Real-Time Hardware/Software Approach to Phase Noise Emulation

Phase noise is a complex and ubiquitous source of BER degradation for all communication systems. Tight interaction between the phase noise and implementation of receiver tracking loops limits the fidelity of analytical derivations. The long timescales associated with phase noise make software simulations extremely time consuming. Both of these difficulties are exacerbated in systems that employ forward error correction. This paper reports on the development of a hardware-assisted phase noise emulator. This emulator allows injection of wideband, completely programmable phase noise into a real-time system. The phase noise samples are computed entirely in software and then passed to a hardware engine. The hardware engine digitizes a low-IF signal, combines it with the computed phase noise, and re-generates an analog low-IF output. The system described in this paper supports signals up to 30 MHz wide, centered at a 70 MHz IF. The phase noise characteristics can be modeled accurately up to 10 MHz using a simple model and up to 1 MHz for a more complex model.