In modern days, wireless communication systems are everywhere. They are easy to use, install, buy and maintain. These factors means that wireless communication systems are dominating the communication world to such an extent that you can rarely see people using wired or guided communication systems anymore.

What is most exclusive about a wireless communication system? Wireless communication systems are systems that transfer information from one place to another without using any guided medium like RF cables, fiber optics or waveguides. The main reason for the massive growth of wireless networks is this key property; the medium doesn’t need to be guided.

Among those wireless communication systems, cellular networks are in the lead when it comes to using wireless networks. Most of the time, the final network of almost all the cellular architectures like 3G or LTE is a cellular network. A huge amount of the backbone is also made up of micro links. Therefore, most cellular communication nodes use wireless communication. Antennas of cellular or modern LTE systems are now an important part of that architecture.

From the first generation of mobile networks, 1G to 5G, the development of the cellular system was very rapid and advanced. According to the generation, all the protocol, physical devices and the level of performance are different.

Why do you need Cellular and LTE Antennas?

The antenna is one of the most important components in the communication system architecture. Nowadays, digital communication is much more dominant than analog communication because digital modulation schemes are more immune to noise. Nevertheless, the antenna has always remained the same because the performance of the antenna only depends on the performance you need, and it is a crucial part of the system. Therefore, you need make sure you choose the perfect antenna for your cellular device.

When you consider the antennas in the cellular systems such as 3G or LTE, there are main distinctions between antennas of a typical wireless system and antennas on a cellular system. They deploy a different design approach than the other antennas in a typical communication system. If you consider the transmission antenna for a television transmission or FM transmission, the broadcaster uses the maximum power possible and the maximum height possible for the antenna according to the regulatory laws as these things determine the strength of signal. However, in the cellular system, one transmitter antenna should satisfy two things:

• The transmission antenna should give coverage to the expected portion of the cell.

• The transmission antenna should not increase the transmission power such that it would interfere the neighbor cell.

Therefore, both transmitter and receiver antenna of a cellular network have unique design considerations and excelled performance.

Parameters, Features and Categories of Cellular and LTE Antennas

There are two different types of antennas that you can use from the user-end of a cellular network. Those are internal antennas and external antennas.

Internal antennas are the ones that you install inside of a mobile device. These types of antennas are Microstrip patch antennas or the Stripline antennas. In a mobile device, these types of antennas are protected by the surrounding casing, therefore, using internal antennas are preferred in applications such as mobile phones, portable routers or laptops.

When considering external antennas, they need to be mounted outside without any protective casing. These work for applications such as signal boosting for a router, the antenna may sometimes be 10-15 meters away from the device. These are the most common ways to use an external antenna:

• In applications like routers, modems or the integrated access devices (IAD), using an external antenna is preferred. That’s because, after fixing the antenna for a good cellular signal reception, the device can continuously perform well without changing the orientation.

• Sometimes, when the signal reception for a mobile device or a router is bad, an antenna can be used to boost the signal. In this situation, a directional antenna should be used for better reception. The best choices are a dipole antenna or a Yagi antenna depending on the situation.

The following is a brief summary of the main two kinds of cellular antenna:

How Antenna Parameters Behave for Cellular Antennas

Antenna parameters always depend on the application itself. As cellular or modern 4G networks have their unique requirements that are different to any other wireless communication network, the antenna parameters also have a unique design approach.

i.  Gain and Radiation Pattern

At the mobile-user end, the antenna radiation pattern always takes an omni-directional pattern in the horizontal plane and doughnut-shaped pattern in the vertical plane. This pattern can be simulated as shown in the figure below.

This is an EM simulation of a 2dBi, 4G hinged antenna using CST Microwave Studio. The left image shows the horizontal far field radiation pattern of the antenna and it is symmetrical. That means the antenna receives or transmits in the whole horizontal plane.

The image in the middle is the radiation pattern in the vertical plane. The pattern is not a circle. A typical cellular antenna does not radiate in the whole vertical plane. This particular antenna has a vertical-plane gain of 2.6 dBi. This is to reduce power wastage. When a cell tower and the user is in line-of-sight, this type of gain is efficient for keeping the link alive.

ii.  Polarization

On the other hand, when considering a mobile phone, the orientation of the mobile phone always differs according to the user. The phone can be in the user’s pocket, on the desk or anywhere. Therefore, the antenna orientation can also vary and that could be a problem if the antenna does not align with the polarization of the cell tower antenna.

For the perfect signal reception, the polarization of the transmitter antenna should align with the polarization of the receiver antenna. To address this problem, in modern cellular networks, cell tower antennas have cross-polarization. That means there are two antennas on the cell tower to accommodate vertical and horizontal polarization. Most of the time the service provider will only use a single antenna for this. They use cross-dipole excitation in the feedhorn of the reflector antenna to achieve both vertical and horizontal polarization simultaneously.

Cross-polarization can achieve two things:

• The mobile phone orientation does not need to align with the cell-tower antenna polarization because the cross polarization transmits radiation in vertical and horizontal planes.

• Multiple users can connect to the cell tower in different polarization and it is easy to achieve MIMO (Multi Input Multi Output) for the communication system.

How to Choose the Best Cellular or LTE Antenna

It’s obvious that we need to use the best antenna for the cellular or LTE application for it to be effective. Therefore, the question arises, “How to choose that best antenna for a Cellular device?” There may also be an antenna with the wireless equipment already and therefore, a requirement for optimizing the performance of that antenna.

To achieve the above two things, the following are some common factors to be considered when choosing the antenna or increasing the performance of the signal reception.

1)   Always Be Aware of the Direction of the Cell Tower

This is essential for a receiving antenna of wireless equipment in the cellular network, especially when using an external antenna such as a Yagi antenna. This also depends on the cellar coverage of the service provider. For example, in a rural area where the cellular coverage is continuous and high, the user does not need to care that much about this. However, when a user is in a remote area where the coverage is low, the received signal strength of the cell tower is weak. In addition, if the user is at the boundary of a cell, the interference from neighbor cells will be quite high.

If you consider the above figure, user A belongs to the cell 1. Therefore, the receiving antenna of user A should be directed towards the base tower in the cell 1. However, as user A is near the boundary of the cell, the interference of cell 2 can affect the performance of user A.

This is because the way a cellular network is deployed is such that an end-user automatically connects to the cell tower with the higher receiving signal strength. Moreover, the signal strength, especially at boundaries can vary. Therefore, it is better to avoid the interchange between different cells. The best way to achieve that is to mount a directional antenna towards the cell tower with the best signal reception.

2)   Be Sure to Use the Correct Type of Antenna

The uses of internal and external antennas can be different according to the application. When considering the external antennas, if the external antenna is an indoor antenna, it is probably a dipole antenna or a whip antenna with an omni-directional pattern in the horizontal plain and a small gain in the vertical plane.

Other common external antenna for indoor uses are the hinged antenna or the panel antennas. In a 4G/LTE router, the preferred choice is a hinged antenna. A hinged antenna is a dipole antenna with an inductive load at the end. It has a gain around 3-6 dBi. A hinged antenna is directly connected to the RF antenna connector of the router.

If there is any need for extension, the preferred choice is a whip antenna or a Yagi antenna. Yagi antennas have a higher gain with a value more than 15 dBi. A Yagi is preferred when the signal reception is very weak.

If the antenna is an internal antenna, the most popular type is the Planar Inverted-F Antenna (PIFA). Nowadays, people always have their mobile phones with them, and they are always exposed to EM radiation. Therefore, it is essential to consider this human factor when designing wireless devices. Specific Absorption Rate (SAR) is a measure that indicates how much of the transmitted RF energy is absorbed by the human tissues. This depends on the transmission. PIFA antennas have good SAR properties.

3)   Mounting Method

Most of the external antennas in the routers are hinged type antennas. Therefore, the mounting method is not a concern as the antenna directly connects to the RF connector of the router. External dipole type antennas like whipped antennas have magnetic mounting. The base of the antenna is a magnet and it can be attached to metals with magnetic properties. These are the type of antennas you use in vehicles.

When considering the directional antennas like a Yagi or a log periodic antenna, you need to choose an antenna mast to mount them on. Antenna masts are a rigid aluminum stick. The antenna is mounted on this mast. One important thing to consider when using an antenna mast is to use lightning protection, otherwise, this can damage mobile devices. Here, it is not required to ground the antenna, but using a surge protector is just fine.

The internal antennas are extremely easy to install. Most of the time, these are adhesive antennas which can be attached to the casing of the devices, like the ones in the laptop. In the mobile phone, the patch antenna has a direct connection to the transceiver at all times.

4)   What Role does Frequency Reuse Play?

In a modern cellular network like 4G/LTE or 5G, there is the concept called, “frequency reuse.” This means that, in the cellular network, there are neighboring cells for a single cell. In most of the cellular networks, the shape of one cell is hexagonal. Therefore, there are six neighbor cells to every one cell.

You can see that in the following picture.

The idea here is to use different frequency bands in those seven cells to avoid interference. If you consider the middle Iris Blue cell, the surrounding six cells can interfere with the signal reception of a user in that cell.

The following are the different frequency bands in cellular networks:

• 3G Frequency Bands

UMTS (Universal Mobile Telecommunication System) are the groups of frequency bands used by the 3G cellular networks.

There are 32 frequency bands in UMTS.

Uplink and downlink capacities are different in each band.

• 4G/LTE Frequency Bands

There are TDD (Time division Multiplexing) bands and FDD (Frequency Division Multiplexing) bands.

Uplink and downlink capacities are different in each band.

To avoid using 7 frequency bands, there is a concept called, “cell sectoring” which can reduce the number of frequency bands.

The frequency bands can differ depending on the country. When a service provider chooses a set of particular frequency bands for a particular network, the regulatory body of that country assigns small channels to the service provider. Then the service provider uses those channels in different cells of the cellular network.

When designing the antenna, the antenna should be able to operate in all those possible frequencies in that band. Moreover, the transceiver of the mobile device, especially on the phone, should be able to change between 4G, 3G or 2G depending on the signal strength of the received signal. Therefore, in a mobile phone, antennas for all 2G, 3G and 4G bands are installed inside of the mobile phone. However, when you consider a cellular antenna of a router, most of the time, it only supports 4G. That’s because the speed of 2G and 3G is not sufficient for a router. There is only one receiving antenna band for a router, and that is 4G. These days, 3G routers or dongles are outdated and not really in use anymore.

To find out about the different frequencies of the different service providers and the different bands, you can check this free tool; Cellmapper – https://www.cellmapper.net/

Future and Development of Cellar and LTE Antennas

5G cellular networks are in our near future. Most of the leading companies in telecommunication have successfully deployed 5G tests in small-scale and large-scale events. Therefore, it is interesting to know how the cellular networks and cellular antennas would adopt to 5G.

An important factor about the 5G is that it is short range. The cell side of a 5G network would be much smaller compared to a 3G or 4G network. Therefore, the user would frequently change between cells. However, as the attenuation losses are higher for 5G transmission, the transmission power does not decrease. Therefore, the effects of the 5G RF power to humans is a big concern in 5G. In mobile devices you’ll need antennas with satisfactory SAR values. In addition, 5G cellular network would use the frequency in the range of 25-39GHz meaning that the antenna size becomes much smaller and the MIMO array antenna would be used inside the mobile for 5G networks.

One thing is certain, developments in wireless communication systems will always increase. After 5G, there will be 6G and the cellular networks will be more advanced and complex in the future. But an antenna will always be a part of those cellular networks.

With regarding the cellular antennas, we provides both quality internal and external antennas as mentioned above. Each antenna comes with the calibrated standards and you can check the specification of each antenna separately on the product page.