The Ground Plane Mirror

Contributing Author Bülent Solan, Co-Founder Quarterwave

The ground plane principle is crucial in all antenna technologies, from resonant structures on a PCB to chip antennas or resonator antennas. In resonant structures, it acts as the “second pole,” influencing radiation just as much as the radiator. For chip and resonator antennas, the ground plane itself becomes a radiating element.

For small antennas in portable devices or compact solutions, ground plane size and properties are key considerations. An undersized ground plane reduces efficiency and weakens antenna performance.

Optimizing Antenna Performance with Characteristic Mode Analysis (CMA)

The geometric dimensions of a PCB directly influence which modes can be excited on a ground plane. Precise design and mode analysis are essential, and at Quarterwave, we use Characteristic Mode Analysis (CMA) to identify the frequency ranges where the antenna achieves maximum efficiency. CMA helps better determine how PCB dimensions affect radiation behavior.

Invisible Power, Visible Impact

Particularly useful when design goals are not fully met, CMA allows for performance compromises. It guides the selection to define ideal antennas for specific applications and optimizes antenna placement. In MIMO applications, CMA improves decoupling through orthogonal modes.

A clear example of this is reflected in PCB sizes specifically developed and optimized for Quarterwave chip antennas. In tracker applications, GPS data is captured and transmitted to the cloud via NB-IoT. These solutions require both a GPS antenna and a suitable LTE antenna that is optimized for operation in LTE bands B20 (800 MHz) and B8 (900 MHz). Our innovative solution integrates both functionalities in a single chip antenna supporting both GPS and NB-IoT bands.The challenge with low frequencies is that smaller PCB sizes, and consequently smaller ground planes, impair antenna performance. This makes the design of small antennas for these frequencies particularly challenging, as the limited size of the ground plane does not provide enough support to ensure optimal antenna performance.

The Future of Efficient Antennas

To overcome the challenges of small ground planes, Quarterwave has developed a solution that significantly enhances antenna efficiency. Quarterwave’s chip antenna is purpose-built for compact PCBs, roughly the size of a matchbox, where achieving sufficient efficiency is particularly challenging. Conventional chip antennas and similar technologies in the size range, especially for lower cellular bands, often have efficiencies of no more than 15%. Another challenge is their narrowband nature.

Quarterwave’s chip antenna is a solution that surpasses conventional designs by incorporating an intelligent matching circuitry, boosting efficiency by up to 30% across multiple bands. This allows for optimization for the B20 and B8 bands within a highly compact form factor.

Conclusion: Ground Plane – Key to Antenna Efficiency

A sufficiently large and continuous ground plane is essential to maximize efficiency and achieve optimal radiation characteristics, particularly when integrating antennas into portable devices and low-frequency applications.

At Quarterwave, leveraging CMA enables custom antenna designs that exceed standard solutions. Utilizing innovations like Quarterwave chip antennas and intelligent matching circuits delivers superior efficiency and ensures small antenna integration in complex applications won’t compromise performance.