Flush, Water Drop, and Horn Antennas: Structure, Beam, and Selection Differences
In radar level meter selection, the antenna type directly affects the beam angle, measurement blind zone, anti-adhesion capability, and installation space. Flush, water drop, and horn antennas are three common structures. This article compares their differences from a hardware perspective to help engineering and technical personnel and procurement quickly determine applicable scenarios.
1. Flush Antenna
The flange mounting surface of a flush antenna is completely flat. The microwave lens is embedded inside the flange, with no component extending into the tank or pipe. The lens is a thin flat fluoroplastic microwave window, with no protrusion and no cavity overall.
Beam and Blind Zone
- Beam angle: The largest among the three, with high microwave divergence and the weakest focusing capability.
- Near-field blind zone: The smallest, with almost no measurement dead zone.
Mechanical and Surface Characteristics
- No protruding structure, no collision risk.
- Flat surface, no drainage curvature.
- No internal retention cavity.
Signal Attenuation and Installation
Microwaves are emitted vertically from a flat surface. Medium foam or deposits will directly and completely cover the emitting surface, resulting in the most obvious blocking attenuation. During installation, the smallest specification flange or short sleeve is suitable. There is no requirement for installation depth, and the nozzle length is not restricted.
2. Water Drop Antenna
The water drop antenna uses an integral solid one-piece lens, protruding outward into the cavity in an arc-shaped water drop form. It is solid with no hollow cavity, and its outer surface is a continuous smooth arc streamline.
Beam and Blind Zone
- Beam angle: Medium to small, with focusing capability better than flush type and weaker than horn type.
- Near-field blind zone: Very small.
Mechanical and Surface Characteristics
- Arc-shaped protrusion with a natural drainage curved surface.
- Solid structure, no dirt-hiding cavity.
- Has protruding length, with collision interference risk.
Signal Attenuation and Installation
Deposits and condensate on the arc surface slide off automatically, making it difficult to completely cover the core microwave emitting area. Blocking attenuation is weaker than that of the flush type. During installation, standard DN50/DN80 flanges are commonly used, and a small amount of protruding space needs to be reserved.
3. Horn Antenna
The horn antenna consists of a conical hollow metal cavity plus a front-end lens. It has an internal hollow conical cavity and protrudes significantly outward overall. The cavity forms a microwave reflection and convergence channel.
Beam and Blind Zone
- Beam angle: The smallest among the three, with the strongest microwave convergence, the best directivity, and the highest long-distance signal concentration.
- Near-field blind zone: The largest among the three.
Mechanical and Surface Characteristics
- Hollow inner cavity with an enclosed recessed space.
- Longest horn protrusion, with the highest collision interference risk.
- Inner cavity easily retains fluid and moisture.
Signal Attenuation and Installation
The hollow cavity is highly prone to accumulating impurities and water, directly blocking the microwave path. The probability of signal attenuation and instability is much higher than that of solid antennas. During installation, a large-diameter flange (starting from DN80) must be used. A longer nozzle space needs to be reserved, and an external purge interface can be connected.
Core Dimension Hardware Comparison Table (No Medium Scenario)
| Comparison Dimension | Flush Antenna | Water Drop Antenna | Horn Antenna |
|---|---|---|---|
| Structural Form | Flat embedded lens, no protrusion | Solid arc protrusion | Hollow conical protrusion |
| Beam Angle | Largest | Medium to small | Smallest |
| Focusing Capability | Weakest | Medium | Strongest |
| Near-field Blind Zone | Smallest | Very small | Largest |
| Anti-blocking Capability | Worst, attenuation once surface is covered | Better, deposits slide off easily | Poor, inner cavity easily blocked |
| Collision Risk | None | Yes | Highest |
| Mounting Flange | Smallest specification | DN50/DN80 | Starting from DN80 |
| Purge Interface | Not supported | Not supported | External connection possible |
Minimal Summary: Pure Hardware Differences
- Flush type: Does not protrude, wide beam, no blind zone, vulnerable to surface film blocking.
- Water drop type: Solid arc protrusion, moderate beam, self-draining, not easily fully covered by deposits.
- Horn type: Hollow long conical, most concentrated beam, large blind zone, inner cavity easily accumulates debris, supports purging, only large-diameter installation.
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