Synthesis of microwave circuit board antennas for economically optimized 902-928 MHZ band applications
A method to design a low cost, small size antenna for operation within the 902-928 MHz frequency band is developed. As an example, a Printed Circuit Board (PCB) topology has been selected using an inexpensive FR-4 grade board material. A single patch antenna cannot be used because the resonant frequency varies due to the process variation of the PCB material. A wider bandwidth, coplanar strip antenna is designed to compensate for the PCB material variation. The Finite Difference Time Domain (FDTD) Method is used to simulate different coplanar strip combinations. A final topology selection is based on impedance bandwidth, average return loss, radiation bandwidth, and relative gain. A three coplanar strip antenna is the selected final design. The impedance bandwidth of this antenna is 46 MHz, approximately twice the impedance bandwidth of a single patch antenna of similar dimensions. The relative gain reduction of the three coplanar strip antenna is only 2 dB with respect to the single patch antenna. Also, the simulated gain variation over the expected permittivity variation is only $\pm$2.6 dB. No significant relative gain reduction is expected over the predicted loss tangent variation.
Mark Roman Wolski,
"Synthesis of microwave circuit board antennas for economically optimized 902-928 MHZ band applications"
(January 1, 1998).
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