Interference from co-located LNA

Often a GNSS receiver is placed in the same enclosure as a GNSS antenna and LNA to create an all in one GNSS receiver product (also referred to as a smart antenna).

The close proximity of a high-gain amplifier to the GNSS receiver may cause some low-level near-field energy from the receiver to be amplified and fed back into the receiver, causing C/No degradation to one or more constellations.

It is strongly advised in a smart antenna design that the receiver be enclosed in a shield to prevent this near-field energy from coupling into the antenna. This includes connecting the GNSS receiver input ground to the shield surrounding the receiver, similar to the following image. It is also strongly advised to use mounting rail for receiver cards used in this configuration.

The previous figure shows one method of shielding the receiver.

The rail mounting provision on the edges of the receiver card can also used to attach entire board shielding.