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What Are TRP and TIS? Understanding Over-the-Air Antenna Testing
Antenna TestingAntenna
Quick answer: Involve the antenna engineer early, ideally in the feasibility study or concept phase, while antenna placement and antenna type can still be changed. At that point the antenna engineer can give the most valuable feedback, and the risk of reworking the mechanics and PCB is lower. Share the use case, performance targets, timeline, mechanical and electrical models, materials, placement limitations and any prior designs, and keep the antenna, RF and mechanical engineers in regular contact throughout the project.
Why should antenna design be part of the product project?
Antenna design is as important to a successful project as mechanical and RF design. It is one part of product design and should not be done separately from the other product design targets, so a successful project typically needs close collaboration between mechanical, antenna and RF engineers.
An antenna engineer's work consists of the design work itself and of collaboration and information sharing with the other product engineers. With that collaboration can unnecessary work be avoided and as a result we get an antenna design that suits the product in question. At worst, a lack of communication can lead to unexpected problems or delays in the product timeline.
What information does an antenna engineer need from your team?
For proper antenna design an overall understanding of the product as well as its details is needed. The information typically shared with the antenna engineer is:
- Use case. The antenna engineer should know how, where and for which purpose the product is used. For example, wearable antenna designs must account for the effect of the user's body. This can affect the choice of antenna or even the choice of communication technology.
- Design and performance targets. Targets can be related to distance or to antenna parameters, and they measure how good an antenna solution is. The antenna engineer can also help evaluate appropriate targets.
- Project timeline. The timeline can affect antenna design. Strict and loose deadlines may call for different antenna approaches.
- Mechanical and electrical model. Both models are the basis for antenna simulations. For example, the plastic cover of the product and the PCB can affect antenna performance, and the electrical connections in the mechanics and PCB may also have an impact. When these models are accurate, antenna performance can be predicted more accurately in simulations, and accurate modelling may help avoid several prototyping rounds.
- Materials. The materials used in the mechanics and the PCB should be known, because their RF properties can heavily affect antenna performance. The choice of materials can be discussed with an antenna engineer.
- Limitations in antenna placement. Antenna placement within the product affects the achievable RF performance, but some locations can be obstructed by mechanical or electrical requirements. Knowing these limitations early saves the antenna engineer unnecessary work.
- Prior designs. If there are earlier designs, comparing their performance with the planned product can give a figure of merit for sufficient performance. Measuring and simulating a prior design may also help predict the performance of the current product more accurately.
How should antenna, RF and mechanical engineers work together?
The antenna engineer should work inside the design process together with the mechanical and RF teams. This keeps product design smooth and avoids additional delays. Good practices include:
- Agree the starting point. At the beginning, the antenna engineer should receive the information described above. The performance targets in particular should be discussed and agreed, so that the design work starts in the right direction for the product's needs.
- Update progress regularly on both sides. Regular meetings, for example weekly, to check the status of work between the antenna, mechanical and RF teams enable constructive dialogue. They avoid unnecessary surprises, reduce the risk of the antenna design going in the wrong direction and keep engineers from different fields aligned with each other's work.
- Document progress. Like any successful project, this one needs proper documentation. When relevant project results and agreed matters are in written form, misunderstandings and miscommunication are avoided. The format can be emails, PowerPoint slides, Word documents and so on; what matters is that the latest project information is available to everyone involved, so that all parties know the current solutions.
- Notify of changes. This applies to all engineers, whether the change is mechanical, RF or antenna related. Seemingly small details can have a large impact on antenna performance.
- Find solutions together. The antenna engineer cannot complete designs without agreement with the mechanical and RF engineers. Some antenna solutions need back-and-forth discussion on how to realise the antennas mechanically and how durable they are from a mechanical point of view.
- Keep a discussion channel open. There should be an easy way for the mechanical, RF and antenna engineers to communicate. A quick channel for questions and answers between regular meetings can speed up the design work.
What does the antenna engineer do in each project phase?
Generally speaking, the antenna engineer should be involved quite early to avoid possible RF performance issues. If high performance is required, antenna design can partly decide the form factor of the product. At a late stage, when the product design is fixed, the antenna engineer has fewer tools to affect antenna performance.
Antenna design can be divided into four phases: feasibility, concept, design and measurements. The antenna engineer may also be needed after the project is completed.
| Phase | Typical situation | Antenna engineer's role |
|---|---|---|
| Feasibility study | Product and use case known; RF feasibility uncertain | Simplified simulations of the space and antenna locations needed to reach the targets |
| Concept phase | Product size and mechanical outlines known; some freedom in antenna placement and type | Works within the remaining freedom; performance targets are discussed and agreed |
| Design phase (detailed design) | Antenna location and type fixed | Realizes the concept-phase performance; watches details such as metal near the antenna and grounding vias |
| Measurement phase (prototype verification) | Prototype built | Verifies the performance, ideally in a single round |
| After the project | Product design changes | Estimates the effect with simulations or additional measurements |
Feasibility study
The product and use case are known, but it is not certain that the intended product is feasible in the RF sense. When the achievable performance is uncertain, the antenna engineer can be involved.
The antenna engineer can use simplified simulations to estimate antenna performance and what is required for the product to be feasible. For example, the product size and the optimal antenna locations can be studied to show whether the project is feasible with its current scope. Accurate information on the mechanical and electrical components is not necessarily needed yet, because the purpose of an antenna feasibility study is to show how much space the antennas need to reach the performance targets. The result can serve as input data for the mechanical and RF engineers.
Concept phase
The overall mechanics, such as product size and mechanical outlines, are usually known, and there is an idea of where the electrical components will be. Depending on the maturity of the project, some aspects of the mechanical and RF design may already be fixed. Typically there is still some freedom in antenna placement and in the choice of antenna type.
In this phase, share the mechanical and electrical limitations, what can still be changed in the product, and the models and materials of the mechanics and electronics. The performance targets should also be discussed and agreed. Information can be shared in regular meetings, through additional discussion channels between engineers and in written documentation of the results and agreed matters.
Design phase (detailed design)
The design is usually largely fixed in both the mechanical and RF sense, and the antenna location and type are fixed. The aim of this phase is to realize the antenna performance achieved in the concept phase, not to improve it.
Details become important here. Small changes in the mechanics or the PCB can degrade antenna performance, for example adding metal to the mechanics close to the antenna or having too few grounding vias. Close collaboration and discussion between the antenna, RF and mechanical engineers is essential at this stage. If the antenna engineer is not included, costly and time-consuming rework may be required, for example on the PCB. Detailed information can be shared through the design and production files for the mechanics and PCBs.
Measurement phase (prototype verification)
The performance of the designed product is verified with antenna measurements. Ideally there is only a single prototyping and measurement round, although depending on the project, several prototyping rounds can be more cost- and time-effective. Early prototyping may reduce uncertainty in the simulation models and provide valuable insight for product development.
Related reading: What Are TRP and TIS? Understanding Over-the-Air Antenna Testing
After the project is completed
The antenna engineer may still be needed after the prototype measurements are over. If the design of the product changes, notify the antenna engineer and discuss the change, because antenna performance can be affected. The effect can be estimated with simulations or with additional measurements of the new product.
What happens if the antenna engineer joins late?
If the antenna engineer is brought in during the design phase, when things are largely fixed, or only after the product has been fabricated, rework is usually required to reach sufficient performance. For example, off-the-shelf antennas may not work well once they are integrated into the mechanics. This can require a custom antenna design, which can in turn mean changes to the mechanics or PCB, delaying the project and increasing costs. Our article on chip antennas in plastic devices describes one example of such integration problems.
In the feasibility study or concept phase, the antenna engineer can give the most valuable feedback on what to do, and the risk of reworking the mechanics and PCB is lower.
It is also good to keep in mind that not all RF problems are related to antennas. There can be EMC/EMI related issues, which may be captured in active measurements.
Frequently asked questions
When is it too late to involve an antenna engineer? Once the product design is fixed, the antenna engineer has fewer tools to affect antenna performance, and reaching sufficient performance usually requires rework. The best time is the feasibility study or concept phase, while antenna placement and antenna type can still be changed.
Can an off-the-shelf antenna be used instead of a custom design? It depends on the product. Off-the-shelf antennas may not work well once they are integrated into the mechanics, and then a custom antenna design may be needed, which can mean changes to the mechanics or PCB, project delays and higher costs.
How many prototype rounds does antenna design need? Ideally one prototyping and measurement round. Depending on the project, several rounds can be more cost- and time-effective, because early prototyping may reduce uncertainty in the simulation models.
Are all RF problems caused by the antenna? No. Some RF problems are related to EMC/EMI, and these may be captured in active measurements.
Bring an antenna engineer into your project early
Radientum has worked with more than 300 customers on over 1,000 projects. Our antenna engineers can join your product project at any stage, alongside your mechanical and RF teams. Book a free 60-minute consultation to talk through your product.
Original text by Riku Kormilainen rewritten for the new webpage by Maria Herronen
