Patent Application
20250079721
High-gain, direct radiating phased array antennas (DRAs), such as for use on a communication satellite, tend to have a relatively large profile. For example, it can be difficult to satisfy mechanical and thermal design constraints as the profile of such a DRA shrinks. However, shrinking the profile can provide certain features. For example, providing such a small profile DRA can help facilitate stacking a high number of satellites in a single launch vehicle for deployment.
A further understanding of the nature and advantages of various embodiments may be realized by reference to the following figures. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by letter and/or a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
In recent years, there has been a move toward convergence of satellite and cellular networks to support and enhance global connectivity, including in remote, rural, and maritime regions where terrestrial infrastructure tends to be limited or non-existent. For example, the 3rd Generation Partnership Project (3GPP), a body responsible for development and maintenance of global cellular standards, has introduced technical standards and specifications to allow non-terrestrial networks (NTNs) to be part of fifth generation (5G) cellular network architectures. These and other technological developments seek to integrate satellite communications with 5G New Radio (NR) frameworks and/or other terrestrial cellular capabilities by specifying network functions, interfaces, and the like.
Integrating satellites with terrestrial cellular frameworks can involve overcoming several technical obstacles, such as latency of ground-to-satellite links. However, such integration can also provide several features. One feature is that use of satellites can extend cellular coverage to geographically isolated areas that otherwise do not have access to terrestrial infrastructures (e.g., cell towers). A related feature is that extending coverage can also extend support for remote emergency services, Internet of Things (IoT) and other deployments, and the like. Another feature is that satellite links can be used as redundant (e.g., backup) communication links in the event of terrestrial network failures, which can improve the reliability and resilience of the network. Another feature is that certain satellite features can be used to enhance support for secure government communications. Another feature is that satellite links can be used to help with load balancing and with offloading of traffic from congested terrestrial links (e.g., in densely populated areas, or at high-demand periods of time).
Technical standards and specifications for NTN extensions of cellular networks can identify specific frequency bands for satellite operations within the 5G spectrum to increase compatibility and decrease interference. Some current NTN approaches use S-band for communications between terrestrial 5G networks and satellites, where the satellite tends to be low earth orbit (LEO) and/or geostationary Earth orbit (GEO) satellites. S-band satellites generally operate in a frequency range of approximately 2 to 4 Gigahertz (GHz), which is part of the so-called “S-band” of the electromagnetic spectrum. The S-band tends to be well-suited for NTN uses because it manifests particularly good performance with respect to range, bandwidth, atmospheric penetration, and other factors.
For context,
Antenna systems of S-band satellites often include large deployable antennas, such as parabolic antennas, for communication with ground stations and user terminals. In the illustrated satellite 100, the antenna system 120 is shown as a direct radiating antenna (DRA) composed of an array of patch radiating elements, as described herein. The antenna system 120 is coupled with a face of the satellite main body 110. Embodiments of the DRA antenna (or antennas) are configured for dynamic beamforming. Beamforming can be used to dynamically focus beams on particular (e.g., high-demand) areas, to support beam hopping, to optimize coverage, to manage interference, and/or to provide other features. This capability supports mobile 5G users and addresses varying traffic loads. Although not explicitly shown, the antenna system 120 can also include antennas for telemetry, tracking, and command (TT&C) operations, for inter-satellite communications, and/or for other purposes.
In some embodiments, the satellite 100 is part of a constellation of such satellites. The satellite constellation can be designed to effectively expand a cellular network (e.g., a 5G network) for global (or regional) coverage. Embodiments can be designed to provide high-capacity, high-throughput communication links for direct-to-device communication services. Some implementations additionally use the satellite constellation to provide backhaul support for terrestrial portions of the infrastructure. In such a constellation, the satellites are arranged in one or more orbits (e.g., LEO and/or MEO). The satellites are in communication with a network of ground stations, such as gateway terminals. The ground terminals can provide ground-to-satellite communication links, interfaces between the satellite and terrestrial portions of the infrastructure, and certain command and control functions for the satellites. The satellites may also be in communication with each other (e.g., with adjacent satellites in the same orbit and/or with satellites in adjacent orbits) via inter-satellite links (ISLs).
Although descriptions herein refer specifically to 5G cellular networks, S-band communications, and the like, techniques described herein can be applied to any suitable high-gain, patch antenna-based satellite DRAs. For example, techniques described herein can be extended to other cellular technologies, such as sixth generation (6G) cellular technologies. Similarly, as new NTN standards and specifications are developed, techniques described herein can be extended to any suitable frequency bands, such as the L-band (1-2 GHZ), C-band (4-8 GHz), Ku-band (12-18 GHz), Ka-band (26.5-40 GHz), V-band (40-75 GHz), Q/V-band (33 75 GHZ), millimeter wave bands above 75 GHz, etc.
The illustrated radiating element configuration 200 includes a radiating element 210. The radiating element 210 is a microstrip antenna, or “patch” antenna. Typically, the radiating element 210 acts as a resonator at a fundamental mode, with the electric field distribution over the radiating element 210 resembling a half-wave dipole pattern along its length. As such, for a square radiating element 210, each side length is typically designed to be approximately one half of the wavelength of the fundamental frequency (e.g., the carrier) to be received. In some cases, the effective wavelength is shorter than the free space wavelength of the fundamental frequency because of a higher dielectric constant of the substrate material of the radiating element 210. Still, the S-band frequency range generally corresponds to wavelengths of between approximately 15 centimeters (cm) at 2 GHz and approximately 7.5 cm at 4 GHZ, or a square radiating element 210 side length of between approximately 3.75 cm to 7.5 cm. Circular radiating elements 210 (i.e., circular patches) tend to be designed with a diameter that is approximately ⅓ the wavelength of the fundamental frequency to be received. Often, numerical methods, computer simulations, empirical formulas, and/or other techniques are used to accurately predict the resonant frequency of a radiating element 210 design and thereby to optimize radiating element 210 dimensions for particular reception characteristics.
As illustrated, the radiating element 210 (a “patch”) can be coupled with a coupler 205. Ports of the coupler 205 are labeled with numbers 1-4 in circles (representing “port 1” through “port 4”). In an illustrative operational case, port 1 is fed with a transmit chain to produce RCHP at port 3, and port 2 is fed with a receive chain to produce LHCP at port 4. Although RCHP and LHCP are orthogonal, there can still be some self-interference when signals with those polarization orientations are concurrently produced by a same radiating element 210. Techniques are used to mitigate such self-interference.
The coupler 205 is illustrated as a “single-box branch-line” coupler. Such a single-box coupler 205 can provide a single null for matching and is thus narrow-band. In an alternative embodiment, the coupler 205 is implemented as a “2-box branch-line” coupler. Such a 2-box coupler 205 can provide good coverage to two bands. Embodiments of the coupler 205 are implemented as “strip-line” or “micro-strip” couplers, which can be reduced in size by using an appropriate dielectric value and/or by “stubbing up” (i.e., adding one or more extensions or protrusions (stubs) to the radiating patch or to the feed line for impedance matching, bandwidth enhancement, resonance fine-tuning, and/or the like).
The transmit path of each radiating element configuration 300 includes a power amplifier (e.g., illustrated as a solid-state power amplifier, SSPA) 310, and the receive path of each radiating element configuration 300 includes a low-noise amplifier (LNA) 320. The SSPA 310 includes semiconductor devices (e.g., field-effect transistors (FETs), bipolar junction transistors (BJTs), etc.) that amplify radio frequency (RF) signals to power levels desired for transmission by its respective radiating element 210. Each SSPA 310 can include components for input signal conditioning (e.g., filters), amplification (e.g., one or more stages of semiconductor amplification), output matching and filtering (e.g., matching circuits and filters), and control and protection (e.g., gain adjustment, overdrive protection, load mismatch protection, temperature compensation, etc.). Each SSPA 310 can be implemented as one or more SSPAs. Each LNA 320 is configured to amplify weak signals received by its respective radiating element 210 with minimal addition of noise. The LNA 320 effectively increases the sensitivity and selectivity of the receive path, such as by improving signal-to-noise ratio (SNR) and other receive characteristics. Each LNA 320 can include an amplification stage, input and output matching networks, biasing circuitry, stability enhancements, and/or other components.
In effect, each radiating element configuration 300 includes a transmit path through its respective SSPA 310 and a receive path through its respective LNA 320. The transmit path and the receive path can be designed to operate in different respective sub-bands of the S-band. For example, embodiments can be designed so that each radiating element 210 transmits and receives simultaneously on both RHCP and LHCP. To support the radiating element 210 transmitting and receiving simultaneously on both LCHP and RHCP, embodiments include diplexers 325. As illustrated, each radiating element configuration 300 can include two diplexers 325 (e.g., radiating element configuration 300a is illustrated as including diplexer 325-1a and diplexer 325-2a, and radiating element configuration 300n is illustrated as including diplexer 325-1n and diplexer 325-2n).
Each diplexer 325 is a passive radio-frequency device that combines or splits two different frequency bands. The diplexer 325 permits two different signals (i.e., the receive and transmit signals) at distinct frequencies (i.e., the high sub-band and low sub-band) to share a common path (i.e., the radiating element 210 path), while maintaining isolation between the signals. Each diplexer 325 has three ports: a high-sub-band port, a low-sub-band port, and a common port. A high-pass filter (or filter network) is coupled between the high-sub-band port and the common port, and a low-pass filter (or filter network) is coupled between the low-sub-band port and the common port. The low-pass and high-pass filters are designed to have minimal insertion loss in their respective passbands and high isolation in their respective stopbands, such that the receive and transmit frequency bands can be used simultaneously without interference.
In each radiating element configuration 300, the respective high-sub-band ports of the two diplexers 325-1 and 325-2 can be coupled with outputs from the SSPA 310, the respective low-sub-band ports of the two diplexers 325-1 and 325-2 can be coupled with inputs to the LNA 320, and the respective common ports of the two diplexers 325-1 and 325-2 can be coupled with feed ports 315-1 and 315-2 of the radiating element 210. As illustrated by arrows next to each feed port 315, one feed port 315-1 of each radiating element 210 is configured for resonance parallel to a first pair of edges of the radiating element 210, and the other feed port 315-2 of each radiating element 210 is configured for resonance parallel to the other pair of edges of the radiating element 210 (i.e., in orthogonal directions).
In the patch antenna array 400, the spacing between radiating elements 210 (the “patch spacing” 420) can be approximately one-half of the free-space wavelength for full horizon-to-horizon scan without grating lobes. Since this scan volume may not be practical based on certain design constraints, the patch spacing 420 can be relaxed to slightly larger values. As noted above, in embodiments having square radiating elements 210, the side length of each radiating element (the “patch size”) can also be approximately one-half of the wavelength. However, the wavelength used for the patch size may be the wavelength in the dielectric board material of the substrate on which the radiating elements are mounted, not the free space wavelength. Using such values, overlaps of radiators are avoided, and spacing may be adjusted to provide better isolation between radiators.
As illustrated, the patch antenna array can include a stack-up of planar layers, including at least a first side of the planar stack-up and a second side of the planar stack-up. For example, from one perspective, the first side is the top side of the planar stack-up and the second side is the bottom side of the planar stack-up. The radiating elements 210 are mounted to the first side of the planar stack-up, and active components including at least the SSPAs 310 and LNAs 320 are mounted to the second side of the planar stack-up. In some embodiments, additional discrete components, such as beamformers, phase-shifters, etc. are mounted on the second side of the planar stack-up. In some embodiments, power, control, and signal networks are implemented on one or more layers between the first side of the planar stack-up and the second side of the planar stack-up.
In some embodiments, at least a first layer 402 is disposed closes to the first side, a second layer 404 is disposed closest to the second side, and a third layer 406 is disposed between the first layer 402 and the second layer 404. For example, the layers can be implemented as a multi-layer printed circuit board (PCB). The first layer 402 can be a ground plane with which the radiating elements 210 are electrically and physically coupled. The ground plane can act as a reflector to help direct the radiation pattern of the radiating elements 210. The SSPAs 310 and LNAs 320 are mounted to the third layer 406. Although not explicitly shown, the diplexers 325 (
Particularly when used with a large patch array (e.g., over one thousand radiating elements 210), the compact design of
In addition to the layers described with reference to
In some embodiments (e.g., in addition to or as an alternative to the graphoil), a thermally conductive bonding material is used as the thermal conduction layer 510. For example, one or more compressible, thermally conductive materials is disposed between the third layer 406 and the thermal radiation layer 520, or between the third layer 406 and the graphoil. For example, the compressible, thermally conductive material can include one or more thermal pads, polymer matrices filled with thermally conductive materials, thermal gap fillers, thermal phase change materials, thermally conductive foams, and/or thermally conductive elastomers.
In some embodiments (e.g., in addition to or as an alternative to the graphoil and/or thermally conductive bonding material), the thermal conduction layer 510 is implemented as a vapor chamber layer. The vapor chamber layer is implemented as a flat, thin enclosure containing a small amount of liquid under vacuum conditions. The inner surfaces of the enclosure can be lined with wicking materials, such as sintered metal power, mesh screens, grooves, etc. Heat from the third layer 406 and components mounted thereon causes liquid inside the vapor chamber layer to absorb the heat and change to a vapor phase. The vapor travels to cooler regions of the enclosure, where it condenses back to its liquid phase, thereby releasing the latent heat that was absorbed.
The thermal conduction layer 510 is thermally coupled with a thermal radiation layer 520. In some embodiments, the thermal radiation layer 520 is an optical solar reflector layer. In other embodiments, the thermal radiation layer 520 is coated with a mirror material. In other embodiments, the thermal radiation layer 520 is painted white. In operation, heat conducts from the third layer 406 (and components mounted thereon), through the thermal conduction layer 510, and into the thermal radiation layer 520, where the heat can be radiated into space and away from the patch antenna array 500.
At stage 608, embodiments can form an array of radiating element configurations on the planar substrate. Such forming can include at least stages 612 and 616 for each of the plurality of radiating element configurations. For example, at stage 612, embodiments can couple a microstrip radiating element to the first side of the planar substrate in a respective first-side (e.g., top-side) array position. At stage 616, embodiments can couple several (e.g., two) active amplifier components to a second side of the planar substrate in a respective second-side (e.g., bottom-side) array position opposite the first-side array position. For example, the active components for each radiating element configuration includes at least a solid-state power amplifier and a low noise amplifier.
The direct radiating phased array antenna are designed to communicate signals according to a carrier frequency, such as in the S-band. In some embodiments, as described herein, the microstrip radiating element is a square patch radiating element having a side length approximately equal to one half of a wavelength of the carrier frequency in the planar substrate. In some embodiments, the array of radiating element configurations is arranged so that a patch spacing between the radiating elements in the array is at least one half of a free-space wavelength of the carrier frequency.
In some embodiments, providing the planar substrate at stage 604 includes forming the substrate as a planar stack-up having a first layer, a second layer, and a third layer. In such embodiments, the microstrip radiating element can be coupled at stage 612 to a first side of the first layer, and the active amplifier components can be coupled at stage 616 to a second side of the third layer. In some such embodiments, providing the planar substrate at stage 604 further includes forming the second layer to include, for each of the array of radiating element configurations, a pair of passive filter components (e.g., a pair of diplexers) each coupled between the plurality of active amplifier components and a respective feed port of the microstrip radiating element.
At stage 620, embodiments can thermally couple a thermal conduction layer with the second side of the planar substrate. As described herein, some embodiments of the thermal conduction layer include a graphoil layer, a compressible thermally conductive bonding material, a vapor chamber layer, and/or any feasible combination thereof. At stage 624, embodiments can thermally couple a thermal radiation layer with the thermal conduction layer. As described herein, some embodiments of the thermal conduction layer are implemented as an optical solar reflector.
Having described several example configurations, various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. For example, the above elements may be components of a larger system, wherein other rules may take precedence over or otherwise modify the application of the invention. Also, a number of steps may be undertaken before, during, or after the above elements are considered.
This application claims priority to U.S. Provisional Patent Application No. 63/535,432, filed Aug. 30, 2023, entitled “Direct Radiating Phased Array Antenna Systems,” the entire disclosure of which is hereby incorporated by reference, for all purposes, as if fully set forth herein.
| Number | Date | Country | |
|---|---|---|---|
| 63535432 | Aug 2023 | US |
