This is your car, can you hear me?

The car’s classic rod antenna for radio reception is almost a thing of the past. But did you know that modern cars have a number of hidden antennas? Find out where they are.

20. 1. 2022 Škoda World Innovation & technology

Sounds good

“The classic rod antenna on the roof has been replaced by fins, which look better and can integrate three functions. They include an LTE antenna for connectivity, an antenna for controlling the independent heating if the car is equipped with it, and a so-called GNSS antenna. The latter receives signals from satellites for navigation, and its unfamiliar name indicates that it can handle other satellite systems used around the world in addition to GPS,” says Vlastimil Navrátil, coordinator of the reception and sound department at ŠKODA Technical Development.

The antenna system is used not only by the radio and navigation system, but also by the e-Call function

The antenna for radio reception has been moved to the rear window. It is a printed structure integrated into the glass, similar to the strips used to heat it. When you look at the car from behind, you’ll notice that vertical lines have been added. “But from a radio-frequency point of view, the whole structure in the glass acts as an antenna, even the heating part. Via soldering plates and a short cable, the signal from this passive antenna travels to an amplifier located in the metal of the fifth door, which amplifies it and sends it via a coaxial cable to the car’s audio system,” explains Navrátil’s colleague, antenna specialist Petr Svoboda.

The thick blue lines are where you can find the antennas on the rear window of the ŠKODA ENYAQ iV.

You may have noticed that some manufacturers integrate the antenna into the side window by the boot – that is especially common on estate cars. ŠKODA tries to stick to the rear window, mainly because of the larger area of the glass and therefore better reception. There are two antennas in the glass, one for FM reception and the other for DAB. One antenna would be shielded from some directions by the bodywork, so two are used, ideally as far apart as possible and positioned differently so that they don’t behave as one.

The “glass” antenna includes filter elements. The antennas are connected to the heating, and without the filters, turning on the rear window defrost would interfere with signal reception.

How is the antenna structure for the rear window created?

It’s pretty complicated, and simply stretching a few wires across the glass won’t cut it. It starts with a computer simulation using what is known as mesh data, a more or less dense network of points representing the car’s entire body. And it is the fifth door is one of the parts that is defined in greatest detail for the antennas - because the accuracy of the calculations depends on it. The calculations take place at an intense pace over a period of about six weeks: one line is left out here, two are added there and so on. Very often, of course, the structures are based on ones that are already established and have worked well on another model, and these are then optimised. The surrounding cables have a big influence on the reception quality, and of course the sheet metal of the fifth door is a conductor, so it affects the signal too. All it takes is a one-millimetre adjustment to the sheet metal that encases the rear window during development, and the whole antenna has to be redesigned. After the computer simulations, the best result is tested on the car and optimised physically. Again, a piece of the structure is scraped off or added in the form of copper wire to see if that improves reception. Then everything is measured and so on and on and on, until the optimum reception is reached. Everything has to be well balanced. It often happens that by improving one antenna, the performance of the other will get worse.

Visualisation of the “mesh” for the ŠKODA OCTAVIA

Normal and emergency communication with the world

Underneath the rear bumper cladding is a pair of LTE antennas. “The one on the right is dedicated to mobile data services and, together with the antenna in the roof fin, ensures the best possible data flow. One would not be enough – the antenna is either receiving or transmitting at a particular moment, because it cannot handle both at the same time. That’s why they’re doubled up, so that the car’s communication with its surroundings is as fast, smooth and high-quality as possible, even at higher data volumes. In addition, the rooftop LTE antenna also serves the needs of the emergency e-Call system. This is mandatory in many regions, so even cars with lower equipment levels have GNSS and LTE antennas in the roof fin so that the car knows its location and can send it to emergency responders in a special SMS,” Navrátil explains.

The LTE antenna below the rear bumper used for mobile online services (here shown on the ŠKODA KAROQ).

The left antenna in the rear bumper serves as support for the Phonebox equipment. This is a module in the dashboard that enables inductive wireless charging of mobile phones. However, it is rather obscured there, so an outdoor signal finds it hard to reach. This antenna therefore essentially brings the mobile signal closer to the phone in the cockpit.

Phone Box enables wireless mobile phone charging and connection to the car’s external antenna

All European ŠKODA models today use the set of antennas described here, and you won’t see a classic roof-mounted rod antenna on them anymore. With one exception. “That’s the FABIA. What is otherwise caught by the structure in the fifth door, i.e. the AM, FM and DAB signal, is dealt with by a roof bar on this compact car. The FABIA has it on the roof even if it is equipped with navigation. In this case, the antenna bar has a larger base that contains the GNSS module,” adds Svoboda.

The ŠKODA FABIA and its rod antenna

So our car recognises us

These days, the vast majority of drivers press a button on the remote control to unlock the car. Or not even that. The system for unlocking and locking the car has its own control unit, which is located under the dashboard, approximately above the clutch pedal or left footrest. When the key is pressed, it sends out a signal on a 434 MHz wavelength. This is a free unlicensed band that is commonly used by most manufacturers. The antenna in the control unit receives it, evaluates the validity of the request and unlocks the car. It locks the car again later in the same way.

Car keys with remote control; its antenna is located below the dashboard.