uaa1570hl NXP Semiconductors, uaa1570hl Datasheet - Page 27

• Manufacturer Part Number: uaa1570hl
• Description: Global Positioning System Gps Front-end Receiver Circuit
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The limitation imposed by image noise is illustrated in
Fig.18 where the ideal calculated filter response is
compared against the measured noise density at the
output of the first IF filter. The single sided FET probe
measured result was corrected by +6 dB to account for
balanced processing and
or 11.2 dB to accommodate power conversion losses.
The IF noise density selectivity is seen to be limited by the
available RF gain and noise figure of the first mixer. At the
image frequency, 34.86 MHz, the measured noise floor is
approximately 13 dB below the desired IF level at
41.82 MHz. This will result in an image contribution to the
noise figure of the system of approximately 0.2 dB.
1999 May 10
Global Positioning System (GPS) front-end
receiver circuit
(1) Ideal calculated filter response.
(2) Measured filter noise density.
Fig.18 First IF filter output noise power density (application board).
10 log
handbook, halfpage
--------------- -
663
(dBm/Hz)
50
N d
120
130
140
150
160
30
34.86
34
10
6
/sec
(2)
38
(1)
27
41.82
The in-band noise density can be estimated based on the
single-ended voltage gain to the output of the IF filter. With
the antenna thermal input level at approximately
voltage gain from the antenna to the IF filter output of
approximately 47 dBV (at 5 V supply voltage), we can
expect the differential noise power density to be
approximately 174 dBm + 4 dB + 47 dBV + 6 dB
(conversion to balanced)
or 129 dBm/Hz. The final term converts the measured
power using a high impedance FET probe, calibrated to a
50
output environment.
174 dBm/Hz, noise figure of approximately 4 dB and
42
10
environment, to the actual 663
6
/sec
46
f (MHz)
MHB281
50
10 log
663
--------------- -
50
UAA1570HL
Product specification
differential filter