TA0030

TA0030
 TA0030 RF2607, RF2609: Transmit and Receive AGC Amplifiers for CDMA Cellular/PCS Phones      
  Cellular and Personal Communication Services (PCS) phones that are based on Code Division Multiple Access (CDMA) need careful regulation of signal levels on both the forward and reverse channels. In the reverse channel (mobile phone to base station) a transmit automatic gain control (AGC) amplifier must carefully adjust the output power of the mobile so that it does not dominate the input spectrum at the base station. Each mobile's signal should arrive at the base station at the same power level; this helps ensure that capacity is maximized. In the forward channel (base station to mobile) a receive AGC amplifier adjusts to accommodate widely varying signal levels coming in from the base station. At a CDMA mobile phone antenna numerous signals sent from the cell base station are layered on a single frequency band and within this group of signals lays the desired data. All of these signals (desired and undesired) pass through a low noise amplifier front end and then through a downconverting mixer. Immediately following the mixer the waveforms pass through a CDMA intermediate frequency (IF) bandpass filter. All of the aforementioned signals are in-band and are not filtered. Because of this condition the receive AGC amplifier cannot simply limit. The strongest signal would be limited and compress all othe...