Stochastisation of microwave oscillations in microstrip log-periodic antenna-generator with LF noise-like modulation.

Microwave solid-state oscillators of noise-like signals are of the great interest for wireless telecommunication systems, imaging systems and electronic warfare. In the paper, the possibility of power combining in the array of three independent noise-like oscillators is investigated. The noise-like oscillators are based on the microstrip log-periodic antennas which are integrated with field-effect transistors. As an active element, NE350184С field-effect transistor with 13.5 dB gain at 12 GHz is chosen. It was previously shown that single-frequency, multifrequency or noise-like generations are possible in the active antennas. The main factors that affect the generation type are the current in the drain-source circuit of the transistor and the distance between the antenna plane and reflecting screen. It is experimentally shown, that using of the noise-like oscillator arrays makes possible the spectrum and power combining, but the construction is not enough stable and reliable.

Subordinate Oscillator Arrays: Physical Design and Effects of Error

Prior work demonstrates that an attached subordinate oscillator array (SOA) can attenuate vibration of a host structure over a frequency range of interest. A judicious choice of the distribution of masses and stiffnesses of the attached oscillators can result in a relatively flat frequency response of for the host structure over a desired band. This response modification can be a significant improvement over classical dynamic vibration absorbers (DVA) that attenuate a structure's response at one target frequency while increasing the frequency response amplitude at nearby side frequencies. Performance of the SOA can be highly sensitive to the uncertainty or disorder in the mechanical properties of the system. This paper introduces a novel design strategy that can make use of either 3D-printing or piezoelectric SOAs (PSOAs). These strategies have the potential to address and ameliorate such sensitivity to error. It is important to note that the design strategy is simple and effective in that it can be carried out without computational optimization techniques by choosing simple or well-known distributions of properties.

Expanding the Teaching of Single Frequency Vibration Absorption to Broadband Attenuation using Subordinate Oscillator Arrays via Fettuccine Pasta

Dynamic vibration absorbers (DVAs) and tuned mass-dampers (TVAs) have wide-spread applications in the aerospace industry, the automotive sector, and in civil engineering structures. There are numerous designs of active and passive vibration attenuators or absorbers that isolate structural vibrations at or around the desired frequency. All these design approaches are fundamentally different ways to modify and tune the placement of the resonant frequencies of the host structure. The current work presents a novel method to passively attenuate vibration over a broad frequency bandwidth in the presence of uncertainty. An array of linear oscillators, also referred to as subordinate oscillator arrays (SOAs), are attached to a two-degrees-of-freedom structure to produce an attenuated broadband frequency response around a target frequency. SOAs can also be interpreted as an array of DVAs and in some categories, they can be considered as an approach to meta-structures. Another objective of the current work is to develop a hands-on approach to extend classroom teaching of vibration-isolation using SOAs made out of fettuccine strands and modeling clay. The frequencies of the oscillators in the array are tuned by varying the length of each strand and the mass of the modeling clay attached to its tip. Uncertainty in dynamic properties of such oscillators often results in mistuned SOAs with non-uniform frequency response function. Therefore, designing and testing fettuccine-based SOAs allows students to handle cases when structural uncertainties arise in engineering systems. Additionally, some of the work in the field of meta-structures can be modeled and represented by SOAs and this will provide a straight forward way to teach students some of these contemporary concepts.