Compact and Low-profile Frequency Agile Loop Antenna Integrated with Inductors

We present a frequency agile loop antenna which consists of a suspended transmission line and two inductors. Using appropriate inductors, the operating frequency of the antenna can be controlled without seriously sacrificing its performance. We derived an equivalent circuit of this proposed compact and low-profile antenna. Results from some prototypes showed that a frequency tuning range as high as 870 MHz can be achieved using off-the shelf inductors. In the case of integrating two inductors of 33 nH, an electrical size of the antenna as small as 0.118 lambda times 0.013 lambda times 0.047 lambda is achieved.