Rectifiers Based on Quadrature Hybrid Coupler with Improved Performance for Energy Harvesting

This paper presents a method for enhancing RF-dc conversion efficiency of the rectifier based on inkjet-printed quadrature based hybrid coupler (QHC) for wireless energy transfer systems. The input matching network and output load of the rectifier are optimized for optimal RF-dc conversion efficiency. Improvement of about 16 dB input power range is achieved for RF-dc conversion efficiency of 60%. The simulated efficiencies of the rectifiers with and without coupler for 3 MHz LTE signals and output power spectra densities at 1.5 GHz are illustrated

Integrated Filters and Couplers for Next Generation Wireless Tranceivers

The main focus of this thesis is to investigate the critical nonlinear distortion issues affecting RF/Microwave components such as power amplifiers (PA) and develop new and improved solutions that will improve efficiency and linearity of next generation RF/Microwave mobile wireless communication systems. This research involves evaluating the nonlinear distortions in PA for different analog and digital signals which have been a major concern. The second harmonic injection technique is explored and used to effectively suppress nonlinear distortions. This method consists of simultaneously feeding back the second harmonics at the output of the power amplifier (PA) into the input of the PA. Simulated and measured results show improved linearity results. However, for increasing frequency bandwidth, the suppression abilities reduced which is a limitation for 4G LTE and 5G networks that require larger bandwidth (above 5 MHz). This thesis explores creative ways to deal with this major drawback. The injection technique was modified with the aid of a well-designed band-stop filter. The compact narrowband notch filter designed was able to suppress nonlinear distortions very effectively when used before the PA. The notch filter is also integrated in the injection technique for LTE carrier aggregation (CA) with multiple carriers and significant improvement in nonlinear distortion performance was observed. This thesis also considers maximizing efficiency alongside with improved linearity performance. To improve on the efficiency performance of the PA, the balanced PA configuration was investigated. However, another major challenge was that the couplers used in this configuration are very large in size at the desired operating frequency. In this thesis, this problem was solved by designing a compact branch line coupler. The novel coupler was simulated, fabricated and measured with performance comparable to its conventional equivalent and the coupler achieved substantial size reduction over others. The coupler is implemented in the balanced PA configuration giving improved input and output matching abilities. The proposed balanced PA is also implemented in 4G LTE and 5G wireless transmitters. This thesis provides simulation and measured results for all balanced PA cases with substantial efficiency and linearity improvements observed even for higher bandwidths (above 5 MHz). Additionally, the coupler is successfully integrated with rectifiers for improved energy harvesting performance and gave improved RF-dc conversion efficienc

Impact of 5G Waveforms on Energy Harvesting Rectifier Performance

In this paper, an evaluation of impact of 5 MHz 5G FBMC waveforms on energy harvesting rectifier performance is presented. The 5 MHz 5G FBMC signals are used in Matlab. The simulated CCDFs of the rectifier for 5 MHz 5G signals at different input powers at 1.5 GHz are illustrated

Rectifier Nonlinearity Effects on 4G and 5G Wireless Systems

In this paper, a waveform comparison and rectifier nonlinearity effects on 4G and 5G wireless systems are presented. The 3 MHz CP-OFDM and 5G FBMC signals are used in Matlab simulations. It is noted that 3 MHz CP-OFDM signals have larger side-lobes in comparison with 5G FBMC signals. The 5G FBMC signals have stepper slope at the edges and very low out-of-band leakage. The simulated output spectra densities of the rectifier for 3 MHz LTE and 5G FBMC signals at 1.5 GHz are illustrated

Aperture Sharing Metasurface-Based Wide-Beam Antenna for Energy Harvesting

Since the available ambient power level is usually quite low for radio frequency energy harvesting, it is very desirable for an antenna to have both a high gain and a wide beamwidth. Usually, they cannot be achieved simultaneously. In order to overcome this limitation, a multi-port antenna using a nonuniform metasurface (MTS) is presented. In this MTS-based antenna, three modes with complementary radiation patterns are excited through one middle and two side aperture-coupled feeding ports. The first mode is the fundamental TM10 mode with in-phase current distributions on the MTS. It has a broadside directional radiation pattern with a high gain. The second and third modes are symmetrical to each other at a high mode. They have opposite current distributions on two sides of the MTS. These two modes have a directional radiation pattern with a tilted angle. These three modes share the same aperture but are excited by three different feeds. Each feed is connected to a rectifier. By combining direct current (DC) output to a single load, an antenna with a wide beam and a high gain can be effectively achieved, although each mode has the usual limitation of gain and beamwidth. The key advantage of this proposed rectenna is that the unit cells on the MTS layer can be reused to excite different MTS modes with different radiation patterns simultaneously. Thus, a wide beamwidth can be achieved. Three realized beams are oriented at −35°, 0°, and + 35° respectively. By combining the DC output from the three modes, the proposed rectenna has effectively achieved a beamwidth of 114° with a gain ranging from 8 to 9.8 dBi. The RF-to-DC conversion efficiency of the rectifiers is 3%-67% at 2.45 GHz when the input power ranges from −35 to 0 dBm. The proposed MTS antenna with an overall size of λ0 × λ0 × 0.03 λ0 can achieve 12% fractional bandwidth

암 진단 및 치료에 적용 가능한 마이크로파 능동 집적 탐침에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 2. 권영우.본 논문에서는 암 진단 및 치료에 적용 가능한 초소형 마이크로파 능동 집적 탐침에 대해 기술하였다. 생체 조직의 광대역 측정과 저전력 온열 치료에 적용 하기 위해 유전율 측정 회로를 평면형 동축 탐침에 집적하였고, 마이크로파 발생 회로를 어플리케이터에 집적하였다. MEMS 기술과 MMIC 기술을 적용함으로써 단일 플랫폼에 집적된 시스템으로 구현하여 집적도를 향상 시키고, 시스템을 소형화 하였다. 먼저 multi-state reflectometer를 이용하여 암 진단에 활용 가능한복소 유전율 측정 기술에 대해 제안하였다. 2, 16 GHz에서 동작하는 광대역 reflectometer는 이중 대역 위상 고정 루프 (PLL), 임피던스 튜너, RF 전력 검출기 등의 MMIC와 MEMS 기반의 방향성 결합기, 평면형 탐침을 집적하여 구현하였다. 제작한 능동 집적 탐침 시스템을 이용하여 생체 조직과 암 조직 등의 유전율을 측정함으로써 유용함을 확인하였고, 측정된 유전율과 표준값을 비교하여 시스템의 측정 정확도를 검증하였다. 또한 저전력 마이크로파 온열 치료 요법을 위한 능동 집적 탐침을 개발하였다. MEMS 공정을 통해 제작한 평면형 실리콘 탐침에 전압 제어 발진기, 구동 증폭기, 전력 증폭기를 집적하여 능동 집적 탐침 시스템을 제작하였다. 치료를 진행하는 동안, 마이크로파의 전력을 측정할 수 있도록 전력 검출기와 방향성 결합기도 함께 집적하였다. 암, 근육 등 다양한 생체 조직을 이용한 실험의 결과로부터 Ku 대역의 주파수에서 저전력 마이크로파 온열 치료가 가능함을 확인하였다. 마지막으로 자성 나노입자를 이용한 온열 치료에 적용하기 위해 능동 집적 탐침을 개발하였다. 자성 나노입자가 온열 치료 요법에 미치는 영향을 분석하기 위해 전자기-열 결합 해석을 수행하였고, 이로부터 자성 나노입자의 선택도 향상을 위한 최적의 주파수를 결정하였다. 발진기와 전력 증폭기 MMIC와 이중 채널 로그 전력 검출기, 방향성 결합기를 탐침에 집적하여 시스템을 제작하였다. 이를 이용한 실험 결과로부터 능동 집적 탐침의 성능을 확인하였으며, 자성 나노입자가 저전력 및 암 특이 마이크로파 온열 치료의 효율과 선택도를 향상시키는데 유용함을 검증하였다.This thesis presents miniaturized microwave active integrated probe systems applicable to cancer detection and treatment. To realize broadband detection and low-power hyperthermia, planar-type coaxial probes and heat applicators have been integrated with active circuits for permittivity measurement and microwave generation, respectively. Each integrated system is implemented on a single platform using Microelectromechanical Systems (MEMS) and monolithic microwave integrated circuit (MMIC) technologies for miniaturization and integration. First, a complex permittivity measurement technique using an integrated multi-state reflectometer (MSR) is proposed for cancer detection application. The broadband MSR covering both 2 and 16 GHz bands consists of a dual-band phase-locked loop, a directional coupler, an impedance tuner, two RF power detectors, and a micromachined silicon planar probe with an open-ended coaxial aperture. All the active and passive circuit components have been integrated on the micromachined probe platform in a small form factor of 6.8 mm × 50 mm × 0.6 mm. The performance of the fabricated integrated probe has been evaluated by comparing the measured permittivities of 0.9% saline, pork muscle, fat, and xenografted human breast cancer with the reference data. For low-power microwave hyperthermia, a Ku-band active integrated heat applicator is demonstrated. A planar-type coaxial applicator has been fabricated using silicon micromachining technology, on which a Ku-band voltage controlled oscillator (VCO), a driver amplifier, and a power amplifier (PA) have been integrated. A directional coupler and power detectors are employed for power monitoring. The fully integrated heat applicator has been realized in a small footprint of 8 mm × 56 mm. In-vitro and in-vivo ablation experiments on pork muscle, fat, and human-cancer xenografted nude mouse demonstrate the feasibility of low-power hyperthermia using Ku-band microwaves. Finally, an active integrated heat applicator for magnetic nanoparticle (MNP)-assisted hyperthermia is developed. The effect of the MNP on microwave hyperthermia has been analyzed by a coupled electromagnetic-thermal analysis. The optimum frequency for hyperthermia is determined by the coupled analysis. A 2-GHz source module consisting of a VCO and a PA has been implemented in MMICs and integrated on the heat applicator platform. A dual-channel log detector and a directional coupler have been also employed to monitor the power levels during hyperthermia. Experiment results show not only sufficient heating performance of the integrated applicator, but also the effectiveness of the MNP for low-power and cancer-specific microwave hyperthermia.Abstract i Contents iv List of Figures viii List of Tables xv 1. Introduction 1 1.1 Motivation 1 1.2 Microwave Cancer Detection 4 1.3 Microwave Hyperthermia 5 1.4 Outline of Thesis 7 2. Active Integrated Probe for Cancer Detection 9 2.1 Introduction 9 2.2 Principle of Operation 13 2.2.1 Multi-State Reflectometer 14 2.2.2 Governing Equation for Complex Permittivity 15 2.2.3 Determination of Complex Permittivity 17 2.2.4 Calibration 19 2.3 Design and Fabrication 21 2.3.1 Micromachined Planar Coaxial Probe 21 2.3.2 Impedance Tuner 30 2.3.3 Directional Coupler 34 2.3.4 Power Detector 37 2.3.5 Signal Source 39 2.3.6 Active Integrated Probe System 43 2.4 Measurement Results 46 2.5 Summary 52 3. Ku-Band Active Integrated Heat Applicator for Cancer Ablation 54 3.1 Introduction 54 3.2 Design and Fabrication 57 3.2.1 Micromachined Planar Coaxial Applicator 58 3.2.2 Microwave Source 63 3.2.3 Power Monitoring Circuits 67 3.2.4 Ku-Band Active Integrated Applicator System 67 3.3 Experiment Results 70 3.4 Summary 77 4. Active Integrated Heat Applicator for Magnetic Nanoparticle-Assisted Hyperthermia 79 4.1 Introduction 79 4.2 Magnetic Nanoparticle (MNP) 82 4.2.1 Heating mechanism of MNP 83 4.2.2 Permeability of MNP 84 4.3 Coupled Electromagnetic-Thermal Analysis 88 4.3.1 Coupled Electromagnetic-Thermal Problems 88 4.3.2 Electromagnetic Analysis 92 4.3.3 Thermal Analysis 94 4.3.4 Analysis Results 96 4.4 Design and Fabrication 103 4.4.1 Spiral Applicator 104 4.4.2 Microwave Source 107 4.4.3 Power Monitoring Circuits 111 4.4.4 Active Integrated Applicator for MNP-Assisted Hyperthermia 119 4.5 Experiment Results 122 4.6 Summary 132 5. Conclusion 134 Bibliography 137 Abstract in Korean 152Docto

Design and analysis of MOSFET based absorber for 5G massive MIMO base station.

Masters Degree. University of KwaZulu-Natal, Durban.The Fifth Generation (5G) technology suffers from a series of drawbacks ranging from the high cost of infrastructure development, replacement of old devices that may not be compatible with 5G, and losses within the 5G base station construct. During transmission, these losses have a negative effect on the overall performance and efficiency of transmission systems. The 5G massive-Multiple Input Multiple Output (MIMO) base station structure suffers from these losses. In addition, a loss experienced in the 5G technology is due to the reflection of signals from the receiver (Rx) branch connected to the circulators in the 5G massive-MIMO base station. Operators often specify that the worst-case reflections (return loss) over the system's operating frequency range must be 18 dB lower than the signal transmitted into the system. As feed systems become shorter and antenna systems are required to operate over broader frequency ranges, achieving an 18 dB return loss may not be practical, most especially at a 5G frequency regime. This reflection loss experienced in the 5G massive-MIMO base station results from the Rx branch's unmatched load impedance with the source impedance of the Transceiver (TX) branch. However, this problem can be solved by designing a matched circuit between the TX and RX branch of the base station. But Engineers are often faced with the challenge of designing a matching network for impedance mismatch, most especially at high frequency. For this reason, an N-channel Metal Oxide Field Effect Transistor (MOSFET) connected to a circulator has been proposed as an alternative solution to the performance and efficiency reducing effects of reflected radio frequency signal. The proposed model has been presented by connecting the Tx branch, antenna, Rx branch, and the MOSFET to each of the assumed four-port circulator ports. Two comparisons have been made between the source current and drain current of the MOSFET whenever there is a reflection from the base station's Rx branch, In this research, four case of reflection from the RX branch of the base station have been examined at 28 Ghz to analyse the model's performance. Various performance parameters (Insertion loss, Reflection coefficient, Total Power Absorbed by MOSFET (TPAM), Total Power Lost to Rectifier (TPLR), S-parameter, efficiency, etc.) have been analyzed for the validity, stability, and reliability of the proposed model. At worst case reflection from port-3 of the circulator, TPAM, TPLR and reflection coefficient have been observed to be 0.64 mW, 2.95 mW, and 0.0001179. Comparisons have been made with existing RF absorber models using efficiency, insertion loss, frequency, RF power absorption level, and ease of implementation as a standard. The model has been observed to have an efficiency greater than 90 %, an insertion loss more significant than 38 dBm at a frequency of 28 GHz