Tham khảo tài liệu 'microstrip antennas part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Circularly Polarized Slotted Slit-Microstrip Patch Antennas 349 the measurement of the reading range. The maximum reading range of 60 - 65 cm is achieved at the boresight. Fig. 5. Measured radiation patterns at 924 MHz. Symmetric-slit with slot based compact CP microstrip antennas In this section the symmetric-slit microstrip patch based compact circularly polarized microstrip antennas are also designed at frequency around GHz. The slit-slotted microstrip patch radiators are printed on the RO4003C substrate H mm sr and tanỉ . The square patch L and ground-plane sizes are mm and mm X mm respectively. The coaxial feed-location yo is mm from centre of the patch radiator. Designed dimensions of the patch radiators are shown in patch sketches. The V-shaped symmetric-slit along with circular slot at the centre of square patch radiator is shown in Figure 6. The circularly polarized radiation is achieved by changing the area of slits along the diagonal directions Al A2 . Simulated resonance frequency of the square patch without slits and slot is around GHz. The measured and simulated return loss is Fig. 6. Symmetric-slit with circular-slot patch radiator. 350 Microstrip Antennas Fig. 7. a . Simulated and measured return loss of the symmetric-slit patch with circular slot. Fig. 7. b . Simulated and measured axial-ratio at the boresight Fig. 8. Measured radiation patterns in x-z and y-z planes at GHz Circularly Polarized Slotted Slit-Microstrip Patch Antennas 351 plotted in Figure 7 a . Measured resonance frequency of the proposed slit-slotted microstrip patch antenna is GHz. Boresight minimum axial-ratio is around the GHz as shown in Figure 7 b . Simulated and measured results are good agreement. The boresight measured gain is more than dBic over the 3-dB AR bandwidth. Measured radiation patterns in x-z and y-z planes at GHz are plotted in Figure 8. Operating frequency of the antenna is lower when .
