Photos Vryonides

Triple notch UWB antenna controlled by three types of resonators

This paper discusses a microstrip fed UWB monopole antenna with a triple notch characteristic. The three notches are designed to occur at the WiMAX frequency range, the WLAN and at a third frequency in the higher end of the UWB range. Each of the three notches is controlled by a different type of resonators and each and every notch can be adjusted without affecting the position or the shape of the remaining two, thus allowing for an antenna design with adjustable, agile S11 response.

UWB antenna with a WiMAX frequency notch caused by a novel stepped U shaped slot that suppresses the parasitic notches

UWB antennas with embedded stubs or slots can create a notch in the frequency range. The frequency notch and therefore the reduced radiation intensity is confined to frequencies used by other applications in order to achieve reduced interference. However the use of such resonant elements causes additional notches at the fre quencies which equal to even or odd multiples of the design frequency. While the lowest odd multiple of the WLAN frequency (5.2–5.8 GHz) lays outside the UWB range (3.1–10.6 GHz) this is not the case for the WiMAX frequency. In this paper, a stepped slot is introduced in a UWB elliptical monopole that suppresses the unwanted higher order notch, and with the use of a linearly tapered feed line return loss better than −10dB is achieved throughout the UWB range with the exception of the WiMAX range.

Reconfigurable dual-mode band-pass filter with switchable bandwidth using PIN diodes

A reconfigurable band-pass filter with switchable bandwidth, for wireless applications is demonstrated using a dual-mode microstrip square-loop resonator. The proposed filter has been designed on Rogers RO4003C and achieves switchable bandwidth by changing the length of two tuning stubs with the implementation of two strategically placed p-i-n diodes as switching elements. The filter was designed with a center frequency of 2.4 GHz and the two distinct operation states have bandwidths, 113 MHz (4.8%) with an insertion loss of 1.2 dB and 35 MHz (1.5%) with an insertion loss of 1.5 dB. The physical size of the fabricated reconfigurable filter including the implementation of the DC bias lines is comparable to the size of a conventional filter.

On the Use of Tunable Power Splitter for Simultaneous Wireless Information and Power Transfer Receivers

The use of a tunable power splitter (PS) as a constituent component of a simultaneous wireless information and power transfer (SWIPT) system is discussed. Two varactor diodes are used to achieve a tunable output power ratio 2 :  3 varying from 1 : 1 to 1 : 10 under good matching conditions. The SWIPT system that operates at 2.4 GHz consists of a typical patch antenna, cascaded with the tunable PS, and a voltage doubler rectifier. The constituent components were implemented and tested as stand-alone devices and were subsequently combined in a measurement system using interconnectors. The effect of the tunable PS was explored with respect to the SNR measurements on the port that is intended for the information decoding receiver and the DC voltage measurements on the termination load of the rectifier that is connected directly on the energy harvesting port of the tunable PS. A spectrum analyzer is used for the SNR measurements while the input power is controlled using a signal generator. Both wireless power transmission and on-board measurements verify that the harvested energy can be maximized by using the minimum SNR at the information decoding branch at the expense of DC power consumption required for the biasing of the varactor diodes.

A square ring resonator bandpass filter with asymmetrically loaded open circuited stubs

This work presents the design, fabrication, and measurements of a compact, low loss, bandpass filter, using two asymmetrically loaded open circuited stubs on a microstrip square ring resonator. In the proposed design, a bandpass filter is developed from the stop band characteristics of the ring resonator. The operating frequency of the filter is at 2.4 GHz. The filter has a bandwidth of 1.4 GHz, resulting in a 60% -3 dB fractional bandwidth. The insertion loss is less than 1 dB and the return loss is below -20 dB in the desired passband. A prototype is fabricated to validate the proposed design using Rogers 4003C substrate and an equivalent circuit model with almost identical S-parameters response, is also introduced. The measured results agree well with the simulated results and the equivalent circuit models response. In order to further improve the band rejection zone, parallel-coupled lines are introduced in replacement of the conventional microstrip lines of the input and output feed lines of the ring resonator. The use of coupled lines improves the band rejection zone of the filter especially for frequencies away from the transmission zeros, and results in insertion loss better than -20 dB.

Humidity sensor devices using PEDOT:PSS

This paper discusses the use of PEDOT:PSS material for the implementation of two types of humidity sensor devices. The first device is a wireless humidity sensor that consists of a microstrip-fed rectangular slot antenna, loaded with one or two PEDOT:PSS blocks. The second device consists of a two port, filter, that consists of a split ring of rectangular shape, that is also loaded with a PEDOT:PSS block. PEDOT:PSS block was characterized with equivalent RC network, for three different humidity percentages, 40%, 70% and 100%. The three different RC value sets cause resonance frequency shifts in the response of the s parameter plots. The wireless sensor changes its radiating resonance and it can therefore be read by a distant interrogator, and the filter sensor presents a band pass zone shift that can be sensed with the integrated decision making system. Both sensor devices present high sensitivity, meaning that significant frequency shift and thus sensing ability is demonstrated even for small humidity variations response of the sensor devices.

Comparison of GPS-derived vTEC over Cyprus with IRI-2007

This paper presents a comparison of ionospheric vertical total electron content (vTEC) values evaluated from Nicosia (35.1 N, 33.4 E) ground-based GPS station in Cyprus and the corresponding predictions with the latest version of the IRI model (IRI-2007) during periods of low (2008), and high (2001) solar activity for different seasons.

Spread F observations during low solar activity over Cyprus

The temporal variations of the low-latitude spread-F (SF) observed by DPS-4D digisonde at Nicosia during low solar activity from January 2009 to December 2010 are studied. The spread F measured by the digisonde were classified into two types, i.e., mixed SF (MSF) and range SF (RSF). The statistical results show that the MSF and RSF are outstanding irregularities in Cyprus which occur in all three seasons (equinox, summer, winter). Both types have a diurnal peak before midnight and usually appear during 20:00–06:00 UT.

24 GHz low phase noise HBT dielectric resonator oscillator

This paper describes the design and performance of a novel, planar 24 GHz low phase noise GaAs HBT dielectric resonator oscillator (DRO) for millimeter wave short range radar sensors for automotive and industrial applications. The detailed design, circuit development and experimental results for the DRO are presented and discussed. The measurement of the oscillator showed a center frequency of 23.82 GHz with a fundamental output power of 3.33 dBm and a phase noise performance of −125.67 dBc/Hz at 100 KHz offset, the lowest yet reported.

Development of an ultra compact dual band antenna on a one cubic centimeter (1 cm 3 ) surface

This paper discusses the development of a dual, broadband antenna, designed to be used for a compact sensor with total size no more than one cubic centimeter (1 cm3). The antenna specifications require more than 100 MHz bandwidth at 2.4 GHz and more than 1 GHz bandwidth at frequencies higher than 6 GHz. The 2.4 GHz radiation is used for the downlink, control data reception, and the wideband radiation is used to support the high data rate transmission to the sensor reader (uplink). A novel folded dual monopole antenna is presented that meets the sensor requirements. It is printed on two faces of a one cubic centimeter box. On one side a “fat” monopole is implemented successfully for the wideband operation and on an adjacent side a folded monopole operates effectively at 2.4 GHz. Both monopoles use the same, common feed line. The sensor IC is embedded inside the 1 cm3 cube.