REP008: Dual-band front-end IC operating at universal 85MHz low IF for CDMA, PCS and AMPS

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.

Objective: Develop application circuit and test this dual-band tri-mode front-end IC using 85MHz IF in PCS, Cellular CDMA and Cellular AMPS.

The MAX2323 provides a single-channel output for cellular and PCS digital communications mixers. In this application circuit, the goal is to evaluate performance using a general-purpose low IF of 85.38MHz. The high IP2 performance of the PCS mixer and the rejection of the RF filter band edges provide acceptable, although not perfect, 1/2IF image rejection. This design is a circuit prototype used to evaluate the extreme data of MAX2320 . Even when using low IF in the PCS band, the results are surprisingly good.

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. The difference from its previous generation (MAX2320) is the addition of a third "mid-gain" state to the cellular band LNA, which improves sensitivity and conversion hysteresis margin. The MAX2323 uses a smaller package (28-QFN) and has a higher third-order input intercept point.

Schematic of the MAX2323 evaluation kit (PDF, 61kB)
Bill of materials, part 1
Bill of materials, part 2
Bill of materials, part 3