User Manual Part 1

47
Front End LNA and Bypass Switching
The Low Noise Amplifier (LNA) is critical in determining the overall noise figure of the
receiver chain. An MGA-71543 amplifier (U39) provides optimum noise figure, gain, intercept
point, and power consumption.
Post-LNA Bandpass Filters
An additional bandpass filter is located after the LNA. This filter is identical to the front
end filter previously described and provides additional image rejection.
Mixer and LO Filter
A double-balanced, low-level ADEX-10L mixer (MX1) with a LO drive level of +4 dBm is
used for the first conversion. This mixer provides a good dynamic range with a 3 dB lower LO
drive than the more traditional +7 dBm drive mixers. This reduces power consumption and also
the conducted and radiated local oscillator leakage from the receiver.
High side injection is used to provide optimum spurious performance. A LO filter prior to
the mixer LO port reduces wideband noise from the LO synthesizer which improves receiver
sensitivity.
IF Filter and Amplifier