| MS Seminar

Name of the Speaker: Mr. SNIGDHA JAKKOJU (EE20S039)
Guide: Dr. Saurabh Saxena
Online meeting link: https://meet.google.com/ega-qkfi-hmk
Date/Time: 12th August 2025 (Tuesday), 11:00 AM
Title: A 2.25GHz PLL with 0.1-2MHz Inloop phase modulation for Telemetry Applications.

Abstract :

A compact phase modulator for telemetry applications faces the strict challenge of size, weight, and power consumption, as every such factor adds to the payload and complexity of a successful operation. A single IC solution addresses the above issues but at the cost of the desired linearity of modulation and lesser flexibility in making the changes after the fabrication. A conventional fractional-N phase-locked loop (PLL) offers a compact inloop phase modulation opportunity, but the modulation bandwidth is lower than the PLL loop bandwidth. A stable, low-jitter, low-frequency reference clock source lowers the PLL loop bandwidth, reducing the phase modulation bandwidth. In addition, a low reference frequency spur requirement demands a lower bandwidth. On top of this, a significant phase modulation amplitude stresses the PLL blocks for their linearity requirements. Amid these challenges, this work implements an inloop single IC phase modulator for the telemetry requirements.

A 2.25 GHz fractional-N PLL with 40MHz reference clock and two-point inloop phase modulation is implemented in UMC 180 nm CMOS process. In post-layout simulations with extracted parasitics, the PLL achieves < 1 psrms integrated jitter and <-70 dBc reference spur at the output while consuming 39.5mW from 1.8V supply voltage. An inloop phase modulation bandwidth is extended > 2MHz with small modulating amplitudes, whereas the loop bandwidth of the PLL is restricted to 200 kHz. An output phase modulation with modulation index m≈ 2 and modulation error Δm ≤ 0.1 across 0.1-2.0 MHz frequency range is realized. In addition, the proposed phase modulation technique has been demonstrated at the prototype level using off-the-shelf components and custom-designed PCB.