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This paper conducts a validation of two linearization approaches that utilize baseband nonlinear linearization signals of the 2nd order, through practical experiments on an asymmetrical two-way microstrip Doherty amplifier (ADA), and simulations on a symmetrical two-way Doherty amplifier (DA) as well as the single stage power amplifier (PA) for the post-OFDM 5G modulation formats. In the first approach, linearization signals are led at the input and output of the carrier transistor in the DA, while in the second approach, they are injected at the outputs of both the carrier and peaking amplifiers. The DA was tested in simulation for the FBMC signal of 20 MHz bandwidth, while the experimental measurements were performed for the FBMC signal on the ADA for different useful signal frequency bandwidths, 5 MHz, 7.5 MHz, and 10 MHz. The maximal improvement of DA linearity obtained in simulation is 10 dB for lower power and 5 dB for maximum amplifier output power, while the second approach gives around 2 dB better results for higher power levels. The experimental test for ADA performed for considered signal bandwidths indicates 3 dB to 5 dB linearity improvement for the implemented approaches and more symmetrical results achieved by the second approach. Additionally, the simulation tests for the PA were carried out for the FBMC, UFMC, and FOFDM signals of 100 MHz bandwidth, with the application of the first linearization approach. The minimal achieved linearization improvement is 13 dB for the FOFDM signal and a maximal of 18 dB for the FBMC signal. [ABSTRACT FROM AUTHOR]

In this paper, a millimeter‐wave broadband high‐efficiency power amplifier (PA) for Ka‐band (26–32 GHz) using 0.15‐μm GaAs pseudomorphic high‐electron‐mobility transistor process is proposed. The PA utilizes a three‐stage cascade structure and adopts an RC series feedback network, which expands the bandwidth and ensures the circuit stability. To improve the output power and efficiency of the circuit, a tree‐like transistor structure is proposed. The power amplifier, it can provide 23.6 dBm output P1dB with 33.1% power‐added efficiency at 28 GHz with high linearity. The maximum small signal gain can reach 27 dB with 3‐dB bandwidth from 24 to 33 GHz for the measured results. [ABSTRACT FROM AUTHOR]

Summary: Wideband low‐noise amplifiers (LNAs) are widely used in 5G and 6G communication systems. This paper first analyzes two common bandwidth extension technologies: the stagger tuning technique and the magnetically coupled resonators (MCR) technique. Then, a four‐stage LNA based on double‐tuned transformer combined with stagger tuning idea and MCR idea was proposed. In order to improve the broadband characteristics of the LNA, the loose coupling double‐tuned transformer is carefully designed. Compared with the traditional stagger tuning LNA, it has better broadband characteristics, lower element error sensitivity, and lower design complexity. This designs a gain bandwidth product of 1.48 T with a −3‐dB bandwidth in 9.11 GHz and the noise factor is lower than 3 dB, which covers more than 45% −3‐dB fractional bandwidth. The LNA consumes 37‐mW power with a 1.1‐V supply and occupies 1.22 × 0.4 mm2. [ABSTRACT FROM AUTHOR]

This paper proposes a novel Class‐F broadband power amplifier design method. A Class‐F power amplifier for 1.3–2.5 GHz is fabricated by step‐matching, combining a harmonic control structure and a parasitic compensation circuit. A bandwidth expansion structure is established based on microstrip lines and capacitor. The proposed structure resolves the low efficiency caused by the coincidence of the fundamental frequency band and second harmonic frequency band, which allows the power amplifier to function properly from 1.1 to 2.5 GHz. A high‐efficiency broadband power amplifier is tested to find that the saturated output power with the proposed device is between 40.1 and 41.7 dBm, the gain is from 9.3 to 14.4 dB, and the drain efficiency is 60.8%–84.2% at 1.1–2.5 GHz frequency. [ABSTRACT FROM AUTHOR]

This paper proposes a generalized design methodology for extending the bandwidth and output back-off range of an equal-cell Doherty power amplifier (EC-DPA). The parameters of the EC-DPA combiner are derived based on pre-defined asymmetrical voltage and nonlinear current profiles. It is illustrated that the design parameters of the EC-DPA can be expressed as a function of the combining load. Then, the combining load can be optimized to extend the bandwidth of the proposed EC-DPA. As a validation, an 1.4–2.1 GHz EC-DPA with extended output back-off range is implemented in this paper. Under a continuous-wave (CW) signal excitation, the fabricated EC-DPA achieves a maximum output power of 42.6–43.8 dBm, a saturation drain efficiency (DE) of 50.2%–70.2% and a 10 dB back-off DE of 45.2%–53.7% over 1.4–2.1 GHz. Moreover, under the excitation of a 20 MHz modulated signal with a peak-to-average power ratio (PAPR) of 8.0 dB, the measured adjacent channel leakage ratios (ACLRs) of the fabricated EC-DPA changes from −36.2 dBc to −25.5 dBc at the lower band and from −34.6 to −23.8 dBc at the upper band over 1.4–2.1 GHz when the average output power is 35.0 dBm. [ABSTRACT FROM AUTHOR]

The motivation of this paper increases the bandwidth of power amplifier to multioctave by matching circuit, which consists of ferrite balun, 4:1 transformers and RC network feedback to make atrade-off between gain and VSWR. So this work discusses the design of a push-pull power amplifier demonstrating over more than a decade bandwidth using matching networks to achieve [30–800] MHz bandwidth. Matching transformer techniques can be used in order to minimise the return loss and increase the gain. Modification of the classical topology, based on inductive compensation of the parasitic capacitance of ferrite, has been proposed and used to design a 1:4 transformer. Practically, miss-match and heating is the main concern for broadband performance of high power amplifier. Coaxial cable and ferrite are also used to dissipate the heat (high temperature) resulting from the amplification power, in addition to installing the board on a cooler with appropriate dimensions, so we get the best match and stability. The simulation results are compared with the measurements. The measured results show that 20.5–17.46 dB of gain, 50.5–47.46 dBm of output power, and 50.9 of drain efficiency are delivered. [ABSTRACT FROM AUTHOR]

A polarization splitter based on gold filled dual-core photonic crystal fiber (DC-PCF) that can work from 1420 nm to 1980 nm (560 nm bandwidth) is proposed in this work. The splitter has an extinction ratio lower than –20 dB over a large bandwidth with a total length of 254.6 µm. The key principle of operation of the splitter is the induced change in the refractive index of the y-odd mode when it is coupled to the second order plasmonic mode, while other supermodes are weakly affected by the plasmonic mode. The proposed broadband and compact polarization splitter may find applications in communications and sensing, being capable of working in the infrared and mid-infrared wavelength ranges. [ABSTRACT FROM AUTHOR]

An impedance matched parametric amplifier (IMPA) with Josephson junctions is fabricated and characterized. A hybrid structure containing coplanar and strip structures is implemented to realize an impedance taper line and a plate capacitor in an LC nonlinear resonator based on Josephson junctions. The upper plate of the capacitor is isolated with SiNx without grounding as well as the strips. Such easily-prepared designs greatly reduce the requirements for lithography alignment and precision, which makes the fabrication process more reliable. The experimental results show that in such IMPA a gain higher than 25 dB with a bandwidth of about 100 MHz can be obtained. This broadband amplifier operates close to the quantum limit. By adjusting the working point, a higher bandwidth of about 400 MHz can be obtained with a gain of about 17 dB. [ABSTRACT FROM AUTHOR]

Previously, the bandwidth of conventional Doherty power amplifiers (DPAs) is limited by the phase dispersion of the microstrip impedance transformer (IT). To overcome this phase dispersion, minimization of the phase delay of the IT is required, however at the expense of load modulation bandwidth, which limits further bandwidth extension. In this article, we present a broadband Doherty-like PA topology that, for the first time, uses parallel right- and left-handed ITs. This satisfies the minimal phase delay requirement while simultaneously maintaining wideband load modulation. Consequently, the frequency range for load modulation can be significantly extended. For demonstration purposes, a Doherty-like PA prototype is realized using two identical 10-W GaN HEMTs. Measurement results show that a drain efficiency of at least 40% is achieved at 5.2–6-dB back-off from 1.25 to 2.30 GHz, which corresponds to a very wide bandwidth of ~60%. [ABSTRACT FROM AUTHOR]

High frequency (HF) transmitter implemented with the multioctave broadband power amplifier (PA) enables long-distance communication and has strong survivability. However, it is faced with the problem of harmonics because of the nonlinearity of the PA. We first consider canceling the harmonics using a harmonic cancellation digital predistortion (HC-DPD) technique, instead of lossy and bulky analog filter banks. A uniform complex-valued Hilbert transform-based polynomial (HTBP) function is proposed for the modeling of the harmonics, as well as the fundamental component in the real-valued input and output signals. In order to validate this idea, detailed experiments were performed for carrier frequencies located at 5 and 10 MHz, respectively. After the proposed HC-DPD, the harmonics were all canceled to satisfy the linearization requirements. In particular, the improvement of the second harmonic is more than 40 dB, which is nearly 20 dB better than that of the memoryless polynomial (MLP) model. Furthermore, the experimental results demonstrate that the proposed technique is scalable, in which the model coefficients extracted at a specific power level, signal bandwidth, and carrier frequency can be extended to other scenarios. Both the second and third harmonics were canceled for being below −45 dBc after the HC-DPD. [ABSTRACT FROM AUTHOR]

This paper presents a method for designing a power amplifier for high efficiency Class-E broadband topology using a low- pass filter of a high order is presented. A study of the state of the art regarding the design of a power amplifier Class-E performed operating within the frequency band of 0.8 GHz to 1.5 GHz. In the design accordingly ensures the attenuation of the power of the second and third harmonic, critical to achieving high efficiency amplification criterion. The design equations and simulation were made in AWR Design Environment V13. The efficiency levels achieved were 74%, the efficiency of added power (PAE) 72% power gain was more than 8 dB across the band, a bandwidth of665 MHz, and the band of 60.8% was achieved, with an efficiency drain and PAE above 50%. [ABSTRACT FROM AUTHOR]

In this article, we present a novel technique to build digital predistorters that can linearize broadband power amplifiers (PAs) using reduced sampling rates. In contrast to conventional digital predistortion (DPD) where oversampling is necessary to avoid aliasing effect, the proposed method cancels the aliasing distortion using a sliced multistage cancellation scheme. A large reduction of sampling rate can be achieved in digital implementation of DPD, significantly reducing power consumption and implementation cost. Experimental results show that a DPD with a sampling rate of merely $1.5\times $ , instead of $5 \times $ , signal bandwidth, can still produce satisfactory performance within the linearization bandwidth but consume only one-third of power, compared with that using the conventional approaches. The proposed technique provides a promising solution for the next-generation 5G systems, where large signal bandwidths are required. [ABSTRACT FROM AUTHOR]

This paper propose an inverted sequential load-modulated balanced amplifier (ISLMBA) for extending the dynamic power range of a power amplifier (PA) over a wide bandwidth. The proposed ISLMBA consists of a control amplifier (CA) and a balanced PA (BPA) pair. A composited impedance inverter is inserted between each BPA transistor and the output coupler. The composited impedance inverter is composed by the intrinsic elements and output matching network (OMN) of the BPA transistor. In this way, the intrinsic elements can be fully absorbed into the impedance inverter over a wide bandwidth. Meanwhile, the load modulation trajectories of the BPA transistors can be optimized over a wide bandwidth by tuning the characteristic impedance of the impedance inverter. The theoretical current, voltage and load-modulation profiles of the ISLMBA are comprehensively analyzed. It is illustrated that the proposed ISLMBA could maintain high efficiency at deep output back-off power level over a wide bandwidth. Moreover, this work designs and fabricates an ISLMBA operating over 1.3–2.55 GHz to verify the proposed PA architecture. The fabricated ISLMBA exhibits a saturation drain efficiency (DE) of 54.5%–73.8% and a saturation output power of 42.9–45.9 dBm. At the same time, the fabricated ISLMBA achieves a 10 dB back-off DE of 42.1%–63.9% over the frequency band of interest. When the fabricated ISLMBA is stimulated by a 20 MHz wideband signal with a peak-to-average power ratio (PAPR) of 10.2 dB at 2.0 GHz, the measured adjacent channel leakage ratios (after predistortion) are −47.7 and −48.8 dBc at the lower and upper bands, respectively. [ABSTRACT FROM AUTHOR]

This paper presents the design and implementation of a bidirectional distributed amplifier (BDDA) in a 0.18- $\boldsymbol \mu \text{m}$ CMOS process. The performance of the BDDA is theoretically analyzed, and the optimum number of gain stages ($n_{\text {opt}}$), maximum achievable power gain ($G_{P}$), and circuit bandwidth are formulated. In addition, a new formula for proper choice of the number of DA stages (i.e., $n$) is offered where dc-power consumption of the circuit ($P_{\text {dc}}$) is also considered. This formula optimizes $G_{P}/P_{\text {dc}}$ , and it is preferred over the conventional $n_{\text {opt}}$ formula. To validate the theoretical analyses, a 2–12-GHz BDDA with high output 1-dB compression point of +16 dBm and small-signal gain of 10 dB is fabricated. The BDDA chip occupies 1.89-mm2 die area, and its average measured noise figure and $P_{\text {dc}}$ are 6.8 dB and 0.38 W in the high-power mode and 6.5 dB and 0.13 W in the low-power mode, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we describe the design of the first reported full W-band (75–110 GHz) power amplifier (PA) monolithic microwave integrated circuits (MMICs) based on gallium nitride technology. The discussed MMICs come in two versions. Over a bandwidth (BW) of 70–110 GHz, the three-stage PA can deliver, on average, 25.6 dBm with a power-added efficiency (PAE) of 6.5%, while the four-stage PA is able to generate 27 dBm with a PAE of 6.1%. A peak output power of 28.6 dBm is achieved at 80 GHz with a PAE of 8.6%, which corresponds to a power density of 2.6 W/mm. The significant BW was achieved partially by incorporating a novel type of broadband radial stub into the design, which can provide nearly a twofold rejection-BW improvement over the conventional version. To the best of our knowledge, no other solid-state circuit can deliver such power levels over the complete W-band. [ABSTRACT FROM AUTHOR]

In this paper, we explore theoretically and experimentally broadband spatiotemporally modulated magnetless circulators realized by combining three-port nonreciprocal junctions with three identical bandpass filters. We develop a rigorous theory for the proposed circuit, which allows optimizing its design and to derive a global bound on the maximum possible bandwidth (BW). We verify our theory with simulations and measurements of a printed circuit board prototype based on a differential wye junction and second-order Chebyshev bandpass filters, resulting in a measured fractional BW of 13.9% at a center frequency of 1 GHz. [ABSTRACT FROM AUTHOR]

Total bandwidth of existing wireless communication technologies covers a wide frequency range of over one octave. But most existing power amplifier configurations cannot meet this requirement while at the same time maintaining a high efficiency. Therefore, a new structure that can achieve multioctave bandwidth is proposed in this paper together with the design methodology. The difficulty in realizing a bandwidth larger than one octave lies in the overlapping of fundamental and harmonic frequencies. Regarding this problem, the continuous class-F mode is extended to allow a resistive second harmonic impedance, rather than the pure reactive one. With the relaxed design requirements and overlapping design space of fundamental and second harmonic frequencies, harmonic tuning and fundamental frequency matching networks can be designed separately. More importantly, broadband matching for fundamental frequencies can be implemented simply by considering only three fundamental frequency points using the multiple frequencies matching method. To verify the validity of the proposed methodology, a multioctave power amplifier was designed, fabricated, and measured. Measured results verify a wide bandwidth of 128.5% from 0.5 to 2.3 GHz. Over this frequency range, drain efficiency was larger than 60% with output power greater than 39.2 dBm and large signal gain larger than 11.7 dB. [ABSTRACT FROM PUBLISHER]

In this paper, a broadband continuous-mode Doherty power amplifier (CM-DPA) is realized taking advantage of the noninfinity output impedances of peaking stage. Specifically, the carrier PA of the designed DPA operates in a continuous class-J mode when the peaking PA is in the OFF-state, where the output impedance of the peaking PA has some influences on the carrier PA. When the peaking transistor is in the OFF-state, the load impedance variation of the carrier transistor versus noninfinity peaking impedance is presented in this contribution. The proposed method surmounts the back-off drain efficiency deterioration of DPAs at two side working bands through elaborately processing the noninfinity peaking impedance. This paper also presents a method to derive the required OFF-state output impedance of the peaking stage by the carrier PA in a symmetrical broadband DPA. A broadband CM-DPA working over 1.6–2.7 GHz (bandwidth of 51%) is designed and fabricated for interpreting our theories. The simulated load trajectory of the carrier transistor is in line with the design space of continuous class-J mode. Under continuous wave excitation, experimental results show the drain efficiencies of 46.5%–63.5% at 6-dB output back-off power levels and 56%–75.3% at peaking power levels. The maximum output power of this DPA is 43.8–45.2 dBm with a gain of 9.4–11.5 dB across the whole working band. Furthermore, a 20-MHz LTE modulated signal with a peak-to-average power ratio of 7.4 dB is also applied to the fabricated CM-DPA at 2.2 GHz. At an average output power of 37.5 dBm, measurement results show the adjacent channel power ratios of −30.2 and −50.1 dBc before and after digital predistortion, respectively. [ABSTRACT FROM PUBLISHER]

This study presents a CMOS distributed amplifier (DA) with pseudo differential amplifying that achieves DC-40GHz bandwidth (BW) in 0.18-m RF CMOS process. The DA with three-stage amplifying cells was proposed to improve the DA performance. The inter-stage was composed of pseudo differential amplifying for bandwidth extension. By incorporating the pseudo differential amplifier configuration and capacitor-less circuit in the stages, the DA provides average gain and high bandwidth. The simulation results showed that the DA has a S of 6.4dB, 3-dB BW from DC up to 40GHz. It also has a minimum noise figure (NF) of 4.27dB, one dB compression point (P of 3.5dBm, a high reverse isolation S of less than 15dB, an input return loss S and output return loss S of less than 16 and 12dB, respectively. It consumes 115mW and occupies a total active area of 0.27mm2. [ABSTRACT FROM AUTHOR]

This paper presents two integrated concurrent dual-band class-J power amplifiers (PAs) in AlGaAs–InGaAs pHEMT technology. Design flexibility of class-J space is employed to explore the availability of a dual-band PA where the center frequency of the second band is twice the center frequency of the first band ( f2=2f1 ). The theoretical formulations are developed for f2=2f1 case, for which it is not feasible to obtain high efficiencies using class-F−1, class-F, and other high-efficiency modes. A proof of concept 5/10-GHz class-J PA is manufactured in a 0.1- \mu \textm GaAs pHEMT technology. The proposed PA delivers 26.9- and 26-dBm output power with peak power added efficiencies (PAEs) of 49% and 46% at 5 and 10 GHz, respectively. Another 6/16-GHz ( f2\neq 2f1 ) dual-band concurrent class-J PA with a PAE of more than 50% in both bands is also fabricated in a 0.25- \mu \textm GaAs pHEMT technology. The designed dual-band class-J PA delivers 26- and 25.5-dBm output power at 6 and 16 GHz, respectively. [ABSTRACT FROM PUBLISHER]

A low-noise (⩽4 fA/√Hz), broadband (⩾100 kHz) compact architecture and related operation solutions are proposed for portable and low-cost time-domain acquisition of currents with effective resolution in the order of 1 pA and below. The front-end architecture is based on an integrating-differentiating scheme to achieve the optimal performance in terms of input-referred equivalent noise, but it overcomes the typical noise/bandwidth trade-off by making the sampling frequency of the A/D conversion independent from the rate at which the analog front-end is reset. In order to strongly mitigate the main drawback, i.e., the introduction in the system of an inherent time-variance, a Track-and-Hold circuit synchronized with the reset is exploited. For validation purposes, a dual-channel prototype was implemented in a low-cost CMOS technology. The prototype is characterized by standard figures of merit and is experimentally validated by two simple case studies, which are typical of practical applications. [ABSTRACT FROM AUTHOR]

ABSTRACT In this work, a 4-element wide band frequency agile multiple-input-multiple-output (MIMO) antenna system is presented. Frequency agility is achieved by loading the antenna elements with capacitive reactance using varactor diodes. The proposed MIMO antenna is a wide band antenna with very wide tunability range between 1610 and 2710 MHz, thus covering several well-known wireless standards. Each tuned band has at least 470 MHz bandwidth. The proposed design is simple in structure with low profile antenna elements. The design is fabricated on an FR4 substrate with single element dimensions of 7.9 × 26.9 mm2 on a single board of dimensions 60 × 100 × 0.8 mm3. The proposed MIMO antenna system is highly suitable to be used in wireless handheld devices and mobile terminals within a cognitive radio platform. The antenna system is also characterized for MIMO performance metrics. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2276-2280, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT This paper introduces a matching technique for highly sensitive integrated broadband low-noise amplifiers. Noise matching is achieved by the paralleling of identical input transistors. Impedance matching, based on reducing the number of components to the absolute minimum, is done by using the base-collector capacitance as network element. Using a 0.13 [ABSTRACT FROM AUTHOR]

This paper presents the results of a theoretical investigation of the asymmetrical bridged T-coil (BTC) bandwidth enhancement network under the condition of maximally flat magnitude (MFM) response. Conventionally, the BTC is used in the symmetrical configuration and it is well known that, as compared to the commonly used RC load, the maximum bandwidth enhancement ratio (BWER) under the MFM condition is 2√2. It is shown here that by introducing asymmetry, even under the constraint of MFM response, the maximum achievable BWER is theoretically unlimited, the limit being set only by practical considerations. Unlimited BWER has never been considered possible, even theoretically, with BTC or any other network, and the result reported here is believed to be a breakthrough in the design of wide-band and ultra wide-band amplifiers. Simulations for a few designs indicate that practical realization of the full potential of the asymmetrical BTC may have to wait for improved technologies which facilitate tight coupling between the two parts of the coil and also minimize parasitic effects. [ABSTRACT FROM PUBLISHER]

ABSTRACT In this paper, two versions of a complete RF front-end for a 10 Gbps optical receiver are presented. The RF front-end consists of a transimpedance amplifier and a limiter amplifier. Two versions of the TIA amplifiers are proposed. The first topology has 54 dB transimpedance gain, 11.5 GHz bandwidth and has a input current noise density of only [ABSTRACT FROM AUTHOR]

The feasibility of deploying reflectarray antennas on synchronous satellites with the aim of achieving isoflux beam for optimum earth coverage is investigated. Due to the difference in free space loss from the satellite to different points on the earth, a conventional collimated beam pointing to the Earth centre is not efficient. So, there is a need for a radiation pattern whose gain increases at the line of sight angles to the horizon and diminishes towards the centre. Accordingly, a single-layer reflectarray antenna composed of loaded square patches is fabricated and tested. In this regard, the dimensions of reflectarray elements are adjusted using a robust optimization technique that minimizes the adverse effects of frequency dispersion in the intended frequency bandwidth. Experimental results demonstrate a stable radiation pattern with a relative bandwidth of about 11% at 14.25 GHz centre frequency. [ABSTRACT FROM AUTHOR]

ABSTRACT This article proposes a design strategy for broadband Doherty power amplifier (PA) using broadband load combiner. The bandwidth of the Doherty PA based on the proposed combiner using packaged transistor is about 2.5 times the bandwidth of conventional Doherty PA using a quarter-wave transformer. An easy to implement analytical design methodology has been presented for the proposed load-combiner while describing the bandwidth enhancement strategy. The design methodology is validated with the design of a broadband Doherty PA based on CREE 10 W packaged GaN high electron mobility transistor devices using the proposed load combiner. Measurement results show more than 45% drain efficiency at 6 dB output power back-off (OPBO) over 400 MHz frequency range, centred around 1.95 GHz. The peak drain efficiency at saturation is better than 60% over this band of operation. At 6 dB OPBO, the maximum improvement of 18.5% in drain efficiency is achieved as compared to the balanced mode PA. Measurement with single carrier wideband code division multiple access modulated signal shows the average drain efficiency of more than 44% at 36.6 dBm average output power at center frequency of operation. The adjacent channel power ratio is better than −45 dBc after applying digital predistortion. The circuit is realized with microstrip technology, which can be easily fabricated using conventional printed circuit processes. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:655-674, 2015. [ABSTRACT FROM AUTHOR]

Hybrid optical amplifiers (HOAs) are crucially important for broadband band amplification, and are widely deployed in high-capacity dense wavelength division multiplexed systems. We summarize the present state-of-the-art in this rapidly growing field. In addition, theoretical background and various inline configurations of optical amplifiers have been presented. Various issues such as gain flatness, gain bandwidth, transient effect, and crosstalk were presented in HOAs. Results show that the HOAs provide better gain flatness without using any expensive gain flattening techniques, and an acceptable range of gain, noise figure, bit error rate, and transience. [ABSTRACT FROM AUTHOR]

A novel broadband mid-infrared (mid-IR) difference frequency generation (DFG) scheme in a uniform grating periodically poled lithium niobate (PPLN) on the basis of gradient temperature control technique is proposed. Our theoretical results show that the quasi-phase matching bandwidth (BW) for the idler is <10 nm under a fixed crystal temperature condition for two fundamental lights operating in the 1060 and 1550 nm regions. The BW for the idler is remarkably enhanced with increasing temperature gradient across the crystal. When the pump wavelength is fixed at 1.08 μm, the BW for the idler is increased to 18, 40, and 102 nm at 20, 40, and 60 °C, respectively. However, when the signal wavelength is fixed at 1.58 μm, two idler QPM bands for each crystal temperature are achieved. These bands can be simultaneously broadened (in nanometers) to 21 and 14, 54 and 64, and 158 and 161, at 20, 40, and 60 °C, respectively. The broadened idler QPM bands can also be moved over a wide range by adjusting the temperatures at both endfaces of the crystal while maintaining a certain temperature gradient. This scenario is quite useful for further enhancing the mid-IR wavelength coverage. [ABSTRACT FROM AUTHOR]

Three wideband amplifiers in double-heterojunction bipolar transistor technology have been designed and measured. The amplifiers use different types of distributed amplifier (DA) topologies, all based on cascode gain cells. A single-stage DA design achieves 7.5-dB gain and 192-GHz bandwidth and a two-cascaded single-stage DA achieves an average gain of 16 dB with a bandwidth of 235 GHz. The third circuit is a conventional DA with more than 10-dB gain from 70 kHz up to 180 GHz. To the authors’ best knowledge, the single-stage DA and the two-cascaded single-stage DA are the widest band amplifiers in any technology reported to date. Furthermore, the conventional DA has a record bandwidth for circuits in conventional DA topology with gain from near dc. [ABSTRACT FROM AUTHOR]

This paper describes a fully integrated E-band power amplifier (PA) in 40-nm CMOS. The design and layout of the unit PA stage is optimized to achieve high output power while maintaining high power gain. A broadband parallel-series power combiner is proposed to provide the PA stage optimum load impedance across the complete E-band. The complete PA achieves a measured saturated output power of 20.9 dBm with more than 15-GHz small-signal -3-dB bandwidth and 22% power-added efficiency (PAE) at 0.9-V supply. The in-band variation of -1-dB compressed power (P1\ {dB}) is only \pm0.25 dB. This is the first reported silicon-based PA that covers both 71–76- and 81–86-GHz bands with uniform gain, output power, and PAE. [ABSTRACT FROM AUTHOR]

We propose an isolation network to simultaneously improve the input return loss, output return loss and isolation of the Wilkinson power divider in a wide bandwidth. The required even mode and odd mode reflection coefficients of the isolation network are calculated. Constructed even and odd mode circuits are combined to give the desired isolation network. Analytical expressions for the optimal component values for a single-section divider are given. Compared with the single-section Wilkinson divider, the final design can triple the bandwidth for an input-output return loss and isolation of greater than 25 dB. Broadband characteristic is achieved without increasing the number of sections hence extra length and insertion loss are avoided. Wide operation bandwidth of the new divider is verified by experimental results. The proposed method can be applied to a two-section divider, also broadening its bandwidth. [ABSTRACT FROM AUTHOR]

In this paper, we further develop the concept of a wideband Doherty power-amplifier topology with reconfigurable efficiency. This is done by presenting new theory that - in contrast to previous work - makes it possible to analyze how the performance of the amplifier depends on the input network properties and the choice of gate bias voltages. The utility of the presented theory is demonstrated by the design and characterization of a gallium-nitride monolithic-microwave integrated-circuit amplifier designed in close agreement with the theoretical findings. Continuous-wave (CW) measurements show that the fabricated amplifier provides more than 31% power-added efficiency (PAE) at 9-dB output power back-off over a 5.8-8.8-GHz frequency range, and that the efficiency can be reconfigured as predicted by the presented theory. Modulated measurements - employing digital pre-distortion (DPD) and a 20-MHz signal with 8.5-dB peak-to-average power ratio - show more than 32% average PAE across the same 5.8-8.8-GHz frequency range. Both the CW and the modulated measurements thereby verify the wideband performance predicted by the theory. In addition, modulated measurements at 7.0 GHz without DPD show that the amplifier can provide excellent raw linearity by demonstrating -41.0-dBc adjacent channel power ratio and -34.2-dB normalized mean square error. [ABSTRACT FROM AUTHOR]

This paper presents a bandwidth enhancement technique for broadband Darlington amplifiers. A detailed analysis of the high-frequency performance of the Darlington amplifier and the effect of bandwidth enhancement is provided. A design procedure is also given for broadband feedback Darlington amplifiers with bandwidth enhancement and gain flattening. A single- and a three-stage feedback amplifier with the proposed improvements are designed and implemented in a 0.25-\mu\ m AlGaAs–InGaAs pHEMT technology. The single-stage amplifier provides \ 6\pm \ 0.4~\ dB of small-signal gain in the frequency band of 1–30 GHz. The three-stage amplifier features \ 17.8\pm \ 0.8~\ dB of small-signal gain in the frequency band of 2–29 GHz. It provides a gain-bandwidth product of 217 GHz, which is 3.3 times larger than the unity gain frequency (f T) of the process. [ABSTRACT FROM AUTHOR]

New designs of wide-band rat-race couplers are proposed. The wide-band operation is achieved with the use of the microstrip nonuniform transmission line sections for the branches of the conventional rat-race coupler. The design formulas are developed using ABCD matrix and the even- and odd-mode analysis. The theoretical analysis has been verified by measurements of the two manufactured wideband rat-race couplers, one operate within 0.85-1.92 GHz and other within 1.55-3.55 GHz frequency range with the equal nor-malized characteristic impedance functions. For both fabricated couplers, the isolation pa-rameter is better than 15 dB over a 77% relative bandwidth. Also, it is shown that the designed wide-band rat-race coupler can be realized in higher frequency bands with the fixed fractional bandwidth. [ABSTRACT FROM AUTHOR]

This paper describes the design and implementation of a package-integrated Chireix outphasing RF switch-mode power amplifier (PA). The optimum loading conditions, based on class E, and the Chireix compensation elements are provided to the active devices by a dedicated low-loss bondwire-based transformer power combiner that enables a very small form factor and low cost. The realized prototype achieved 70.6-W peak power with 73% peak drain efficiency at 2.3 GHz and 28 V, and up to 81% peak drain efficiency at 2.2 GHz and 20 V. When operated for maximum power at 28 V, it reached 53.5%/43.5% average drain/total efficiency for a 9.6-dB peak-to-average-power-ratio W-CDMA signal at 2.3 GHz with low ACLR1/2 levels ( -\49/-\56 dBc after memoryless digital predistortion). Moreover, from 2.1 to 2.4 GHz, the realized PA demonstrated more than 50% drain efficiency across >\260, >\160, and >\80 MHz at 6-, 8-, and 10-dB back-off, respectively. [ABSTRACT FROM PUBLISHER]

This paper presents a high-power high-efficiency wideband suboptimum Class-E RF power amplifier based on a packaged high-power GaN HEMT. It uses a simple double-reactance compensation and impedance transformation load network that includes device intrinsic capacitance, package parasitics, low-loss microstrip transmission lines, and lumped components. This load network makes the GaN HEMT operate in suboptimum Class-E from 900 to 1500 MHz (50% fractional bandwidth at 1200 MHz). The amplifier can operate both in continuous wave and pulsed modes over its full bandwidth without tuning. It delivers up to 180-W output power with up to 85% drain efficiency and PAE=81\%. To the best of the authors' knowledge, the amplifier proposed in this work outperforms commercial grade amplifiers that operate in the same frequency band with similar output power levels. Direct applications for this amplifier include mobile satellite communications transmitters, envelope elimination and restoration digital audio broadcasting transmitters, and power stages for primary and secondary RADAR transmitters. [ABSTRACT FROM PUBLISHER]

The noise models of InP and GaAs HEMTs are compared with measurements at both 300 and 20 K. The critical parameter, Tdrain, in the Pospieszalski noise model is determined as a function of drain current by measurements of the 1-GHz noise of discrete transistors with 50-\Omega generator impedance. The dc I–V for the transistors under test are presented and effects of impact-ionization are noted. InP devices with both 100% and 75% indium mole fraction in channel are included. Examples of the design and measurement of very wideband low-noise amplifiers (LNAs) using the tested transistors are presented. At 20-K physical temperature the GaAs LNA achieves <10-K noise over the 0.7–16-GHz range with 16 mW of power and an InP LNA measures <20-K noise over the 6–50-GHz range with 30 mW of power. [ABSTRACT FROM PUBLISHER]

This paper presents CMOS distributed amplifiers (DAs) using the proposed gate–drain transformer feedback technique. The feedback allows reuse of the traveling signal to achieve a high gain-bandwidth product while maintaining low power consumption of DAs. With the folded transmission lines and patterned ground shield, the miniaturized transformer has high quality factors and a well-controlled feedback coupling coefficient. Two DAs are realized using the proposed technique in both \0.18-\mu\ m and 90-nm CMOS technologies, respectively. The \0.18-\mu\ m CMOS DA achieves a gain of 9.5 dB with a 3-dB bandwidth of 32 GHz, and the noise figure (NF) ranges from 4.1 to 7.6 dB under a power consumption of 71 mW. Under a power consumption of 60 mW, the 90-nm DA demonstrates a gain of 7 dB, a bandwidth of 61.3 GHz, and an NF below 6.2 dB up to 40 GHz. The core areas of the \0.18-\mu\ m and 90-nm designs are only 0.58 and \ 0.41 mm^2, respectively. [ABSTRACT FROM PUBLISHER]

This paper presents a compact broadband branch-line hybrid coupler. It is composed of a miniaturized branch-line hybrid coupler and broadband impedance matching networks. A coupled-line structure is used for the broadband impedance matching network. The branch-line hybrid coupler is realized by using high-impedance transmission lines and distributed capacitors. In order to further reduce the circuit size, the distributed capacitors are placed in the center space of the hybrid coupler and the coupled lines are effectively meandered. For validation, a prototype of the compact hybrid coupler was designed and fabricated at the center frequency of 1 GHz. For given conditions, the proposed hybrid has 29.4% bandwidth which is from 870 to 1170 MHz. Compared to the conventional 3-dB branch-line hybrid coupler, it exhibited a size reduction of 50.8% and an extended operating bandwidth of 66.7%. [ABSTRACT FROM AUTHOR]

Broadband amplifiers that can accommodate commercial communication standards such as GSM, UMTS, Wi-Fi, and Wi-Max are extremely important for radio equipment manufacturers. To achieve this coverage, the amplifier should provide high gain and efficiency over a band from 800 to 5200 MHz. Although there are transistor devices that have cut-off frequencies well over these frequencies, amplifiers covering such a broad-bandwidth are difficult to design due to the requirement of broadband matching networks. In this work, design of broadband tunable matching networks is investigated using Real Frequency Direct Computational Technique (RF-DCT). In order to be able to work on sample structures, impedance transforming filters are chosen and a broadband tunable matching network has been designed. Implementation of tunable inductors is investigated and the performance of a tunable matching network using tunable inductors and capacitors is demonstrated. Eventually a broadband frequency tunable amplifier has been designed using the tunable inductor concept. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013. [ABSTRACT FROM AUTHOR]

This paper presents a waveguide-based spatial power combining module using an improved four-way waveguide-based spatial power dividing/combining network. With a conventional fabrication process, the improved network performs low-loss, broadband and symmetrically power dividing/combining at higher frequency in millimeter wave band, and is easy to be integrated with solid-state high power devices for power combining applications. The corresponding validation is carried out in V-band. The proposed network has a measured loss less than 0.5 dB and exhibits very good amplitude balance and fixed phase relationship in an 8.7 % relative bandwidth, from 55 to 60 GHz. And then, a four-way waveguide-based spatial power combining module is fabricated. The measured power is more than 200 mW in 54.5-61 GHz, and the achieved power combining efficiency is more than 80 % in 54.5-60.5 GHz. [ABSTRACT FROM AUTHOR]

This paper derives the theory and presents measurements of a new power amplifier based on the Doherty power amplifier topology. It is theoretically shown that the proposed amplifier can simultaneously provide high efficiency at both full output power and at output power back-off, over a much improved bandwidth compared to the conventional Doherty power amplifier. It is also shown that the proposed amplifier allows reconfiguration of the efficiency in power back-off without the need of tunable elements. [ABSTRACT FROM PUBLISHER]

In this paper, a novel dual-band transmission-line parallel Doherty amplifier architecture for active antenna arrays and base-station applications in next-generation communication systems is presented. The carrier and peaking amplifiers using GaN HEMT Cree CGH40010P devices are designed based on the reactance compensation technique to provide optimum Class-E impedance seen by the device output at the fundamental frequency across the wide frequency range achieving drain efficiencies over 73% across the frequency range from 1.7 to 2.7 GHz. In a single-carrier WCDMA operation mode with a peak-to-average ratio of 6.5 dB, high drain efficiencies of 40%-45% can be achieved at an average output power of 39 dBm with an ACLR1 of about -30 dBc at center bandwidth frequencies of 2.14 and 2.655 GHz. [ABSTRACT FROM AUTHOR]

We demonstrate the output characteristic of broadband parametric amplification of incoherent light pulses in a 355-nm pumped degenerate picosecond optical parametric amplification with either saturated or unsaturated amplification. The optical parametric amplifier is seeded by the fluorescence generated in a solution of pyridine-1 dye in ethanol. With the saturated amplification, we can obtain high energy incoherent light pulses, whose full width at half maximum bandwidth varies from 16 nm to 53 nm for the different phase matching angles near degeneracy. Moreover, the unsaturated bandwidth of the amplified pulses fits well to the calculated result at degeneracy. Selecting s-polarized fluorescence with a Glan-Taylor prism, the maximum bandwidth of the amplified fluorescence is found to be 59 nm for a purely s-polarized seed. The maximum output energy is 0.67 mJ for the optical parametric amplifier. By using an optical filter and compressor, the generated high energy incoherent light has great potential as the incoherent pump, signal or idler wave of a parametric down-conversion process, so that a wave with a high degree of coherence can be generated from an incoherent pump light. [ABSTRACT FROM AUTHOR]

This paper describes the design approach employed for achieving approximated continuous Class-F power amplifier (PA) modes over wide bandwidths. The importance of the nonlinear device capacitance for wave-shaping the continuous Class-F voltage and current waveforms is highlighted, thus reducing the device sensitivity to second and third harmonic impedance terminations. By identifying the high-efficiency regions on the reactance plane for harmonic band placement, the design can be reduced to a fundamental matching problem. The distributed simplified real frequency technique synthesis algorithm can then be utilized to achieve wideband operation. Using a 10-W Cree GaN HEMT device, greater than 70% efficiency has been measured over a 51% bandwidth from 1.45 to 2.45 GHz, with output powers of 11–16.8 W. The nonlinear PA was then linearized using digital predistortion with 20-MHz long-term evolution and 40-MHz eight-carrier W-CDMA excitation signals, to attain adjacent channel power ratios below -\53 and -\49 dBc, respectively. To the best of the authors' knowledge, the measured results represent the best performance obtained from a broadband switch-mode PA, and the best linearized switch-mode performance using 20- and 40-MHz modulated signals. [ABSTRACT FROM PUBLISHER]

A novel cell element, the combination of meander-shaped rectangle and ring, is presented for reflectarray. The feature of the cell element is investigated along with the design of the feed and array. A 52-element array prototype based on the proposed element has been fabricated and measured showing good results over a 26% 1-dB gain bandwidth. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:500-503, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26563 [ABSTRACT FROM AUTHOR]

In this article, a C-Band broadband patch antenna is designed. The binary particle swarm optimization (BPSO) combining with IE3D software is adopted to broaden the bandwidth of the patch antenna automatically. Characteristics of the antenna are calculated using the well-known Zeland IE3D software package while the bandwidth characteristic of the antenna is optimized using BPSO technique. The comparison results show that the 3.2% impedance bandwidth (4.63-4.78 GHz) of the patch antenna is upgrade to 10.4% (4.47-4.96 GHz) through the BPSO-IE3D method. The antenna gain is stable and the radiation patterns are similar in configuration over the whole operating frequencies to that of a conventional patch antenna. A prototype of the optimized antenna has been fabricated and important antenna parameters such as reflection coefficient (S11) parameter, gains and radiation patterns are measured using Network Analyzer and antenna test-bench. The measured values of the antenna parameters are found to match well with that of the simulated results, all of which illustrate that the method is valid and the antenna can operate well. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 54:434-438, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26552 [ABSTRACT FROM AUTHOR]