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The rapid development of wireless communication, space-based radar systems and active military radars in the past decades gives rise to the necessary of information security and electromagnetic waves pollution, which arouse the requirement of perfect electromagnetic absorbers in both military and civil areas. Since the isolation of graphene and the first experimental demonstration of so-called perfect metamaterial absorber carried out in the early 21st century, a large amount of research has been directed at graphene based metamaterial absorbers. This thesis delivers pioneering developments on the design of printed graphene metamaterial absorbers on electromagnetic ranges including radio frequency, microwave frequency, and THz bands. This thesis focuses on the design and optimization of broadband metamaterial absorbers for civil and military applications and aims to provide novel ideas and combed design approaches for further development of the metamaterial absorbers with outstanding properties. This thesis presents several broadband printed graphene metamaterial absorbers with competitive properties. For example, the two multilayer structure metamaterial absorbers in chapter 3 provide ultra-wide operation bandwidth covering from C band to Ka band, and from S band to Ku band, respectively; the ultra-thin metamaterial absorber in chapter 4 achieves a relative absorption bandwidth of 178% with a thickness of merely 0.3 mm; the novel printed graphene AMC based radar absorber has pioneering advances compared with conventional metallic AMC based absorbers; the genetic algorithm optimized absorber indicates potentials of coding metamaterial absorbers. For the first time, the printed graphene AMC based radar absorber is experimentally demonstrated. Furthermore, the printed graphene metamaterial absorbers presented in this thesis are angle-insensitive and polarization-independent, and possess good flexibility thanks to the printed graphene patterns and flexible dielectric substrates. This work significantly provides novel approaches and more design flexibility to metamaterial absorbers, and expands the applications of printed graphene in the design and fabrication of metamaterial absorbers.

Graphene is claimed to be the wonder material that could potentially redefine our future technologies. The reason behind this is that graphene possesses outstanding electronic and mechanical properties. These unique properties could improve or reinvent a vast variety of applications that used every day in our life. For many years, most researches were focusing on fundamental physics and properties of the graphene. The progress of graphene has been quicker than other comparable materials although a lot of the most exciting areas of graphene science are still in the early stages. This thesis mainly focuses on the research of the realization of Radio Frequency (RF) graphene based wireless applications. To begin with, the tunability of graphene is utilized to design graphene based attenuator, single and multi-frequency reconfigurable antennas. These works show the feasibility of applying monolayer graphene sheet into RF applications and antenna designs. In addition to that, graphene conductive ink was made utilizing graphene flakes as base material and to make this screen printed material vastly more conductive by compression technique. This technique is low-cost and efficient, and the printed samples are flexible and environmental friendly. This thesis also presents the design and ministration of Ultra high frequency (UHF) Radio Frequency Identification (RFID) antenna, Near Field Communication (NFC) Antennas based on printed graphene technology. The pioneering experiments on printed graphene show this technology can significantly reduce the cost for RFID applications thanks to a much simpler process and lower material cost. Furthermore, the fundamental experiments on Graphene Oxide (GO) dielectric properties in GHz are applied in RF enabled humidity sensor and Wireless Graphene Security Networks extends the possibilities of applying printed graphene technology into internet of things (IoT) and wireless communication applications.

Motivated by the few work has done on the performance measurement of graphene passive devices compared to graphene active devices, several different types of passive devices are fabricated and measured. In general, the fabricated devices are divided into two parts: the DC devices and the RF devices, which based on the different electrical properties we measure in Chapter 7. For the DC devices, attention has been given to the resistance of CVD graphene that we later use in all the RF devices. The Dirac point seems only appears in the exfoliated graphene measurement, which is caused by the doping concentration difference between the exfoliated and CVD graphene. Meanwhile, the sheet resistance of graphene is calculated based on the four-point measurement. The sheet resistance of CVD graphene is around 291 Ω/sqFor the RF devices, the measurement is conducted on the two types of graphene passive devices from 0-110 GHz. The first type of graphene devices is the graphene CPW resonator. We measure the input impedances of the graphene resonators on different substrates (Si/SiO2 and GaAs) and with different graphene lengths (440 micro metre, 500 micro metre and 1415 micro metre). For the graphene resonators on Si/SiO2 substrate, the input impedance does show the resonance shift compared to the graphene-removed structure. The frequency position of the resonance that appears is consistent with the theoretical calculation result. Besides, the influence of the external conditions such as temperature on the performance of graphene resonators has been investigated. The input impedance resonance shows the shift when the external temperature varying from 40o C（313K） to 160o C （433K）. This measurement is undertaken with the graphene resonator on GaAs substrate. The second type of graphene devices is the graphene CPW transmission line on Si/SiO2 substrate. The S-parameters measured from VNA reveal that graphene within the transmission line acts as the transmission channel, which is a little lossy at the microwave frequency range. The poor transmission is also partially caused by the mismatching of the parasitic impedance, as well as the substrate loss, which is verified by the comparison result between the graphene transmission line and the graphene-removed transmission line. Similarly, the concern on the signal line coupling is also eliminated by using the graphene-removed structure.

Since the isolation of graphene in 2004, a large amount of research has been directed at 2D materials and their applications due to their unique characteristics. This thesis delivers pioneering developments on the applications of graphene and graphene oxide (GO) on electromagnetic ranges such as radio frequency, microwave frequency and THz bands, and specifically 2D materials based antennas, absorbers, sensors and etc. This thesis focuses on exploring electromagnetic applications of monolayer graphene, printed graphene and graphene oxide. In study of monolayer graphene applications, the theoretical and simulation studies are carried out to design tunable terahertz (THz) absorbers, tunable microwave wideband absorbers, and reconfigurable antennas, etc. These studies on the applications of monolayer graphene have proved prospective potentials of graphene in THz sensing, RCS reduction, and reconfigurable antennas. This thesis also presents pioneering advances on electromagnetic applications of printed graphene. Among these works, low-cost highly conductive and mechanically flexible printed graphene is developed for radio frequency (RF) applications. For the first time, effective RF radiation of printed graphene is experimentally demonstrated. Based on these results, applications of printed graphene including RFID (radio frequency identification) tags, anti-tampering RFID, EMI shielding, flexible microwave components such as transmission lines, resonators and antennas, conformable wideband radar absorbers, graphene oxide based wireless sensors, etc. are developed and experimentally demonstrated. This work significantly expands applications of graphene in electromagnetic areas.