QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1048A

1.5GHZ TO 2.7GHZ DIRECT CONVERSION I/Q RECEIVER

3

QUICK START PROCEDURE

Demonstration circuit 1048A is easy to set up to evalu-

ate the performance of the LT5575. Refer to Figure 1

for proper measurement equipment setup and follow

the procedure below:

NOTE:

a.

Care should be taken to never exceed absolute

maximum input rating.

b.

DC power should never be applied to the EN pin

before it is applied to the Vcc pin.

1.

Connect all test equipment as shown in Figure 1.

2.

Apply 5V DC supply power, and verify that the cur-

rent consumption is approximately 132mA.

3.

Apply RF and LO input signals to perform AC

measurements.

4.

Set the LO signal generator (#1) to provide a

1901MHz, 0dBm, CW signal to the demo board LO

input port.

5.

Set the RF signal generators (#2 and #3) to pro-

vide two –10dBm CW signals to the demo board

RF input port—one at 1899.9MHz, and the other

at 1900.1MHz.

6.

Set the Spectrum Analyzer’s start frequency to

100kHz and stop frequency to 1400kHz. Sufficient

spectrum analyzer input attenuation should be

used to avoid saturating the instrument.

7.

Measure input 2

nd and 3rd order intercepts:

a.

IIP2 = P1 – P2 + Pin

b.

IIP3 = (P1 – P3) / 2 + Pin

Where P1 is the lowest power level of the two fun-

damental output tones at either 900kHz or 1100kHz,

P2 is the 2

nd order product at 200kHz, P3 is the larg-

est 3

rd order product at either 700kHz or 1300kHz,

and Pin is the input power (in this case, -10dBm).

All units are in dBm.

8.

Voltage conversion gain can also be measured. But

be ware that the gain is reduced by combiner loss

plus 7.23dB, because the load impedance to each

output pin is 50

Ω

Ω

Ω

Ω in this setup. Please refer to the

LT5575 datasheet for more detailed explanation.

9.

Measure LO to RF leakage, RF to LO isolation, and

Input 1dB compression.

10.

Double-Side band Noise Figure can be measured di-

rectly on a noise figure meter. Refer to noise figure

meter manual for instructions.