This paper presents the design and optimization of highly efficient radio frequency power amplifiers (RFPAs) for driving acousto-optic tunable filters (AOTFs) in spaceborne applications. High efficiency is critical in such applications to minimize power consumption, heat dissipation, and enhance system reliability. However, RFPAs typically generate significant harmonic content and heat, which can induce thermal effects and compromise the optical measurement accuracy of AOTFs. This work investigates the trade-offs among efficiency, bandwidth, harmonic suppression, and tunable output power. Analytical modeling and parametric optimization are employed to derive practical design strategies. The results offer valuable insights for the development of efficient RF driving systems for AOTFs.

This paper presents a novel platform for the efficient analysis, design, and optimization of ideal single-ended Class-E power amplifiers (PAs). It employs a comprehensive time-domain analytical model, which extends the conventional design space by incorporating variable duty cycles, variable voltage switching (VVS), and variable derivative voltage switching (VDS), enabling precise evaluation of key performance parameters such as harmonic efficiency, maximum output power capability, maximum operating frequency, and device stress. To facilitate practical design verification, an open-source, GUI-based CAD tool has been developed, providing researchers with an accessible and interactive environment for analysis and validation. In addition, a Python-based global optimization algorithm is integrated into the framework to automate component selection and enhance design robustness, particularly in scenarios involving finite DC-feed inductance. The accuracy and applicability of the proposed methodology are validated through nonlinear harmonic balance (HB) simulations. The results confirm the model’s ability to predict system behavior with high fidelity, making it a valuable resource for both academic and industrial design applications.

Spaceflight has become more accessible than ever due to increased launch reliability and significant advances in electronics. Among these advancements are small-sized PocketQubes, which are small satellites (5 × 5 × 5 cm for 1P) that can be built using commercial off-the-shelf components. A critical subsystem in these satellites is the communication system, which requires compact and deployable antennas. This work focuses on the design of deployable antennas for TU Delft’s upcoming Delfi-Twin PocketQube mission, operating in the 10 m and 6 m amateur bands. The Shape Memory Alloy (SMA) nitinol was selected as the antenna material due to its favorable mechanical and deployment characteristics. However, its high electrical resistivity limits antenna efficiency. This study investigates multiple conductive coating techniques for nitinol antenna wires, aiming to improve electrical performance while maintaining mechanical flexibility. The coatings are evaluated through electrical resistance measurements and mechanical bending tests. Among them, a DuPont ME164 ink showed the most promising performance, significantly reducing wire resistance compared to bare nitinol while preserving mechanical integrity. These results address a novel conductive coating for efficient SMA-based antennas and demonstrate a valid approach for improving deployable antennas in small-satellite applications.

In recent years, advancements in semiconductor technologies have significantly transformed Radio Frequency Power Amplifiers (RFPAs), enhancing their efficiency, size, and performance. Despite these advancements, the design of RFPAs remains intrinsically linked to the specific applications for which they are intended. What proves effective in one context, such as communication technologies, may not be equally suitable in others, such as scientific instruments. This discrepancy highlights the lack of a systematic approach to RFPA design that can be applied across different applications. This paper delves into the fundamental concepts of RFPA design, adopting a comprehensive perspective. It further introduces an alternative categorization of RFPAs, thereby providing a generalized design approach.

Acousto-Optic Filters are versatile devices with a range of applications in modern optics. Their technology has reached a mature industrialability. They are particularly valuable in fields requiring precise wavelength selection and fast switching capabilities, making them essential tools in various applications. The generalisation of their use has led to new applications still requiring specific developments.We present the design and validation of an AOTF for spectro-polarimetry analysis which provides a constant spectral resolution over a wide spectral band. The variation of the spectral resolution is made possible by the manufacture of a transducer divided into multiple electrodes allowing to play on the interaction length easily by activating and deactivating the electrodes. In addition, the power distribution supplying the electrodes can be modulated, which offers the possibility of finely controlling the spectral template.The device developed has an acoustic cut of 5°, operating from 450 to 800 nm. We opted for a transducer equipped with 5 electrodes. This strategy makes it possible, depending on the power supply conditions, to modulate the selectivity of the filter by a factor of 4 for a given wavelength and to maintain a constant selectivity of the order of 10 nm over the entire operating range.

In space applications, CubeSats are used for all kinds of commercial and research purposes. These small satellites are launched in such large numbers that from a pollution point of view it makes sense to return them intact to Earth. To establish this, a dedicated reentry is needed. During this reentry process, the CubeSat has to make use of a heatshield which deforms due to multiple forces acting upon the structure. In order to monitor this heatshield, this study aims at investigating, designing, simulating, and testing the integration and readout of fiber Bragg gratings (FBGs) into a mock-up heatshield, in order to monitor its shape. Therefore, a mock-up of a CubeSat and its accompanying heatshield is constructed to simulate the realistic use of FBGs. Based on the external dimensions of the heatshield, the study gives a practical installation pattern for the FBGs. A 3-D simulation model of the heatshield and accompanying CubeSat is built. To achieve deformation in this 3-D model, the study proposes an algorithm based on single-point data. Using existing OROCOS/ROS middleware, the study establishes a comprehensive system for setting up and reading out FBGs in order to gather information on the heatshield’s status. Finally, after testing the mock-up heatshield set, the system can reflect the deformation of the heatshield in real-time in the 3-D model. Additionally, the system can save the entire deformation process of the heatshield as a series of model files, which can be used for sophisticated static analysis.

One of the main challenges for users applying an AOTF as a commercial off-the-shelf component for optical wavelength filtering, is the lack of detailed manufacturing information on critical parameters. Information such as diffraction angles, the precise RF driving frequencies required for momentum-matching conditions, as well as the data for each wavelength across a certain optical spectrum is not always easily available. To obtain this information, users must perform physical tests to configure the optimal frequencies, diffraction angles, and incidence angles for each wavelength of interest which is labor-intensive and costly.This research uses an optimization algorithm applied to an analytical model which can characterize key angles related to the AOTF’s crystallographic axis, such as the crystallographic axis angle θc, the tilt-angle α, as well as facet inclination angles β and γ. First, diffraction testing on an AOTF is done, by recording both output ray angles and the momentum-matching frequency. Then the optimization algorithm is chosen and applied to the analytical model to determine the optimal parameters for θc, α, γ, and β. With these parameters, the AOTF’s behavior can be extrapolated to multiple wavelengths, which not only saves time, but also enables more versatile planning of optical setups.

Memristors have emerged as prospective two-terminal elements, having applications in memory, neuromorphic systems, and analog circuits. Biological materials such as egg albumin exhibit memristive behavior, displaying a distinctive pinched hysteresis signature in their current-voltage characteristics. However, such memristive behavior must be mathematically modeled to gain insights into the material’s operation and utilize it in various circuit applications. This article proposes a novel SPICE-level framework for fabricated egg albumin memristors using Joglekar’s memristor model. Experimental current-voltage characteristics are used to calibrate the SPICE model, ensuring accurate reproducibility of the experimental results. Additionally, the impact of variations in model-specific parameters on dynamic resistance and device performance is explored.

The use of Acousto-Optical Tunable Filters (AOTFs) is well known in ground- and space-based applications. These devices are used in several optical instruments and payloads for monitoring and other purposes. To make use of the filter capability of the AOTF, a dedicated Radio Frequency (RF) chain, consisting of an RF generator and RF amplifier, is needed. An RF generator can be designed in several ways. However, the design of these steering devices for space applications comes with several difficulties and limitations. The mechanical stress due to shock and vibration, the temperature variation, as well as the vacuum environment and radiation levels in which these devices have to perform limits the selection of possible techniques. This paper aims at giving an in-depth overview of space-qualified RF generator techniques using Commercial-Off-The-Shelf available components that usable in the harsh environment of space and applicable in driving AOTFs. Several analog as well as digital generator principles are discussed, substantiated by test results.

Acousto-Optical Tunable Filters (AOTFs) make use of the interaction between sound and light. To generate an ultrasound diffraction grating, a Radio-Frequency (RF) signal is applied to a piezoelectric transducer. The optical pass band can be controlled by adapting the properties of this transducer and the RF-signal. To achieve more precise control of the optical spectral bandwidth, we propose to use a multi-electrode array, consisting of five consecutive transducers. The Voltage Standing Wave Ratio (VSWR) is then used to evaluate the efficiency of the coupling between the RF-signal applied to the transducer and the acousto-optical crystal. A higher VSWR indicates that more power is being reflected back and less is being absorbed by the transducer, which in turn results in a decrease in optical performance. The aim of this paper is to develop an RF driving system capable of compensating for the VSWR behavior, linked to the individual impedance matching network of each transducer. For this, the five transducer setups were electrically characterized. These measurements allow the development of an RF power compensation system, leading to an increase of applied power at the level of each transducer. Hence, the absorbed power at transducer level increases, resulting in improved optical diffraction efficiency.

The distribution and behavior of the vast accumulation of plastic waste in the oceans, often referred to as the 'plastic soup’, are heavily influenced by plastic debris coming from rivers and coastal areas. Currently, the location and dynamics of the oceanic ‘plastic soup’ is already well understood. However, the exact process behind the formation of this plastic soup remains incompletely comprehended. This knowledge gap can be linked, in part, to the absence of worldwide detailed spatiotemporal data collected from ground and space. This is specifically due to the lack of detection and imaging techniques with a high spatial and temporal resolution. To address this gap, an innovative concept is proposed based on
imaging spectroscopy. The goal is to address and further improve the observed spectral signatures of different plastics by imaging the observed scenery. In order to distinguish between these different kinds of plastics, a dedicated optical filtering system with a high resolution and revisit time has to be designed. Therefore, the concept is based on an Acousto-Optic Tunable Filter (AOTF), specifically designed for remote sensing and imaging. In order to achieve a high temporal resolution, being able to capture the evolution and movement of plastic in the oceans, a constellation of satellites are foreseen. Therefore, a low flying platform and deployable optics are introduced. Flying at 300 km altitude instead of a typical > 600 km for Earth observation satellites, reduces the required imaging aperture.

This paper presents a comprehensive analysis of Class-E series-tuned radio-frequency power amplifiers (RFPAs), focusing on their design and optimization for high efficiency and performance. However, achieving optimal performance involves navigating trade-offs among efficiency, bandwidth, harmonic suppression, output power capability, and device stress. This work examines the trade-offs involved in the series-tuned ((Formula presented.)) network and establishes the bounds for its quality factor using computer-aided harmonic balance (HB) simulations. Additionally, it explores optimal harmonic termination strategies to enhance the performance and efficiency of the design. Finally, a novel methodology using harmonic termination is proposed, simplifying the design process by eliminating the need for traditional load-pull extraction methods.

We present an original acousto-optic tunable filter that is able to filter visible light from 400 to 650 nm and is designed to interact simultaneously with two polarizations. The filter shows an adjustable optical bandwidth and apodization capabilities. These features make it suitable for practical spectroscopic applications. Experimental validation is also presented.

Diffraction of optical waves by an acoustic grating is a well-known phenomenon that enables the design of very versatile devices useful in photonic systems. For example, Acousto-Optic Tuneable Filters (AOTFs) can be dynamically tuned by radio-frequency signals. Among possible material choice, tellurium dioxide crystal is often used for practical applications due to its high efficiency. In such a birefringent material, the anisotropic configuration is often used. A feature of this configuration is the sensitivity to optical input polarisation: a selective coupling between polarized modes occurs. The incident must be polarised and
the diffracted mode polarisation is orthogonal to the incident one.
However, during the design process a very specific operation point can be found that ensures the simultaneous diffraction of both the ordinary and the extraordinary optical modes. In this presentation, we introduce the design of AOTF in birefringent crystals and present the main parameters that are subject to trade-off. Acousto-optic diffraction efficiency is sensitive to the so-called phase matching condition between optical wave and the ultrasonic
wave. The offset from synchronicity is considered introducing a phase mismatch parameter. Diffraction efficiency evolution with respect to Bragg condition offset are illustrated. A custom device is finally presented that ensures simultaneous diffraction of both polarisation modes and compared to experimental results.

Acousto-Optical Tunable Filters (AOTFs) are a promising technology, exceptionally suited for advanced applications in spectroscopy and imaging across various scientific fields, including space exploration. This is due to their flexibility and high-speed functionality for precise wavelength selection via periodic modulation of the crystal’s refractive index using sound waves. These AOTFs are in turn driven by Radio Frequency (RF) signals through a transducer creating sound waves inside the crystal. This work presents a detailed comparison of three distinct topologies of Radio Frequency Power Amplifiers (RFPAs) for driving these AOTFs within the 30 to 300 MHz frequency range. The analysis focuses on three critical parameters: efficiency, bandwidth, and linearity, which are essential for optimizing the performance of AOTFs. By evaluating the trade-offs among these parameters, this research aims to identify the most effective design approach for RFPAs in this application context.

Current monitoring systems to detect sporadic E use ground-based setups, ionosondes, and the network of GNSS satellites in order to assess the phenomenon of sporadic E. This paper aims to monitor sporadic E using a miniature space-based platform in an atypical way. The setup consists of multiple radio-amateur beacon systems aboard satellites, each having a specific modulation and transmission scheme. This Radio Amateur Beacon System for the Investigation of the Ionosphere (RABSII) is coupled to a GNSS receiver, revealing the location of the platform. Multiple beacon data streams are sequentially sent from a satellite platform towards the Earth. By receiving and comparing the Signal-to-Noise ratios of these streams using a dedicated ground-based radio-amateur network of receiving stations, the presence of sporadic E can be determined, and a location-based model can be built. The advantage of this miniaturized, low-power, low-cost instrument is its ability to be put on any satellite platform in the future in order to map sporadic E.

Acousto-Optical (AO) devices are not only used for filtering purposes in spectral
imaging, but also in optical communications and spatial tracking systems. Some AO devices with space applications are AO Tunable Filters (AOTFs), Modulators (AOMs), Deflectors (AODs) and Frequency Shifters (AOFSs). Though these device’s applications differ, they are all controlled with Radio-Frequency (RF) signals. These signals are converted by a transducer into an acoustic wave, which propagates inside the AO device. The interaction between the incoming
light and the acoustic waves inside the birefringent AO material creates multiple output beams. This interaction can result in filtering, modulation, deflection or frequency shifting, depending on the AO device in question. This research focuses on the design of a flexible, uniform RF generator, applicable to all AO devices in the space applications domain. The RF output maximizes the performance of the AO device, while the use of components available in space
qualified grades eases integration with future space missions. Its design is a key step towards a miniaturized, space qualified, general-purpose RF generator. This research presents schematics, design and preliminary component test results.

The AOTF-based NO2 camera is a remote sensing instrument primarily aimed at imaging and quantifying the NO2 field above cities or in industrial plumes. The measurement principle consists in acquiring a number of spectral images of the scene at selected wavelengths. Each pixel is therefore recording a discrete spectrum of the radiance collected in its acceptance cone, enabling the retrieval of the NO2 column density in its optical path by application of the DOAS method on the measured spectrum. The core element of the instrument principle is the acousto-optical tunable filter (AOTF). This device works under the principle of the acousto-optical interaction, the coupling of the light electric field with the modulation of the crystal lattice by a shear acoustic wave created by a transducer. The coupling takes place at a single wavelength, and diffracts that part of the spectrum into another direction. By blocking the undiffracted light beam, and imaging the diffracted order, one can capture a monochromatic image of the scene. We propose to expand the capabilities of the NO2 camera by exploiting another aspect of the acousto-optic interaction. The coupling between light and sound actually takes place in a birefringent crystal (TeO2), and one usually works with a single linear polarization of the incoming light (e-light, or o-light). The two polarization components are diffracted in different directions. If the current design is modified such that the two components can be imaged, then an information on the degree of linear polarization of the light can be obtained. In the atmosphere, the scattering of light by air (Rayleigh), and particles (Mie) is controlling the state of polarization of the scattered solar light. Hence, aerosols not only introduce a smooth spectral signatures, but also a change of the state of polarization. The proposed modification of the NO2 camera design can provide some sensitivity on this, potentially enhancing the scientific return of the instrument with aerosol retrievals capabilities. The new instrumental design will be presented, and vector radiative transfer simulations will be produced to estimate the benefit of this change.

Currently, the amount of space debris is increasing rapidly due to the tremendous amount of satellite launches. Having an autonomous re-entry system aboard satellites at their end-of life, creates possibilities in the frame of lowering space debris, as well as for sample return from space. This paper aims at describing two possible deployment systems for the Thermal Protection System. Also, the integration of an onboard Fibre Bragg Grating-based shape monitoring system, coupled to an adaptive control system is described. Additionally, several re-entry trajectory steering systems are investigated, combined with an inflatable concept analysis. The combination of a deployable Thermal Protection System, an onboard closed feedback loop for shape monitoring, and the ability to adapt the shape of the Thermal Protection System, creates the possibility to design an autonomous dynamically steered re-entry system.

In the last couple of years, the use of weak signal propagation reporter (WSPR) has grown significantly in the radio amateur community and beyond. This protocol allows to probe potential propagation paths between radio transceivers, operating at a low-power level. The protocol decodes the received signals and translates them into appropriate signal-to-noise ratio levels, which reveal the possible propagation paths between the transmitter and receiver using ionospheric reflections. In this article, specifically the 160-m radio amateur band is addressed. This band used less intensity for WSPR communication, compared to the other radio amateur bands (80 m and 40 m). Additionally, the 160-m band has specific features such as the link between propagation performance and the Earth’s electron gyro-effect. The aim of this article is to address these features experimentally. First, two identical 160-m band WSPR receiver stations are conditioned to compare the performance of different 160-m band antennas. Each setup, separated by a limited distance, generates almost identical SNR reports, allowing the comparison between the two antennas. Second, a more extended experimental investigation of the propagation path performance on the 160-m band reveals information on the radio wave behaviour between the transmitter and receiver. The first experiment allowed the identification of the most optimal antenna, specifically in the 160-m band. The second experiment shows that the SNR values can vary depending on the polarization shift of the received signal. Possibly, this can be linked to the effect of the magnetic field of the Earth via the electron gyro-frequency.