REP012: Cellular LNA achieving +20dBm IIP3 in low-gain high-linearity mode

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 as assessment testing tools.

Goal: Experimentally tune this dual-band three-mode front-end IC to achieve the best linearity of cellular LNA in CDMA low-gain high-linearity mode.

The requirements of this design are to perform conventional tuning of the device to obtain the high linearity performance of +20dBm IIP3 in the low gain mode of the cellular LNA, while matching the mixer output port to 85.38 on both analog and digital (cellular/PCS) modes. MHz. Note that this is an experimental one-off "performance limit" design, and it is difficult to achieve this performance under normal circumstances. Careful adjustments to the LNA's bias resistors are made along with the IF output matching circuit. The LNA input matching should also be modified, but care should be taken not to disturb the noise figure at mid-gain and high-gain. The output matching of the LNA does not need to be modified. This design demonstrates that extremely versatile applications can be developed using these silicon germanium front-end ICs.

The MAX2323 low-noise amplifier (LNA) and mixer is designed for dual-band CDMA cellular handsets, but it can also be used in dual-band TDMA, GSM, EDGE, or WCDMA applications. The difference from its predecessor ( MAX2320 ) is that it adds a third "medium gain" state to this cellular band LNA, which allows for improved switching hysteresis margin. It also uses a smaller package (28-QFN) and provides a higher third-order input intercept point.

Schematic of the MAX2323 evaluation kit (PDF, 60kB)
Bill of materials, part 1
Bill of materials, part 2
Bill of materials, part 3
Cellular LNA/mixer IIP3 measurement setup
Cellular LNA/mixer noise-figure measurement setup
PCS LNA/mixer IIP3 measurement setup
PCS LNA/mixer noise-figure measurement setup