B. G. M. de Oliveira

Compact coplanar interferometer for a 5–6 GHz IFM system

The authors present a new compact coplanar interferometer for application in an IFM system with 4 bits that operates in a frequency band from 5 to 6 GHz. This interferometer consists of a couple of coplanar two-way Wilkinson power dividers connected to two CPS lines with different signal delays. This interferometer presents smaller dimensions when compared to other designs. Details of this compact coplanar interferometer are provided along with a comparison between theoretical, simulated and measured results.

A smart antenna system for remote supervision

This paper presents a switched smart antenna system, designed to provide a reliable communication between a Center for Integrated Operation of a distributor of electric power and automation devices such as electrical switches remotely controlled. The smart antenna system is controlled by an electronic device which sets de direction of the main lobe of an antenna array to the automation device. Network of power distribution automation devices are used as switches, remotely controlled and su- pervised by a Center for Integrated Operation (COI, from Portuguese Centro de Operacao Integrado). The communication between the COI and the automation devices can be performed by various forms of media such as dial-up, cellular, satellite and radio link in the UHF band. In the case of UHF radio link, the system consists of a base station that communicates with all devices in the area, focuses the information and sends it to the COI. The base station is usually located at a substation of the electricity Distribution Company, and devices on poles. At the base station, an antenna array of collinear dipoles is used which produces an omnidirectional radiation pattern with gain of about 6 dBi. The distance,terrain, vegetation and buildings in the path between the devices and the base can disrupt radio communication, leaving these devices in shadow regions. An increase in signal intensity would be sufficient to overcome various obstacles and reestablish communication path, eliminating the shadow regions. This could be achieved by the omnidirectional dipole array, but at the expenses of a great number of dipoles which in the end would be unpractical. This paper describes a smart antenna switched system installed at the base station that focuses the main lobe towards the automation device with a higher gain than the one of the original system. This would reestablish communication and also would be able to spread the communi- cation with more devices to be installed for further expansion. As far as the authors are concerned, no similar application of a smart antenna array has been reported yet.

Interferometer Instantaneous Frequency Identifier

The rapid development of radar, communication and weapons guidance systems generates an urgent need for microwave receivers to detect possible threats at the earliest stage of a military mission. The microwave receivers used to intercept the RF signals must be able to meet these challenges. Thus, microwave receivers have become an important research area because of their applications to electronic warfare (EW) [1].

Microstrip power divider for integration of an Instantaneous Frequency Measurement system

A 3-dB microstrip power divider was designed and fabricated to integrate two multi-band-stop filters for Instantaneous Frequency Measurement (IFM) system application. A 2-bits IFM system was set up with the divider. Experimental results are also presented.

Instantaneous Frequency Measurement Subsystem implementation using low-cost microcontroller

This paper presents a practical implementation of a S-Band 4-bit Digital Instantaneous Frequency Measurement Subsystem based on microstrip multibandstop filters. The outputs are converted using RF detectors and digitized using an Arduino® board. Filter design is based on open-loop resonators. Sub-band is determined by calculating the average value of m measures and standard deviation is used to further improve reliability. This paper discusses the key requirements for this design and presents experimental results for the sub-band determination.

A comparison between 4-bit fixed and reconfigurable microwave discriminators for frequency identification

This paper presents a comparison between fixed and reconfigurable 4-bit microwave discriminators. The fixed discriminator is implemented by using multi-band-stop filters to define bits used for frequency identification. The reconfigurable discriminator is implemented by using delay lines and two SPQT switches. Both designs operate at L and S bands, a comparison between both devices is provided, including simulated and measured responses for both designs.

New compact interferometer based on fractal concept

The authors present a novel compact 3-bit interferometer based on Hilbert fractal geometry for application to Instantaneous Frequency Measurement (IFM) system operating in the range 4.66-6.38 GHz. The interferometers use two-way Wilkinson power dividers connected to two microstrip line with different signal delays, where one of these microstrip lines is based on Hilbert fractal curve. A full wave EM simulator is used to obtain the frequency response. Simulated responses are presented and compared to theoretical results.

Reconfigurable frequency identification receivers

This paper presents a building block approach for the design of frequency identification receivers. The devices are based on a Reconfigurable Discriminator (RD) for frequency measurement, operating from 1 to 4 GHz. The RD is a two-port device used to identify the frequency of an unknown signal. The devices use RF switches, which are implemented with PIN diodes to select different bits used for frequency identification.

Switched smart antenna system for SCADA telesupervision and telecontrol systems

This paper presents the conception and simulation results of a switched smart antenna array to be used for a reliable communication between a Distributor of Electricity and its automation devices such as remotely supervised and controlled electrical switches. The smart antenna system controls the direction of the radiation main lobe, increasing the transmitted power density, which allows the establishment of communication with devices located in shadow regions. This prevents new repeater stations to be installed for the same purpose. Also laboratory tests with Beamforming Controller Circuit are here reported.

Coplanar power splitter analysis for the miniaturization of instantaneous frequency measurement subsystems

Based on design equations taken from the conformal mapping theory, the authors have investigated the frequency response of a miniaturized coplanar power splitter for instantaneous frequency measurement subsystems application. Devices in different scales are fabricated and measured. The results of insertion loss through both arms of each structure are presented and compared. The devices were made on both RT/duroid 6010 and glass fibber by the silk screen technique.