It was just over a hundred years ago that Professor J. Chandra Bose of Calcutta made the first pyramidal microwave horn and reported his findings [1] in "Electrical Engineering". The following year, he lectured to the Royal Institution and demonstrated his millimetre wave spectrometer. This operated up to 60 GHz - a tremendous achievement for 1897! He described his microwave horn as a "collecting funnel" and his original diagram shows a wide flare pyramidal horn.

For some decades, little work was carried out on microwave horns, largely due to a greater interest in low frequency antennas for transmission. Then in the 1930s came the first analysis of the horn, and, slowly at first, more work followed, and the horn came increasingly into use. Modern computers have led to a greater understanding of the way in which horns function, and to more efficient designs.

Curiously, the exact equations for the gain of wide angle horns like Bose's "collecting funnel" were solved only recently, by Dr Dennis Hawkins [2, 3] at Q-par Angus Ltd.

Q-par Angus owes a great deal to Bose and his horn. The company can safely claim to be the leaders in the UK in the design, analysis and manufacture of horn antennas. The wide variety of applications has led to an equal variety of shapes and sizes. One of the largest horns manufactured by the company is shown above. This is a broad band horn designed for EMC testing in the range 100 MHz to 1 GHz: it measures 2 metres long and has an aperture of 1.5 x 2 metres. In contrast, Q-par Angus has also made horns working at 200 GHz with an 8 mm aperture.

Most horn antennas lie somewhere between these two extremes. Standard gain horns are usually operated from about 1 GHz to 60 GHz, but Q-par Angus have no reservations about extending the range in either direction.

There is many a good tune played on an old horn, and the variety continues to extend.

[1] Bose, J. C. : "A complete apparatus for the study of the properties of electric waves",
Electrical Engineering, London, October 2nd, 1896.

[2] Hawkins, D.C. :"Improvements to Synthesis of Waveguide Horns",
Electron.Lett., 1992, 28, (9), pp 879-881.

[3] Hawkins, D.C. and Thompson, F. :"Modifications to the Theory of Waveguide Horns",
Proc. IEE - H, Vol.140, No.5, October, 1993.