FORTIFY RF 9 Ways to Transform your Antenna Design with 3D-Printed Dielectrics User Guide

FORTIFY RF 9 Ways to Transform your Antenna Design with 3D-Printed

Dielectrics

Specifications

• Printing Technology: Fortify’s Gradient Dielectric 3D Printing
• Materials: Rogers Corporation Radix Printable Dielectric, technical ceramics like 97% pure Alumina
• Surface Finish : Excellent
• Loss Substrate: Low
• Conductor Materials: Bulk copper, bulk silver, silver nano-inks, and more
• Application Areas : Conformal Antennas, Matching Structures, mmWave Radomes

Introduction

The RF Applications Guide provides 9 ways to transform your antenna design with 3D-printed Dielectrics. It offers insights into
Fortify’s Gradient Dielectric 3D Printing Technology and its various applications in the field of antennas.

Product Usage Instructions

Conformal Antennas
To create a conformal antenna using Fortify’s Gradient Dielectric 3D Printing Technology, follow these steps:

1. Design the desired shape of the antenna using suitable CAD software.
2. Ensure that the design includes the necessary provisions for conductor plating.
3. Use Fortify’s DLP-based 3D printer with Rogers Corporation’s Radix or other suitable materials to print the dielectric substrate in the desired shape.
4. Post-process the printed substrate to achieve the desired surface finish.
5. Perform a secondary process of conformal conductor plating using suitable conductor materials like bulk copper, bulk silver, or silver nano-inks.
6. Test the conformal antenna for its performance and make adjustments if necessary.

Matching Structures

To improve antenna feeds using matching structures, such as matching rods, follow these steps:

1. Identify the waveguide feed of the antenna.
2. Select a suitable dielectric matching rod.
3. Carefully insert the matching rod into the waveguide feed, ensuring a secure fit.
4. Test the antenna’s performance with the matching structure in place and make adjustments if necessary.

mmWave Radomes
To create mmWave radomes using Fortify’s technology, follow these steps:

1. Design the radome shape and dimensions according to the specific requirements of the microwave or mmWave application.
2. Select the appropriate material (such as Rogers Corporation’s Radix or technical ceramics like 97% pure Alumina) based on factors like temperature resistance and UV exposure.
3. Use Fortify’s 3D printer to print the radome with the desired shape, thickness, and surface roughness.
4. Post-process the printed radome to achieve the desired surface finish.
5. Mount the radome above the electronics and sensitive antenna components, ensuring proper alignment and secure attachment.
6. Test the antenna system with the radome in place to evaluate its performance and make adjustments if necessary.

INTRODUCTION

3D printed dielectrics are being used in antenna products across a variety of industries ranging from commercial applications in 5g and satellite communications to defense and aerospace applications such as RADAR, electronic warfare, and tactical communications. With Fortify’s high resolution, high throughput composite 3D printing technology, product designers, RF engineers, and researchers are using components like 3D printed RF lenses, radomes, foams, and more to recognize huge improvements in their microwave antenna designs.

In this guide, we introduce nine ways engineers and RF designers use dielectric 3D printing in their products and applications.

Figure 1: Fortify Flux Core printer with a 3D printed part manufactured using Rogers Corporation Radix Printable Dielectric

FORTIFY’S GRADIENT DIELECTRIC 3D PRINTING TECHNOLOGY
Gradient Refractive Index (GRIN) designs are the basis for many of the applications listed below. Fortify enables GRIN technology by printing lattice structures – complex networks of surfaces and pores that have feature sizes significantly smaller than the electromagnetic wavelength. By varying the volume fraction of dielectric material to air in a region of a 3D-printed lattice, a locally effective dielectric constant can be realized. The volume fraction of the lattice can be varied from location to location, enabling the capability of gradient dielectric materials. You can find more details about Fortify’s 3D printed GRIN technology in our recent case study focused on Ku /Ka-band Luneburg Lenses at www.3dFortify.com.

By combining these printing capabilities with low-loss dielectric materials like Rogers Corporation’s Radix Printable Dielectric or Fortify’s own 97% Pure Alumina, a great variety of wide-band, high-performance applications are possible.

1. CONFORMAL ANTENNAS Figure 2: A cone-shaped antenna substrate plated with conformal copper geometries for aerospace and defense applications.

   • What is it?
     A conformal antenna is a combination of a non-planar, low-loss dielectric substrate with metallization applied directly to the printed geometry. The substrate is printed into the desired shape and is conformally plated in a secondary process using conductor materials like bulk copper, bulk silver, silver nano-inks, and more.

   • What problems does it solve?
     These structures enable the integration of antenna components into dimensionally constrained systems – allowing you to fit microwave antennas into areas where typical antennas will not fit. Beyond that, integration reduces the overall bill of materials, minimizing complexity and easing costs. In addition to these advantages, RF designers can consider the potential matching, bandwidth, and radiation pattern improvement that comes from moving antenna designs from planar to 3D.

   • How does Fortify do it?
     Microwave and millimeter wave antennas require excellent surface finish and low-loss substrates to be viable for an application. Using Fortify’s DLP-based high resolution and high throughput 3D printing process combined with microwave materials like Rogers Corporation’s RadixTM, the perfect substrate can be printed for conformal conductor plating.

   • Where is it used?
     Conformal antennas are excellent solutions for aircraft where space is aerodynamically constrained – such as airplanes, drones, and rockets. Conformal antennas are also used in other applications where SWaP (size, weight, and power) are big considerations, such as SATCOM on-the-move and man- carry antenna devices. Anywhere a device needs to be small and lightweight, a 3D-printed conformal antenna is an excellent option.

2. MATCHING STRUCTURES

   • What is it?
     A matching structure is a standalone dielectric component or geometry integrated within a 3D printed design. The structure is used to match the impedance of the antenna to the feed source, allowing the antenna to operate in the desired frequency band with maximum efficiency and improved matching and radiation patterns. This allows the antenna to operate in the desired frequency band with maximum efficiency with improved matching and radiation pattern improvement. These structures are used in radomes, lenses, horns, and more.

   • What problems does it solve?
     Matching structures work to minimize the reflections at the interface of a feed, such as with waveguides or horns – to maximize power transfer and improve the overall efficiency of a system. In the case of a parabolic dish antenna feed, the 3D-printed gradient dielectric rod fits into the feed and works to eliminate noise, optimize dish illumination, minimize spillover loss, and improve the radiation pattern. Figure 3: Neil from the Machining and Microwaves YouTube channel inserting a dielectric matching rod into the waveguide feed for his parabolic dish antenna.Image courtesy of Machining and Microwaves YouTubeChannel.

   • How does Fortify do it?
     Fortify’s technology enables the manufacturing of gradient dielectrics, including continuous equation-based dielectric profiles within any envelope. The gradient dielectric material properties or/and the shape of the printed component can be tuned to serve as a high-performance matching structure.

   • Where is it used?
     Matching structures are found all over the place – but in the case of the dielectric rod for a feed antenna, this is typically found in parabolic dish antennas for downlink communications. Elsewhere, matching is found in nearly every mmWave and microwave antenna system in some capacity. Check out how Neil at the Machining and Microwaves YouTube channel used a matching rod technology to improve his antenna feed!

3. MMWAVE RADOMES

   • What is it?
     A radome is a device that sits above electronics and sensitive antenna components. Radomes are designed and printed to meet the dielectric and geometric needs of high-performance microwave and mmWave applications.

   • What problems does it solve?
     These structures enable the integration of antenna Radomes to provide the necessary environmental protection for the antenna system while also reducing surface reflections, beam distortion, and loss. Radomes need to be manufactured with precise shapes, specific thicknesses, and low surface roughness to be optimized for microwave and mmWave antennas.

   • How does Fortify do it?
     Fortify’s 3D printers print low-loss dielectric material like Rogers Corporation’s Radix and technical ceramics like 97% pure Alumina. These materials can be printed with the shape, radome thickness, surface roughness, and mating features to rapidly create a radome perfect for any antenna. Other characteristics of the application, like temperature resistance and UV exposure, help to define which material works best for any application.

   • Where is it used?
     Radomes are employed in nearly every antenna for the public and private sectors –ranging from telecom base stations and SATCOM terminals, all the way to rocket nose cones and high-speed vehicle electromagnetic windows.
     If you’re working on a radome design for your antenna and you need some support, reach out to set up a call with our antenna application experts!

4. BROADBAND NOSECONE

   • What is it?
     A broadband nosecone is a device that sits above and protects electronics and sensitive antenna components while also having excellent RF transmission characteristics. A nosecone tends to sit at the nose of an aircraft – protecting electronics from the forces and elevated temperatures generated by high-speed travel.

   • What problems does it solve?
     Nosecones provide the necessary environmental protection for the antenna system – and great nosecones will help to improve the system’s performance. By leveraging designs like A, B, or C-type sandwich layered foam construction constructions, nosecones can be made to perform with excellent broadband behavior, enabling wider bandwidth and greater transmission efficiency than typical solid dielectric radome designs. Figure 6: A-type composite foam sandwich nosecone manufactured from 3D printed 97% purity Alumina technical ceramic. A section cut of the nosecone is shown to exhibit the composite structure. The interior and exterior surface of the cone is solid dielectric, where the core is a lightweight, low dielectric constant foam structure.

   • How does Fortify do it?
     Fortify’s 3D printers can manufacture low-loss technical ceramics like 97% pure Alumina Low Shrink Alumina Silicate. Using these materials, along with the freedom of design enabled by 3D printing, composite foams such as the A-type sandwich design (solid, high dielectric constant skins sandwiching a low dielectric constant, lightweight core) can be manufactured.

   • Where is it used?
     Nosecones are typically found on aircraft or other high-speed airborne vehicles in aerospace and defense applications. With the emergence of unmanned vehicles and smart devices, communications across multiple frequency bands have become increasingly critical for modern vehicle designs, and nosecone radomes need to have broadband characteristics to complement them.

5. LOW DIELECTRIC CONSTANT FOAMS

   • What is it?
     A 3D-printed foam is a low-loss, low-dielectric spacer typically used to separate a conductive element (like a patch or a microstrip) from a ground plane. Foams are also used to rigidly fill the interstitial space of antenna elements like stacked patch antennas or cavity-backed slot antennas.

   • What problems does it solve?
     Traditionally sourced low Dk, low-loss foams are typically sold as sheets of material and come in pre-defined thicknesses. This makes them challenging and expensive to form into the correct shape for non-planar applications. During PCB lamination processes, they also tend to crush, compressing the air voids, and changing the dielectric constant. In other applications, non-rigid foams can deflect or deform under high pressures such as on aircraft, negatively impacting antenna performance.

   • How does Fortify do it?
     Fortify’s technology can manufacture low-loss dielectric foams using materials like Rogers Corporation’s Radix. By enabling the design and manufacturing of application-specific, conformal, rigid, low-Dk foams, all the challenges related to traditional foam processing are reduced. With the ability to change the dielectric constant and part strength across the geometry of the part, Fortify provides a unique combination of structural integrity and dielectric properties, tuned for each application.

   • Where is it used?
     Conformal, low Dk foams are used across industries but are primarily found in aerospace and defense applications where lightweight, low dielectric rigid structures are needed such as for radomes or antenna PCBs.. Figure 7: Diagram of a coplanar waveguide-fed patch antenna with a 3D printed low dielectric constant foam substrate. The grey-colored structure represents the low dielectric constant 3D printed material, and the gold-colored structures represent conductive elements.
     Figure 8: A diagram of a conformal version of a coplanar waveguide-fed patch antenna. This component could be 3d printed using Rogers Corporation’s Radix Printable Dielectric for microwave and millimeter wave applications. er wave applications

   • Where is it used?
     Conformal, low Dk foams are used across industries but are primarily found in aerospace and defense applications where lightweight, low dielectric rigid structures are needed such as for radomes or antenna PCBs..

6. SWITCHED BEAM ARRAY ANTENNA LENS
   Switched-beam array antennas are an emerging type of antenna architecture that leverages large Luneburg-style lenses for passive beam shaping and steering. Here are two examples of switched beam array antenna lenses
   A. Spherical Lens with Conformal Antenna Feed

   • What is it?
     A Switched Beam Array using a spherical Luneburg-style lens is a high-gain antenna that can generate and point several instantaneous fixed-position beams. In this architecture, a Luneburg lens is fed by an array of antenna feeds placed conformal to the surface of the lens. The Luneburg lens naturally has a focal point at the surface of the lens and enhances the gain equivalently for all feeds.

   • What problems does it solve?
     Most current beamforming and beam-steering antennas rely on active phase shifting by way of phase shifters and amplifiers to create and point high-gain beams. In the case of a Phased Array antenna, the aperture shrinks as you scan a beam, meaning that gain reduces as a beam moves from boresight – this is called scan loss. In the case of frequency-domain multiplexing systems, the feed antennas in a SBA can all be receiving or transmitting at the same time.

   • How does Fortify do it?
     Luneburg lenses for SBAs in microwave and mmWave applications are easily manufactured using our lattice-based gradient dielectric manufacturing technology. Luneburg lenses combined with a conformal feed array enable gain enhancement equivalently for all feeds – meaning that there is no scan loss.

   • Where is it used?
     Spherical Switched Beam Array Lens Antennas can currently be found in areas where a lot of 5G throughput is required such as at stadiums and festivals. These devices are also deployed in terrestrial ground-to-satellite communication stations for both commercial and military applications for higher frequencies ranging into Ka-band.
     B. Semi-spherical Lens with a Flat Bottom

   • What is it?
     A Switched Beam Array with a flat bottom has a dielectric distribution like a Luneburg-style lens, but the gradient is changed to accommodate all the feed elements co-located on the same flat face below the antenna. This antenna architecture utilizes the lens as a passive phase shifter to steer and focus the beams.

   • What problems does it solve?
     While also having many of the benefits of the spherical SBA mentioned earlier, the flat bottom significantly simplifies the design and assembly of the lens feed structure. In a traditional Phased Array, the phase shifter IC is the limiting factor for the bandwidth of operation. The phase delay in a lens is a true time delay and has a very wideband operation. Therefore, providing that the feeds themselves are wideband (or can be easily swapped), the SBA can be a much cheaper, more wideband, lower power consumption, and lower heat generation beam-steering solution than a phased array. Figure 10: Switched Beam Antenna (SBA) lens printed using Rogers Corporation Radix Printable Dielectric with a flat bottom mounted to a base plate. The base plate supports an array of waveguide feed antennas, where each antenna creates a discrete beam. A Styrofoam cover is also used as lens protection.

   • How does Fortify do it?
     Fortify’s gradient dielectric technology enables more complex dielectric distributions than the simple Luneburg Lens distribution. Using design algorithms and RF optimization workflows, non-analytical dielectric distributions are designed and easily manufactured. With optimization, the lens can be compressed into a smaller footprint for integration into more space-constrained applications.
     For more information about the flat-bottomed SBA lens shown in the photos, send us a note to set up a meeting for a short presentation!
     Figure 11: (Left) SBA mounted in a test chamber for characterization in the 3.5 to 8.2 GHz frequency range. Signal strength versus angle was characterized. The lens system is only limited by antenna feed selection – the lens is naturally wide band and has a cutoff frequency ranging above 18 GHz. (Right) Polar diagram showing the beams created by each waveguide feed.

   • Where is it used?
     Like the Spherical SBA, flat-bottomed SBAs are great options for defense applications in electronic warfare, ground-to-air or ground-to-satellite communications, cellular base stations, and more.
     To learn more about how physically large lenses are designed and built, read our white paper on the RF performance impacts of lens segmentation and assembly.

7. HORN LENSES
   Horn lenses are 3D-printed lenses designed to sit in front of a high-gain horn antenna with the intent of increasing the performance of the horn plus lens antenna system. Below, we introduce two applications for horn lenses.
   A. Point-to-Point Focusing

   • What is it?
     A point-to-point focusing horn lens is a cylindrical lens that sits in front of a horn with a dielectric distribution tailored for optimal performance. The lens is mounted a nominal distance from the horn, has a larger cross-section than the horn, and is used to increase the gain and improve sidelobe levels.

   • What problems does it solve?
     The point-to-point focusing horn lens is significantly shorter than a comparable horn antenna with the same gain – allowing for smaller footprint antennas with similar or improved performance. Horn lenses of this type have been implemented onto existing antenna systems to adjust or augment the system performance on the fly.

   • How does Fortify do it?
     Again, by leveraging gradient dielectric 3D printing, the lens dielectric gradient is optimized for the highest performance. The optimization also includes variables like distance from the horn and the thickness of the lens to achieve the desired gain and maximize aperture efficiency.
     The horn lens shown in the images has been presented at several conferences including IEEE AP-S/URSI and International Microwave Symposium in 2023. If you’d like a copy of our conference paper, please send us a note!

   • Where is it used?
     Horn lenses of this type are mostly found in test and measurement systems used to characterize the RF behavior of materials or devices. Horn lenses are typically deployed to increase the gain of an existing system or be included in the native design of a new horn plus lens antenna.
     Figure 12: A point-to-point focusing lens is shown mounted to a Ka-band feed horn in a test chamber. This lens has a Luneburg-lens style radial dielectric gradient and is mounted to the horn with a 3D printed fixture and was characterized from 20-25.5 GHz. Tests demonstrated a ~5-6 dB of additional gain over the bare horn across the entire tested range.
     B. Wideband Matching and Gain Improvement

   • What is it?
     Somewhat different from the point-to-point focusing lens is the wideband matching and gain improvement horn lens. This lens is paired with a wide bandwidth horn such as a dual or quad ridge horn and is typically mounted directly to the face of the horn. The lens leverages matching structures like those introduced earlier in this guide.

   • What problems does it solve?
     Wideband horns like dual or quad ridge horns have excellent bandwidth but suffer from poor matching, low gain, and very low aperture efficiency on the high end of their frequency band. The aperture efficiency can reach as low as 15%. Introducing a 3D printed dielectric lens with an optimized distribution can address all these underperforming characteristics, and significantly increase system performance.

   • How does Fortify do it?
     Lenses such as these rely on Fortify’s 3D printed GRIN technology for the lens and matching structure design but also leverage the flexibility of 3D printing to incorporate solid fixturing elements for snapping directly onto the horn antenna itself without the need for additional components.

   • Where is it used?
     These devices are great for use in point-to-point applications in public and private 5G and fixed wireless backhaul links as well as for very wide band test and measurement systems.

8. FIELD OF VIEW-ENHANCING LENS FOR PHASED ARRAY ANTENNA
   What is it?
   A field-of-view enhancing lens is a type of lens designed to pair with a phased array to increase the field of view of an array out to +/-90 degrees from boresight. The lens contains a dielectric distribution designed to guide the RF waves to and from the antenna while keeping the scan loss to a minimum.

9. What problems does it solve?
   State-of-the-art phased array systems are typically limited to a field of view of of +/- 60 degrees from boresight. In the scenario where 360-degree coverage is required, three or more phased array antennas would need to be deployed. Therefore, wider coverage comes with significantly greater infrastructure cost and complexity.

10. How does Fortify do it?
    By leveraging a higher dielectric constant printable dielectric material from Rogers Corporation, a greater range of effective dielectric constants can be created using Fortify’s printing technology. Combining that manufacturing capability with optimization algorithms and relevant design inputs, a FOV- enhancing lens was designed to increase the FOV of a COTS phased array out to +/- 90 degrees.

11. Where is it used?
    This lens antenna has applications spanning a wide range of industries – wherever phased arrays are currently being used. This includes applications in RADAR, Electronic Warfare, 5G, Satellite Communications, tactical communications, and more. We have excellent data on our Field of View demonstrator to share – reach out now to set up a meeting with our applications engineering team!

12. CONSTANT-K LENS

    • What is it?
      A constant-K lens is a type of lens where the dielectric constant does not vary across the part. In this lens, the focusing behavior is generated by shaping the profile of a lens.

    • What problems does it solve?
      In the cases shown here, despite performing across very wide bandwidths, Vivaldi antennas lack radiation performance at higher frequencies. By pairing a lens with this antenna, the system realizes reduced sidelobes due to reduced aperture phase error, and the result is higher gain and improved radiation pattern at frequencies up to 60 GHz.

    • How does Fortify do it?
      Using Fortify’s latticing approaches, a device of a discrete dielectric constant can be created to replicate the dielectric constant of any number of existing RF polymer materials. In this case, Fortify printed a custom-shaped lens with a constant dielectric constant of 2.1 Dk, with the intent to replace an existing Teflon lens design concept. The printed structure added improved phase matching and higher gain at the higher frequencies. The dielectric constant of the resultant constant-K lens could be tuned to lower or higher Dks, depending on the desire of the designer.

    • Where is it used?
      This lens antenna is best used in ultrawideband applications in 5G and satellite communications, microwave imaging, and RADAR. However, these design concepts could be extended to other frequency ranges for different applications and material dielectric constants. Figure 15: Broadband balanced antipodal Vivaldi antenna (BAVA) mounted in a chamber for radiation pattern characterization. Image courtesy of San Diego State University Antenna and Microwave Laboratory.

FAQ

• Q: What materials can be used for conformal conductor plating?
  • A: Conductor materials like bulk copper, bulk silver, silver nano-inks, and more can be used for conformal conductor plating.
• Q: Where are mmWave radomes typically used?
  • A: mmWave radomes are used in various applications ranging from telecom base stations to SATCOM terminals and rocket systems.

CONTACT US
Interested in learning more about how Fortify’s technology is unlocking freedom of design for RF engineers? Ready to take the next step in enhancing and transforming your antennas?
Visit us at www.3DFortify.com or email us at [email protected]

References

• AT&T Official Site | Our Best Wireless & Internet Service
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