Ken W. Smart

Supplying the Power Requirements to a Sensor Network Using Radio Frequency Power Transfer

Wireless power transmission is a method of supplying power to small electronic devices when there is no wired connection. One way to increase the range of these systems is to use a directional transmitting antenna, the problem with this approach is that power can only be transmitted through a narrow beam and directly forward, requiring the transmitter to always be aligned with the sensor node position. The work outlined in this article describes the design and testing of an autonomous radio frequency power transfer system that is capable of rotating the base transmitter to track the position of sensor nodes and transferring power to that sensor node. The systems base station monitors the nodes energy levels and forms a charge queue to plan charging order and maintain energy levels of the nodes. Results show a radio frequency harvesting circuit with a measured S11 value of −31.5 dB and a conversion efficiency of 39.1%. Simulation and experimentation verified the level of power transfer and efficiency. The results of this work show a small network of three nodes with different storage types powered by a central base node.

Antenna impedance matching for maximum power transfer in wireless sensor networks

The conditions for maximum power transfer from a source antenna to a receiving antenna are examined when the two antennas are in close proximity. As an example, computed and measured results are described for the power transfer efficiency for two-element Yagi antennas. These results can be used to design matching networks between the antenna and a load such as a voltage multiplier for power transfer in a wireless sensor network. It is concluded that maximum PTE could be obtained by continuously tuning the antenna and matching network as the antenna separation and load conditions change.

A Millimeter-Wave Antenna Amplitude and Phase Measurement System

We describe the design and application of a system for measuring the magnitude and phase of antenna radiation patterns in the 182-194 GHz frequency range. A heterodyne receiver comparing antenna and reference signals is designed from readily available components and incorporated into a 12-m anechoic chamber. The chamber is used with or without a compact-range reflector for compact-range or far-field measurement of antennas up to 0.6 m in diameter. The measured phase variation of the system, when idle, averages 0.3° over 227 s and 4.5° over 30 min. The amplitude stability is better than ±0.15 dB over a 63-h period. Verification of the system is obtained through comparison with other measurements and calculated results on horn and pillbox antennas. The applications of the system are illustrated through its use in characterizing the magnitude and phase radiation patterns of a new beam-scanning pillbox antenna for a 186-GHz imaging system.

Design Aspects of an Antenna-MMIC Interface Using a Stacked Patch at 71–86 GHz

A bond-wire-free interconnection between monolithic microwave integrated circuit (MMIC) and antenna using a stacked patch configuration is investigated. An edge-fed patch on a gallium arsenide (GaAs) MMIC chip drives a patch antenna integrated in the lid of the MMIC package. The lid is formed using a liquid crystal polymer (LCP) substrate. The first implementation using a laminated multichip module (MCM-L) process is presented that covers the designated E-band spectrum for long-range wireless communications (71–86 GHz). Electromagnetic simulations and measurements of antenna radiation patterns agree well over the whole frequency range of interest. Important design aspects and manufacturing tolerances specific for the implementation of the interface in MCM-L millimeter-wave front-ends are presented. An alternative design is proposed for improved radiation patterns across the band.

Recent developments in measuring signal and noise in phased array feeds at CSIRO

We describe recent developments in measuring both signal and noise in phased array feeds for radio astronomy at CSIRO. We introduce new techniques including aperture array noise measurements with beamforming weights matched to a reflectors focal field. Weights are calculated via antenna-range and in-reflector measurements. We also describe the separation of system temperature and aperture efficiency via drift scans.

A cryogen-free HTS Josephson junction detector for terahertz imaging

A cryogen-free terahertz (THz) imaging system based on a high-temperature superconducting (HTS) Josephson junction detector is reported. The detector was made of a YBa2Cu3O7�x stepedge Josephson junction and integrated into an on-chip thin-film antenna. The HTS Josephson detector was cooled via a commercial mechanical cryocooler; an important step towards cryogen-free THz instrumentation, which is critical for industrial acceptance. In addition, it is shown that operating the detector in a cryocooler provides improved flexibility for optimizing the detector parameters and performance due to the ability to adjust the temperature compared to liquid nitrogen cooling methods. The dc and ac characteristics, the detector responsivity and the noise-equivalent power of the detector, and resulting image quality were studied as the function of operating temperatures.

Performance validation of the 19-element multibeam feed for the five-hundred-metre aperture spherical radio telescope

The performance of an L-band 19-element multibeam feed for the five-hundred-metre aperture spherical radio telescope is verified here. Radiation patterns have been measured in an anechoic chamber in the radiating near field of the array and compared with simulated radiation patterns from HFSS for the same conditions. Very good agreement is observed between the measurements and simulations.

A Practical and Portable Solids-State Electronic Terahertz Imaging System.

A practical compact solid-state terahertz imaging system is presented. Various beam guiding architectures were explored and hardware performance assessed to improve its compactness, robustness, multi-functionality and simplicity of operation. The system performance in terms of image resolution, signal-to-noise ratio, the electronic signal modulation versus optical chopper, is evaluated and discussed. The system can be conveniently switched between transmission and reflection mode according to the application. A range of imaging application scenarios was explored and images of high visual quality were obtained in both transmission and reflection mode.

Dual-band VHF/UHF smartphone antenna for mobile digital television

A dual-band VHF/UHF antenna suitable for use with a portable media device is proposed. The antenna is designed to attach to a smartphone or tablet as a folding cover. It uses a capacitively-coupled element for the VHF antenna and a shorted dipole for the UHF antenna. A low-pass filter network couples the two antennas together so they can be fed from a single port. Applications of the antenna are for the reception of mobile digital television signals such as the ATSC M/H standards or DVB-H on portable media devices such as smartphones or tablets.

E-band aperture coupled GaAs / LCP antennas

An E-band aperture coupled patch antenna using a combination of GaAs and liquid crystal polymer (LCP) substrates packaged with a laminated multi-chip module (MCM-L) process is presented in this paper. The antenna offers an electromagnetic interface between a GaAs MMIC and a separate dielectric antenna package. Design, manufacture, packaging and test results of the proposed antenna are presented. Measurement of a waveguide to microstrip transition used in the testing of the antenna is presented with excellent performance obtained across the E-band. Further analysis of the packaging method is required to assess the unpredicted loss observed in the measurements.