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AFEs target femtocells, software-defined radio

Posted: 02 Feb 2012 ?? ?Print Version ?Bookmark and Share

Keywords:AFE? software-defined radio? femtocell?

Texas Instruments Inc. (TI) has announced what it claims as the industry's fastest, highest-performance analog front end (AFE) for femtocell base stations and portable software-defined radio (SDR) applications. According to the company, the AFE7225 operates 25 percent faster than the competition, while increasing the signal-to-noise ratio (SNR) by 2dB and providing up to five times the DAC output current.

The low-power, 12bit AFE7225 integrates a dual 125MSPS ADC and dual 250MSPS DAC. In addition, the 12bit AFE7222 is available for lower bandwidth, power-sensitive applications. It integrates a dual 65MSPS ADC and dual 130MSPS DAC and uses 398mW in full-duplex or 212mW in half-duplex receive mode at full speed.

The AFE7225 and AFE7222 integrate more digital signal processing capabilities than similar AFEs, stated the company. They are the only mixed-signal AFEs with independent transmit and receive, 32bit numerically controlled oscillators (NCOs), serialized LVDS input/output options, and independent transmit/receive quadrature modulation correction for gain, phase and offset imbalances, boasted TI.

The AFEs consumes only 12mW of power in deep-sleep mode with a wake-up of only 13?s, or as little as 120mW in light-sleep mode with 5?s wake-up time, said the company. The dual ADC achieves 70dB SNR, while the dual DAC achieves an adjacent channel leakage ratio of 75dB with a 3G W-CDMA cellular signal.

Both devices feature independent transmit and receive digital block up- and down-conversion with 2x to 4x interpolation, 2x decimation, coarse and 32bit NCO frequency mixers; digital correction of gain, phase and offset for quadrature modulation receive and/or transmit; and a peak/rms power meter.

TI added that the dual 12bit auxiliary DAC and dual-input 12bit auxiliary ADC eliminate the need for a separate monitoring and control device, reducing board space, power and cost. Additionally, digital DAC inputs and ADC outputs can be configured for serial LVDS to save pin/trace-count and aid long-trace signaling; or multiplexed 12bit CMOS for a low-power interface, supporting full-duplex over two buses or half-duplex from one or two digital buses.

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 100MHz for transmit, and a single ADC channel can be used to capture IFs of more than 300MHz, with the unused channels shut down to conserve power. For femtocell base stations, the AFEs provide macrocell performance when combined with high-quality RF components, such as the TRF372017 IQ modulator with local oscillator and the TRF371125 IQ demodulator.

Evaluation modules are available for $499. The AFE7222EVM and AFE7225EVM include the TRF370333 IQ modulator and CDCE72010 clock jitter cleaner, as well as TI power management devices such as DC/DC converters and low-noise LDOs, to provide a complete bits-to-RF prototyping and reference design.

The AFE7225 and AFE7222 are available in a 9 x 9mm QFN package for a suggested retail price of $29.50 and $19.50, respectively, for 1,000-units.





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