uaa1570hl NXP Semiconductors, uaa1570hl Datasheet - Page 20

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

Philips Semiconductors
7.2
The application circuit does not allow easy measurement,
calibration and documentation of the many sub-block
characteristics which ensure good system performance.
Therefore, test boards have been developed which allow
direct measurement of the sub-block characteristics.
These boards use a 1 : 16
transform 50
IF frequencies. The high-impedance side of these
transformers is terminated with a physical resistor to adjust
the UAA1570HL impedance at the port being measured, to
approximately 800 . This ensures that a calibrated signal
The transformer provides marginal performance at
41.8 MHz, so calibration results for this transformer are
also included in this document.
The 800
notes at the end of the table. The effects of the transformer
and associated termination losses have also been
removed to some extent, so that specifications reflect the
performance of the IC. The measured graph results were
all derived from the test boards and corrected to again
reflect part performance as much as possible.
However, this was not always possible, so some
discussion concerning the measurement limitations is
provided where appropriate. Where possible, fundamental
design relationships and limitations are indicated.
The following two graphs (Figs 11 and 12) reflect the
measured performance of the 1 : 16
transformer used to test the IF functions. Two transformers
were placed back-to-back to make these measurements.
Figure 11 represents the transmission function of just one
of these transformers over frequency. Figure 12
represents the associated return loss at one input with the
second transformer terminated into 50 . In the actual
UAA1570HL test board a single transformer is terminated
in 800 .
1999 May 10
is applied or received in the 50
that used in the application board. The UAA1570HL
Characteristic tables provided in this document are
calibrated to this 800
Global Positioning System (GPS) front-end
receiver circuit
Correlation of the UAA1570HL data sheet,
application and test boards
impedance environment is somewhat less than
to the more appropriate value of 800
environment as quantified in the
ratio RF transformer to
test environment.
ratio RF
at
20
In addition to the direct effects of power losses introduced
by the transformer (approximately 1.3 dB at 41.82 MHz),
which are reflected in the measured S21 results, the test
board results may also be impacted by deficiencies in the
transformer 1 : 4 voltage step-up ratio at 41.8 MHz;
however, this has not been quantified.
An additional correction must be made to the current test
results to compensate for internal 4 pF shunt capacitors on
each collector output of the first mixer, which have not
been resonated out in the testing.
The first mixer measurements also include a 3 dB loss due
to the 800
removed from the specification result. The second mixer
has similar 2.1 dB input and 3 dB output transformer
termination losses removed from the specification.
For measurements made at 3.48 MHz in the second IF,
0.4 dB must be added to the measured results to reflect
transformer losses at IF2, also.
In summary the measured gain of the first mixer has been
increased by 1.3 dB (transformer IL) + 1.4 dB (capacitive
roll-off effects) + 0.2 dB (gain match) + 3 dB (output
transformer termination loss) or 5.9 dB to calibrate out
these losses in the specification.
The measured gain of the second mixer has been
increased by 1.3 dB (input transformer IL) + 1.7 dB
(input term loss) + 0.4 dB (output transformer IL) and
+ 3 dB (output term loss) or 6.4 dB to calibrate out these
losses in the specification.
transformer termination. This loss is also
UAA1570HL
Product specification