An interference cancellation technique is described for improving the dynamic range of receivers. A feedforward approach is used to attenuate large interferers before the down-conversion mixer in a receiver. This is accomplished with no measurable impact on the in-band noise performance. Techniques to cancel interference within a narrowband and also in multiple bands are described. Simulation results and measurements from a discrete prototype system are used to validate the approach.

Feedforward Interference Cancellation in Radio Receiver Front-Ends

Multichannel active noise control (MCANC) is widely recognized as an effective and efficient solution for acoustic noise and vibration cancellation, such as in high-dimensional ventilation ducts, open windows, and mechanical structures. The feedforward multichannel filtered-x least mean square (FFMCFxLMS) algorithm is commonly used to dynamically adjust the transfer function of the multichannel controllers for different noise environments. The computational load incurred by the FFMCFxLMS algorithm, however, increases exponentially with increasing channel count, thus requiring high-end field-programmable gate array (FPGA) processors. Nevertheless, such processors still need specific configurations to cope with soaring computing loads as the channel count increases. To achieve a high-efficiency implementation of the FFMCFxLMS algorithm with floating-point arithmetic, a novel architecture based on multiple-parallel-branch with folding (MPBF) technique is proposed. This architecture parallelizes the branches and reuses the multiplier and adder in each folded branch so that the tradeoff between throughput and the usage of the hardware resources is balanced. The proposed architecture is validated in an experimental setup that implements the FFMCFxLMS algorithm for the MCANC system with 24 reference sensors, 24 secondary sources, and 24 error sensors, at a sampling and throughput rates of 25 kHz and 260 Mb/s, respectively.

Practical Implementation of Multichannel Filtered-x Least Mean Square Algorithm Based on the Multiple-Parallel-Branch With Folding Architecture for Large-Scale Active Noise Control

Adaptive fractional Fourier domain filtering

Jharkhand is one of the biodiversity rich states of India because of its origin, diverse physiographic and climatic conditions. It is well known due to its tribal populations, mineral resources, and its vast forest resources. Forest resources are considered as a commodity of high value across the state as most of the locals are dependent for their daily subsistence needs mainly for food and fuelwood. Forests play an important role in the economic, cultural and social lives and supporting rural livelihoods and food security in Jharkhand. Jharkhand is home to tropical moist deciduous and tropical dry deciduous forests and the dominant plant species like Shorea robusta, Diospyros melanoxylon, Pterocarpus mersupium, Gloriosa superba, Butea monosperma, Madhuca longifolia, etc. Commonly extracted forest produces are timber, fuel wood, fodder, and a range of Non-Timber Forest Products (NTFPs) such as fruits, nuts, edible fungi, vegetables, fish, animals and medicinal plants, resins, essences, and a range of barks and fibers such as bamboo, rattans, palms and grasses. Over-exploitation of useful plants, lack of knowledge and awareness about the plants’ present population status, habitat alteration and specificity, narrow range of distribution, over-grazing are some of the severe threats endangering the existing populations of important plants. Additionally, natural enemies such as pathogens, herbivores and seed predators could substantially limit the abundance of rare plant species in any given area. Collection of plant materials, especially of rare and endangered plant species from natural habitats for various experimental purposes by researchers, also poses a threat on their natural population in the wild. Realizing the continuous depletion of these valuable resources, attempts should be made for its large-scale cultivation and multiplication in order to meet its escalating demand as well as long-term sustainability. There is an urgent need to carry out detailed investigations on the geographical distribution patterns, habitat utilization patterns, feeding ecology, and impact of herbivores on important plant populations.

Forest Resources of Jharkhand, Eastern India: Socio-economic and Bio-ecological Perspectives

Design considerations related to feedforward interference cancellation in a narrow-band receiver are discussed A design is presented that distributes the noise and linearity requirements across two parallel receiver branches Simulation results from a 1GHz front-end designed in a UMC-013?m CMOS process are presented

Feedforward Interference Cancellation in Narrow-Band Receivers

In an increasingly noisy society, methods of reducing noise are becoming more important. This work proposes an analog electroacoustic circuit for active control of narrow-band low-frequency acoustic noise using adaptive filtering techniques. The circuit aims at producing antinoise, which is acoustically added to the disturbing noise to produce an error signal that is fed back to the circuit. The proposed circuit is a modified Kerwin-Huelsman-Newcomb biquad filter that tunes itself to the incoming noise frequency using the zero tuning techniques. The circuit was implemented on a printed circuit board and it was successful in reducing noise by 15-20 dB in open space. Active noise control specifically for narrow-band noise cancellation using adaptive analog filters seems to be a better solution than its digital signal processing counterpart in speed, cost, and robustness.

Active cancellation of acoustic noise using a self-tuned filter

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Active cancellation of acoustic noise using a self-tuned filter