June 5, 2025

Antennas are used to transmit or receive electromagnetic wave signals, such as mobile phone antennas with a frequency range of 800MHz to 2.6GHz. Satellites are devices that operate in orbit and can forward radio signals. For example, communication satellites can cover about 90% of the world and provide television and telephone services. Antenna Functionality At […]

Satellite communication antenna types include: parabolic antenna (usually 1.2 meters in diameter, suitable for C band), flat antenna (light and thin, suitable for Ku band), helical antenna (supports circular polarization), phased array antenna (can electronically control the beam direction) and portable antenna (easy to deploy, about 0.6 meters in diameter). Choose the appropriate type according

An ​​elevated feed antenna​​ positions the ​​radiator 0.25-0.5λ above ground​​ to ​​reduce surface wave losses by 60%​​, boosting gain ​​3-5dB​​ versus ground-mounted designs. This setup uses ​​folded dipoles or patch arrays​​ at ​​2-6GHz​​, achieving ​​<2:1 VSWR​​ through ​​impedance matching stubs​​. The elevation minimizes ​​multipath interference​​, improving ​​SINR by 15dB​​ in urban environments while maintaining ​​±45°

The key difference lies in ​​radiation control​​: a ​​single antenna​​ emits/receives signals with fixed ​​5-15dBi gain​​, while an ​​array combines multiple elements​​ (4-256+) for ​​steerable beams​​ achieving ​​20-40dBi gain​​. Arrays use ​​phase shifters​​ to electronically adjust patterns ​​within 10μs​​, enabling ​​±60° scanning​​ without mechanical movement. Single antennas cover ​​1-5GHz bandwidth​​, whereas arrays achieve ​​5-10x wider

A ​​triple feed antenna​​ integrates ​​three independent feed points​​ to enable ​​multi-band or multi-polarization operation​​ within a single aperture. This design achieves ​​>90% isolation between ports​​ while supporting ​​simultaneous LHCP/RHCP/linear signals​​. Typical configurations use ​​orthogonal waveguide slots​​ or ​​stacked patches​​, reducing size by 40% versus separate antennas. Key applications include ​​satellite comms (4-30GHz)​​ where it

An ​​axial or front feed antenna​​ positions the ​​feed point along the central axis​​ of parabolic dishes, achieving ​​>60% aperture efficiency​​ with minimal blockage. This design reduces ​​sidelobes by 15-20dB​​ compared to offset feeds while maintaining ​​<2dB noise temperature​​. The waveguide typically extends ​​0.3-0.5x focal length​​, optimized for ​​3-30GHz frequencies​​ with ​​cross-polarization under -30dB​​. ​​Basic

A ​​coaxial feed in antenna​​ refers to using ​​50-ohm or 75-ohm coaxial cable​​ to deliver RF signals directly to the radiator. This method achieves ​​>95% signal efficiency​​ with minimal loss (<0.5dB/m). The ​​inner conductor connects to the driven element​​ while the ​​outer shield grounds to the reflector​​, reducing interference by 30dB. Common in ​​dipole and

Common antenna feed lines include ​​coaxial cables​​ (50/75Ω impedance, <0.5dB/m loss at 1GHz), ​​waveguides​​ (low-loss for mmWave, e.g., WR-90 handles 8-12GHz), ​​microstrip lines​​ (PCB-integrated, 50Ω typical), and ​​twin-lead wires​​ (300Ω for FM antennas). Fiber optics (<0.2dB/km) feed phased arrays via photonic conversion. Baluns often match unbalanced feeds (e.g., coax) to dipole antennas. ​​Coaxial Cable Basics​​

TEM (Transverse ElectroMagnetic) waves cannot propagate in ​​single-conductor waveguides​​ (e.g., rectangular or circular) because they require ​​two separate conductors​​ (like coaxial cables) to support both electric (E) and magnetic (H) fields orthogonally. In hollow waveguides, the ​​boundary conditions​​ force at least one field component to be longitudinal, creating ​​TE/TM modes​​ instead. For TEM propagation, the

Waves in a waveguide are ​​confined electromagnetic modes​​ propagating along its structure, categorized as ​​TE (Transverse Electric), TM (Transverse Magnetic), or TEM (Transverse ElectroMagnetic)​​ modes. For example, in a ​​rectangular waveguide (e.g., WR-90 for X-band)​​, TE₁₀ mode dominates at ​​8.2-12.4 GHz​​ with a cutoff frequency of ​​6.56 GHz​​. Optical fibers guide ​​1.55 μm infrared waves​​