This paper presents a digital beamforming architecture based on the discrete Fourier transform, designed for medium-Earth orbit satellite payloads to serve multiple ground users. The system leverages a 16×16 16-point two-dimensional fast Fourier transform (2DFFT) to address the growing demand for high-speed data traffic and adaptable satellite communications. The architecture features a routing algorithm for flexible user allocation to any beam position and a cluster-based linear precoding approach to reduce resource and power consumption. Two versions of the 2DFFT module—quantized and non-quantized—are compared in terms of resource usage, power consumption, and performance. Experimental results show that the non-quantized version provides better power efficiency, while the quantized version removes the need for DSP blocks.

Medium Earth orbit (MEO) constellation is an appealing solution between geostationary equatorial orbit (GEO) and lower Earth orbit (LEO) in terms of latency and number of satellites required. On-board processing of digital beam-former in MEO satellites is an efficient solution for achieving wider bandwidth, increased flexibility, and lower latency. Power constraints, however, make it impractical to digitally create thousands of beams at once. In this paper, area-power efficient digital beamformer architectures are proposed considering key metrics of a typical MEO scenario. The proposed efficient digital beamformer is comprised of a sparse-matrix-based user selection, a 2D discrete Fourier transform (DFT)-based digital beam generation, which is implemented by a fast Fourier transform (FFT) algorithm, and a spatial windowing module for selecting the antenna pattern. Furthermore, architectures of digital beam-former using conventional 2D-FFT approach, fully unrolled 2D-FFT, and an area-power efficient twiddle factor (TF) quantized fully unrolled 2D-FFT are proposed. The spatial windowing architecture concerning 10 × 10 radio frequency chains and sparse matrix architecture for user selection is also proposed. The proposed architectures are implemented targeting Virtex ultrascale FPGA and the area-power utilization is reported. It is noticed that more than 50%-reduction in area and power is achieved with the beamformer incorporating the proposed TF quantized fully unrolled 2D-FFT.

On-board processing of digital beamforming in satellites is an efficient solution for the higher data rates, more capacity, and lower latency, but the available on-board limited power makes it impractical to digitally create thousands of beams at once. A significant portion of the analog hardware in a satellite communications payload can be replaced with highly integrated digital components, which are often more affordable, lighter, smaller, and reprogrammable by employing digital beamforming. In comparison to matrix-by-vector multiplication beamforming, the discrete Fourier transform (DFT) beamformer enables the finer realization of real-time beamformers with reduced circuit complexity and lower power consumption. Fast Fourier transform (FFT) methods can further reduce the computing cost of the DFT computation. Therefore, in this paper, area-power efficient two-dimensional (2D) FFT digital beamforming techniques are analyzed and implemented. The major implementation challenge is to produce N samples per cycle with lower area-power consumption. Fully unrolled 4-bit twiddle factor (TF) quantized FFT is proposed in this regard. The optimization techniques through quantization, truncation, and complex multipliers are thoroughly discussed for efficient implementation. The behavioral and post-route timing simulations are validated, and implementation results like area and power consumption are estimated and compared among conventional , fully unrolled, and the proposed 4-bit TF quantized 2D-FFT.

The weak signal levels experienced at the reception of the messages transmitted by navigation satellites, makes Global Positioning System (GPS) vulnerable to unintentional and intentional interference. This calls for appropriate modelling of GPS signal sources and jammers to assess the anti-jamming and interference mitigation capabilities of algorithms developed to be implemented for GPS receivers. Using a practical simulation model, this work presents an anti-jamming technique based on a novel algorithm. A fully adaptive lattice based notch filter is presented that provides better performance when compared to existing adaptive notch filter based techniques, chosen from the literature, in terms of convergence speed whilst delivering superior performance in the excision of the interference signal. To justify the superiority of the proposed technique, the noise and interference signal power is varied for in a wide dynamic range assessing jamming-to-noise density versus effective carrier-to-noise density performance at the output of the correlator.

This paper addresses the problem of multi-robot coordination in scenarios where the robots may experience unexpected delays in their movements. Prior work by Čáp, Gregoire, and Frazzołi introduced a control law, called RMTRACK, which enables robots in such scenarios to execute preplanned paths in spite of disturbances in the execution speed of each robot, while guaranteeing that each robot can reach its goal without collisions and without deadlocks. We extend that approach to handle scenarios in which the disturbance probabilities are unknown at the start and non-uniform across the environment. The key idea is to `repair' a plan on-the-fly, by swapping the order in which a pair of robots passes through a mutual collision region (i.e. a coordination space obstacle), when making such a change can be estimated to improve the overall performance of the system. We introduce a technique based on Gaussian Processes to estimate future disturbances, and propose two algorithms for testing, at appropriate times, whether a swap of a given obstacle would be beneficial. Tests in simulation demonstrate that our algorithm achieves significantly smaller average travel time than RMTRACK at only a modest computational expense.

In this paper a novel pipelining approach applicable to Winograd Fourier transforms is presented. The novel approach makes use of reconfigurable multiplier blocks to implement the real multipliers required for the transform as well as sharing the hardware resources among additions. The additions are realized using modified forms of butterfly circuits. The novel approach is tested on a 5-point Winograd Fourier transform and the circuit area and power dissipation of the design are estimated using an in-house power estimation tool and compared to the state-of-the-rt approaches.

In this paper we propose a novel receiver for multiple input single output channels. Such approaches are preferred in boosting the diversity within the channel, to combat fading. Our receiver performs a space time block coding technique by making use of a blind algorithm, which is the constant modulus algorithm. Being a blind receiver, no training data streams are required to identify and to equalize the frequency selective communication channel. Different from the state-of-the-art techniques in the literature proposed for the channels with transmit diversity, the channel estimation and channel equalization are implemented all in one receiver without any need for an extra step to perform any one of these two. Furthermore, the receiver was designed by also considering a feedback filter in its equalizer for a better error rate performance. Step by step derivation of our novel receiver is shown in this paper alongside the simulation section, where the performance of our novel receiver is illustrated.