A generalized spectral Green's function formulation of N-layer substrate structure is given with ... more A generalized spectral Green's function formulation of N-layer substrate structure is given with three dimension sources, which is a set of closed form formulas. A full-wave analysis model for rectangular microstrip antennas covered with N-dielectric layers has been established by using the above spectral Green's function. The unknown surface current density on the nficrostrip patch for such structure is found as a solution of an integral equation. The input VSWR and radiation patterns of the antenna are also obtained. The numerical results have been verified by the experimental results" Key words Microstrip antenna; N-layer dielectric cover; Full-wave analysis; Spectral Green's function *Partly supported by the Research Item B96(56) of the Ministry of Railways of China
2019 European Microwave Conference in Central Europe (EuMCE), 2019
Characteristics of textile antennas integrated in clothing are affected by moisture from e.g. rai... more Characteristics of textile antennas integrated in clothing are affected by moisture from e.g. rain or perspiration. A wideband planar monopole was adapted for implementation as full textile antenna. The monopole was manufactured by embroidering. The influence of moisture on wideband textile monopole antenna has been investigated by observing the input reflection coefficient, gain and radiation patterns. It was demonstrated that wideband textile antennas are more resilient to moisture in comparison to the resonant ones.
section with the first slot. The purpose of this antenna was to emphasise the effect of an added ... more section with the first slot. The purpose of this antenna was to emphasise the effect of an added short circuited slot on the CP performance, i.e. to control the effectiveness of the final switchable antenna including two slots and pin diodes (Fig. 2). The short circuits were made with 0. I nun-wide strips, which model ideal forward biased pin diodes (ON state), located at 3nun from the slot intersection. Provided that the lengths of the antenna and the slot were tuned (Lp = 16.9mm, LY = 15.4mm), a 4% CP bandwidth was kept with good return loss perfonnances. Nevertheless, the addition of a second slot yields a 30OMHz drop in the central C P frequency.
The surface was mounted above a vertically oriented hom antenna at 45", so that the reflected rad... more The surface was mounted above a vertically oriented hom antenna at 45", so that the reflected radiation was directed into the horizontal plane. The surface and ham were rotated together, and the radiation pattcm was measured with a stationary rccciving horn. The patterns for three different phase gradients are shown in Fig. 3, corresponding to beam positions of O", 20°, and 40'. Steering to the opposite direction is produced with the opposite phase gradients. Thc frequency of the plats is 4.2 GHz. and the measured bandwidth is about-5%. The surface produces approximately the expected beamwidth, patterns, and sidelobe characteristics for a 3.3 wavelength reflector. However, the partems show some dependence on frequency and steering angle, which is likely due to the phase curvarure of the ham antenna, and could be removed by adding a compensating C U N B~K C to the reflection phase function.
pred Vama je broj 1/2012 časopisa AUTOMATIKA koji sadrži devet odabranih radova s 20. Internation... more pred Vama je broj 1/2012 časopisa AUTOMATIKA koji sadrži devet odabranih radova s 20. International Conference on Applied Electromagnetics and Communications (ICECom), koja je održana u Dubrovniku od 20. 23. rujna 2010. godine. Radovi su u zbornicima skupova ograničene duljine te je stoga nekoliko autora pozvano da dostave proširene verzije radova. Petnaest je godina prošlo od prve konferencije ICECom koja je bila organizirana pod današnjim imenom, a koja nastavlja tradiciju susreta koji su organizirani od ranih 1970tih godina. Teme pokrivene konferencijom ICECom stalno se nadopunjuju kako bi se moglo prikazati stanje istraživanja u području modeliranja i konstrukcije antena, računalnih metoda u elektromagnetizmu, pokretnih i osobnih komunikacija, radarskih sustava i daljinskih istraživanja, radio navigacijskih sustava i sustava za pozicioniranje, rasprostiranja elektromagnetskih valova, RFID, elektromagnetske kompatibilnosti, elektromagnetskih mjerenja, THz-nih tehnologija, metamaterijala, itd. Prva skupina radova u ovom posebnom izdanju vezana je uz antene. Prof. Jiro Hirokawa održao je plenarno izlaganje te je u radu Antenski nizovi valovodnih otvor-antena i konverteri polarizacije izvedeni s pomoću planarnih laminata dao pregled istraživačkih aktivnosti svoje istraživačke grupe u izgradnji valovodnih antena u milimetarskome valnom području. To je danas važno pitanje jer su uvedene ili se planiraju uvesti mnoge primjene u milimetarskome valnom području. Glavni problem u izgradnji antena u tom frekvencijskom području čine gubitci i složenost izrade antena, tako da predložena tehnologija zasnovana na planarnim laminatima nudi mnoštvo prednosti. U radu Male antene: tehnike minijaturizacije i primjene, Davor Bonefačić i sur. daje izvrstan pregled tehnika koje se mogu koristiti za izgradnju malih antena antena čija je veličina ograničena veličinom ured̄aja u kojem će se antena koristiti (kao što je to slučaj s mobilnim telefonima). Sve su tehnike eksperimentalno potvrd̄ene te je u članku dana usporedba karakteristika svih predloženih rješenja. Treći članak Usporedba zrcalnog modela i modela prijenosnih linija u analizi horizontalne žičane antene iznad dvoslojnog tla, Vesna Arnautovski-Toševa i sur. razmatraju mogućnost uporabe pojednostavljenih modela za analizu žičanih antena koje se nalaze iznad višeslojnih struktura, tj. iznad realnog modela tla . Rigorozne su metode analize vremenski zahtjevne, tako da autorica istražuje točnost dvaju pojednostavljenih pristupa: zrcalnog modela i modela prijenosnih linija. Nove elektromagnetske strukture, na temelju metamaterijala s aktivnim komponentama, opisane su u radu Analiza stabilnosti u superluminlanim prijenosnim linijama zasnovanim na metamaterijalima s realnim ne-Fosterovim negativnim kondenzatorima, Silvio Hrabar i sur. U radu se daje detaljna analiza osnovnog bloka prijenosne linije izvedene uz pomoć metamaterijala – tzv. aktivni spremnik koji sadrži i konvencionalni kondenzator i ne-Fosterov negativni kondenzator. Radovi Dijagnostika antena s pomoću bezfazne NF informacije, Yuri Álvarez i sur., i Dijagram zračenja vertikalnog dipola iznad mora i pripadajući mjerni postav, Antonio Šarolić i sur., razmatraju probleme elektromagnetskih mjerenja. Za otkrivanje anomalija u promatranoj anteni najbolje je precizno izmjeriti razdiobu bliskog polja (i amplitude i faze) antene. No, to je iznimno složena zadaća, poglavito jer faza brzo varira u bliskom polju. Stoga je od velike važnosti pojednostaviti mjerenja u bliskom polju, odnosno važno je razviti mjerne postupke kod kojih bi bilo moguće izvući dovoljno informacija iz mjerenja samo raspodjele amplitude. U radu se opisuje proširenje tzv. metode rekonstrukcije izvora (SRM) za dijagnostiku antena primjenom bezfaznih mjerenja. Drugi rad vezan uz elektromagnetska mjerenja opisuje kompakOnline ISSN 1848-3380, Print ISSN 0005-1144 ATKAFF 53(1), 5–8(2012)
The paper presents the propagation analysis of ultrawideband Gaussian signal in an automated coll... more The paper presents the propagation analysis of ultrawideband Gaussian signal in an automated collaborative warehouse environment where human and robots communicate to ensure that mutual collisions do not occur. The warehouse racks are principally modeled as clusters of metallic (PEC) parallelepipeds, with dimensions chosen to approximate the realistic warehouse. The signal propagation is analyzed using a ray tracing software, with the goal to calculate the path loss profile for different representative scenarios and antenna polarizations. The influence of the rack surface roughness onto propagation is also analyzed. The guidelines for optimum antenna positions on humans and robots for safe communication are proposed according to the simulations results.
This paper presents an approach to simultaneous beamwidth and beam-steering control using an arra... more This paper presents an approach to simultaneous beamwidth and beam-steering control using an array-fed reconfigurable partially reflective surface (PRS) antenna. Requirements and trade-offs regarding the design of such antennas are discussed. The antenna operation is confirmed by full-wave simulations.
Propagation of UWB Gaussian signal in a model of automated collaborative warehouse is analyzed us... more Propagation of UWB Gaussian signal in a model of automated collaborative warehouse is analyzed using ray tracing method. The transmitting antenna is placed on the human body while the received power profiles in warehouse containing empty racks and racks filled with different loads are calculated. This gives rise to estimation of safe communication range between humans and robots.
Use and application of the GTEM-cell, which is a transmission structure based on a TEM-cell appro... more Use and application of the GTEM-cell, which is a transmission structure based on a TEM-cell approach, are described. The cell can be used for calibrating small antennas, for immunity and emission testing, and for biomedical experiments. It provides homogenous electromagnetic fields with TEM (transversal electromagnetic mode) distribution, similar to the free space. It has a shield to prevent radiation from the outside, which would interfere with our measurement. Plant Lemna minor has been exposed to the electric field similar to those of the cellular phones and the effect on the growth has been studied. The experiments included exposure to the frequencies of 400 MHz and 900 MHz with strength of electric field being 22 V/m. The time of exposure was 2 and 4 hours. The influence of AM (80%) 1 kHz sine modulation was also tested. Our investigations confirmed that electromagnetic field of frequencies produced by mobile phones or base stations can affect plant growth.
2021 Fifteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), Sep 20, 2021
This paper proposes non-Foster tank circuit that comprises both positive and negative R, L, C ele... more This paper proposes non-Foster tank circuit that comprises both positive and negative R, L, C elements. It is shown that, apart from familiar effect of broadband dispersion cancellation, it is also possible to achieve amplification and self-oscillations rooted in negative reactive elements.
In this work, the concept of ultrawideband antenna comprised of two triangular monopoles is intro... more In this work, the concept of ultrawideband antenna comprised of two triangular monopoles is introduced. The design procedure is accompained by simulation and measurement results.
Recent introduction of artificial materials with simultaneously negative permittivity and permeab... more Recent introduction of artificial materials with simultaneously negative permittivity and permeability has initiated a lot of research activities worldwide. One of the potential important applications of the backward-wave materials could be novel guiding structures. Very recently the propagation below cut-off frequency of a waveguide loaded with split-ring resonators (the resonant inclusions usually used for synthesis of negative permeability) was demonstrated. This phenomenon was interpreted by thinking of the waveguide below cut-off frequency of dominant TE mode as the one-dimensional material with negative effective permittivity. Therefore, the waveguide loaded with split-ring resonators was interpreted as a material with both negative permeability and negative permittivity. Although the experimental results show the propagation bellow the cut-off, it was not attempted to verify the existence of the backward waves. In this paper, the original experiment is analyzed and novel physical interpretation is proposed. It is shown that propagation below the cut-off frequency actually occurs due to uniaxial anisotropy of negative permeability of meta-material based on split ring resonators. If one allows usage of anisotropic material for waveguide filling it is not longer necessary to have both permittivity and permeability with same signs. Propagation is also possible if either permeability in transversal direction (for TE modes) or permittivity in transversal direction (for TM modes) has negative sign. In the case of TE modes, the waveguide supports propagation of backward waves below cut-off frequency of an empty waveguide There is no theoretical limit on the lowest frequency of propagation providing that one is able to fabricate uniaxial negative permeability material at given frequency. Thus, it becomes possible to fabricate the waveguide with transversal dimension smaller than half of the wavelength. The simple explanation this peculiar phenomenon is given by analysis of transmission line model of the waveguide. The series inductance per unit length and shunt inductance per unit length have the same sign if the waveguide is filled with isotropic magnetic material (either double positive material or double negative material). On contrary, if the waveguide is filled with uniaxial material with negative permeability in transversal direction, the series inductance will be negative. At one fixed frequency, one can think of negative series inductance as the ordinary capacitance. If the operating frequency is located below cut-off, the equivalent circuit now comprises series capacitance and shunt inductance similar to the left-handed transmission line introduced in. Therefore, the propagation in the form of backward waves becomes possible below the cut-off frequency. Two experimental rectangular waveguides loaded with split-ring resonators in 10 GHz frequency band have been designed, fabricated and tested. The measured results revealed backward-wave pass-band located below the cut off frequency. It was also shown that the increase of physical length of the waveguide caused the decrease of the electrical length. This is the direct proof of backward-wave propagation since the phase of backward wave increases along the waveguide.
2019 23rd International Conference on Applied Electromagnetics and Communications (ICECOM)
Antenna arrays with beam scanning are composed of phase shifters. With a large number of elements... more Antenna arrays with beam scanning are composed of phase shifters. With a large number of elements, the phase shifter control current can be very large. In particular cases, at fixed angles of beam orientation, the control current can be minimized by introducing an additional phase shift to all elements of the antenna array. The article analyzes the value of the current control phase shifters in the 308-element antenna array of the radar wind profiler.
2020 Ural Symposium on Biomedical Engineering, Radioelectronics and Information Technology (USBEREIT)
Antenna arrays that perform electonic beam deviation have phase shifters in their composition. In... more Antenna arrays that perform electonic beam deviation have phase shifters in their composition. In case of large number of antennas in array, the phase shifter control current can be very big. Particulary, the control current of phase shifters could be optimized to a minimum by providing an additional equal phase shift to all elements of the array. The article contains the study of the value of the current control phase shifters in the 308-element antenna array of the wind profiler radar. It was shown that control current varies a lot with an additional phase step for all phase shifters. Difference between maximum and minimum current depends on a deviation angle and minimal step of the phase shifter. The second part of the article dedicated to influence of phase discrete on the antenna array directivity. In particular, it consists estimation of directivity decreasing when the beam is deviated from the normal position by different angles.
A generalized spectral Green's function formulation of N-layer substrate structure is given with ... more A generalized spectral Green's function formulation of N-layer substrate structure is given with three dimension sources, which is a set of closed form formulas. A full-wave analysis model for rectangular microstrip antennas covered with N-dielectric layers has been established by using the above spectral Green's function. The unknown surface current density on the nficrostrip patch for such structure is found as a solution of an integral equation. The input VSWR and radiation patterns of the antenna are also obtained. The numerical results have been verified by the experimental results" Key words Microstrip antenna; N-layer dielectric cover; Full-wave analysis; Spectral Green's function *Partly supported by the Research Item B96(56) of the Ministry of Railways of China
2019 European Microwave Conference in Central Europe (EuMCE), 2019
Characteristics of textile antennas integrated in clothing are affected by moisture from e.g. rai... more Characteristics of textile antennas integrated in clothing are affected by moisture from e.g. rain or perspiration. A wideband planar monopole was adapted for implementation as full textile antenna. The monopole was manufactured by embroidering. The influence of moisture on wideband textile monopole antenna has been investigated by observing the input reflection coefficient, gain and radiation patterns. It was demonstrated that wideband textile antennas are more resilient to moisture in comparison to the resonant ones.
section with the first slot. The purpose of this antenna was to emphasise the effect of an added ... more section with the first slot. The purpose of this antenna was to emphasise the effect of an added short circuited slot on the CP performance, i.e. to control the effectiveness of the final switchable antenna including two slots and pin diodes (Fig. 2). The short circuits were made with 0. I nun-wide strips, which model ideal forward biased pin diodes (ON state), located at 3nun from the slot intersection. Provided that the lengths of the antenna and the slot were tuned (Lp = 16.9mm, LY = 15.4mm), a 4% CP bandwidth was kept with good return loss perfonnances. Nevertheless, the addition of a second slot yields a 30OMHz drop in the central C P frequency.
The surface was mounted above a vertically oriented hom antenna at 45", so that the reflected rad... more The surface was mounted above a vertically oriented hom antenna at 45", so that the reflected radiation was directed into the horizontal plane. The surface and ham were rotated together, and the radiation pattcm was measured with a stationary rccciving horn. The patterns for three different phase gradients are shown in Fig. 3, corresponding to beam positions of O", 20°, and 40'. Steering to the opposite direction is produced with the opposite phase gradients. Thc frequency of the plats is 4.2 GHz. and the measured bandwidth is about-5%. The surface produces approximately the expected beamwidth, patterns, and sidelobe characteristics for a 3.3 wavelength reflector. However, the partems show some dependence on frequency and steering angle, which is likely due to the phase curvarure of the ham antenna, and could be removed by adding a compensating C U N B~K C to the reflection phase function.
pred Vama je broj 1/2012 časopisa AUTOMATIKA koji sadrži devet odabranih radova s 20. Internation... more pred Vama je broj 1/2012 časopisa AUTOMATIKA koji sadrži devet odabranih radova s 20. International Conference on Applied Electromagnetics and Communications (ICECom), koja je održana u Dubrovniku od 20. 23. rujna 2010. godine. Radovi su u zbornicima skupova ograničene duljine te je stoga nekoliko autora pozvano da dostave proširene verzije radova. Petnaest je godina prošlo od prve konferencije ICECom koja je bila organizirana pod današnjim imenom, a koja nastavlja tradiciju susreta koji su organizirani od ranih 1970tih godina. Teme pokrivene konferencijom ICECom stalno se nadopunjuju kako bi se moglo prikazati stanje istraživanja u području modeliranja i konstrukcije antena, računalnih metoda u elektromagnetizmu, pokretnih i osobnih komunikacija, radarskih sustava i daljinskih istraživanja, radio navigacijskih sustava i sustava za pozicioniranje, rasprostiranja elektromagnetskih valova, RFID, elektromagnetske kompatibilnosti, elektromagnetskih mjerenja, THz-nih tehnologija, metamaterijala, itd. Prva skupina radova u ovom posebnom izdanju vezana je uz antene. Prof. Jiro Hirokawa održao je plenarno izlaganje te je u radu Antenski nizovi valovodnih otvor-antena i konverteri polarizacije izvedeni s pomoću planarnih laminata dao pregled istraživačkih aktivnosti svoje istraživačke grupe u izgradnji valovodnih antena u milimetarskome valnom području. To je danas važno pitanje jer su uvedene ili se planiraju uvesti mnoge primjene u milimetarskome valnom području. Glavni problem u izgradnji antena u tom frekvencijskom području čine gubitci i složenost izrade antena, tako da predložena tehnologija zasnovana na planarnim laminatima nudi mnoštvo prednosti. U radu Male antene: tehnike minijaturizacije i primjene, Davor Bonefačić i sur. daje izvrstan pregled tehnika koje se mogu koristiti za izgradnju malih antena antena čija je veličina ograničena veličinom ured̄aja u kojem će se antena koristiti (kao što je to slučaj s mobilnim telefonima). Sve su tehnike eksperimentalno potvrd̄ene te je u članku dana usporedba karakteristika svih predloženih rješenja. Treći članak Usporedba zrcalnog modela i modela prijenosnih linija u analizi horizontalne žičane antene iznad dvoslojnog tla, Vesna Arnautovski-Toševa i sur. razmatraju mogućnost uporabe pojednostavljenih modela za analizu žičanih antena koje se nalaze iznad višeslojnih struktura, tj. iznad realnog modela tla . Rigorozne su metode analize vremenski zahtjevne, tako da autorica istražuje točnost dvaju pojednostavljenih pristupa: zrcalnog modela i modela prijenosnih linija. Nove elektromagnetske strukture, na temelju metamaterijala s aktivnim komponentama, opisane su u radu Analiza stabilnosti u superluminlanim prijenosnim linijama zasnovanim na metamaterijalima s realnim ne-Fosterovim negativnim kondenzatorima, Silvio Hrabar i sur. U radu se daje detaljna analiza osnovnog bloka prijenosne linije izvedene uz pomoć metamaterijala – tzv. aktivni spremnik koji sadrži i konvencionalni kondenzator i ne-Fosterov negativni kondenzator. Radovi Dijagnostika antena s pomoću bezfazne NF informacije, Yuri Álvarez i sur., i Dijagram zračenja vertikalnog dipola iznad mora i pripadajući mjerni postav, Antonio Šarolić i sur., razmatraju probleme elektromagnetskih mjerenja. Za otkrivanje anomalija u promatranoj anteni najbolje je precizno izmjeriti razdiobu bliskog polja (i amplitude i faze) antene. No, to je iznimno složena zadaća, poglavito jer faza brzo varira u bliskom polju. Stoga je od velike važnosti pojednostaviti mjerenja u bliskom polju, odnosno važno je razviti mjerne postupke kod kojih bi bilo moguće izvući dovoljno informacija iz mjerenja samo raspodjele amplitude. U radu se opisuje proširenje tzv. metode rekonstrukcije izvora (SRM) za dijagnostiku antena primjenom bezfaznih mjerenja. Drugi rad vezan uz elektromagnetska mjerenja opisuje kompakOnline ISSN 1848-3380, Print ISSN 0005-1144 ATKAFF 53(1), 5–8(2012)
The paper presents the propagation analysis of ultrawideband Gaussian signal in an automated coll... more The paper presents the propagation analysis of ultrawideband Gaussian signal in an automated collaborative warehouse environment where human and robots communicate to ensure that mutual collisions do not occur. The warehouse racks are principally modeled as clusters of metallic (PEC) parallelepipeds, with dimensions chosen to approximate the realistic warehouse. The signal propagation is analyzed using a ray tracing software, with the goal to calculate the path loss profile for different representative scenarios and antenna polarizations. The influence of the rack surface roughness onto propagation is also analyzed. The guidelines for optimum antenna positions on humans and robots for safe communication are proposed according to the simulations results.
This paper presents an approach to simultaneous beamwidth and beam-steering control using an arra... more This paper presents an approach to simultaneous beamwidth and beam-steering control using an array-fed reconfigurable partially reflective surface (PRS) antenna. Requirements and trade-offs regarding the design of such antennas are discussed. The antenna operation is confirmed by full-wave simulations.
Propagation of UWB Gaussian signal in a model of automated collaborative warehouse is analyzed us... more Propagation of UWB Gaussian signal in a model of automated collaborative warehouse is analyzed using ray tracing method. The transmitting antenna is placed on the human body while the received power profiles in warehouse containing empty racks and racks filled with different loads are calculated. This gives rise to estimation of safe communication range between humans and robots.
Use and application of the GTEM-cell, which is a transmission structure based on a TEM-cell appro... more Use and application of the GTEM-cell, which is a transmission structure based on a TEM-cell approach, are described. The cell can be used for calibrating small antennas, for immunity and emission testing, and for biomedical experiments. It provides homogenous electromagnetic fields with TEM (transversal electromagnetic mode) distribution, similar to the free space. It has a shield to prevent radiation from the outside, which would interfere with our measurement. Plant Lemna minor has been exposed to the electric field similar to those of the cellular phones and the effect on the growth has been studied. The experiments included exposure to the frequencies of 400 MHz and 900 MHz with strength of electric field being 22 V/m. The time of exposure was 2 and 4 hours. The influence of AM (80%) 1 kHz sine modulation was also tested. Our investigations confirmed that electromagnetic field of frequencies produced by mobile phones or base stations can affect plant growth.
2021 Fifteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), Sep 20, 2021
This paper proposes non-Foster tank circuit that comprises both positive and negative R, L, C ele... more This paper proposes non-Foster tank circuit that comprises both positive and negative R, L, C elements. It is shown that, apart from familiar effect of broadband dispersion cancellation, it is also possible to achieve amplification and self-oscillations rooted in negative reactive elements.
In this work, the concept of ultrawideband antenna comprised of two triangular monopoles is intro... more In this work, the concept of ultrawideband antenna comprised of two triangular monopoles is introduced. The design procedure is accompained by simulation and measurement results.
Recent introduction of artificial materials with simultaneously negative permittivity and permeab... more Recent introduction of artificial materials with simultaneously negative permittivity and permeability has initiated a lot of research activities worldwide. One of the potential important applications of the backward-wave materials could be novel guiding structures. Very recently the propagation below cut-off frequency of a waveguide loaded with split-ring resonators (the resonant inclusions usually used for synthesis of negative permeability) was demonstrated. This phenomenon was interpreted by thinking of the waveguide below cut-off frequency of dominant TE mode as the one-dimensional material with negative effective permittivity. Therefore, the waveguide loaded with split-ring resonators was interpreted as a material with both negative permeability and negative permittivity. Although the experimental results show the propagation bellow the cut-off, it was not attempted to verify the existence of the backward waves. In this paper, the original experiment is analyzed and novel physical interpretation is proposed. It is shown that propagation below the cut-off frequency actually occurs due to uniaxial anisotropy of negative permeability of meta-material based on split ring resonators. If one allows usage of anisotropic material for waveguide filling it is not longer necessary to have both permittivity and permeability with same signs. Propagation is also possible if either permeability in transversal direction (for TE modes) or permittivity in transversal direction (for TM modes) has negative sign. In the case of TE modes, the waveguide supports propagation of backward waves below cut-off frequency of an empty waveguide There is no theoretical limit on the lowest frequency of propagation providing that one is able to fabricate uniaxial negative permeability material at given frequency. Thus, it becomes possible to fabricate the waveguide with transversal dimension smaller than half of the wavelength. The simple explanation this peculiar phenomenon is given by analysis of transmission line model of the waveguide. The series inductance per unit length and shunt inductance per unit length have the same sign if the waveguide is filled with isotropic magnetic material (either double positive material or double negative material). On contrary, if the waveguide is filled with uniaxial material with negative permeability in transversal direction, the series inductance will be negative. At one fixed frequency, one can think of negative series inductance as the ordinary capacitance. If the operating frequency is located below cut-off, the equivalent circuit now comprises series capacitance and shunt inductance similar to the left-handed transmission line introduced in. Therefore, the propagation in the form of backward waves becomes possible below the cut-off frequency. Two experimental rectangular waveguides loaded with split-ring resonators in 10 GHz frequency band have been designed, fabricated and tested. The measured results revealed backward-wave pass-band located below the cut off frequency. It was also shown that the increase of physical length of the waveguide caused the decrease of the electrical length. This is the direct proof of backward-wave propagation since the phase of backward wave increases along the waveguide.
2019 23rd International Conference on Applied Electromagnetics and Communications (ICECOM)
Antenna arrays with beam scanning are composed of phase shifters. With a large number of elements... more Antenna arrays with beam scanning are composed of phase shifters. With a large number of elements, the phase shifter control current can be very large. In particular cases, at fixed angles of beam orientation, the control current can be minimized by introducing an additional phase shift to all elements of the antenna array. The article analyzes the value of the current control phase shifters in the 308-element antenna array of the radar wind profiler.
2020 Ural Symposium on Biomedical Engineering, Radioelectronics and Information Technology (USBEREIT)
Antenna arrays that perform electonic beam deviation have phase shifters in their composition. In... more Antenna arrays that perform electonic beam deviation have phase shifters in their composition. In case of large number of antennas in array, the phase shifter control current can be very big. Particulary, the control current of phase shifters could be optimized to a minimum by providing an additional equal phase shift to all elements of the array. The article contains the study of the value of the current control phase shifters in the 308-element antenna array of the wind profiler radar. It was shown that control current varies a lot with an additional phase step for all phase shifters. Difference between maximum and minimum current depends on a deviation angle and minimal step of the phase shifter. The second part of the article dedicated to influence of phase discrete on the antenna array directivity. In particular, it consists estimation of directivity decreasing when the beam is deviated from the normal position by different angles.
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Papers by Juraj Bartolic