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9. For noise under jamming conditions, the following is needed. A 15dB ENR noise
Fig 5. BGU7004 evaluation board including its connections
6. Linearity
At the average power levels of –130 dBm that have to be received by a GPS receiver,
the system will not have in-band intermodulation problems caused by the GPS-signal
itself. Strong out-of-band cell phone TX jammers however can cause linearity problems,
and result in third-order intermodulation products in the GPS frequency band.
6.1 Out-of-Band input third-order Intercept point
This parameter is being measured by a two-tone measurement where the carriers have
been chosen as L1 + 138 MHz and L1 + 276 MHz. Where L1 is the center of the GPS
band, 1575.42 MHz. So the two carriers are 1713.42 MHz and 1851.42 MHz that can be
seen as two TX jammers in UMTS FDD and GSM1800 cell phone systems.
One third-order product (2f
linearities can fall at the desired 1575.42-MHz frequency as follows.
2f
-f
1
This third-order product can influence the sensitivity of the GPS receiver drastically. So
this third-order intermodulation product needs to be as low as possible, meaning the out-
of-band intercept point must be as high as possible.
Fig 6, Fig 7 and Fig 8
UM10491
User manual
source, a directional coupler, GPS band pass filter, a noise-figure analyzer or a
spectrum analyzer with noise option can be used. See
-f
1
2
=2(1713.42 MHz)-1851.42 MHz=1575.42 MHz
2
show the O_IIP3 of the BGU7004 at different supply voltages.
Rev. 1.0 — 14 June 2011
) generated in the LNA due to amplifier third order non-
UM10491
BGU7004 GPS LNA EVB
Fig 12
© NXP B.V. 2011. All rights reserved.
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