History and Future of Antenna Systems

The world is increasingly connected. The current boom in mobile communications is creating a new concept for social interaction. There is practically nobody that does not have a mobile device, enabling the communication at long distance. How have we reached this? Here we
will try to explain briefly the history of mobile communications from its beginning, with large and uncomfortable cell phones, to current small smartphones, the evolution of networks and their worldwide expansion.

There is no doubt that today the mobile device is part of our daily life. Far are the first analogue mobile telephony networks, taking advantage of the experience gained with the radio broadcast since Marconi achieved it in 1899, connecting Dover with Wimereux.

The first radio communications, using half duplex systems, were very important for navigation. Thanks to these systems, the boats could contact others and ask for help if there were in difficulties. It was possible to establish long-distance conversations, too, and the world began
the era of globalization. Such was the impact of radio in our world that technologists dedicated years to its study, trying to improve the service it provided. First with half duplex systems, up reach the current full duplex system that allows conversations without communication codes. Let’s see how that evolution has been.

First cellular devices

The first signs of mobile telephony date back to the 1940s. AT & T created a first mobile phone service in some US cities, using transmitters in cell mode. The name “cellular” comes from here, to refer to the devices that allowed a wireless communication. It consisted of a network of low-power transceivers to which the telephones were connected wirelessly, instead of using a single transmitter with a higher power level. By reducing the electromagnetic field with the square of the distance, the connection between the cell device and the transceiver required not only that the transceiver radiated with a proper power level, but that the cell device also did so. Being the location of the transceivers fixed, there would be no problem in increasing the power level to get the connection with the cell phone. But conversely, if the cell phone had to radiate with a high power level, it was in contradiction with its mobility, since it would be a bulky device.
In 1974, the first commercial networks themselves began to appear, from the hands of the NTT in Japan, and from that moment an explosion of commercial cellular telephone networks began, although these networks were not available to everyone.

These first networks were, to a large extent, analog, and the cell devices were large and weighed about 1 kg. Martin Cooper is considered the pioneer of this technology, leading an R&D team at Motorola, dedicated exclusively to cellular technology. However, the saturation of the networks, due to the increase in the number of users, forced the development of new systems that would allow multiple access and control telephone traffic. And this is where the digital signal processing is incorporated into the technology, and the first digital cells begin to emerge.

The digital signal is the key in the evolution of networks

Since Nyquist conjectured the sampling theorem, there has been a long way to reach digital systems. The first digital systems were for military applications. Technology was expensive and only those agencies and agencies with sufficient budget to approach it could access it.

Therefore, commercial mobile communications in digital format are not reached until the end of the 20th century, coexisting with analog communications. It is known as GSM standard. Developed in 1982, it began to be implemented globally in the 90s and is a revolution in the world of telephony: in addition to voice and short messages, the system could have access to data, being able to connect to Internet. However, the first GSM cell phones still did not incorporate touch screens, but worked with menus. Those were the days of NOKIA’s dominance over the cell phone sector.

The revolution that supposed the GSM caused the definitive shutdown of the analogical networks. Although the GSM network originally started to work in the 900 MHz band, the 1800 MHz band soon was begun to use and the first dual-band cell phones began to be commercialized. These phones allowed better access to telephone traffic. And then, the Telecommunications companies began an aggressive commercial campaign to increase the number of users to their communications networks: the offer of practically free terminals began to create a bag of users so large that mobile phone manufacturers started working on the technology 2G, which included the first GSM standard, the PCS / IS-136 (or TDMA) and the IS-95 / cdmaONE (or CDMA). The GPRS (General Packet Radio Service) is incorporated, too. These second generation mobiles responded to the great demand that was being generated in mobile communications. Cell phones were beginning to be multiband.

But soon, standards evolve to the third generation, known as 3G. This new generation of devices is beginning to be smart. The new generation incorporates the UMTS standard, and the terminals begin to become small computers. The terminals no longer only allow voice and messaging communication via SMS, but also develop an application field with the incorporation of the first touch screens. Now we can connect to the Internet through browsers, there is access to instant messaging through Messenger, Skype or WhatsApp, we can connect to WiFi networks and interconnect between devices through Bluetooth. A large number of functionalities that make explode the world of mobile communications, thanks to the development of specific applications.

To see the importance in the increase of the users that have been providing by the different standards, the graph shows the evolution between the years 2003 and 2007. As we can see, the evolution has been fast and very important in user volume.

The 4G and the future 5G

The 3G standard is the one that has lasted the longest, from 2001 to the present, coexisting with the 4G standard that began to offer coverage in 2009. Increasing data rate is the reason of this standard, which already incorporates LTE, and it is based on the IP protocol. Therefore, it is a system and a network at the same time, and with it, the cable and wireless networks will converge.
The launch of 4G has led to the need for countries to revise their electromagnetic spectra in order to locate the operating bands. In this aspect, the advance in Digital Terrestrial Television has allowed to the occupation of the highest band in the UHF, which is now reserved for 4G
mobile communications.

Meanwhile, the evolution of the terminals has been on line with the evolution of the standards. The 4G terminals are already all smartphones and incorporate features such as NFC (Near-Field Communication, used
in proximity card chips) and even wireless charging systems. In this way, the terminal evolves not only to a small computer that allows any type of
communication, but it becomes a bank card or any other type, thanks to the NFC. And wireless charging systems allow charging the device without cables.
At present, the network for the 5th generation system, known as 5G, is already being developed, which forces us to revise the electromagnetic spectra for its location. There are not standards yet, but it is expected to be operating in 2020.

With this technology, the 4G 100 Mbps data rate is exceeded, achieving up to 400 Mbps, the same data rate that is achieved in fiber optic networks.

Technological advances caused by the evolution of mobile communications.

The advances on the mobile communications also led to technological advances in semiconductor devices and antennas. Semiconductor manufacturers have improved their components, achieving better power consumptions and component sizes, miniaturizing complex functions. Special mention should be done the development of the antennas, with hundreds of publications focusing on the development and miniaturization of multiband antennas, to be incorporated into mobile terminals and not occupying excessive sizes.
For obvious reasons, antennas are an essential part of mobile devices, since they are the elements that allow an effective wireless connection. Without these components, mobile communication would be very inefficient and the current evolution would not have been achieved.

The first antennas on the first generation mobiles were resonant antennas, usually monopole, that were embedded outside the terminal. Sometimes, you had to extend them to get better coverage.

As mobile devices were reducing the size, it was necessary to create another type of antenna. The improvement of the flexible printed circuits (FPC) technology allowed to make antennas embedded inside the terminals. It also allowed the design of multiband antennas, instead of resonant narrowband antennas, although with worse efficiency. These antennas are still of rigid design, and in many occasions, of custom design, since the terminals can vary from one manufacturer to another in their interior composition. Therefore, there will continue to be a clear need to continue designing antennas for these applications.

What about the future?

It is difficult to know what is going to come in the future. The latest  developments in communication standards have been so dizzying that the future is not as clear as water. However, there are elements that can show what the trend will be in the years to come: new materials, starting with graphene. New materials, such as molybdenum disulfide, or InGaZnO or pentacene are being used to make semiconductors. It is more than possible that graphene can be used as a conductor in the development of antennas, electrical contacts and energy collectors. Considering the immense leap that technology has given since the first massive cellular networks until today, the future is open. What is very clear is that mobile communications have opened a field that is in continuous expansion.

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