I have simulated a patch antenna and obtain multiband resonant frequency. I observe that at one band there is a huge gap in total efficiency and radiation efficiency what can be the possible reason? also, I have observed that impedance is near 50 ohms at resonant frequencies.
Sir, My antenna resonates at 28, 38, and 60ghz. but at 38 GHz there is a very huge gap between these two efficiencies. The total efficiency of an antenna is the radiation efficiency multiplied by the impedance mismatch loss of the antenna when connected to a transmission line or receiver (radio or transmitter). but how impedance mismatch is high for one resonant frequency and in Z-plot impedances are near 50 ohms at all the resonating frequencies
Yes, Ghanshyam Singh , has rightly pointed the fact. Both are different. Radiation loss is computed from the radiated power where total loss = rad loss, dielectric loss, conductor loss, surface wave loss etc. Thats why, the curve is correct w.r.t those two losses only.
For more details, James and Hall, hand book of Microstrip Antenna, Vol 1-2, 1989, Chap. 3
Thank you Sudipta Maity sir. It means at 38GHz other losses result in high variation and I have to increase the matching at that frequency. Sir, what can be its possible solution?
Many of the times what happens is that due to parasitic effects we may get resonating frequency. However, at that frequency there will be radiation due to parasitic effects, which are very small when comparing with the direct radiation. The amount of radiation will be very less, which may cause less radiation efficiency. This will majorly happens when we introduce slots, folded strips and etc.
For antenna application, you have to match the feeding system with main antenna element.
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