Instantaneously companding baseband SC low-pass filter and ADC for 802.1 la/g WLAN receiver

To handle the 12dB peak-to-average-power ratio (PAPR) of OFDM signals in a 802.11a/g WLAN receiver baseband, an instantaneously companding system consisting of a 5-order low pass SC filter and a 10-bit pipeline ADC is presented. The filter cut-off and clock frequencies are 10MHz and 100MHz respectively and the ADC sampling frequency is 25MS/s. The filter provides the compressed output directly to the ADC and the signal expansion is done in the digital domain, which eliminates the need of an analog expansion amplifier. For a 12dB increase in dynamic range, it is estimated that the filter consumes 3.7 times less power than a conventional filter while the dynamic range required from the ADC is reduced by 12dB due to companding by a factor of 4. The filter and the ADC are designed to be implemented in a 1.2V, IBM 0.13μm CMOS process and the total power consumption is 75mW.