A low-complexity feed-forward I/Q imbalance compensation algorithm

This paper presents a low-complexity adaptive feed- forward I/Q imbalance compensation algorithm. The feed-forward so- lution has guaranteed stability. Due to its blind nature the algorithm is easily incorporated into an existing receiver design. The algorithm uses three estimators to obtain the necessary parameters for the I/Q imbal- ance compensation structure. The algorithm complexity is low due to 1-bit quantization in the estimators. Simulations show that the compen- sation algorithm is able to attain an image-rejection ratio (IRR) of up to 65 [dB] under various imbalance conditions

A Software-Defined Radio Simulation Method using Observer Patterns

A problem with object-oriented simulation models is that internal model states are hidden and cannot be monitored easily. Object-oriented models are essentially black-box models. This article describes a method to expose the internal states of an object-oriented simulation model. Exposure of the states is achieved though application of the Observer software pattern in the form of data sources. Data sources can be connected to a data sink which then receives data from the sources. Connections between data sources and sinks are made though a broker. The globally accessible broker holds information on the available data sources. Some implementation details of a simulation framework\ud based around the method are discussed. The framework is tested using a small simulation example on I/Q imbalance. Although the focus is on software-defined radio and communication systems, the concepts presented here can also be applied to other types of object-oriented simulation

Experimental Verification of a Harmonic-Rejection Mixing Concept using Blind Interference Canceling

Abstract—This paper presents the first practical experiments\ud on a harmonic rejection downconverter, which offers up to 75 dB of harmonic rejection, without an RF filter. The downconverter uses a two-stage approach; the first stage is an analog multipath/ multi-phase harmonic rejection mixer followed by a second stage providing additional harmonic rejection based on blind adaptive interference canceling in the discrete-time domain. The aim is to show its functional operation and to find practical performance limitations. Measurement results show that the harmonic rejection of the downconverter is insensitive to frontend nonlinearities and LO phase noise. The canceler cannot cope with DC offsets. The DC offsets are removed by highpass filters. The signal paths used to obtain an estimate of the interference must\ud be designed to provide as much attenuation of the desired signal as possible

A Two-stage approach to harmonic rejection mixing using blind interference cancelling

Current analog harmonic rejection mixers typically provide 30–40 dB of harmonic rejection, which is often not sufficient. We present a mixed analog-digital approach to harmonic rejection mixing that uses a digital interference canceler to reject the strongest interferer. Simulations indicate that, given a practical RF scenario, the digital canceler is able to improve the signal-to-interference ratio by 30–45 dB

A Blind Interference Canceling Technique for Two-Stage Harmonic Rejection in Down-mixers

This paper presents practical experiments on a harmonic rejection down-mixer, which offers up to 75 dB of harmonic rejection, without an RF filter. The down-mixer uses a two-stage approach; the first stage is an analog multi-path/multiphase harmonic rejection mixer followed by a second stage providing additional harmonic rejection based on blind adaptive interference canceling in the discrete-time domain. The aim is to show its functional operation. The canceler cannot cope with DC offsets. The DC offsets are removed by highpass filters. The signal paths used to obtain an estimate of the interference must be designed to provide as much attenuation of the desired signal as possible. Front-end nonlinearities and DC offsets are discussed

Increased bone mineral density in Aboriginal and Torres Strait Islander Australians: Impact of body composition differences

Bone mineral density (BMD) has been reported to be both higher and lower in Indigenous women from different populations. Body composition data have been reported for Indigenous Australians, but there are few published BMD data in this population. We assessed BMD in 161 Indigenous Australians, identified as Aboriginal (n = 70), Torres Strait Islander (n = 68) or both (n = 23). BMD measurements were made on Norland-XR46 (n = 107) and Hologic (n = 90) dual-energy X-ray absorptiometry (DXA) machines. Norland BMD and body composition measurements in these individuals, and also in 36 Caucasian Australians, were converted to equivalent Hologic BMD (BMDH) and body composition measurements for comparison

A Software-Defined Radio Simulation Method using Observer Patterns

A problem with object-oriented simulation models is that internal model states are hidden and cannot be monitored easily. Object-oriented models are essentially black-box models. This article describes a method to expose the internal states of an object-oriented simulation model. Exposure of the states is achieved though application of the Observer software pattern in the form of data sources. Data sources can be connected to a data sink which then receives data from the sources. Connections between data sources and sinks are made though a broker. The globally accessible broker holds information on the available data sources. Some implementation details of a simulation framework based around the method are discussed. The framework is tested using a small simulation example on I/Q imbalance. Although the focus is on software-d

Réflexions sur l'usage des modèles dans les études de transports et les sciences sociales

The mathematical modelling of human behaviours is extremely common in both theoretical and applied transport studies. This paper begins with an attempt to demonstrate the limits which apply to the reconstruction of a human reality (in this case an origin-destination matrix) by means of a straightforward and commonly used model, the gravity model. These limits stem from the fact that economic, social and political factors and historical aspects are ignored. The reasons for the prevalence of models in transport studies are then discussed as are the consequences of this prevalence: perpetuation of a view of the operation of society which is far from being without political implications, the surrender of the political community to experts, pseudo-scientific justifications for projects for which politicians do not wish to take responsibility