5 HF Array-Processing Architecture

Previous chapters provided background material on the propagation of HF waves, common HF modulation techniques, and RF receiver architectural options. Now this book begins its primary topic, digital signal-processing techniques that exploit the performance enhancement opportunities afforded by amultielement antenna array. As indicated in chapter 1, such techniques provide significant advantages: 1) increased gain for greater receiver sensitivity, 2) enhanced cochannel interference-suppression capability, and 3) opportunities for the coherent combining of ionospheric propagation modes to suppress multimode garble and realize greater signal-to-noise ratio. These techniques will be detailed in the chapters to follow. This chapter outlines the overall signal-processing architecture, with hints as to how the multielement array provides the leverage for performance enhancements. Subsequent chapters will delve deeply into signal-processing algorithms that provide the desired performance enhancements and quantitatively assess these benefits.