A broadband phase shifter (PS) with a constant phase based on a negative group delay (NGD) microwave circuit is proposed. The presented broadband PS is composed of distributed microstrip lines and two resistors, which is based on the positive group delay compensation principle. By tuning the electrical length of the phase shift transmission line, the constant phase can be obtained in the range of -360° ~ 0°. For verification, three broadband PSs with the phase shift of -90°, -180°, and -270° (90°) are designed, fabricated, and measured at the center frequency of 1.0 GHz. The measurements show that the -90° PS can achieve a constant phase of -90°±3.0° with a fractional bandwidth (FBW) of 73.1%; the -180° PS can achieve a constant phase of -180°±5.0° with an FBW of 51.1%; and the -270° PS can achieve a constant phase of -270°±4.0° with an FBW of 40.4%. Besides, the return loss is greater than 13.6 dB in the flat-phase bands.
In this paper, an AgileDARN (Agile Dual Auroral Radar Network) radar echo classification method based on support vector machine is proposed. AgileDARN radar echo includes ionospheric backscattering echo, meteor echo, noise interference, etc. With the continuous operation of AgileDARN radar, the amount of data increases rapidly, requiring efficient and reliable classification methods. In order to efficiently classify the echoes of AgileDARN radar, this paper proposes an echo classification method based on support vector machine. By analyzing the characteristics of the autocorrelation function (ACF) of the sampled data and extracting the features, the support vector machine(SVM) classification method is adopted to classify AgileDARN echo into ionospheric backscattering echo, meteor echo and noise interference. The data analysis shows that the classification accuracy of training data set is more than 99%, and that of test data set is more than 95%. Using this classification model to classify 1800 echo data of AgileDARN radar, the classification accuracy is more than 91% compared with the result of manual interpretation.
In this article, we present the design and production of a miniaturized adjustable coupler with optimized dimensions of 48 mm in length and 31 mm in width. This coupler offers the possibility of covering all phases [0, 45°, 90°, 120° and 180°]. To be able to achieve this, the proposed coupler can be adjusted through the implementation of six SMV2019-079LF diodes which allow shifting from one phase to another. This new flexibility, in terms of phase shifting, can greatly improve the multifunctional use of this small and efficient coupler, in particular, in comparison with previously improved phase shifting couplers which are limited to one or two phases. The high performance and efficiency have been verified by the results obtained by simulation and measurement.
In this article, a miniaturized, dual-polarized corner-fed microstrip antenna is designed and fabricated at 1.43 GHz for Low Earth Orbit (LEO) Satellite applications. The antenna adopts a Complementary Split-Ring Resonator (CSRR)-inspired structure and slotted patch to achieve miniaturization. This reduces the patch size by 39.4%. Meandered impedance-transforming lines are placed for impedance tuning, and its benefit is demonstrated by both simulated and measured S11 curves reaching lower than -20 dB. Feeding at corner increases its isolation to -25 dB over the whole bandwidth of 40 MHz and reaches lower than -33 dB at the resonant frequency. The antenna is fabricated and tested. Measured results are generally in good agreement with simulations.
The uplink and downlink of modern satellite communication systems operate on different frequency bands. A novel dual-band dual circular polarization filter antenna with a single port is proposed in this paper. The dual-band characteristic of the antenna is obtained by exciting stacked patches. The antenna supports right-handed circular polarization (RHCP) at lower frequency band and left-handed circular polarization (LHCP) at higher frequency band, respectively. The feeding network is realized with a strip line, and the antenna can be equivalent to a parallel circuit. If the lower frequency patch works, the higher frequency patch presents high impedance, and vice versa. Therefore, the antenna has excellent filtering performance. The measurements of antenna prototype are in good agreement with the simulation results. The impedance bandwidth is 5.80-6.10 GHz and 9.20-10.64 GHz, and the axial ratio (AR) bandwidth is 40 MHz for lower band and 180 MHz for higher band, respectively. Meanwhile, the radiation pattern is stable in the operation frequency bands.
A compact exponentially tapered balanced antipodal Vivaldi antenna for Phased array systems is proposed in this paper. The proposed design implements slots at the edges to improve impedance bandwidth typically at lower frequencies. The antenna is coupled to a 50 Ω microstrip line between the signal conductors of the middle layer and ground plane. A detailed parametric analysis has been carried out to determine the optimized dimensions and to achieve desired antenna performance. A prototype of the antenna (56×28×1.6 mm3) was fabricated and measured to validate the simulation results. It is revealed that the antenna has a wide impedance bandwidth of 120% over 5-20 GHz and measured gain of the antenna increases from 2.6 dB to 8.0 dB in the whole operational frequency band. The small aperture width which is typically 28 mm is the attractive feature of the proposed design. Therefore, compact size, high gain, ultrawide bandwidth, and directional radiation characteristics of the proposed design may be suitable for advance radar systems.
In this work, a substrate integrated waveguide slot array filtering antenna for dual band applications is presented. This novel design performs the functions of both a filter and an antenna simultaneously. The main intention of this work is to design a circuit that separates the frequencies in a dual band operation. The antenna is designed as an integration of two parts; the upper part operates at 10.2 GHz while the lower part operates at 16.4 GHz. In each part, an array of five longitudinal slots is incorporated, as well as a SIW antenna with complementary split ring resonators that operate as a band pass filter at the front end. Each slot array antenna is designed for a specific frequency band, and its function depends upon its preceding band pass filter. The two band pass filters allow only signals from the frequency bands for which they are designed, to their corresponding slot array antennas. This technique, along with properly spaced metal vias of the SIW antenna, prevents any leakage and hence reduces interference in dual band operation. Both the band pass filter and the antenna can be built on the same planar board. The antenna is fed through a microstrip to SIW taper transition. CST Microwave Studio software is used for optimization and simulation of the structure. The antenna was built on an RT Duroid 5880 and tested to investigate practical validation. The antenna has a bandwidth of 1.9 GHz, from 9.2 GHz to 11.1 GHz in the X-band, and 2.2 GHz, from 15.6 GHz to 16.9 GHz in the Ku band. The gain pattern is unidirectional in nature and has low side lobe levels of -24 dB and -21 dB at resonant frequencies. A noticeable difference that is greater than 20 dB between co-polarization and cross-polarization is observed. The dimensions of the antenna are 56 mm x 32 mm x 0.508 mm. There is an excellent similarity between the simulated and measured results.
To further improve the sensitivity of liquid dielectric constant measurements, a cylindrical container-type dielectric constant sensor is proposed in this paper. The container of the sensor consists of a substrate integrated waveguide (SIW) loaded with complementary split ring resonators (CSRRs) and a microstrip line. In order to solve the problem that the electric field distribution of the traditional container liquid dielectric constant sensor is only in a single plane, which cannot obtain good resonance characteristics, the sidewall of the sensor container is surrounded by a flexible material loaded with CSRR-SIW. Higher sensitivity can be obtained from measuring dielectric constant with more concentrated electric field distribution. The simulation results show that when the permittivity of the liquid under test (LUT) changes from 1 to 10, the resonance frequency of the sensor changes from 4.50 GHz to 2.94 GHz. The resonance frequency shift with unit dielectric constant greater than 150 MHz is realized. Using the relationship between the fitting permittivity and resonance frequency, the measurement of the known liquid permittivity of the standard sample is carried out. The test results show that the relative error is less than 2%, and the test sensitivity is 3.85%.
This paper proposes a dual-band circularly polarized antenna with ``X'' parasitic structures applied in the Beidou satellite navigation system. The innovation of this paper is to introduce the radome with ``X'' parasitic structures to broaden the beam width of the L-band and to improve the low-elevation gain of the antenna. Furthermore, high dielectric constant materials are used to realize the miniaturization and embedded application of the antenna. The measured results show that the VSWR of the L-band is 1.09 at 1616 MHz, and the VSWR bandwidth (VSWR<2) is 45 MHz (1589 MHz-1634 MHz). The VSWR of S-band antenna is 1.24 at 2492 MHz, and the VSWR bandwidth (VSWR<2) is 54 MHz (2471 MHz-2525 MHz). By adding the designed radome, the 20-degree elevation gain of the L-band is increased by 3.755 dBic. The measured results show that the gain variation at 20-degree elevations of the antenna at 1616 MHz and 2492 MHz are 4.981 dBic and 3.7 dBic, respectively. Moreover, the beam widths of the antenna at 1616 MHz and 2492 MHz are 130 degrees and 104 degrees, respectively. The antenna has an improved gain and a good roundness at low elevation angles, thus providing a favorable choice for navigation antenna solutions.
A dual-polarized wide-angle scanning array antenna is proposed in this paper. The proposed antenna array consists of sixteen elements with the working band from 9.5 to 10.5 GHz. A microstrip patch fed from two orthogonal directions is applied to achieve dual-polarization. In order to obtain good impedance matching and wide bandwidth of the antenna, capacitive coupling feeding is adopted. The measured results show that the proposed array can cover a wide scanning range of ±58°. The polarization isolations of antenna are higher than 17 dB. The isolations between receiving sub-array and transmitting sub-array are higher than 22.3 dB. The proposed array antenna is suitable for Van Atta applications.
In this paper, a novel tunable LC bandpass filter (BPF) based on LC magnetic-dominant mixed coupling is proposed. The design equations for the coupling coefficient and resonating frequency are given. The magnetic dominant coupling region and electric dominant coupling region are studied. The magnetic-dominant mixed coupling is used to compensate the bandwidth of the tunable filter, so that the tunable filter with constant absolute bandwidth can be obtained. The filter is designed, simulated and measured, and the measurement matches the simulation very well. The measurement shows that the central frequency tuning range is from 72 MHz to 222 MHz with -3dB bandwidth of 16.5±3.5 MHz.
Although the design of multiband band-pass filters (MBPFs) has been thoroughly studied in the literature, the synthesis of high-order and multiple pass-band filters with controllable transmission zeros (TZs) and high band-to-band isolation is hardly feasible. In this paper, we present a novel design strategy to cope with this issue. Adopting a star-like topology, the proposed design method is based on the parallel association of N-1 band-stop stepped-impedance stubs to form an N pass-bands resonator. We show that such a simple design principle allows the accurate control of TZs positions. The principle and theory of these associated band-stop resonators (ABSRs) based filter are exposed, and their efficiency is shown through the synthesis, design, simulation, and measurement of quad-band and quint-band band-pass filters. Very good in-band filter performance and very high band-to-band isolation are achieved for both filters without the need for complex optimization process. These results make the ABSRs an attractive solution to achieve multiple band responses with advanced specifications.
This paper proposes a new method to produce and reconfigure transmission zero(s) (TZ(s)). The TZs are constructed by using lumped elements in series with dielectric resonators, which is different from conventional methods such as introducing a cross coupling between nonadjacent resonators and mixed coupling between adjacent resonators. The proposed filter consists of two dielectric resonators, a capacitor, an inductor, two PIN diodes, etc. Two PIN diodes are used as switches to realize reconfigurable TZ(s). The mechanism is analyzed theoretically. An equivalent schematic diagram is simulated by using ADS software. The simulated results show that the structure can realize four response states, i.e., no TZ in the stopband, one TZ in the lower stopband, one TZ in the upper stopband, and two TZs in both sides of the stopband of the filter, respectively. The dielectric resonators (DRs) were made of dielectric ceramics with high dielectric constant of about 92. The filter was fabricated on a dielectric substrate and measured by using a vector network analyzer and double regulated DC power supply.
In the paper, a compact broadband 3×3 Nolen matrix with flatten output ports phase differences is presented. By using two types of three-branch quadrature couplers, wideband impedance matching and flatten output ports amplitudes are obtained. Besides, imbalanced output ports phase differences are compensated by inserting two differential phase shifters between the couplers. Design equations for the proposed structure are derived, and influences of the two differential phase shifters on the phase differences of the Nolen matrix are investigated. To verify the effectiveness of the structure, a prototype operating at 5.8 GHz is fabricated and measured. Measurement results agree well with the simulated ones. Fractional bandwidths (FBWs) of 31.21% and 45.17% are obtained for 15-dB return loss and 15-dB isolation. Moreover, under the criterions of amplitude imbalance < 1 dB and phase difference < 5°, the measured FBWs are more than 23.20% and 23.96%, respectively.
This paper proposes a novel coaxial magnetic gear (CMG) with eccentric permanent magnet structure and unequal Halbach arrays for achieving sinusoidal air-gap flux density and high output torque. The proposed model has a high temperature superconducting (HTS) bulks to replace the epoxy resin in the conventional stationary ring. According to the Meissner effect and one-sided field, the HTS bulks could enhance the modulation effect. The permanent magnets (PMs) on the inner and outer rotors are distributed in Halbach array, in which the PMs are arranged regularly on the outer rotor, and the inner rotor is an eccentric structure. So the inner nonuniform air gap can be obtained. The proposed model with the pole pairs of 4 and 17 for the inner and outer rotors is established, and using finite element analysis (FEA) a calculated torque is up to 350.8 N.m. It is 2.16 times of the torque of conventional CMG.
In this letter, a 120-220 GHz fourth-harmonic mixer based on Schottky diodes is presented. To broaden the bandwidth, a novel diplexer is proposed, which consists of two low-pass filters (LPFs) and a beam lead capacitor. Thanks to the high-pass characteristic of capacitor, the 30-55 GHz local oscillator (LO) signal is efficiently pumped to the diodes. Moreover, a two-level hammer-head configuration is adopted at the LO LPF to block the 120-220 GHz radio frequency (RF) signal. Finally, a 120-220 GHz fourth-harmonic mixer is fabricated and measured. The measurement results show that the conversion loss ranges from 12 to 18 dB within a wide RF relative bandwidth of 58.8%.
This letter proposes a novel analysis and design method of a continuously adjustable bandpass combline filter. It investigates the feedline design specifications and introduces an external quality factor (Qext) tuning structure to achieve a constant fractional bandwidth over 60% tuning bandwidth. The design approach allows to determine the optimum feedline structure for the filter andis verified by full-wave simulation and measurement. The results show a constant fractional bandwidth of 4.5% over the entire operating frequency range between 225-400 MHz.
This paper proposes a 2D semi-analytical electromagnetic model to compute the magnetic field and eddy current generated by a variable current density along a conducting billet of induction heater. The developed model is based on the combination of the discretization method and the Biot-Savart theory. Firstly, the analytical solutions of the vector potential and the magnetic field are calculated in all elements discretized cylindrical geometry using the law of Biot-Savart. Then, the total field is determined by the contribution of the superposition of each element of the discretized geometry. The eddy currents are computed using the Ampere law, and it also allows us to determine the exact resulting heating power density, which is the heat source of the thermal problem. The results obtained are in agreement with those obtained using finite element method. Therefore, the developed magnetic model presents a fast and accurate tool for the design of induction heating devices.
A W-band high isolation single-balanced mixer using a 0.1-um GaN high-electron mobility transistor process is proposed in this paper. The diode is biased near the threshold voltage to reduce drive level, and the needed LO power is only 3 dBm. Moreover, the reasonable diode layout and phase compensation structure are used in the proposed mixer to enhance the LO-to-RF isolation. The measured results of the proposed mixer demonstrate a single-sideband conversion loss of 9-10.6 dB and a LO-RF isolation of 40 dB from 75 to 110 GHz with 7 dBm LO power. Moreover, a DC-to-18 GHz IF bandwidth is achieved with the LO frequency fixed at 110 GHz. The 1 dB compression point of the proposed mixer is 11 dBm with 16 dBm LO power. The measurement results indicate that GaN mixer has great potential for W-band transceiver system applications.
Implementation of a broadband Ruthroff-type transmission line transformer balun with a 1:2 step-up impedance transformation ratio is presented in this letter. The proposed Transmission Line Transformer (TLT) balun was investigated with broadside-coupled lines using three stacked microstrip lines. The proposed balun was formed by cascading one section of modified Ruthroff-type 2:1 unbalanced-to-unbalanced TLT with one section of Ruthroff-type 1:4 TLT balun in series. The achieved fractional bandwidth of the balun is 192.17% over the frequency range from 1.2 to 6.6 GHz, which covers the IEEE 802.11 a/b/g WLAN, WiMAX applications. The measured amplitude and phase imbalances are less than 1 dB and less than 4.51˚, respectively at this frequency range.