Figure shows the block diagram of a beterodyne spectrum

Figure shows the block diagram of a beterodyne spectrum analyzer. It consists of a variable-frequency oscillator, multiplier, band-pass filter, and root mean square (RMS) meter. The oscillator has amplitude A and square over the range A?0 to A?0 + W, where A?0 is the mid-band frequency of the filter and W is the signal bandwidth. Assume that A?0 = 2W, the filter bandwidth ?A? is small compared with A?0 and that the pass-band magnitude response of the filter is one. Determine the value of the RMS meter output for a low-pass input signal g (t).