10.1 INTRODUCTION

The first airborne radar systems were developed during World War II, starting with the British AI (airborne intercept) VHF (200 MHz) radar used in their Beaufighter and Blenheim twin engine fighter/bomber [1, 2]. Airborne radar designs evolved quickly into three distinct categories, airborne early warning (AEW), fighter intercept, and bombing/navigation. Later developments included airborne radars for surface surveillance and weather avoidance.

The need for supporting systems evolved at the same time radars were developed. The first support system needed was electronic communications. This was followed by the need to determine whether the object detected was friendly, neutral, or the enemy, resulting in identification, friend or foe (IFF). The need for command and control of intercepting fighter aircraft led to the development of better navigation systems. Then, all fighters being used for attack knew where the target was located because they had basically the same reference grid, or had achieved "grid lock." Electronic intercept systems capable of detecting and identifying electromagnetic emissions from aircraft were added to provide an independent means of target identification and location. Infrared and television systems have also been used to provide positive means of target identification.

A brief history of the development of AEW is given in Chapter 1, and Chapter 3 includes photographs of a number of the early AEW aircraft. Summaries of the characteristics of AEW radars are given by Morchin [3] and Morchin and Johnston [4].

The first AEW radar employed...