high dielectric constant

anyone please explain what relationship and effect to the antenna performance if we use high dielectric constant? i also want to know what relationship if dielectric constant is high what happened to efficiency and the gain for antenna performance?


regards,
kyg

Hi, kyg:

Higher Er (permittivity) confines the field more into the dielectrics. It will make it harder to radiate. It may also create more surface waves and it will cause lower efficiency and gain. The bandwidth is normally smaller. Regards. From the point view of radiation and bandwidth, it is better to let the field of an antenna spreaded into bigger region. That is why you would see most microstrip antennas use low Er.

Best regards,

how about relationship with the freq that used for example used for uhf band or
wlan or something else?

Frequency is dependent upon the size of the antenna. With higher Er, you are able to reduce the size for the same frequency.

hai jian,

if I use higher Er for uhf freq so it is true the theoretically the size of the
antenna more bigger, the bandwidth is smaller so that efficiency and the gain
become lower?

what do u mean by create more surface wave?

thanks

hi, kyg:

I answered your questions and it does not appear. Here it is again.

1. Higher Er will decrease the size of antenna for the same frequency.
2. Surface wave is created whenever you use layere substrates. It travels along the surface of the substrates. It may be absorbed by the substrates if your substrates are large eough. If it is not large enough, some of it will be radiated as space wave when it hits the boudnary.

Regards,

Pay attention to the loss tangent of the materials you are comparing.