Method for in-system signal analysis is described. A programmable logic device is coupled within a signal communications system. A signal processing core is instantiated in programmable logic of the programmable logic device. At least one communication signal is provided to the programmable logic device, where the at least one communication signal has a first frequency. The at least one communication signal is sampled at a second frequency which is less than the first frequency to obtain samples thereof. The samples are converted from analog signals to digital signals. The digital signals are analyzed with at least in part the signal processing core.