archimedean spiral mode MSA

[sahar20]

i am designing two arm archimedean spiral mode MSA using ie3d software.the ie3d version is 11.05. i simulated the compete model. but the anenna & radiation efficiency is too low. also vswr value is 2 for 1.5 to 1.9 ghz range only . suggest the changes in my model to improve efficinct to 80 to 90 % . also suggest the remedies to improve vswr for wide range.the no. of turns in desinn are 2.5 & the spacing between the conductors & width is 0.5 mm. by changing these parametrs or no. of turns can i get the desired & expected results.or by changing the dielectric constant OR loss tangent results will be improved . kindly suggest the remedies

 

[nazanin]

Low efficiency may be related to the thickness of the trace is too small. If the VSWR is not good, it might be that your normalization impedance is 50-ohms. Most wide band antennas may not work at 50-ohms.