Samsung Employs Conexant Chip Set in CDMA Phones

Samsung Electronics has selected Conexant Systems' (formerly Rockwell Semiconductor Systems) Topaz RF subsystem chip set for its next-generation CDMA digital cellular phones. According to Samsung, this chip set has increased integration and reduced time during the design of the SCH-810 phone, which will be introduced in early 1999.

Conexant's Topaz chip set includes the RF250 receiver, the RF251 transmitter, and the RF252 CDMA baseband analog processor. These three devices, combined with a power amplifier, provide a complete transmit and receive solution for dual-band, dual-mode digital cellular/PCS phones.

The RF250 receiver incorporates all of the components required to implement the receiver front end and IF portions of a wireless phone. Housed in a 48-pin TQFP, the receiver is equipped with two low-noise amplifiers (LNAs)—one for 800 MHz operation and one for 1900 MHz operation. This device also integrates mixers, a single IF variable gain amplifier with a gain control range of over 90 dB, two VHF oscillators, and an in-phase/quadrature (I/Q) demodulator.

The RF251 transmitter includes an I/Q modulator, two IF voltage-controlled oscillators (VCOs), an IF automatic gain control amplifier with a 90 dB gain control range, two upconverters, two drivers for external power amplifiers, and a 48-pin TQFP package. To compensate for the gain variations of off-chip components, a 14-dB gain control is provided in the upconverter stage.

The RF252 baseband analog processor provides an interface between the RF section and the digital processing circuitry of the wireless handset. This device includes on-chip clock synthesis and processing circuits, general-purpose analog/digital conversion products for battery and signal monitoring, two fully programmable phase-locked-loop (PLL) synthesizers, and mode control logic for transmit, receive, sleep, and idle modes.