30 September 2019
A simple guide to impedance matching for RF
13 February 2017
Problem-solving and product design/engineering: they go together hand-in-hand. Engineers and designers are presented with briefs that push the boundaries of possibility - after all, that’s where the biggest market opportunities are - but it’s not just the pressure of marketers and project managers that they are working under when designing 3G wireless antenna products. Network carriers and regulatory bodies also require high levels of performance to even allow a product to go to market.
Devices are becoming smaller, thinner and lighter whilst featuring more components and features. However, high-level wireless performance is now an expectation for consumers. Balancing expectations of the final form factor, whilst retaining high performance, requires great care.
As a rule of thumb, the shorter the frequency; the longer the antenna needs to be. This causes real difficulties in small, portable devices that need to connect to cellular networks. Therefore, to pass minimum requirements for network providers you’ve got a decision to make: do you tell marketing that the product isn’t going to be as small as they want, or do you make sacrifices on performance?
The goal of any antenna design-in is to achieve high levels of performance within a small form factor. This requires you follow best practice for antenna integration process, meaning that “adding in” an antenna at the last minute will cause serious compromise on performance that could cost a device network approval.
If you’re watching a movie at a cinema or theatre, the last thing you want is a shouty neighbour having a phone conversation next to you. It’s the same principle with wireless antenna. When situated next to each other, the broadcasting and receiving antenna may get involved in a fight - which just culminates results in unnecessary power consumption and inefficiency.
This isn’t good for efficiency antenna integration, impacting on radiation patterns and matching elements. Isolated and uncoupled antenna will achieve higher levels of performance and quieten the noisy neighbour and make the receiving antenna more efficient.
Factors such as housing material selection and component placement can impact the matching / tuning of your antenna. It’s important you take necessary steps to prevent this.
The 3G network is so popular because of the availability of connectivity on-the-go. However, the very nature of devices connected to this network can negatively impact the efficiency of a wireless device - in a number of ways.
Performance can easily be inhibited through in-situ use; obstructions such as human body, thick walls and a weak signal can cause difficulties. You can’t always predict exactly how your device will be used, so you will have to intelligently integrate your antenna to overcome the challenges of in-situ performance.
Considering the actual use of your device, designing it around that and then testing your device’s in-situ performance will help you eliminate most of the issues that could prevent you from passing network approval.
It’s the stuff of nightmares, failing to pass a network approval test. Once it’s out of the way, it’s an incredibly relieving feeling. Failure to meet the standards for network approval can pose big issues in the timeline for getting to market, the project budget and potentially even require a total redesign of the device.
Following best practice should take you some way to achieving considerably higher performance than network carriers require to pass. Following best practice isn’t always possible, particularly for small SMART devices, so consider how you are integrating your antenna as early in the design process as possible.
Gaining network approval in the USA is slightly harder than in Europe, due to the geographic differences and availability of broadcast masts. So if the device is to be launched in North America, bear this in mind.
Network approval is probably the largest hoop you’ll need to jump through, but if you are designing a device that could possibly launch in North America, there is another obstacle you’ll need to hurdle: PTCRB Certification.
The PTCRB testing criteria involve everything from overall efficiency to power consumption of the SIM-card. Although the requirements are intended to ensure cellular products perform efficiently, following best practice in antenna implementation will almost certainly secure your certification so that your product may launch in the US - the most common issue is actually implementing a sizeable enough ground plane.
If you have been tasked with designing a 3G wireless product then you have a lot to consider, and a lot of pressure to deal with to get it right - from network carriers, regulatory bodies and customers, each expecting high levels of performance. Getting it right can be a challenge, but not if you have the right guidance to call on.