AD8348

Rev. A | Page 27 of 28

Table 6. Evaluation Board Configuration Options

Component

Function

Default Condition

Power supply and ground vector pins.

Not applicable

SW11, ENBL

the DENBL position to disable the device by grounding the Pin ENBL through a 50 Ω pull-down

resistor. The device can also be enabled via an external voltage applied to ENBL or VENB.

SW11 = ENBL

SW13, R15,

VGIN

Gain control selection: With SW13 in the POT position, the gain of the VGA can be set using the

R15 potentiometer. With SW13 in the EXT position, the VGA gain can be set by an external

voltage to the SMA connector VGIN. For VGA operation, the VGA must first be enabled by

setting SW12 to the IF position.

SW13 = POT

SW12

VGA is enabled. The IF input should be used when SW12 is in the IF position. With SW12 in the

MX position, the ENVG pin is grounded and the VGA is disabled. The MX inputs should be used

when SW12 is in the MX position.

SW12 = IF

IFIP, R31, R32

IF inputs: The single-ended IF signal should be connected to this SMA connector. R31 and R32

form an L pad that presents a 50 Ω termination to the driving source. This L pad introduces an

11.46 dB loss in the input signal path and should be taken into consideration when calculating

the gain of the AD8348.

R31 = 57.6 Ω

R32 = 174 Ω

MXIP, MXIN,

T41,

R41, R42,

C42, C43

Mixer inputs: These inputs can be configured for either differential or single-ended operation.

The evaluation board is by default set for differential MX drive through a balun (T41) from a

single-ended source fed into the MXIP SMA connector. To change to a differential driving source,

T41 should be removed along with Resistor R42. The 0 Ω Resistors R43 and R44 should be installed in

place of T41 to bridge the gap between the input traces. This will present a nominal differential

impedance of 200 Ω (100 Ω per side). The differential inputs should then be fed into SMA

connectors MXIP and MXIN.

T41 = M/A-COM ETK4-2T;

R41= OPEN; C42, C43 =

1000 pF; R42 = 0 Ω

LK11, VCMO

Baseband amplifier output bias: Installing LK11 connects VREF to VCMO. This sets the bias level

on the baseband amplifiers to VREF, which is equal to approximately 1 V. Alternatively, with

LK11 removed, the bias level of the baseband amplifiers can be set by applying an external

voltage to the VCMO test point.

LK11 installed

C8, C9, R4, R5

(I and Q)

Baseband amplifier outputs and output filter: Additional low-pass filtering can be provided at

the baseband output with these filters.

R4, R5 = 0 Ω

C10 (I and Q)

Mixer output dc-blocking capacitors: The mixer outputs are biased to VCMO. To prevent

damage to test equipment that cannot tolerate dc biases, C10 is provided to block the dc

component, thus protecting the test equipment.

C10 = 0 Ω

C1 to C7,

R1, R2,

L1 to L3

(I and Q)

Baseband filter: These components are provided for baseband filtering between the mixer

outputs and the baseband amplifier inputs. The baseband amplifier input impedance is high

and the filter termination impedance is set by R2. See Table 7 for the jumper settings.

All = OPEN

LK5 (I and Q)

Offset compensation loop disable: Installing these jumpers will disable the offset compensation

loop for the corresponding channel.

LK5x = OPEN

Table 7. Filter-Jumper Configuration Options

Condition

LK1x

LK2x

LK3x

LK4x

xMXO to xAIN Directly

•

•

xMXO to xAIN via Filter

•

•

xMXO to J1x Directly, xAIN Unused

•

•

xMXO to J1x via Filter, xAIN Unused

•

•

Drive xAIN from J1x

•