| 摘要 |
A multimode communications device includes an RF section and an analog-to-digital converter (ADC) located in a receive path between the RF section and a baseband section. The ADC includes a programmable signal converter core operable to perform ADC functions on a received RF signal in accordance with different types of mobile communication device operational modes, and further includes a multimode control function for programming the signal converter core as a function of a currently selected operational mode. The programmable signal converter core preferably includes a sigma-delta modulator, and a signal analysis function is provided for analyzing the received RF signal for dynamically programming the converter core to adapt to temporary signal and interference conditions by increasing or decreasing the performance of the signal converter. The signal analysis function may be embodied as a decimation filter having an input coupled to an output of the modulator, or by a digital signal processor forming a portion of a baseband section. The programmable signal converter core may be programmed to change the number of bits used by the sigma-delta modulator and/or a loop filter transfer function and loop filter coefficients, or a number of quantizer levels, or decimator coefficients and word width. The sigma-delta modulator bias currents may also be changed, as may a selected type of dynamic element matching function, each as a function of the selected mode. Other operational criteria that can be changed include the sigma-delta modulator oversampling ratio and/or a change from a switched capacitor to a resistor-capacitor circuit technique, or vice versa. |
