Example 4.6. A dual-mode receiver is designed for both 802.11g and 802.11a.Can this receiver operate with a single LO? Solution Figure 4.12(a)depicts the two bands.We choose the LO frequency halfway between the two so that a single LO covers the 11g band by high-side injection and the 11a band by low-side injection [Fig.4.12(b)].This greatly simplifies the design of the system but makes each band the image of the other.For example,if the receiver is in the 11a mode while an 11g transmitter operates in close proximity,the reception may be heavily corrupted.Note that also the IF in this case is quite high,an issue revisited later. Figure 4.12.(a)11g and 11a bands,(b)choice of fLo. 11g Band 11a Band 和市”中中、 2.40 2.48 5.15 5.355.7255.825 (GHz) (a) fLo f (b)