Application Note; Quick Start Procedure - Linear Technology LT5557 Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1131A

APPLICATION NOTE

ABSOLUTE MAXIMUM INPUT RATING
Supply Voltage (V , V
CC1
Enable Voltage ........................–0.3V to V
LO Input Power........................................ +10dBm
LO Input DC Voltage ..................... -1V to V
RF Input Power ........................................ +12dBm
RF Input DC Voltage..................................... ±0.1V
CAUTION: This part is sensitive to electrostatic dis-
charge (ESD). Observe proper ESD precautions when
handling the LT5557.
FREQUENCY RANGE
Demonstration circuit 1131A is optimized for evaluat-
ing the LT5557 IC for downconverting a RF signal in
the frequency range of 1.6GHz to 2.3GHz to a 240MHz
IF frequency with either low-side or high- side LO in-
jection.
The LT5557's RF input is internally matched to 50Ω Ω Ω Ω
from 1.6GHz to 2.3GHz with better than 12dB return
loss. Its LO input port is internally matched to 50Ω Ω Ω Ω
from 1GHz to 5GHz with better than 10dB return loss.
The frequency range of both ports is easily extended
with simple external matching. Please refer to the
LT5557 datasheet Applications Information section.
Demonstration circuit 1131A utilizes a transformer for
impedance transformation and differential to single-
ended conversion on the IF output port. The IF output
is 50Ω Ω Ω Ω matched for 240MHz, but can be modified for
other IF frequencies. Equations for calculating com-
ponent values, as well as values for several common IF
frequencies are given in the LT5557 datasheet Applica-
tions Information section.

QUICK START PROCEDURE

Demonstration circuit 1131A is easy to set up to evalu-
ate the performance of the LT5557. Refer to Figure 1
for proper measurement equipment setup and follow
the procedure below:
+ -
, IF , IF ) ................. 4V
CC2
+ 0.3V
CC
+ 1V
CC
HIGH SIGNAL LEVEL DOWNCONVERTING MIXER
TEST EQUIPMENT AND SETUP
Refer to Figure 1 for proper measurement equipment
setup.
Use high performance signal generators with low har-
monic output for 2-tone measurements. Otherwise,
low-pass filters at the signal generator outputs should
be used to suppress higher-order harmonics.
High quality combiners that provide broadband 50Ω Ω Ω Ω
termination on all ports and have good port-to-port
isolation should be used. Attenuators on the outputs
of the signal generators are recommended to further
improve source isolation, to prevent the sources from
modulating each other and generating intermodulation
products.
Spectrum analyzers can produce significant internal
distortion products if they are overdriven. Generally,
spectrum analyzers are designed to operate at their
best with about –30dBm to -40dBm at their input. Suf-
ficient spectrum analyzer input attenuation should be
used to avoid saturating the instrument.
Before performing measurements on the DUT, the sys-
tem performance should be evaluated to ensure that:
1) a clean input signal is obtained, and 2) the spectrum
analyzer internal distortion is minimized.
Note 1: Care should be taken to never exceed absolute
maximum input ratings.
Note 2: DC power should never be applied to the EN
pin before it is applied to the V pin.
CC
2