uaa1570hl NXP Semiconductors, uaa1570hl Datasheet - Page 29

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

Philips Semiconductors
As with the RF mixer maintaining the same single-ended
load as an effective differential load would result in the
same voltage applied to the equivalent resistance.
However, a single-ended effective load of 1.6 k could
also bring this mixer output to its clipping point.
The maximum recommended second mixer single-sided
voltage conversion gain (one input to one output) is
therefore approximately 16 for both single-ended and
differential output applications.
The estimated Single-Side Band (SSB) noise figure of the
IF mixer is approximately 7.5 dB at T
3 V supply with an input termination matching resistor of
2 k . Removing the termination results in an expected
noise figure of 4.9 dB from a 1 k source. This
degradation is distributed between the input termination
input loss and approximately a 1.6 dB increase in the
actual mixer noise figure.
The conversion gain is expected to be relatively supply
independent, increasing by only approximately 0.5 dB
from a supply value of 2.7 to 5.5 V. The IF mixer RF
bandwidth is also expected to only increase by
approximately 4%, while the mixer noise figure is expected
to decrease by less than 0.1 dB as the supply is increased
over the same supply range.
The IF mixer RF bandwidth, if not resonated, is dominated
by the mixer differential input capacitance of
approximately 1 pF.
1999 May 10
Global Positioning System (GPS) front-end
receiver circuit
(1) T
(2) T
(3) T
amb
amb
amb
= 40 C.
= +25 C.
= +85 C.
Fig.19 IF mixer 1 dB input compression point (800
handbook, halfpage
CP 1dB
(dBm)
amb
24
26
28
30
2
= 27 C from a
3
29
With tuned inputs, the IF mixer RF input bandwidth can be
extended quite high, but practical consideration warrant
that the RF filter terminating the input should provide band
limiting, thereby restricting the RF high frequency roll-off to
less than 200 MHz without special characterization efforts.
This is also, generally, the upper limit that the
programmable synthesizer supports. The noise figure of
the IF mixer as well as the limiter can be expected to
degrade as the operating frequencies are increased.
For example, at 200 MHz in a terminated 100
the DSB noise figure of the IF mixer will increase by at
least 10 dB to approximately 18 dB. If stability permits low
impedance first IF filters can be matched into the IF mixer
using step-up matching circuits such as baluns or
transformer like tuned networks, to minimize the
degradations.
The input compression point and noise figure of the IF
mixer, as measured in the characterization test board, are
plotted against temperature and supply voltage in
Figs 19 and 20. The characterization test board employs
the 1 : 16
the 800
output transformers, as well as transformer insertion
losses at 41.82 and 3.48 MHz, have been removed before
plotting. Therefore, this graph correlates to specification
and expected performance of the second mixer in the
referenced 800
(2)
(1)
(3)
4
V CC (V)
test environment. The losses of the input and
ratio transformers to provide a 50
MHB282
5
environment.
test circuit).
UAA1570HL
Product specification
system
match to