Traditionally, digital filters were used for signal-to-noise ratio (SNR) improvement. This paper proposes a modified method to enhance and improve the digital filter performance. This method is based on the combination of coherent time averaging technique and digital filtering. This paper discusses the processing of single and multiple input sinusoidal signals with additive noise. By using this method in processing multiple signals, we can isolate the weak in-band signals from the strong out-of-band signals, which consequently improve the weak signal delectability. Cascaded digital filtering is applied using similar or different types of digital filters. A comparison study is provided for single stage and cascaded stages digital filters. It is shown that this modified method leads to better results in SNR improvement of weak signals than in the case of the direct application of digital filtering.