5

Basic tests and measurements.

1. Connect test equipment and power supplies to the demo board as shown in Figure 4.

To turn ON the LT5502 IC set two dip switches:

• STBY – ON, which is LOW (shift switching knob to the left on dip switch 2).

• EN – OFF, which is HIGH (shift switching knob to the right on dip switch 1).

2. Set power supply #1 output for +3.0 V and current limit for 40 mA. Set power supply

#2 output for +3.0 V and current limit for 40 mA. Nominal DC current for each

power supply should be about 25 mA.

• NOTES: A single power supply can be used for both supply inputs. For

precise power consumption measurements, two power supplies are preferred.

• Power supply #2 is used for external baseband drivers and should be set for

3.0 V to 5.0 V. Power supply #1 provides supply voltage to the LT5502 IC

and can be set from 1.8 to 5.25 V.

3. Set signal generator #1 for 280 MHz, CW mode, with output power –50 dBm.

4. Set signal generator #2 for 570 MHz, CW mode, with output power –10 dBm. NOTE:

280 MHz input and 570 MHz LO frequencies will result in 5.0 MHz Baseband (BB)

output signal.

5. Set spectrum analyzer: frequency span 0 to 10 MHz, amplitude reference (top of the

screen) to +10 dBm, Res BW = 100 KHz, VBW = 30 KHz.

6. BB output power measurement. Place a marker on the measured 5.0 MHz tone.

Measure power of 5.0 MHz BB (offset) signal in Q. The power should be 1.5 to 3.5

dBm.

NOTE: Test points E1, E2, E6 and E7 are provided for reference. If necessary, test

points E1 or E2 can be used for optional I-channel BB outputs tests and

measurements. Correspondingly, test points E6 and E7 can be used for optional Q-

channel BB outputs tests and measurements. In this case C10, C11, C14 and C15

should be removed.

7. Optional BB output power measurement. Measure power of 5.0 MHz BB (offset)

signal of the other (I) channel. Power should be very close to step 6 measurements.

8. 3.0 dB limiting sensitivity measurement. Put a marker on the measured 5.0 MHz tone

in reference measuring mode. Reduce power of signal generator #1 (in 1 dB steps)

until the 5.0 MHz marker drops by a factor of 3.0 dB. The corresponding signal level

at signal generator #1 output is the signal level representing the sensitivity related to –

3.0 dB Baseband output signal drop. This IF input signal level should be –79 dBm to

–77 dBm for evaluation boards with an IF input transformer, and –76 dBm to –70

dBm for evaluation boards without an IF input transformer.

9. RSSI measurements. Change signal generator #1 output power with 1 or 2 dB step

increments, from –85 to +5.0 dBm. RSSI output measured by digital DC voltmeter

should be 0.25 to 1.05 V correspondingly.

10. BB phase and amplitude mismatch measurements. Connect two (vertical) inputs of

the oscilloscope to the I/Q BB outputs (SMA connectors J2 and J3). Measurements

should be done with internal or external 50-ohm termination resistors. NOTE:

Oscilloscope should be 1GHz or faster. Calibration and identical connecting cables

are required. Measure the phase and amplitude errors. Phase error should be +/- 2.0

degrees maximum. Amplitude error should be within +/- 0.25 dB.