lna

__RF Low Noise Amplification__
For the low-noise amplifier stages, the MAX2611 low-noise amplifier from Maxim was used. The circuit used to bias the integrated circuit is shown in Figure 4.2.1. Figure 4.2.1 – Low Noise RF Amplifier The RF choke was chosen to give 500 Ohms of reactance at the given frequency. The capacitance of the blocking capacitors was chosen based on the absolute minimum frequency that the RF amplifier would reject (approximately 16 MHz). The biasing resistor was chosen to drive the amplifier with a bias current of 20 mA at a nominal device voltage of 3.8 V given a 5V supply voltage. The circuit was prototyped, and its scattering parameters were gathered using the network analyzer. Figure 4.2.2 shows its gain characteristics, and Figure 4.2.3 shows its output reflection coefficient (which can be used to determine the output impedance). Figure 4.2.2 – MAX2611 Gain Figure 4.2.3 – MAX2611 Output Reflection Coefficient