Maxim Integrated Products introduces a new high-performance SiGe I/Q modulator and digital RF variable gain amplifier (VGA) chipset designed for GSM/EDGE base station applications. The MAX2021/MAX2023 I/Q modulators and the MAX2058/MAX2059 VGA combination provide the lowest noise and highest linearity compared to other competitors' direct conversion (Zero IF) transmitter solutions.
In wireless infrastructure applications, there has been pressure to maintain or even improve performance while reducing costs. Designers are constantly looking for more cost-effective solutions while reducing component count, board size and design complexity. For transmitters in GSM/EDGE basic transceiver systems, the most cost-effective solution is to use a direct baseband to RF (ie zero intermediate frequency) architecture. However, given the stringent requirements of the base station for spectrum masks, the zero-IF architecture has historically been limited to lower performance handheld applications.
With the introduction of the MAX2021/MAX2023 and MAX2058/MAX2059 series of high-performance I/Q modulators and RF digital VGAs, the historic performance barrier of the GSM zero-IF architecture has been broken. Combined with Maxim's dual-channel DAC MAX5873 and quad-channel amplifier, the MAX4395, these devices form the industry's only groundbreaking digital baseband to RF VGA chipset for spectral masking and noise on single-carrier GSM850/900 and DCS1800/PCS1900 EDGE base stations. Background requirements.
By cascading the entire chipset, it delivers +15dBm output power, +32dBm OIP3, and <-156dBc/Hz ultra-low output noise (under 6MHz). The LO leakage (after zeroing) rating is < -40dBc over the -40°C to +85°C extended temperature range. The SPI-controlled RF digital VGA provides full gain control, plus two on-chip attenuators that provide 12dB of static control, 30dB of dynamic control and >10dB of compensation.
Excellent modulator performanceThe noise and linearity performance of the chipset is mainly brought about by the new zero-IF I/Q modulators MAX2021/MAX2023. Both modulators are proud of the output noise density, breaking through -174dBm/Hz, close to the theoretical thermal limit. These superior performances are further amazingly improved by 10dB compared to the highest level of modulator/demodulator previously. In addition, the OIP2, OIP3, and OP1dB levels of the MAX2021/MAX2023 are as high as 57.9dBm/61dBm, 22.3dBm/23.5dBm, and 16.7dBm/14.3dBm, respectively. After considering the noise performance and P1dB value, the total dynamic range exceeds 190.7dB/188.3dB, which is beyond the nearest competitor of 16.7dB/14.3dB. These performance improvements directly enhance the spectral mask performance of the BTS transmitter, allowing the MAX2021/MAX2023 to exceed the stringent spectral template performance requirements of GSM/EDGE BTS applications without the need for relatively expensive transmit stencil filters (above 100k) Each is approximately $2.00 ($US)).
Highly integrated RF digital VGA delivers exceptional performanceThe performance of the MAX2058/MAX2059 RF digital VGAs is equally impressive. Their total adjustment range is 62dB/56dB, the output power is +15dBm, OIP3 is 32.3dBm/31.8dBm, and the spurious emission power is low at 200kHz. To -39.2dBc/-39.1dBc. More interesting is its integration. In addition to including two digital attenuators and two-stage RF amplifiers, these VGAs include an on-chip SPI decoder, two loopback switches, and a sophisticated loopback mixer. When used with Maxim's MAX9491 synthesizer, the loopback mixer provides a convenient way to increase or decrease the frequency of the transmitted signal, so the frequency can fall directly into the receive band. With this unique feature, the system can be configured to simultaneously perform real-time diagnostic monitoring of the transmit and receive links.
Tx chipset greatly reduces component count and costMaxim's basic four-chip solution replaces a large number of components compared to all zero-IF transmitter architectures. Compared to the traditional two-upconversion transmitter architecture, this new solution can replace six sets of functions, saving 65% of the net cost (relative to the replaced component). Maxim's chipset requires only 26mm x 27mm of board space, saving 50% less space than other comparable circuit functions. Cost and space savings make next-generation GSM/EDGE designs where cost and density issues are paramount.
The MAX2021/MAX2023 and MAX2058/MAX2059 are available in 36-pin TQFN and 40-pin TQFN packages, respectively. The MAX2021/MAX2023 start at $4.98 (more than 1,000 pieces, FOB USA), and the MAX2058/MAX2059 starts at $7.96 (more than 1,000 pieces, FOB USA).
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