In the digital synthesis of wideband periodic signals using an Arbitrary Waveform Generator (AWG), the frequency resolution and spectral complexity of the synthesized signals are commonly limited by the memory capacity and clock frequency of the AWG. This paper proposes a novel sequential addressing scheme and then presents several sequences to improve the frequency resolution of the synthesized periodic signals without changing their spectral envelopes and basic time-domain characteristics under the condition of a fixed memory capacity and a fixed clock frequency. The main idea of the scheme is using the address generator in an AWG to program and produce addresses to read fixed waveform data in variable order, and thus to generate waveforms of various periods and profiles. The scheme is applied in simulating signal scenarios for military communication countermeasure experiments, and achieves high performance.

This paper proposes a novel iterative algorithm for optimal design of non-frequency-selective Finite Impulse Response (FIR) digital filters based on the windowing method. Different from the traditional optimization concept of adjusting the window or the filter order in the windowing design of an FIR digital filter, the key idea of the algorithm is minimizing the approximation error by successively modifying the design result through an iterative procedure under the condition of a fixed window length. In the iterative procedure, the known deviation of the designed frequency response in each iteration from the ideal frequency response is used as a reference for the next iteration. Because the approximation error can be specified variably, the algorithm is applicable for the design of FIR digital filters with different technical requirements in the frequency domain. A design example is employed to illustrate the efficiency of the algorithm.