A known source of error in noise figure characterization is the variation of the device characteristics within the bandwidth of the instrument receiver. In this paper, an in-depth analysis of the effect of the receiver bandwidth on noise figure characterization accuracy is developed. For the first time, comparative results for Y-factor and cold-source techniques are given. The analysis clarifies some contradictions about the origin and the final impact of bandwidth effects in Y-factor. In addition, effects derived from an excessively wide bandwidth of the noise receiver are shown to be completely different in both techniques, being more critical in cold-source. As a result of the analysis, correction terms are provided for those cases in which receivers with narrow enough bandwidths are not available. The conclusions extracted from the theoretical formulation are confirmed by the measurements carried out on several narrow-band devices under tests with different characteristics.

This paper, following up on the previous work, investigates the effect of the input coupler's load termination of a balanced amplifier in a beam-steering system. The noise generated in this load termination deteriorates the amplifier noise resistance, which increases the noise temperature due to a varying active reflection coefficient at the antenna ports as a function of scan angle. In reducing this effect, the balanced configuration is made more favorable for radio astronomy applications. By lowering the value of the impedance termination on the fourth port of the quadrature coupler an improvement in noise temperature sensitivity is achieved at the cost of reduced power matching.

This paper presents a design method of internally-matched packaged GaN high electron mobility transistors (HEMTs) for achieving not only high-efficiency and high-power performances but also a wide bandwidth and insensitivity to harmonic terminations in the S-band. The package and its internal matching networks are synthesized to confine the second harmonic impedances seen by the GaN die to high-efficiency regions whatever the harmonic impedances presented outside the package. This paper reports the design of a packaged GaN HEMT achieving 78% of power-added-efficiency (PAE) and 25 W of output power at 2.5 GHz. A packaged GaN power bar is also reported with the addition of fundamental matching networks inside the package. In 50 Ω environment, the packaged GaN power bar provided more than 56% of PAE from 2.5 to 3.1 GHz and was desensitized to harmonic load variations with less than two points of PAE variation when a load-pull is performed at second harmonic frequencies outside the package.

Large-signal (L-S) characterization of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on silicon designed to operate at different millimeter-wave (mm-wave) and terahertz (THz) frequencies up to 0.5 THz is carried out in this paper using an L-S simulation method developed by the authors based on non-sinusoidal voltage excitation (NSVE) model. L-S simulation results show that the device is capable of delivering peak RF power of 657.64 mW with 8.25% conversion efficiency at 94 GHz for 50% voltage modulation; whereas RF power output and efficiency reduce to 89.61 mW and 2.22% respectively at 0.5 THz for same voltage modulation. Effect of parasitic series resistance on the L-S properties of DDR Si IMPATTs is also investigated, which shows that the decrease in RF power output and conversion efficiency of the device due to series resistance is more pronounced at higher frequencies especially at the THz regime. The NSVE L-S simulation results are compared with well established double-iterative field maximum (DEFM) small-signal (S-S) simulation results and finally both are compared with the experimental results. The comparative study shows that the proposed NSVE L-S simulation results are in closer agreement with experimental results as compared to those of DEFM S-S simulation.

This paper presents a new behavioral model for power amplifiers that accomplishes the capture of nonlinear low-frequency memory effects with reduced complexity and superior precision. It has been extensively evaluated with a commercial amplifier using wideband code-division multiple-access (WCDMA)-like modulated data with symbol rates in the range of 2 ksym/s to 1 Msym/s, and it is shown that the first dynamic reduction of the proposed model is successfully compared with other highly efficient methods in terms of complexity and generalization capacity.

This paper presents a novel technology for the implementation of substrate-integrated waveguide (SIW) structures, based on a paper substrate and realized by an inkjet-printing fabrication process. The use of paper permits to implement low-cost microwave structures and components, by adopting a completely eco-friendly implementation technology. SIW structures appear particularly suitable for implementation on paper, due to the possibility to easily realize multilayered topologies and conformal geometries. In this paper, SIW passive components, and antennas (including straight interconnects, band-pass filters, and slotted-waveguide antennas) are proposed for the first time. The design of the components, the steps of the fabrication process, and the experimental characterization of the prototypes are reported in this paper.

Power amplifier (PA) nonlinearities and the digital predistortion (DPD) required for linearization are modeled at baseband using the memoryless polynomial, memory polynomial, and pruned Volterra series. The sampling requirements for the nonlinear basis waveforms created from a band-limited signal are determined as a function of the polynomial order. A Gaussian approximation of the channel filtering is used to make the mathematical analysis tractable. For the memory polynomial and pruned Volterra series cases, the spacing between memory taps, referred to as the delay offset, is selected to trade off model accuracy and the condition number of the coefficient estimation. Examples are provided showing how to select the appropriate delay offset for a memory-based amplifier model and its effect on the DPD performance. A pruned Volterra series is proposed, which demonstrates improved DPD performance compared with the memory polynomial.

This paper presents the design of a high-power dual-band power amplifier (PA) for envelope tracking (ET) operation and its characterization in concurrent dual-band ET operation modes. The design approach relies on the specific actual signal probability distribution and the prototype was conceived for the WCDMA 3GPP DL signals. The paper discusses the impact of the ET-shaping function influence on the linearity versus mean efficiency trade-off, for both single and concurrent dual-band cases. The technique was applied to a concurrent 870 and 2140 MHz ET-PA designed around a GaN HEMT device. The ET friendly design method led to performance very close to those observed at each single band. Over a bandwidth of 100 MHz and for PAR = 6.5 dB, the measured results reported a mean DE better than 71 and 54%, with a peak power higher than 55 and 54 dBm, at the two frequency bands, respectively. When evaluated in concurrent dual-band mode with two WDCMA signals at 6.5 dB PAR each, the ET-PA exhibited an estimated average total power of 49.5 dBm with 57.1% average drain efficiency.

Radar sensors operating in the 76 81 GHz range are considered as essential parts of future vehicle safety systems and could significantly contribute in reducing the number of traffic casualties. Yet high manufacturing costs prevented their broad utilization in cars in the past. Today's SiGe processes show high potential to bring down cost of millimeter (mm)-wave systems into a range where they become attractive for mid- to low-priced cars. However, despite the impressing results achieved so far there is still a lot of work left to be done to achieve the final goal of “affordable radar safety for all”.

This paper expounds the systematic modeling of the behavior of radio frequency (RF) power amplifiers (PAs) exhibiting nonlinear, dynamic behavior. The approach begins with an analysis of the PA output signal to deduce the minimum embedding parameters required to accurately model its response, particularly the nonlinearity order and memory effects depth. The knowledge of the RF PA is then exploited in limiting the number of kernels consequently addressing the complexity of the Volterra series which has been the key hindrance to its wider practical adoption. In the proposed Volterra series model, performance is assessed and compared to memory polynomial model and dynamic deviation reduction Volterra models when used to linearize different high-power amplifiers driven with wideband signals of bandwidth up to 40 MHz. Significant linearization performance is achieved using a reduced number of kernels.

We present the design, fabrication, and measurement of a 2-way modified Wilkinson divider constructed in a coplanar geometry exhibiting ultra wideband isolation, transmission, and port matching in the millimeter-wave frequency range. The proposed divider replaces the lumped resistor in the conventional Wilkinson divider with two quarter-wave length transmission lines, a phase inverter, and two 2Z0 resistors. Except for the three ports that are coplanar waveguides (CPWs), the main body of the divider uses coplanar striplines (CPS). The phase inverter is realized using a simple airbridge-based crossover which is compatible with a modern monolithic microwave integrated circuit process. The divider has a ring-like configuration fabricated on a 620 µm thick semi-insulating GaAs wafer using electron beam lithography (EBL) technology. Three-dimensional (3D) full-wave electromagnetic simulations have been carried out to optimize the design and investigate the possible effect of fabrication tolerance on the performance of the crossover and the divider. Two dividers working at center frequencies of 25 and 80 GHz have been designed, fabricated, and tested. They all show consistent performance in terms of bandwidth, isolation, and port matching. Experimental and simulation results are in excellent agreement.

A compact, microstrip, two-stage, room temperature, single-ended low noise amplifier (LNA) is designed using commercial components for Aperture Tile in Focus (APERTIF), a square kilometre array (SKA) pathfinder project. Various techniques are investigated to insert inductance between the source pad of the package and the ground plane of the printed circuit board (PCB), with the chosen design able to do this using standard manufacturing techniques. The desired noise temperature of 25 K (noise figure (NF) of 0.36 dB) is met over the 1.0–1.8 GHz band, with an input return loss better than 10 dB.

The field of short- and mid-range radar sensors for automotive comfort and safety systems is a fast-growing market. The frequency regulation provides a new 76–81 GHz frequency band, which will be mandatory in the EU for ultra-wideband sensors from 2018. In the “radar-on-chip for cars” (RoCC) project funded by the German Ministry of Research (BMBF), a new technology was developed based on SiGe components with the objective to make the sensors affordable for all car platforms. This paper reports on the contribution of Continental A.D.C. GmbH to the joint “RoCC” project. The aim of the project was to exploit the cost-reduction potential of the SiGe technology by a further integration of the individual components and to show that the reliability and the functionality of the new sensors can meet the current requirements of the market. For this purpose, we evaluated the new eWLB package technology of Infineon. The Institute of Microwave Techniques of the University of Ulm supported us in designing a substrate integrated slotted waveguide antenna array. Demonstration sensors for short- and mid-range applications were built up and tested in the laboratory. To show the ability of the sensors to deal with real scenarios on the road, they were integrated into an experimental vehicle.

The microstrip active patch antenna behaves like a resonant circuit/cavity with multiple resonant frequencies; furthermore, depending on the non-linearity of the device, it generates significant amount of second harmonic radiation. The location of the device on the patch that maximizes the fundamental radiated power output is found to be not the position corresponding to the minimum second harmonic content in radiated power. An optimum location of the diode on the patch has been suggested. The paper also discusses the modification of the behavior of the active antenna, which is first an oscillator; and then a radiator, under injection-locked condition. The results are presented with respect to a Gunn-mounted rectangular patch.

In this paper, authors report on an enhanced approach for the design of monolithic microwave integrated circuit (MMIC) power combining amplifiers. Commonly used techniques for the stabilization of such circuits are empirical and too conservative. This leads very often to a non-desired degradation of the radio frequency (RF) performances that are inherent to the physical properties of such stabilization networks at the fundamental frequency of operation. The methodology proposed here is based on the use of large-signal optimization processes that combine RF and stability analyses from the early stages of the design. This approach results in an improvement of the RF performances while sufficient stability margins are preserved. The optimization procedure is explained on a Ku-band MMIC power amplifier for space-borne communications.

The implementation and application of single-layer fully-planar extended-composite right-/left-handed transmission lines (E-CRLH TLs) in substrate-integrated waveguide (SIW) technology are presented. The multiband CRLH behavior of these artificial lines is explained by considering the lumped element equivalent circuit model. The potential of these lines for dual-band and quad-band applications is demonstrated by designing and fabricating a quad-band Y-junction power divider and two dual-band band-pass filters. The main relevant advantage of SIW-based E-CRLH TLs over other E-CRLH lines is fabrication simplicity, since only a single metal layer must be etched and lumped elements are avoided. The fabricated prototypes exhibit very reasonable performance. It is remarkable that for dual-band band-pass filters, standard Chebyshev responses can be obtained to a very good approximation.

This paper presents a new order selection technique of matrix memory polynomial technique that models the nonlinearities of single-branch and multi-branch transmitters. The new criteria take into account the complexity of the model in addition to its mean-square error in the selection criteria. The quasi-convexity of the proposed criteria was proven in this work. By using this proposed Akaike information criterion (AIC) and Bayesian information criterion (BIC) criteria, the model order selection was cast as a cost minimization problem. To minimize the criteria, modified gradient descent and simulated annealing algorithms were utilized which resulted in a considerable reduction in the number of search iterations. The performances of the criteria were shown by comparing the normalized mean square error (NMSE) of a higher-order model and the optimum model. It has been shown that the NMSE difference is <0.5 dB, but the complexity is much smaller.