Five-Level Waveguide Correlation Unit for

Recent astrophysical measurements require an accu- rate evaluation of the correlation product between very weakly correlated signals. Waveguide correlation units represent a very appealing solution for these applications because of their stability and low-loss features. A new waveguide correlation unit architec- ture is discussed in this paper. It extends over five levels in the -plane and integrates hybrid couplers, filters, a phase shifter, matched loads and various matched transitions. All the aspects concerning the analysis, design, and manufacturing procedures are described, focusing on the reduction of the spurious correlation terms (systematic errors). An aluminum -band prototype has been designed and experimentally tested. The device exhibits spu- rious correlation parameters of the order of 30 dB, in a 10% fre- quency band, in good agreement with the predicted data. Thanks to this feature, the presented architecture is suitable for high-per- formance correlation polarimeters, where very high sensitivity to the relevant signal, as well as very high rejection of both the unpo- larized component of the radiation under test and the instrument noise, are required. Index Terms—Correlation units, directional couplers, filters, hy- brid phase discriminators, phase shifters (PSs), polarimeters, po- larization measurements, radiometers, Stokes parameters, wave- guide components, waveguide networks.

[1]  Ke Wu,et al.  A new 94-GHz six-port collision-avoidance radar sensor , 2004, IEEE Transactions on Microwave Theory and Techniques.

[2]  F. Arndt,et al.  Field Theory Design of Rectangular Waveguide Multiple-Slot Narrow-Wall Couplers , 1986 .

[3]  L. Brunetti,et al.  A 33 GHz polarimeter for observations of the Cosmic Microwave Background , 1998 .

[4]  R. Tascone,et al.  The Sky Polarization Observatory , 2004 .

[5]  R. Tascone,et al.  Orthomode transducer for millimeter-wave correlation receivers , 2006, IEEE Transactions on Microwave Theory and Techniques.

[6]  R. Tascone,et al.  A novel design tool for waveguide polarizers , 2005, IEEE Transactions on Microwave Theory and Techniques.

[7]  R. Orta,et al.  Scattering matrix approach for the design of microwave filters , 2000 .

[8]  J. Uher,et al.  Waveguide Components for Antenna Feed Systems: Theory and CAD , 1993 .

[9]  R. Tascone,et al.  Piecewise-uniform bends in rectangular waveguide , 2005, IEEE Microwave and Wireless Components Letters.

[10]  R. Sorrentino,et al.  Rigorous and efficient fabrication-oriented CAD and optimization of complex waveguide networks , 1997, 1997 IEEE MTT-S International Microwave Symposium Digest.

[11]  R. Tascone,et al.  On-board calibration system for millimeter-wave radiometers based on reference-polarized signal injection , 2006, IEEE Transactions on Microwave Theory and Techniques.

[12]  Tullio Rozzi,et al.  Accurate full-band equivalent circuits of inductive posts in rectangular waveguide , 1992 .

[13]  Enzo Pascale,et al.  The BaR-SPOrt experiment , 2002 .

[14]  Renato G. Bosisio,et al.  Ka-band direct digital receiver , 2002 .

[15]  S. Masi,et al.  The BaR-SPOrt experiment , 2002, SPIE Astronomical Telescopes + Instrumentation.

[16]  T. Itoh.  Numerical techniques for microwave and millimeter-wave passive structures , 1989 .

[17]  Yu Rong,et al.  Full-wave optimum design of millimeter-wave rectangular waveguide narrow-wall branch couplers , 1999, 1999 IEEE MTT-S International Microwave Symposium Digest (Cat. No.99CH36282).

[18]  Ke Wu,et al.  A new six-port junction based on substrate integrated waveguide technology , 2005, IEEE Transactions on Microwave Theory and Techniques.

[19]  G. Engen,et al.  The Six-Port Reflectometer: An Alternative Network Analyzer , 1977, 1977 IEEE MTT-S International Microwave Symposium Digest.

[20]  R. Orta,et al.  Reduced-order optimized mode-matching CAD of microwave waveguide components , 2004, IEEE Transactions on Microwave Theory and Techniques.