tailieunhanh - Microstrip Antennas Part 17

Tham khảo tài liệu 'microstrip antennas part 17', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Microwave Properties of Dielectric Materials 469 Half cylindrical pellet In order to study the effect of the half cylindrical pellet towards the frequency response of the filter the cylindrical pellet is replaced with a split pellet from the same batch of samples. The thickness for this pellet is sanded to the same measurements as the previous sample. Furthermore the dielectric properties are also re-measured to make sure that it is consistent and similar to the previous pellet sample. Thus this will give a good representation of the variation of shape in a test to determine the effect of various shapes of dielectrics towards the microwave properties of the electrical model or structure. Dielectric material orientation will be similar to the previous DRA structure and the test setup for this is also shown in Figure 19. Fig. 19. DRF Measurement Half Cylindrical Pellet . Fig. 20. Measured Frequency Response Half Cylindrical Pellet . 470 Microstrip Antennas The measured S 1 2 frequency response for the half cylindrical pellet is shown in Figure 20. As observed the bandstop response curve has shifted to . The return loss is measured at a lower compared to the previous DRF utilizing the full cylindrical dielectric pellet. From this test it is observed that the half cylindrical dielectric material shape increases the stop frequency by almost 1GHz and lowered the stopband attenuation by 20dB. Although the network analyzer that was used for the measurements was limited to a maximum sweep frequency of 3GHz it can be observed from the S 1 2 plot that the bandwidth of the filter remains consistent for both dielectric shapes. Thus it can be deduced from this that splitting the dielectric material in half on the filter generally increases the notch filter center frequency by 50 and also lowers the attenuation at the center frequency also by 50 . 3. Conclusion Results from the dielectric measurements suggest that by using 2 different synthesis techniques .