ADF4001BCP datasheet(20/28 Pages) AD

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AD8348

Rev. A | Page 20 of 28

APPLICATIONS

BASIC CONNECTIONS

Figure 49 shows the basic connections schematic for the AD8348.

C32

1000pF

C31

1000pF

R31

57.6Ω

J21

C21

1000pF

C22

1000pF

R21

60.4Ω

+VS

C0Q

0.1µF

C11

4.7µF

IFIP

R32

174Ω

T21

ETC1-1-13

IFIP

MXIP

VPOS2 VGIN

IOFS

QOFS

VREF

ENBL

LOIN

LOIP

VPOS1 COM1

IOPN

QOPN

IOPP

QOPP

VCMO ENVG

IAIN

QAIN

COM3 COM3

IMXO

QMXO

COM2 VPOS3

IFIN

MXIN

AD8348

C0l

0.1µF

J2I

IOPP

J3I

IOPN

J2Q

QOPP

J3Q

QOPN

C53

100pF

C54

0.1µF

+VS

C51

100pF

C52

0.1µF

+VS

VREF

SW12

+VS

SW11

+VS

ENBL

DENBL

C55

100pF

C56

0.1µF

VGIN

MXIP

R42

0Ω

T41

ETK4-2T

C41

1µF

C43

1000pF

C42

1000pF

Figure 49. Basic Connections Schematic

POWER SUPPLY

The voltage supply for the AD8348, between 2.7 V and 5 V, should

be provided to the +VPOSx pins, and ground should be connected

to the COMx pins. Each supply pin should be decoupled separately

using two capacitors whose recommended values are 100 pF and

0.1 μF (values close to these can also be used).

DEVICE ENABLE

To enable the device, the ENBL pin should be driven to VS.

Grounding the ENBL pin disables the device.

VGA ENABLE

Driving the voltage on the ENVG pin to VS enables the VGA. In

this mode, the MX inputs are disabled and the IF inputs are

used. Grounding the ENVG pin disables the VGA and the IF

inputs. When the VGA is disabled, the MX inputs should be used.

GAIN CONTROL

When the VGA is enabled, the voltage applied to the VGIN pin sets

the gain. The gain control voltage range is between 0.2 V and 1.2 V.

This corresponds to a gain range between +25.5 dB and −18.5 dB.

LO INPUTS

For optimum performance, the local oscillator port should be

driven differentially through a balun. The recommended balun

is M/A-COM ETC1-1-13. The LO inputs to the device should

be ac-coupled, unless an ac-coupled transformer is being used.

For a broadband match to a 50 Ω source, a 60.4 Ω resistor

should be placed between the LOIP and LION pins.

LOIP

LOIN

60.4Ω

1000pF

ETC1-1-13

Figure 50. Differential LO Drive with Balun

Alternatively, the LO port can be driven from a single-ended source

without a balun (Figure 51). The LO signal is ac-coupled directly

into the LOIP pin via an ac-coupling capacitor, and the LOIN pin

is ac-coupled to ground. Driving the LO port from a single-

ended source results in an increase in both quadrature phase

error and LO leakage.

LOIP

LOIN

60.4Ω

1000pF

Figure 51. Single-Ended LO Drive

The recommended LO drive level is between −12 dBm and

0 dBm. The LO frequency at the input to the device should be

twice that of the desired LO frequency at the mixer core. The

applied LO frequency range is between 100 MHz and 2 GHz.

IF INPUTS

The IF inputs have an input impedance of 200 Ω. A broadband

50 Ω match can be presented to the driving source through the use

of a minimum-loss L pad. This minimum-loss pad introduces

an 11.46 dB loss in the input path and must be taken into account

when calculating metrics such as gain and noise figure. Figure 42

shows the S11 of the IF input with and without the L pad.

1000pF

174Ω

57.6Ω

IFIP

IFIN

Figure 52. Minimum-Loss L Pad for 50 Ω IF Input

MX INPUTS

The mixer inputs, MXIP and MXIN, have a nominal impedance

of 200 Ω and should be driven differentially. When driven from

a differential source, the input should be ac-coupled to the

source via capacitors, as shown in Figure 53.

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