Design of a Light and Compact Antenna Element for Ultrawideband Digital Arrays
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This report contains the design of a tightly coupled dipole array (TCDA) ultrawideband antenna element with an integrated Marchand balun made for digital phased arrays. The element is manufactured and measured as part of an 8x8 array. The project is done in cooperation with the research group for passive RF-sensors at the Norwegian Defence Research Establishment (FFI) who are in the beginning phases of researching UWB technology. In an infinite array simulation, the element performs on par with existing designs made for the same frequency bands. At broadside it achieves a bandwidth of 1:5.35 (2.33-12.46 GHz) for a voltage standing wave ratio (VSWR) of < 2.5 and a radiation efficiency of more than 80 percent. The bandwidth for the same conditions at a scan angle of 70 deg. in the E-plane is 1:4.26 (2.7-11.5) GHz. In the H-plane, the VSWR is slightly higher, and the array achieves a bandwidth of 2.35-12.2 GHz (1:5.2) for a VSWR of < 3 and a radiation efficiency of more than 80 percent at a scan angle of 50 deg. The radiation efficiency at broadside is more than 90 percent for a bandwidth of 2.3-11.8 GHz (1:5.13) which could be important if the antenna is to be used in radio detection and ranging (radar). The manufactured prototype shows promising results, but needs more work in order to function on the same level as the simulated array. It suffers from peaks in the VSWR believed to be caused by ground loops and production inaccuracies. At broadside, the prototype achieves a bandwidth of 2.45-12.95 GHz (1:5.3) for a VSWR of < 4 (< 2.5 if the largest peak in VSWR is ignored). It is likely that the VSWR can be reduced through better production.