Avago公司的ALM-1812是高增益低噪音GPS前端放大器,組合了高增益LNA和GPS FBAR濾波器.LNA采用Avago的GaAs增強模式pHEMT工藝,而一流的FBAR濾波器在Cell/PCS頻段有極好的抑制特性,大于85dB. ALM-1812的增益為19.1dB,NF為1.66dB,IIP3 = +2 dBm, IP1dB = -8 dBm.本文介紹了ALM-1812主要特性和指標, 應用電路,演示板布局和電路圖以及所用元器件與散射參數(shù)和測試參考平面圖.
ALM-1812: High-Gain GPS Low Noise Amplifier with Integrated Filters and Variable Current/Shutdown Function
Avago Technologies’ ALM-1812 is a GPS front-end module that combines a high-gain low-noise amplifier (LNA) with GPS FBAR filters. The LNA uses Avago Technologies’ proprietary GaAs Enhancement-mode pHEMT process to achieve high gain with very low noise figure and high linearity. Noise figure distribution is very tightly controlled. A CMOS-compatible shutdown pin is included either for turning the LNA on/off, or for current adjustment. The integrated filter utilizes an Avago Technologies’ leading-edge FBAR filter for exceptional rejection at Cell/PCS-Band frequencies.
The low noise figure and high gain, coupled with low current consumption make it suitable for use in critical low-power GPS applications or during low-battery situations.
ALM-1812主要特性:
• Very Low Noise Figure
• Exceptional Cell/PCS-Band rejection
• Low external component count
• Fully-matched at RF input and RF output
• Shutdown current: < 1 uA
• CMOS compatible shutdown pin (SD)
• ESD:> 3kV at RFin pin
• 4.5 x 2.2 x 0.95 mm3 size
• Adjustable bias current via single external resistor/voltage
• Lead-free, Halogen free and meets MSL3
ALM-1812主要指標:
Specifications (Typical performance @ 25°C) At 1.575GHz, Vdd = 2.8V, Idd = 6.8mA
• Gain = 19.1 dB
• NF = 1.66 dB
• IIP3 = +2 dBm, IP1dB = -8 dBm
• S11 = -10 dB, S22 = -15 dB
• Cell-Band Rejection:> 90dBc
• PCS-Band Rejection:> 85dBc
ALM-1812應用:
• GPS Front-end Module
圖1. ALM-1812應用電路
圖2.ALM-1812演示板布局圖
應用電路所用元件表:
圖3.ALM-1812演示板和應用電路框圖
Notes
1. The module is fully matched at the input and output RF pins. The RFin pin is directly connected to a shunt inductor that is grounded. The RF output filter blocks DC. Best noise performance is obtained using high-Q wirewound inductors. This circuit demonstrates that low noise figures are obtainable with standard 0402 chip inductors.
2. C2 and L2 form a matching network that affects the frequency response and linearity of the LNA, these can be tuned to optimize gain and return loss.
3. L1 and R1 isolates the demoboard from external disturbances during measurement. It is not needed in actual application. Likewise, C1 and C3 mitigate the effect of external noise pickup on the Vdd and Vsd lines respectively. These components are not required in actual operation.
4. Bias control is achieved by either varying the Vsd voltage with/ without R2, or fixing the Vsd voltage to Vdd and adjusting R2 for the desired current.
圖4.ALM-1812散射參數(shù)和測試參考平面圖
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