Multi-and Wide-Band Single-Feed Patch Antenna

NASA's newly developed antenna is lightweight (at or below 2 grams), low volume (at or below 1.2 cm3), and low stowage thickness (approx. 0.7 mm), all while delivering high performance (at or above 10 dBi gain). The antenna includes a novel design-material combination in a helical coil conformation. The design allows the antenna to compress for stowage (e.g., satellite launch), then self-deploy at the desired time in orbit. NASA's lightweight, self-deployable helical antenna can be integrated into a thin-film solar array (or other large deployable structures). Integrating antenna elements into deployable structures such as power generation arrays allows spacecraft designers to maximize the inherently limited resources (e.g., mass, volume, surface area) available in a small spacecraft. When used as a standalone (i.e., single antenna) setup, the the invention offers moderate advantages in terms of stowage thickness, volume, and mass. However, in applications that require antenna arrays, these advantages become multiplicative, resulting in the system offering the same or higher data rate performance while possessing a significantly reduced form factor. Prototypes of NASA's self-deployable, helical antenna have been fabricated in S-band, X-band, and Ka-band, all of which exhibited high performance. The antenna may find application in SmallSat communications (in deep space and LEO), as well as cases where low mass and stowage volume are valued and high antenna gain is required.

The patch antenna consists of two radiating metal patch elements, a metal feed circuit, choke rings, several alignment spacers, a SMA connector, and a mounting lid giving the antenna a total diameter of 54 mm; small enough to fit in a coffee cup. The signal is carried between the lower patch and the circuit via a coaxial transmission structure, in which the probes are the inner conductor and the antenna structure is the outer conductor. The patch antenna is constructed entirely of metal, offering rugged physical durability while delivering superior performance. This advanced material not only enables the antenna to handle higher power loads (exceeding 10 watts) but also ensures exceptional stability under demanding conditions—outperforming standard patch antennas made with traditional dielectric materials. It is also not susceptible to the manufacturing variability incurred from using dielectrics. Ideally, this metallic design also allows for reentry and reuse across missions. The patch antenna is designed with integrated choke rings to effectively mitigate multipath signal interference, delivering an impressive front-to-back ratio of over 35 dB. Its integrated polarizer circuit enhances signal clarity and boosts overall efficiency, ensuring reliable communication in challenging environments. With support for both right- and left-handed circular polarization, the antenna achieves a co-polarization peak gain of 9 dBi and an axial ratio of less than 3 dB within a wide 50-degree orientation range. These advanced features provide superior signal performance and consistent clarity across diverse applications. Although designed for space and planetary exploration applications, the antenna may also be valuable for terrestrial use cases with rugged conditions. The X-band patch antenna is at technology readiness level (TRL) 5 (component and/or breadboard validation in relevant environment) and is available for patent licensing.

The circularly polarized antenna features an integrated prime-fed S-band and Cassegrain-based Ka-band reflector system. The Cassegrain primary and secondary reflectors are specially shaped for optimal Ka-band gain, while a frequency selective surface on the secondary reflector provides reflectivity at Ka-band, and acts as a transparent dielectric radome for the S-band feed antenna. Design innovations include an improved S-band feed antenna and cross-polarization compensation, improved Ka-band horn, and special shaping of the secondary reflector for ease of fabrication. The technology improves upon prior S-band feed antenna designs to provide mechanical robustness and low cross-polarization over a wide field of view. It also improves the front-to-back ratio, providing much higher signal radiated forward, over an increased bandwidth as well. The Ka-band feed horn is based on a prior NASA innovation, the standard Potter horn, but in this innovation has significantly lower sidelobe level performance. This is achieved by using a modified smooth s-curved interior horn profile rather the the typical conical/cylindrical form typical of the standard Potter horn design. The smooth interior wall is also easier to fabricate than alternative corrugated wall designs. Additionally, a cross-polarization cancellation cup is integrated with the Ka-band horn geometry, with the cup being placed around the neck of the horn in the form of a collar, allowing the two to be fabricated together.

This CLAS-ACT is a lightweight, active phased array conformal antenna comprised of a thin multilayer microwave printed circuit board built on a flexible aerogel substrate using new methods of bonding. The aerogel substrate enables the antenna to be fitted onto curved surface. NASA's prototype operates at 11-15 GHz (Ku-band), but the design could be scaled to operate in the Ka-band (26 to 40 GHz). The antenna element design incorporates a dual stacked patch for wide bandwidth to operate on both the uplink and downlink frequencies with a common aperture. These elements are supported by a flexible variant of aerogel that allows the material to be thick in comparison to the wavelength of the signal with little to no additional weight. The conformal antenna offers advantages of better aerodynamics for the airframe, and potentially offers more physical area to either broadcast further distances or to broadcast at a higher data rate. The intended application for this antenna is for UAVs that need more than line of sight communications for command and control but cannot accommodate a large satellite dish. Examples may be UAVs intended for coastal monitoring, power line monitoring, emergency response, and border security where remote flying over large areas may be expected. Smaller UAVs may benefit greatly from the conformal antenna. Another possible application is a UAV mobile platform for Ku-band satellite communication. With the expectation that 5G will utilize microwave frequencies this technology may be of interest to other markets outside of satellite communications. For example, the automotive industry could benefit from a light weight conformal phased array for embedded radar. Also, the CLAS-ACT could be used for vehicle communications or even vehicle to vehicle communications.

NASA's SDR uses Field-Programmable Gate Array (FPGA) technology to enable flexible performance on orbit. A first-generation FM-modulated transceiver is capable of operating at up to 1 Mbps downlink and 50 kbps uplink, full duplex. An FPGA performs Reed-Solomon (255,223) encoding, decoding, and bit synchronization, providing Consultative Committee for Space Data Systems (CCSDS) and Near Earth Network (NEN) telemetry protocol compatibility. The transceiver accepts data from the onboard flight computer via a source synchronous RS422 interface. NASA's second-generation full duplex SDR, known as PULSAR (programmable ultra-lightweight system-adaptable radio, Figures 1 and 2 below) incorporates command receiver and telemetry transmitters, as well as updated processing and power capabilities. An S-band command receiver offers a max uplink data rate of 300 Kbps and built-in QPSK demodulation. X- and S-Band telemetry transmitters offer a max downlink data rate of 150 Mbps and flexible forward-error correction (FEC) using Reed-Solomon encoding (LDPC rate 7/8 and 1/2 convolution in development), and it uses QPSK modulation. The use of FEC adds an order of magnitude increase in telemetry throughput due to an improved coding gain. An onboard FPGA uses high-speed logic for uplink/downlink and encoding/decoding processes. Balloon flight testing has been conducted and is ongoing for PULSAR.