As the world continues to adopt the next generation of mobile technology, dual-band 5G wireless communications are becoming increasingly significant. 5G technology operates on two different frequency bands, the sub-6 GHz Frequency Range (FR1) and the millimeter wave (MMW) Frequency Range (FR2). The special features in each band enable 5G dual-band communication to provide better coverage and capacity than previous generations of wireless networks. This is especially essential for applications that need high-bandwidth and low-latency connections, such as virtual and augmented reality, autonomous vehicles, and industrial automation. Furthermore, dual-band 5G can help alleviate network congestion in urban areas by redirecting traffic to the MMW band, which has considerably greater capacity. As a result, dual-band 5G is expected to play a critical role in facilitating the next wave of technological innovation and revolutionizing the way we live and work. A dual-band antenna with a large frequency ratio (FR) is required due to the significant difference between each frequency band in 5G. Research on dual-band antennas is facing challenges such as low FR and a lack of a specific design methodology. Despite attempts to develop dual-band antennas with large FRs, there are still issues with low performance and limited bandwidth. This study introduces a novel approach for designing a dual-band antenna with a large FR. The proposed solution draws inspiration from a hybrid design of a dual-band antenna to achieve a large FR, and from the parabolic reflector antenna design to significantly enhance gain in the upper band. The lower band antenna in this design serves as both a radiator for the lower band and a reflector to align the beam in the upper band. This approach can be used to design dual-band antennas for various frequencies. In this thesis, we present a comprehensive model and framework for designing an antenna integrated reflector that offers a large FR. The proposed model is capable of producing an antenna that meets the requirements of the targeted application, namely 5G. This antenna exhibits wideband characteristics and high gain. Two different antenna integrated reflectors, named AIR-I and AIR-II, were designed based on the proposed model. AIR-I has a FR of 10.1. As for AIR-II, due to the presence of dual-band upper antennas, it has a lower band at 1.35 GHz and two upper bands at 13 GHz and 24 GHz thus, a FR of 9.5 and 18, respectively. The above design followed a specific purpose. It uses a 24 GHz/1.35 GHz frequency ratio of 18 to showcase the antenna performance in the context of dual-band 5G. However, the measurement facilities being limited to 20 GHz, a frequency ratio of 9.5 at 13 GHz/1.35 GHz was measured for the AIR-II, as proof of concept. Then, two prototypes were fabricated from AIR-II namely, Prototype-I and Prototype-II. While it would have been possible to demonstrate a proof of concept from a single prototype, it has been decided to produce and test two samples to enable a more exhaustive examination of the subject and obtain additional data that would lend greater support to the model outlined in this thesis. Prototype-I had the same structure as AIR-II and had an operational bandwidth of 0.69 GHz-1.74 GHz / 6 GHz-18 GHz and a FR of 9.9. On the other hand, Prototype-II had an operational bandwidth of 0.69 GHz-1.74 GHz / 13 GHz-18 GHz and a FR of 12.8. These prototypes exhibited maximum bandwidths of 100% and 86%, respectively. Furthermore, at the upper band, Prototype-I achieved a peak gain improvement of 12.6 dB, while Prototype-II achieved an improvement of 8.7 dB. These results demonstrated the significant advantages of our proposed methodology in dual-band antenna design.

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This dissertation presents new circuit architectures and techniques for improving the performance of several key BiCMOS RFIC building blocks used in radar and wireless communication systems operating up to millimeter-wave frequencies, and the development of an advanced, low-cost and miniature millimeter-wave concurrent dual-band transmitter for short-range, high-resolution radar and high-rate communication systems. A new type of low-power active balun consisting of a common emitter amplifier with degenerative inductor and a common collector amplifier is proposed. The parasitic neutralization and compensation techniques are used to keep the balun well balanced at very high frequencies and across an ultra-wide bandwidth. A novel RF switch architecture with ultra-high isolation and possible gain is proposed, analyzed and demonstrated. The new RF switch architecture achieves an ultra-high isolation through implementation of a new RF leaking cancellation technique. A new class of concurrent dual-band impedance matching networks and technique for synthesizing them are presented together with a 25.5/37-GHz concurrent dual-band PA. These matching networks enable simultaneous matching of two arbitrary loads to two arbitrary sources at two different frequencies, utilizing the impedance-equivalence properties of LC networks that any LC network can be equivalent to an inductor, capacitor, open or short at different frequencies. K- and Ka-band ultra-low-leakage RF-pulse formers capable of producing very narrow RF pulses in the order of 200 ps with small rising and falling time for short-range high-resolution radar and high-data-rate communication systems are also developed. The complete transmitter exhibiting unique characteristics obtained from capabilities of producing very narrow and tunable RF pulses with extremely RF leakage and working concurrently in dual bands at 24.5 and 35 GHz was designed. Capability of generating narrow and tunable RF pulses allows the radar system to flexibly work at high and multiple range resolutions. The extremely low RF leakage allows the transmitter to share one antenna system with receiver, turn on the PA at all time, comply the transmitting spectrum requirements, increase the system dynamic range, avoid harming to other systems; hence improving system size, cost and performance. High data-rate in communication systems is achieved as the consequence of transmitting very narrow RF pulses at high rates. In addition, the dissertation demonstrates a design approach for low chip-area, cost and power consumption systems in which a single dual-band component (power amplifier) is designed to operate with two RF signals simultaneously.

Since its invention, phased array has been extensively applied in both military and civil areas. The applications include target detecting and tracking, space probe communication, broadcasting, human-machine interfaces, and remote sensing. Although the phased array applications show a broad range of potential market, there are some limitations of phased array's development: high cost, complex structure, narrow bandwidth, and high power consumption. Therefore, novel ideas are needed to reduce these constraints. In this thesis, several new approaches about the design and application of phased array are presents. First, the principle of phased array and fundamental design equations are introduced. Second, a new application of phased array antenna for radar respiration measurement is presented. By integrating a 4×4 Butler matrix with four-element antenna array, there will be four distinct main beams in radiation pattern. This new approach can improve the measurement accuracy and realize a high detecting rate. Third, a compact phased array antenna system based on dual-band operations is introduced. Dual-band function can make N-antenna system obtain 2N unique radiation beams (N is an integer) and achieve a significant size reduction compared to the conventional single-band system. To verify the design concept, a four-element phased array antenna working at 5GHz and 8GHz is designed and fabricated. The measurement results make a good agreement with the simulations. Finally, a novel architecture of steering phase feeding network by using bi-directional series-fed topology is presented. This bi-directional series-fed network needs less phase shifters and realizes steering phase function by applying control voltage.

This thesis presents a brief introduction to microwave components and technology. It also presents two novel dual-band designs, their analysis, topology, simulation and fabrication. In chapter 2, a novel dual-band bandpass filter using asymmetric stub-loaded stepped-impedance resonators (SLSIRs) operating at 1 and 2.6 GHz is shown. This type of design applies suitable arrangements to improve the filter’s performance. Then, in chapter 3, a novel dual-band balun (transforms unbalanced input signals to balanced output signals or vice versa) operating at 1.1 and 2 GHz with flexible frequency ratios is presented, which has more advantages in microwave applications. Then, conclusion and future works are discussed in chapter 4.

As the wireless technology maturing, the wireless systems are evolving towards the development of new applications with broad band access and also the higher data rate. This necessity will give rise to the new WLAN standards as well as minimizing the cost, high QoS and security features of the wireless setup. It will also lift the trends towards the miniaturizination of hand-held devices, high data rates, higher bandwidth and robust performance on present and future WLAN standards, IEEE 802.11a/ 802.11b and 802.11g. A Coplanar waveguide (CPW) fed compact and optimized monopole antenna printed on a substrate of Rogers TMM 4 is studied in this paper. The proposed antenna is fabricated and measured to verify the response for Wireless applications. It is broadband antenna which has dual band characristics and can operate simultaneously both at 2.4 GHz and 5.2 GHz frequency bands for Wireless Local Area Network (WLAN) application. Furthermore it is studied in detail that how the antenna performance and operation is affected by changing the parameters of antenna. The antenna has satisfactory return loss characteristics in desired range of frequency. The antenna has acceptable gain and directivity. The proposed antenna has a return loss value S11 < -10 dB. The impedance bandwidth of antenna is high and the radiation pattern of antenna is omnidirectinal which fulfill the WLAN requirements.

In the thesis, we designed a metamaterial radome to increase the antenna gain. Owing to the need of high-directivity radiation in fix-point communications, antenna array and reflective antenna had been used to increase the directivity of antenna traditionally. Complicated feed and huge antenna size are the disadvantages of these techniques. We proposed a simpler metamaterial radome to increase the antenna gain. We find the subwavelength-hole structure formed by four Jerusalem cross structures can collimate electromagnetic wave originally spreading out from the holes. With the same size, multiple subwavelength holes in metamaterial radome can further enhance the antenna gain. We showed that metamaterial radome with 9 subwavelength holes can improve the gain by about 3.5 dB. In addition, we applied the concept of Fabry-Perot Cavity (FPC) to find the suitable distance between the radome and the antenna. When the resulting electromagnetic waves are in-phase, the radome can increase the antenna gain effectively. Recently, high-directivity radiation in fix-point communications is required and in the meantime multi-mode communication systems have become more and more popular. For practical purposes, we designed a coplanar dual-band metamaterial radome to be operated at 2.5 GHz and 3.5 GHz for WiMAX. This structure allows adjustment of its characteristics independently at each band. This coplanar dual-band radome can enhance the antenna gain by about 1.74 dB and 2.08 dB at 2.5 GHz and 3.5 GHz, respectively.

In general, Dual-Band technology enables microwave components to work at two different frequencies. This thesis introduces novel dual-band microwave components and their applications. Chapter 2 presents a novel compact dual-band balun (converting unbalanced signals to balanced ones). The ratio between two working frequencies is analyzed. A novel compact microstrip crossover (letting two lines to cross each other with very high isolation) and its dual-band application is the subject of chapter 3. A dual-frequency cloak based on lumped LC-circuits is introduced in chapter 4. In chapter 5, a dual-band RF device to detect dielectric constant changes of liquids in polydimethylsiloxane (PDMS) microfluidic channels has been presented. Such a device is very sensitive, and it has significantly improved the stability. Finally, conclusion of this thesis and future works are given in chapter 6.

Yes / Two miniature low profile PIFLA antennas with a compact volume size of 30mm × 15mm × 8mm has presented in this paper. By applying the magnetic wall concept a reduced size dual-band and a wideband half PIFLAs for WLAN (2.4GHz/5.2GHz) and UWB applications are achieved. The dual-band antenna shows a relative bandwidth of 12% and 10.2% at ISM2400 and IEEE802.11a frequency bands respectively for input return loss less than 10dB. By carefully tuning the geometry parameters of the dual-band proposed antenna, the two resonant frequencies can be merged to form a wide bandwidth characteristic, to cover 3000MHz to 5400 MHz bandwidth (57%) for a similar input return loss that is fully covering the lower band UWB (3.1-4.8GHz) spectrum. The experimental and simulated return losses on a small finite ground plane of size 30mm × 15mm show good agreement. The computed and measured radiation patterns are shown to fully characterize the performance of the proposed two antennas. / MSCRC

In this thesis the general Chebyshev filter synthesis procedure to generate transfer and reflection polynomials and coupling matrices were described. Key concepts such as coupled resonators, non-resonant nodes have been included. This is followed by microwave duplexer synthesis. Next, a technique to design dual band filter has been described including ways to achieve desired return loss and rejection levels at specific bands by manipulating the stopbands and transmission zeros. The concept of dual band filter synthesis has been applied on the synthesis of microwave duplexer to propose a method to synthesize dual band duplexers. Finally a numerical procedure using Cauchy method has been described to estimate the filter and duplexer polynomials from measured responses. The concepts in this thesis can be used to make microwave filters and duplexers more compact, efficient and cost effective.