When engineers select an EMI ventilation panel, the first specification they often look at is shielding effectiveness.
90 dB.
100 dB.
110 dB.
The higher number appears to be the better choice.
But this approach can create problems.
A honeycomb waveguide window is not simply a component that provides a certain shielding number. It is part of the ventilation system, mechanical structure and electromagnetic shielding boundary.
If the wrong product is selected, the system may have excellent shielding performance in a test report but still fail to meet the actual requirements of the enclosure.
The better approach is to evaluate the entire application.
1. Start With the Frequency Range
The first question should not be:
“How many dB do you need?”
It should be:
“At which frequencies do you need that shielding?”
Electromagnetic shielding effectiveness changes with frequency.
The geometry of the honeycomb cell determines how electromagnetic energy interacts with the structure.
Cell aperture and cell depth are therefore closely related to the frequency performance.
For some applications, the main concern may be low-frequency magnetic fields.
For others, the critical range may be hundreds of MHz or several GHz.
A product optimized for one frequency range should not automatically be assumed to provide the same performance at another frequency.
This is especially important when the enclosure is used for RF testing, microwave equipment, military electronics or communication systems.
Noordin Etech waveguide window designs can be configured for different shielding requirements, with product data including performance across multiple frequency ranges depending on the specific construction. For example, one nickel-plated configuration specifies performance from 14 kHz through the GHz range.
The correct specification therefore needs to include the actual frequency range.
2. Cell Size Is an Electrical Parameter
A honeycomb cell may look like a mechanical opening.
Electromagnetically, however, it behaves like a small waveguide.
This means the cell aperture is an important electrical parameter.
Smaller cells generally provide stronger electromagnetic restriction.
But smaller does not automatically mean better.
Reducing the cell aperture can affect:
- Airflow
- Pressure drop
- Manufacturing cost
- Cleaning
- Mechanical durability
- Required panel area
Therefore, cell size should be selected according to the required combination of shielding and ventilation.
This is why a professional specification should identify the cell size instead of simply describing the product as an “EMI vent.”
3. Panel Depth Also Matters
Two honeycomb panels may have the same cell diameter but different depths.
Their electromagnetic performance may therefore be different.
The deeper the waveguide structure, the longer the electromagnetic path through the cell.
This is one of the fundamental reasons honeycomb waveguide windows work.
A shallow perforated plate and a deep honeycomb structure are not electrically equivalent, even if their openings look similar.
For high-performance shielded applications, the honeycomb depth should be considered together with cell aperture and target frequency range.
Some Noordin Etech honeycomb waveguide configurations use a 45 mm honeycomb thickness with 3 mm or 5 mm cell diameters.
4. Airflow Cannot Be an Afterthought
The purpose of a ventilation window is still ventilation.
This sounds obvious, but it is easy to overlook when the primary project objective is electromagnetic shielding.
A shielded room may contain:
- Power amplifiers
- RF generators
- Electronic test equipment
- Computers
- Battery systems
- High-power loads
All of these can generate heat.
If the ventilation panel creates excessive pressure drop, the HVAC system may need additional fan capacity.
That increases system cost and power consumption.
This is why open area is an important specification.
For example, Noordin Etech EMI shielding honeycomb vent panels specify an approximately 95% cell open rate.
A good design therefore looks at both:
Shielding effectiveness
and
Airflow performance.
Neither should be evaluated independently.
5. The Frame Is Part of the Shield
Another common mistake is to focus entirely on the honeycomb core.
Imagine a honeycomb panel with excellent RF attenuation.
Now imagine that it is installed into a large metal opening with an electrically poor connection around the perimeter.
The shielding performance of the overall system can be much lower than the performance of the honeycomb itself.
The frame therefore plays an important role.
The designer should consider:
- Frame material
- Mounting method
- Contact surface
- Conductive gasket
- Fastener arrangement
- Surface treatment
- Mechanical flatness
For shielded rooms and chambers, the perimeter interface can be just as important as the honeycomb structure.
6. Conductive Gaskets Matter
A waveguide window may be mechanically installed correctly but still have electrical discontinuities around the frame.
This is where conductive gaskets can become important.
Depending on the application, the interface may use:
- Monel wire mesh gasket
- Conductive elastomer
- Neoprene environmental gasket
- Fingerstock
- Other EMI-compatible sealing solutions
Noordin Etech honeycomb vent panels can be supplied with conductive and environmental gasket options depending on the application.
The goal is simple:
The ventilation panel should become part of the shielding boundary, not simply be attached to it.
7. Surface Treatment Is Not Only About Appearance
Different surface treatments can be selected according to environmental and mechanical requirements.
Typical options include:
- Chromium
- Tin
- Nickel
- Flame-resistant paint
For telecom and outdoor equipment, environmental resistance can be important.
For military shelters, mechanical durability and appearance may both matter.
For indoor EMC chambers, conductivity and compatibility with the surrounding shielding structure may have higher priority.
The correct surface treatment should therefore be selected based on the actual operating environment.
8. Mechanical Installation Must Be Considered Early
A technically suitable waveguide window can still become difficult to install if the mechanical design is not confirmed in advance.
Before ordering, engineers should confirm:
- Overall panel dimensions
- Cut-out dimensions
- Frame dimensions
- Mounting holes
- Mounting direction
- Panel thickness
- Required gasket
- Airflow direction
- Available installation space
Standard dimensions may be convenient for some projects, while custom dimensions may be necessary for others.
Noordin Etech currently lists standard configurations such as 300 × 300 mm, 300 × 600 mm, 400 × 400 mm, 500 × 500 mm and 600 × 600 mm for one honeycomb waveguide configuration, while customized appearance and dimensions are also available.
Confirming these dimensions before fabrication can prevent expensive modifications to the shielded enclosure later.
9. Do Not Ignore Environmental Requirements
The operating environment can change the specification.
An indoor EMC chamber may have relatively controlled conditions.
An outdoor telecom enclosure may face:
- Rain
- Dust
- Humidity
- Temperature changes
- UV exposure
A military shelter may require additional mechanical protection.
A medical or laboratory application may have different cleanliness and sealing requirements.
Therefore, “EMI shielding vent” is not a complete specification.
A better requirement would be:
EMI shielding + airflow + mechanical + environmental + installation.
10. Shielding Performance Must Be Tested Correctly
Another important issue is how shielding effectiveness is measured.
A product may be advertised as having very high shielding effectiveness, but engineers should confirm:
- Frequency range
- Test method
- Test configuration
- Panel size
- Installation condition
- Whether the value applies to the component or complete enclosure
Noordin Etech’s waveguide window category references standards such as MIL-STD-285 and IEEE 299 for shielding evaluation.
The test method should always be considered together with the number.
A “100 dB” value without frequency and test conditions is incomplete information.
11. The Best Design Is a System-Level Design
A honeycomb waveguide window should be treated as one part of the shielding system.
The complete system may include:
Shielding panel → frame → gasket → waveguide window → HVAC system → fan → surrounding structure.
A weakness in any one of these interfaces can reduce the final result.
This is why experienced EMC engineers do not simply choose the product with the highest dB rating.
They look at the complete application.
Final Engineering Checklist
Before approving a honeycomb waveguide window, ask:
Frequency
- What frequency range needs to be attenuated?
- Is low-frequency performance important?
- Is microwave performance required?
Shielding
- What shielding effectiveness is required?
- At which frequencies?
- What test standard is applicable?
Airflow
- What airflow rate is required?
- What pressure drop is acceptable?
- What is the available ventilation area?
Mechanical
- What is the opening size?
- What is the panel thickness?
- How will the window be mounted?
Interface
- Is a conductive gasket required?
- How will electrical continuity be maintained?
Environment
- Indoor or outdoor?
- Is corrosion resistance required?
- Is flame resistance required?
Finish
- Chromium?
- Tin?
- Nickel?
- Spray-painted finish?
Once these questions are answered, product selection becomes much more straightforward.
The goal is not to buy the honeycomb waveguide window with the highest number on the datasheet.
The goal is to select the right electromagnetic structure for the actual shielding and ventilation requirements of the system.
That is the difference between component selection and EMC engineering.
Learn more about Noordin Etech waveguide windows:
Noordin Etech Waveguide Window Products
For more information：
Why Honeycomb Waveguide Windows Can Ventilate While Blocking EMI
