DC399A - Demo Manual

January 09, 2002
Demo board DC399A Quick Start Guide.
I. Introduction
The DC399A demo board (Figures 1 & 2) is intended to demonstrate the capabilities of the LT5504
IC. The LT5504 IC operates over a wide supply voltage range, from 5.25V down to 2.7V.
The LT5504 consists of RF/IF limiters, a LO buffer amplifier, a limiting mixer, 3rd-order 450MHz
integrated low pass filters, RF/IF detectors and an output interface. The ultra wide dynamic range is
achieved by measuring the RF signal using an RF detector and RF limiter, and simultaneously
measuring a down-converted IF signal using IF detectors and IF limiters. These signals are summed
to generate an accurate linear DC voltage proportional to the input RF power in dB. The output is
buffered with a low impedance output driver.
1
GND
Vout
VCC
DC399A
LT5504
RF IN
LO IN
LT5504 IC
JP1
RF MEASURING RECEIVER
Figure 1. DC399A demo board
Vcc
C2
C5 C6
C3
R2
Jumper
RF
R1
C1
T1
1 Vcc
Vcc 8
2
RF+
Vout 7
3
RF-
LO
4 GND
C4
6
EN 5
LT5504
RSSI output
R2
C7
R5
R4
LO
input
Figure 2. DC399A demo board schematic.
II. LT5504 basic tests and measurements.
1. Connect all the test equipment and power supplies as shown on Figure 3.
2. Set power supply to desired supply voltage from 2.7 to 5.25 volts.
3. When jumper (JP1) plugged-in, it provide HIGH logic level which enables the IC. When
jumper (JP1) is removed, it provides LOW logic level, which disables the IC. External
2
4.
5.
6.
7.
ENABLE voltage source or pulse generator can be connected to the lower pin of the jumper
(JP1) assembly and ground. The lower pin of the jumper is connected to the EN pin 5 of the
IC. NOTE: The on/off threshold voltage is about Vcc/2. When the input voltage is higher
than 0.6*Vcc, the circuit is completely turned on. When the input voltage is less than
0.4*Vcc, the circuit is turned off.
Set Signal Generator #1 for desired frequency within frequency range of 800 to 3000 MHz.
Set Signal Generator #1 Pout for desired output level within range of -80 to +5 dBm (CW
signal). Set Signal Generator #2 for frequency below or above the Signal Generator #1
frequency setting by the factor of 50 to 450 MHz, Pout = -10 dBm, CW signal.
NOTE 1: For RF input frequencies above 2.2 GHz LOW Side LO injection is preferable.
NOTE 2: Internal IF amplifier frequency range is 50 to 450 MHz.
Perform RSSI measurements. Change Signal Generator #1 Pout setting for any other desired
output level within range of -80 to +5 dBm and repeat the RSSI measurement.
Using Step 4 initial settings set Signal Generator #1 for ASK modulated signal (up to 5 MHz).
Measure recovered ASK signal at RSSI output.
3
+
Oscilloscope
Power
. Supply
GND
VCC
+
Vout
DC399A
LT5504
DC Voltmeter
RF IN
LO1 IN
Signal Generator 2
LT5504 IC
JP1
RF MEASURING RECEIVER
Signal Generator 1
Figure 3. Test set up for LT5504 RSSI measurements.
4
Similar pages