1. Path Length Difference Study R. Apsimon

2. Assumptions Assume input signals vary sinusoidally (good approximation after BPF). Input signal arrives at a phase +φ for one input and a phase –φ for the other input – This symmetry is required to solve the equations 2φ is the path length difference expressed as a phase at 714MHz

3. After a lot of maths… A and B are the input amplitudes. ψ Δ is the phase difference between the sum and diff channels. Δθ is the phase jitter on the LO.

4. Simplifications Assume A=B – ie. centre beam at ATF2 or equal amplitude on test bench. δy is the contribution to the uncorrelated jitter. C is the calibration constant.