Wireless data distribution system based on dual-polarized dielectric waveguide

The growing number of mobile devices over the past decades, such as mobile phones, IoT sensors, and terminals, has driven exponential growth in the number of nodes in wireless networks. Furthermore, recent advances in network-based activities, such as entertainment and video conferencing, are driving the need for high-bandwidth, low-latency, and high-reliability wireless networks. In this thesis, a data distribution system based on dual-polarized dielectric waveguides is presented. The system targets the frequency range at around 60 GHz, which is of interest to wireless standards such as IEEE 802.11ad. Besides, clip antennas are presented as radiating elements in the data distribution system. Further components, such as metal waveguide dividers and transitions to metal waveguides, are also presented. The presented dielectric waveguide is dual-polarized, with the fundamental mode propagating simultaneously in two polarizations as two data channels. The coupling between the two polarizations, the cross-polarization coupling, reduces the transmission quality of the data channels. The cross-polarization coupling is deeply investigated in this thesis, first by investigating a rectangular metal waveguide, and then the theory is applied to the dielectric waveguide. The key parameter for a low cross-polarization coupling is the difference in the dielectric constant, the Δβ, which leads to a short coupling beat length and a lower magnitude of the cross-polar component in a twisted dielectric waveguide section. The cross-section of the dielectric waveguide features modifications to a cylindrical rod waveguide. An air hole is added to the center of the cross-section to reduce the dielectric loss, and three modifications are proposed to increase the Δβ and to reduce the cross-polarization coupling. The first one is to flatten the outer circumference of the cross-section, the second one is to use two air holes, and the third one is to use a slot-shaped air hole. The resulting Δβ of each approach is investigated, and two cross-sections of the first approach are manufactured, since the first approach increases the Δβ with a much smaller impact on the β of two polarizations. The measurements of the dielectric waveguides show an attenuation of around -2 dB/m, with the cross-polarization coupling below -20 dB. Additionally, a cross-section combining the first and second approaches is manufactured to demonstrate the low cross-polarization coupling and the high Δβ achieved. Next, the transitions from the proposed dielectric waveguides to a WR15 waveguide and a 3mm by 3mm square metal waveguide are presented. The WR15 waveguide is single-polarized and easy to manufacture from off-the-shelf WR15 components, while the square waveguide transition offers greater design flexibility for minimal insertion loss. In both transition designs, a high-permittivity pin is inserted into the air hole at the end of the dielectric waveguide to concentrate the E-field distribution at the transition. The simulated results show around 1 dB insertion loss for the WR15 transition and below 0.45 dB for the square transition. Then, dual-polarized dividers in metal waveguide technology are presented. The dividers have square ports of 3mm by 3mm for dual-polarization operation, and a Y-junction or T-junction in the center, with impedance transformers in doubleridged waveguides to match the impedance at the junction. A given dividing ratio can also be achieved by adjusting the impedance transformer sections, and a 2 dB and a 6 dB unequal divider are presented. A Y-junction equal divider and a Tjunction 6 dB unequal divider are manufactured and measured, with the measured results agreeing with the simulated results. Finally, clip antennas are presented as radiating elements to complete the data distribution system. The clip antenna is an antenna that can be non-destructively mounted onto the dielectric waveguide and radiate a portion of the power on the waveguide to the desired direction, with a well-defined beam shape and minimal impact on the propagating wave on the dielectric waveguide. The presented clip antennas can be easily manufactured with a metal sheet, and have a configurable realized gain in the range of -10 - 5 dBi. Furthermore, multiple clip antennas can be used together to form a clip antenna array to increase the realized gain. In the end, the dielectric waveguide and the clip antennas are combined for a data rate measurement. The measurement setup includes a transmitter with an output power of 22.5 dBm, a WR15 to dielectric waveguide transition, 10m of dielectric waveguide, a three-clip-antenna array, 2m of free space, and a receiver with a 25 dBi horn antenna. The measurement is conducted in channel 1 of the IEEE 802.11ad standard, with a center frequency of 58.32 GHz. With a bandwidth of 2.16 GHz, an EVM of -20.8 dB is measured, constituting a packet error rate below 10% with MCS 12.4 of IEEE 802.11ad, and a stable Wi-Fi payload data rate of 6.93 Gbps.