Tri-Band Inter-Frequency Group Delay Calibration

Triple Frequency Reference Station (TFRS) is developing circuitry and associated firmware to produce a phase-coherent signal across the L1, L2, and L5 frequency bands for calibration of triple-frequency, high-accuracy GPS receivers. As an undergraduate project, TFRS aims to assist in the calibration of ionospheric biases by enabling on-demand calibration of receivers as environmental or external factors change. The signal is generated by a Complex Programmable Logic Device (CPLD) and upconverted by three-stages of mixers, placing phase-coherent, GNSS-like signals onto L1, L2, and L5. Modifications to the GRID software defined receiver will measure inter-channel biases of the generated signal when processed by a front-end. TFRS hopes to attain a phase-coherence of 100 picoseconds or less and confirm this accuracy with a series of tests culminating in inter-channel bias measurements.