资 源 简 介
The AD9267 is a dual conTInuous TIme （CT） sigma-delta （Σ-Δ） modulator with −88 dBc of dynamic range over 10 MHz real or 20 MHz complex bandwidth. The combinaTIon of high dynamic range， wide bandwidth， and characterisTIcs unique to the continuous time Σ-Δ modulator architecture makes the AD9267 an ideal solution for wireless communication systems. The AD9267 has a resistive input impedance that significantly relaxes the requirements of the driver amplifier. In addition， a 32× oversampled fifth-order continuous time loop filter attenuates out-of-band signals and aliases， reducing the need for external filters at the input. The low noise figure of 15 dB relaxes the linearity requirements of the front-end signal chain components， and the high dynamic range reduces the need for an automatic gain control （AGC） loop. A differential input clock controls all internal conversion cycles. An external clock input or the integrated integer-N PLL provides the 640 MHz internal clock needed for the oversampled continuous time Σ-Δ modulator. The digital output data is presented as 4-bit， LVDS at 640 MSPS in twos complement format. A data clock output （DCO） is provided to ensure proper latch timing with receiving logic. Additional digital signal processing may be required on the 4-bit modulator output to remove the out-of-band noise and to reduce the sample rate.
