Fabrication and performance of broadband back to back waveguide to suspended stripline transition on quartz for D-band

Abstract

Fig. I.Suspended stripline structure.In practical SSL circuits, grooves are used in the housing to support the dielectric substrate. For geometries in which the groove depth is a significant fraction of the channel width (often in the case at millimeter wave frequencies), this omission predicts a much higher cut-off frequency for the TE IO type waveguide mode than actually exist. A full wave simulation is necessary to determine the exact cut-off frequency of the higher order waveguide mode in the presence of strip conductor.The electric probe type transition consists of a rectangular electric probe inserted into the waveguide formed by an extension of the suspended stripline beyond the ground plane. The idea is very similar to the conventional waveguide to coaxial line transition. These types of transitions have been already developed at Kaband and W-band [1]-[4]. This paper describes the fabrication and performance of the above transition for D-band on 2 mil quartz substrate. Although fused quartz is an extremely brittle material, But for realizing millimeter wave circuits at these frequencies, fused quartz substrate is preferred due to its lower loss tangent, extremely good surface finish and tight control of relative permittivity. Proper and careful handling is required for fabrication ofMIC circuits on quartz. II. FABRICATIONBare fused quartz (Er=3.78) of 20 x 20 mm 2 size were cleaned and coated with 2 Jlm gold on one side by electron beam evaporation followed by electroplating.For better sticking of gold, 200 Achromium was coated before gold. Chrome mask were prepared using Laser Pattern Generator DWL66 and subsequent developing and etching. After photolithography process (resist coating, UV exposing, developing and wet etching), MIC circuit on quartz was fabricated. After dicing the Abstract -A back to back waveguide to suspended stripline transition for D-band has been fabricated on 2 mil (50.8 JUIl) fused quartz substrate by photolithography process and the performance of the transition has been studied. The excitation of transition probe has been done by placing the rectangular probe transversely across the WR6 waveguide and using a 50 JUIl fIXed short. To obtain low reflections over the whole operating frequency range of the transition, dimensional parameters, such as probe length, probe width, width and height of suspended stripline channel and thickness of quartz substrate have been optimized using electromagnetic simulation software HFSS. Insertion loss of less than 1.5 dB has been achieved for fabricated back to back transition on quartz over frequency range from 130 to 150 GHz.

Inline waveguide to suspended stripline transition with DC/IF return path

“…The insertion loss is comparable with other reported works. It is a little higher than the one in at D‐band and at G‐band. For , the operation bandwidth is much narrower than the one in this work, and the performance can be optimized at the interested band.…”

Broadband suspended stripline to air‐filled rectangular waveguide transition

“…Various transitions between the SSL and the rectangular waveguide have been reported in the open literature [6][7][8][9][10]. A right-angle transition that couples energy from the SSL to the waveguide by means of a probe [6], employs a capacitive load along the stripline to improve the matching bandwidth.…”