REP021: Front-end devices for 2.5GHz Globalstar and IS-95

Rapid engineering prototypes are actual circuits that Maxim application engineers build in the lab and conduct product testing. They are the starting point for new RF engineering designs. They are not intended to be used as assessment testing tools.

Goal: Develop an application circuit using this dual-band three-mode CDMA front-end IC. The 2.5GHz LEO satellite channel and IS-95 CDMA use PCS band downconverters and cellular band downconverters respectively.

The focus of this application design is to downconvert the 2.5GHz signal to 210MHz in the PCS band signal channel. IS-95 CDMA uses the cellular band signal channel. The LNA input and output matching are completely redesigned, and special attention must be paid to the optimization of the IF SAW filter matching at 210MHz. The MAX2323 has its own appeal, as this PCS LNA has two gain levels and excellent 2GHz noise figure, which is ideal for LEO satellite phone designs. In order to meet the frequency plan, the requirement of this design is to match both the FM analog mixer and the cellular/PCS digital mixer IF to 210MHz IF.

The MAX2323 low-noise amplifier (LNA) mixer is designed for dual-band CDMA cellular handsets. It can also be used in dual-band TDMA, GSM, EDGE, or WCDMA applications. Unlike its predecessor ( the MAX2320 ), it adds a third "mid-gain" state to cellular band LNAs, improving switching hysteresis margin. It has a higher third-order input intercept point in a smaller package (28-QFN).

Schematic of the MAX2323 evaluation kit  
Bill of materials, part 1
Bill of materials, part 2
LNA noise-figure test setup