A dual-mode cellular phone is designed to operate with either cellular phone service in the 900-MHz band or PCS in the 1,900-MHz band. The phone uses a superheterodyne receiver with a 500-MHz IF for both modes.
(a) Calculate the LO frequency and the image frequency for high-side injection when the phone receives an 880-MHz signal.
(b) Calculate the LO frequency and the image frequency for low-side injection when the phone receives a 1,960-MHz PCS signal.
(c) Discuss the advantage of using a 500-MHz IF for this dual-mode phone.
