Antenna having elements with programmable digitally generated time delays

Abstract

An array antenna (12) in which dependent programmable and digitally generated time delays are imposed on signals passing through each antenna element (14) is disclosed. A beam steering computer (32) determines data values corresponding to delays needed at each element to form a desired beam angle. These data values are written into digital element signal processors (DESPs) (40) which are associated with each element in one-to-one correspondence. Each DESP (40) includes a waveform generator (30), which produces digitized samples synchronously with a reference clock signal. A stream of the digitized samples passes through and is delayed in a highly precise delay generator (54) before being converted to analog in a D/A converter (60). The analog signal is modulated (62), amplified (66), and then radiated at the associated element (14). Received signals are amplified (70), demodulated (72), converted to digital in an A/D converter (74), and then passed through the same delay generator (54). They are then re-converted to analog (60), modulated (62) back to RF, and combined (50) with other delayed RF signals. The delay generator (50) includes a register file (106) which receives a digitized waveform. A latch (86) receives delay data. The delay data programs a counter (80, 82) to delay the waveform for a variable, integral number of reference clock cycles. The delay data further programs a delay line (88) to impose a further fractional portion of a reference cycle delay on the waveform.