Cellular Antennas for your DAL device

Overview

This is information on cellular antennas for Digi devices running the DAL Operating System.

Antenna Terminology

Internal antennas: An antenna can be concealed within the casing of a device, as seen with most smart phones. Internal antennas are potentially more prone to interference due to the close grouping of electrical components.

External antennas: Situating antennas further away from the rest of the circuit board can help alleviate interference due to electrical components by maximizing a device's natural reach. Instead of sitting inside the device directly next to the modem or transceiver, they screw into place using SMA connectors and protrude from the equipment (think "rabbit ears").

MIMO: Multiple-Input and Multiple-Output (MIMO) technology expands the throughput capacity of a transceiver by leveraging multiple antennas to simultaneously convert RF signals into data (or vice versa), providing faster transfer speeds as a result. Think of it (loosely) as Carrier Aggregation for antennas—once again combining individual lanes into a single, coordinated superhighway. Note that 2x2 MIMO antennas have two antennas for transmitting and receiving while 4x4 MIMO antennas have four antennas.

5G NR FR1 (Sub-6 GHz): New Radio Frequency Range 1.  These antennas are an evolution of existing LTE designs and sizes. They are similar to the antennas used in 4G LTE, with common types including dipole, monopole, PIFA, IFA, and loop antennas. The design challenges mainly involve balancing smaller device sizes with larger antenna bandwidths.

5G NR FR2 (mmWave): New Radio Frequency Range 2.  These antennas operate at higher frequencies and require more advanced designs due to significant signal propagation challenges. Phased-array antennas are necessary to achieve feasible cell sizes and fully utilize the potential bandwidth and throughput of 5G technology. These designs help compensate for the severe path losses associated with mmWave signals by increasing antenna gain.

Antennas tested by Digi

Note: Antenna information has been compiled by Digi to assist customers in selecting the best solution for their application and business needs.  Availability and pricing may vary.  Customers should test and validate antennas for their specific use case.

These antennas are omni-directional, that is, they offer the ability to send/receive signals from any direction. Directional antennas may improve RF sensitivity, but they will require an expert knowledge to find a specific cellular tower and maintain the ongoing fine-tuning that may be required to keep the antenna positioned properly. Due to the challenges of directional antennas, Digi typically focuses on MIMO omni-directional models.

For a list of antennas tested by Digi, refer to the Antennas tested by Digi section in the EX15 User Guide.  Expand the section on the bottom-left to view them.

Number of Antennas

• For Digi devices that use CAT M1 cell modems, one antenna should be used.  This would be applicable to such Digi products as the 1002-CMM1-GLB Core Modem, or the Connect IT Mini.
• Regarding 2x2 MIMO antennas being used with 4G-capable Digi devices, one 2X2 MIMO antenna (using the two elements / SMA connectors) should be used per cell modem.
• Regarding 2x2 MIMO antennas being used with 5G-capable Digi devices, two 2X2 MIMO antennas (using the four elements / SMA connectors) should be used per cell modem.
• For 4G-capable Digi devices, a 4x4 MIMO antenna may be used with only two of the four elements connected.   Review the respective product's user guide to determine which two elements should be attached to which two antenna connectors.
• Regarding 4x4 MIMO antennas being used with 5G-capable Digi devices, one 4X4 MIMO antenna (using the four elements/ SMA connectors) should be used per cell modem.
• If using only one antenna element per cell modem on a 4G-capable DAL-based Digi device, and/or only two antenna elements per cell modem on a 5G-capable DAL-based Digi device, you should set the Network → Modems → Modem → Antenna parameter to Main.
  • Regarding 4G, the antenna element should be attached to the Main antenna connector of the Digi device.
  • Regarding 5G, review the respective product's user guide to determine which two ports (likely Main + one of the other three) the two antenna elements should be attached to.

4G versus 5G

Note that not all 4G antennas work with 5G modules and not all 5G antennas work on 4G modules.  This all depends on the frequency specs of the antenna, module, and cellular provider.

Digi Antennas

Indoor antennas come with certain Digi cellular devices.  Please check the models page, of your device, to view the “What’s in the box”.  Antennas do not come with any Core modems.  Accessory Kits, some of which include antennas, are available for certain devices. 

Digi does not currently sell outdoor antennas. 

Please note the frequencies and other specifications are available, for each Digi antenna, under the Products page.   

Purchasing Antennas

If you wish to discuss or purchase new antennas, please contact Digi’s Sales department by going to https://www.digi.com/contactus/digi-sales

They will be able to provide options for you.

Purchasing Antennas outside of Digi

Digi does provide recommendations for antennas.  Please be sure to note the bullets below when purchasing antennas as well as other sections in this article:

• Verify you have good quality antennas that match the frequency and bands on your module and carrier.
  • Please check the specifications, of the DAL device or Core modem, for the bands of the radio.
• Most Digi devices use industry standard female, center pin, 50 Ω SMA connectors to affix antennas to the internal cellular radio.  This information should be in the respective product's user guide.
• An extension cable can also enhance the reach of a device; however, that cabling causes attenuation—or a degradation in signal quality—due to the distance the signal travels.
• Please see “Number of Antennas” above.

Placement

• In general, you should place your antennas where you get best signal.  This will take testing.  Items such as network bands, signal strength, and your cellular providers cellular tower location, will play a part in determining this. 
• Note that obstructions will also play a role.  Internal clutter, such as motors, lights, or metal, may cause poor SINR (signal-to-interference-plus-noise ratio). 
• Verify you have good quality antennas that match the frequency and bands on your Digi device (its cell modem specifications) and carrier.
• Whenever possible, reposition the Digi device itself rather than relying on antenna extension cables, which can degrade signal quality.

Signal Strength for Cellular Antennas

Signal strength for 5G connections

For 5G connections, the RSRP value determines signal strength.

• Excellent: > -65 dBm
• Good: -64 dBm to -80 dBm
• Fair: -81 dBm to -90 dBm
• Poor: < -90 dBm

Signal strength for 4G connections

For 4G connections, the RSRP value determines signal strength.

• Excellent: > -90 dBm
• Good: -90 dBm to -105 dBm
• Fair: -106 dBm to -115 dBm
• Poor: -116 dBm to -120 dBm
• No service: < -120 dBm

Tips for improving cellular signal Strength

If the signal strength LEDs or the signal quality for your device indicate Poor or No service, try the following things to improve signal strength:

• Move your DAL device to another location.
• Try connecting a different set of antennas, if available.
• Use extension cables.

To find device specific information on the Digi Support page, including the data sheet: https://www.digi.com/support

To find device specific information on the Digi Products page, including specifications: https://www.digi.com/products