2.1.3 Experimental results and discussion

The proposed antenna designs were fabricated by using milling machine technology with 0.1 mm accuracy on Rogers 6035HTC substrate with a 0.25 dielectric thickness and 0.017-mm copper thickness. A 1.85-mm end launcher connector is used to measure the proposed antennas. The simulation reflection coefficient was verified by comparison with the experimental results of the antennas by using 37397C Anritsu vector network analyzer. Photos of the fabricated antennas are shown in Figures 6 and 7. The comparison between measured and simulated |S11| for linearly and circularly proposed antennas are shown in Figure 8(i) and (ii), respectively. The measurement and simulation result data are in a good agreement. Measured results ended at 65 GHz as it is the end-point of the network analyzer. The rectangular slot shape gives the best antenna performance for linearly and circularly polarized slots. These designs also have low profile, wide impedance bandwidth |S11| < 10 dB, and wide 3 dB axial ratio.

3. UWB antenna in radio frequency range

Photo of fabricated circular polarized slot antenna, (a) rectangular, (b) circular, and

Passive Components for Ultra-Wide Band (UWB) Applications

DOI: http://dx.doi.org/10.5772/intechopen.88444

Figure 7.

Figure 8.

107

(c) triangular shaped [27].

Planar microwave circuitry has generated attractive radiating structures with high gain, low weight, reliability, ease of manufacturing and integration such as the Vivaldi antennas [36, 37], and the tapered slot antenna [38] for UWB antennas. The printed planar log-periodic dipole (LPDA) is the most suitable solution microwave frequencies [39]. LPDAs have a lot of advantages, such as directive radiation pattern, linear polarization and low cross polarization ratio over a wide frequency range [5]. At the beginning, coaxial cable was used for feeding the printed LPDAs at the radio and the TV frequency bands; however, it was found that the performance became worse when frequency increases. Due to huge increase in data traffic, there is a requirement for wireless networks which support both data and voice transfer

Measured and simulated |S11| of (i) linear polarized (a) rectangular, (b) circular, and (c) triangular slot shaped and (ii) circular polarized (a) rectangular, (b) circular, and (c) triangular slot shaped [27].

simultaneously for short-range wireless communication systems [1, 2].

Figure 6. Photo of fabricated linear polarized slot antenna, (a) rectangular, (b) circular, and (c) triangular shaped [27].

Figure 7.

bandwidth. However, AR bandwidth discontinuities appear from 40 to 55 GHz. The comparison results of AR values simulated and measured at t = 3 mm is shown in Figure 5(b). Finally, for the triangular slot shape, a truncated corner was used. To improve the AR bandwidth, an L-shaped strip was added at the other triangular corner with width 0.1 mm as shown in Figure 3. The bandwidth for simulated and measured AR values for the triangular CP antenna is shown in Figure 5(c). From previous shapes, it appears that rectangular shaped slot with notches gives wide

Axial ratio of the antennas with different slot shapes (a) rectangular, (b) circular, and (c) triangular [27].

The proposed antenna designs were fabricated by using milling machine technology with 0.1 mm accuracy on Rogers 6035HTC substrate with a 0.25 dielectric thickness and 0.017-mm copper thickness. A 1.85-mm end launcher connector is used to measure the proposed antennas. The simulation reflection coefficient was verified by comparison with the experimental results of the antennas by using 37397C Anritsu vector network analyzer. Photos of the fabricated antennas are shown in Figures 6 and 7. The comparison between measured and simulated |S11| for linearly and circularly proposed antennas are shown in Figure 8(i) and (ii), respectively. The measurement and simulation result data are in a good agreement. Measured results ended at 65 GHz as it is the end-point of the network analyzer. The rectangular slot shape gives the best antenna performance for linearly and circularly polarized slots. These designs also have low profile, wide impedance

axial ratio bandwidth without degrading the antenna bandwidth.

2.1.3 Experimental results and discussion

UWB Technology - Circuits and Systems

Figure 5.

Figure 6.

106

(c) triangular shaped [27].

bandwidth |S11| < 10 dB, and wide 3 dB axial ratio.

Photo of fabricated linear polarized slot antenna, (a) rectangular, (b) circular, and

Photo of fabricated circular polarized slot antenna, (a) rectangular, (b) circular, and (c) triangular shaped [27].

Figure 8.

Measured and simulated |S11| of (i) linear polarized (a) rectangular, (b) circular, and (c) triangular slot shaped and (ii) circular polarized (a) rectangular, (b) circular, and (c) triangular slot shaped [27].
