Included in at least one reviewed higher-education syllabus.
S4-2.2 Antenna Analysis: Dipoles & Loops
You can derive fields for the infinitesimal dipole, analyse the half-wave dipole and loop antenna, and compute radiation resistance and directivity.
The infinitesimal dipole is the hydrogen atom of antenna theory: nobody builds one, but every real antenna is analysed by summing them. This topic derives its fields, then treats the half-wave dipole and the loop, computing radiation resistance and directivity for each. It sits between the vocabulary unit and arrays because superposition of these results is exactly how arrays are analysed next. The number worth keeping is the half-wave dipole's seventy-three ohm radiation resistance — it is the historical reason so much radio hardware settles around fifty to seventy-five ohms.
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Analysis of the infinitesimal dipole
The infinitesimal dipole is the hydrogen atom of antenna theory: nobody builds one, but every real antenna is analysed by adding many of them together. The algebra is dense and it is the foundation the rest of the unit stands on.
Half-wave dipole: fields, radiation resistance, directivity
The half-wave dipole is the antenna that actually gets built, and its radiation resistance of about seventy-three ohms is the reason so much radio hardware is designed around fifty and seventy-five ohms. This is where theory meets the connectors on the bench.
Loop antenna analysis
A loop antenna radiates through circulating current rather than a straight wire, which gives it a different pattern and a very different radiation resistance. Small loops turn up constantly in receivers and tags.
Calculation of radiation resistance and directivity for each
Radiation resistance is the equivalent resistance that would absorb the power an antenna actually radiates, and directivity says how sharply it does so. Computing both for the standard antennas is the numerical skill this unit is examined on.
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