be described as having “immunity to nearby materials” but this is generally either untrue or the antenna has low efficiency. Directional antennas (like a microstrip patch) and antennas using new band-gap technologies can have limited interaction with nearby materials but these are unusual situations. Most often, the integrated antenna is a structure that includes the product within its near field, so interaction is inevitable.
The antenna/ground plane interaction creates a complex situation where the antenna impedance (and impedance bandwidth), overall efficiency, and radiation pattern all depend heavily on the characteristics of the entire device. Intelligent implementation of the antenna must be holistic in approach, involving the entire device and considered from the very beginning of the product design. As Larry Zibrik of Sierra Wireless told us during an interview for this paper “An OEM must realize that, almost without exception, the industrial design of the device will be impacted by the antenna design. Understanding and anticipating this fact from the very beginning of the design process is critical to success.” For obvious reasons, the conductive parts of the device have the largest influence on the antenna, but non-conductive components (enclosure, PCBs, etc.) will also affect antenna design and performance.
Manufacturers of radio modules are an excellent source of antenna element design or selection and antenna location within the device. These manufacturers have likely seen similar devices and are therefore familiar with both the electrical and mechanical design issues, as well as the manufacturing issues of particular antennas. Obtaining antenna design and implementation advice from the radio module manufacturers is worth the effort and cost involved, especially considering the very high costs associated with a product re-design after the failure of FCC regulations, PTCRB, or carrier requirements. The following sections discuss antenna types and configuration. The discussion assumes that that the antenna is a dual-band device.
4.1 Embedded vs. External
Antenna Fundamentals – Technical Brief