Combination antennas to the rescue

Antenna manufacturers are finding new ways to accommodate the need for simultaneous voice, data, GPS and more.

The critical communications industry is evolving, and the era of traditional two-way voice being the only means of communication between a control room and a user in the field is over. Vehicles are being fitted with more technology, from onboard computers to equipment to fight crime and manage medical and fire situations.

These solutions are powered by the 4G LTE revolution, which is providing a high-speed wireless data stream from the network carriers alongside more secure, wireless local area networks.

However, such advances require innovation in many types of hardware, including antennas. This article explores the importance of using a combination mobile antenna to achieve best performance and utilisation on a public safety vehicle.

Changing environment

For many years, supplying the critical communications industry with mobile antennas was relatively straightforward. The customer selected a mobile radio, had a specific frequency designated for its use and simply sourced all the appropriate accessories, including mobile antennas tuned to suit.

This all changed with the need to transmit large packets of data wirelessly via cellular networks. The number of antennas required on a vehicle drastically increased to keep up with the data throughput, and this brought with it a number of challenges. Combination antennas have become more important and widespread as a way to tackle this growing challenge.

Modern vehicles have much smaller roof spaces, as well as styling that is dominated by a central light bar. A good example of this came with the discontinuation of the Crown Victoria vehicle by Ford in the USA in 2011, after which many police forces switched to the Dodge Challenger as their preferred new patrol vehicle.

With the addition of a few antennas for conventional radio, space becomes increasingly restricted, making it difficult to install auxiliary antenna equipment — especially for those that have a large ground plane and need to be as elevated as possible.

Furthermore, there is a push for police vehicles to appear more stealthy and less like standard law enforcement vehicles. So fitting standard antenna products is not always an option.

More recently, the challenge has become even harder with vehicles such as the Ford Explorer, with its ribbed roof line, becoming increasingly popular. This has meant that only certain shapes will fit on the roof, bringing with it additional complications for antenna product design, especially if larger-footprint combination antennas are desired.

Combining antennas

Some of the ways to get around the issue of restricted space include combining different-frequency antennas together in a single housing or developing a multiband antenna. These techniques have become more sophisticated and customers now expect that auxiliary antennas will very closely resemble the OEM car antenna.

This brings its own difficulties, as the antenna has to look aesthetically pleasing while maintaining a small and correct shape. With vehicles potentially fitted with cellular and Wi-Fi capable devices, as well as conventional radio, this expectation becomes a bit of a dilemma.

Furthermore, there is the potential to run into interference issues if the antennas are placed too close to one another. 700 MHz, a commonly used band in certain areas of the world, adds further complexity, as a standard ¼ wave at this frequency is approximately 10 cm in length. Disguising such an antenna is challenging.

In addition, as these antennas are used for mission-critical deployment, they must be good quality and correctly tuned before they are installed to ensure a reliable and high-performance connection is maintained at all times.

Enter MIMO

With the need to boost data rates so that users can send large files, multiple-input, multiple-output (MIMO) antennas have become increasingly necessary. This brings its own complexities as MIMO requires multiple, same-frequency antennas to operate simultaneously in the designated frequency band.

Given that MIMO antennas need to be spaced appropriately to avoid interference, and there is restricted roof space and tight budgets, antenna manufacturers are under pressure to come up with innovative designs while also meeting customers’ performance expectations.

This is even more challenging as LTE 700/800 MHz networks are rolled out, with potentially patchy coverage.

Public safety authorities worldwide are also looking at all possible ways to reduce costs and remain within shrinking budgets, while meeting expectations to have the latest technology. This has placed added pressure on component manufacturers to come up with cheaper, more cost-effective, more efficient and better designs.

Combining antennas into a single housing is one way of getting around this issue, as they reduce the cost and time for installation and can potentially help retain the resale value of the vehicle.

They also can futureproof the vehicle. For example, a combination antenna may have GPS, cellular or Wi-Fi capability even if the user currently does not need such functionality. However, given its ubiquity it is likely that such a user will adopt GPS, cellular and/or Wi-Fi within the next few years, in which case they will not need to add any further external equipment as it will be already installed.

Cutaway diagram of a Sharkee antenna.

It’s for these reasons that Panorama has invested heavily in the development of the MIMO Sharkee vehicle antenna unit. This shark fin-style, semi-covert unit accommodates up to six antennas in a single product, designed to fit within a vehicle’s ribbed roof line. With two wideband 700–3800 MHz antennas offering the MIMO performance desired by the public safety industry, it covers all the standard cellular frequencies. Two dual-band 2.4 and 5.8 GHz Wi-Fi antennas offer MIMO capability for high-speed data transmission in and around the vehicle, and an active 26 dB GPS module means the vehicle’s location is known at all times when data is being transmitted. A whip placement enables the customer to adopt their VHF, UHF, dual-band or even tri-band antenna.

Antennas such as this address the transition between traditional conventional radio and advanced wireless technology, while meeting the key challenges and demands of the public safety industry in the 21st century.

Images courtesy Panorama Antennas and dealers

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