| At present, the short range wireless communication is important increasingly, so it is significant to research antenna technology in short range wireless communication. The main standard of shot range wireless communication include: Blue tooth, 802.11, IrDA, UWB and Zigbee. The UWB technique is studied by many scientists because of its advantages such as high speed, high capacity, high resolution, anti-multipath fading, low power, simple system structure, low cost and is easy to digitize. Moreover, with sharp increase of communications traffic, dual-frequency antenna is researched by many scholars recently. It is very significant to research dual-frequency antenna operating at 2.4GHz and 5.8GHz bands for WLAN operating at this bands. The UWB antenna and dual-frequency antenna are mainly researched in thesis.In chapter 3, three novel UWB antennas with CPW-fed are proposed.The first one is novel UWB antenna with partial-circular patch, which is design and realized on the substrate with thickness of 0.8mm and relative permittivity of 3.4. The size of antenna is 800mm×800mm, operating at 110MHz-880MHz with 155.56% relative bandwidth for return loss less than -10dB. The normalized radiation patterns at 246MHz,500MHz and 740MHz are presented, it is seen that the proposed antenna has same polarization planes and similar broadside radiation patterns. Especially the H-plane shows good omni-directional radiation patterns. The gain can keep more than OdBi at 110MHz-620MHz, and even 5.4dBi in some frequency range.The second one is UWB antenna with two arc side rectangular patch, which is design and realized on the substrate of RO4003C with thickness of 0.813mm and relative permittivity of 3.38. The size of antenna is 50mm×50mm, operating at 3GHz-20GHz with 148% relative bandwidth for return loss less than -10dB. The simulated and measured normalized radiation patterns at 3.5GHz,10GHz and 16GHz are presented, it is seen that the proposed antenna has same polarization planes and similar broadside radiation patterns. Especially the H-plane shows good omni-directional radiation patterns. The measured gain can keep more than -5dBi at 3.1-20GHz, and even 6dBi in some frequency range.The third one is UWB antenna with two half circular sides rectangular patch, which is design and realized on the substrate of RO4003C with thickness of 0.813mm and relative permittivity of 3.38. The size of antenna is 30mm×30mm, operating at 4GHz-20GHz with 133% relative bandwidth for return loss less than -10dB. The simulated and measured normalized radiation patterns at 6GHz and 15GHz are presented, it is seen that the proposed antenna has same polarization planes and similar broadside radiation patterns. Especially the H-plane shows good omni-directional radiation patterns. The gain can keep more than OdBi at 2.9GHz-15.3GHz, and even 5dBi in some frequency range, which are flatness in operating range, so signal can be radiated and received effectively.In chapter 4, two novel compact dual-frequency antennas operating at 2.4GHz and 5.8GHz are proposed, good and similar radiation characteristic are obtained at two bands.The first one is rectangular dual-frequency antenna with CPW-fed and stub, which is design and realized on the substrate of FR4 with thickness of 1.6mm and relative permittivity of 4.4. The size of antenna is 40mm×40mm, operating at 2.15GHz-2.5GHz and 4.6GHz-7GHz with relative bandwidth are 15% and 41.4% for return loss less than -lOdB. The normalized radiation patterns at 2.4GHz and 5.8GHz are presented, H-plane shows good omni-directional radiation patterns. The gain can keep more than OdBi at 2GHz-8GHz, and even 7dBi in some frequency range. The surface current distribution of patch is changed because of the stub, so the operating frequency is decreased, the bandwidth is broadened, the return loss in operating range is decreased.The second one is novel compact dual-frequency micro-strip antenna, which is design and realized on the substrate of FR4 with thickness of 1.6mm and relative permittivity of 4.4. The compact structure and dual-frequency characteristic are realized respectively using meander technology and double resonance model. The size of antenna is 20mm x 20mm, operating at 2.364GHz-2.401GHz and 5.651GHz-5.878GHz with relative bandwidth are 1.38% and 3.94% for return loss less than -10dB. The normalized radiation patterns at 2.4GHz and 5.8GHz are presented, H-plane shows good omni-directional radiation patterns. The gain can keep more than -4dBi at two bands, which are obviously higher than closed bands and the maximal gain is 2.5dBi.The commercial electromagnetic simulation software Ensemble 8.0 is used to simulate the antenna. The Agilent N5230A vector network analyzer and Lab-Volt 8092 antenna measurement system was used to measure the return loss and radiation pattern. |
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