Abstract: This reference design (RD) is for a dual-band, dual-mode CDMA front-end for Japanese cellular CDMA at 110MHz IF. The RD uses a low-noise amplifier (LNA) with mixer, the MAX2325, that is also useful for TDMA, GSM, and EDGE applications. Schematics and bill of materials are shown.
Rapid Engineering Prototypes are real circuits that Maxim application engineers have built and measured in our labs. They can provide a starting point for new RF designs. They are not available as evaluation kits.
Objective: To band-shift the RF matching from the U.S. to the Japanese cellular band, and to measure the performance of this CDMA dual-mode front-end IC.
The MAX2325 application circuit was changed from its standard BOM for the U.S. cellular-band LNA and mixer RF matching, to meet the Japanese cellular band with 110MHz IF. In addition, measurements were made to ensure compatibility with the end-customer's requirements. The MAX2325's performance was found to be fully compliant to the data sheet specifications at U.S. cellular frequencies.
A MAX2323 evaluation kit was used to evaluate the performance of the MAX2325, as it provides a superset of MAX2325 features.
The MAX2325 low-noise amplifier (LNA) plus mixer is designed for single-band CDMA cellular-phone handsets, but it can also be used in 800-900MHz-band TDMA, GSM, or EDGE applications. It differs from its predecessor (the MAX2324) by adding a third "mid-gain" state for the LNA that improves switchover hysteresis margin. The MAX2325 also comes in a smaller package (28-QFN) and offers increased third-order input intercept.
Tested Circuit 
