MAX2653 LNA with Gain-Step Retuned for GPS Applications

  
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This application note presents alternate RF matching networks for the MAX2653 SiGe LNA, tuned for the GPS band (1575MHz center frequency). Performance metrics (supply current, forward gain, NF, IIP3, reverse isolation and input/output return loss) for both high and low gain modes, as well as 2. 7V and 3. 0V supplies are provided. For VCC =
MAX2653 LNA with Gain-Step Retuned for GPS Applications - schematic

2. 7V, high-gain mode, this application provides 19. 2dB Gain, 1. 6dB NF, and The MAX2653 SiGe Low Noise Amplifier (LNA) is internally optimized for lowest noise performance in the US PCS (1930MHz to 1990MHz) and the European DCS (1805MHz to 1880MHz) receive bands. These LNAs offer a 20dB gain control step, externally adjustable gain and linearity (via single external resistor), 2. 7V to 3. 3V operation, and a 0. 25 µA shutdown mode. Maxim does not offer a stand-alone LNA for the GPS (1575MHz center) band that includes a gain-step, but re-tuning the MAX2653 to this lower band offers a excellent solution. These alternative matching values (Table 1) offer 0. 5dB more gain, 0. 1dB better noise figure, and 2dB better IIP3 - all for nearly identical supply current. For applications that do not require a gain step, Maxim offers the MAX2654 and MAX2655 SiGe GPS LNAs. They offer a bias current control (via external resistor) to set gain and linearity, a 0. 1 µA shutdown mode and integrated 50 © output matching. Find the datasheet at. After replacing the matching components on the EVKit, key performance metrics were re-tested at room temperature ”Table 2 provides the results of the re-tuned MAX2653 bench testing. These values are referred to the EVKit SMA connectors; to get values referred to the output of the matching networks, assume approximately 0. 2dB loss at each the output and the input. In this fashion, the NF of the circuit...



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