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The distribution of lubricant flow field inside the two‐stage transmission reducer is very complicated during splash lubrication, which is difficult to be visually simulated and analysed using traditional finite element methods (FEM). There are many problems in model processing, algorithm selection, mesh division, and computational workload. Through sufficient investigation and experimental validation based on literature, the moving particle semi‐implicit (MPS) method is proposed to study the splash lubrication characteristics of a rail vehicle reducer. Through this method, the visual simulation calculation of multiple working conditions of reducer with complex structure is realised, and the unreasonable structure of the gearbox body is optimised. The model of oil supply demand in the Hertz contact zone of gear transmission is established, and the time‐domain variation law of oil particles number in the contact zone and oil supply state are analysed. It is found that the optimised reducer model can meet the demand of oil supply under the four typical working conditions of the rail vehicle. The higher the initial oil volume is, the more sufficient the oil supply is. Compared with the working temperature conditions of 20 and 80 °C, the lubrication effect is better at 40 and 60 °C. By analysing the power loss proportion of each gear, it is found that the sum of power loss of gear 1 and gear 2 is dominant under different working conditions, reaching 76%–99.5% of the total churning power losses. [ABSTRACT FROM AUTHOR]

In this article, an efficient over-the-air (OTA) calibration and pattern estimation method under the midfield (MF) condition for the fifth-generation (5G) millimeter-wave (mmWave) large-scale arrays is proposed. A new transformation and revision algorithm is developed to calibrate the antenna array fast and accurate. Meanwhile, the time consumed in the accurate beamforming pattern estimation is reduced significantly. The proposed method requires a much smaller size anechoic chamber, a fixed probe antenna, and a vector network analyzer (VNA). The effectiveness is proven with the detailed theoretical analysis and experimented with a 64-element phased array in the 26 GHz band. The calibrated root-mean-square (rms) errors of the phase and magnitude are about 1.8°/0.4 dB. In addition, the proposed calibration and pattern estimation method is tremendously cost-effective and time-saving with similar accuracy as the far-field test method. [ABSTRACT FROM AUTHOR]

In this communication, a dual polarized (DP) stacked patch filtenna (filtering antenna) with a wide stopband is developed for tile array applications. The bandpass filtering property is realized by improving the feeding network and patch without adding extra bandpass circuit or size. An elaborate feeding structure with complementary pair of a short-circuited stub and an open-circuited stub (CSSOS) is developed, which generates two transmission nulls effectively enhancing the selectivity and suppressing the harmonic. Moreover, CSSOS has a small size and broadens the impedance bandwidth apparently by introducing an in-band resonance. By properly etching four U-shaped slots on the driven patch, a radiation null in the upper stopband is also generated. The nulls generated by the two approaches can be adjusted independently in wide ranges. For further harmonic suppression, bandstop striplines (BSSs) with ultralow insertion loss are developed. Measured results show that the filtenna performs a wide operating band (3.10–3.95 GHz) and a wide stopband up to 8 GHz with a rejection level higher than 16 dB. Besides, a 32-element tile phased array employing the filtennas is also fabricated and measured. A compact configuration, high selectivity, and good beam steering capacity are exhibited. [ABSTRACT FROM AUTHOR]

A tri‐band shared‐aperture antenna operating at both the sub‐6G and millimeter‐wave bands is proposed for 5G/B5G communications. It is small in size owing to the structure sharing technique. Four longitudinal slots are etched on the top of a substrate integrated waveguide (SIW), forming a millimeter‐wave antenna operating at 28 GHz. Meanwhile, the outer conductor of the entire SIW is used to realize a monopole antenna that can operate at 3.5 and 4.9 GHz, respectively. The structure reuse efficiency of the monopole radiating area is about 80%. A tri‐band microstrip line to SIW transition is proposed to excite different transmission modes in the sub‐6G and millimeter‐wave bands, thus, realizing the proposed large frequency ratio tri‐band antenna with a single shared port. A prototype of the proposed antenna is fabricated and measured, and the measured results agree well with the simulated ones, validating the correctness of this design. [ABSTRACT FROM AUTHOR]

A kind of novel general multiband digital predistortion (DPD) model is proposed for the linearization of the multifrequency transmitters. By the theoretical analysis, we extend the existing instantaneous sample indexed magnitude-selective affine (IMSA) function-based model to multidimensional cases, which includes the 2-D-IMSA model and the 3-D-IMSA model for concurrent dual-band and triband scenarios, respectively. The core of the new models is to use the multidimensional IMSA function to replace the complex basis function of the classic multiband model through the method of segmentation and approximation. After segmentation, the proposed models have a simple linear structure in each small area, which greatly reduces the model complexity. Experiments show that the proposed models can give similar normalized mean square error and DPD performance in comparison with existing classic models when a power amplifier is excited by two 20-MHz signals in the concurrent dual-band scenario and by three 20-MHz signals in the concurrent triband scenario. [ABSTRACT FROM AUTHOR]

The rapid detection and accurate positioning of bolster spring with complex geometric features in cluttered background is highly important for the grasping task of bolster spring in overhauling workshop. To achieve a better trade-off among positioning accuracy, running time and model size, two MobileNetv3 and GhostNet-based modified YOLOv3 (MGBM-YOLO) models are proposed in this paper: MGBM-YOLO-Large and MGBM-YOLO-Small, which are applied to the robotic grasping system of bolster spring based on image-based visual servoing (IBVS). The proposed MGBM-YOLO models are trained and evaluated on Pascal VOC2007 and Pascal VOC2012 datasets. The results show that compared with the original YOLOv3 model based on Darknet53, the sizes of the proposed Large and Small models are reduced by 59% and 66% respectively, and the model parameters are reduced by 63% and 66% respectively. The detection speed is 4× and 5.5× faster respectively when the difference of mAP is small. To improve the convergence speed of IBVS system, an online depth estimation method based on the area feature of detection bounding box of bolster spring is proposed. The comparative experiments of visual servoing grasping are conducted on the robotic grasping platform of bolster spring. The experimental results show that the two MGBM-YOLO detection models proposed in this paper can meet the requirements of fast detection and positioning of bolster spring robotic grasping system based on IBVS. The proposed method of feature depth online estimation is of great significance to accelerate the convergence speed of visual servoing system. [ABSTRACT FROM AUTHOR]

In this paper, to address the problem of automatic positioning and grasping of bolster spring with complex geometric features and cluttered background, a novel image-based visual servoing (IBVS) control method based on the corner points features of YOLOv3 object detection bounding box is proposed and applied to the robotic grasping system of bolster spring. The YOLOv3 object detection model is used to detect and position the bolster spring and then based on the corner points features of the bolster spring bounding box, the IBVS controller is designed to drive the end effector of the robot to the desired pose. This method adopts the approach-align-grasp control strategy to achieve the grasping of the bolster spring, which is very robust to the calibration parameter errors of the camera and the robot model. With the help of Robotics and Machine Vision Toolboxes in Matlab, IBVS simulation analysis based on feature points is carried out. The results show that it is reasonable to use the corner points of the object detection bounding box as image features under the initial pose where the image plane is parallel to the object plane. The positioning and grasping experiments are conducted on the robotic grasping platform of bolster spring. The results show that this method is effective for automatic positioning and grasping of bolster spring with complex geometric features and cluttered background, and it has strong robustness to the change of illumination. [ABSTRACT FROM AUTHOR]

In this article, to adapt the various polarization of user terminal, a 1 × 4 C‐band high‐integrated polarization reconfiguration phased array based on phase shifter matrix is presented. The phased array combined with polarization reconfiguration antenna elements exhibits the desired beamforming patterns and achieves beam polarization reconfiguration simultaneously. Based on the technique of the shunted microstrip open‐stub and equalizing resistor, a high‐precision reflection‐type phase shifter with full 360° continuous phase tuning range is designed for this phased array in this article. The prototype of the polarization reconfiguration phased array is designed and fabricated. Measured results show that proposed phased array works at 5.8 GHz and achieves 21.4% (1.2 GHz) impedance bandwidth and 14.3% (800 MHz) 3 dB axial ratio bandwidth. The beam coverage range at 5.8 GHz is more than 64° with 0.2° beam steering resolution. [ABSTRACT FROM AUTHOR]

A band-limited magnitude-selective affine (MSA) function-based model is proposed for digital predistortion (DPD) of broadband power amplifiers (PAs) in 5G millimeter-wave frequency band. The new model is derived from the band-limited canonical piecewise linear function-based model by employing MSA functions, which can obviously reduce the number of multiplication operations and the model complexity. Experimental results show that the proposed model gives better normalized mean square error and DPD performance in comparison with some existing models when a broadband PA is excited by a 5G new radio (NR) signal of 400-MHz bandwidth at 28-GHz band. [ABSTRACT FROM AUTHOR]

An antipodal linearly tapered slot filtenna (ALTSFA) with diverse split-ring resonators (SRRs) is proposed. The ALTSFA is actually an antipodal linearly tapered slot antenna (ALTSA) fed by a substrate integrated waveguide (SIW) whose cutoff characteristic is utilized to obtain a lower band suppression. A broad-coupled complementary SRR (BC-CSRR) and 11 SRRs on the ALTSA are used to achieve an upperband suppression. Hence, filtering function with wide stopbands is achieved without enlarging its size and deteriorating the radiation performance. A prototype of the proposed ALTSFA was fabricated and measured, and a bandwidth ranging from 23.5 to 27.5 GHz, a maximum gain of 10 dBi, and a maximum out-of-band suppression of 20.55 dB are observed, validating its good performance. The proposed ALTSFA can be a promising candidate for compact fifth-generation mobile communications and beyond (5G/B5G) millimeter-wave communication system. [ABSTRACT FROM AUTHOR]

In this letter, a three-dimensional ground coplanar waveguide (3D-GCPW) structure is proposed as a broadband planar transition between the conventional GCPW and substrate integrated coaxial line (SICL). The proposed 3D-GCPW contains a 3-D central conductor constructed by two copper layers which are connected together by metallized blind vias and two side ground planes. Its characteristic impedance is mainly determined by the width of the 3-D central conductor and the gap to the side ground plane; thus, the requirement for machining accuracy of metallized blind vias in 3D-GCPW can be reduced during the machining process. A back-to-back structure of the 3D-GCPW transition is fabricated by a multilayer printed circuit board (PCB) process and measured to validate the good performance. The experimental results show that the proposed 3D-GCPW transition exhibits a reflection coefficient less than −10 dB and an acceptable insertion loss within dc to 42 GHz, making it promising for high-performance multiple-channel transceiver or massive integrated applications. [ABSTRACT FROM AUTHOR]

A high-gain dual-band resonant cavity antenna (RCA) for the fifth-generation (5G) millimeter-wave (MMW) communications is presented in this letter. The proposed antenna provides the high gain and large gain-bandwidth product over the 28 GHz band and the 38 GHz band. The heights of the second- and third-order resonant in the RCA are optimized for dual-band operation. Improvements on the gain and the bandwidth are achieved in both bands when stepped rings are added. The gain is further increased with a circular patch on a partially reflective surface, which is made by a substrate of high permittivity. Finally, a prototype is designed, simulated, and verified through measurement. Good performance is achieved: in the 26.5–28 GHz band, the bandwidth is 5.5% and the peak gain is 20.3 dBi; in the 37.5–39.4 GHz band, the bandwidth is 4.9% and the peak gain is 20.4 dBi. The proposed antenna has the features of low cost and easy fabrication as well. [ABSTRACT FROM AUTHOR]

In this article, novel millimeter-wave (mmWave) filtennas (filtering antennas) are proposed to realize compact size and low insertion loss for 5G applications. It is achieved by employing eighth-mode substrate-integrated waveguide (EMSIW) cavities fully shielded by metallized vias and cover as resonators, which are named as fully shielded EMSIW (FSD-EMSIW) cavities. Interdigital coupling between cavities is introduced in order to obtain higher coupling strength for wideband operation. The proposed single-polarized antenna consists of a feeding stripline, two FSD-EMSIW cavities, and two stacked square patches, generating the four-order filtering antenna response. Furthermore, this design has been extended to realize a dual-polarized filtenna by employing double sets of feeding network. For demonstration, single-/dual-polarized filtenna prototypes were fabricated and measured, the measured results show that the 5G mmWave band (24.25–29.5 GHz) can be covered with average gains of 4.5 dBi. Good bandpass filtering response is also observed. Finally, to validate the proposed idea in array applications, a 16-element filtenna array is designed and measured with good performance. [ABSTRACT FROM AUTHOR]

This letter reports a strategy of full-digital arrays with nonreciprocal transmitting (Tx) and receiving (Rx) beam patterns, for the first time, for 5G/6G wireless communications. The proposed full-digital array contains a smaller number of Rx channels than that of the Tx channels. The unequal number of Tx and Rx channels makes the transmitting and receiving patterns asymmetrical, which would not only release the burden of data processing but also reduce the hardware cost and power consumption of the entire system. Importantly, as compared with conventional large-scale beamforming arrays, the proposed strategy will not deteriorate the range of coverage at an instantaneous time. A 64-element full-digital beamforming array prototype was designed, fabricated, and characterized for a proof-of-concept demonstration. [ABSTRACT FROM AUTHOR]

A novel wideband magnetoelectric (ME) dipole antenna with dual circular polarization and unidirectional radiation is proposed in this letter. The proposed antenna is based on two perpendicular sub-ME dipoles realized by four V-shaped patches and four V-section columns, and each of them is composed of an electric dipole and a magnetic dipole in parallel. Fed by two simple Γ-shaped feeds, 90° phase difference between the electric dipole and the magnetic dipole in each of the sub-ME dipoles is achieved, hence the dual-circularly polarized radiation is generated. Wide impedance bandwidth is obtained in virtue of the two kinds of dipoles being excited simultaneously. The 3 dB axial-ratio (AR) bandwidth is enlarged by optimizing the V-section columns and a circular cavity. Besides, the port isolation is apparently enhanced by adding slits on the patches and elaborating different spacings between each feed and its two-sided columns. Measured results show that the proposed antenna has many appealing properties, such as a unidirectional radiation pattern, an impedance bandwidth (reflection coefficients ≤–10 dB and port isolation ≥ 10 dB) of 51.1% and a 3 dB AR bandwidth of 41.9%. [ABSTRACT FROM AUTHOR]

The integration of the sub-6 GHz and millimeter-wave (mmWave) antennas has become an important issue for the next-generation wireless communication. For the mmWave band, adaptive beam steering is required to solve the path loss and coverage range problems. In this communication, an aperture-sharing technique is developed, so that a four-unit linear 28 GHz array and a 3.5 GHz dipole antenna can be integrated and the same aperture can be shared. The SIW is utilized to enable the integration and maintain the radiation of both antennas, without mutual interference. By adopting a separate feeding network, each mmWave array unit is independently excited, so that a beam steerable in the E-plane can be synthesized in the mmWave band. A prototype is fabricated with a compact size owing to the shared aperture. The measured results show good radiation characteristics and broad 10 dB impedance bandwidth exceeding 20% in both bands. Furthermore, the mmWave beam steering is obtained with a stable gain level. The proposed dual-frequency antenna is suitable for some terminal applications in the next-generation wireless networks. [ABSTRACT FROM AUTHOR]

This paper presents a 3D complex envelope leapfrog alternating‐direction‐implicit finite‐difference time‐domain method. Compared with the previous work, the proposed method costs less computation runtime and memory while maintaining similar accuracy. The stability, accuracy and efficiency of the method are demonstrated by the numerical examples. [ABSTRACT FROM AUTHOR]

This paper presents a 28-GHz low-cost high-precision phased array for fifth-generation millimeter-wave communications. The local oscillator (LO) phase shifting approach and the subharmonic mixing technique are adopted to achieve a full 360° phase-shifting range with up to 10-bit phase resolution and ultralow magnitude deviation. Each phased channel in this array contains a 1-bit 180° intermediate frequency phase shifter and a low-voltage varactor-tuned reflective-type phase shifter at LO path. The LO phase shifting is used to achieve fine phase shifting with low-magnitude variation. The subharmonic mixing enables lower phase range and lower operation frequency at the LO path. The measured root-mean-square phase error and magnitude variation are around 0.3° and 0.1 dB, respectively. The over-the-air phased array calibration and measurement are also performed. The eight-element phased array achieves +/−50° beam scanning angle and fine beam resolution less than 1° step. The gain flatness of the phased array is less than +/−1dB at 1-GHz signal bandwidth. The eight-element array achieves an effective isotropic radiated power of 41 dBm at 10-dB power backoff. The measured error-vector-magnitude is 1.72% with a 500-MHz orthogonal-frequency-division-multiplexing QAM-64 signal. [ABSTRACT FROM AUTHOR]

A 2-D simplified memory polynomial (2D-SMP) model is proposed for concurrent dual-band power amplifiers (PAs) in this letter. The derivation of the proposed model is similar to that of the 2-D modified memory polynomial (2D-MMP) model. The 2D-SMP model consists of an in-band part and a cross-band modulation part without the envelope factors, which exist in the 2D-MMP model. Theoretical analysis shows that it has moderate complexity but higher modeling accuracy than the 2D-MMP model. The simple least square algorithm can be used to extract the model coefficients, and the additional binary search algorithm for the best envelope factor is not needed. The experimental results show that the 2D-SMP model can achieve higher model accuracy and better digital predistortion (DPD) performance than the 2D-MMP model when a dual-band PA is excited by a combined dual-band long-term evolution signal. [ABSTRACT FROM AUTHOR]

A planar circularly polarized substrate integrated waveguide (SIW) stacked patch antenna array consisting of four sequential-rotation (SR) subarrays is presented for $Ka$ -band applications. Antenna element is realized based on a pair of stacked cavities by the combination of a driven patch layer and a parasitic patch layer, which are formed by a shorted square patch and multiple identical stacked square patches, respectively. Each subarray consisting of two pairs of elements, excited by a coplanar waveguide (CPW) network with four metallic vias, is well matched to a novel SIW SR feeding network. A narrow transverse coupling slot, a semiopening resonant cavity, two pairs of inductive vias, and an inductive window are introduced in the SIW-based feeding network to implement functions of phase shifter, impedance matching, and power divider in the two layers. By employing the proposed SR feeding network, the CPW network, and the four subarrays, the excellent performance of the array is realized. To verify the design, a prototype is fabricated and measured, which demonstrates a −10 dB impedance bandwidth of 29.6%, a 3 dB axial ratio bandwidth of 25.4%, and a peak gain of 20.32 dBic. [ABSTRACT FROM AUTHOR]

A 64-channel massive multiple-input multiple-output (MIMO) transceiver with a fully digital beamforming (DBF) architecture for fifth-generation millimeter-wave communications is presented in this paper. The DBF-based massive MIMO transceiver is operated at 28-GHz band with a 500-MHz signal bandwidth and the time division duplex mode. The antenna elements are arranged as a 2-D array, which has 16 columns (horizontal direction) and 4 rows (vertical direction) for a better beamforming resolution in the horizontal plane. To achieve half-wavelength element spacing in the horizontal direction, a new sectorial transceiver array design with a bent substrate-integrated waveguide is proposed. The measured results show that an excellent RF performance is achieved. The system performance is tested with the over-the-air technique to verify the feasibility of the proposed DBF-based massive MIMO transceiver for high data rate millimeter-wave communications. Using the beam-tracking technique and two streams of QAM-64 signals, the proposed millimeter-wave MIMO transceiver can achieve a steady 5.3-Gb/s throughput for a single user in fast mobile environments. In the multiple-user MIMO scenario, by delivering 20 noncoherent data streams to eight four-channel user terminals, it achieves a downlink peak data rate of 50.73 Gb/s with the spectral efficiency of 101.5 b/s/Hz. [ABSTRACT FROM AUTHOR]

A low-profile substrate-integrated waveguide (SIW) cavity-based antenna with conical-beam circularly polarized (CP) radiation is presented. Conical-beam CP radiation is obtained by the combination of a radial current source and a loop current source, which are produced by a shorted monopole patch and an annular array, respectively. The proposed annular array configuration is designed by combining multiple identical customized parasitic patch elements arranged around the monopole. Phase compensatory lines and shorted annular ring slots are introduced in the array to tune phase difference of two current sources and to generate in-phase currents on the elements, respectively. All antenna elements are simultaneously excited within a center-fed SIW cavity. In order to fully picture the operating mechanism, we analyze the wide impedance and axial-ratio (AR) bandwidths based on an equivalent circuit model and an electromagnetic theory. Then, parametric studies are carried out for a detailed design illustration. To verify the design, a prototype has been fabricated and measured, which shows a stable conical-beam radiation and good performance including: a low profile of 0.062\lambda 0 , a 10 dB impedance bandwidth of 20.4%, a 3 dB AR bandwidth of 17%, a maximum gain of 8.25 dBic, and an advantage of large ground compatibility. [ABSTRACT FROM PUBLISHER]

A 2-D-canonical piecewise linear (2-D-CPWL) function-based behavioral model is proposed for concurrent dual-band power amplifiers (PAs) in this letter. The model is derived from the Volterra-based 2-D-modified memory polynomial (2-D-MMP) model by replacing the high-order terms with CPWL and it can provide a lower complexity than the 2-D-MMP model and some existing CPWL-based dual-band models. The least-square algorithm can be used to extract the model coefficients. Experimental results show that the proposed 2-D-CPWL model can achieve nearly the same model accuracy and digital predistortion performance compared with the 2-D-MMP model, when a dual-band PA is excited by a combined dual-band long-term evolution signals. [ABSTRACT FROM AUTHOR]

A low phase noise X-band oscillator based on the bandpass response power divider in single-layer substrate integrated waveguide (SIW) technology is presented in this letter. The power divider is embedded in the SIW filter; therefore, lower insertion loss and more compact area size can be realized than those using the independent design of both components. To achieve better phase noise performance, transmission zeros are introduced by cross coupling through the resonant cavities to increase peak group delay. In addition, by placing external feeding at the center of cavity edge, the second harmonic can be suppressed efficiently. The measured results verify the performance of the proposed bandpass response power divider and show that the phase noise of the oscillator can achieve −143.3 dBc/Hz at 1-MHz offset frequency. [ABSTRACT FROM PUBLISHER]

A band-limited canonical piecewise-linear function (CPWL)-based model is proposed for wideband power amplifiers (PAs). The model has a similar structure of the band-limited dynamic deviation reduction (DDR) Volterra series model but without high-order terms and long finite impulse response filters, which are replaced by CPWL. The model has lower complexity and more flexibility than the band-limited DDR Volterra series model and the model parameters can be estimated by the least-square method. Experimental results show that the proposed model nearly gives the same normalized mean square error and digital predistortion performance as the band-limited Volterra series when a wideband PA is excited by a 5-carrier long-term evolution advanced signal of 100-MHz bandwidth. [ABSTRACT FROM PUBLISHER]

A novel coupling topology of substrate integrated waveguide filter with unequal‐length slots is proposed. This filter consists of two resonators and a pair of unequal‐length slots, which can be considered as two‐stage bypass coupling resonators. There exist two resonant modes (TE101 and TE102) in each resonator. TE101 mode is coupled by the long slot, and TE102 mode is coupled by the short slot, which can achieve two resonant modes couplings between adjacent cavities. This structure uses TE102 mode to design the centre frequency of the passband and regards TE101 mode as spurious response. As a result, this filter leads to three transmission zeros (TZs), two TZs locate above the passband and one TZ is below the passband. The filter is fabricated and measured, the measured results agree well with simulated ones. [ABSTRACT FROM AUTHOR]

A simple technique is developed in this communication to increase the axial ratio (AR) bandwidth and achieve good impedance matching of a single-fed low profile circularly polarized (CP) stacked patch antenna. The proposed antenna is composed of a driven patch layer and a parasitic patch layer. The driven patch layer consists of a truncated main patch, a parasitic patch and a probe feeding structure while the stacked patch layer is comprised of five patches. The proposed antenna combines the attractive features such as low profile, wide impedance and AR bandwidths, high gain as well as easiness of design, manufacture and integration. The antenna operating at 6 GHz band is designed and fabricated on an FR4 substrate and the overall volume is 0.8 \lambda{{0}} \times 0.8 \lambda{{0}} \times 0.09 \lambda{{0}}. Measured results show that the antenna achieves an impedance bandwidth of more than 30% for \vert S11\vert <-15 dB, a 3-dB AR bandwidth of about 20.7%, and a gain level of over 7.9 dBi within the 3-dB AR bandwidth. [ABSTRACT FROM PUBLISHER]

In this article, the development of a high-efficiency power amplifier (PA) with the inverse class-F configuration and a novel 3/4 spiral defected ground structure (DGS) is presented. The proposed DGS structure has improved rejection characteristic and its resonance frequencies are more convenient to adjust than conventional symmetric and asymmetric spiral structure. The electromagnetic-simulated result shows that the proposed circuit has improved harmonic control performance with simplified structure and less return loss than the conventional microstrip harmonic control circuit. The 3/4 spiral harmonics control circuit (HCC) can be modeled by three parallel RLC resonators. Using the proposed structure a high-performance harmonic control circuit is designed for implementing an inverse class-F PA. For comparison, two inverse class-F PAs operating at 2.4 GHz have been implemented by the microstrip HCC and the proposed HCC, respectively. According to the experiment results, the size of the proposed inverse class-F PA is reduced by 20%, the power-added efficiency and the gain are increased by 4.8% and 1.5 dB, respectively. [ABSTRACT FROM PUBLISHER]

A broadband inverted Doherty power amplifier (IDPA) is proposed in this article. To achieve the tradeoff between efficiency and operation bandwidth, an optimized output matching network and offset lines are used to design the load network of the proposed power amplifier (PA). For experimental verification, a conventional IDPA and a class-AB biased balanced PA have been implemented. In addition, a 64-QAM modulated signal with 24-MHz channel bandwidth are applied as excitation. According to experiment results, the proposed Doherty power amplifier can keep power-added efficiency (PAE) higher than 31% from 2.4 to 2.5 GHz with 0.5 dB output-power flatness at 27-dBm output power. The PAE of the proposed PA is 16.4% and 4.2% higher than the balanced PA and the conventional IDPA respectively. In addition, the linearity of the proposed PA is improved effectively. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:636-639, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25785 [ABSTRACT FROM AUTHOR]

This letter introduces a Ku band continuously tunable filter with one parameter. The proposed filter is implemented using substrate integrated waveguide (SIW) technology and has a simple and symmetrical structure. The tunability of the circular resonator is a kind of mechanical tuning, achieved by the different distance between moving copper column and the center of the circular cavity. Location of moving distance has an approximately linear relation with the dominant cavity resonance frequency. The single circular cavity has a tuning range of 12.6–15.0 GHz. The fabricated filter is made up of two cavities and has a frequency tuning ratio percentage of 19.2% compared with the center frequency 13.825 GHz. The insertion loss is between 1.7 and 2.8 dB. [ABSTRACT FROM PUBLISHER]

In [A2] V.I. Arnold introduced three basic invariants St, J[sup +] and J[sup -] of plane curves and proposed some interesting conjectures concerning the extremal value of these invariants on a given set of curves. Partial answers have been obtained by O. Viro and A. N. Shumakovich. We give explicit formulas for these extremal values of sets of plane curves with fixed number of double points and of Whitney index and we determine on which curves these extremal values are attained (Theorems 3-6). Our arguments are based on understanding of the fine structures of generic curves and some surgery operations on curves. [ABSTRACT FROM AUTHOR]

A generalized formula for penetrating boundary conditions is derived based on the Z-transform. The well-known absorbing boundary conditions (ABCs), such as the Mur’s ABC, and Liao’s ABC, can be deduced from the formula. Furthermore, some new ABCs can also be deduced from it. The stability of these ABCs are demonstrated via Von Neurmann method and their validity is verified by numerical examples. [ABSTRACT FROM AUTHOR]

A modified canonical piecewise-linear function (CPWL)-based model is proposed for characterizing wideband power amplifiers. The model has a similar structure of the decomposed vector rotation (DVR) model but without DVR operations, in which the first-order basis function can be replaced by a second-order function by analysis. The model has lower complexity than the DVR model and the model parameter scan be estimated by least-square method. Experimental results show that the proposed model nearly gives the same normalized mean square error performance as the DVR model when a wideband Doherty power amplifier is excited by a 5-carrier long-term evolution advanced (LTE-A) signal of 100 MHz bandwidth. [ABSTRACT FROM PUBLISHER]

In this letter, a systematic method to design compact output matching network of power amplifier (PA) is proposed, which is based on the simplified real frequency technique. The produced network is mainly constructed with commensurate transmission lines, containing cascaded unit elements and open-shunt stubs, as well as a shorted-series stub for dc bias. A GaN PA is designed to verify the method. The measured results show that the PA achieves 68.07%–79.49% drain efficiency and 40.93 to 42.4 dBm output power from 1.7 to 3.1 GHz. Moreover, the fabricated PA has a small size of only 2015 mm^2, due to the compact matching networks. [ABSTRACT FROM PUBLISHER]