A 256MHz analog baseband chain is implemented in 1.2 V 65nm CMOS process. The baseband chain is composed of one fifth-order type I Chebyshev low-pass filter (LPF) and two variable gain amplifiers (VGA) for Ultra wideband (UWB) applications. The LPF is realized in Gm-C topology for channel selection. AC coupling capacitor and series divider resistors are used to prevent dc-offset and set a suitable common mode voltage. To achieve wide bandwidth and high linearity, an amplifier with enhanced source degeneration is employed in VGA design. Simulation results show that the baseband chain can realize a variable -3dB bandwidth range from 151MHz to 256 MHz with 15MHz step, and the gain range can vary from 20dB to 38dB with 3 dB step. For the overall chain the noise figure (NF) is 11dB at 38dB gain, while the input-referred noise (IRN) is 2.5 nV/v'Hz.