A 26 GHz retro-reflective array for long-range RFID applications
A unique design of series-fed grounded coplanar waveguide (GCPW) patch arrays for use in retro-reflective arrays is presented. For the current application, a planar retro-reflector which is capable of providing large radar cross-section (RCS) and signal modulation, and can also operate on metallic surfaces from 25.5–26.5GHz is desired. Linear, series-fed GCPW patch arrays are employed as the radiating elements. Using constituent arrays allows maximization of RCS using the minimum number of active components. Additionally, the unique orientation of the series-fed arrays provides beam squinting, allowing for ease of target identification and distinguishing the response from that of the array ground plane. The array design and results are briefly presented herein. Integration of the array in the intended system application is discussed in a separate conference submission.
Closed-Loop Feed Architectures for RCS Beam Broadening of Retro-Reflective Arrays
This communication presents a novel architecture for a one-dimensional, large radar cross section (RCS) retro-reflective array. This array is tailored to aide in the standoff detection and localization of large metallic objects in a warehouse setting. This application scenario requires this retro-reflective array to be planar, provide a high RCS, and a wide beam in the elevation plane. Traditional methods to increase the RCS of planar arrays employ an increase in the number of array elements which typically results in a narrowing of the beam in this plane. The approach presented eliminates this problem. To maintain a wider beam in elevation, a unique series fed grounded coplanar waveguide (GCPW) patch element is designed to radiate off boresight at a specified degree. This linear array is fed from both terminal ends of the array through a unique `closed-loop' interconnection scheme. In this arrangement, a resonant structure is created through circular loops that are formed by the interconnection of the linear series arrays and associated feed lines. The result is a broadened beam in elevation when compared to that of traditional Van Atta interconnection schemes while maintaining the broad RCS expected of a retro-reflective array in the horizontal plane. This compact array has a large RCS and is implemented at 26 GHz. The design of the array elements themselves is discussed along with the development of this novel feed architecture. RCS pattern measurements from the fabricated arrays are presented and performance enhancements quantified when compared to traditional retro-reflector feed geometries.
Parboiled rice effluent: A wastewater niche for microalgae and cyanobacteria with growth coupled to comprehensive remediation and phosphorus biofertilization
Abstract The potential of microalgae and cyanobacteria for bioremediation of wastewater by nutrient uptake combined with simultaneous biomass production is a well recognized perception of today's world. The present study illustrates the treatment of a highly polluted wastewater generated during parboiling of paddy in rice mill industries, widely operational in developing countries where rice is the staple food crop, with the help of microalgal and cyanobacterial isolates capable of growing at high rates in parboiled rice mill effluent (RME). This endeavor leads to comprehensive bioremediation of the said effluent and subsequent use of the harvested biomass as slow release phosphorus biofertilizers and the treated effluent for crop irrigation. The RME-acclimatized algal consortium demonstrated highest growth in terms of fresh weight and greatest remediation efficiency at the end of 36 days' treatment of RME, with 93.9% phosphorus and 100% ammonia-nitrogen removal, 98.7%, 91.6% and 93.5% reduction in biological oxygen demand, chemical oxygen demand and total dissolved solid, respectively, and an increment of 186 ± 0.3 mg L − 1 dissolved oxygen, bringing down the pollutants level well below the discharge limits suggested by Central Pollution Control Board, India. Additionally, microalgae in the consortium aggregated in clumps spontaneously in presence of the filaments of Phormidium sp. facilitating easy harvest. The RME-acclimatized algal consortium demonstrated highest accumulation of polyphosphate (poly-P) (0.76 ± 0.01% of dry weight) as well as highest release of phosphorus in non-sterile soil emphasizing the essential role of soil phosphorus solubilizing organisms to leach soluble phosphorus from the insoluble poly-P present in the biomass. The rice seedlings watered with treated RME also showed improved growth effect on shoot height and leaf width. The study results establish the suitability of RME as an excellent growth media for microalgae and cyanobacteria.