Guard traces for sensitive signals in PCB Design - Cell-by-Cell Formula Trace

Concept Flow

Signal Data Table

+-------------------+------------------+------------------+---------------------+
| Signal            | Trace Length (mm)| Noise Level (mV) | Guard Trace Present  |
+-------------------+------------------+------------------+---------------------+
| Sensitive Signal 1 | 50               | 10               | Yes                 |
| Sensitive Signal 2 | 70               | 15               | No                  |
| Sensitive Signal 3 | 40               | 8                | Yes                 |
+-------------------+------------------+------------------+---------------------+

Formula in Noise Reduction column:
IF(Guard Trace Present = "Yes", Noise Level * 0.5, Noise Level)

This formula halves noise if guard trace is present, else keeps noise same.

We have a table of sensitive signals with their trace lengths, noise levels, and whether a guard trace is present. The concept is to reduce noise by half if a guard trace is present using a simple IF formula.

Formula

=IF(D2="Yes", C2*0.5, C2)

This formula checks if the guard trace is present in cell D2. If yes, it multiplies the noise level in C2 by 0.5 to reduce noise by half. Otherwise, it returns the original noise level.

Step-by-Step Trace

Step	Expression	Evaluates To	Explanation
1	D2="Yes"	TRUE	Check if guard trace is present for Sensitive Signal 1. It is 'Yes', so TRUE.
2	C2*0.5	5	Since guard trace is present, noise is reduced by 50%. Original noise is 10 mV, so reduced noise is 5 mV.
3	IF(TRUE, 5, 10)	5	IF condition is TRUE, so result is 5 mV noise after reduction.

The final noise reduction value for Sensitive Signal 1 is 5 mV.

Variable Tracker

Variable	Value
D2 (Guard Trace Present)	Yes
C2 (Noise Level)	10
Noise Reduction (Result)	5

Key Moments

What does the formula check first?

What happens if the guard trace is present?

What is the noise reduction value for Sensitive Signal 1?

Sheet Trace Quiz - 1 Questions

What does the formula in cell E2 do when D2 is "No"?

A Returns the original noise level

B Returns zero noise

C Halves the noise level

D Doubles the noise level

Key Result

The IF formula checks if a guard trace is present and reduces noise by half if yes, otherwise returns original noise.

Transcript

We start by checking if the guard trace is present in cell D2. Since it is "Yes", the formula multiplies the noise level in C2 by 0.5, reducing it from 10 mV to 5 mV. If the guard trace was not present, the formula would simply return the original noise level. This approach helps us understand how guard traces reduce noise in sensitive PCB signals.