Antenna Systems & Technology - Fall 2016 - 12

FEATURE ARTICLE The 5 Biggest Myths Around Base Station Antennas Dr. Mohammed Nadder Hamdy, Director, Wireless Network Engineering - CommScope Base station antennas are like closed boxes that we rarely get a chance to look inside. They can't be opened without getting damaged, and their size and weight makes them difficult to display inside offices. Despite significant technological advancements on the inside of the box, we still see only the same shaped box from the outside. This could be one of the reasons behind many misperceptions surrounding their function, which have turned into myths over time. Let's explore some of the most common myths related to these mysterious boxes, revealing a few of the industry's best-kept secrets. While there are many industry myths, the five more prevalent are: 1. Antenna parameters are invariable 2. A panel antenna has the same pattern as its radiating elements 3. Multiple input ports mean multiple arrays inside 4. Multibeam antennas have multiple arrays inside 5. Beam steering requires active antennas Myth 1: All Antenna Parameters are Invariable Most radio planners will look to select their antenna base stations by gain, beamwidth, supported bands, and input ports. When consulting a datasheet listing these variables for different antennas, many planners will only see these values in their headers and summaries. However, what is often missed is the wide operating bandwidth and electrical tilt, both of which are key factors in affecting performance. To showcase this, we will examine two different examples - horizontal beamwidth (HPBW), and a front-to-back ratio example. Horizontal Bandwidth The graph below examines three different half power horizontal beamwidth antennas, deployed at 65 degrees. Each colored line represents a different frequency at a specific e-tilt. As you can see, the HPBW varies quite widely across the variety of supported bands and tilts of each antenna. If HPBW falls below expectations, this can lead to coverage holes - while conversely, increasing can lead to interferences. This is why tighter Figure 1. Horizontal Beamwidth example deviations are ideal, as it provides the most consistency of service. Front to Back Ratio In examining the front-to-back ratios, with once again each colored line representing a different frequency, we can see there is still a level of variance in each of the three models. As we can see, there is an enormous variance between each different antenna, which is not accounted for in the datasheet. Figure 2. Front-to-back ratio example 12 Antenna Systems & Technology Fall 2016 www.AntennasOnline.com http://www.AntennasOnline.com

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