Influence of voltage and frequency dimming on power losses in HF electronic ballasts for compact fluorescent lamps

Compact Fluorescent Lamps (CFL) incorporating electronic ballasts are widely used in lighting. In many cases the ability to dim the lamp is a requirement Dimming can be achieved by varying the voltage supplied to the inverter or by changing the switching frequency of the inverter. The effect of dimming by both approaches on the power losses in the inverter is studied in this work. The lamp and associated inverter has been modeled in PSPICE, using a behavioral model for the CFL. Predicted losses are in good agreement with experimental data obtained from calorimetry. The model was then used to determine the distribution of losses within the inverter, enabling a comparison of the effects of the two dimming methods to be made. © 2006 IEEE.

Influence of voltage and frequency dimming on power losses in hf electronic ballasts for compact fluorescent lamps

Compact fluorescent lamps (CFLs) incorporating electronic ballasts are widely used in lighting. In many cases, the ability to dim the lamp is a requirement. Dimming can be achieved by varying the switching frequency of the inverter or by changing the voltage supplied to the inverter. The effect of dimming by both approaches on the power losses in the inverter is studied in this work. The lamp and associated inverter has been modeled in Pspice, using a behavioral model for the CFL. Predicted losses are in good agreement with experimental data obtained from calorimetry. After verification, the model was then used to determine the distribution of losses within the inverter, enabling a comparison of the effects of the two dimming methods to be made. © 2011 IEEE.

Compact phase shifter based on highly anisotropic liquid crystals for microwave frequency

A compact microwave phase shifter was designed and fabricated using highly anisotropic liquid crystals (LCs). It comprises a thin LC layer between a ground plane and a directly coupled and inverted microstrip line. The proposed folding configuration is beneficial for size reduction. Both simulation and experimental results confirm the compact size devices with reasonably good performance.

Voltage programmable dual-band bandpass/bandstop filter response in a single micro-electro-mechanical device

This paper reports on a switchable multi-band filter response achieved within a single micro-electro-mechanical device. A prototype device fabricated in a SOI process demonstrates a voltage programmable and tunable, dual-band, band-pass/band-stop response. Both analytical and finite element models are introduced in this paper to elucidate the operating principle of the filter and to guide filter design. Voltage programmability of the filter characteristic is demonstrated with the ability to independently tune the centre frequency and bandwidth for each band. A representative measurement shows that the minimum 3 dB-bandwidth (BW) is 155 Hz, 140Hz, and 20 dB-BW is 216 Hz, 203Hz for the upper-band and lower-band center frequencies located at 131.5 kHz and 130.7 kHz, respectively. © 2011 IEEE.

Dual-mode thin film bulk acoustic wave resonators for parallel sensing of temperature and mass loading.

Thin film bulk acoustic wave resonator (FBAR) devices supporting simultaneously multiple resonance modes have been designed for gravimetric sensing. The mechanism for dual-mode generation within a single device has been discussed, and theoretical calculations based on finite element analysis allowed the fabrication of FBARs whose resonance modes have opposite reactions to temperature changes; one of the modes exhibiting a positive frequency shift for a rise of temperature whilst the other mode exhibits a negative shift. Both modes exhibit negative frequency shift for a mass load and hence by monitoring simultaneously both modes it is possible to distinguish whether a change in the resonance frequency is due to a mass load or temperature variation (or a combination of both), avoiding false positive/negative responses in gravimetric sensing without the need of additional reference devices or complex electronics.

Dual-mode thin film bulk acoustic wave resonators for parallel sensing of temperature and mass loading

Thin film bulk acoustic wave resonator (FBAR) devices supporting simultaneously multiple resonance modes have been designed for gravimetric sensing. The mechanism for dual-mode generation within a single device has been discussed, and theoretical calculations based on finite element analysis allowed the fabrication of FBARs whose resonance modes have opposite reactions to temperature changes; one of the modes exhibiting a positive frequency shift for a rise of temperature whilst the other mode exhibits a negative shift. Both modes exhibit negative frequency shift for a mass load and hence by monitoring simultaneously both modes it is possible to distinguish whether a change in the resonance frequency is due to a mass load or temperature variation (or a combination of both), avoiding false positive/negative responses in gravimetric sensing without the need of additional reference devices or complex electronics. © 2012 Elsevier B.V.

Wide Area Passive UHF RFID System using Antenna Diversity Combined with Phase and Frequency Hopping

This paper presents a long range and effectively error-free ultra high frequency (UHF) radio frequency identification (RFID) interrogation system. The system is based on a novel technique whereby two or more spatially separated transmit and receive antennas are used to enable greatly enhanced tag detection performance over longer distances using antenna diversity combined with frequency and phase hopping. The novel technique is first theoretically modelled using a Rician fading channel. It is shown that conventional RFID systems suffer from multi-path fading resulting in nulls in radio environments. We, for the first time, demonstrate that the nulls can be moved around by varying the phase and frequency of the interrogation signals in a multi-antenna system. As a result, much enhanced coverage can be achieved. A proof of principle prototype RFID system is built based on an Impinj R2000 transceiver. The demonstrator system shows that the new approach improves the tag detection accuracy from <50% to 100% and the tag backscatter signal strength by 10dB over a 20 m x 9 m area, compared with a conventional switched multi-antenna RFID system.

800V lateral IGBT in bulk Si for low power compact SMPS applications

An 800V rated lateral IGBT for high frequency, low-cost off-line applications has been developed. The LIGBT features a new method of adjusting the bipolar gain, based on a floating N+ stripe in front of the P+ anode/drain region. The floating N+ layer enhances the carrier recombination at the anode/drain side of the drift region resulting in a very significant decrease in the turn-off speed and substantially lower overall losses. Switching speeds as low as 140ns at 25oC and 300ns at 125oC have been achieved with corresponding equivalent Rdson at 125oC below 90mω.cm2. A fully operational AC-DC converter using a controller with an integrated LIGBT+depletion mode MOSFET chip has been designed and qualified in plastic SOP8 packages and used in 5W, 65kHz SMPS applications. The device is fabricated in 0.6μm bulk silicon CMOS technology without any additional masking steps. © 2013 IEEE.

Chirp-enhanced direct modulation of a monolithic sub-Terahertz dual laser transmitter

A technique enabling 10 Gbps data to be directly modulated onto a monolithic sub-THz dual laser transmitter is proposed. As a result of the laser chirp, the logical zeros of the resultant sub-THz signal have a different peak frequency from that of the logical ones. The signal extinction ratio is therefore enhanced by suppressing the logical zeros with a filter stage at the receiver. With the aid of the chirp-enhanced filtering, an improved extinction ratio can be achieved at moderate modulation current. Hence, 10 GHz modulation bandwidth of the transmitter is predicted without the need for external modulators. In this paper, we demonstrate the operational principle by generating an error-free (bit error rate less than 10-9) 100 Mbps Manchester encoded signal with a centre frequency of 12 GHz within the bandwidth of an envelope detector, whilst direct modulation of a 100 GHz signal at data rates of up to 10 Gbps is simulated by using a transmission line model. This work could be a key technique for enabling monolithic sub-THz transmitters to be readily used in high speed wireless links. © 2013 IEEE.

Theoretical study of line narrowing in a sub-terahertz monolithic dual laser source with an integrated reflector

A monolithic design is proposed for low-noise sub-THz signal generation by integrating a reflector onto a dual laser source. The reflectivity and the position of such a reflector can be adjusted to obtain constructive feedback from the reflector to both lasers, thus causing a Vernier feedback effect. As a result, 10-fold line narrowing, the narrowing being limited by the resolution of the simulation, is predicted using a transmission line model. Finally, a simple control scheme using an electrical feedback loop to adjust laser biases is proposed to maintain the line narrowing performance. This line narrowing technique, comprising a passive integrated reflector, could allow the development of a low-cost, compact and energy-efficient solution for high-purity sub-THz signal generation. © The Institution of Engineering and Technology 2014.

Vertically-coupled microring laser array for dual-wavelength generation

We report the first demonstration of continuous-wave operation of a tunable, compact microring laser array based on a vertical-coupling architecture, well suited to larger-scale integration. Wavelength separation tunability from 4.9 to 6.3nm is observed. © 2006 Optical Society of America.