Introduction:
The frequency sampling method is a technique used for the realization of Finite Impulse Response (FIR) filters. It involves sampling the desired frequency response of the filter and then finding the corresponding impulse response using the inverse discrete Fourier transform (IDFT). The resulting impulse response is then used to implement the FIR filter.

Frequency Sampling Method:
The frequency sampling method involves the following steps:
1. Determine the desired frequency response of the FIR filter.
2. Sample the desired frequency response at equally spaced frequencies.
3. Perform the IDFT on the sampled frequency response to obtain the corresponding impulse response.
4. Implement the FIR filter using the obtained impulse response.

Cascade of Filters:
When applying the frequency sampling method, the realization of the FIR filter can be viewed as a cascade of two filters. This can be understood by considering the steps involved in the frequency sampling method.

First Filter:
The first filter in the cascade is responsible for generating the sampled frequency response. It takes the desired frequency response as input and produces the sampled frequency response. This filter essentially performs the sampling operation by assigning the values of the desired frequency response at equally spaced frequencies.

Second Filter:
The second filter in the cascade is responsible for converting the sampled frequency response into the impulse response. It takes the sampled frequency response as input and performs the IDFT to obtain the corresponding impulse response.

Overall Cascade:
The output of the first filter (sampled frequency response) serves as the input to the second filter (IDFT operation). The output of the second filter (impulse response) represents the final realization of the FIR filter. Therefore, the realization of the FIR filter by frequency sampling can be viewed as a cascade of two filters.

Conclusion:
In conclusion, the realization of a FIR filter by frequency sampling can be viewed as a cascade of two filters. The first filter generates the sampled frequency response, and the second filter converts the sampled frequency response into the impulse response. This cascade of filters allows for the implementation of the desired FIR filter using the frequency sampling method.