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AN383

Si47XX ANTENNA, SCHEMATIC, LAYOUT, AND DESIGN GUIDELINES

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AN383

2.2. Emissions Mitigation Components

The following components may be placed to reduce VCO emissions. This is only required if regulatory testing

requires measuring emissions at the VCO frequency of 3–4 GHz. Refer to Section “2.6.1. Emissions Mitigation

Checklist” for detailed layout and grounding recommendations pertaining to the components described below.

2.2.1. FMI Mitigation Components

Table 2. FMI Mitigation Components

Option

1

2

Components

C5 = NP

F1 = BLM15GA750SN1

C14 = 6 pF

C5 = 2.7 pF

F1 = 20 nH

C14 = 2.7 pF

Best

Sensitivity

Less

(+1.75 dB vs Option1)

Mitigation

Best

Cost

Higher

Good

Lower

C5 (NP) is an optional filter capacitor for FMI pin 2 and may be placed to shunt VCO energy to GND and prevent it

from radiating from an antenna connected to the FMI pin. This pad is a placeholder for alternate emission

mitigation option 2. While it is recommended to select option 1 for best sensitivity and mitigation performance,

leaving this pad ensures that there is no redesign necessary between options. Route pin 2 to GND/RFGND if the

pin functionality is not used.

F1 (BLM15GA750SN1) is an optional bead for FMI pin 2 and may be placed to prevent VCO energy from radiating

from FMI pin. Place F1 as close as possible to FMI pin 2. Route pin 2 to GND/RFGND if the pin functionality is not

used.

C14 (6 pF) is an optional filter capacitor for FMI pin 2 and may be placed to shunt VCO energy to GND and prevent

it from radiating from an antenna connected to the FMI pin. Place C14 as close as possible to FMI pin 2. The

ground path should be optimized on the top layer. Route pin 2 to GND/RFGND if the pin functionality is not used.

2.2.2. AMI Mitigation Components

Table 3. AMI Mitigation Components

Option

1

2

3

Components

C17 = 3.3 pF

L2 = 10 nH

C16 = 3.3 pF

C17 = 2.7 pF

L2 = 20 nH

C16 = 2.7 pF

C17 = NP

L2 = BLM15GA750SN1

C16 = NP

Best

Sensitivity

Less

(+3 dB vs Option1)

Least

(+6 dB vs Option1)

Mitigation

Good

Cost

Lower

Better

Lower

Best

Higher

C17 (3.3 pF) is an optional filter capacitor for AMI pin 4 on Si473x devices and may be placed to shunt VCO energy

to GND and prevent it from radiating from an antenna connected to the AMI pin. Place C17 as close as possible to

AMI pin 4 and RFGND pin 3. The ground path should be optimized on the top layer. Route pin 4 to GND/RFGND if

the pin functionality is not used.

L2 (10 nH) is an optional filter inductor for AMI pin 4 on Si473x devices and may be placed to prevent VCO energy

from radiating from AMI pin. Place L2 as close as possible to AMI pin 4. Route pin 4 to GND/RFGND if the pin

Rev. 0.8

7

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