In this paper, a modified ground structure capable of reducing mutual coupling to provide isolati... more In this paper, a modified ground structure capable of reducing mutual coupling to provide isolation between adjacent antenna elements is presented. The proposed modified ground structure is a combination of a strategically located ground slot, asymmetric partial ground and a substrate-integrated pin wall. The use of the modified ground structure causes a more than 28 dB (measured value) mutual coupling reduction. The modified ground structure has been optimized and validated with a finite spaced planar 2 × 1 antenna array operating at 4.16 GHz, intended for unmanned aerial vehicle radar altimeter applications. The patch antennas built with the MGS exhibit high gain (greater than 6 dBi throughout the operational band), along with inter-element coupling as low as −65 dB. Mutual coupling reduction at lower contours is beneficial for altimeter applications.
A rugged metal protected antenna that produces an omnidirectional radiation pattern is proposed i... more A rugged metal protected antenna that produces an omnidirectional radiation pattern is proposed in this letter. The omnidirectionality is achieved by using a cavity enclosed PCB (Printed Circuit Board) with λ/4 transformers and ground shortening pins combination. The slotted cavity filled with ablative material is designed to maintain the radiation characteristics of the enclosed PCB and provide strength for the antenna arrangement, which can be effectively used on high-speed aerial platforms. The simulated and measured results demonstrate that the proposed antenna possesses a stable omnidirectional radiation pattern, its horizontal gain is higher than-1.5 dB, the azimuthal gain ripple is within ± 0.7 dB, and the antenna efficiency exceeds 85%, over the entire operational frequency band. In addition, the conformal, tapered, non-protruding, lowprofile and DC-grounded design makes winged antennas superior candidate for supersonic (Mach> 1) airborne applications.
2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall)
Considering the requirements of amplifiers for modern communication systems and having different ... more Considering the requirements of amplifiers for modern communication systems and having different topology variants with different advantages or disadvantages over each other, this paper presents experimental comparison between Class AB and High efficiency Class F−1 power amplifiers using GaN based Transistors. The results show that Class F−1 power amplifier exhibit higher output power and higher efficiency but degraded linearity response as compared to class AB power amplifier. For comparison, the inverse class F and class AB power amplifiers were designed and implemented at 2.14 GHz using GaN Hemt. Measured performance showed 7% higher power added efficiency along with 0.3 dB increase in output power for inverse class F power amplifier.
In this paper, a new slant-polarized slot antenna configuration is presented for direction findin... more In this paper, a new slant-polarized slot antenna configuration is presented for direction finding and base station applications. The proposed antenna comprises enhanced size coaxial cables, slots, and feeding assemblies. The slant polarization is achieved by four angled slots etched around the outer cylinder of the oversized coaxial cable. An internal compact axis-symmetric feeding network connects primary apertures to form the omnidirectional antenna. Simulations and measurements demonstrate that the antenna maintains an omnidirectional pattern from 2.5 GHz to 2.8 GHz, having 11.3% bandwidth (measured return loss <−10 dB) and gain ripple of ±0.2 dB in the azimuth plane, which leads to the stable operational coverage. Another benefit of this structure is its polarization purity. The cross-polarization levels are below-14dB over the whole bandwidth. Move over; it is ruggedized DC short, self-supporting, and surface-mountable structure. Furthermore, compact and conformal shape reduces aerodynamic drag and makes this antenna a potential candidate for mounting vehicle systems too. INDEX TERMS Omnidirectional, gain ripple, slant polarization, dc ground, rugged.
2020 International Conference on UK-China Emerging Technologies (UCET), 2020
This paper presents a compact mixed coupled quarter-wavelength $(\lambda/4)$ resonator filter emp... more This paper presents a compact mixed coupled quarter-wavelength $(\lambda/4)$ resonator filter employing J/K inverters and coupling-path phases. In contrast to conventional mixed coupled models, the proposed method makes use of separated J and K inverters to obtain desired electric and magnetic couplings respectively. A transmission zero (TZ) below passband is created by applying capacitive dominant mixed coupling between $\lambda$/4 uniform impedance resonators (UIRs). In addition to coupling magnitude, the TZ also depends on coupling path phases. Tapped feed lines implied between resonators and input-output (I/O) ports provide necessary electrical length ratio between J and K coupling paths. A fourth order prototype filter at 10GHZ with 6.8% fractional bandwidth (FBW) is designed, fabricated and tested. The measured results show good agreement with simulated response, which verifies the design approach.
2019 International Symposium on Antennas and Propagation (ISAP), 2019
This paper presents a high power, high efficiency power amplifier using GaN HEMT class F inverse ... more This paper presents a high power, high efficiency power amplifier using GaN HEMT class F inverse with harmonic termination network at operating frequency 2.14GHZ. The optimum impedances for input and output 1st,2nd, and 3rd harmonics were extracted using load and source pull analysis. Effect of with and without harmonic termination on the performance of class F inverse power amplifier is evaluated by its output power, PAE and gate stress. Propose class F inverse amplifier is fabricated on RO4350B. Measured results indicate that class F inverse power amplifier has achieved high output power 36.3dBm with high efficiency of 71%.
A new slot-based antenna design capable of producing horizontal polarization for unmanned aerial ... more A new slot-based antenna design capable of producing horizontal polarization for unmanned aerial vehicle (UAV) ground control station (GCS) applications is outlined in this paper. The proposed antenna consists of oversize coaxial cylinders, slots, and slot-feed assembly. Each of the four vertical slots, arranged periodically around the antenna’s outer cylinder, emits a horizontally polarized broad beam of radiation, in phase, to produce an omnidirectional pattern. The antenna possesses a low-ripple ±0.5 dB in azimuth gain (yaw) due to its symmetric axis shape and an enclosed feed within itself, which does not radiate and interfere with the main azimuth pattern. This is crucial for a UAV GCS to symmetrically extend its coverage range in all directions against yaw planes. Simulation and measurement results reveal that the antenna maintains stable gain in the omnidirectional pattern (+0.5 dB) over the entire operational frequency band (2.55 GHz to 2.80 GHz), where S11 is lower than −10...
Design of a high power, high efficiency GaN HEMT based Class F power amplifier with harmonic term... more Design of a high power, high efficiency GaN HEMT based Class F power amplifier with harmonic termination network, operational at 2.1 GHz, has been presented in this paper. Optimum source and load impedances for fundamental tone, 2nd and 3rd harmonics were extracted using load and source pull analysis. Effect of with and without harmonic termination on the performance of class F power amplifier is investigated in term of output power, power added efficiency and drain bias variation. Proposed class F power amplifier is fabricated using RT/Duroid 5870 of 20 mil thickness. Designed structure possess power added efficiency of 72% with high output power of 36.3 dBm. In order to further enhance efficiency of power amplifier, it was operated at lower drain bias current resulting in efficiency enhancement of 6% with no significant change in output power performance.
Desktop 3D printers are fast becoming a household item. Easy access to additive manufacturing cou... more Desktop 3D printers are fast becoming a household item. Easy access to additive manufacturing could lead to discrepancies in the quality of 3D printed parts. The purpose of this research is to establish methodologies to systematically evaluate the mechanical quality and dimensional accuracy of 3D printed parts. For the evaluation of the mechanical quality, several plastic specimens were tested on a universal testing machine (MTS Q-Test, Eden Prairie, Minnesota) to generate stress-strain profiles following ASTM D638 standards for plastic components. For the dimensional accuracy, several challenging and unconventional structures were printed. These structures allow to systematically quantify dimensional and geometrical features. The large amount of printing undertaken during this project exposed many issues related to the process of 3D printing itself. This allowed insight into the different techniques incorporated in the process of additive manufacturing which proves to be beneficial...
A dual and quad element antenna array resonating at 2.4 GHz with narrow beam is proposed in this ... more A dual and quad element antenna array resonating at 2.4 GHz with narrow beam is proposed in this paper. An intention to put forward this work is to make use of microstrip patch antennas in beamforming to form directional beams in analog and digital domains; reducing co-channel / multipath interferences and improving Quality of Service (QoS) for senor arrays and 3G wireless networks. The size of dual and quad element antenna array is 60 x 130 mm2 and 60 x 240 mm2 respectively. Simulations in HFSS (High Frequency Structure Simulator) showed least mutual coupling among adjacent elements and prototypes have been fabricated using FR4 to verify the efficiency of the presented work for IEEE 802.11b/g WLAN standards. Streszczenie. W artykule przedstawiono dwu- i czteroelementowy uklad anten o wąskim strumieniu promieniowania, o czestotliwości rezonansowej 2,4 GHz oraz mozliwości wykorzystania w przesyle sygnalu. (Uklad anten mikropaskowych w systemach ksztaltowania strumienia promieniowania...
In this article a high power (320 watt), high efficiency (greater than 56 %) LDMOS based power am... more In this article a high power (320 watt), high efficiency (greater than 56 %) LDMOS based power amplifier configuration is proposed. Proposed compact class-AB amplifier is designed using non-linear model of MRF8P29300, targeting S-band. Along with optimization using ADS, hybrid couplers are used to improve the performance of proposed amplifier, providing output power of 56 dBm. Other than design details, paper also present electromagnetic and thermal analysis for better understanding of amplifier characteristics. Moreover, measured results indicate that proposed amplifier achieved 14dB gain, gain flatness <0.7dB and input/output return loss <-12dB; which make proposed amplifier worthy and prospective candidate for surveillance and tracking radars.
In this paper, a modified ground structure capable of reducing mutual coupling to provide isolati... more In this paper, a modified ground structure capable of reducing mutual coupling to provide isolation between adjacent antenna elements is presented. The proposed modified ground structure is a combination of a strategically located ground slot, asymmetric partial ground and a substrateintegrated pin wall. The use of the modified ground structure causes a more than 28 dB (measured value) mutual coupling reduction. The modified ground structure has been optimized and validated with a finite spaced planar 2 × 1 antenna array operating at 4.16 GHz, intended for unmanned aerial vehicle radar altimeter applications. The patch antennas built with the MGS exhibit high gain (greater than 6 dBi throughout the operational band), along with inter-element coupling as low as −65 dB. Mutual coupling reduction at lower contours is beneficial for altimeter applications.
2019 8th Asia-Pacific Conference on Antennas and Propagation (APCAP)
In this article a single center-fed circular polarized conical-beam antenna for vehicle mounted a... more In this article a single center-fed circular polarized conical-beam antenna for vehicle mounted applications is presented. Antenna configuration contains hybrid of vertically polarized slot-loop arrangement and horizontally polarized stubs to provide circular polarization features. Artificial Magnetic Conductor is used to enhance gain and to avoid circular polarization distortion while being mounted over metallic platforms. Proposed antenna possesses high and stable left-hand circular polarization gain (7.2 ± .2 dBic) and symmetric omni-directional radiation characteristics, offers circular polarization from theta 4° to 35° and −4° to −35°, against all pi angles that are 180° to −180°, in 2.8 to 2.93 GHz frequency range.
The enhancement of optical characteristics at optical frequencies deviates with the choice of the... more The enhancement of optical characteristics at optical frequencies deviates with the choice of the arrangement of core-shell nanoparticles and their environment. Likewise, the arrangements of core-shell nanoparticles in the air over a substrate or in liquid solution makes them unstable in the atmosphere. This article suggests designing a configuration of an active spherical coated nanoparticle antenna and its extended array in the presence of a passive dielectric, which is proposed to be extendable to construct larger arrays. The issue of instability in the core-shell nanoantenna array models is solved here by inserting the passive dielectric. In addition to this, the inclusion of a dielectric in the array model reports a different directivity behaviour than the conventional array models. We found at first that the combination model of the active coated nanoparticle and passive sphere at the resonant frequency can excite a stronger field with a rotated polarization direction and a pr...
Circularly-polarized planar antenna with a shaped pattern for airborne applications, is proposed ... more Circularly-polarized planar antenna with a shaped pattern for airborne applications, is proposed in this letter. The proposed antenna consists of vertically-polarized formation and horizontally-polarized stubs to provide circularly-polarized configuration, which is loaded by a copper curl based top layer to control current distribution for beam shaping and filling of zenith null. The antenna also contains split ring resonators beside partial ground to make it deployable over larger ground planes (metallic bodies) without distorting circular polarization by controlling phase of reflected waves. The power density of presented airborne shaped pattern antenna differs for variant elevation and azimuth angles, to have uniform wireless coverage over the earth's surface by managing variations of the signal strength because of different path lengths. The demonstrated antenna also possesses circular polarization and direction based circular polarization diversity at angles against the greatest path-lengths. Antenna retains a null-filled pattern in the vertical plane along with having high absolute peak gain (5.5 ± 1 dBi) and adequate peak polarization gain (2 to 4 dBi) throughout the operational bandwidth from 2.82 GHz to 2.89 GHz (Measured reflection coefficient less than −10 dB). Moreover, the radiating element exhibits omnidirectional radiation characteristics, with good horizontal gain (greater than −3.6 dBi).
In this letter, a null-filled shaped beam planar monopole antenna for aerial platform application... more In this letter, a null-filled shaped beam planar monopole antenna for aerial platform applications is presented. The proposed antenna consists of a slot and a loop hybrid to give vertically polarized monopole configuration, which is overlapped by a curl to control current distribution that leads to filling of radiation null and shaping the beam. The antenna possesses different gain amplitudes at different yaw and pitch angles, as being required by aerial platforms to cover variant distance ranges in various directions. Simulated and measured results exhibit that the antenna retains null-filled pattern in vertical plane, along with high, stable, and linear peak gains (6.4 ± .4 dBi), over the entire operation band that is from 2.54 to 2.69 GHz (measured reflection coefficient less than –10 dB). The proposed antenna displays an omnidirectional radiation characteristics and a good gain in azimuth plane, having the minimum horizontal gain of –2.85 dBi. Furthermore, flaunted antenna is rigid, planar, aerodynamically stable, and surface-mounted, which makes the proposed antenna a prospective and worthy candidate for aerial platforms.
This paper presents the design of compact cross-coupled microstrip trisection bandpass filters ba... more This paper presents the design of compact cross-coupled microstrip trisection bandpass filters based on the hybrid structures of quarter-wavelength (λ/4) and half-wavelength (λ/2) resonators. The desired cross-couplings for transmission zeros (TZ) are realized by parallel coupled transmission line sections (Jinverter) or coupled via sections (K-inverter) of λ/4 resonators. The main line couplings on the other hand, are formed by mixed-coupled λ/4 and λ/2 resonators. In order to validate the proposed hybrid configurations, two X-band trisection filters with 6.5% and 6.2% fractional bandwidth (FBW) were designed, fabricated and measured. The first filter generates a TZ below the passband, while the second one produces a TZ above the passband. Minimum insertion loss of 1.7 dB and 1.5 dB were observed for the two trisection filters, respectively, while the hybrid configurations caused significant size reduction in the overall filter size. Moreover, the first spurious response for the proposed filter topologies was pushed to 3fo, resulting in a widestopband-fo is the passband center frequency. The measured and simulated S-parameters show good agreement, which proves the validity and accuracy of the proposed hybrid design methodology.
This paper presents a narrow band frequency reconfigurable antenna for global navigation systems.... more This paper presents a narrow band frequency reconfigurable antenna for global navigation systems. Proposed frequency tunable antenna operates for GLONASS (1.601 GHz), GPS (1.575 GHz) and COMPASS (1.561 GHz) navigational systems. Antenna design consists of rectangular patches, two pin-diode switches, feed network, biasing circuitry and supply lines to make antenna operational for three frequency bands. Antenna is simulated and optimized using CST—Computer simulation technology and is fabricated on Roger RO4350b substrate. The demonstrated antenna along with being frequency agile possess essential performance characteristics like high gain, stable radiation patterns and good radiation efficiency for all three frequency bands, making it prospective choice for wireless navigational systems.
In this paper, a modified ground structure capable of reducing mutual coupling to provide isolati... more In this paper, a modified ground structure capable of reducing mutual coupling to provide isolation between adjacent antenna elements is presented. The proposed modified ground structure is a combination of a strategically located ground slot, asymmetric partial ground and a substrate-integrated pin wall. The use of the modified ground structure causes a more than 28 dB (measured value) mutual coupling reduction. The modified ground structure has been optimized and validated with a finite spaced planar 2 × 1 antenna array operating at 4.16 GHz, intended for unmanned aerial vehicle radar altimeter applications. The patch antennas built with the MGS exhibit high gain (greater than 6 dBi throughout the operational band), along with inter-element coupling as low as −65 dB. Mutual coupling reduction at lower contours is beneficial for altimeter applications.
A rugged metal protected antenna that produces an omnidirectional radiation pattern is proposed i... more A rugged metal protected antenna that produces an omnidirectional radiation pattern is proposed in this letter. The omnidirectionality is achieved by using a cavity enclosed PCB (Printed Circuit Board) with λ/4 transformers and ground shortening pins combination. The slotted cavity filled with ablative material is designed to maintain the radiation characteristics of the enclosed PCB and provide strength for the antenna arrangement, which can be effectively used on high-speed aerial platforms. The simulated and measured results demonstrate that the proposed antenna possesses a stable omnidirectional radiation pattern, its horizontal gain is higher than-1.5 dB, the azimuthal gain ripple is within ± 0.7 dB, and the antenna efficiency exceeds 85%, over the entire operational frequency band. In addition, the conformal, tapered, non-protruding, lowprofile and DC-grounded design makes winged antennas superior candidate for supersonic (Mach> 1) airborne applications.
2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall)
Considering the requirements of amplifiers for modern communication systems and having different ... more Considering the requirements of amplifiers for modern communication systems and having different topology variants with different advantages or disadvantages over each other, this paper presents experimental comparison between Class AB and High efficiency Class F−1 power amplifiers using GaN based Transistors. The results show that Class F−1 power amplifier exhibit higher output power and higher efficiency but degraded linearity response as compared to class AB power amplifier. For comparison, the inverse class F and class AB power amplifiers were designed and implemented at 2.14 GHz using GaN Hemt. Measured performance showed 7% higher power added efficiency along with 0.3 dB increase in output power for inverse class F power amplifier.
In this paper, a new slant-polarized slot antenna configuration is presented for direction findin... more In this paper, a new slant-polarized slot antenna configuration is presented for direction finding and base station applications. The proposed antenna comprises enhanced size coaxial cables, slots, and feeding assemblies. The slant polarization is achieved by four angled slots etched around the outer cylinder of the oversized coaxial cable. An internal compact axis-symmetric feeding network connects primary apertures to form the omnidirectional antenna. Simulations and measurements demonstrate that the antenna maintains an omnidirectional pattern from 2.5 GHz to 2.8 GHz, having 11.3% bandwidth (measured return loss <−10 dB) and gain ripple of ±0.2 dB in the azimuth plane, which leads to the stable operational coverage. Another benefit of this structure is its polarization purity. The cross-polarization levels are below-14dB over the whole bandwidth. Move over; it is ruggedized DC short, self-supporting, and surface-mountable structure. Furthermore, compact and conformal shape reduces aerodynamic drag and makes this antenna a potential candidate for mounting vehicle systems too. INDEX TERMS Omnidirectional, gain ripple, slant polarization, dc ground, rugged.
2020 International Conference on UK-China Emerging Technologies (UCET), 2020
This paper presents a compact mixed coupled quarter-wavelength $(\lambda/4)$ resonator filter emp... more This paper presents a compact mixed coupled quarter-wavelength $(\lambda/4)$ resonator filter employing J/K inverters and coupling-path phases. In contrast to conventional mixed coupled models, the proposed method makes use of separated J and K inverters to obtain desired electric and magnetic couplings respectively. A transmission zero (TZ) below passband is created by applying capacitive dominant mixed coupling between $\lambda$/4 uniform impedance resonators (UIRs). In addition to coupling magnitude, the TZ also depends on coupling path phases. Tapped feed lines implied between resonators and input-output (I/O) ports provide necessary electrical length ratio between J and K coupling paths. A fourth order prototype filter at 10GHZ with 6.8% fractional bandwidth (FBW) is designed, fabricated and tested. The measured results show good agreement with simulated response, which verifies the design approach.
2019 International Symposium on Antennas and Propagation (ISAP), 2019
This paper presents a high power, high efficiency power amplifier using GaN HEMT class F inverse ... more This paper presents a high power, high efficiency power amplifier using GaN HEMT class F inverse with harmonic termination network at operating frequency 2.14GHZ. The optimum impedances for input and output 1st,2nd, and 3rd harmonics were extracted using load and source pull analysis. Effect of with and without harmonic termination on the performance of class F inverse power amplifier is evaluated by its output power, PAE and gate stress. Propose class F inverse amplifier is fabricated on RO4350B. Measured results indicate that class F inverse power amplifier has achieved high output power 36.3dBm with high efficiency of 71%.
A new slot-based antenna design capable of producing horizontal polarization for unmanned aerial ... more A new slot-based antenna design capable of producing horizontal polarization for unmanned aerial vehicle (UAV) ground control station (GCS) applications is outlined in this paper. The proposed antenna consists of oversize coaxial cylinders, slots, and slot-feed assembly. Each of the four vertical slots, arranged periodically around the antenna’s outer cylinder, emits a horizontally polarized broad beam of radiation, in phase, to produce an omnidirectional pattern. The antenna possesses a low-ripple ±0.5 dB in azimuth gain (yaw) due to its symmetric axis shape and an enclosed feed within itself, which does not radiate and interfere with the main azimuth pattern. This is crucial for a UAV GCS to symmetrically extend its coverage range in all directions against yaw planes. Simulation and measurement results reveal that the antenna maintains stable gain in the omnidirectional pattern (+0.5 dB) over the entire operational frequency band (2.55 GHz to 2.80 GHz), where S11 is lower than −10...
Design of a high power, high efficiency GaN HEMT based Class F power amplifier with harmonic term... more Design of a high power, high efficiency GaN HEMT based Class F power amplifier with harmonic termination network, operational at 2.1 GHz, has been presented in this paper. Optimum source and load impedances for fundamental tone, 2nd and 3rd harmonics were extracted using load and source pull analysis. Effect of with and without harmonic termination on the performance of class F power amplifier is investigated in term of output power, power added efficiency and drain bias variation. Proposed class F power amplifier is fabricated using RT/Duroid 5870 of 20 mil thickness. Designed structure possess power added efficiency of 72% with high output power of 36.3 dBm. In order to further enhance efficiency of power amplifier, it was operated at lower drain bias current resulting in efficiency enhancement of 6% with no significant change in output power performance.
Desktop 3D printers are fast becoming a household item. Easy access to additive manufacturing cou... more Desktop 3D printers are fast becoming a household item. Easy access to additive manufacturing could lead to discrepancies in the quality of 3D printed parts. The purpose of this research is to establish methodologies to systematically evaluate the mechanical quality and dimensional accuracy of 3D printed parts. For the evaluation of the mechanical quality, several plastic specimens were tested on a universal testing machine (MTS Q-Test, Eden Prairie, Minnesota) to generate stress-strain profiles following ASTM D638 standards for plastic components. For the dimensional accuracy, several challenging and unconventional structures were printed. These structures allow to systematically quantify dimensional and geometrical features. The large amount of printing undertaken during this project exposed many issues related to the process of 3D printing itself. This allowed insight into the different techniques incorporated in the process of additive manufacturing which proves to be beneficial...
A dual and quad element antenna array resonating at 2.4 GHz with narrow beam is proposed in this ... more A dual and quad element antenna array resonating at 2.4 GHz with narrow beam is proposed in this paper. An intention to put forward this work is to make use of microstrip patch antennas in beamforming to form directional beams in analog and digital domains; reducing co-channel / multipath interferences and improving Quality of Service (QoS) for senor arrays and 3G wireless networks. The size of dual and quad element antenna array is 60 x 130 mm2 and 60 x 240 mm2 respectively. Simulations in HFSS (High Frequency Structure Simulator) showed least mutual coupling among adjacent elements and prototypes have been fabricated using FR4 to verify the efficiency of the presented work for IEEE 802.11b/g WLAN standards. Streszczenie. W artykule przedstawiono dwu- i czteroelementowy uklad anten o wąskim strumieniu promieniowania, o czestotliwości rezonansowej 2,4 GHz oraz mozliwości wykorzystania w przesyle sygnalu. (Uklad anten mikropaskowych w systemach ksztaltowania strumienia promieniowania...
In this article a high power (320 watt), high efficiency (greater than 56 %) LDMOS based power am... more In this article a high power (320 watt), high efficiency (greater than 56 %) LDMOS based power amplifier configuration is proposed. Proposed compact class-AB amplifier is designed using non-linear model of MRF8P29300, targeting S-band. Along with optimization using ADS, hybrid couplers are used to improve the performance of proposed amplifier, providing output power of 56 dBm. Other than design details, paper also present electromagnetic and thermal analysis for better understanding of amplifier characteristics. Moreover, measured results indicate that proposed amplifier achieved 14dB gain, gain flatness <0.7dB and input/output return loss <-12dB; which make proposed amplifier worthy and prospective candidate for surveillance and tracking radars.
In this paper, a modified ground structure capable of reducing mutual coupling to provide isolati... more In this paper, a modified ground structure capable of reducing mutual coupling to provide isolation between adjacent antenna elements is presented. The proposed modified ground structure is a combination of a strategically located ground slot, asymmetric partial ground and a substrateintegrated pin wall. The use of the modified ground structure causes a more than 28 dB (measured value) mutual coupling reduction. The modified ground structure has been optimized and validated with a finite spaced planar 2 × 1 antenna array operating at 4.16 GHz, intended for unmanned aerial vehicle radar altimeter applications. The patch antennas built with the MGS exhibit high gain (greater than 6 dBi throughout the operational band), along with inter-element coupling as low as −65 dB. Mutual coupling reduction at lower contours is beneficial for altimeter applications.
2019 8th Asia-Pacific Conference on Antennas and Propagation (APCAP)
In this article a single center-fed circular polarized conical-beam antenna for vehicle mounted a... more In this article a single center-fed circular polarized conical-beam antenna for vehicle mounted applications is presented. Antenna configuration contains hybrid of vertically polarized slot-loop arrangement and horizontally polarized stubs to provide circular polarization features. Artificial Magnetic Conductor is used to enhance gain and to avoid circular polarization distortion while being mounted over metallic platforms. Proposed antenna possesses high and stable left-hand circular polarization gain (7.2 ± .2 dBic) and symmetric omni-directional radiation characteristics, offers circular polarization from theta 4° to 35° and −4° to −35°, against all pi angles that are 180° to −180°, in 2.8 to 2.93 GHz frequency range.
The enhancement of optical characteristics at optical frequencies deviates with the choice of the... more The enhancement of optical characteristics at optical frequencies deviates with the choice of the arrangement of core-shell nanoparticles and their environment. Likewise, the arrangements of core-shell nanoparticles in the air over a substrate or in liquid solution makes them unstable in the atmosphere. This article suggests designing a configuration of an active spherical coated nanoparticle antenna and its extended array in the presence of a passive dielectric, which is proposed to be extendable to construct larger arrays. The issue of instability in the core-shell nanoantenna array models is solved here by inserting the passive dielectric. In addition to this, the inclusion of a dielectric in the array model reports a different directivity behaviour than the conventional array models. We found at first that the combination model of the active coated nanoparticle and passive sphere at the resonant frequency can excite a stronger field with a rotated polarization direction and a pr...
Circularly-polarized planar antenna with a shaped pattern for airborne applications, is proposed ... more Circularly-polarized planar antenna with a shaped pattern for airborne applications, is proposed in this letter. The proposed antenna consists of vertically-polarized formation and horizontally-polarized stubs to provide circularly-polarized configuration, which is loaded by a copper curl based top layer to control current distribution for beam shaping and filling of zenith null. The antenna also contains split ring resonators beside partial ground to make it deployable over larger ground planes (metallic bodies) without distorting circular polarization by controlling phase of reflected waves. The power density of presented airborne shaped pattern antenna differs for variant elevation and azimuth angles, to have uniform wireless coverage over the earth's surface by managing variations of the signal strength because of different path lengths. The demonstrated antenna also possesses circular polarization and direction based circular polarization diversity at angles against the greatest path-lengths. Antenna retains a null-filled pattern in the vertical plane along with having high absolute peak gain (5.5 ± 1 dBi) and adequate peak polarization gain (2 to 4 dBi) throughout the operational bandwidth from 2.82 GHz to 2.89 GHz (Measured reflection coefficient less than −10 dB). Moreover, the radiating element exhibits omnidirectional radiation characteristics, with good horizontal gain (greater than −3.6 dBi).
In this letter, a null-filled shaped beam planar monopole antenna for aerial platform application... more In this letter, a null-filled shaped beam planar monopole antenna for aerial platform applications is presented. The proposed antenna consists of a slot and a loop hybrid to give vertically polarized monopole configuration, which is overlapped by a curl to control current distribution that leads to filling of radiation null and shaping the beam. The antenna possesses different gain amplitudes at different yaw and pitch angles, as being required by aerial platforms to cover variant distance ranges in various directions. Simulated and measured results exhibit that the antenna retains null-filled pattern in vertical plane, along with high, stable, and linear peak gains (6.4 ± .4 dBi), over the entire operation band that is from 2.54 to 2.69 GHz (measured reflection coefficient less than –10 dB). The proposed antenna displays an omnidirectional radiation characteristics and a good gain in azimuth plane, having the minimum horizontal gain of –2.85 dBi. Furthermore, flaunted antenna is rigid, planar, aerodynamically stable, and surface-mounted, which makes the proposed antenna a prospective and worthy candidate for aerial platforms.
This paper presents the design of compact cross-coupled microstrip trisection bandpass filters ba... more This paper presents the design of compact cross-coupled microstrip trisection bandpass filters based on the hybrid structures of quarter-wavelength (λ/4) and half-wavelength (λ/2) resonators. The desired cross-couplings for transmission zeros (TZ) are realized by parallel coupled transmission line sections (Jinverter) or coupled via sections (K-inverter) of λ/4 resonators. The main line couplings on the other hand, are formed by mixed-coupled λ/4 and λ/2 resonators. In order to validate the proposed hybrid configurations, two X-band trisection filters with 6.5% and 6.2% fractional bandwidth (FBW) were designed, fabricated and measured. The first filter generates a TZ below the passband, while the second one produces a TZ above the passband. Minimum insertion loss of 1.7 dB and 1.5 dB were observed for the two trisection filters, respectively, while the hybrid configurations caused significant size reduction in the overall filter size. Moreover, the first spurious response for the proposed filter topologies was pushed to 3fo, resulting in a widestopband-fo is the passband center frequency. The measured and simulated S-parameters show good agreement, which proves the validity and accuracy of the proposed hybrid design methodology.
This paper presents a narrow band frequency reconfigurable antenna for global navigation systems.... more This paper presents a narrow band frequency reconfigurable antenna for global navigation systems. Proposed frequency tunable antenna operates for GLONASS (1.601 GHz), GPS (1.575 GHz) and COMPASS (1.561 GHz) navigational systems. Antenna design consists of rectangular patches, two pin-diode switches, feed network, biasing circuitry and supply lines to make antenna operational for three frequency bands. Antenna is simulated and optimized using CST—Computer simulation technology and is fabricated on Roger RO4350b substrate. The demonstrated antenna along with being frequency agile possess essential performance characteristics like high gain, stable radiation patterns and good radiation efficiency for all three frequency bands, making it prospective choice for wireless navigational systems.
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Papers by Hamza Nawaz