It’s rare that a product specification will be written by someone with a robust knowledge of product engineering. New product ideas are usually the work of research and competitive analysis from marketers and senior managers, then financial managers appraise risk and allocate budgets.
Each of these teams have different goals in mind: marketers want unique features, directors want profit, and financial managers want to minimise risk and cost. It’s often required that products are small, low-cost and achieve high performance - it’s up to engineering to design the heart of these products: the electronics.
We were approached by a company who were looking to design a portable LTE Wireless Router and they weren’t entirely sure what kind of performance to expect. Using this type of antenna brings it’s own problems, too.
Frequency determines antenna, antenna determines product design
LTE product designs can be extremely difficult to master as you will be dealing with an antenna that supports a frequency range from 698 - 2690MHz. For true LTE you also need 2 antennas - MIMO (Multiple in - Multiple out).
There are two main issues with this type of design:
- 100-120mm of host ground plane is needed for low band frequencies to achieve good performance and antenna efficiency
- MIMO designs often face isolation issues, as multiple antennas working on the same frequencies tend to cancel each other out
Antenna performance for cellular/LTE applications is extremely important as devices will need to pass network approval before they can go to market, particularly in the US before they will be approved for use on major networks such as AT&T. PTCRB certification was also required for this company designing the LTE Wireless Router.
Position vs. Performance
Passive testing will enable engineers to find the optimum position of an antenna for performance. The engineer provided Antenova with 3D models of the initial designs of the router, so our own engineers were able to mock up the outer casing and use a bare host PCB to run tests on.
These passive tests found the product to be too short. The host PCB would need to be elongated in order to increase performance, as the length of the product at that time would meant PTCRB certification was borderline.
Further tests were conducted to find a solution to the required size increases needed to comfortably pass the PTCRB certification, which was vital for their product to eventually go to market.
Timely testing saves aggravation
Conducting tests before designs are formally approved can help save later aggravation and prevent time from being wasted redesigning aspects of the device. For the LTE Wireless Router, the device length was increased by 12mm to ensure performance would not only attain PTCRB certification, but would provide a good level of performance for end users.
After the design was completed, the Antenova engineers assisted by reviewing Gerber files and recommended small layout changes before any time and money was sunk in building prototyped devices.
Working with Antenova engineers throughout the early stages of design, all the way through to when Gerber Files were finalised allowed the company to streamline their design cycle, saving budget, reducing engineering costs and reducing the overall time to market - all whilst creating a product with the right level of performance without any technical disaster.
