ADL5355ACPZ-R7 datasheet(18/24 Pages) AD

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ADL5355

Rev. 0 | Page 18 of 24

APPLICATIONS INFORMATION

BASIC CONNECTIONS

The ADL5355 mixer is designed to downconvert radio

frequencies (RF) primarily between 1200 MHz and 2500 MHz

to lower intermediate frequencies (IF) between 30 MHz and

450 MHz. Figure 52 depicts the basic connections of the mixer.

It is recommended to ac-couple RF and LO input ports to

prevent non-zero dc voltages from damaging the RF balun or LO

input circuit. The RFIN capacitor value of 3 pF is recommended

to provide the optimized RF input return loss for the desired

frequency band.

IF PORT

The mixer differential IF interface requires pull-up choke inductors

to bias the open-collector outputs and to set the output match.

The shunting impedance of the choke inductors used to couple

dc current into the IF amplifier should be selected to provide

the desired output return loss.

The real part of the output impedance is approximately

200 Ω, as seen in Figure 30, which matches many commonly

used SAW filters without the need for a transformer. This results in

a voltage conversion gain that is approximately 6 dB higher than

the power conversion gain, as shown in Table 2. When a 50 Ω

output impedance is needed, use a 4:1 impedance transformer,

as shown in Figure 52.

BIAS RESISTOR SELECTION

Two external resistors, RBIAS IF and RBIAS LO, are used to adjust the

bias current of the integrated amplifiers at the IF and LO terminals.

It is necessary to have a sufficient amount of current to bias both

the internal IF and LO amplifiers to optimize dc current vs.

optimum IIP3 performance. Figure 41, Figure 43, and Figure 44

provide the reference for the bias resistor selection when lower

power consumption is considered at the expense of conversion

gain and IP3 performance.

MIXER VGS CONTROL DAC

The ADL5355 features two logic control pins, VGS0 (Pin 12) and

VGS1 (Pin 13), that allow programmability for internal gate-to-

source voltages for optimizing mixer performance over desired

frequency bands. The evaluation board defaults both VGS0 and

VGS1 to ground. Power conversion gain, IIP3, NF, and IP1dB

can be optimized, as is shown in Figure 39 and Figure 40.

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