An Integrated Millimeter-Wave Broadband Microstrip-to-Waveguide Vertical Transition Suitable for Multilayer Planar Circuits
An integrated broadband vertical microstrip-to-rectangular waveguide (RWG) transition at Ka-band is presented. This transition is especially suitable for multilayer planar circuits, by utilizing a section of multilayer three-dimensional (3-D) stepped substrate integrated waveguide (SIW) structure, along with a taper transition. A simplified initial transition model from 3-D stepped SIW to waveguide is first optimized, thereafter, a full microstrip-to-waveguide transition is constructed and further optimized. For demonstration, some back-to-back transition prototypes are fabricated by multilayer PCB processing. The experimental results show that the return loss better than 15 dB is obtained from 33 to 36.7 GHz, with the minimum net insertion loss about 0.7 dB for a single transition at 35 GHz.
Bandwidth Comparison of Topside Waveguide-to-Microstrip Transitions with Back-Short Waveguide and with Double-Layer Substrate in Millimeter-Wave Band
Topside waveguide-to-microstrip transitions whose waveguide sits on the top of the substrate were developed in the millimeter-wave band. A substrate is attached on a back-short waveguide and the WR-10 waveguide is set on them. The microstrip line is inserted into the WR-10 waveguide, while the microstrip line is inserted into the backshort waveguide of the ordinary transition. A topside waveguide-to-microstrip transition with double layer substrate has been also developed. A coupling patch is located on the top surface with spacing of the upper substrate thickness from the microstrip signal line patterned between the upper and the lower substrates. The performance of the topside transitions with a back-short waveguide is compared with the transition with double layer substrate and the ordinary transition in this paper.
Modeling Coherent Backscattering Errors in Fiber Optic Gyroscopes for Sources of Arbitrary Line Width
We present a new model of the noise and drift induced by coherent backscattering in a fiber optic gyroscope (FOG) interrogated with a light source of arbitrary temporal coherence. This study is critical to understand whether a FOG driven with a laser instead of a broadband source can attain high sensitivity and stability, which would have the overwhelming benefit of improving the FOG scale factor stability by at least ten-fold and would enable the use of FOGs for inertial navigation of aircrafts. Analytical and numerical solutions bring to light two significant new predictions. First, coherent-backscattering noise can be made negligibly small by utilizing a laser with a very narrow linewidth (less than ~ 20 kHz), although in this regime the drift is high. Second, by using a laser with a broad linewidth (greater than ~ 10 MHz), both the noise and the drift are low enough for aircraft inertial navigation. The dependencies of the noise and drift on fiber loss, loop coupling coefficient, and backscattering coefficient are also presented to define the optimum mode of operation of this new class of FOGs.