A “Gain” in Microwave Capacity

Junaid_Syed Junaid Syed April 3, 2014

Sentinel antennaMy colleague recently posted a good blog article previewing some of the course content from the CommScope Infrastructure Academy class titled “Microwave Radio Antenna Link Fundamentals.” Jim Syme presented the concepts of antenna directivity and gain in microwave systems, explaining how these characteristics compensate for the inherent losses within a microwave link. I’d like to expand these topics a bit to talk about how they influence microwave antenna size.

In general, antenna directivity and gain refer to the values associated with the boresight of an antenna. The boresight is the axis of symmetry of the antenna, which defines its maximum performance values. Gain is a measured value but directivity is computed. As such, gain is always less than directivity, reflecting the real-world measurement instead of atheoretical value.

The challenge in antenna design is tomaintain the gain of the antenna in the boresight direction but reduce its directivity/gain in other directions. The ability to do this is called side lobe discrimination. Side lobe discrimination can be improved by tapering the energy distribution on the radiating aperture so that edges of the aperture are illuminated less. This results in a reduction in effective aperture size, hence reducing the gain of the antenna. This technological challenge can be overcome by utilizing Class 4 ETSI (European Telecommunications Standards Institute) microwave antennas, whose side lobes are reduced without compromising the gain. CommScope’s line of Class 4 antennas is called Sentinel.

How does the move to Class 4 antennas impact the antenna size? The size of the antenna is decided based on the required receive signal level (RSL). In dense environments where high capacity is in demand to satisfy user needs, the carrier to interference (C/I) ratio (the amount of power in an RF carrier to the power of the interference that exists within the channel) is another parameter that dictates the size of the antenna. In some cases, larger sized antennas are used not because of RSL but to improve C/I. The larger antennas solve the problem in this regard but also increase CapEx and OpEx costs. Using low side lobe Class 4 antennas allows operators to use relatively smaller size antennas even in dense and high capacity demand areas. There is a huge potential for low side lobe antennas to mitigate today’s and tomorrow’s microwave link challenges.

In summary, Class 4 antennas with better side lobe discrimination offer opportunities to use physically smaller antenna in dense environments where interference is a concern, increasing the available link capacity and potential revenue generation. Another colleague of mine will be announcing a white paper soon that goes into even more detail. In the meantime, leave a comment with any questions.

About the Author


Junaid Syed

Dr. Junaid Syed works for product line management of the Microwave Systems team at Commscope. Junaid covers Middle East, Asia, and Africa in the areas of microwave and millimeter wave antenna systems, flexi waveguides and waveguide components that support mobile backhaul systems. He brings 26 years of international experience in the telecommunication and defense industries. He holds 10 US patents, 9 international patents and many patent applications are pending. He has penned a number of published articles and is a current member of technical committees of various IEEE conferences. He also represents CommScope as a technical committee member with ETSI and FWCC. Junaid earned his B.S. from Punjab University with Silver Medal honors, and a bachelor of engineering degree in electronics/avionics from NED University of Engineering and Technology with Gold Medal honors, both in Pakistan. He earned his Ph.D. in microwave and millimeter wave from the University of London and conducted his post-doctoral research on reflect array antenna design at Queen's University Belfast, both in the United Kingdom.