Medium wave

Abstract: The encroachment of "civilization" on the site of a medium wave broadcasting array can give rise to distortions of its radiation pattern resulting in inadequate coverage of the service area, or even in the violation of licensing provisions. The radiation pattern distorts because RF currents are induced by the broadcasting antenna's field on any large metallic structures such as a highrise building or a high-tension power line. If the structure is resonant, these currents can be large and the reradiated field can be strong. This paper uses modern digital computer techniques to calculate the field reradiated from a power line near an AM broadcasting tower. The current distribution on the towers and "skywires" for a uniform power line is shown to exhibit distinct "off-resonance" and "resonant" behavior. The frequency dependence of the reradiated field is found to be simple loop resonance for a uniformly spaced power line, and so is a super-position of the resonant behavior of loops of many sizes for a complex site. The computer model is applied to analyze the azimuth pattern for a complex site near Hornby, Ontario where two power lines come close to an omnidirectional antenna. The computations are compared with scale model measurements. Since a perfectly conducting ground was used in the computations, the method may help to estimate the upper bound on the distortions of the azimuth pattern which could arise from the construction of a proposed power line near an existing broadcasting antenna.

Abstract: A medium wave infrared (MWIR) uncooled microbolometer focal plane array (FPA) has multiple stacks (200) with at least one uncooled IR detector (60) of a single MWIR band and a MWIR band absorber (210) applied using standard silicon processing techniques.

Abstract: Radio frequency (RF) energy harvesting is an emerging technology that has the potential to eliminate the need for batteries and reduce maintenance costs of sensing applications. The antenna is one of the critical components that determines its performance and while antenna design has been well researched for the purpose of communication, the design for RF energy harvesting applications has not been widely addressed. The authors present an optimised design for such an antenna for harvesting energy from medium wave broadcast transmis- sions. They derive and use a model for computing the optimal antenna configuration given application requirements on output voltage and power, material costs and physical dimensions. Design requirements for powering autonomous smart meters have been considered. The pro- posed approach was used to obtain the antenna configuration that is able to deliver 1 mW of power to 1 kΩ load at a distance of up to 9 km, sufficient to replace batteries on low-power sensing applications. Measurements using a prototype device have been used to verify the authors simulations.

Abstract: For smart grid applications, power line communications (PLC) have become a promising candidate to support some emerging services. Although it may employ frequencies above 500 kHz to guarantee reliable performance and fast response, potential interferences between such PLC access system and medium wave (MW)/short wave (SW) broadcast radios may be caused. This paper targets to evaluate the interference level specifically, based on which some detection and mitigation solutions are also proposed as cognitive PLC approaches. It starts with spectrum analyzer based measurements on the loop antenna and at two typical low voltage (LV) power line access networks in China to investigate the ingress caused by MW/SW broadcast radios, and the Electro Magnetic Interference (EMI) issue of PLC is also assessed by a field test. Then by performing a statistical analysis on the narrow-band radio interference level above the power line noise floor, an Adaptive Detection (AD) method for identifying radio stations is presented. Moreover, cooperative detection in cognitive radio (CR) is introduced as well by merging the detecting results achieved at different positions of the network to enhance the performance. Finally, the design aspects for such cognitive PLC access system are briefly discussed.