Austin Fikes’s research while affiliated with California Institute of Technology and other places

Large apertures in space are critical for high-power and high-bandwidth applications spanning wireless power transfer (WPT) and communication, however progress on this front is stunted by the geometric limitations of rocket flight. We present a light and flexible 10GHz array, which is composed of dipole antennas co-cured to a glass-fiber composite. The arrays can dynamically conform to new shapes and are flexible enough to fold completely flat, coil into a rocket payload, and pop back up upon deployment in orbit. The array is amenable to scalable, automated manufacturing - a requirement for the massive production necessary for large apertures. Moreover, the arrays passed the standard gamut of space-qualification testing: the antennas can survive mechanical stress, extreme temperatures, high-frequency temperature cycling, and prolonged stowage in the flattened configuration. The elements exhibit excellent electromagnetic performance: a return ratio better than -10dB over ≈1.5GHz, a single lobe half-power beamwidth of greater than 110° suitable for broad beamforming, >92% efficiency, and excellent manufacturing consistency. Moreover, its mechanical durability vis-a-vis extreme temperatures and protracted stowage lends itself to demanding space applications. This lightweight and scalable array is equipped to serve a host of new space-based radio-frequency technologies and applications which leverage large, stowable and durable array apertures.

This paper presents a distributed space solar power generation and transmission system that converts solar insolation into microwave power and beams it to Earth. This system, composed of a power station of large, close-flying modules residing in Geostationary Orbit, can form dynamically programmable focal points on Earth to provide dispatchable power on demand. Modules are composed of flexible phased array sheets hosting a self-synchronizing network of integrated circuits and antennas which convert DC power from photovoltaic cells into radiated RF energy. The sheets are coiled into a compact payload, launched, and deployed in orbit. Presented herein is a detailed technoeconomic analysis of the proposed system, with investigations into such areas as mass, cost to produce and launch, and a levelized cost of energy (LCOE). This analysis demonstrates that the proposed 10GHz system can generate dispatchable power on the ground at 6.641c/kWh---competitive with the cheapest clean energy sources available today.

Large apertures in space are critical for high-power and high-bandwidth applications spanning wireless power transfer (WPT) and communication, however progress on this front is stunted by the geometric limitations of rocket flight. Here, we present a light and flexible 10GHz array, which is composed of dipole antennas co-cured to a glass-fiber composite. The arrays are designed to dynamically conform to new shapes and to be flexible enough to fold completely flat, coil, and pop back up upon deployment. The design was chosen to be amenable to scalable, automated manufacturing - a requirement for the massive production necessary for large apertures. Moreover, the arrays passed the standard gamut of required space-qualification testing: the antennas can survive mechanical stress, extreme temperatures, high-frequency temperature cycling, and prolonged stowage in the flattened configuration. The elements exhibit excellent electromagnetic performance - with a return ratio better than -10dB over a bandwidth of 1.5GHz and a single lobe half-power beam width of greater than $110^\circ$ suitable for broad range beamforming and with excellent manufacturing consistency. Moreover, its mechanical durability vis-a-vis extreme temperatures and protracted stowage lends itself to demanding space applications. This lightweight and scalable array is equipped to serve a host of new space-based radio-frequency technologies and applications which leverage large, stowable and durable array apertures.

Multi-beam relays can be used to overcome the non-line-of-sight (NLOS) issues in millimeter-wave (mm-wave) communication networks that serve many users in an obstruction-rich environment. We demonstrate a modular multi-beam relay array at 28 GHz, which is scalable and fully decentralized. The individual branches of the array are independent and do not need to share a timing reference or be physically located on the same substrate. Multi-beam capability is facilitated by a multi-channel baseband signal conditioning chain that includes a reconfigurable, passive, inductorless, 3rd-order N -path filter with programmable frequency-independent phase shift. This baseband signal conditioning chain enables beams concurrently multiplexed in spatial and frequency domains. We present the theory, design, and operation of the custom RFIC, which enables independent multi-beam relaying. Multiple RFICs are used to create relay arrays. A four-element relay array demonstrates three independently steered beams that utilize the full array aperture with a total wireless throughput of 625 Mb/s.

Complex and dynamic control of radiated fields are advantageous for flexible radio systems, which naturally move, roll, bend, twist, deform, and vibrate. Practical challenges hinder the proliferation of these antenna arrays. This work shows how using radio-frequency microchips reduces system component count, decreases mass to ~0.1 g cm ⁻² , and increases functionality and mechanical flexibility. We develop a general platform for large scale flexible arrays and demonstrate two different 256-elements, 30 × 30 cm ² flexible arrays. By varying supply distribution methods and radiators we show how performance can be optimized for maximum power delivery or physical flexibility. The demonstrated systems conform to curved surfaces with radii of curvatures as low as 23 cm and wirelessly deliver ~ 80 mW of DC power to a 6.7 cm × 11 cm-receiver over one meter away. This paves the way towards the integration of smart arrays in flexible wearables and deployable lightweight airborne systems.

This paper describes Caltech's Space Solar Power Demonstration One (SSPD-1) payload and upcoming mission on Momentus Space Vigoride 5. SSPD-1 is comprised of three experiments each of which demonstrates the performance of a key technology piece in the space environment. We describe the goals of SSPD-1. The three experiments-Alba, DOLCE and MAPLE are discussed. The launch of SSPD-1 is scheduled for November 6, 2022 on Space X's Transporter 6 mission.

We propose a novel design for a lightweight, high-performance space-based solar power array combined with power beaming capability for operation in geosynchronous orbit and transmission of power to Earth. We use a modular configuration of small, repeatable unit cells, called tiles, that each individually perform power collection, conversion, and transmission. Sunlight is collected via lightweight parabolic concentrators and converted to DC electric power with high efficiency III-V photovoltaics. Several CMOS integrated circuits within each tile generates and controls the phase of multiple independently-controlled microwave sources using the DC power. These sources are coupled to multiple radiating antennas which act as elements of a large phased array to beam the RF power to Earth. The power is sent to Earth at a frequency chosen in the range of 1-10 GHz and collected with ground-based rectennas at a local intensity no larger than ambient sunlight. We achieve significantly reduced mass compared to previous designs by taking advantage of solar concentration, current CMOS integrated circuit technology, and ultralight structural elements. Of note, the resulting satellite has no movable parts once it is fully deployed and all beam steering is done electronically. Our design is safe, scalable, and able to be deployed and tested with progressively larger configurations starting with a single unit cell that could fit on a cube satellite. The design reported on here has an areal mass density of 160 g/m2 and an end-to-end efficiency of 7-14%. We believe this is a significant step forward to the realization of space-based solar power, a concept once of science fiction.