Search

This paper addresses the mechanisms of wideband power amplifiers’ efficiency degradation in comparison with their narrowband operation. It starts by identifying some possible causes for this performance degradation, showing that the baseband terminations are dominant. A detailed explanation for the efficiency degradation is then presented, considering the scenarios where the most important baseband components fall before or after the resonance imposed by the bias and matching networks. A theoretical model that is able to describe this performance degradation is also presented. Finally, the proposed theory is validated through two implemented power amplifiers with the same fundamental and harmonic terminations, but with different baseband networks, showing that an optimized bias network design can improve the efficiency performance of a PA. [ABSTRACT FROM AUTHOR]

In this paper, a new design concept of Schiffman phase shifters under the operation of the second phase period in frequency domain is presented and analyzed. By investigating phase properties of the C-section structure, we first find that its second phase period is another independent and distinctive working region for Schiffman phase shifter, in addition to its first phase period. In contrast to traditional counterparts working on the first phase period, which are suitable for small phase shift from 0° to 90°, the Schiffman phase shifters on the second phase period are suitable for the large phase shift from 90° to 180°. It is because of the opposite phase variation property that the electrical length of reference line gets shortened as the phase shift value increases. Compared with the first phase period, the second phase period can achieve wider phase shift bandwidth under the same coupling degree. This feature is believed to be very useful in the limited realizable coupling degree cases. In this context, the closed-form synthesis formulas of Schiffman phase shifter on the second phase period are presented. Meanwhile, detail theoretical analysis of the phase shift bandwidth and phase deviation is carried out. In final, two Schiffman phase shifters on the first and second phase periods are designed and fabricated to validate our proposed concept and approach in the experiment. [ABSTRACT FROM AUTHOR]

The conventional Doherty power amplifier (DPA) theory is limited to single carrier operations, leading to a nongeneric structure. This paper presents a new analysis that generalizes the conventional DPA (CDPA) theory for increased efficiency and bandwidth. We demonstrate that by introducing a theoretical parameter $\alpha$ at the output combiner, we can redefine the relationships among the output combiner elements for a greater level of design flexibility than it was possible in the CDPA. We also show that previously published works in this area can be considered as special cases of the proposed general theory. As a demonstrator, a specific design, named reduced- $\alpha$ DPA, realized using GaN HEMTs is provided to illustrate the robustness of the approach. This design proves effective for further improving the performance of the previously published 2.14-/2.655-GHz dual-band parallel DPA. A maximum drain efficiency of 84% and 67% at an average of 43-dBm peak and 6-dB back-off power levels, respectively, was measured with continuous wave signals. To quantify the linearity performance, the proposed DPA was tested using wideband CDMA and long-term evolution signals where the adjacent channel leakage ratio was recorded at −25 dBc with an average output power of 38.7 and 36.5 dBm at 2.14 and 2.655 GHz, respectively. [ABSTRACT FROM PUBLISHER]

In this paper, a novel terminated coupled line structure (TCLS) is introduced, which is constructed by a coupled line section and four terminations loaded on it. Introducing different kinds of terminations, three types of bandpass filters (BPFs) based on TCLSs are proposed, theoretically analyzed, and fabricated, including two single-ended wideband BPFs with fractional bandwidths (FBWs) of 67% and 40% respectively, and a wideband differential BPF with 74% differential-mode FBW. These BPFs can achieve wide passband bandwidth, low in-band insertion loss, high passband selectivity, as well as deep stopband rejection performance simultaneously, benefited from the multiple transmission zeros and transmission poles obtained by the TCLSs. The practical design procedures of these BPFs are presented and explained. The agreement among theoretical predictions, EM-simulated, and measured results validates our proposed filter structures. Finally, the generalized multistage filter topology based on TCLSs is proposed to design high-order filters with better filtering performances. [ABSTRACT FROM PUBLISHER]

This paper presents a V -band 1.2-V wideband power amplifier (PA) with a compact four-way radial power combiner in a 90-nm CMOS process. A transformer-based radial power combiner with a 1-dB insertion loss at 60 GHz and a 0.043-mm ^{\mathrm { {2}}} compact size is designed for high-output-power combining and wideband load-pull matching. This PA achieves the saturated output power ( P_{\mathrm { {SAT}}}) of 20.6 dBm, the maximum power-added efficiency ( \textit PAE\mathrm { {max}}) of 20.3%, and a 20.1-dB small-signal gain ( S\mathrm { {21}}) at 60 GHz. The PA maintains a flat 20-dBm P\mathrm { {SAT}} with \textit PAE\mathrm { {max}} better than 17.3% within 50–64 GHz, and it has a 3-dB bandwidth (BW) of 24.5 GHz (41.8–66.3 GHz). The chip area without pads is 0.432 mm ^\mathrm 2 . To the best of the author’s knowledge, this $V$ -band PA with a flat frequency response of 20-dBm P\mathrm { {SAT}} presents the widest large-signal BW (50–64 GHz) compared with the reported 60-GHz CMOS high-output PAs. [ABSTRACT FROM AUTHOR]

This paper presents a wideband vector-sum phase shifter (VSPS) that operates over the entire WR-3 band (220–320 GHz). Compared to conventional VSPSs with double Gilbert cells, the proposed phase shifter employs a single Gilbert-cell structure for vector modulation. This reduces the output current combining ratio from 8:2 to 4:2, and boosts the impedance at the combining node, thus facilitating wideband output matching at upper millimeter-wave and terahertz bands. The simplified structure leads to a reduction in dc power consumption and chip area without sacrificing the 360^\circ phase-shifting property. Lossy matching is applied at the Gilbert-cell output to further increase bandwidth and stability at the expense of relatively high loss. The phase shifter is implemented using a 250-nm InP DHBT technology that provides f T and f \max exceeding 370 and 650 GHz, respectively. The measurements exhibit a wideband phase shift with continuous 360^\circ coverage and average insertion loss ranging from 11.8 to 15.6 dB for the entire WR-3 band. The root mean square amplitude and phase error among different phase states are less than 1.2 dB and 10.2^\circ, respectively. The input-referred 1-dB compression is measured at \0.7 dBm on average. The dc power consumption is 21.8–42.0 mW at different phase states. [ABSTRACT FROM PUBLISHER]

In this paper, a dynamic stack-controlled CMOS FET RF power amplifier (PA) is developed to enhance the efficiency of the envelope tracking power amplifier (ET PA) system for low-voltage operation. The power cell used in the two-stage PA is a quadruple-stacked FET structure with dynamic stacking controller to reconfigure the power cell into the quasi-triple or quasi-double stacks according to the magnitude of the input envelope signal. The proposed power cell boosts the peak efficiency in the low VDD region by bypassing the stack entering the triode region and reoptimizing the load impedance so that all the FETs operate under the saturation and the optimum load conditions. A detailed analysis is presented to understand the gain and phase step discontinuities at the stack switching points, and the circuit techniques to equalize the gain and phase between the adjacent stack configurations are developed. The proposed two-stage stack-controlled PA is fabricated with a 0.32-\mu\ m silicon-on-insulator (SOI) CMOS process together with the envelope amplifier (EA). Full long-term evolution (LTE) characterization is performed using LTE signals with a peak-to-average power ratio (PAPR) of 6.7 dB and signal bandwidths (BW) of 10 and 20 MHz. With 10-MHz signals, dynamic stacking provides 3.5% power added efficiency (PAE) improvement over the static stack at 25.7 dBm, resulting in 47.5% PAE with 26.6-dB gain. A 20-MHz LTE test shows an overall PAE of 45.9% with an evolved universal terrestrial radio access (E-UTRA) adjacent channel leakage ratio (ACLR) of -33 dBc with memoryless digital predistortion. Even with the lower efficiency of the EA compared with the state-of-the-art results, the measured overall system efficiency with 3.4 V maximum voltage is comparable with those reported using GaAs HBT's with 5 V supplies, which clearly demonstrates the advantages of the proposed dynamic stack control. [ABSTRACT FROM AUTHOR]

This paper presents an innovative architecture to drastically enlarge the bandwidth of the Doherty power amplifier (DPA). The proposed topology, based on novel input/output splitting/combining networks, allows to overcome the typical bandwidth limiting factors of the conventional DPA. A complete and rigorous theoretical investigation of the developed architecture is presented leading to a closed-form formulation suitable for a direct synthesis of ultra-wideband DPAs. The theoretical formulation is validated through the design, realization, and test of a hybrid prototype based on commercial GaN HEMT device showing a fractional bandwidth larger than 83%. From 1.05 to 2.55 GHz, experimental results with continuous-wave signals have shown efficiency levels within 83%–45% and within 58%–35% at about 42- and 36-dBm output power, respectively. The DPA has also been tested and digitally predistorted by using a 5-MHz Third Generation Partnership Project (3GPP) signal. In particular, to evaluate the ultra-wideband and the multi-mode capabilities of the prototype, f1 =1.2~{\GHz}, f 2 =1.8~{\GHz}, and f 3 =2.5~{\GHz} have been selected as carrier frequencies for the 3GPP signal. Under these conditions and at 36-dBm average output power, the DPA shows 52%, 35%, and 52% efficiency and an adjacent channel power ratio always lower than -\43 dBc. [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]

Two new wideband in-phase and out-of-phase balanced power dividing/combining networks are proposed in this paper. Based on matrix transformation, the differential-mode and common-mode equivalent circuits of the two wideband in-phase and out-of-phase networks can be easily deduced. A patterned ground-plane technique is used to realize the strong coupling of the shorted coupled lines for the differential mode. Two planar wideband in-phase and out-of-phase balanced networks with bandwidths of 55.3% and 64.4% (\vert S{ dd21,31}\vert<4\ {\ {dB}}) for the differential mode with wideband common-mode suppression are designed and fabricated. The theoretical and measured results agree well with each other and show good in-band performances. [ABSTRACT FROM PUBLISHER]

In this paper, a novel terminated cross-shaped resonator (TCSR) is analyzed and used to design ultra-wideband (UWB) bandpass filters (BPFs) with fixed and reconfigurable notch bands. It is found that the TCSR can exhibit a maximum three poles and two zeros when open and short terminations are applied. The intrinsic zero is simply used for the implementation of notch bands offering systematic design and flexible tuning capabilities. Bandwidth can also be kept unchanged when tuning a notch within the UWB passband. In contrast to common band-notched UWB BPFs using additional notch resonators, only a single TCSR is required to realize band-notched UWB filters. Three UWB BPF prototypes, including a four-pole filter with 94.7% fractional bandwidth (FBW) and a notch band at 5.8 GHz, a five-pole filter with 111% FBW and dual notch bands at 4.3/9.1 GHz, and a four-pole filter with 82.4% FBW and reconfigurable notch band from 4.6 to 6.5 GHz are designed and experimentally characterized. Their experimental characterizations are in good agreement with theoretical analysis validating a simple approach of band-notched UWB BPF design. [ABSTRACT FROM AUTHOR]

This paper presents a new class of dual-, tri- and quad-band BPF by using proposed open stub-loaded shorted stepped-impedance resonator (OSLSSIR). The OSLSSIR consists of a two-end-shorted three-section stepped-impedance resistor (SIR) with two identical open stubs loaded at its impedance junctions. Two 50-\Omega tapped lines are directly connected to two shorted sections of the SIR to serve as I/O ports. As the electrical lengths of two identical open stubs increase, many more transmission poles (TPs) and transmission zeros (TZs) can be shifted or excited within the interested frequency range. The TZs introduced by open stubs divide the TPs into multiple groups, which can be applied to design a multiple-band bandpass filter (BPF). In order to increase many more design freedoms for tuning filter performance, a high-impedance open stub and the narrow/broad side coupling are introduced as perturbations in all filters design, which can tune the even- and odd-mode TPs separately. In addition, two branches of I/O coupling and open stub-loaded shorted microstrip line are employed in tri- and quad-band BPF design. As examples, two dual-wideband BPFs, one tri-band BPF, and one quad-band BPF have been successfully developed. The fabricated four BPFs have merits of compact sizes, low insertion losses, and high band-to-band isolations. The measured results are in good agreement with the full-wave simulated results. [ABSTRACT FROM PUBLISHER]

This paper proposes a multistage transformer-feedback-based design approach for a high fractional-bandwidth (fBW) IF stage in a 60-GHz heterodyne receiver. An in-depth analysis of source-to-gate transformer-feedback amplifiers, including the design of the matching network, is presented. Analytic expressions for the input resistance, quality factor, and noise figure (NF) as a function of the transformer turns-ratio (n) and magnetic coupling factor (k) are derived. To validate the proposed analysis, a wideband IF amplifier and mixer were designed in a 40-nm CMOS process. From measured results, this device achieves a 16% -3-dB fBW, a peak power gain of 27.6 dB, an NF of 5.3 dB while consuming 28.8 mW from a 0.9-V supply. [ABSTRACT FROM AUTHOR]

In this paper, a novel miniaturization method for filter implementation is presented and validated. According to frequency response transformation, the filter structure has the wideband bandpass response in the required frequency band which is lower than the operation frequency. The in-band and out-of-band characteristics are also improved to realize wide passband and stopband responses. For demonstration, three filters are designed based on the proposed ideas. The efficient circuit area is reduced by 56.8%–64.7% compared with the conventional wideband filter, indicating significant miniaturization using the proposed method. Another advantage of our work is that the stopband is extended to more than 9f0 than other wideband filter structures. Good agreement between simulation and experiment is obtained. [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]

A wideband common-gate (CG) low-noise amplifier (LNA) utilizing positive-negative-feedback technique is presented. The positive-negative-feedback technique boosts effective transconductance (Gm) and output impedance, which leads to an LNA with higher gain and lower noise figure (NF) over the previously reported amplifiers. In addition, this approach provides high linearity with an aid of third harmonic cancellation, and it breaks transconductance (gm) constriction for input matching in CG amplifiers. In this paper, linearity and output impedance improvement through the proposed technique are fully analyzed. An LNA prototype is implemented in 0.18- μm CMOS technology occupying a total area of 0.33 mm2. The implemented LNA delivers a maximum voltage gain of 21 dB, a minimum NF of 2 dB, an third-order intermodulation intercept point of -3.2 dBm, and 3.6 mW of power consumption in 300-920 MHz of 3-dB bandwidth with input matching (S11 <; -10 dB). [ABSTRACT FROM PUBLISHER]

A methodology for the design of multichannel, wideband, highly efficient hybrid Class-J power amplifiers for fourth–generation (4G) communication transmitters is proposed. The design procedure is based on the automatic generation and evaluation of a vast number of output matching networks of the same topology but different dimensions, with respect to efficiency, output power, and linearity. The approach can find application in the management of the efficiency/linearity/bandwidth tradeoff in amplifier design. In this paper, two matching network architectures have been considered. One multistubbed network and a stepped-impedance microstrip line network. The approach has been validated through the design, simulation, and measurement of two power amplifiers realized using the aforementioned procedure. The first amplifier covers 1.6–2.2 GHz (31.6% fractional bandwidth) with 55%–68% drain efficiency at the 2-dB compression point and worst case adjacent channel power ratio (ACRP) and error vector magnitude (EVM) of -\ 21.8 dBc and 8.35%, respectively, over the bandwidth. The second covers 0.5–1.8 GHz (113% fractional bandwidth) with 50%–69% drain efficiency at the 2-dB compression point and worst case ACRP of -\ 27.5 dBc and EVM of 4.22%. Both amplifiers are based on a commercial, packaged 10-W GaN HEMT transistor. [ABSTRACT FROM AUTHOR]

Two novel wideband differential bandpass filters based on a T-shaped structure are proposed in this paper. Broad passband and wideband harmonic suppression for the differential/common mode can be easily achieved for the wideband differential filter without cross coupling, due to the controlled resonator frequencies of the shorted/open T-shaped structure. In addition, another more compact differential filter using cross coupling is proposed with two transmission zeros close to the passband to improve the selectivity for the differential mode. To verify the presented concept, two prototypes (\varepsilon r = 2.65, h = 0.5~\ mm) with 3-dB fractional bandwidth of 70% and 70.7% for the differential mode and insertion loss greater than 13.5 dB for common mode (0–19 GHz) are designed and fabricated. Good agreement can be observed between measured results and theoretical expectations. [ABSTRACT FROM AUTHOR]

This paper presents a new design method for reconfigurable coupled line filters. The main aim is to develop an analytical design procedure for designing this type of reconfigurable filter with any orders and bandwidths. The new design procedure allows not only making the design easy, but also increasing the passband performance by eliminating the impedance transformers needed for matching purposes used in previous filters. A reconfigurable bandpass filter of this type is designed that can switch between three distinct bandwidth states ranging from around 26% to 50% ripple fractional bandwidth (FBW) centered at 2 GHz. In addition, liquid crystal polymer (LCP) multilayer circuit technology, which offers a great flexibility in realizing required even- and odd-mode impedances for a wideband coupled line filter, is deployed to implement the designed filter. The reconfigurable filter exhibits insertion losses ranging from 0.57 dB for the widest passband state to 1.95 dB for the narrowest passband state. The fabricated filter shows good agreement with EM simulated results. [ABSTRACT FROM PUBLISHER]

A novel wideband receiver RF front-end, including a resistive negative feedback wideband low-noise amplifier (LNA) with feedforward noise and distortion cancellation and a current commutating down conversion passive mixer with biquad trans-impedance amplifier, is presented in this paper. In comparison to conventional resistive negative feedback LNAs, theory analysis and experimental results for the proposed LNA circuit shows improved performance parameters, including voltage gain, noise figure (NF), and input-referred third-order intercept point (IIP3), especially helpful for wideband LNA design in modern deep-submicrometer CMOS. A wideband receiver RF front-end fabricated in 0.13-\mu\m CMOS, based on the proposed feedforward noise and distortion-cancellation resistive-feedback LNA, has 42–48-dB conversion gain with 0.8–12-MHz tunable IF -3-dB bandwidth and 12-dB adjacent channel selectivity at 2fp, -14-dBm IIP3, and 3-dB NF double-sideband with 10-kHz flicker-noise corner frequency. [ABSTRACT FROM AUTHOR]

This paper presents a new design of wide slot antenna for various wideband applications. The proposed printed antenna consists of a slot and a turning stub, both formed by a binomial curve function; thus, various bandwidths (BWs) can be obtained based on the structure with different binomial curves. Some key parameters affecting the antenna performance have been analyzed and discussed in detail as an antenna design guideline. To validate the theoretical design, six prototypes of various binomial-curved slot antennas were designed, fabricated, and measured. Good agreement between the simulated results and the measured ones is observed. The results demonstrate that the proposed type of antenna can obtain a BW range from 9.8% to 99.7% for VSWR \leq 2 by selecting various binomial-curved slots, which may provide a convenience for various wideband antenna designs. Moreover, the proposed type of antenna owns a simple structure and a stable gain of about 3–5.5 dBi, which is very suitable for wideband wireless system applications. [ABSTRACT FROM AUTHOR]

In the above paper two equivalent circuits of $L_{T}-$ and $\Pi $ -types for a 90° transmission-line section (TL) are suggested only for $N = 1$. However, the design formulas for $N= n$ , where $n\ge 1$ and integer, are already published for $L_{T}$ -types and for $\Pi $ -types [3, Fig. 6(c) with $\Theta _{a}= 0^{\circ }$ ], , and the advantages for $N \ge 2$ are verified for $L_{T}$ -types in and $\Pi $ -types , , as well. [ABSTRACT FROM AUTHOR]