Datasheet DC503A Datasheet (Linear Technology)

DC503A DEMO BOARD QUICK START GUIDE

Description:

The DC503A demo circuit board is intended to demonstrate the capabilities of the LT5512
downconverting mixer IC for cable infrastructure applications.

The LT5512 (Figure 1) is a broadband high signal level mixer IC optimized for high linearity
downconverter applications including cable and wireless infrastructure. The IC includes a
differential LO buffer driving a double-balanced mixer. An integrated RF amplifier improves LO­RF isolation and eliminates the need for precision external bias resistors.

The LT5512 is a high-linearity alternative to passive diode mixers. Unlike passive mixers, which
have conversion loss and require high LO drive level, the LT5512 delivers conversion gain and
requires significantly lower LO drive levels.

The DC503A demo board downconverts 1230MHz RF input to 270-870MHz IF output. The LO is
injected from the high-side between 1500MHz and 2100MHz.

Figure 1. LT5512 IC Block Diagram

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LT5512 Downconverting Mixer Single-Tone Measurements for 1230 MHz CATV Band.

1. Connect all test equipment as shown in Figure 2.

2. Set the Power Supply output voltage to 5V, and set the current limit to 100mA.

3. Connect TP1 (EN) to the 5V power supply. Mixer is in ENABLE mode.

4. Set the Signal Generator #1 to provide an 1800MHz, -10dBm, CW signal to the demo board
LOin port.

5. Set the Signal Generator #2 to provide a 1230MHz, -10dBm, CW signal to the demo board
RFin port.

6. Set the Spectrum Analyzer’s center frequency to 570MHz. Perform mixer conversion gain,
and 1dB compression measurements.

7. Set the Spectrum Analyzer’s center frequency to 1800MHz. Perform mixer LO to IF
leakage measurement.

SIGNAL

GENERATOR 2

SIGNAL

GENERATOR 1

SPECTRUM
ANALYZER

Figure 2. Test Set-Up for Mixer Single-Tone Measurements.

POWER SUPPLY

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LT5512 Downconverting Mixer Two-Tone Measurements for 1230MHz CATV Band.

∑

1. Connect all test equipment as shown in Figure 3.
Note: 1). A high quality combiner that provides 50-ohm termination on all ports and has

good port-to-port isolation should be used.

2). The two 3dB attenuators on the inputs of the combiner are used to further
improve source isolation.

2. Set the Power Supply output voltage to 5V, and set the current limit to 100mA.

3. Connect TP1 (EN) to the 5V power supply. Mixer is in ENABLE mode.

4. Set the Signal Generator #1 to provide a 1800MHz, -10dBm, CW signal to the demo board
LOin port.

5. Set the Signal Generator #2 and #3 to provide two -10dBm CW signals to the demo board
RFin port—one at 1229.9MHz, and the other at 1230.1MHz.

6. Set the Spectrum Analyzer’s center frequency to 570MHz. Perform input 3rd order
distortion measurement. (IIP3 = P1 + (P1 – P3) / 2 – Gc, where P1 is the lowest power level
of the two desired output tones at either 569.9MHz or 570.1MHz, P3 is the largest 3rd order
product at either 569.7MHz or 570.3MHz, and Gc is conversion gain. P1 and P3 are in units
of dBm, and Gc is in dB.)

SIGNAL

GENERATOR 2

3dB PAD

3dB PAD

SIGNAL

GENERATOR 3

Figure 3. Test Set-Up for Mixer Two-Tone Measurements.

SIGNAL

GENERATOR 1

SPECTRUM
ANALYZER

POWER SUPPLY

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AAC (was TAD) [phone] CHIP RESISTORS

AAC (was TAD) [phone]

AAVID [phone] HEAT SINKS

ALLEN BRADLEY [phone] CARBON RESISTORS

AMP [phone] PC MOUNT BNC

APEM [phone] SMD TOGGLE/PB SWITCH

API DELEVAN [phone] INDUCTORS

AVX [phone] CHIP CAPS

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AVX [phone] TANTALUM CAPS

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TOKO [phone] RF PRODUCTS

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UNITED CHEMICON [phone] ELECTROLYTIC CAPACITOR

VISHAY [phone] ZENER/SM. SIGNAL DIODES

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WIMA [phone] PAPER/FILM CAPACITORS

ZETEX [phone] SMALL SIGNAL DISCRETES

ZIERICK [phone] STAKED PINS

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Mouser Electronics

Authorized Distributor

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Analog Devices Inc.:
DC503A