An array of stagger‐tuned printed dipoles as a broadband frequency selective surface

In addition, a connection metal line of 1 mm width was printed between the two side-feeds. This connection metal line mainly serves as a delay line in the proposed antenna to provide a 90° phase difference between the two side-feeds. This desired phase difference can be obtained by adjusting the distance (1.5 mm in this study) between the connection metal line and the ground conducting patch in the proposed design. Also notice that two small notches were cut near points A and B in the ground conducting patch to avoid the shortcircuiting of the two side-feeds to the ground. To excite the proposed antenna with right-hand CP operation for GPS operation, a 50 microstrip feed line printed on the test circuit board is connected to the side-feed at point A. In this case, the side-feed at point A will have a 90° phase lead, as compared to the side-feed at point B. This condition can lead to successful excitation of two orthogonal resonant modes of equal amplitudes and 90° phase difference for right-hand CP operation. Also note that, if left-hand CP operation is desired for some other applications, the microstrip feed line can be connected to the side-feed at point B. In this case, the side-feed at point A will have a 90° phase lag, as compared to the side-feed at point B, thereby making possible the generation of a left-hand circularly polarized wave. 3. EXPERIMENTAL RESULTS AND DISCUSSION A prototype with the design dimensions shown in Figure 1 was constructed and studied. Figure 2 shows the measured return loss of the constructed prototype. An impedance bandwidth, determined by 10 dB return loss, of 12 MHz (1570 –1582 MHz) centered at about 1575 MHz is obtained. In addition, there are two resonances excited at very close frequencies, which are contributed from the excitation of the two side-feeds in the proposed design. Figure 3 shows the measured axial ratio in the broadside direction of the constructed prototype. A 3 dB axial-ratio CP bandwidth of about 3.5 MHz is obtained, which covers the required bandwidths for GPS operation at 1575 MHz. The measured radiation patterns in two principal planes at 1575 MHz are also plotted in Figure 4, and the measured antenna gain is shown in Figure 5. From the obtained results, good right-hand circularly polarized (RHCP) radiation is seen, and the measured antenna gain is about 3.0 –3.4 dBi for operating frequencies across the 3 dB axial-ratio CP bandwidth. 4. CONCLUSIONS A novel surface-mountable ceramic chip antenna for CP operation has been proposed, and a prototype for GPS operation at 1575 MHz has been implemented and studied. With the use of a squaredisk ceramic chip having a relative permittivity of 45, the constructed prototype occupies a compact volume of 4 17.5 17.5 mm 3 and demonstrates good CP radiation characteristics.