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Every mobile phone, Wi-Fi router and satellite dish depends on antennas that send and receive microwaves. In India, the research tradition behind that technology owes a great deal to Rajeshwari Chatterjee. She trained in mathematics, crossed into engineering when few women in India could, and spent nearly three decades building microwave research at the Indian Institute of Science (IISc). This post covers her path, explains one of her research topics with a worked example from Class 12 physics, and ends with lessons for students.
Who was Rajeshwari Chatterjee?
The IISc Department of Electrical Communication Engineering heritage page describes her as the first woman engineer from Karnataka. She was born on 24 January 1922 in Nanjangud, Karnataka, into a family that valued women's education; she attended the Special English School founded by her grandmother, the social reformer Kamalamma Dasappa.
She took BSc (Hons) and MSc degrees in mathematics and physics at Central College, Bangalore, graduating with first rank from Mysore University in 1942. In 1943 she joined IISc as a research student in the Electrical Technology Department, when C. V. Raman was the institute's director. After independence she won a government scholarship to study in the United States, and completed a master's degree in electrical engineering and then a PhD in 1953 at the University of Michigan, under Professor William Gould Dow.
What did she build at IISc?
She returned to join the Department of Electrical Communication Engineering at IISc, where the heritage page lists her service from 17 August 1953 to 31 July 1982. Together with her husband, Sisir Kumar Chatterjee, she established India's first microwave research laboratory. Over her career she supervised 20 PhD students, published more than 100 research papers and wrote seven technical books on microwave engineering, antenna theory and dielectric-loaded antennas. She chaired the department from 1979 to 1981.
Her early papers show the lab's range. In 1960 the couple published Some Investigations at Microwave Frequencies in what is now the IETE Journal of Research. In 1968 she published Theory of dielectric rod aerials, and in the 1970s she was publishing antenna designs with her students, such as a dielectric hemisphere on a cone antenna with T. S. Vedavathy.
What is a dielectric rod antenna?
Most antennas students picture are metal wires or dishes. A dielectric rod antenna is a rod of insulating material, such as a plastic, that guides a microwave along its length and launches it from the end as a narrow beam. Its behaviour depends on how the wave travels inside the material, which is where Class 12 electromagnetic waves come in. Our guide to electromagnetic waves and the spectrum covers the basics.
Worked example: how long is a microwave?
Use c = fλ, with c = 3.0 × 10⁸ m/s in a vacuum.
At 3 GHz. λ = c/f = (3.0 × 10⁸)/(3.0 × 10⁹) = 0.10 m = 10 cm.
At 10 GHz. λ = (3.0 × 10⁸)/(1.0 × 10¹⁰) = 0.030 m = 3 cm.
A half-wave antenna at 3 GHz. Its length is λ/2 = 5 cm.
Inside an insulator. In a non-magnetic material with relative permittivity εr, the speed of the wave is v = c/√εr, while the frequency stays the same. So the wavelength shrinks by the same factor. For εr = 4, √εr = 2, and a 3 GHz wave has λ = 10 cm / 2 = 5 cm inside the material.
Step 4 is the key idea behind dielectric antennas: the material changes how the wave travels, and that changes the beam the antenna produces.
Common mistakes. Writing 1 GHz as 10⁶ Hz instead of 10⁹ Hz gives an answer a thousand times too large. And forgetting the square root: for εr = 4 the speed halves, it does not fall to a quarter. Our profile of Heinrich Hertz and radio waves shows where this physics began.
How was she recognised?
The IISc page lists her awards: the Mummadi Krishnaraja Wodeyar Award for first rank in BSc, the Mountbatten Prize of the Institute of Electrical and Radio Engineering (UK), the J. C. Bose Memorial Prize of the Institution of Engineers, and the Ramlal Wadhwa Award of the Institute of Electronics and Telecommunication Engineers. In 2017 the Ministry of Women and Child Development named her, after her death, among India's "First Women Achievers". After retiring in 1982 she worked against gender discrimination with the Indian Association for Women's Studies. She died on 3 September 2010.
What can a student take from how she worked?
Mathematics travels. Her degrees were in mathematics and physics, and that base let her move into engineering research. The calculus and vectors you study now are what electromagnetic theory is built on.
Build what is missing. There was no microwave laboratory in India, so she and her husband made one, and then designed courses to train others.
Train people, not just devices. Twenty PhD students carried her methods into labs and industry. Explaining your work to others is part of doing it.
Ask how the wave behaves inside the material. Her research questions came straight from basic wave physics applied carefully to real objects.
If electromagnetic waves still feel abstract, the Fermi Simulation Lab has interactive simulations for ideas that are easier to see than read, so you can watch how wavelength changes with frequency.
Your next step: find the Wi-Fi frequency printed on your router, usually 2.4 or 5 GHz, and work out its wavelength and half-wave antenna length.
