Linear Technology LT5557 Quick Start Manual page 3

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1131A
Connect all test equipment as shown in Figure 1.
1.
Apply 3.3V DC supply power, and verify that the cur-
2.
rent consumption is approximately 81.6mA.
Apply RF and LO input signals to perform AC meas-
3.
urements.
Set the LO signal generator (#1) to provide a
4.
1710MHz, -3dBm, CW signal to the demo board LO
IN port.
Set the RF signal generators (#2 and #3) to provide
5.
two –6dBm CW signals to the demo board RF IN
port—one at 1950MHz, and the other at 1951MHz.
Set the Spectrum Analyzer's frequency range to cap-
6.
ture the 240MHz IF output. Sufficient spectrum ana-
lyzer input attenuation should be used to avoid satu-
rating the instrument.
Conversion gain and Input 3
7.
measured:
Gc = P1 – Pin
a.
IIP3 = (P1 – P3) / 2 + Pin
b.
Where P1 is the lowest power level of the two fun-
damental output tones at either 240MHz or at
241MHz, P3 is the largest 3
239MHz or at 242MHz, and Pin is the input power
(in this case, -6dBm). All units are in dBm.
HIGH SIGNAL LEVEL DOWNCONVERTING MIXER
rd
order intercept can be
rd
order product at either
To measure the 2RF-2LO output spurious product,
8.
turn off signal generator 3. Set signal generator 2 to
f = f + f /2. In this case, f
RF LO IF
240MHz / 2 = 1830MHz. Then the desired output
would be at 120MHz, and the 2RF-2LO output spur
would be at 240MHz. The dBc difference between
the two outputs is the 2RF-2LO output spurious
product.
Follow the same procedure for 3RF-3LO output spu-
9.
rious product measurement. This time, set signal
generator 2 to f
RF
240MHz / 3 = 1790MHz. The desired output would
be at 80MHz, and the 3RF-3LO output spur would
be at 240MHz. The dBc difference between the two
outputs is the 3RF-3LO output spurious product.
Measure RF to LO isolation, LO leakages, and Input
10.
1dB compression.
Single-Sideband Noise Figure can be measured on a
11.
noise figure meter.
manual for instructions. Be sure to use a high qual-
ity signal generator and a band-pass filter on the LO
input. A band-pass filter on the RF input port is re-
quired for image suppression.
= 1710MHz +
RF
= f + f /3 = 1710MHz +
LO IF
Refer to noise figure meter
3