GSM, 3G, 4G LTE, 5G SUB-6 ANTENNA DESIGN

What makes cellular antenna design different?

One of the largest drivers of antenna technology and design over the past decades has been cellular networks and portable devices. 2G, 3G ,4G LTE and now 5G have all build upon its predecessor with added layer of complexity. At the same time development that started with phones lead to smartphones, IoT sensors, wearables, and many more applications.

Multiband antennas

Cellular systems are operated by cellular operators that license frequency bands from public officials. This is big contrast to many other systems that use ISM bands. This also means that there are a lot of different frequency bands in use for cellular systems and they vary across the world.

When you have several frequency bands to cover you need 2, 3, 4 or multiband antennas that are generally more complex and sensitive for errors. They also need more space compared to single band antennas.

In speaking language cellular frequency bands are grouped together. Different variations exist but we prefer to use two different ways depending on the band configuration:

1. Split in two:

  • Low Band (LB), 699-960 MHz
  • High Band (HB), 1710-2690 MHz

2. Split in three:

  • Low Band (LB), 699-960 MHz
  • Mid Band (MB), 1710-2170 MHz
  • High Band (HB), 2500-2690 MHz

Antenna performance requirements

Network operators associate they brand with the quality of connection to their network. They quality of connection depends on the performance of user equipment (UE) connecting to the network. For example, a smartphone (UE) with a bad antenna will behave poorly in the network which is seen as limited coverage by the user and in many occasions the network operator will be blamed. This is the reason why some network operators have their own performance requirements for devices in their network. These requirements can be really challenging to meet.

Typically, requirements are set for

  • Total Radiated Power (TRP)
  • Total Radiated Sensitivity (TRS/TIS)
Commonly used cellular bands Frequency [MHz] Uplink [MHz] Downlink [MHz]
1 2100 1920-1980 2110-2170
2 1900 1850-1910 1930-1990
3 1800 1710-1785 1805-1880
4 1700 1710-1755 2110-2155
5 850 824-849 869-894
7 2600 2500-2570 2620-2690
8 900 880-915 925-960
12 700 699-716 729-746
17 700 704-716 734-746
18 850 815-830 860-875
20 800 832-862 791-821
28 700 703-748 758-803
custom antenna design

Regulatory requirements

In addition to network operators placing their requirements for your device government regulators place limits to the performance. These are due to public safety and interoperability reasons. Limits themselves are not specific to only cellular systems but the combination of high-performance requirements and challenging antenna design lead to situation where extra attention needs to be kept not to reach safety limits.

In terms of antenna design there are two criteria that are important:

  1. Specific Absorption Rate (SAR)
  2. Effective Isotropic Radiated Power (EIRP)

Limitations these two create are tackled by shielding user body from the antenna and making the radiation as omnidirectional as possible. The criteria limits vary between countries and device types.

custom antenna design

Multiple antennas per band

Latest LTE and 5G standards include diversity and multiple-input-multiple-output (MIMO) antennas. Purpose of those is to improve reliability of connections by increase reception sensitivity and enable higher data rates.

Diversity antenna is a second reception (Rx) only antenna with different radiation characteristics than main antenna which has transmission (Tx) capabilities as well. Both Main and Diversity antennas should be about equal in performance to get most benefit out of the diversity
functionality which is about 3dB.

MIMO can have 2, 4, 8 or even more MIMO antennas in reception (Rx-MIMO). Usually there is only one transmission antenna but in certain application multiple Tx-MIMO antennas are used. For a MIMO antenna to be useful they need to differ from each other which means the location, antenna itself or both need to be different from one antenna to another.

custom antenna design

Radientum Services for Cellular antenna design

We offer antenna design services for full product development projects from feasibility studies through different design stages to consultancy at mass production phase.

Our antenna simulations are critical at reaching accurate performance forecast in early stages of development enabling informed decisions before manufacturing of prototypes. Simulation enable us to use our extensive know how in product integration to find new innovative antenna solutions.

We can also measure both TRP and TRS of a cellular system in our own anechoic chamber against communication tester. This means that a Test-SIM card is only thing needed to get measurement started and the communication tester will control your device.

We specialize in high performance integrated solutions that are cost-driven. Check our references!

References

RADIENTUM

Visiokatu 4
33720 Tampere, Finland
+358 40 501 3535
contact@radientum.fi

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