Kenneth C. Rovers

Spurious-Free Dynamic Range of a Uniform Quantizer

Quantization plays an important role in many systems where analog-to-digital conversion and/or digital-to-analog conversion take place. If the quantization error is correlated with the input signal, then the spectrum of the quantization error will contain spurious peaks. Although analytical formulas describing this effect exist, numerical evaluation can take much effort. This brief provides approximations for the spurious-free dynamic range (SFDR) of a uniform quantizer with a single sinusoidal input, with and without additive Gaussian noise. It is shown that the SFDR increases by approximately 8 dB/bit, in case there is no noise. Generalizing this result to multitone inputs results in an additional 2 dB/bit per additional tone. Additive Gaussian noise decorrelates the sinusoid(s) and the quantization error, which results in a dramatic increase in SFDR.

DVB-S Signal Tracking Techniques for Mobile Phased Arrays

A system that uses adaptive beamforming techniques for mobile DVB-S reception is proposed in this paper. The purpose is to enable DVB-S reception in moving vehicles. Phased arrays are able to electronically track the desired signal during dynamic behaviour of the vehicle the array is mounted on. The proposed system uses blind beamforming to adapt the array steering vector to changing signal (conditions and) directions. Movement of the vehicle, the phased array is mounted on, leads to modulus and phase deviations at the beamformer output. An extended version of the CMA algorithm is used to adapt the steering vector weights to compensate for those deviations. For simulation of the proposed system a model of vehicle dynamics is used to generate realistic antenna data. Simulation of the proposed system based on this antenna data shows appropriate corrections for modulus and phase deviations.

The problem with time in mixed continuous/discrete time modelling

The design of cyber-physical systems requires the use of mixed continuous time and discrete time models. Current modelling tools have problems with time transformations (such as a time delay) or multi-rate systems. We will present a novel approach that implements signals as functions of time, directly corresponding to their mathematical representation. This enables an exact implementation of time transformations and as an additional advantage enables local control over time. A representation of components and signals in both domains is provided, together with composition operators to allow the specification of signal flow diagrams.

Adaptive Beamforming Using the Reconfigurable MONTIUM TP

Until a decade ago, the concept of phased array beam forming was mainly implemented with mechanical or analog solutions. Today, digital hardware has become powerful enough to perform the massive number of operations required for real-time digital beam forming. While more and more applications are using beam forming to improve the communication channel utilization both in space and frequency, many dedicated digital architectures are proposed for the processing. By using a reconfigurable architecture, the same hardware platform can be reused for different applications with different processing needs. In this paper, we present a reconfigurable Multi-processor System-on-Chip based solution for phased array processing that supports advanced tracking mechanisms to continuously receive signals with a mobile receiver. An adaptive beam former for DVB-S satellite reception is presented, that uses a Constant Modulus Algorithm to track satellites. The processing of a receiver with 64 antennas and 3 beams is mapped on a reconfigurable processor named Montium TP. The total implementation of such a receiver requires about 570 clock cycles on a single Montium TP, but can also be partitioned over multiple Montium TPs to support larger phased arrays.

Hardware/Software Co-design Applied to Reed-Solomon Decoding for the DMB Standard

This paper addresses the implementation of Reed-Solomon decoding for battery-powered wireless devices. The scope of this paper is constrained by the digital media broadcasting (DMB). The most critical element of the Reed-Solomon algorithm is implemented on two different reconfigurable hardware architectures: an FPGA and a coarse-grained architecture: the Montium, The remaining parts are executed on an ARM processor. The results of this research show that a co-design of the ARM together with an FPGA or a Montium leads to a substantial decrease in energy consumption. The energy consumption of syndrome calculation of the Reed-Solomon decoding algorithm is estimated for an FPGA and a Montium by means of simulations. The Montium proves to be more efficient

Mobile satellite reception with a virtual satellite dish based on a reconfigurable multi-processor architecture

Traditionally, mechanically steered dishes or analog phased array beamforming systems have been used for radio frequency receivers, where strong directivity and high performance were much more important than low-cost requirements. Real-time controlled digital phased array beamforming could not be realized due to the high computational requirements and the implementation costs. Today, digital hardware has become powerful enough to perform the massive number of operations required for real-time digital beamforming. With the continuously decreasing price per transistor, high performance signal processing has become available by using multi-processor architectures. More and more applications are using beamforming to improve the spatial utilization of communication channels, resulting in many dedicated digital architectures for specific applications. By using a reconfigurable architecture, a single hardware platform can be used for different applications with different processing needs. In this article, we show how a reconfigurable multi-processor system-on-chip based architecture can be used for phased array processing, including an advanced tracking mechanism to continuously receive signals with a mobile satellite receiver. An adaptive beamformer for DVB-S satellite reception is presented that uses an Extended Constant Modulus Algorithm to track satellites. The receiver consists of 8 antennas and is mapped on three reconfigurable Montium TP processors. With a scenario based on a phased array antenna mounted on the roof of a car, we show that the adaptive steering algorithm is robust in dynamic scenarios and correctly demodulates the received signal.

Designing a dataflow processor using CλaSH

In this paper we show how a simple dataflow processor can be fully implemented using CλaSH, a high level HDL based on the functional programming language Haskell. The processor was described using Haskell, the CλaSH compiler was then used to translate the design into a fully synthesisable VHDL code. The VHDL code was synthesised with 90 nm TSMC libraries and placed and routed. Simulation of the final netlist showed correct behaviour. We conclude that Haskell and CλaSH are well-suited to define hardware on a very high level of abstraction which is close to the mathematical description of the desired architecture. By using CλaSH, the designer does not have to care about internal implementation details like when designing with VHDL. The complete processor was described in 300 lines of code, some snippets are shown as illustration.

UniTi: Unified Composition and Time for Multi-domain Model-based Design

To apply model-based design to embedded systems that interface with the physical world, including simulation and verification, current tools fall short. They must provide mathematical (model) definitions that stay close to the specification of the system. They must allow multiple domains, such as the continuous-time, discrete-time and dataflow domain, in a single model including well-defined interaction. They must support model transformations for refining a model during development. And most importantly, they must accurately include and simulate different notions of time in the model. UniTi is a model-based design flow and modelling and simulation environment that delivers on all these aspects. It is based on components that are signal transformations, and therefore mathematical functions. However, in each domain the representation of a signal differs. As components have the same structure in each domain, we can use unified composition operators to represent multiple domains in a single model. Furthermore, this composition provides a unified perspective on time in the domains, even though we differentiate between different notions of time. Time becomes a local property of the model, allowing us to represent and simulate time transformations such as time delays exactly without losing efficiency. Finally, model transformations are defined for such components, which are used for refining and developing the model and which are guided by the design steps in the design flow. We will formally define the domains, composition operators and transformations of UniTi and verify the approach with a case study on a phased array beamforming system.

Mixed continuous/discrete time modelling with exact time adjustments

Many systems interact with their physical environment. Design of such systems need a modelling and simulation tool which can deal with both the continuous and discrete aspects. However, most current tools are not adequately able to do so, as they implement both continuous and discrete time signals as consisting of separate values at a single global simulation clock. The consequence is that simulation, of a time delay for example, either yields inaccurate results or becomes inefficient.