Advanced digital antenna module

Abstract

An Advanced Digital Antenna Module (ADAM) for receiving and exciting electromagnetic signals. The ADAM ASIC integrates a complete receiver/exciter function on a monolithic SiGe device, enabling direct digital-to-RF (Radio Frequency) and RF-to-digital transformations. The invention includes an improved analog-to-digital converter (ADC) ( ) with a novel active offset method for comparators. The novel ADC architecture ( ) includes a first circuit ( ) for receiving an input signal; a second circuit ( ) for setting a predetermined number of thresholds using a predetermined number of preamplifiers ( ) with weighted unit current sources ( ) in each of the preamplifier outputs; and a third circuit ( ) for comparing the input to the thresholds. In the preferred embodiment, the ADC ( ) includes trimmable current sources ( ). The ADC ( ) of the present invention also includes an improved comparator circuit ( ). The novel comparator ( ) includes split load resistors, pairs R (active mode) and R and pairs R (active mode) and R , to increase the acquisition time and reduce the regeneration time constant, emitter follower buffers Q and Q on the latch pair transistors Q and Q to reduce the capacitive loading on the regeneration node, and cascode transistors Q and Q coupled to the load resistors to eliminate the output loading effects from the regeneration node. In the preferred embodiment, the invention also includes a novel DDS/DAC architecture ( ) with digitally trimmed unary currents and a novel sine lookup and decoder design which overcomes the conventional dynamic range limitations at high conversion rates.