REP017: Dual-band three-mode IC suitable for both CDMA and AMPS with an intermediate frequency of 183MHz

Rapid engineering prototypes are actual circuits built and tested by Maxim application engineers in our labs. They are the starting point for new RF engineering designs. They are not intended as tools for assessment testing.

Purpose: Use dual-band three-mode CDMA front-end IC in a receiver that requires both a digital communication channel with a frequency of 183.6MHz and an AMPS analog channel IF.

The emergence of MAX2338 provides convenience for dual-band use of a single IF. The IP2 index and other related parameters of the digital communication channel mixer provide sufficient margin to meet the 1/2 IF and other interference of CDMA mobile phones. In addition, the analog FM mixer can easily operate at 183.6IF, so (by using the internal LO (local oscillator) divider) only one RF VCO (voltage controlled oscillator) is needed in the transceiver design. The MAX2338 has been successfully tested and used in such applications, that is, in the front-end design of mobile phones with both CDMA systems and AMPS systems, a 183.6MHz IF filter suitable for CDMA and a narrowband suitable for AMPS is used . The performance specifications in the data sheet are fully met.

The MAX2338 low-noise amplifier (LNA) and mixer is designed specifically for dual-band CDMA mobile phones, but it can also be used in dual-band TDMA, GSM, EDGE, or WCDMA systems. The MAX2338 provides a divide-by-2 function in the PCS band LO input channel, specifying a single VCO in the PCS band. The buffered LO output allows the driven transmit channel to be directly upconverted without using an external LO buffer. For LNAs and mixers, the MAX2338 differs from its replacements ( MAX2320 and MAX2323 ) by its lower noise curve characteristics and higher IIP3 performance. Likewise, its package (28-QFN) is smaller.

Block diagram of a receiver-path application
Schematic of the MAX2338 evaluation kit (PDF, 60kB)
Bill of materials, part 1
Bill of materials, part 2