Quick Start Procedure - Linear Technology DC2077A Demo Manual

QUICK START PROCEDURE

Demo circuit 2077A can be set up to evaluate the perfor-
mance of the LTC6431-20. Refer to Figure 3 for proper
equipment connections and follow the procedure below:
Two-Tone Measurement
Connect all test equipment as suggested in Figure 3.
1. The power labels of VCC 4.75V-5.25V and GND directly
correspond to the power supply. Typical current con-
sumption of the LTC6431-20 is about 95mA.
2. Apply two independent signals f1 and f2 from signal
generator 1 and signal generator 2 at 240MHz and
241MHz, while setting the amplitude to –18dBm/tone
at the demo board input (J1).
3. Monitor the output tone level on the spectrum analyzer.
Adjust the signal generator levels such that the output
power measures +2dBm/tone at the amplifier output J2,
after correcting for external cable losses and attenuations.
SIGNAL
GENERATOR 1
LOWPASS FILTER
6dB ATTN PAD
(OPTIONAL)
COMBINER
Mini-Circuits
ADP-2-9
6dB ATTN PAD
(OPTIONAL)
LOWPASS FILTER
SIGNAL
GENERATOR 2
HP8644A
AMPLIFIER
Mini-Circuits
ZHL-2 OR EQUIVALENT
3dB ATTENUATION
PAD
AMPLIFIER
Mini-Circuits
ZHL-2 OR EQUIVALENT
HP8644A
Figure 3. Proper Equipement Setup for IP3 Measurement
DEMO MANUAL DC2077A
4. Change the spectrum analyzer's center frequency and
observe the two IM3 tones at 1 MHz below and above
the input frequencies. The frequencies of IM3_LOW and
IM3_HIGH are 239 MHz and 242 MHz, respectively. The
measurement levels should be approximately –92dBc;
+48dBm is typical OIP3 performance for the LTC6431-20
at 240MHz.
The OIP3 calculation is:
OIP3 = POUT + ∆IMD3/2
where:
POUT is the lower output signal power of the funda-
mental products.
∆IMD3 = POUT – PIM3; PIM3 is the higher third-order
intermodulation product.
Single-Tone Measurement
5. Continue with Step 4 above, turn off one signal source
to measure gain and harmonic distortions.
VCC = 4.75V TO 5.25V
DC POWER SUPPLY
+
GND V
20dB ATTENUATION
PAD
SPECTRUM
ANALYZER
Rohde & Schwarz
COAXIAL
FSEM30
CABLE
dc2077af
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