A super heterodyne receiver operates in the frequency range of 58 MHz – 68 MHz. The intermediate frequency f_1F and local oscillator frequency f_L0 are chosen such that f_1F $$\leq$$ f_L0.It is required that the image frequencies fall outside the 58 MHz – 68 MHz band. The minimum required f_1F (in MHz) is ___________.

For a superheterodyne receiver, the intermediate frequency is 15 MHz and the local oscillator frequency is 3.5 GHz. If the frequency of the received signal is greater than the local oscillator frequency, then the image frequency (in MHz) is _________.

Consider the signal $$s\left(t\right)\;=\;m\left(t\right)\;\cos\left(2{\mathrm{πf}}_\mathrm c\mathrm t\right)\;+\widehat m\left(t\right)\;\sin\left(2\mathrm\pi\;{\mathrm f}_\mathrm c\mathrm t\right)$$ where $$\widehat m\left(t\right)\;$$ denotes the Hilbert transform of m(t) and the bandwidth of m(t) is very small compared to f_c. The signal s(t) is a