In practical satellite communication applications, the polarization alignment between the antenna and the satellite directly affects signal reception quality. Whether in fixed ground stations, SOTM (satcom-on-the-move), or maritime/airborne platforms, precise polarization angle adjustment is a critical step to ensure a stable and reliable communication link.
So why is polarization alignment so important? How should linear polarization be adjusted in a scientific and systematic way? And why does circular polarization simplify installation and commissioning?
In our previous articles — Definition, Calculation, and the Relationship Between Antenna Polarization Angle and Terminal Position/Attitude and Impact of Polarization Angle Errors on Antenna Gain and Cross-Polarization Isolation — we introduced the definition of the polarization angle, the concept of cross-polarization isolation, and how the terminal’s geographic location and orientation affect antenna polarization.
Today, from an engineering-practice perspective, we will provide a systematic explanation of how to adjust the polarization angle for satellite communication antennas under both linear and circular polarization scenarios, along with the principles behind these methods.
Dual-Polarization Frequency Reuse
The radio frequency spectrum available for satellite communications—such as the C, Ku, and Ka bands—is a globally shared and extremely limited natural resource. The bandwidth of each band is fixed and strictly allocated and regulated by the International Telecommunication Union (ITU). As communication services continue to grow explosively, the demand for satellite bandwidth has increased dramatically.
To maximize the utilization of these valuable spectrum resources, modern satellite communication systems widely adopt dual-polarization frequency reuse. In this approach, the satellite simultaneously transmits two independent signals over the same frequency by using different polarization states:
One signal uses vertical polarizationwhile the other uses horizontal polarization, or
One uses left-hand circular polarization (LHCP)while the other uses right-hand circular polarization (RHCP).
Example:
In the traditional approach, if a frequency could support only one polarized signal, transmitting two different signals would require two separate frequencies (e.g., F1 and F2). With polarization reuse, however, both signals can be transmitted over the same frequency (e.g., F1): one using horizontal polarization and the other using vertical polarization (or LHCP/RHCP in circular-polarization systems).
In this way, a frequency that originally carried only a single signal can now carry two independent channels simultaneously. This effectively doubles the overall communication capacity without the need for additional spectrum allocation—a significant efficiency gain given the high cost and scarcity of satellite transponder resources.
Polarization Angle Adjustment for Satellite Communication Antennas Under Linear Polarization
If the satellite transmits a horizontal polarization (H-Pol) signal, how should the ground antenna adjust its polarization angle to achieve proper alignment?
Why is such horizontal/vertical polarization adjustment necessary?
As explained in our earlier articles, satellite polarization—especially for geostationary (GEO) satellites located above the equator—is defined with respect to the Earth’s equatorial plane. Horizontal polarization (H-Pol) refers to an electric field vector that is parallel to the equatorial plane. The polarization angle, therefore, describes the tilt of the satellite’s H-Pol electric field vector relative to the local horizontal plane at the ground station when the signal arrives.
This means that achieving polarization alignment on the ground does not simply mean placing the feed, LNB, or OMT in a way that matches the local “horizontal” direction.
For example, consider a GEO satellite located at 125°E, transmitting an H-Pol signal (with its electric field parallel to the Earth’s equatorial plane). If a ground station is located exactly on the equator and directly beneath the satellite’s longitude (also at 125°E), then the satellite’s horizontal polarization will indeed be parallel to the local horizontal plane of the ground station.
However, at any other geographic location, the satellite’s electric field will appear rotated from the perspective of the ground station. In these cases, the received horizontal polarization is no longer aligned with the local horizontal plane; instead, it arrives with a certain rotation angle relative to the ground station’s reference frame. Therefore, the ground antenna must rotate its feed or OMT accordingly to match the incoming polarization direction and achieve proper alignment.
How to Adjust Horizontal/Vertical Polarization Angles
Adjustment Method for Linear-Polarization Signals: Ground Fixed Stations and SOTM Terminals
For linear-polarized signals, technicians typically adjust the polarization angle after completing azimuth and elevation alignment. Once the antenna is accurately pointed, the polarization adjustment can begin.
First, based on the satellite’s orbital position and the geographic coordinates of the ground antenna, the azimuth, elevation, and polarization angle are calculated. After obtaining the required polarization angle, the technician rotates the antenna feed—most commonly by rotating the LNB or the feed assembly—to ensure that the antenna’s receive/transmit polarization is properly aligned with the satellite’s incoming signal.
This rotation aligns the ground antenna’s horizontal or vertical polarization with the satellite’s polarization orientation, minimizing cross-polarization interference and maximizing link performance.
If the LNB bracket includes a polarization scale, the technician can simply rotate the LNB to the calculated theoretical polarization angle indicated on the scale.
In addition, many modern fixed ground stations and SOTM antennas use automatic satellite acquisition. The antenna control unit (ACU) drives a motor to automatically rotate the feed (LNB) to the required theoretical polarization angle.
There is also a manual polarization adjustment method for rotating the antenna feed (LNB). For example:
Suppose a satellite transmits a horizontal-polarization signal at 12250.2 MHz and a vertical-polarization signal at 12250 MHz, and the ground antenna needs to align to the horizontal-polarization signal.
Horizontal and vertical polarizations are orthogonal to each other in space.
A well-designed antenna optimized for horizontal polarization has extremely low sensitivity to the vertical-polarized wave. When the antenna is perfectly aligned to horizontal polarization, its response to the vertical-polarized signal is theoretically zero.
Therefore, the goal of polarization adjustment is to:
Maximize the received power of the desired signal (12250.2 MHz, horizontal polarization).
Minimize the power of the undesired orthogonal signal (12250 MHz, vertical polarization)—ideally making it disappear on the spectrum analyzer.
When these conditions are met, the antenna is perfectly aligned with the horizontal-polarization signal while achieving maximum suppression of the orthogonal vertical-polarization signal.
Manual Polarization Adjustment Procedure for Ground Station Antennas：
Preparation and Calculation: Input the local location and satellite longitude, and calculate the theoretical polarization angle.
Equipment Connection and Setup: Properly connect the spectrum analyzer to the LNB output, and configure it to clearly observe the target signal as well as potential interference signals.
Azimuth and Elevation Adjustment: Adjust the antenna’s azimuth and elevation angles so that the antenna points toward the satellite.
Polarization Angle Adjustment: Rotate the antenna feed (LNB) to the theoretical polarization angle to initially acquire the signal.
Fine-Tuning Optimization (Core Loop): This is a precise and iterative process. By slightly rotating the LNB and monitoring the spectrum analyzer in real time, maximize the target signal power while minimizing the interference signal power to find the optimal peak point.
During manual polarization adjustment, continuously monitor the power of the horizontally polarized signal (desired signal) and the orthogonal vertically polarized signal (interference), and calculate the cross-polarization discrimination (XPD).
Polarization adjustment for satellite communication antennas when operating with circularly polarized signals
Advantages of Using Circular Polarization in Satellite Communication Antennas：
Mitigates polarization mismatch, making it particularly suitable for mobile satellite communications.
When satellite communication antennas use linear polarization (horizontal/vertical), the antenna’s polarization must be precisely aligned with the signal. If the receiving antenna is misaligned, or if the mobile antenna rotates during movement (e.g., a vehicle turning, a ship rocking, or an aircraft rolling), severe polarization mismatch may occur, resulting in significant signal attenuation or even communication interruption.
In contrast, circularly polarized waves have a rotating electric field vector during propagation. A right-hand circularly polarized (RHCP) antenna can receive RHCP waves from any orientation (as long as the sense of rotation matches) without signal loss due to the antenna’s own rotation. In other words, theoretically, the antenna’s ability to receive RHCP signals remains unchanged regardless of rotation about its boresight axis.
For example, many mobile Ka-band signals for aviation and maritime applications use circular polarization to mitigate the effects of platform attitude changes. The Ka-band signals transmitted by satellites such as ChinaSat-26 and high-throughput satellites also employ circular polarization.
Mitigates Faraday rotation caused by the ionosphere
When a linearly polarized signal passes through the Earth’s ionosphere, the Earth’s magnetic field causes the polarization plane to twist or rotate. The degree of this rotation is inversely proportional to the square of the signal frequency (the lower the frequency, the greater the rotation). This phenomenon is known as Faraday rotation.
Faraday rotation affects only linearly polarized signals and does not alter the handedness of circularly polarized signals. A right-hand circularly polarized (RHCP) signal remains RHCP after passing through the ionosphere, although its phase may change. Since the effect of Faraday rotation is inversely proportional to frequency, it is more pronounced for low-frequency signals. For example, in low-frequency bands such as the L-band used by GPS and BeiDou navigation satellites, the S-band used by TianTong satellites, and the L/S-bands used by satellite phones, Faraday rotation can reach tens or even hundreds of degrees. Therefore, circular polarization is commonly employed for these satellite signals rather than linear polarization.
Greatly simplifies antenna installation
As mentioned earlier, linearly polarized antennas require precise adjustment of the polarization angle during installation, and mobile satellite antennas must continuously adjust the polarization angle in real time. In contrast, circularly polarized antennas require no polarization adjustment during installation. In practice, it is only necessary to ensure that the antenna’s sense of rotation (left-hand or right-hand) matches that of the satellite signal, greatly simplifying the installation and satellite acquisition process.
For mobile satellite antennas, only the azimuth and elevation angles need to be adjusted to point toward the satellite, without the need to calculate or adjust the polarization angle. This significantly lowers the technical requirements.
How is the antenna polarization angle adjusted for circularly polarized signals?
In fact, circularly polarized antennas do not require polarization angle adjustment; only the polarization state needs to be selected. Taking a Ka-band circularly polarized satellite communication portable station as an example:
The antenna of the portable station has only two polarization states: 0° and 180°. The feed (OMT or waveguide switch) is designed to switch between RHCP (right-hand circular polarization) and LHCP (left-hand circular polarization) operation modes. This is a simple two-option configuration rather than a finely adjustable angle.
During satellite acquisition, the user simply switches the feed between 0° and 180° manually; the antenna’s polarization does not require motorized servo adjustment. It is important to note that if the circular polarization sense is incorrect (for example, using an LHCP antenna to receive an RHCP signal), signal loss can reach 25–30 dB, causing the communication link to fail completely. During commissioning, only one of the two states (0° or 180°) can establish a valid connection, while the other will result in almost no signal.
Why is the Antesky Flyaway Antenna Easier to Align Polarization in Engineering Applications?Antesky 1.0-2.4 Meter Flyaway antenna is engineered with practical field deployment requirements in mind, making polarization alignment significantly more efficient:
• Precise Feed Polarization Scale
Antesky 1.0-2.4 Meter Flyaway antenna: The linear-polarized feed is equipped with a ±90° mechanical scale, perfectly matching the engineering workflow described in this article—allowing technicians to “coarsely set the polarization angle according to the theoretical value.”
• Optional Motorized Polarization Adjustment (for Fixed or Transportable Stations)
For users who need quicker setup, remote operation, or reliable repeatability (such as government, broadcast, emergency communications, or fixed ground stations), Antesky antenna can be configured with:
A polarization adjustment motor
Controller-based automatic positioning to the specified polarization angle
• 0°/180° Quick-Switch Circular Polarization Feed
For circular-polarized configurations, the antenna uses a feed design that supports instant switching between RHCP and LHCP.
• High Cross-Polarization Isolation
The feed system is optimized to provide excellent cross-polarization isolation, ensuring strong co-pol performance while suppressing unwanted cross-pol signals—matching the XPD requirements outlined earlier in the article.
Conclusion
This article systematically elaborates on the theoretical foundations and practical methods for adjusting the polarization angle of satellite communication antennas. By analyzing the characteristics of linear and circular polarization in different application scenarios, we recognize the critical impact of polarization alignment on communication quality. Linear polarization systems require precise polarization angle adjustment to ensure maximum signal reception and interference suppression, whereas circular polarization systems simplify the installation process through rotational direction matching.