From Earth to Orbit: The Important Role of Antennas in NTN

As the Internet of Things (IoT) continues to expand, the challenge of connecting devices beyond terrestrial network coverage becomes increasingly important. Non-Terrestrial Networks (NTN) enable IoT applications to reach areas where traditional connectivity cannot, bridging the gap between terrestrial and satellite systems.

In this context, antennas play a central role in enabling the innovation behind Non-Terrestrial Networks (NTN). Their design dictates how effectively devices connect and sustain communication with satellites - particularly under the strict requirements of low power consumption, compact size, and cost sensitivity typical of IoT applications. This paper explores the significance of antennas in NTN, outlines their key specifications and types, and discusses future developments in this field.

NTN Use Cases

NTN is not about replacing terrestrial connectivity but complementing it. Where terrestrial networks are unavailable or unreliable - such as oceans, mountains, deserts, or remote rural regions - NTN ensures continuity.

This enables applications that were once restricted to expensive and proprietary satellite networks:

• Asset tracking and logistics across land, sea, and air
• Agriculture and environmental monitoring in remote fields or forests
• Smart metering for utilities in rural or hard-to-reach areas
• Emergency communications where terrestrial networks are down or overloaded

By lowering the barrier to entry, NTN opens new opportunities for large-scale deployments that combine terrestrial and satellite connectivity seamlessly.

Figure 1. NTN Use Cases

Why Antennas Are Critical in NTN

Satellite communication poses distinct challenges for antenna design. The downlink signals are typically very weak, while IoT devices must operate with minimal power consumption. When the antenna cannot efficiently capture enough of the incoming signal, the device may need to retransmit data multiple times - leading to unnecessary energy use and shorter battery life.

Key antenna parameters for satellite communication:

• Gain: sufficient to close the link budget without requiring higher transmit power.
• Polarization: matching satellite polarization improves reception; circular (RHCP/LHCP) signals lose ~3 dB if received with linear antennas.
• Bandwidth: must cover transmit and receive frequencies across L- and S-bands.

• Radiation pattern: gain at low elevation angles is essential, especially for LEO satellites not always overhead.

Figure 2. Illustration of elevation angle and propagation delay (source: 3GPP TR 38.811)

If we look into the link budget formula:

G_rx  = P_req - EIRP +   FSPL + L_other

          P_req = required received power (dBm) = receiver sensitivity (TIS) + desired margin (dB)

          EIRP = satellite EIRP (dBm)

          FSPL = free-space path loss (dB) = 20log10(4πR/λ)

          L_other = sum of other losses in dB

L_other includes different type of losses, many of them related only to satellite communication, which are not critical in terrestrial networks, for example, atmospheric/ionospheric and rain losses. 

Also, losses affecting polarization mismatch. Remember that the signal from satellites is circular polarized, Right Hand Circular Polarization (RHCP) or Left-Hand Circular Polarization (LHCP). If the receiving antenna is linear polarized, you will lose up to 3dB, as only one linear component of the signal will be received. Circular polarization is difficult to achieve when covering different frequencies over a broad bandwidth. Therefore, for the applications where there is hybrid connectivity (terrestrial + NTN), having a single antenna doesn’t allow to have circular polarization.

Another factor that is not always considered is the antenna gain towards the azimuth. Satellites, especially for LEO that are moving around the earth, are not always at the zenith. If the antenna has low gain on the azimuth, this will also affect the link budget. For example, patch antennas have high gain, but they are directive, and the gain towards the azimuth is much lower than the peak gain towards the zenith. In the case of GEO satellites, the location where the device also affects the response – if the GEO satellite transmits the beam from the north hemisphere but the device is located on the south hemisphere, the gain towards the azimuth plays an important role.

These are the technical factors why the antennas are critical for NTN, however there are also non-technical factors as size and cost. Traditional satellite antennas are large and expensive, which don’t make them suitable for IoT, where the mass deployment is in mind. In order to scale the number for IoT devices connected to satellite, the antennas must be affordable and have a reasonable size.

NTN Antenna Specifications

3GPP Release 17 provides an initial class of consumer and IoT devices to communicate over orbiting satellites. 

The frequencies used for NB-NTN are located in the L and S-bands. To be precise, and taking Skylo as example:

Table 1. Skylo frequency bands

Depending on the band and the satellite provider, the polarization can be RHCP or LHCP. Typically, most cases have been RHCP in the L-band while LHCP for the S-band, although it could also be RHCP.

As checked in the previous section, the antenna specifications to close the link budget will depend on several factors. Not all the satellite providers have publicly announced the requirements, but as reference, Skylo has published the specifications for the device certification.

Skylo has 2 types of devices for their certification (ref. Skylo Certification – Device v1.0):

Type 1 for high-performance IoT or automotive:

Type 2 for consumer-grade wearables or handsets:

These specifications relate to the device performance TRP (Transmitted Radiated Power) and TIS (Total Isotropic Sensitivity):

TRP (Total Radiated Power)

TRP_dBm = Conducted Power_dBm + Antenna Total Gain_dB

TIS (Total Isotropic Sensitivity)

TIS_dBm = Conducted Sensitivity_dBm + Antenna Total Gain_dB (ideally)

The TRP can normally be accurately calculated by using the conducted power from the module and the total gain (or efficiency) of the antenna.

For the case of the TIS, the actual results can be more diverse, depending on the device design (e.g. if there is noise coming from the PCB, the antenna will catch that noise and will affect the TIS performance). This parameter is even more critical in NTN, as the satellite signal will be weak at reception, due to the losses from the different factors explained in the previous section, that will be more susceptible to being affected and reduce the TIS performance.

Note that not only will the antenna play an important role, but the conducted power and, especially the sensitivity of the module, will be critical to make sure the overall combination of module + antenna will close the link budget.

Type of Antennas for NTN

We discussed the key antenna parameters and what would be good to close the link budget. However, to have the best antenna option for closing the link budget is not always possible – it also depends on the user case. It’s not the same static devices where the antenna can be guaranteed to always be facing the sky that a portable device that can be changing position all the time. Also, if the device is a satellite-only device or a hybrid device, where typically a single antenna must cover all the cellular bands, including the NTN bands.

Hybrid Devices (Terrestrial + NTN)

Hybrid NTN-IoT devices must support both terrestrial cellular bands and satellite NTN bands. This allows devices to operate seamlessly on LTE networks where coverage exists and switch to satellite where terrestrial connectivity is unavailable.

Many LTE antennas already cover the S-band, but not the L-band. Optimizing existing LTE designs to support NTN bands is a practical path for hybrid devices:

• Designed for cellular (LTE/Cat-M/NB-IoT) plus NTN frequency bands
• Support operation across multiple bands, including sub-GHz, L-band, and S-band
• Compact, embedded formats enable easy integration into IoT devices

By combining terrestrial and satellite coverage in a single antenna, these solutions simplify design while reducing cost and footprint. However, it will challenge the performance to close the link budget.

Figure 3. Embedded Cellular/LTE + NTN Antennas

In order to improve the NTN performance based on the directions explained in section 3, the NTN bands should be extracted, and a dedicated antenna could be used to achieve the circular polarization required to improve the performance. This will work only if the positioning of the device guarantees that the antenna can always be facing the sky.

Satellite-Only Devices

For satellite-only devices, antenna design depends on whether the use case is static or mobile. In static scenarios, the device orientation can be controlled, and circularly polarized antennas bring significant advantages. Circular polarization improves gain stability, mitigates multipath fading, and increases robustness against misalignment.

In the case of the mobile devices, if the antenna position can be guaranteed to always face the sky, then the circular polarized antennas can provide the performance improvement.

Traditional patch antennas, however, present challenges: narrow bandwidth makes it difficult to cover both Rx and Tx in L- and S-bands. In most cases, two separate patches are required, or otherwise the full band is not fully covered (e.g. using GPS patch antennas for the L-band, not all the frequencies for Tx and Rx are covered in the band n255).

To address these limitations, Laser Direct Structuring (LDS) techniques enable compact, circularly polarized antennas with wide bandwidth and improved azimuth gain, offering a path to more practical IoT integration, improving the link reliability even when the satellite is at low angles.

Figure 4. Example of L-band LDS NTN Antenna with RHCP

The Future of NTN: Towards Multi-Band and Multi-Constellation Antennas

The next generation of NTN-IoT devices will demand antennas capable of operating across both the L- and S-bands, supporting multiple constellations such as LEO and GEO, and seamlessly transitioning between terrestrial and satellite networks - all while remaining compact and cost-effective for large-scale deployment.

Emerging manufacturing techniques like Laser Direct Structuring (LDS) enable the development of compact, multi-band antennas with circular polarization. These designs maintain stable gain from zenith to near the horizon, improving link reliability even when satellites are at low elevation angles.

Another promising direction involves active antenna architectures. Some can dynamically adjust their radiation pattern - providing higher gain toward the sky for satellite connections and improved azimuthal coverage for terrestrial networks. Others integrate a low-noise amplifier (LNA) at the receiver front end, enhancing sensitivity and helping close the link budget under weak-signal conditions.

Conclusion

NTN is transforming global connectivity by extending the reach of IoT devices beyond terrestrial boundaries. Yet, this transformation relies on antennas that are efficient, compact, and optimized for low-power satellite communication.

Antennas in LDS technology demonstrates how innovation in antenna design will enable IoT devices to connect from earth to orbit, delivering reliable connectivity wherever it is needed.