Accurate Millimeter-wave Carrier Frequency Offset Measurement Using the Six-port Interferometric Technique
Résumé
A V-band front-end based on a six-port interferometer is proposed for the accurate measurement of Carrier Frequency Offset (CFO) and carrier recovery in a wireless system. The interferometer uses power readings for amplitude, phase or frequency comparison between its two RF inputs. If the circuit is carefully designed, this low-cost technique allows precise phase and frequency measurements without the need of any calibration. Furthermore, the ability to work with a reduced local oscillator (LO) power is a significant advantage of interferometry versus conventional mixing techniques. Measurements performed at 64 GHz show a resolution of a few Hz, as low as permitted by today's DC coupled measurement equipment. A CFO of 3 Hz, equivalent with a Doppler shift corresponding to a velocity of 7 mm/s, has been successfully measured.