tailieunhanh - Microstrip Antennas Part 15

Tham khảo tài liệu 'microstrip antennas part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Microstrip Antennas for Indoor Wireless Dynamic Environments 409 Fig. 31. Measuring a planar microstrip antenna with Butler matrix inside near field Satimo chamber Fig. 32. Simulated reflection coefficients versus frequency for the planar microstrip antenna array with 4 X 4 Butler matrix using FR4 substrate 410 Microstrip Antennas 3. Analysis design and implementation of an aperture-coupled microstrip antenna The circular polarization diversity with the square patch microstrip antenna is obtained by the implantation of the quadrature hybrid as a microstrip feed line. The small size antenna is achieved by using the aperture coupled structure. In the present study the ACMSA is analyzed based on cavity model because the TLM is useful only for patches of rectangular shape 14 . The cavity model is used to design the ACMSA and determine the length of the open microstrip stub line in order to match microstrip antenna. The Matlab and ADS are used for designing and simulating the ACMSA. Analysis of ACMSA using cavity model Resonant Frequency The cavity model is based on treating the microstrip antennas as cavities formed by microstrip lines as shown in Figure 33. The region between the patch and ground plane may be treated as a cavity bounded by electric walls above and below and magnetic walls along the edges. The fields inside the antenna are assumed to be the fields inside this cavity. Due to the electrically thin substrate the fields in the interior region do not vary with z. Also inside the cavity the electric field has only a z component Ez and the magnetic field has Hx and Hy components 14 . Figure 33 shows the cavity model of the ACMSA. Microsn ip feed-line Fig. 33. Cavity model of the ACMSA The magnetic field H inside the cavity volume can be developed by Maxwell s equations 16 Vx H Je jaS E 13 Microstrip Antennas for Indoor Wireless Dynamic Environments 411 Vx H A A A x y z _d_ _d_ _5_ dx dy dz Hx Hy 0 14 Vx H 15 I d Vx VxH 1 2 I õxõy ổy2 Vx Vx H A A A x