New Tx Chipset Enables the Industry's Highest Linearity, Lowest Noise, Direct-Conversion Transmitter for GSM/EDGE Base Stations
SUNNYVALE, CA—August 30, 2006—Maxim Integrated Products (NASDAQ: MXIM) introduces a new high-performance SiGe I/Q modulator and digital RF variable-gain amplifier (VGA) chipset designed specifically for GSM/EDGE base-station transmitter applications. Together, the MAX2021/MAX2023 I/Q modulators and the MAX2058/MAX2059 VGAs deliver the lowest noise and highest levels of linearity of any competing direct-conversion (zero-IF) transmitter solution.
Overview
The pressure of reducing costs while maintaining or even improving performance continues for wireless infrastructure applications. Designers are constantly searching for more cost-effective solutions that simultaneously reduce component count, board size, and design complexity. For GSM/EDGE base transceiver system (BTS) transmitters, the most cost-effective solution utilizes a direct baseband-to-RF (i.e., zero-IF) architecture. However, due to the base station's demanding spectral mask requirements, zero-IF architectures have historically been limited to low-performance handset applications.
With the introduction of the MAX2021/MAX2023 and MAX2058/MAX2059 series of high-performance I/Q modulators and RF digital VGAs, the historical performance barrier for GSM zero-IF architectures has finally been breached. Together with the Company's MAX5873 dual DAC and MAX4395 quad amplifier, these new components form the industry's first and only digital baseband-to-RF VGA chipset that meets all spectral-mask and noise-floor requirements for single-carrier GSM850/900 and DCS1800/PCS1900 EDGE base stations.
When cascaded together, the complete chipset delivers +15dBm of output power, +32dBm of OIP3, and an exceptionally low output-noise level of < -156dBc/Hz (at 6MHz offset). LO leakage (nulled) is also rated at < -40dBc over the extended -40°C to +85°C temperature range. Complete lineup gain control is provided by the SPI™-controlled RF digital VGAs, as the two on-chip attenuators support 12dB of static control, 30dB of dynamic control, and > 10dB of lineup compensation.
Unprecedented Modulator Performance
The chipset's noise and linearity performance is driven primarily by the new MAX2021/MAX2023 zero-IF I/Q modulators. Both modulators boast breakthrough output-noise-density levels of -174dBm/Hz that match the theoretical thermal limit. These outstanding levels represent an astounding 10dB improvement over prior state-of-the-art modulators/demodulators. In addition, the MAX2021/MAX2023 yield OIP2, OIP3, and OP1dB levels of up to 57.9dBm/61dBm, 22.3dBm/23.5dBm, and 16.7dBm/14.3dBm, respectively. When you couple the noise performance with the raw P1dB values, the gross dynamic range is greater than 190.7dB/188.3dB-a 16.7dB/14.3dB performance leap over the closest competitors. These performance improvements directly enhance a BTS transmitter's spectral mask performance, and they allow the MAX2021/MAX2023 to exceed the strict spectral-mask requirements for GSM/EDGE BTS applications without the use of relatively expensive transmit mask filters (approximately $2.00 ($US) each, in volumes of 100k or more).
Novel Performance Capability from Highly Integrated RF Digital VGAs
The performance of the MAX2058/MAX2059 RF digital VGAs is
equally impressive. Each device yields 62dB/56dB of total adjustment range, +15dBm of output power, 32.3dBm/31.8dBm of OIP3, and a low spurious emission of -39.2dBc/-39.1dBc at a 200kHz offset, respectively. Even more noteworthy is their degree of integration. Besides the two digital attenuators and the two-stage RF amplifiers, these VGAs include an on-chip SPI decoder, two loopback switches, and a novel loopback mixer. When paired with the Company's MAX9491 synthesizer, the loopback mixer provides a convenient means for translating the transmit signal frequency up or down so that it can be fed directly into the receiver band. With this unique feature, the system can be configured for simultaneous, real-time diagnostic monitoring of both the transmitter and receiver chains.
Tx Chipset Significantly Reduces Components and Costs
As with all zero-IF transmit architectures, the Company's basic four-chip solution (See Figure 1) replaces a myriad of components. Compared to a traditional double upconversion transmit architecture (See Figure 2), this new solution replaces six lineup functions with a net cost savings of 65% (comparison made with replaced components). The Maxim chipset also only requires 26mm x 27mm of board space, resulting in a 50% space savings over a comparable circuit function. The cost and space savings, in turn, enable the next generation of GSM/EDGE designs in which transceiver price and density issues are paramount.
The MAX2021/MAX2023 and MAX2058/MAX2059 are available in 36-TQFN and 40-TQFN packages, respectively. Prices start at $4.98 (1000-up, FOB USA) for the MAX2021/MAX2023 and $7.96 (1000-up, FOB USA) for the MAX2058/MAX2059. For more information please visit: http://www.maxim-ic.com/gsmtx
Maxim Integrated Products is a leading international supplier of quality analog and mixed-signal products for applications that require real-world signal processing. For more information, go to http://www.maxim-ic.com, call us at 408-737-7600, or write to us at 120 San Gabriel Dr., Sunnyvale, CA 94086.
SPI is a trademark of Motorola, Inc.
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