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Maxim's lowest noise 3G WCDMA base-station transmitters
July 26, 2005
Maxim Integrated Products introduces the MAX2022, the world's lowest noise, highest linearity, 2GHz, Zero-IF I/Q modulator designed specifically for wireless infrastructure applications. The MAX2022 is the latest addition to Maxim's growing base-station portfolio, which includes complete RF-to-bits solutions for virtually every wireless standard.
Ideally suited for 2.5G/3G base-station transceivers, the MAX2022 delivers over 23dBm and 51dBm of OIP3 and OIP2 performance, respectively, while maintaining an incredibly low output-noise density of less than -173.2dBm/Hz. Uncalibrated sideband suppression is rated at 45.7dBc, and the unnulled carrier feedthrough is limited to -40.4dBm. The MAX2022 also delivers up to -20.8dBm of output power, with an exceptionally low -0.005dB/degrees Celsius variation over -40 degrees Celsius to +85 degrees Celsius. Output power flatness is also impressive at 0.32dB. Together, these features enable true four-carrier WCDMA/UMTS direct conversion architectures, with -27dBm/carrier power and 67dB adjacent channel leakage ratio (ACLR) performance.
The MAX2022 is ideal for 1500MHz to 2500MHz WCDMA, DCS/PCS/EDGE, cdma2000, and WiMAX(s) wireless infrastructure applications where high linearity and low noise figure are critical for maintaining high levels of ACLR and Error Vector Magnitude (EVM) transmitter performance. In the case of WCDMA, the MAX2022 can deliver peak ACLR levels up to 71dB, 68dB, and 67dB for 1-carrier, 2-carrier, and 4-carrier operation, respectively.
The MAX2022 also yields a 3dB advantage in OP1dB linearity over the closest competing solution, and it offers an impressive 15dB advantage in output noise performance. It also eliminates the need for an expensive transmit mask filter immediately following the modulator. The MAX2022 is the only 4-carrier modulator on the market to do this without the use of supplemental baseband I/Q buffer amplifiers. The elimination of this transmit filter also simplifies the design of digital predistortion architectures because the system's bandwidth will not be limited by the filter's mask.
As a fully integrated SiGe ZIF modulator/demodulator, the MAX2022 integrates two state-of-the-art matched mixer cores for modulating in-phase and quadrature signals, three LO mixer amplifier drivers, and an LO quadrature splitter. On-chip baluns are also integrated to allow for single-ended RF and LO connections. As an added feature, the baseband inputs have been matched to allow direct interfacing to the transmit DAC, thereby eliminating the need for costly I/Q buffer amplifiers. Through all this integration, the total board space used by the upconverting modulator is reduced by a factor of 4x; the discrete part count is reduced by 60%. More importantly, the MAX2022's ZIF architecture eliminates a complete IF transmit stage, thus resulting in further reductions in board size and lineup cost. Four IF amplifiers, two upconversion mixers, two LO buffer amplifiers, two filters, and a complete synthesizer (VCO + PLL) are effectively replaced by this single ZIF modulator.
As part of its commitment to providing RF-to-bits solutions for the wireless infrastructure market, Maxim is now offering a complete UMTS/WCDMA transmitter reference design that capitalizes on the breakthrough technology provided by the MAX2022. Figure 4 (below) illustrates Maxim's transmitter solution which utilizes the recently introduced MAX5895 interpolating DAC, the MAX2057 RF VGA, the MAX2015 RF power detector, and the MAX2016 gain and VSWR detector. Actual measurements from the reference design.
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