|dc.description.abstract||With the increase in demand for higher data rates and higher bandwidth requirements, modern communication systems pursue innovative solutions that effectively utilize the high-frequency spectrum available at the Millimeter-wave (mm-wave) band and beyond (Terahertz bands). Phased arrays have found wide applications in satellite communication systems, especially with the decrease in implementation costs.
Phased array systems, operating at K-/ Ka- bands, are considered the pillars of future communication systems. The advances in highly integrated circuits (ICs) allowed the full integration of transmitting and receiving channels in one chip. Thus, increased functionality in a small footprint can be achieved. However, phased array antennas are implemented by placing antenna platforms of each operating band next to each other. Therefore, the antenna platforms are space-consuming. Multiple radiators can utilize the same physical area, owing to the shared-aperture concept. However, fulfilling the performance requirement for radiators of each frequency band is a challenge. Limited work from the literature has been reported on shared aperture arrays operating in the mm-wave range with a small frequency ratio and with acceptable performance at both bands.
In this dissertation, the design, and verification of a novel shared aperture array is implemented using the dielectric resonator antennas (DRAs). With DRAs, the numerous flexible design aspects provide an advantage to meet the stringent requirement of shared-aperture arrays. Further, DRAs as non-metallic radiators are considered a good candidate for mm-wave applications due to their negligible ohmic loss. The 3D-printed technology is used in the realization of the DRAs. 3D-printing provides the advantage of design flexibility and dimensional accuracy as compared to machining methods. All the DRA designs are also fabricated using commercial machined substrates as a benchmark in comparison to the 3D-printed models. Up to the author's knowledge, this work is the first to compare the operation of 3D-printed DRAs with their counterparts. The presented shared-aperture array provides a low-cost solution for mm-wave applications. By properly designing the DRAs, the proposed technique can be further extended to modular form. An analysis of the effect of the orientation of the DRAs in the lattice of the multi-band structure on the antenna characteristics and the isolation between both bands is described.
Firstly, a single-DRA fed by substrate integrated coaxial line (SICL) at K-band is proposed to reduce the DRA feed circuit footprint. The design realizes a wide bandwidth of 3 GHz (19.95 - 23.04 GHz), 3 GHz (20.6 - 23.5 GHz) for the machined DRA, and 3D-printed DRA, respectively. The corresponding measured realized gains are 6.2 dBi, and 6 dBi for the machined DRA, and 3D-printed DRA, respectively. The measured co-polarization to the cross-polarization level is more than 30 dB for both DRAs.
Secondly, the design of a single-DRA fed by substrate integrated waveguide (SIW) at Ka-band on two substrate layers is described. The design realizes a wide bandwidth of 2.2 GHz (30.5 - 32.7 GHz), and 2.3 GHz (30.7- 33 GHz) for the machined DRA, and 3D-printed DRA, respectively. The corresponding measured realized gains are 5.5, and 5.3 dBi, respectively. The measured co-polarization to the cross-polarization level is more than 30 dB for both DRAs.
Thirdly, a K-/Ka- bands DRAs shared aperture sub-array is introduced using the adopted feeding techniques. The sub-array realizes isolation of more than 50 dB between both bands, wide bandwidth of operation of more than 2 GHz, and efficient utilization of aperture space. At the K- band, the machined and 3D printed DRA in the shared aperture configuration covers a broad -10-dB bandwidth of 5 GHz (19.5 to 24.5 GHz) and 5.5 GHz (21 to 26.5 GHz), respectively. At the Ka-band, the machined and 3D-printed DRA sub-array in the shared-aperture configuration covers a bandwidth of 2.4 GHz (30.7 to 33.4 GHz) and 2.3 GHz (31 to 33.3 GHz), respectively. The average realized gain is 9.25, 10 dBi for the Ka-band machined and 3D printed sub-array, and 6.3, 7 dBi for the K-band machined and 3D-printed DRA in a shared sub-array configuration. The measured co-polarization to cross-polarization level is more than 30 dB for the Ka-band machined and 3D printed sub-array. For the K-band, the measured co-polarization to cross-polarization level is more than 26 dB, and 17 dB for the 3D printed and machined antenna in the shared array configuration.
Compared to other reported shared aperture arrays, the suggested sub-array achieved one of the state-of-art isolation and excellent radiation characteristics over a wide operating bandwidth. Moreover, the shared feeding space is efficiently utilized; by sharing the SIW walls with the SICL feeding lines. Furthermore, the PCB technology and 3D-printing allow full integration with planar circuits and efficient operation at mm-wave ranges compared to other reported fully metallic and bulky structures.||en