The Study Of Near-Field Focusing And Synthesis, Wideband Tunable Reflection Phase Shifter, And CTS Antenna

The research works are made based on scientific projects in China and US. This dissertation consists of three main parts:First one presents a new near field focusing and near field targeted sub-wavelength coil array; The second part is primarily for wide band non-dispersive reflection phase shifter which is based on the active non-Foster circuits loaded Artificial Magnetic Conductor (AMC). The proposed method meliorate the strong dispersion in passive AMCs; The third part is concerned with the wide band large aperture Continuous Transverse Stub (CTS) antenna. The plane wave feeding methods are talked and a wide band CTS antenna with large aperture is designed. The author’s major contributions are outlined as follows:1. The study of near field focusing for magnetic field and systhesis in the nean-field zone(1) Near field focusing for magnetic field.It is the first time, as we know, to present the design of a magnetic screen and its implementation in the world, which can pattern magnetic field into 256 programmable spots of small sub-wavelength dimension. A design methodology is outlined for designing a near field plate to achieve a desired focus. A sample of thickness 2.1 mm with 16 layers, in which there are 32 unclosed loops for focusing on each of 8 layers and optimized guiding strips on the other 8 layers, is fabricated and measured. The measurement results based on the near field measurement system we set up using the Labview software from National Instruments (NI) agree well with the simulation results. Finally, the response of the magnetic screen in the time domain is measured and computed showing the screen can be operated under pulse excitation. Such a device, capable of producing a programmable focused magnetic field, will find applications in biomedical devices, near-field imaging systems, data storage, and electromechanical actuators.(2) Synthesis and realization of programmable subwavelength coil array for near-field manipulation.Different from the relationship in the far-field zone, electronic field and magnetic field have a more complicated relationship in the near-field zone. Borrowing the concept of the superdirective electrically small antenna array, we present the design and experimental demonstration of a programmable dense phased array, which can manipulate the evanescent magnetic field leading to a precise controlled electronic filed pattern at an image plane in the near-field zone. A synthesis methodology is outlined for two dimensional near field manipulations. Simulation based on the full-wave electromagnetic solver clearly demonstrates the focused electronic field pattern, and its implementation is discussed. A sample of a three-layer dense phased array with 48 units is fabricated and measured. The consensus of the measured results with the simulated and synthesized results verifies the validation of the presented synthesis approach. This method can be used for other near-field subwavelength synthesis, and the the array will find applications in biomedical devices such as neural stimulations, and potentially other areas such as non-contact charging.2. Wideband tunable reflection phase shifter based on non-Foster circuit.We present, analytically and numerically, a wideband non-dispersive reflection phase shifter deployed with an artificial magnetic conductor (AMC) loaded with negative inductors and negative capacitors that are generated by non-Foster circuits. The AMC design is based on the high impedance surface. The analysis of the AMC with the ideal components provides the stability and tunability of the whole structure in theory. Finally, the non-Foster circuit is designed based on highly accurate, scalable measurement-based models, and co-simulated with a real lossy model of the AMC. The numerical results are in good agreement with the analysis and show a nearly flat reflection phase from 450MHz to 600MHz. This flat reflection phase can further be tuned by tuning the loaded inductance from 30 nH to 50 nH.3. Wide band Continuous Transverse Stub (CTS) antenna with a large radiation apertureA wideband Continuous Transverse Stub antenna with high efficiency and high polarization is designed. The working mechanism for improving the operating bandwidth and various feeding system have been talked. A comparison is made of the combination of the pillbox structure and ridged H horn antenna with half Maxwell fish eye lens for feeding system on the performance of CTS antenna. Finally, the CTS antenna with an aperture 600×600 mm2 excited by the improved pillbox feeding network is designed based on Ansoft HFSS and the simulation results show that the proposed antenna has a good radiation property in the opertating frequency band from 3-8.5 GHz, with -12 dB SLL and -51 dB cross polarization level. The radiation efficiency is higher than 51% in the whole band. All of the resuls meet the requirement.