Answer 5.10

The carrier recovery circuit uses the squaring device to double the frequency of the incoming signal hence forcing the 0o and 180o phase modulation to modulo 360o. The squared output is thus at twice the input carrier frequency including any frequency error in the system such as Doppler shift. For this case, the output frequency would thus be 2 x (1 MHz + 70 Hz) or 2000140 Hz