Page 10 - Two-chord Interferometry using 3.39 µm He-Ne Laser on a Flux-Coil-Generated FRC

Quadrature Phase Detectors:
Block Diagram of Electronics
Block diagram of the interferometer electronics including 40 MHz local oscillator (LO), bias tees (BT) with Vbias=–0.5V, band-pass filters (BPF), low-pass filters (LPF), attenuator (Attn), low-noise amplifiers (Amp), splitter (Spl), and quadrature phase detectors (QPD). Note that all RF components are enclosed by SS304 non-magnetic shielding box.
The QPD (I.F. Engineering, model QPD-40-TRIA) has a frequency range of 40 MHz ±1% and a phase accuracy of ±1 degree. The optimum input powers of signal (detector) and reference (LO) lines onto the QPD are ~0 dBm and ~10 dBm, respectively, so that the adequate RF components such as an amplifier, an attenuator, and a band-pass filter are used to meet the input-power requirement as well as to obtain the clean signals.
10 HTPD2010, Wildwood, NJ, 5/17/2010 Presenter: Hiroshi Gota Privileged and Confidential