Baseband receiver including dual port DAC

DETAILED DESCRIPTION The need remaining in the prior art is addressed by the present invention, which relates to a receiver arrangement responsive to an incoming analog signal and forming a digital representation thereof and, more particularly, to a baseband receiver including a dual-port digital-to-analog (DAC) converter for simultaneous use in both the I- and Q-rails of the receiver.
In accordance with a preferred embodiment of the present invention, the baseband receiver maintains separate I and Q signal paths, a successive approximation analog-to-digital converter (ADC) technique to process the received analog components.
The successive approximation ADC in the receiver of the present invention comprises separate sample-and-hold circuits, comparators and successive approximation registers (SARs) on each signal path, as in the prior art.
In a departure from the prior art, a single dual-port digital-to-analog converter (DAC) is used to simultaneously process both the received I and Q signal components.
More particularly, the outputs from both SARs are applied as separate inputs to the dual-port DAC, where the separate outputs from the dual-port DAC are fed back as "error signal" inputs to the respective comparators along the I and q signal paths.
The dual-port DAC includes two separate sets of switches across a precision resistor ladder so that the same resistor ladder is used to simultaneously process the pair of input digital signals and generate as an output a pair of analog signals.
Advantageously, the dual-port DAC provides a significant size saving over using a separate pair of DACs (one for each signal path), since a dual-port DAC is approximately the same size as a conventional DAC.
Further, since the dual-port DAC includes a single resistor ladder and reference potential source, it consumes approximately the same amount of power as a conventional DAC.
A savings of approximately 50% in both size and power is thus achieved by using a dual-port DAC in a baseband receiver in accordance with the present invention