Complete Parameter Identification of Large Induction Machines From No-Load Acceleration–Deceleration Tests

This paper introduces an offline deterministic method for identification of inertia moment, mechanical losses, and electrical parameters for large induction machines, based on direct-on-line starting and natural slowdown tests, performed under no-load conditions. The static characteristic of absorbed power is used for the validation of results. Complete experimental results for a 6-kV four-pole 7500-kW machine are presented. The method brings significant cost savings for testing large induction machines.     

Frequency independent microstrip stacked antenna

The advancement of technological development in the microstrip antenna and its applications in diverse areas, have given rise to the need for a frequency agile and frequency independent microstrip antenna which could be used for the same range of frequencies without altering the system. Requirements of such nature could be met by log periodic antenna. However, in the present endeavour a frequency independent microstrip stacked antenna consisting of nine elements operating in the S-band (2.000–4.000GHz) has been proposed. The developed antenna has been experimentally tested over an achievable band of frequencies from 3.200 to 3.920GHz. The antenna performance has characteristics like E-plane radiation patterns. The 3dB beamwidth, radiated power and VSWR show very similar behaviour for the different frequencies of operation obtainable in the S-band. The coaxial-fed microstrip stacked antenna provides an operational bandwidth of approximately 23%, i.e. 3.200GHz to 3.920GHz. The VSWR for the entire operational band is around 2 whereas the gain for the antenna is found to vary from 4.00 to 8.36dB. The 3dB beamwidth has been found to fluctuate between 16.8° and 23.5°. The designed antenna can be well suited for the practical broadband applications.     

Analysis of Multilayer Rectangular Patch Antenna for Broadband Operation

In this paper analysis of multilayer patch antenna has been carriedout. The antenna shows the broad bandwidth when a patch is stacked over fed patch in gap coupled structure. Typically a 42.65% bandwidth is achieved in three layer antenna. Further the bandwidth of the antenna depends inversely on the gap(s). The gain of the antenna is found to be 6.08 dB with 3 dB beam width of 92°. The theoretical results are compared with IE3D simulation and reported experimental data.     

Analysis of electromagnetically coupled two-layer elliptical microstrip stacked antennas

Theoretical analysis of a coaxially fed, electromagnetically coupled two-layer elliptical microstrip stacked antenna based on circuit theory is presented in which mutual coupling is considered. Consequently, various parameters such as input impedance, VSWR, return loss, bandwidth etc. are investigated as a function of frequency, which shows resonance at 3.0GHz. It is also observed that there exists a critical value of frequency (3.0GHz) below which capacitive coupling is dominant and above which inductive coupling is dominant. The electromagnetic coupling enhances the radiated power which depends directly on the permittivity of the substrate, in spite of the fact that radiated power generally decreases with increasing permittivity of the substrate.     

Analysis of gap-coupled microstrip antenna

In the present paper the analysis of a gap-coupled microstrip antenna (GCMSA) is carried out using the circuit concept and consequently various parameters such as input impedance, VSWR and return-loss are investigated for different air gap lengths. It is observed that the resonant frequency of the antenna with different substrates depends on the gap length. The gap-coupled antenna behaves as an RL network below the resonant frequency for all substrate materials and gap lengths, whereas the antenna behaviour above resonance is like an RC network. It is further observed that the resonant frequency of the GCMSA decreases with increasing gap length.     

Noise considerations for a tunnel diode integrated rectangular patch antenna

The tunnel diode integrated rectangular patch antenna is investigated, with emphasis mainly on noise considerations. Noise power is calculated and is found to increase very slightly with frequency for both GaAs and Ge tunnel diode loaded patches. Noise figure and noise temperature also increase with frequency for GaAs and Ge tunnel diode loaded patches. Loading the patch with the tunnel diode increases the effective noise figure and effective noise temperature of the patch, degrading the performance of the communication system significantly.     

Gap-coupled microstrip array antenna for wide-band operation

The theoretical and experimental investigations carried out on a gap-coupled microstrip array antenna reveal that there is a significant improvement in VSWR and bandwidth characteristics of the gap-coupled microstrip array antenna as compared with a conventional microstrip array antenna. The input impedance and the resonant frequency of the gap-coupled patch are found to depend heavily on the gap length as well as on the dielectric constant of the substrate material.     

L-strip Feed Circular Disk Dual Resonator Patches Antenna for Wireless Communication

A dual frequency resonance antenna achieved by introducing L-strip feed in circular disk patch is analysed by using circuit theory concept. The resonance frequency is found to be 5.19 and 10.44 GHz for lower and upper resonance frequency respectively and the bandwidth of the proposed antenna for lower and upper resonance frequency is found to be 11.54 and 13.12 %. When the notch is cut on the circular disk patch dual resonance frequency is shifted higher side and the resonance frequency is found to be 5.84 and 10.54 GHz. It is found that the resonance frequency is observed 1.860 and 1.824 respectively. It is easy to adjust the higher and lower band by changing the dimensions of L-strip. It is found that the resonance frequency also depends on the notch dimensions. The theoretical results are compared with IE3D simulation results which are in close agreement.     

Tunnel diode integrated rectangular patch antenna for millimetre range

Theoretical investigations conducted for the Ge tunnel diode integrated rectangular patch antenna reveals that such an antenna exhibits frequency tunability with bias voltage. The Ge tunnel diode loaded patch can be operated in the millimetre range (53.517–56.4615GHz). The range of frequency obtainable for operation is 2944.5MHz. The radiation pattern shows variation with the bias voltage, and radiated power beamwidth and directivity vary inversely with bias voltage. Thus, the Ge tunnel diode loaded patch can be used to achieve electronic tuning (BW = 5.355%) with the bias voltage.