QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 933A

HF/VHF/UHF DOWNCONVERTING MIXER

2

APPLICATION NOTE

ABSOLUTE MAXIMUM INPUT RATING

Supply Voltage ..................................................... 5.5V

Enable Voltage.................................–0.3V to V

CC+0.3V

LO+ to LO- Differential Voltage .......................... ±1.5V

..................................................(+6dBm equivalent)

RF+ to RF- Differential Voltage........................... ±0.7V

................................................(+11dBm equivalent)

FREQUENCY RANGE

Demonstration circuit 933A is optimized for 140MHz

RF to 10MHz IF downconversion with high-side LO

injection. However, it can also be used at other fre-

quencies.

The RF input port is well matched with better than

10dB return loss over the frequency range from

100MHz to 195MHz. The simple resistive LO input

matching is robust up to 1.5GHz. The IF output port

has better than 10dB return loss from 500kHz to

95MHz.

With proper matching, the RF, LO and IF ports can be

tuned for operation at other frequencies. Please refer

to the LT5512 datasheet Applications Information

section.

TEST EQUIPMENT AND SETUP

Refer to Figure 1 for proper measurement equipment

setup.

Use high performance signal generators with low

harmonic output for 2-tone measurements. Other-

wise, low-pass filters at the signal generator outputs

should be used to suppress higher-order harmonics.

High quality combiners that provide broadband 50

Ω

termination on all ports and have good port-to-port

isolation should be used. Attenuators on the outputs

of the signal generators are recommended to further

improve source isolation, to prevent the sources from

modulating each other and generating intermodula-

tion products.

Spectrum analyzers can produce significant internal dis-

tortion products if they are overdriven. Generally, spec-

trum analyzers are designed to operate at their best with

about –30dBm to -40dBm at their input. Sufficient

spectrum analyzer input attenuation should be used

to avoid saturating the instrument.

Before performing measurements on the DUT, the

system performance should be evaluated to ensure

that: 1) a clean input signal is obtained and 2) the

spectrum analyzer internal distortion is minimized.

QUICK START PROCEDURE

Demonstration circuit 933A is easy to set up to evalu-

ate the performance of the LT5512. Refer to Figure 1

for proper measurement equipment setup and follow

the procedure below:

1.

Connect signal generator outputs to demo board

RFin port (SMA connector J1) and LOin port (SMA

connector J2) via coaxial cable.

2.

Connect demo board IFout port (SMA connector

J3) to spectrum analyzer input via coaxial cable.

3.

Connect DC power supply negative (-) output to

demo board GND pin.

4.

Connect DC power supply positive (+) output (4.5V

to 5.25V) to demo board Vcc pin.

NOTE:

Do not exceed 5.5V, the absolute maximum

supply voltage.

5.

Using a jumper cable, connect demo board Vcc pin

to EN pin. Now the detector is enabled (on) and is

ready for measurement.