RHCP
Understanding RHCP
Circular polarization, and RHCP specifically, is essential for satellite communications because it eliminates the need for precise alignment between transmit and receive antenna orientations. A linearly polarized antenna must be aligned with the signal polarization; CP antennas work regardless of rotation.
RHCP Properties
- Sense: Clockwise rotation when viewed from behind the wave.
- Axial ratio: Ideal CP has 0 dB axial ratio. Good CP antennas achieve < 3 dB.
- Cross-pol: LHCP is the cross-polarization. Ideally zero coupling between RHCP and LHCP.
RHCP Applications
- GPS: All GPS signals are RHCP. GPS antennas must be RHCP.
- Satellite: Many satellite uplinks and downlinks use CP.
- Radar: CP reduces clutter from rain (rain reflections reverse polarization).
Frequently Asked Questions
What is RHCP?
RHCP is circular polarization where the electric field rotates clockwise when viewed from behind the wave. It is used for GPS, satellite communications, and radar. An RHCP signal requires an RHCP antenna for proper reception.
What is the difference between RHCP and LHCP?
RHCP rotates clockwise; LHCP rotates counter-clockwise. They are orthogonal: an RHCP antenna cannot receive LHCP signals and vice versa. This orthogonality enables frequency reuse by carrying independent signals on RHCP and LHCP simultaneously.
What happens when CP meets a reflector?
When a circularly polarized wave reflects from a flat surface, the polarization sense reverses: RHCP becomes LHCP and vice versa. This is why circular polarization is used in weather radar; rain reflections reverse sense and can be filtered out.