Question: A dual-band receiver employing a Weaver architecture is shown in Fig. The first LO frequency is chosen so as to create high-side injection for the 2.4-GHz band and low-side injection for the 5.2-GHz band. (The receiver operates only in one band at a given time.) Neglect the noise and nonlinearity of the receiver itself and assume an SNR of 20 dB is required for the signal to be detected properly. The Weaver architecture provides an image rejection ratio of 45 dB.
(a) Suppose the receiver must detect a 285-dBm signal in the 2.4-GHz mode while receiving at the same antenna a 210-dBm 5.2-GHz component as well. Determine the amount of rejection required of BPF1 at 5.2 GHz.
(b) Suppose the receiver operates in the 5.2-GHz band but it also picks up a strong component at 7.2 GHz. It is possible for this component to be mixed with the third harmonics of LO1 and LO2 and appear in the baseband. Does the Weaver architecture prohibit this phenomenon? Explain in detail.
