Texas Instruments Incorporated has introduced an analog front end (AFE) for femtocell base stations and portable software-defined radio (SDR) applications. The low-power, 12-bit AFE7225 integrates a dual 125-MSPS analog-to-digital converter (ADC) and dual 250-MSPS digital-to-analog converter (DAC), improving the signal-to-noise ratio (SNR) by 2 dB and providing up to five times the DAC output current.
In addition to the AFE7225, the 12-bit AFE7222 is available for lower bandwidth, power-sensitive applications. It integrates a dual 65-MSPS ADC and dual 130-MSPS DAC and uses 398 mW in full-duplex or 212 mW in half-duplex receive mode at full speed.
The AFE7225 and AFE7222 both integrate digital signal processing capabilities for design flexibility. The company claims that are the only mixed-signal AFEs with independent transmit and receive, 32-bit numerically controlled oscillators (NCOs), serialized LVDS input/output options, and independent transmit/receive quadrature modulation correction for gain, phase and offset imbalances.
The AFE7225 and AFE7222 can be used in heterodyne or direct-conversion radio architectures. For heterodyne radios, a single DAC channel in the AFEs can be used to create an intermediate frequency up to approximately 100 MHz for transmit, and a single ADC channel can be used to capture IFs of more than 300 MHz, with the unused channels shut down to conserve power. For femtocell base stations, the AFEs provide macro-cell performance when combined with RF components such as the TRF372017 IQ modulator with local oscillator and the TRF371125 IQ demodulator.
The AFE7225 is available in a 9-mm x 9-mm QFN package for a suggested retail price of $29.50 for 1,000-units. The AFE7222 is available in a 9-mm x 9-mm QFN package for a suggested retail price of $19.50 in 1,000-unit quantities.
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