RFAntenna Mechanical vs Electrical Tilt: Understanding the Differences
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This page compares antenna mechanical tilt vs. electrical tilt, highlighting the differences between them. We’ll also touch upon an antenna down tilt angle calculator.
We will explore the following:
- Techniques to increase cell capacity
- Definitions of mechanical and electrical tilt
- Mechanical tilt basics and its drawbacks
- Electrical tilt basics and its benefits
- Difference between mechanical and electrical tilt
Techniques to Increase Cell Capacity
The increasing popularity of wireless cellular technologies and the widespread use of mobile phones have necessitated improvements in network capacity.
RF engineers have developed techniques like frequency reuse and spatial isolation.
Initially, frequency reuse was employed with omnidirectional antennas, which unfortunately led to inter-cell interference.
The advent of sector array antennas improved frequency re-use, resulting in better cell capacity. However, this approach introduces intra-cell interference.
Spatial isolation can be achieved by focusing the beam in a particular region. This increases cell capacity by serving mobile users in different regions using different selective beams. However, the spread of the antenna’s radiation pattern can negatively impact adjacent sectors within the same cell, as well as adjacent cells. This leads to a degradation in the quality of service.
To address these issues, RF engineers have explored the concept of antenna tilt.
Figure 1: Antenna Downtilt
The dictionary definition of “tilt” is “incline or bend from a vertical position.” Tilting upwards is referred to as “uptilt,” while tilting downwards is referred to as “downtilt.” Downtilt is depicted in Figure 1.
Downtilt is generally the most beneficial and will be the focus of our discussion. We will primarily focus on the horizontal beam and not the vertical beam as shown in the figure-1.
Mechanical tilt involves physically or manually downtilting the antenna. This method has certain drawbacks, as mentioned later.
Electrical tilt was developed to address these drawbacks. Electrical tilt does not involve any physical movement. Instead, it changes the phases of the radiation pattern of individual antennas used in a sector array antenna. Electrical tilt can also provide the gain to support beamforming, which extends coverage.
Antenna Mechanical Tilt and its Drawbacks
Figure 2: Mechanical Tilt
RF engineers have historically used mechanical tilt to adjust the position of RF antennas.
However, as shown in Figure 2, this method tilts the antenna in only one plane.
Furthermore, when the front part is tilted down to decrease the gain on the horizon, the back side tilts upward.
This results in a change in the front-to-back ratio and an increase in inter-sector interference.
Mechanical tilt can lead to “pattern blooming,” as illustrated in Figure 4. The outermost part of the pattern in the right-hand position of Figure 4 represents a mechanically tilted antenna with 0 degrees of downtilt. The changes in radiation patterns with respect to different degrees of mechanical tilt are also shown.
Antenna Electrical Tilt and its Benefits
Figure 3: Electrical Tilt
The concept of electrical tilt has provided greater control over shaping the radiation pattern of the antenna and boosting the pattern as desired. This has simplified operations for cellular operators.
Electrical downtilt changes the phase element of the antenna’s different radiating elements separately and simultaneously.
This allows RF engineers to change the gain of the pattern around the tower in a full 360 degrees.
Figure 3 depicts the coverage achieved using electrical tilt.
Major Difference Between Mechanical Tilt and Electrical Tilt
Figure 4: Mechanical Tilt vs Electrical Tilt
Figure 4 illustrates the difference between mechanical and electrical tilt with respect to the radiation pattern.
As shown, mechanical tilt results in pattern blooming, while electrical tilt suppresses this blooming. Electrical tilt achieves this result by tuning individual radiating elements of the antenna array. Mechanical tilt fails to achieve this as it tunes the entire antenna as a fixed single unit.
