A microwave antenna transmits and receives electromagnetic energy at microwave frequencies, typically from about 1 GHz into the millimeter-wave range. It converts guided RF energy from a coaxial cable, microstrip line, or waveguide into a radiated wave; in receive mode, the same process works in reverse.
Antenna type, aperture, polarization, impedance matching, and operating frequency determine gain, beamwidth, efficiency, and usable bandwidth.
How Does a Microwave Antenna Work?
Transmit Mode
An RF transmitter delivers power through a coaxial cable, microstrip line, or waveguide to the antenna feed. Current and electric-field distributions on the radiating structure produce electromagnetic waves. Horn antennas and reflector antennas form narrow beams, while arrays control the beam through amplitude and phase across multiple elements.
Receive Mode
An incoming electromagnetic wave induces voltage and current at the antenna terminals. The feed network transfers this signal to the receiver for filtering and processing. Because most passive antennas are reciprocal, their transmit and receive patterns are essentially the same at the same frequency and polarization.
Directivity, Gain and Beam Control
Directivity describes how strongly an antenna concentrates radiation in a particular direction. Gain also includes radiation efficiency, so gain is always lower than or equal to directivity when both use the same reference. A larger effective aperture generally produces higher gain and a narrower beam.
For an aperture antenna, the approximate directivity is D ≈ 4πηA/λ², where η is aperture efficiency, A is physical aperture area, and λ is wavelength.
Practical gain depends on aperture efficiency, conductor and dielectric losses, impedance matching, surface accuracy, and feed illumination. Parabolic reflector antennas can provide more than 30 dBi of gain for point-to-point and satellite links, depending on dish diameter, frequency, and efficiency.
Key Components of a Microwave Antenna System
A complete microwave antenna system combines the radiating structure with a low-loss feed, matching and polarization components, and the correct RF interface.
| Component | Function | Examples |
|---|---|---|
| Radiating structure | Converts guided RF energy to free-space waves and back again | Horn, patch, slot, reflector |
| Feed network | Transfers RF energy with controlled loss and phase | Waveguide, coaxial cable, microstrip |
| Matching and polarization components | Control reflections and polarization | Transitions, polarizers, OMTs |
| RF interface | Connects the antenna to the transmitter or receiver | Coaxial connector or waveguide flange |
Common Microwave Antenna Types
- Horn antennas: Offer predictable radiation patterns, broad bandwidth, and high power handling for testing, radar, and reflector feeds.
- Microstrip antennas: Provide a compact, low-profile solution for wireless terminals, arrays, and integrated systems.
- Reflector antennas: Produce high gain and narrow beams for satellite, telemetry, and long-distance links.
- Array antennas: Combine multiple elements to increase gain or electronically control the beam.
Frequency, Matching and Performance
At lower microwave frequencies, patch, array, log-periodic, spiral, and reflector antennas are selected according to bandwidth, size, coverage, gain, and installation requirements.
At higher microwave and millimeter-wave frequencies, waveguide-fed horn and reflector antennas are widely used because they offer low feed loss, predictable polarization, and accurate beam control.
Good impedance matching reduces reflected power. The acceptable VSWR or return loss depends on the system specification; common design targets include VSWR ≤ 1.5 or return loss ≥ 14 dB, but these are not universal limits.
Common Microwave Antenna Applications
- 5G and point-to-point links: Patch arrays, horn antennas, and reflector antennas support directional links, beamforming, and high-capacity backhaul.
- Radar and sensing: High-gain antennas and arrays provide the angular resolution and beam control needed for detection, tracking, automotive radar, and measurement systems.
- Satellite communication: Reflector and horn antennas provide high gain and controlled polarization for ground terminals, telemetry, and tracking.
- Test and measurement: Standard-gain horns and other calibrated antennas support chamber testing, field measurements, and antenna characterization.
For communication links, reflections, obstructions, weather, and relative motion can change signal amplitude and phase, so link design should account for wireless channel fading.
How to Choose a Microwave Antenna
Start with the operating frequency and required bandwidth, then balance electrical performance with the mechanical and environmental limits of the system.
- Frequency and bandwidth: Confirm that the antenna covers the full operating band with acceptable matching.
- Gain and beamwidth: Higher gain generally produces a narrower beam and requires more accurate alignment.
- Polarization: Match linear or circular polarization to the radio system and propagation environment.
- Power, interface, and environment: Check power handling, connector or waveguide flange, mounting, temperature, weather protection, and size.
Conclusion
Microwave antennas convert guided RF signals into controlled electromagnetic radiation and perform the reverse process in reception. Selecting the right design requires balancing frequency range, gain, beamwidth, polarization, bandwidth, power handling, interface, and environmental requirements.
RF MISO supplies horn, reflector, array, microstrip, spiral, log-periodic, and other microwave antenna solutions for radar, satellite communication, testing, and wireless systems.
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Post time: Aug-15-2025
