RF Driver for Acousto Optic Modulator

Abstract

Acousto Optic Modulator (AOM) is an interaction cell which, when excited with RF power, produces spectrum of colours from white light input. These interaction cells are used in several applications such as film recorders, Graphic arts, beam splitters, colour generators, optical defectors etc. To drive the AOM, an RF driver circuit is required. The RF driver is basically a high frequency converter and high power amplifier which can give a frequency of several MHz and power upto several watts. The conversion from low frequency to high frequency and amplifying to a few watts is not a new technique but it is difficult to amplify the signal with 100% duty cycle (without distortion). These applications require a linearly variable amplitude and high frequency generator which is very difficult to realise at around 300 MHz frequency. The power amplifiers presently available suffer from severe distortion as they are class-C amplifiers. Many power converters are available which convert AC power to drive DC motors using SCRs but those concepts can't be implemented in these applications because they are limited to a low frequency range. This paper describes the description of RF driver for AOM and design criteria for a specific application in film recorder. This design can also be used for applications where a highly linear, variable amplitude, frequency generation and linear power amplification is required at around 300 MHz frequency with 3W maximum power output.

Additional information

Notes on contributors

K M M Rao

Kunda M M Rao, is presently working as Group Head, Imaging & Image Processing Group in National Remote Sensing Agency, Dept of Space, Hyderabad and also as Operations Director for Indian Remote Sensing Satellites 1C & ID. He has acquired ME (Electronics) from BITS Pilani in 1972. He is fellow IETE, ISNT and Member IEEE (USA) and ISRS. He has bagged best invention award for SIPS 1989, Engineer of the year award from Institution of Engineers in 1989, Meritorious Invention Award for Colour Photowrite system in 1992 from NRDC, invention award for Dn Scanner Digitizer in 1994 and SICO sponsored National Academy of Science Award and Gold Medal for Image Processing Instrumentation in 1995. Published around 40 research papers in various national and internatioanl journals. Obtained five patents for his designs. He has designed and developed Large format 40” ×40”) film recorder to write images in RC color photographic paper. Guided more than hundred BE & ME students for their project work. His areas of interest are: image processing for medical applications, remote sensing, Digital printing for graphic arts and satellite data processing.

D S Jain

D S Jain, was born in Mandalagarh (Rajasthan) in 1953. He obtained his BE (horns) in 1975 and ME (Electronics) in 1977 from BITS Pilani. From 1977 to 1979 he was associated with CEERI Pilani on development of process control instruments for Sugar Industry. Since 1979 he is working at National Remote Sensing Agency as Head Imaging Division, Deputy Project Director, IRS-P5 Cartosat-1 and Project Director, ASDF. He has 2 patents and several publications in international journals to his credit. He is responsible for master films generation from remote sensing satellite data. He is involved in development of several technologies for remote sensing applications. He was principal co-ordinator for establishing IRS-IB data reception and processing systems. He is also responsible for systems augmentation for IRS-1C/1D and Cartosat-1 data processing systems using state-of-the-art workstations. He has received Best Important Substitution Invention and NRDC awards. He has been honoured at ‘Outstanding Young Indian’ by Indian Junior Chamber in 1991. He is a member of IEEE (USA) and ISRS.

G Vara Prasad

G Vara Prasad, was born in Jangalakandrika village, Nellore District, Andhra Pradesh in 1963. He obtained his AMIETE in 1986 and MTech (Advanced Electronics) on 1990 from JNT University, Hyderabad. Since 1991, he is working at National Remote Sensing Agency, Hyderabad as Hardware engineer on antennas, satellite data reception systems and digital film recorders. He was also Project Manager for IRS-1D (filming), Project Manager for ASDF-Filming and operations manager for IRS-1D (Filming). He has published a few papers in journals and guided several MTech/MSc/BTech students for successful completion of their project works. He got expertise to maintain digital film recorders.

N Prasada Rao

N Prasada Rao, was born in Nukalavari palem village in Krishna District of Andhra Pradesh in 1941. He obtained his Diploma in Electronics in 1965 from Indian Air Force. He worked in the Indian Air Force as supervisor in communications field such as HF, VHF and navigation equipment. Since 1977, he is with National Remote Sensing Agency, Hyderabad involving in development of electro-optical instruments for remote sensing applications such as drum scanner, densitometer and additive color viewer. Presently, he is responsible for film product generation at NRSA. He is also project manager for IRS-P4 (Filming).

S Rajendra Kumar

S Rajendra Kumar, was born in Kurnool District, Andhra Pradesh in 1954. He obtained his Diploma in Electronics and Communication in 1974mmedly joined Defence Electronics Research Laboratory, Hyderabad and worked in VHF/UHF receivers joined National Remote Sensing Agency as Hardware Engineer in 1979 and working on remote sensing instruments and digital film recorders development. Trained on Digital film recorders at Canada in 1984 and 1987. He was also recipient of NRDC award for design and development of small format digital film recorder. He has published a few papers in journals and guided several MTech, MSc, BTech, students for successful completion of their project works. Presently, he is Head, Hardware Development Section, looking after large format film recorder development and maintenance and also image analysis systems.