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LNAs tailored for cellular, LTE base stations

Posted: 07 Jun 2010 ?? ?Print Version ?Bookmark and Share

Keywords:LNA? amplifier? LTE? WiMAX? base station?

Avago Technologies has developed two next-generation LNAs for base station RF front-end design. With the addition of these 1500MHz to 2300MHz and 2300MHz to 4000MHz LNAs, Avago will complete its next-generation LNA series that covers all cellular bands for GSM, CDMA, UMTS, and WiMAX and LTE bands.

The two new LNAs target cellular infrastructure base station applications, such as transceiver radio cards, tower mounted amplifiers, combiners, repeaters and remote/digital radio heads. They set new standards for low noise figure. The wireless infrastructure industry is challenged to provide optimum coverage with the best signal quality in crowded spectrum. Receiver sensitivity is one of the most critical requirements in a BTS receive path design. Proper LNA selection, in particular the first-stage LNA, greatly affects the BTS receiver sensitivity performance. Low noise figure is a key design goal. Avago offers noise figure of 0.48dB at 1900MHz.

Another key design factor is linearity, which affects the receiver's ability to distinguish between closely spaced wanted and spurious signals. Third order intercept, OIP3, is used to specify linearity. At 1900MHz and typical operating condition of 5V/51mA, Avago's proprietary GaAs Enhancement-mode pHEMT process technology gives a noise figure of 0.48dB and an OIP3 of 35dBm. At 2500MHz and typical operating condition of 5 V/56mA, the noise figure is 0.59dB and OIP3 is 35dBm. With a low NF and high OIP3, the new Avago LNAs offer more design margin for the BTS receiver path than previous amplifiers.

With built-in active bias circuitry, Avago's LNA operating current is adjustable. This allows designers to make tradeoffs between operating current and output linearity, as measured by OIP3, while maintaining an optimum noise figure. BTS designers will have the flexibility to meet various design needs and regional requirements with the same Avago LNA.

Since more communication channels must now fit into a transmit/receive card, PCB real estate has become another key design challenge for BTS designers. Avago chose a QFN package with a small 4mm? footprint to meet market needs. The two new LNAs share the same package footprint, pinout and external matching network of the existing Avago 900MHz, MGA-633P8 LNA. A common PCB design can therefore be used for all base station RF front-end designs that operate in different frequency bands. This reduces the number of PCB designs needed to supply base station solutions for different bands and geographic markets.

The two new LNAs will be offered in 2mm x 2mm x 0.85mm, 8-lead, surface mount QFN packages that are RoHS-compliant. All devices operate over a very wide temperature range, -40C to +85C.

The two new LNAs will be available in Q2, completing Avago's next-generation series of high linearity, active bias, LNAs that include the existing 900MHz MGA-633P8.

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