Antennas#

Where circuits meet physics.

An antenna is the interface between guided waves (on transmission lines) and free-space radiation. It converts electrical energy into electromagnetic waves and vice versa. Unlike most circuit components, an antenna’s behavior is determined by its physical shape, size relative to wavelength, and surroundings.

Antenna design is where circuit theory meets electromagnetic field theory — and where the gap between simulation and reality is widest. Ground planes, enclosures, nearby objects, and even the person holding the device all change the antenna’s behavior in ways that schematics can’t predict.

What This Section Covers#

• What an Antenna Actually Does — The physical mechanism of radiation, reciprocity, gain, and how to read radiation patterns.
• Common Antenna Types — A practical survey of dipoles, monopoles, loops, patches, Yagis, and their tradeoffs.
• Radiation Resistance & Efficiency — Understanding what limits how much transmit power actually gets radiated.
• Polarization & Orientation — How wave orientation affects signal strength and when it matters in practice.
• Ground Planes & Counterpoise — The often-misunderstood “other half” of monopole antennas and PCB antenna designs.
• Antenna Tuning & Trimming — Practical techniques for adjusting antenna resonance and impedance match.
• Measuring Antennas Without a Lab — What a NanoVNA and field measurements can reveal, and what requires serious facilities.
• Antennas in Enclosures & Real Environments — Why antenna performance changes dramatically inside a product or a room.