The third instalment of our wireless design cycle webinar explores the Gerber review and design test steps of the cycle. Antenova's antenna applications specialist, Geoff Schulteis, focuses on the key considerations for making these stages a success.
Gerber design review
Prevention is better than cure. Following the completion of the first version of a board design, the designer can make a number of checks to ensure wireless performance is well optimised. There are several key questions to address:
Transmission Lines
1. Does the device use a suitable transmission line?
2. Does the impedance of the transmission line match the source and RF circuitry?
3. Are transmission lines short and without corners (i.e. using chamfered edges where possible)?
Matching Circuit
4. Have you incorporated a matching circuit (such as a Pi matching circuit) within your RF circuitry?
5. Do the values of your matching circuit enable an impedance match?
Via placement
6. Usage: Are vias used to form a ground fencing?
7. Spacing: the spacing between two vias should exceed 5% of the wavelength of the RF signals.
8. SeparationWW: Are separate vias used for each pin and pad?
Design test
Verifying a device operates as expected in the hands of consumers is a step not to be missed. In fact, all cell carriers and network operators will conduct testing on devices that are to launch on their network. In North America, due to geographic reasons, this testing is extensive – and the passing criteria is renowned for being difficult. 3 out of 5 devices are thought to fail certifications at the first attempt.
Not everyone has access to sophisticated anechoic testing facilities – but finding a vendor who has can drastically reduce the time and money spent trying to achieve certifications. Over-the-Air testing can allow a designer to assess the performance of a design, all without delaying a time-to-market date.
