mu \text {m} \times 67\,\,\mu \text{m}$ and 2) the signal source achieves 6.3% frequency tuning range (FTR) with 3.7-mW peak output power at 160 GHz within 0.053-mm ² active area. It has a measured phase noise of −105 dBc/Hz at 10-MHz offset, 5.5% dc-to-RF power efficiency, 70.1-mW/mm ² power density, FOM of −171 dBc/Hz, and FOM $_{T}$ of −172.7 dBc/Hz.