Transmission Line Resistance Compression Networks and Applications to Wireless Power Transfer

Microwave-to-dc rectification is valuable in many applications, including RF energy recovery, dc-dc conversion, and wireless power transfer. In such applications, it is desired for the microwave rectifier system to provide a constant RF input impedance. Consequently, variation in rectifier input impedance over varying incident power levels can hurt system performance. To address this challenge, we introduce multiway transmission line resistance compression networks (TLRCNs) for maintaining near-constant input impedance in RF-to-dc rectifier systems. A development of TLRCNs is presented, along with their application to RF-to-dc conversion and wireless power transfer. We derive analytical expressions for the behavior of TLRCNs, and describe two design methodologies applicable to both single and multistage implementations. A 2.45-GHz four-way TLRCN network is implemented and applied to create a 4-W resistance compressed rectifier system that has narrow-range resistive input characteristics over a 10-dB power range. It is demonstrated to improve the impedance match to mostly resistive but variable input impedance class-E rectifiers over a 10-dB power range. The resulting TLRCN plus rectifier system has >50% RF-to-dc conversion efficiency over a >10-dB input power range at 2.45 GHz (peak efficiency 70%), and standing wave ratio <;1.1 over a 7.7-dB range, despite a nonnegligible reactive component in the rectifier loads

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

Matching Network Elimination in Broadband Rectennas for High-Efficiency Wireless Power Transfer and Energy Harvesting

Impedance matching networks for nonlinear devices such as amplifiers and rectifiers are normally very challenging to design, particularly for broadband and multiband devices. A novel design concept for a broadband high-efficiency rectenna without using matching networks is presented in this paper for the first time. An off-center-fed dipole antenna with relatively high input impedance over a wide frequency band is proposed. The antenna impedance can be tuned to the desired value and directly provides a complex conjugate match to the impedance of a rectifier. The received RF power by the antenna can be delivered to the rectifier efficiently without using impedance matching networks; thus, the proposed rectenna is of a simple structure, low cost, and compact size. In addition, the rectenna can work well under different operating conditions and using different types of rectifying diodes. A rectenna has been designed and made based on this concept. The measured results show that the rectenna is of high power conversion efficiency (more than 60%) in two wide bands, which are 0.9-1.1 and 1.8-2.5 GHz, for mobile, Wi-Fi, and ISM bands. Moreover, by using different diodes, the rectenna can maintain its wide bandwidth and high efficiency over a wide range of input power levels (from 0 to 23 dBm) and load values (from 200 to 2000 Ω). It is, therefore, suitable for high-efficiency wireless power transfer or energy harvesting applications. The proposed rectenna is general and simple in structure without the need for a matching network hence is of great significance for many applications

High-efficiency 2.45 and 5.8 GHz dual-band rectifier design with modulated input signals and a wide input power range

This paper presents a new rectifier design for radio frequency (RF) energy harvesting by adopting a particular circuit topology to achieve two objectives at the same time. First, work with modulated input signal sources instead of only continuous waveform (CW) signals. Second, operate with a wide input power range using the Wilkinson power divider (WPD) and two different rectifier diodes (HSMS2852 and SMS7630) instead of using active components. According to the comparison with dual-band rectifiers presented in the literature, the designed rectifier is a high-efficiency rectifier for wide RF power input ranges. A peak of 67.041% and 49.089% was reached for 2.45 and 5.8 GHz, respectively, for CW as the input signal. An efficiency of 72.325% and 45.935% is obtained with a 16 QAM modulated input signal for the operating frequencies, respectively, 69.979% and 54.579% for 8PSK. The results obtained demonstrate that energy recovery systems can use modulated signals. Therefore, the use of a modulated signal over a CW signal may have additional benefits

Design of efficient microwave power amplifier systems

In the future communication systems, it is of key importance that the transceivers are capable of operating in multiple frequency bands and with complex signals. In this context, the power amplifier is a critical component of the transceiver, since it is responsible for most of the total power consumption in base stations and portable devices. Apart from the power consumption, the design of power amplifier systems must account for multi-band/broadband capabilities, high peak-toaverage power ratio signals and the mismatch effect caused by the various operating conditions. Hence, the design of power amplifier topologies that enhance the total system efficiency and reliability is a challenging task. This PhD dissertation introduces novel power amplifier architectures and solutions for modern communication systems. The contributions of this thesis can be divided in two parts. The first part deals with the study and design of power amplifier systems. It is of major importance that these designs provide linear amplification and operation at multiple frequency bands, which will permit the reduction of the cost and size of the devices. Additionally, we investigate the possibility to harvest the dissipated power from the power amplification process. For the development of the prototypes, lumped-element topologies, transmission line implementation and Substrate Integrated Waveguide (SIW) technology are adopted. In the second part of the thesis, novel matching networks are introduced and their properties are studied. In particular, resistance compression topologies are proposed to overcome the performance degradation associated with the sensitivity of nonlinear devices to environmental changes. These networks can be adopted in modern power amplifier architectures, such as envelope tracking and outphasing energy recovery power amplifier topologies, in order to provide improved performance over a wide range of operating conditions.Es primordial que los transceptores de los futuros sistemas de comunicación sean capaces de operar en múltiples bandas de frecuencia y con señales complejas. En este contexto, el amplificador de potencia es un componente crítico del transceptor dado que su consumo energético supone la mayor parte del consumo tanto de las estaciones base como de los dispositivos móviles. Aparte del consumo energético, los nuevos diseños de sistemas de amplificación de potencia deben considerar aspectos como la capacidad de operar en múltiples bandas o en banda ancha, el uso de señales con alta relación de potencia pico a potencia media (PAPR) y el efecto de desadaptación que aparece bajo las diferentes condiciones de funcionamiento. Por lo tanto, el diseño de nuevas topologías para amplificadores de potencia que mejoren la eficiencia total del sistema y la fiabilidad es una tarea compleja. Esta tesis doctoral presenta nuevas arquitecturas de amplificadores de potencia y soluciones para los sistemas de comunicación modernos. Las contribuciones de esta tesis se pueden dividir en dos partes. La primera parte se centra en el estudio y diseño de sistemas de amplificación de potencia con el fin de proporcionar amplificación lineal y funcionamiento en múltiples bandas de frecuencia, lo que permitirá reducir el coste y tamaño de los dispositivos. Además, se investiga la posibilidad de reutilizar la energía disipada en el proceso de amplificación de potencia. Para el desarrollo de los prototipos, se utilizan topologías hibridas, implementaciones con líneas de transmisión y tecnología de guía de onda integrada en sustrato (SIW). En la segunda parte de la tesis, se proponen redes de adaptación y se estudian sus propiedades. En particular, se proponen topologías de compresión de resistencia para minimizar el efecto que producen en el rendimiento la sensibilidad de los dispositivos no lineales a los cambios ambientales. Estas redes pueden ser utilizadas en arquitecturas modernas de amplificadores de potencia como pueden ser las topologías envelope tracking y outphasing energy recovery con el fin de proporcionar un rendimiento mejorado bajo múltiples condiciones de funcionamiento

A Wide Dynamic Range Rectifier Based on HEMT Device with a Variable Self-Bias Voltage

This brief focuses on a highly efficient rectifier based on a high-electron-mobility transistor (HEMT) with a wide dynamic range of input power. Due to the nonlinear characteristics of HEMT, the impedance mismatch at different input power levels is a major challenge in rectifier design. Herein, a variable voltage gate self-bias network is proposed. It can dynamically generate a DC voltage according to the input power level, and continuously provide the optimal bias for the HEMT, thereby improving the RF to DC conversion efficiency in a wide input power range. This design does not require any external sensing or dynamic control circuit. The power needed by the self-bias network is provided using a weak coupling structure placed at the input port, which couples a small amount of the received RF power to operate the self-bias network. It is demonstrated that the proposed rectifier can achieve a dynamic operating power range of 24 dB (from 1 to 25 dBm) for over 60% conversion efficiency, or 16 dB for over 70% conversion efficiency in the measurement