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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]

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 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 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]

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]

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]

In this letter, a low phase noise free-running oscillator employing a substrate integrated waveguide (SIW) dual-mode bandpass filter (BPF) is presented. As a frequency stabilization element in the feedback loop, the dual-mode SIW BPF is designed at the oscillation frequency. Due to the transmission zero near the upper passband of the filter, a large group delay peak at the upper passband edge can be achieved to improve the phase noise performance significantly. An X-band oscillator using a SiGe HBT has been designed and experimentally demonstrated at 11.571 GHz. Measured results show that, the phase noise of this proposed oscillator is -135.5~dBc/Hz at 1 MHz offset frequency with a figure of merit (FOM) of -206.2~dBc/Hz. [ABSTRACT FROM PUBLISHER]

A nonlinear filter-based Volterra model with low complexity is proposed for modeling and characterizing wideband power amplifiers. This model has a similar form of a simplified second-order dynamic deviation reduction (DDR)-based Volterra model but without complex square root calculations and high order terms, which are replaced by a first-order nonlinear filter. The model parameters with smaller magnitude distribution range and lower precision in storing and calculation can be estimated by least-square method, and then the model has lower complexity than the second-order simplified DDR Volterra model. Experimental results verified that good performance and lower complexity can be achieved by using this model for a wideband Doherty power amplifier. Finally, the model is employed to compensate the nonlinearity of the Doherty power amplifier, and over 12 dB adjacent channel leakage ratio (ACLR) improvement is achieved for a five-carrier long-term evolution advanced (LTE-A) signal of 100 MHz bandwidth. [ABSTRACT FROM PUBLISHER]

In this letter, a low-cost continuously tunable substrate integrated waveguide (SIW) resonator and a low phase noise SIW voltage-controlled oscillator (VCO) are presented. A simple new structure for coupling varactor to the SIW cavity is proposed, which realizes a simple circuit layout for the tuning resonator. Equivalent circuit model is given for the varactor coupled resonator. Relation between the coupling coefficient k and the relative tuning bandwidth is analyzed. Prototypes of tunable SIW resonator and a low phase noise SIW VCO have been designed and fabricated. Measured results show that the proposed resonator possesses unloaded Q factor of 286–299 for a tuning range of 492 MHz, and the phase noise of the SIW VCO is - 93\mathchar"707B -95.6~dBc/Hz at 100 kHz offset for the whole oscillating frequency range of 455 MHz at X-Band. [ABSTRACT FROM PUBLISHER]

In this letter, a novel absorbing boundary condition (ABC) is proposed for the 3-D split-step finite-difference time-domain (FDTD) method. Compared with the traditional Mur first-order ABC, the proposed ABC is simpler and requires less additional computation. Numerical simulation results show that the reflection error of the proposed ABC is much lower than that of the traditional Mur first-order ABC and its modifications. Further investigation shows that the accuracy of the proposed ABC is almost equivalent to the Mur second-order ABC. [ABSTRACT FROM PUBLISHER]

In this letter, dynamic fuzzy neural networks (D-FNN) are applied to model power amplifiers (PAs) with memory effects. The D-FNN model implements Takagi-Sugeno-Kang (TSK) fuzzy systems based on extended radial bias function (RBF) neural networks. The parameters of the model are trained by the online self-organized learning algorithm, in which the neurons can be recruited or deleted dynamically according to their significance to system performance, and the over fitting or over training problems can be avoided. The D-FNN model is validated in our test bench in which a Doherty PA is excited with 10 MHz and 20 MHz worldwide interoperability for microwave access (WiMAX) signals. Experimental results show that the D-FNN model can give an accurate approximation to characterize the wideband PAs with memory effects. [ABSTRACT FROM PUBLISHER]