A 26 GHz retro-reflective array for long-range RFID applications
A unique design of series-fed grounded coplanar waveguide (GCPW) patch arrays for use in retro-reflective arrays is presented. For the current application, a planar retro-reflector which is capable of providing large radar cross-section (RCS) and signal modulation, and can also operate on metallic surfaces from 25.5–26.5GHz is desired. Linear, series-fed GCPW patch arrays are employed as the radiating elements. Using constituent arrays allows maximization of RCS using the minimum number of active components. Additionally, the unique orientation of the series-fed arrays provides beam squinting, allowing for ease of target identification and distinguishing the response from that of the array ground plane. The array design and results are briefly presented herein. Integration of the array in the intended system application is discussed in a separate conference submission.
Tracking of Metallic Objects Using a Retro-Reflective Array at 26 GHz
The detection and tracking of targets in highly cluttered environments often poses a difficult engineering challenge as the strong clutter backscatter contained in the scene makes it difficult to distinguish the target of interest. A design concept to aide in standoff detection and tracking of large metallic objects in a warehouse setting is presented. This includes the design and implementation of an active retro-reflective array system that is able to determine the precise location and identification of an object. To accomplish this, a unique series fed grounded coplanar waveguide patch antenna is designed and implemented with minimal cross coupling among elements. This compact array has a relatively large radar cross-section (RCS) while maintaining the desired retro-reflectivity. Additionally, a tilted beam is incorporated in the linear series-fed array to isolate the large RCS of the planar array structure at boresight from the desired modulated, retro-reflective RCS. This method for enhanced detection is implemented at 26 GHz. The incorporation of the high-speed PIN switches into the array structure provide the tag with a unique identification. Measurement results for the modulated RCS from such an array in a cluttered environment are presented.
Mutual impedance effects in large beam scanning arrays
An analysis is presented of the driving point impedance of the elements in a flat array of infinite vertical height but finite horizontal width. It is assumed that each of the elements is fed by a separate amplifier, having infinite internal impedance, and that the amplifiers can be phased to direct the beam at various positions in space. The radiating elements considered are infinitely long wires spaced on half-wavelength centers and half-wave dipoles spaced on half-wavelength centers, each backed by a conducting ground plane spaced one-quarter wavelength from the elements. Values of driving point impedance are computed for the 61 elements in arrays 30 wavelengths wide. Values of the driving point impedance near the center of the array are found to agree closely with the values computed for infinitely wide arrays while the driving-point impedance of elements near the edge of the array are found to deviate considerably from the values at the center.