TABLE OF CONTENTS In this chapter the concept of the monobit receiver will be introduced. This technique can be considered as a digital channelized approach. The fast Fourier transform (FFT) is very simple and can be built on one chip. A simple frequency encoder is used after the FFT outputs to determine the number of input signals and their frequencies. The design of a candidate encoder will be presented. The encoder and the FFT can be built on one chip. The chip has been fabricated and the monobit receiver concept has been validated successfully in the laboratory.
The monobit receiver concept is inspired by commercial Global Positioning System (GPS) receiver designs. Usually, the analog-to-digital converter (ADC) in a commercial GPS receiver has only 1 or 2 bits, and the GPS signal is more complicated than a pulsed radio frequency (RF). This idea is adopted in wideband receiver applications and the name monobit receiver is used. This technique can be used to reduce to a minimum the hardware required for a given receiver function, with only a slight reduction in performance.
Because the ADC used in the monobit receiver has very few bits, the system is basically nonlinear. A nonlinear system is difficult to analyze theoretically. Thus, in designing the receiver one uses data collected from a data collection system. The collected data are processed in a computer to evaluate the performance. In order to determine the number of input signals, thresholds must be incorporated in the chip design. These threshold values...
