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Introduction
Demo board DC333A demonstrates operation of the LT5502 IC. The LT5502 is a high
performance limiting amplifier and quadrature IF demodulator with 70MHz to 400MHz
input frequency, operating over the wide supply voltage range, from 5.25V down to 1.8V.
This allows the LT5502 to run directly from a single Lithium Ion battery, or from two or
more NiCad batteries. In combination with an appropriate RF front end and RF/IF bandpass
filters, the LT5502 forms a wideband receiver for applications at 900MHz, 1.8GHz, 2.4-
2.5GHz, or other frequencies. The LT5502 can even be used as a self-standing receiver at
frequencies below 400MHz.
IF Input
RSSI
output
Arrow.com.
Downloaded from
Demo board DC333A Quick Start Guide.
0.1 uF
12
13
Limiter 2
Limiter 1
6
7
62 ohm
15
3, 5, 8, 9,
14, 20, 21
LT5502
1.8 pF
2d LO input
Figure 1. Demo board DC333A block diagram.
100 pF
Vcc
4, 16, 17, 22
LPF
I mixer
0º
LO
buffer
LPF
90º
Q mixer
f/2
19
18
+2.0 to 5.0 V
External
Buffer
I outputs
1
2
Buffer
External
Buffer
Q outputs
24
23
Buffer
11
STBY
10
EN
I output
Q output
1
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Table of Contents
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Summary of Contents for Arrow DC333A
- Page 1 Demo board DC333A Quick Start Guide. Introduction Demo board DC333A demonstrates operation of the LT5502 IC. The LT5502 is a high performance limiting amplifier and quadrature IF demodulator with 70MHz to 400MHz input frequency, operating over the wide supply voltage range, from 5.25V down to 1.8V.
- Page 2 I/Q baseband signals are passed through fully integrated 5 -order low pass filters and output drivers. Demo board DC333A has additional output drivers, which provide 50-ohm output impedance. The LT5502 has a 4dB noise figure and an achievable sensitivity of –86 dBm. Figure 2 shows the baseband I/Q output voltage swing versus IF input power at an IF frequency of 280MHz.
- Page 3 A 62 ohm resistor provides broadband 50-ohm impedance matching. The cascaded NF for the IF circuit is degraded by 2.0 dB. Figure 1 shows a version of the demo board DC333A with 62 ohm terminating resistor.
- Page 4 Q outp.- I outp.- LO inp. IF inp. Signal Generator #2 RSSI STBY Vсс1 Digital DC Signal voltmeter Power Generator #1 Supply #1 Figure 4. Test and measurement set-up Arrow.com. Arrow.com. Arrow.com. Arrow.com. Downloaded from Downloaded from Downloaded from Downloaded from...
- Page 5 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. Arrow.com. Arrow.com. Arrow.com. Arrow.com.
- Page 6 BB filter. The same test can be conducted using a tracking generator or network analyzer. In this case, an external I/Q modulator will be necessary to bring BB signals back to the original input frequency range. Arrow.com. Arrow.com. Arrow.com.
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