Design of a ferrite rod antenna for harvesting energy from medium wave broadcast signals

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 transmissions. 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 proposed 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

A new representation of Dirac impulses in time-domain computer analysis of networks with ideal switches

A novel method for representing Dirac impulses in switched networks is presented. This method can be applied in the analysis and simulation of switched networks when the ideal switch model is used. The Dirac impulses in the time domain are not approximated by large values wich can give problems with conditioning and overflows. A logical representation of impulsive quantities is introduced. This representation did prove to be reliable and efficient in handling impulses which can be present at some of the switching transitions. Influence of impulses on the state of switches in the network can be easily accessed. No prior knowledge of circuit operation is needed to find the correct circuit topology after switching. The use of a state space description of the switched network allows to predict the possibly impulsive transitions. Therefore, the impulse analysis can be performed only for a limited number of transitions

Feedforward control of DC-DC PWM boost converter

A new feedforward control circuit suitable for applications in the de-de pulsewidth modulated (PWM) boost converter operated in the continuous conduction mode (CCM) is proposed, Its principle of operation is described, analyzed for steady state, and experimentally verified, The peak value of the sawtooth voltage at the noninverting input of a PWM modulator is held constant and the voltage at the inverting input of the PWM modulator varies in proportion to the converter de input voltage, As a result, the complement of the on-duty cycle (1 - D) is proportional to the de converter input voltage, yielding the converter output voltage theoretically independent of the converter input voltage, The circuit is very simple and significantly improves line regulation of the output voltage, The measured open-loop line regulation at fixed loads was less than 5% for the converter de input voltage change by 400%. The load regulation was also good even without a negative feedback loop

Self capacitance of inductors

A new method for predicting the stray capacitance of inductors is presented. The method is based on an analytical approach and the physical structure of inductors. The inductor winding is partitioned into basic celles many of which are identical. An expression for the equivalent capacitance of basic cell is derived. Using this expression, the stray capacitance is found for both single- and multiple-layer coils, including the presence of the core. The method was tested with experimental measurements. The accuracy of the result is good. The derived expressions are useful for designing inductors and can be used for simulation purposes

Analysis of networks with ideal switches by state equations

A new computer-oriented method for a large-signal time-domain analysis of networks containing ideal switches is presented. The method is based on a state variable approach that exploits an efficient novel algorithm developed for the systematic formulation of state equations and output equations for linear active networks, Switched networks consisting of linear elements and both externally and internally controlled switches can be investigated, Dirac's delta impulses are permitted in the analysis in order to find out the correct topology after switching, A new simple and convenient method for representing Dirac's delta impulses is also introduced, An example is both discussed in detail and analyzed with a computer code