Photonic Microwave Signal Processing Based on Opto-VLSI Technology

Deep learning (DL) for Radio Frequency (RF) signal processing has gained significant traction, with drone classification emerging as one of the key applications in security-sensitive contexts. However, existing DL approaches often require considerable computational resources, lack robustness to adversarial attacks, and operate in static, ground-based settings. The integration of Universal Software Radio Peripheral (USRP) modules into drones now enables real-time, on-board RF signal processing, opening new avenues for scalable and responsive security systems. In this work, we present HyperDrone, the first RF signal processing framework based on Hyperdimensional Computing (HDC). HyperDrone employs a resource-efficient ensemble of HDC classifiers, combining diverse encoding strategies to achieve state-of-the-art accuracy in drone detection. This design not only enhances performance over standard HDC models but also significantly improves robustness to adversarial perturbations without the need for adversarial training. Compared to prior works, HyperDrone has up to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1 0} \times$</tex> faster inference and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{2 7} \times$</tex> faster training. It improves few-shot learning accuracy by over 30 % and adversarial robustness by 18 %, with less than 1 % accuracy drop.

Ultra-High Bandwidth Radio Frequency and Microwave Photonic Signal Processing Based on Kerr Micro-Combs

Dissipative solitons relying on the double balance between nonlinear and linear effects as well as cavity loss and gain have attracted increasing attention in recent years, since they give rise to novel operating states of various dissipative nonlinear systems. An optoelectronic oscillator (OEO) is a dissipative nonlinear microwave photonic system with a high quality factor that has been widely investigated for generating ultra-low noise single-frequency microwave signals. Here, we report a novel operating state of an OEO related to dissipative solitons, i.e., spontaneous frequency hopping related to the formation of dissipative microwave photonic solitons. In this operating state, dissipative microwave photonic solitons occur due to the double balance between nonlinear gain saturation and linear filtering as well as cavity loss and gain in the OEO cavity, creating spontaneous frequency-hopping microwave signals. The generation of wideband tunable frequency-hopping microwave signals with a fast frequency-hopping speed up to tens of nanoseconds is observed in the experiment, together with the corresponding soliton sequences. This work reveals a novel mechanism between the interaction of nonlinear and linear effects in an OEO cavity, extends the suitability and potential applications of solitons, and paves the way for a new class of soliton microwave photonic systems for the generation, processing, and control of microwave and RF signals.

This paper describes a new technique for detecting faulty components such as cracked insulators and faulty surge arresters on power lines. The technique utilises radio frequency (RF) pulses emitted from the faulty components as the monitoring parameter. The high frequency radio pulses are captured using a biconical antenna with a frequency range of 30 MHz to 300 MHz. The radio frequency pulses are stored analysed and characterised using signal processing. Good characterisation of RF pulses in the time domain has been achieved using parameters obtained from statistical analysis such as mean median, peak and auto-correlation. Second analysis method applied for characterising the pulses is the fast Fourier transform (FFT). In order to extract more informative features from the RF pulses, a third analysis, joint time-frequency transformation, is used. These three different methods have successfully revealed unique signatures of different faulty conditions on power line components.

We have proposed, analyzed, and demonstrated a high-isolation photonic microwave mixer using an integrated, dual-stage balanced-bridge Mach-Zehnder modulator. The proposed balanced photonic microwave mixer provides not only high isolation between radio frequency (RF) signal and local oscillator (LO) ports, but also excellent isolation between intermediate frequency (IF) and RF/LO ports without any filters. In this paper, the structure, principle, and operation settings are discussed in detail. Experimental results showed >60 dB electrical isolation between RF and LO ports and >50 dB isolation between IF and RF/LO ports in a demonstrative photonic microwave mixer. This device can extend the bandwidth of a modulator and have wide applications in RF photonic links where RF signal conversion and processing are required.

High speed Analog-to-Digital Converters (ADCs) are key components for enhancing high-speed communication systems, such as broadband satellites at millimeter wave frequencies [1] and extremely high-throughput wireless systems [2]. Tens of gigahertz ADCs are required to cope with the increasing need of real-time digital signal processing of broad bandwidth analog RF signal in direct digital receivers. Electronic ADCs have inherent limitations for reaching high bandwidth with an appropriate resolution [3] due to the high timing jitters of electronics clocks, state of art values over 100 fs for [4]. We are studying an All-Optical Analog-to-Digital Converter (AOADC) based on an Electro-Optic (EO) polymer deflector [5] for achieving higher than 20 GHz of bandwidth with a 6 bits of resolution, taking advantage of much lower timing jitters of modes-locked lasers on one hand and very good materials qualities of EO polymers on the other hand (excellent velocity matching between the microwave signals and optical waves in polymeric materials and EO coefficient up to 350 pm/V versus 31 pm/V of the popular inorganic crystal LiNbO 3 ). The EO deflector converts magnitude variation of the analog RF voltage, applied on its Coupled Mirco-Strip (CMS) driving electrodes, into variations of deflection angle of an optical leaky beam out of the optical deflector using the linear EO effect (Pockels effect). This variation of deflection angle as result of the applied RF signal is then quantized using optical windows followed by an array of high-speed photodetectors. This paper reports design optimization of an EO deflector based on polymer materials. On the one hand, the leaky optical waveguide is optimized for achieving up to 6.3 bits of resolution, on the other hand, a transition from coplanar waveguide pads (CPW) to the CMS line is designed for RF characterization of optical deflectors by means of Ground-Signal-Ground (GSG) probes. Experimental validation of 2 cm long of via-free CPW-CMS transition built on a 40 µm thick Benzo Cyclo Butene (BCB) polymer shows a bandwidth higher than 25 GHz. This transition is very helpful for packaging and connectorization of photonic-microwave devices.

This paper describes realizable acousto-optic configurations for the implementation of phased array beamformers. The simple system is capable of generating a distribution of wideband radio frequency (RF) signals with controlled phases. A laboratory demonstration model of the acousto-optic beamformer was built using a pair of Bragg cells and a 10-channel fiber-detector array. Experimental results show that a large phase excursion is obtainable simply by tuning the frequency of the control signal. 1. INTRODUCTION The practical implementation of beamformers for phased array antennas has long been recognized as a challenging technical issue. Simpler and better beamforming techniques are needed to provide the controlled RF amplitude and phase exitations to be fed to the large number of phased array elements. In the conventional microwave implementation the phased array beamforming is performed by the use of individually controlled phase shifters and variable gain amplifiers in the signal path of each phased array element. For large arrays the required RF hardware becomes bulky and complex. The high power consumption of the phase shifter network also poses a major problem.Recently, there has been growing interest in the optical implementation of the phased array beamformer.1 3 The optical approach offers many potential advantages such as high operating frequency and wide bandwidth, immune to radio frequency interference (RFI), small size, low weight, etc. A few methods for the optical beamformer have been pro­ posed. The basic idea is to perform the beamforming at optical wavelengths using spatial light modulators (SLM) and downconverting to the microwave domain by heterodyning with a frequency-shifted reference light beam. This paper discusses several configurations of a phased array beamformer using acousto-optic (AO) techniques.In the proposed approach, AO Bragg cells were used for both the optical beamforming and frequency-shifting purpose. Experimental results were obtained with a ten-channel, one-dimensional beamforming breadboard using two Bragg cells. Both the RF carrier frequency and the phases are independently controlled by tuning the Bragg cell frequencies. The method can be extended to two-dimensional beamforming.

Introduction Microwave links serve important communication, signal processing and radar functions in many commerical and military applications. However, the attenuation of microwave RF signals in cables and waveguides increases rapidly as the frequency of the signal increases, and it is specially high in the millimeter wave range. Optical fibers offer the potential for avoiding these limitations for the transmission of RF signals. Photonic microwave links employ optical carriers that are intensity modulated by the microwave signals and transmitted or distributed to optical receivers via optical fibers. Since the optical loss for fibers is very low, the distance for photonic transmission and distribution of microwaves can be very long. When the modulation of an optical carrier is detected at a receiver, the RF signal is regenerated. Figure 1.1 illustrates the basic components of a simple photonic microwave link. Since the objective of a photonic microwave link is to reproduce the RF signal at the receiver, the link can convey a wide variety of signal formats. In some applications the RF signal is an unmodulated carrier – as for example in the distribution of local oscillator signals in a radar or communication system. In other applications the RF signal consists of a carrier modulated with an analog or digital signal.

This paper presents a comparative study of two approaches for detecting and analyzing acoustic microwaves in piezoelectric materials, with a focus on Lithium Niobate (LiNbO₃) substrates. The first approach models acoustic microwave propagation in piezoelectric structures using an interdigital transducer (IDT) to excite electro-elastic waves. It examines various wave modes, including secondary surface waves, leaky waves, bulk waves, and skimming bulk waves, while applying wavelet transform for efficient signal detection. Two wavelet functions—Mexican-hat and Morlet—are evaluated in terms of their capability to identify acoustic wave singularities and their effectiveness in microwave signal processing. The second approach introduces a machine learning framework based on Support Vector Machines (SVM) to detect ultrasonic pulses and reveal wave patterns that are typically undetectable using conventional methods. By classifying the real and imaginary components of attenuation coefficients and acoustic velocity, this method yields more accurate values and enhances the modeling of ultrasonic pulse propagation. While the wavelet-based approach emphasizes signal processing for wave detection, the SVM-based method demonstrates superior performance in identifying complex wave patterns and provides higher accuracy in ultrasonic pulse modeling, thereby supporting the development of advanced acoustic microwave devices.

This paper investigates the effect of radio frequency (RF) interference on the performance of very high-speed digital subscriber line (VDSL) system. It is shown that a blind equalization is extremely difficult in the presence of RF interference. A receiver structure, incorporating an adaptive notch filter (ANF) and hybrid DFE (H-DFE), is proposed to mitigate the effect of RF interference on the VDSL system. The use of an ANF before the DFE yields reliable blind equalization as well as performance improvement. It is also shown that the H-DFE structure employed in the proposed receiver outperforms the conventional DFE or the noise predictive DFE structure in the presence of RF interference.

Protecting COVID-19 Vaccine Transportation and Storage from Analog Cybersecurity Threats

Photonic integrated circuits are playing an increasingly important role in the implementation of microwave photonic systems for the generation and processing of microwave signals. In this tutorial, techniques to generate and process microwave signals using photonic integrated circuits (both InP and silicon based) will be discussed.

Dual frequency combs are emerging as highly effective channelizers for radio frequency (RF) signal processing, showing versatile capabilities in various applications including Fourier signal mapping, analog-to-digital conversion and sub-sampling of sparse wideband signals. Although previous research has considered the impact of comb power and harmonic distortions in individual systems, a rigorous and comprehensive performance analysis is lacking, particularly regarding the impact of phase noise. This is especially important considering that phase noise power increases quadratically with comb line number. In this paper, we develop a theoretical model of a dual frequency comb channelizer and evaluate the signal to noise ratio limits and design challenges when deploying such systems in a high bandwidth signal processing context. We show that the performance of these dual comb based signal processors is limited by the relative phase noise between the two optical frequency combs, which to our knowledge has not been considered in previous literature. Our simulations verify the theoretical model and examine the stochastic noise contributions and harmonic distortion, followed by a broader discussion of the performance limits of dual frequency comb channelizers, which demonstrate the importance of minimizing the relative phase noise between the two frequency combs to achieve high signal-to-noise ratio signal processing.

We propose and demonstrate a monolithically integrated mode division multiplexing (MDM) photonic system for parallel radio-frequency (RF) signal processing using a silicon platform. Two independent lowpass integrated microwave photonic filters (IMPFs) are successfully demonstrated using the proposed scheme. Full integration of active and passive devices ensures small footprint and good performance for microwave photonic applications. The adoption of MDM extends the parallel processing capability of a single wavelength line. The first order transverse electric (TE1) and second order transverse electric (TE2) modes are utilized for two IMPFs, with minimum bandwidth 3.7 and 3.8 GHz, respectively. Furthermore, by elaborately controlling the micro-ring based mode convertors, the continuous tuning of bandwidth is achieved from 3.7 to 8 GHz for TE1 and 3.8 to 7.6 GHz for TE2 based IMPFs.

A study of the parameters of the radio path was carried out to substantiate the possibility of expanding the integrated multi-level spectrum of 5G/6G and increasing the efficiency of the station equipment of the next generation information communication systems. The paper presents the results of research into the bandwidth of the transmission channel in the THz range, taking into account the transmission power and noise of the components of modern telecommunication systems, as well as the influence of atmospheric attenuation. The idea of ​​a new spectrum, possibilities and problems of using the THz range for both communication and scanning were presented. It also describes the process of modeling and measuring new channels along high-frequency bands, for scenarios with large aperture arrays, non-terrestrial networks, and scanning in millimeter and THz bands. Improved methods for solving technical problems identified in 5G systems, such as mobility and coverage, as well as implementation problems of telecommunications equipment, are identified. In particular, to facilitate the optimal design of radio technologies in 6G systems, it is necessary to model transmission channels with higher accuracy. In addition, to improve the transmission characteristics of millimeter waves, improvements are needed in the radio signal beamforming technology, in particular in beamforming during the scanning process. It is determined that the use of the millimeter range spectrum will be significantly improved due to the improvement of technologies related to materials, radio frequency components and signal processing. Thus, it becomes possible to achieve ultra-high data transfer speed and high-precision scanning resolution. A study of the theoretical foundations of the creation of new devices, the design of electronic, photonic and hybrid receivers, large-sized antenna arrays, gratings on a common crystal or case, and new technologies for the formation of materials for the manufacture of gratings, which ensure the rapid development of communication technologies in the THz range, was carried out. time identified the need for further research in the field of designing powerful high-frequency devices, new materials for antennas and RF transistors, receiver architecture, channel modeling, grating signal processing, and energy efficiency issues. The 6G radio path has been studied, which will contain new capabilities and provide new services using new wireless technologies. It is determined that the 6G system will include many new elements, such as new spectrum, new channels, new materials, new antennas, new computing technologies and new end devices. THz spectrometry at 6G has been found to have many potential applications in health care, industry, food quality control, and the environment, as the vibrational and rotational frequencies of most molecules lie in the THz range. THz spectrometry is of considerable interest due to its ability to provide continuous real-time information through dynamic, non-invasive, passive and non-contact measurements. Of particular note is that THz spectrometry provides results comparable to professional CT or MRI machines, but with a much safer and more portable functional process.