M. T. de Melo

Discriminators for Instantaneous Frequency Measurement Subsystem Based on Open-Loop Resonators

The authors have studied a new way to design an instantaneous frequency measurement subsystem (IFMS). The method is based on bandstop filters. The device uses rectangular open-loop resonators instead of delay lines. The resonance frequency is adjusted by a resonator perimeter that must be approximately a half-wavelength long, and also by coupling distance between the resonators and the main transmission line. Simulated and experimental results are presented for a 5-bit IFMS.

Using genetic algorithms for device modeling

In this paper, genetic algorithms are used to find the optimal values for the lumped elements of a given discrete model such that its response best match the modeled devices response. A novel objective function is used by the algorithm which is suited for matching responses with pairs of conjugate poles or zeroes. By applying the method for different values of the devices parameters, the relationship between the models and the devices parameters can be found. An application of the method to a bandpass filter shows that it can give quite precise results.

Comparison between power line communication multipath model and coaxial cable interferometer theory

SUMMARY The authors have studied a new method to find parameters of broadband power line communication channel model. Lossless power line communication channel model is compared with classical interferometers approach to develop this model. The authors also used coaxial cables to simulate a multipath channel, because it can behave like a lossless power line communication channel. Thus, measurements were carried out with a network analyzer to find S parameters. The modeling parameters, for the multipath model were found after using MATLAB software and classical interferometers approach. Then, theoretical and experimental results are presented and compared. Copyright

Coplanar Antenna Array for 2.45GHz RFID Tag

A new CPS Antenna design is presented. This antenna is suitable for RFID Tags, operating at 2.45GHz. The device was fabricated on RT6002 substrate of thickness h=1.5 mm. Input impedance control is based on the conformal mapping technique. A full wave EM simulator was used to obtain the frequency response. Simulated and experimental results are presented.

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 Novel LSB Discriminator for a 5 bit IFM Subsystem Based on Microstrip Band-Stop Filter

The authors have studied a new way to design IFM (Instantaneous Frequency Measurement) subsystem. The method is based on band-stop filters. The IFM uses rectangular open loop resonators instead of delay lines. The resonance frequency is adjusted by resonator perimeter, that must be half guided wavelength, and also by coupling distance between the resonators and the main transmission line. A LSB (least significant bit) discriminator of an IFM subsystem with resolution of 62.5 MHz is designed. The device has been fabricated on RT6010.2 substrate of thickness h=1.27 mm. A full wave EM simulator is used to obtain the frequency response.

Microstrip diplexer for GSM and UMTS integration using ended stub resonators

A novel microstrip diplexer design for UMTS and GSM ranges is presented. This device was implemented by using microstrip resonator with serial coupling. The modified gap structure allows to adjust the operating frequency of the filters and reduces the dimensions of the device as it will be presented. Simulation results of the diplexer are presented. Device has been simulated on Duroid RT6010 substrate of thickness 0.61 mm. A new diplexer can be used for sharing radiating system of both UMTS and GSM platforms.

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.