Antenna/Propagation Domain Self-Interference Cancellation (SIC) for In-Band Full-Duplex Wireless Communication Systems.

In-band full duplex (IBFD) is regarded as one of the most significant technologies for addressing the issue of spectrum scarcity in 5G and beyond systems. In the realization of practical IBFD systems, self-interference, i.e., the interference that the transmitter causes to the collocated receiver, poses a major challenge to antenna designers; it is a prerequisite for applying other self-interference cancellation (SIC) techniques in the analog and digital domains. In this paper, a comprehensive survey on SIC techniques in the antenna/propagation (AP) domain is provided and the pros and cons of each technique are studied. Opportunities and challenges of employing IBFD antennas in future wireless communications networks are discussed

Wideband Self-Adaptive RF Cancellation Circuit for Full-Duplex Radio: Operating Principle and Measurements

This paper presents a novel RF circuit architecture for self-interference cancellation in inband full-duplex radio transceivers. The developed canceller is able to provide wideband cancellation with waveform bandwidths in the order of 100 MHz or beyond and contains also self-adaptive or self-healing features enabling automatic tracking of time-varying self-interference channel characteristics. In addition to architecture and operating principle descriptions, we also provide actual RF measurements at 2.4 GHz ISM band demonstrating the achievable cancellation levels with different bandwidths and when operating in different antenna configurations and under low-cost highly nonlinear power amplifier. In a very challenging example with a 100 MHz waveform bandwidth, around 41 dB total cancellation is obtained while the corresponding cancellation figure is close to 60 dB with the more conventional 20 MHz carrier bandwidth. Also, efficient tracking in time-varying reflection scenarios is demonstrated.Comment: 7 pages, to be presented in 2015 IEEE 81st Vehicular Technology Conferenc

In-Band Full-Duplex 통신용 고격리도 이중편파 송수신기 안테나 어레이에 관한 연구

학위논문(석사) -- 서울대학교대학원 : 공과대학 전기·정보공학부, 2023. 2. 오정석.In this thesis, we focused on realizing the propagation domain of transmitter and receiver system composed of the antennas and isolators. Firstly, a logical design procedure based on a new perspective of the common mode (CM) and differential mode (DM) theory for a dual-polarized antenna in sub-6 GHz N78 band (3.3-3.8 GHz) has been proposed. Next, novel illumination topologies and decoupling methodologies enabling dual-polarized multi-path coupling suppression for 5G sub-6 GHz transmit/receive (TRx) antenna arrays have been presented. For the antenna design, a novel elaborate design method using field concentration has been established via the mode segmentation of S-parameters. Interestingly, an improvement in the port isolation between two different polarizations is achieved by using an independently controllable Smith chart trace for each mode using simple methodologies. To provide a deep physical insight into the mechanism of realizing the dual-polarized antenna, the corresponding field distributions based on the CM and DM analysis have been proposed for the first time, and the proposed antenna has been simulated, fabricated, and measured. The simulation as well as experimentally measured results show that the antenna can offer peak isolations of 40 dB, a gain of 8 dBi, cross-polarization discrimination of 20 dB, an efficiency of 92% with stable radiation patterns, and a profile of 0.14λ across 3.3-3.8 GHz, using FR-4 substrates for low-cost. Furthermore, this study not only offers knowledge on cross-polarization but also provides the active S-parameters for all possible amplitude and phase sequences to reflect realistic scenarios. For the isolator design, the isolator composite consists of the proposed planar inverted-L isolator (PILI) and electromagnetic band-gap (EBG). To consider dual-polarized multi-path isolations in reliable 5G integration scenarios, a low profile (0.13λ at 3.5 GHz) antenna with dual (±45° slant) polarization, impedance bandwidth of 40%, and port isolation of 25 dB is proposed. It was demonstrated that the proposed PILI could significantly suppress the direct coupling and ground coupling between TRx. Their composite combined with EBGs can further improve their dual-polarized decoupling. Two sets of 3.5GHz 1×4 antenna arrays with 45° - slant polarization and the proposed PILI/EBG composite were designed, manufactured, and measured for simultaneous decoupling of eight paths among the TRx antenna elements. Finally, the measured results reveal that the overall isolation level of the dual-polarized array configuration is approximately 70 dB with a low profile (0.14λ), maintaining the matching and port isolation conditions.본 논문은 안테나와 아이솔레이터로 구성된 송신기와 수신기의 전파영역 구현에 집중하였다. 첫 째로, 단순 파라미터 스터디가 아닌 새로운 관점의 논리적인 Common Mode and Differential Mode (CMDM)에 기반 설계 절차를 sub-6 GHz N78 밴드 (3.3-3.8 GHz)에 대하여 제시하였다. 다음으로, 이중편파 다중경로 커플링 억제를 위한 5G sub-6 GHz 대역 송수신기 안테나 어레이의 획기적인 구조와 디커플링 방법을 제시하였다. 안테나 설계에 대하여, S파라미터 모드 분할을 통한 필드 집중 방법을 이용하여 섬세한 설계법을 제시하였다. 흥미롭게도, 앞서 제시한 간단한 방법을 이용해서 각 모드에 독립적인 조절이 가능한 스미스 차트를 통해 각기 다른 편파 사이의 포트 격리도를 개선하였다. 이중편파 안테나의 동작원리에 대한 깊은 물리적 통찰력을 제공하기 위하여, CMDM 분석에 기반한 대응하는 필드 분포를 최초로 제시하였고 제안된 안테나는 시뮬레이션, 제작, 측정되었다. 시뮬레이션뿐만 아니라 실험을 통한 측정 결과는 안테나가 FR-4기판을 사용하여 저비용 제작을 하였고 40 dB의 포트 격리도, 8 dBi의 이득, 20 dB의 XPD, 92 %의 효율과 안정적인 빔패턴을 저자세로 얻었다. 게다가, 본 연구는 실제 동작 상황을 반영하기 위하여 Cross 편파에 대한 지식뿐만 아니라 active S파라미터를 가능한 모든 진폭과 위상조합에 대하여 제공했다. 아이솔레이터 설계에 대하여, 아이솔레이터 복합체는 평면 역-L 모양 (PILI)과 전자기파 밴드갭 (EBG)로 구성되어있다. 5G 실제 상황을 위하여 이중편파 다중격로를 고려하였다. 안테나는 40%의 임피던스 대역폭, 25 dB의 포트 격리도를 갖는다. 제안된 PILI는 송신기와 수신기 사이에 주요하게 직접적인 커플링과 그라운드를 통한 커플링을 억제할 수 있음이 증명되었다. EBG와 결합된 복합체는 추가로 이중편파 디커플링을 수행할 수 있다. 송신기 수신기를 반영하여, 1×4 어레이 안테나의 두 세트와 PILI/EBG 복합체가 8개의 결과를 동시에 만족하기 위하여 설계, 제작, 측정 되었다. 최종적으로, 측정된 결과는 임피던스와 포트 격리도는 유지하면서 전체적인 이중편파 어레이의 격리도는 대략 70 dB의 결과를 얻었다.1. Study Background 1 2. Antenna Design 4 2.1 Introduction 4 2.2 Principle of the CM and DM Theory 8 2.3 Design of the Dual-Polarized Antennas 11 2.3.1 Design Procedure 14 2.3.2 Experimental Results 17 2.4 Intensive Interpretation 20 2.4.1 Active S-parameters 20 2.4.2 Cross-Polarization Discrimination 24 3. Isolator Design 26 3.1 Introduction 28 3.2 Design of Decoupling Structure 30 3.2.1 Wall Analysis 30 3.2.2 Transmission Line-Based Analysis 33 3.2.3 Isolator with EBG 40 3.3 Measurement and Analysis 45 4. Conclusion 48 References 50 Abstract in Korean 55석

Inkjet Printed Flexible Patch Antennas for Full Duplex and Circular Polarization Applications

Flexible devices are getting more popular nowadays because of it’s lightweight, small size, portability, less expensive, environment friendly, and disposability. Flexible antenna, part of flexible devices, has become an important component of research for electrical engineers. The flexible antenna can be built using different materials like PET, PEN, liquid crystal polymer, PDMS, and textiles like woolen felt, cotton, cordura, and fleece as substrate. This thesis focuses on designing and fabricating antennas on PET paper by using inkjet printing for full duplex and circular polarization applications. Firstly, a flexible full-duplex antenna is proposed with robust performance and high isolation for 5.8 GHz using foam and PET paper. The patch of the antenna is modified by corner cut and inset feeding, while the defected ground structure is used to improve isolation between transmit and receive ports. Silver nanoparticle ink is used for printing the antenna in an inkjet printer. The fabricated version supports simulated results by showing acceptable performance in desired bandwidth. Bending tests and human body loading experiments are carried out on the fabricated antenna to demonstrate the antenna’s effectiveness for wearable applications. To the best of author’s knowledge, this is the first flexible full duplex antenna designed, achieving a high isolation level of -50 dB. Moreover, wide bandwidth, improved gain, and radiation efficiency, low cost, easy fabrication, and robust performance make it a good option for 5.8 GHz wearable applications. Secondly, a simple and compact CPW-fed circularly polarized antenna is presented. The proposed antenna consists of a modified “S” shaped patch, which has slots in three different places along with a slot in the ground plane. These slots contribute to increasing the bandwidth of the axial ratio. The antenna has a 3 dB axial ratio bandwidth of 10.47% (4.07 GHz- 4.52 GHz) and an impedance bandwidth of 17.53% (3.8 GHz - 4.53 GHz) covering the full region of axial ratio band. Moreover, this antenna is designed using PET paper which makes it flexible in nature and the first flexible antenna in the discussed frequency range to the best of author’s knowledge. Finally, an inkjet printed circularly polarized antenna using CPW feeding on PET substrate is proposed. The antenna is designed and optimized using ANSYS HFSS, which operates at 4.01 GHz - 5.05 GHz and 6.23 GHz - 7.58 GHz with a return loss of < -10 dB. On top of that, the antenna shows an axial ratio of less than 3 dB at 4.23 GHz - 4.62 GHz and 7.11 GHz - 7.36 GHz, whereas left hand circular polarization (LHCP) is observed in the first band and right hand circular polarization (RHCP) is observed in the second band. The dimension of the antenna is 31 mm x 37 mm x 0.135 mm. Measurement of the fabricated version shows good agreement with the simulated version. To the best of author’s knowledge, this antenna is the first flexible CPW-fed circularly polarized antenna with dual band

Massive MIMO for Next Generation Wireless Systems

Multi-user Multiple-Input Multiple-Output (MIMO) offers big advantages over conventional point-to-point MIMO: it works with cheap single-antenna terminals, a rich scattering environment is not required, and resource allocation is simplified because every active terminal utilizes all of the time-frequency bins. However, multi-user MIMO, as originally envisioned with roughly equal numbers of service-antennas and terminals and frequency division duplex operation, is not a scalable technology. Massive MIMO (also known as "Large-Scale Antenna Systems", "Very Large MIMO", "Hyper MIMO", "Full-Dimension MIMO" & "ARGOS") makes a clean break with current practice through the use of a large excess of service-antennas over active terminals and time division duplex operation. Extra antennas help by focusing energy into ever-smaller regions of space to bring huge improvements in throughput and radiated energy efficiency. Other benefits of massive MIMO include the extensive use of inexpensive low-power components, reduced latency, simplification of the media access control (MAC) layer, and robustness to intentional jamming. The anticipated throughput depend on the propagation environment providing asymptotically orthogonal channels to the terminals, but so far experiments have not disclosed any limitations in this regard. While massive MIMO renders many traditional research problems irrelevant, it uncovers entirely new problems that urgently need attention: the challenge of making many low-cost low-precision components that work effectively together, acquisition and synchronization for newly-joined terminals, the exploitation of extra degrees of freedom provided by the excess of service-antennas, reducing internal power consumption to achieve total energy efficiency reductions, and finding new deployment scenarios. This paper presents an overview of the massive MIMO concept and contemporary research.Comment: Final manuscript, to appear in IEEE Communications Magazin

Space-Air-Ground Integrated 6G Wireless Communication Networks: A Review of Antenna Technologies and Application Scenarios

A review of technological solutions and advances in the framework of a Vertical Heterogeneous Network (VHetNet) integrating satellite, airborne and terrestrial networks is presented. The disruptive features and challenges offered by a fruitful cooperation among these segments within a ubiquitous and seamless wireless connectivity are described. The available technologies and the key research directions for achieving global wireless coverage by considering all these layers are thoroughly discussed. Emphasis is placed on the available antenna systems in satellite, airborne and ground layers by highlighting strengths and weakness and by providing some interesting trends in research. A summary of the most suitable applicative scenarios for future 6G wireless communications are finally illustrated