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Microstrip Antenna Designs for Sensor and Communications Applications David Pozar

Microstrip Antenna Designs for Sensor and Communications Applications David Pozar Electrical and Computer Engineering University of Massachusetts at Amherst Amherst MA 01003. Near field focused microstrip array Ku band fan beam microstrip array Improved bandwidth microstrip reflectarray.

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Microstrip Antenna Designs for Sensor and Communications Applications David Pozar

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  1. Microstrip Antenna Designs for Sensor and Communications Applications David Pozar Electrical and Computer Engineering University of Massachusetts at Amherst Amherst MA 01003

  2. Near field focused microstrip array Ku band fan beam microstrip array Improved bandwidth microstrip reflectarray Outline One of the main goals of the Center for Advanced Sensor and Communications Antennas at the University of Massachusetts is to identify and develop antenna technologies with improved performance and/or reduced cost for future applications.

  3. Near Field Focused Microstrip Array • Application to low-cost radiometric temperature sensor • Food industry, chemical processing, materials manufacturing • Radiometric technique works through smoke, dust, or steam • Developed by ProSensing Inc (Amherst), and K. Stephan (Texas State U) • 12.5 GHz, focus to a spot size of 2.6” at 12” from aperture • Two array versions were designed, fabricated, and tested • Near field testing done at Hanscom AFB • Resulting antenna is substantially smaller and cheaper than original horn

  4. Radiometric Temperature Sensor Antennas – Before and After Original dielectric loaded horn antenna Near field focused microstrip arrays

  5. Calculated Near Field Contours of Microstrip Array

  6. Near Field Measurement of Microstrip Array at Hanscom AFB

  7. Measured Near Field 3D Pattern of Microstrip Array

  8. Measured Near Field E-plane Patterns of Microstrip Arrays f = 12.45 GHz. Red curve for array using non-symmetric feed network, green curve for array with reversed patches in E-plane. Note: main beam peaks are off center due to mechanical misalignment of test fixture.

  9. Ku Band Fan Beam Microstrip Array • Application to short range ocean surface topography mapping • Two arrays used for differential phase shift measurement of backscatter • 45” long aperture at 16.15 GHz, 2 degree beamwidth • 20 dB sidelobe level • Short pulse duration requires time delay feeding across aperture • Loss and space considerations require subarraying (2x4 and 2x6) • Design completed, subarrays tested, final array being fabricated

  10. Ku Band Array 176 patch elements, 2x4 and 2x6 subarrays

  11. Improved Bandwidth Microstrip Reflectarray • Microstrip reflectarray uses a flat aperture of microstrip patches with individual phase shifts to form a coherent beam • Reflectarrays typically use variable-length patches, patches with tuning stubs, or CP patches with rotations to achieve required reflection phases • Bandwidth (gain) is generally limited to 2-4% with these methods • A new technique using aperture coupled patches with stub tuners provides much better bandwidth properties, see “Microstrip Reflectarrays: Myths and Realities”, JINA 2004, at http://www.ecs.umass.edu/ece/pozar/jina.ppt for more discussion of microstrip reflectarrays

  12. Microstrip Reflectarray This reflectarray uses variable length microstrip patches to provide a shaped beam pattern.

  13. Aperture Coupled Stub Tuned Microstrip Reflectarray microstrip patches ground plane with apertures variable length tuning stubs unit cell cross section Patches and apertures are identical for all elements; stubs vary in length to control reflection phase.

  14. Reflection Phase vs. Patch / Stub Length variable-length microstrip patches stub-tuned aperture coupled patches

  15. Comparison of Gain Bandwidth 1 dB gain bandwidth is improved from 3.5% to 9%

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