Proposed Feeding Network Research Articles

Butler matrix-based beamforming with polarization reconfigurability for reducing electromagnetic interference

In this paper, Circular-Polarization (CP) reconfigurability, switched beamforming, and Side Lobe Level (SLL) reduction necessary for electromagnetic interference suppression are achieved thanks to a novel modified single-layer 4×8 Butler Matrix (BM). The proposed feeding network is capable of exciting a linear array composed of four square patch antennas. Each antenna element is fed from its both adjacent edges with a ±90°phase difference, thus resulting in Left-Handed or Right-Handed Circular Polarizations (LHCP or RHCP). The suggested feeding network also reduces the SLL by engendering tapered amplitude distributions in its output ports. This feature has been introduced for the first time in a system providing simultaneous beam switching and polarization reconfigurability. It should be mentioned that beamforming is performed as the BM can generate progressive phase differences regarding the input port selected for the excitation. All the above-mentioned characteristics are well received by a straightforward and flexible modification in 4×8 BM. A sample of the structure operating at 2.4 GHz is designed, fabricated, and measured. Furthermore, the theta bandwidth in both RHCP and LHCP cases is evaluated, showing the full coverage of azimuth plane from –60 to 60 degree with an Axial Ratio (AR) below 3 dB.

A novel radial network for feeding concentric ring antenna arrays

This paper presents a novel radial network for feeding concentric ring antenna arrays. The proposed feeding network consists of a radial network of 1 input to 20 outputs. Two stages are required for this planar radial network: a radial power divider of 1 to 5 and a cascade Wilkinson power divider of 1 to 4 to generate 20 outputs that feed to a concentric rings antenna array. The proposed radial network provides a feeding network having balance in magnitude and phase to be applied in antenna systems based on a concentric rings array geometry. The paper provides as an interesting contribution the full antenna system considering the proposed radial feeding network (1 to 20) and the concentric rings antenna array. Full wave electromagnetic simulations and experimental measurements are implemented to verify the performance of matching, bandwidth and radiation pattern of the full system taking the mutual coupling into account.

A Compact Four Elements PIFA Array for RFID Reader Applications

In this paper, a novel compact 2×2 Planar Inverted-F Antenna (PIFA) array with four elements is proposed. This antenna array operates in Industrial, Scientific, and Medical (ISM) band for Radio Frequency Identification (RFID) reader applications, and it consists of four identical PIFAs radiating elements placed on the top of the upper substrate, two substrates, and a proposed feeding network placed on the bottom of the lower substrate. The PIFAs radiating elements are placed at the edges of the ground plane to reduce mutual coupling between them. The total size of the antenna array is only 62×45×8.6 mm3. The substrate used is FR4 with constant dielectric relativity of 4.4, a thickness of 0.035 mm, and a height of 1.6 mm. The proposed antenna is simulated and optimized using Computer Simulation Technology Microwave Studio (CST MWS) software. Simulation results show that the PIFA array offers good characteristics in terms of reflection coefficient, isolation (decoupling), and radiation patterns which makes it a good candidate for ISM band applications.

A Novel 1.05 GHz to 1.25 GHz Filtering Antenna Feeding Network With Reconfigurable Frequency and Polarization

In this article, a novel 1.05-1.25 GHz filtering antenna feeding network with reconfigurable frequency and polarization is proposed. It simply consists of a reconfigurable in-/out-of-phase filtering power divider (RFPD) and a 90° hybrid coupler. By controlling the varactors in the RFPD without any switch component, the proposed 3-port feeding network offers continuous reconfigurable filtering responses with four switchable output patterns including: equal power dividing with phase difference of negative or positive 90°, single-ended output at either output port. With this proposed feeding network connecting to a regular dual-polarized antenna, the resulted antenna system can easily realize reconfigurable polarization of vertical polarization (V-LP), horizontal polarization(H-LP), left-handed circularly polarization (LHCP) and right-handed circularly polarization (RHCP), in addition to its reconfigurable filtering responses. A prototype using microstrip technology is designed, fabricated and measured to demonstrate the proposed technique. Good agreement between simulated and measured results is obtained. The measured results show that the feeding network covers a frequency range of 1.05-1.25 GHz, and the error of phase difference and amplitude imbalance are less than 5° and 0.5 dB, respectively. The resulted antenna beams can be freely switched in four polarization states with good performance.

High-Isolation Dual-Polarized Leaky-Wave Antenna With Fixed Beam for Full-Duplex Millimeter-Wave Applications

In this article, a high-isolation dual-polarized leaky-wave antenna (LWA) with a fixed beam is proposed for full-duplex millimeter-wave (mm-wave) applications. The proposed antenna consists of a dual-polarized LWA array and an orthogonally differential feeding network. The proposed dual-polarized LWA array is developed based on the proposed LWA unit cell, which is suitable for differential feed, and the open stopband is eliminated. The proposed feeding network provides two pairs of orthogonally differential excitation for the LWA array to realize the fixed beam with orthogonal polarization in boresight direction; the high interport isolation is implemented as well. The prototype for demonstration purposes is fabricated and measured. The measured results show that the proposed antenna exhibits an operating band from 27.6 to 29.5 GHz with a maximum gain of up to 24 dBi. Furthermore, the measured interport isolation is higher than 51 dB within the operating band, where the maximum isolation is up to 60 dB. The measured cross-polarization levels are also very low, less than −27 dB. The proposed antenna features high gain, high interport isolation, and good co-/cross-polarization isolation, achieving a good Tx/Rx separation for the in-band full-duplex applications at mm-wave frequencies.

Circularly polarized antenna array based on hybrid couplers for 5G devices

This paper depicts a wideband circularly polarized (CP) antenna for 5G devices. The antenna array has a 3D structure including four simple printed dipole elements with directional radiations, high gain, and high efficiency. It achieves a CP by using the sequential rotation (SR) feeding based on 90°-3dB hybrid couplers in the proposed feeding network. The antenna array bandwidth is wide, 26.7%, with an operating frequency band from 3.35 GHz to 4.35 GHz. The antenna achieves a high peak gain of 10.73 dBi and high efficiency of 93.75%. Besides, the antenna gain is stable over the operating bandwidth (BW). At the centre operating frequency of 3.75 GHz, the angle of circular polarization is 51°. The antenna is designed and fabricated on the Rogers 4003 C substrate. The measured S11 is well matching with the simulation results. With the above characteristics, the proposed antenna can be a suitable candidate for 5G devices.

Wideband Octagonal Dual Circularly Polarized Sub-array Antenna for Ku-Satellite Systems

In this paper the analysis and design of a dual circularly polarized 4×4 antenna array operating in Ku-band are discussed with emphasis on its sequential feeding network. The dual circular polarization is achieved by feeding a stacked octagonal patches with a wideband branch line coupler. The proposed 4×4 antenna array is based on two separate sequential feeding networks for LH and RH circular polarizations. The advantage of the proposed feeding network is that it is implemented on a single layer. Simulation results by using both HFSS and CST are presented for comparison. In addition, experimental verifications are presented.

Four-Node Antenna Feeding Network for Interfacing With Differential Front-End Electronics

A novel concept of a differential feeding network for four-node antenna/antenna arrays is proposed. The network is constructed out of a four-strip coupled-line directional coupler operating in a mixed differential-nodal mode enabling direct interfacing of differential front-ends with single-ended antennas. It is shown, that such a configuration provides at the outputs of the proposed feeding network four signals, which are equal in amplitude and with phase progression of 90°. Thus, such a network can be utilized for generating either dual-circular polarization from a 2× 2 antenna array or can constitute simultaneously two out-of-phase power dividers and a directional coupler resulting in a two-beam antenna array in one cut-plane and two-element array in the other one. The dual-circular excitation is of particular interest for modern-day transceivers as it enables polarization-division-duplex communication. The presented concept is confirmed by measurements of two different antenna arrays operating at 2.5 GHz frequency range featuring dual-circular and dual-beam properties, respectively.

N-Way Planar Balanced-to-Balanced Series Feeding Network for Balanced Frequency-Scanning Phased Array

In this article, a novel series feeding network as an N-way balanced-to-balanced structure for balanced frequency-scanning phased array is proposed. Design requirements of the N-way balanced-to-balanced series feeding (BBSF) network are extracted and mixed-mode S-parameters are expressed by using matrix transformation. Designing the BBSF network without using baluns at input and output paths of the network results in the compact and low-loss feeding network, while maintaining the common-mode suppression feature. Furthermore, to have a planar BBSF network, microstrip crossovers are utilized to avoid the use of multilayer PCB design, resulting in the elegant transfer of intersecting RF signals. To validate the proposed structure, a three-way BBSF network is fabricated which shows acceptable mixed-mode measurement results. Also, to demonstrate the performance of the proposed structure, a balanced frequency-scanning phased array is designed employing the proposed feeding network. The measurement results of the fabricated array show that the differential return loss and the differential mode to common mode conversions are better than 20 and 30 dB at 5.85 GHz, respectively. Meanwhile, the fabricated array shows a wide-range beam-scanning capability over its frequency band.

Wideband sequential feeding network for Ku‐band dual circularly polarized 4 × 4 antenna array

In this article the analysis and design of a dual circularly polarized 4 × 4 antenna array operating in Ku band are discussed with emphasis on its sequential feeding network. The proposed antenna element is composed of stacked circular patches fed by a branch line coupler to introduce dual circular polarization. These antenna elements are arranged into 2 × 2 sequential fed antenna arrays with two separate sequential feeding networks for LH and RH circular polarizations. These 2 × 2 sequential fed antenna arrays are arranged to compose the proposed 4 × 4 antenna array. The proposed feeding network is implements on a single layer. Due to the coupling between the lines of the complete feeding network, matching and axial ratio of the complete antenna are degraded. Matching stubs at appropriate points on the complete feeding network are used to adjust the total performance of the designed 4 × 4 antenna array. Simulation results by using both HFSS and CST are presented for comparison. In addition, experimental verifications are presented.

Lightweight Printed Dipole Antenna Array With 3 × 2 Beamforming Network for Wide UAV Communication Coverage

In this paper, a lightweight printed dipole antenna array with 3 × 2 beamforming network for wide unmanned aerial vehicle (UAV) communication coverage is presented. The proposed antenna consists of an upper substrate, a lower substrate, and two supports with a microstrip feeding. The upper substrate has a two-element printed dipole antenna array, and the lower substrate includes a beamforming feeding circuit and a ground plane as a reflector of the proposed antenna array for gain improvement. For wide beam coverage, the proposed feeding network consists of three RF switches, one Wilkinson power divider, and one 90° hybrid coupler, and generates the wide beam using one broadside beam and two end-fire beams. Measured impedance bandwidth, peak gain, and half-power beamwidth (HPBW) of the proposed array operated from 5.03 to 5.15 GHz are approximately 2 GHz, 4.3 dBi, and 155°, respectively.

Ultra‐compact 3 × 3 Nolen matrix beamforming network

A novel compact 3 × 3 Nolen matrix beamforming network is proposed in this study. Unlike the Butler matrix and Blass matrix, in this design, the proposed feeding network only requires couplers and phase shifters and removes crossovers and load terminations. To minimise the size, the authors’ proposed novel Nolen matrix is realised by lumped-element couplers. First, the design theory for 3 × 3 Nolen matrix is derived, and the associated pyramidal layout consisting of three couplers with two coupling ratios and three-phase shifters is proposed. Based on the determined topology, the S-parameters of the proposed feeding network and desired coupling ratios are derived, and it is found that the phase differences among the output ports are dependent on the characteristics of the couplers. Then, each coupler is realised by using lumped-elements (including inductors and capacitors) in the proposed topologies, where the values of the elements are obtained by analysing the ABCD-matrix of the branch lines in the couplers. To verify the proposed concept, an experimental prototype working at 1 GHz is fabricated and tested. The simulation and measurement results agree well with each other, and an ultra-compact size 0.17λ × 0.06λ is implemented to achieve more than 90% size reduction comparing with the previous designs.

A 140 GHz High-Efficiency Slotted Waveguide Antenna Using a Low-Loss Feeding Network

This letter proposes a 140 GHz high-efficiency slotted waveguide antenna with a low-loss feeding network. The feeding network provides the same-magnitude but alternating-phase excitations for the slotted parallel-plate waveguide (PPW) array. The alternating-phase excitations are used to implement virtual electric walls (VEWs) for replacing the physical metal walls. Hence, the antenna efficiency is improved significantly. To verify the proposed method, an 8 × 8 slot array with the proposed feeding network is designed and fabricated, which has a fractional bandwidth of 10.17%, i.e., from 132 to 146.15 GHz. Experimental results show that the radiation and aperture efficiency of the prototype can be as high as 93.4% and 73.2%, respectively. The measured antenna has a peak radiation gain of 24.59 dBi at 137.5 GHz and a flat in-band gain. The proposed antenna provides a promising solution to develop high-efficiency upper millimeter-wave and sub-terahertz (THz) applications.

Dual-Sense Circular Polarization Antenna Based on Reconfigurable Orthogonal Network

A novel circular polarization (CP) reconfigurable microstrip antenna is presented. The CP reconfigurable antenna is divided into three layers, composed of an annular radiating patch, ring slot, and reconfigurable orthogonal network (RON). The designed antenna is fed by dual vertical branches at the output port of the RON. By adjusting the bias voltage of the PIN switch loaded on the reconfigurable orthogonal network, the output phase can be changed, which means that the polarization direction of CP antenna is switchable. Simulation results show that the proposed feeding network provides constant phase difference and lower insertion loss for both states in the operating frequency band, thereby achieving good match and axial ratio characteristics either LHCP or RHCP state. Measured results show that the proposed antenna exhibits operational bandwidth of 1.2% with axial ratio below 3 dB and return loss above 10 dB in both polarized states. Good agreement between simulated and measured results is obtained.

A Novel 2-D $3\times3$ Nolen Matrix for 2-D Beamforming Applications

In this paper, a 2-D beamforming phased array using a novel 2-D Nolen matrix network is presented. The Nolen matrix is a novel antenna feeding network composed of only couplers with dedicated coupling ratios and phase shifters. It does not require crossover and load termination compared to other networks based on Butler and Blass matrix. To be specific, the closed-form equations are derived first for uniplanar single $3 \times 3$ Nolen matrix, which is composed of three couplers and three phase delay lines. Most importantly, it is found that the proposed Nolen matrix can employ couplers with arbitrary phase differences to achieve relatively flexible progressive phase delays across the radiating elements, presenting a high degree of freedom on circuit topology and beamforming performance. Then, a 2-D antenna feeding network is designed by stacking and cascading six $3 \times 3$ Nolen matrices, and a 2-D patch antenna array is integrated with the proposed feeding network to generate nine radiation beams with unique directions on azimuth and elevation planes, realizing the 2-D beamforming function. To verify the proposed design concept, a prototype of 2-D beamforming phased array operating at 5.8 GHz is designed, fabricated, and measured, and the experimental results agree well with simulation and theoretical analysis.

Circular feeding network for circular polarisation reconfigurable antennas

In this Letter, a symmetric feeding network is proposed for constructing circular polarisation (CP) reconfigurable antennas. The proposed feeding network is based on the sequentially rotated serial feed with three outputs, which has been employed for circularly polarised antennas, extensively. The reconfigurability is obtained by using an additional line and bias circuits. A circular patch antenna is stacked on the proposed feeding network, designed for the frequency band 2-2.3 GHz, to obtain a wideband CP reconfigurable antenna. The performance of the proposed reconfigurable antenna is validated using simulation and measurement results.

A Quadruple-Polarization Reconfigurable Feeding Network for UAV RF Sensing Antenna

A quadruple-polarization reconfigurable feeding network for an unmanned aerial vehicle (UAV) RF sensing antenna operating at 915 MHz is presented. It consists of one single-pole four-throw (SP4T) switch, one 90° hybrid coupler, two 180° hybrid couplers, and two single-pole double-throw (SPDT) switches. By controlling the SP4T and SPDT switches, quadruple polarizations with two linear polarizations (vertical and horizontal) and two circular polarizations (right-hand and left-hand) were obtained. The proposed reconfigurable feeding network with quadruple polarization modes in the 902–928-MHz range has an insertion loss of approximately 2.5 dB including switch loss, and it achieves amplitude and phase variations of up to approximately 0.5 dB without divided power or switch loss, and 3°, respectively. Using the proposed feeding network, a circular low-profile UAV RF sensing antenna with quadruple polarizations was designed. Its electrical size, 10-dB impedance bandwidths, and a peak gain are approximately $0.57\lambda _{0} \times 0.57\lambda _{0} \times 0.08\lambda _{0}$ at 915 MHz, 16%, and 6 dBi(c), respectively.

Miniaturised multi‐beam‐controlled circular eight‐port beamforming network for long‐range UHF RFID hemispheric coverage

In this paper, a miniaturised multi-beam-controlled circular eight-port beamforming network for long-range ultra-high-frequency radio-frequency identification (UHF RFID) hemispheric beam-coverage systems (e.g. unmanned aircraft systems) is proposed. For multi-beam control and compact implementation, the proposed eight-port feeding network consists of an integrated beam-control block with a two-stage RF switch block, 12 quadrature hybrid couplers, and 12 90° phase shifters, and was designed and fabricated on a circular three-layer 1.2 mm FR-4 substrate. The diameter of the fabricated network is ~0.47 λ 0 at 915 MHz. The measured maximum insertion loss, and amplitude and phase imbalances of the fabricated network at the authorised UHF RFID frequency band (902-928 MHz) are ~4.5 dB, ± 1.3 dB, and ± 17.5°, respectively. An eight-element dipole antenna array with the proposed feeding network shows feasibility of hemispheric beam coverage by generating multiple beams simultaneously regarding port controls. Beam coverages, where the simulated realised gain is higher than 3 dBi, are ~180° and 130° at φ = 90 and 0°, respectively.

Compact Sequential Feeding Network With Quadruple Output Ports and Its Application for Wideband Circularly Polarized Antenna

A compact single-layer series-type feeding network is proposed by utilizing two dual-band frequency-independent couplers in this paper. The overall size of the feeding network is further reduced by meandering the transmission lines. The proposed feeding network is quite suitable in the design of wideband circularly polarized antenna due to its wideband performance, identical amplitude and flat 90° successive shifts between two arbitrary adjacent ports. Based this, a wideband circularly polarized antenna for satellite application (L band and S band) is presented, fabricated, and measured employing the proposed feeding network. Four feeding strips are introduced to enhance the axial ratio (AR) bandwidth of the proposed antenna. The simulated AR bandwidth extends from 14.7% to 34.5% by loading the four feeding strips. The measured results indicate that the proposed antenna has numerous advantages, such as low-cost, low-profile ( $0.07\lambda _{0}$ ), wideband, high gain, wide AR bandwidth, and excellent circularly polarized feature. Note that the measurements agree reasonably well with the simulations.

A Feeding Network with Chebyshev Distribution for Designing Low Side-lobe Level Antenna Arrays

This paper proposes a feeding networking to gain low sidelobe levels for microstrip linear antenna arrays. The procedure to design a feeding network using Chebyshev weighting method will be proposed and presented. As a demonstration, a feeding network for 8×1 elements linear array with Chebyshev distribution weights (preset sidelobe level of -25 dB) has been designed. An unequal T-junction power divider has been applied in designing the feeding network to guarantee the output powers the same as Chebyshev weights. The obtained results of the amplitudes at each output port have been validated with theory data. The phases of output signals are almost equal at all ports. The proposed feeding network, therefore, can be a good candidate for constructing a low sidelobe level linear array antenna.