This item checks for the distance and existence of bead component in signal pattern.

In order to prevent noise coupling to or form other signals, the designer may assign bead components in signal pattern. The distance from IC to bead component should be kept as short as possible. A ferrite bead is a passive electric component used to suppress high frequency noise in electronic circuits. It is a specific type of electronic choke. Ferrite beads employ the mechanism of high dissipation of high frequency currents in a ferrite to build high frequency noise suppression devices.

In addition to small stray capacitance, ferrite bead inductors have another excellent feature. At high frequencies, this type of inductor works not as an inductor but as a resistor and dissipates noise in the form of heat.
  • Item: Enter item name.
  • Net: Select a target net group that nets in the group that needs bead components.
  • Bead Comp: Select a component group that components in the group will be used as bead components.
  • Start Comp: Select a starting component group.
  • Distance: Assign a reference distance of bead components from the starting component.


  • PollEx DFE reports No Filter if there is no bead component.
  • PollEx DFE reports No Start Comp if there is no starting component.
  • If there is a bead component but it is placed too far from the starting component, PollEx DFE reports Distance Fail and measured distance as well as the reference distance.
Bead component is an L-element type component of power line to protect noise from power. To the signal which is very sensitive to noise, the designer can use bead component for EMI to filter out unnecessary high frequency noise.

Figure 1.
Characteristics of ferrite bead inductors allow you to remove high frequency noises by converting them to heat.
Table 1. EMI Filter Usage
Usage Specification Type Recommentation
Power Line BLM11P (0.5-1A) Ferite Bead IC Power Line
NFM2012P (2A) 3-Terminal Capacitor
BLM41P (1-6A) Ferite Bead Power Circuit
NFM46P (6A) 3-Terminal Capacitor
Signal Line BLM10A (10~1kΩ) Ferite Bead Weak Ground Pattern
BLA3216A (30~1kΩ) Array-Type Ferite Bead
PLM3216K (280Ω) Common Mode Choke
GRM36 2-Terminal Capacitor Strong Ground Pattern
NFM39R (22~2200pF) 3-Terminal Capacitor
NFM60R (22~2200pF) T-Type 3 Terminal Capacitor
NFA3216D (22~2200pF) Array Type
High Speed Line NFM51R (10M~500MHz) 3-Terminal Capacitor Normal Mode Noise
NFM839R (22~10Ω, 10~100pF) RC-Type 3 Terminal Capacitor
NFA3216 (6.8~100Ω, 10~100pF) RC Array Type
BLM11B (5~500MHz) Ferite Bead
PLM250 (350~4kΩ) Common Mode Choke Common Mode Noise

Characteristics of Analog and Digital Signals

Because analog signal handles change of magnitude in signal, if noise is overlapped on signal, it results in distortion of signal and changes the original signal. In this case, it is impossible to recover the original signal. Digital signal can be recovered from the changes made by noise.

Figure 2.