Analysis of dual slot antennas for quasi-optical applications using lumped element (LE)-FDTD method

Analysis of dual slot antennas is becoming very important for the design of many quasi-optical circuits. This paper uses the lumped element finite difference time domain (LE-FDTD) method to investigate the performance of single and dual slot antennas on both infinite and finite dielectric substrates. The infinite case has been used to validate the approach. The finite dielectric case has been studied to understand the influence of surface wave modes propagating within the finite substrate on the performance of such circuits. A good agreement with published results has been obtained for the infinite case. Results are shown for dual slots on finite substrates suggesting that changes in the feeding configuration can reduce the problem of spurious coupling. This paper also presents results comparing LE-FDTD analysis with measured results. Good agreement is obtained for resonant frequency and reasonable agreement for amplitude. The results show that impedances close 50 Ω can be obtained by feeding at the end of the slot. This allows for the possibility of directly matching active components placed in the slot. The lumped element FDTD code being used allows for the incorporation of transistors and diodes in the slots plane wave excitation and radiation pattern calculation. Thus complete quasi-optical circuit performance can be investigated