General Description
Digital Precorrection (Predistortion) system used to compensate for the non-linearity of an RF power amplifier. Compensates for both Gain and Phase. The design may be used in open-loop configuration or in closed-loop configuration as part of an adaptive precorrection system. Complex LUT stores the inverse (AM-AM) and (AM-PM) characteristics of the Amplifier. Optional choice of programming interfaces (I2C, SPI or UART) may be provided as an extra.
Key Design Features
– Corrects the PA Gain and Phase responses
– 16-bit signed (I/Q) inputs and outputs
– 256×32-bit LUT to store inverse PA characteristic
– LUT initialized at compile time or modified in-circuit
– Suitable for open or closed-loop operation
– Operation at Baseband or IF frequencies
– Typical improvements of up to 20 dBs in the ‘shoulders’
– Pipeline latency of only 8 clock cycles
– FPGA sample rates of 200 MHz+
Applications
– Linearization for Mobile base-stations
– Linearization for Digital-TV Broadcasting
– Precorrection of any type of digitally modulated
signal where the signal envelope varies and
therefore the instantaneous input power
e.g. UMTS, WCDMA, OFDM etc.
