Can anyone tel what is function of RC in the above figure.
Sorry for the delayed response. Let's say for example we have a simple passive RC bandpass filter, the cutoff frequency is dependent on the values of the capacitor and the resistor. The cutoff frequency of the filter follows the formula:
fcutoff = 1/(2*pi*R*C)
You can try this tutorial (analog filters) for more information on filter design. Also, you can visit FILTER WIZARD | Analog Devices to help you on your future filter designs.