Shahram Mohammad Nejad, Saeed Olyaee,
Volume 5, Issue 2 (6-2009)
Abstract
In this paper, we present a high accuracy laser range finder and velocimeter using ultra-fast time-to-digital converter (TDC). The system operation is based on the measuring the round-trip time of a narrow laser pulse. A low-dark current high-speed PIN photodiode is used to detect the triggered laser beam and to produce start signal. The pulsed laser diode generates 45W optical power at 30ns duration time and 905nm wavelength. A high-responsivity avalanche photodiode (APD) detects the reflected beam from the target. An optical head including beam splitter, lenses and optical filters is also designed and implemented. The signal conditioner of the system includes pre- and post-amplifiers, comparator, opto-isolators and monostable. By using a 3MV/W reach-through structure avalanche photodiode and a wideband pre-amplifier, the pre-amplifier output reaches 15.9mV, resulting from the minimum detectable optical power. The APD temperature and as a result its responsivity is controlled by a thermoelectric controller unit. The start and stop signals from PIN and APD are led to the time-to-digital converter to count the round-trip time of the laser beam. The system is tested by a retro-reflector as a target for 30-1200m distances. The resolutions of the distance and velocity measurement are limited to 18.75mm and 1.2m/s, respectively. In the worst condition, the minimum reflected optical power is limited to about 5.3nW in 1.2km distance.
H. Shayeghi, S. Pourjafar, F. Sedaghati,
Volume 17, Issue 2 (6-2021)
Abstract
This work introduces a new non-isolated buck-boost DC-DC converter. Interleaved configuration of the suggested structure increases the voltage conversion ratio. The voltage rate of the suggested converter can be stepped-up and stepped down for lower values of duty-cycle, which causes to decrease in the conduction losses of the system. The voltage conversion ratio of the recommended structure is provided with low maximum voltage throughout the semiconductor elements. Additionally, utilizing only one power switch facilitates converter control. Using a single power MOSFET with small conducting resistance, RDS-ON, increases the overall efficiency of the recommended topology. To verify the performance of the presented converter, technical description, mathematical survey, and comparison investigation with similar structures are provided in the literature. Finally, a laboratory scheme with a 100W load power rate at 50 kHz switching frequency is carried out to demonstrate the effectiveness of the proposed converter.
