The antenna coil structure consists of two sets of unconnected coils wound around a magnetic rod, forming the antenna coil used in the input circuit of a radio. Two independent coils form a high-frequency transformer. Soft magnetic ferrite materials are mainly classified into manganese zinc ferrite, nickel zinc ferrite, high conductivity manganese zinc ferrite, etc;
The antenna magnetic rod coil is a high-frequency transformer composed of a magnetic rod and a coil. The coils you see wound on a magnetic rod are usually divided into two groups:
Primary coil: forms a tuning circuit with a variable capacitor, used to select the radio frequency you want to listen to.
Secondary coil: By coupling, the selected signal is transmitted to the next stage circuit of the radio for amplification processing.
The working principle can be decomposed into two key steps:
1. Collection and aggregation (function of magnetic rod): The magnetic rod is made of a soft magnetic material called ferrite, which has a high magnetic permeability. You can imagine it as a "funnel" specifically designed to collect magnetic field lines. When electromagnetic waves pass through space, the magnetic rod can efficiently "attract" and "gather" the scattered magnetic field lines in a wide range around it onto itself.
2. Induction and enhancement (the role of coils): Due to the magnetic field lines being tightly confined within the magnetic rod and passing through the coils wound around the magnetic rod, according to the principle of electromagnetic induction, much higher voltage signals can be induced in the coils than without the magnetic rod. This is equivalent to greatly enhancing the antenna's "perception ability" for weak signals, thereby significantly improving the receiving sensitivity.
Structure and Materials
Simply put, it is a magnetic rod made of a special magnetic material (ferrite) inserted into the hollow coil. This magnetic rod plays the role of an "energy harvester" and a "signal amplifier", greatly enhancing the coil's ability to receive electromagnetic waves.
Magnetic rod: Depending on the operating frequency, the material of the magnetic rod also has a division of labor.
Medium wave magnetic rod: usually black in color, made of manganese zinc ferrite, with high magnetic permeability, suitable for lower frequencies (~1.6MHz).
Shortwave magnetic rod: usually brown or gray in color, made of nickel zinc ferrite, with low magnetic permeability, but can operate at higher frequencies (~30MHz) with low high-frequency losses.
Coil: In order to reduce the losses caused by the "skin effect" of high-frequency currents, medium wave coils are often wound with multiple strands of yarn. Short wave coils are commonly wound with silver plated copper wire (leaving gaps between circles) to further reduce losses and distributed capacitance.
Application field
Wireless communication, features: miniaturization, high efficiency, anti-interference, applied to IoT sensors, underground/pipeline communication, near-field communication (NFC)
Wireless charging, features: improves transmission efficiency, reduces device size, applied to consumer electronics (mobile phones, watches), medical implant devices, industrial sensors
New antenna, features: breaking through traditional size limitations, achieving ultra-low frequency communication, applied in ground penetrating communication, pipeline robot positioning, underwater communication
