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High efficiency planar and RFIC-based antennas for millimeter-wave communication systems


The dissertation presents the design and measurements of several planar and RFIC-based high efficiency antennas for mm-wave applications. The high-efficiency microstrip-fed endfire angled-dipole antenna is designed mainly for phased-array applications. It is built on both sides of a Teflon substrate ([epsilon]r = 2.2) and allows a wideband feed from the single-ended microstrip line to the differential dipole. The design results in wide radiation patterns for scanning purposes with a gain of around 2.5 dB at 20 - 26 GHz and a cross-polarization level of < -15 dB at 24 GHz. A mutual coupling of < -23 dB is measured between adjacent elements with 6.8 mm center-to center spacing (0.50 - 0.54[lambda]0 at 22 - 24 GHz). A variant of the angled-dipole antenna with a magnetic ground plane edge was also developed, and shows a measured gain of > 6 dB at 23.2 - 24.6 GHz and very low mutual coupling between elements (< -23 dB for a 6.8 mm spacing). Both antennas result in a radiation efficiency of > 93% when referenced to the microstrip line feed. The usefulness of these antennas as phased-array radiators is demonstrated by several eight-element linear arrays at 22 - 24 GHz with scan angle up to 50°. High-efficiency microstrip-fed and CPS-fed Yagi-Uda antennas have also been developed for point-to-point millimeter-wave communication systems. The antennas are built on Teflon substrates ([epsilon]r< = 2.2) ; and utilize 5 directors to result in a gain of 8 - 12 dB at 24 GHz and 60 GHz. A mutual coupling of < -20 dB is measured between two microstrip-fed Yagi-Uda antennas with a center-to center spacing of 8.75 mm (0.7[lambda]0 at 24 GHz), and a two-element array results in a measured gain of 11.5-13.0 dB at 22-25 GHz. The planar Yagi-Uda antennas result in high radiation efficiency (> 90%) and is suitable for short-range mm-wave radars and high data- rate communication systems. A differential version was also developed using a folded dipole feed and is compatible with fully-differential RFICs. Self-shielded microstrip-fed Yagi-Uda antenna has also been developed for 60 GHz communications. The antennas are built on a Teflon substrates ([epsilon]r = 2.2) with a thickness of 10 mils (0.254 mm). A 7-element design results in a gain > 9.5 dB at 58 - 63 GHz. The antenna shows excellent performance in free space and in the presence of metal- planes used for shielding purposes. A parametric study is done with metal plane heights (h) from 2 mm to 11 mm, and the Yagi-Uda antenna results in a gain > 12 dB at 58 - 63 GHz for h = 5 - 8 mm. A 60 GHz four-element switched-beam Yagi-Uda array is also presented with top and bottom shielding planes, and allows for 180° angular coverage with < 3 dB amplitude variations. This antenna is ideal for inclusion in complex platforms, such as laptops, for point-to-point communication systems, either as a single element or a switched-beam system. MM-wave planar monopole antennas have been also demonstrated. A triangular and a straight monopole antennas result in a measured S₁₁ < -10 dB at 20.7 - 37.9 GHz and 18 - 42 GHz respectively. Both antennas are suitable for ultra-wideband applications. These antennas show omni-directional patterns over almost the whole bandwidth but with high cross-polarization levels ( ̃equal to the co-polarization level). An alternate monopole design with a localized folded current choke was developed and results in lower cross-polarization levels ( -6 dB), but with S₁₁ < -10 dB at 23.1 - 26.7 GHz. A variant of this design with a magnetic ground plane results in substantial reduction in the cross-polarization level (-13 dB) but with a bandwidth of only 1 GHz (S₁₁ < - 10 dB at 23.5 - 24.8 GHz). The measured gain of the antennas are in the range of -4.0 dB to + 2.9 dB, depending on the design, and with high radiation efficiency (> 90%). Finally, a W-band high-efficiency, electromagnetically-coupled on-chip silicon microstrip antenna has been demonstrated. The antenna is composed of a quartz substrate placed on top of a commercial low- resistivity SiGe BiCMOS silicon chip. Design criteria for the microstrip antenna taking into account the dielectric and metal-density rules for the different layers of the BiCMOS silicon chip are presented. The antenna results in Sv(1)v(1) < -10 dB at 91.7 - 98.5 GHz, a gain of 0.7 - 3.9 dB and a radiation efficiency of 44 +/- 13% at 91 - 100 GHz. The design is scalable to NxM elements and to wafer-scale arrays. To our knowledge, this is the first high- efficiency Silicon wafer-scale antenna to date

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