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This paper addresses the estimation and compensation of I/Q imbalance, one of the most prominent impairments found in wideband zero-intermediate frequency transceivers (TRxs). The I/Q imbalance encountered in this kind of TRx comprises not only frequency-selective gain and phase imbalance but also delay imbalance. Unless appropriate compensation is applied, the I/Q imbalance significantly degrades the performance of a communication system. This paper presents a novel compensation technique for transmitter I/Q imbalance based on built-in-self-calibration, a low cost and robust compensation technique that enables manufacturing as well as in-field calibration with low computational complexity. The method's performance is evaluated in a TRx with 64-quadratic-amplitude modulation and 2 GHz of bandwidth implemented with real hardware. The measurements show that the proposed technique achieves an image rejection ratio greater than 35 dB in the entire 2 GHz bandwidth and an error vector magnitude lower than 3%. [ABSTRACT FROM AUTHOR]

This paper addresses the estimation and compensation of I/Q imbalance, one of the most prominent impairments found in wideband zero-intermediate frequency transceivers (TRxs). The I/Q imbalance encountered in this kind of TRx comprises not only frequency-selective gain and phase imbalance but also delay imbalance. Unless appropriate compensation is applied, the I/Q imbalance significantly degrades the performance of a communication system. This paper presents a novel compensation technique for transmitter I/Q imbalance based on built-in-self-calibration, a low cost and robust compensation technique that enables manufacturing as well as in-field calibration with low computational complexity. The method’s performance is evaluated in a TRx with 64-quadratic-amplitude modulation and 2 GHz of bandwidth implemented with real hardware. The measurements show that the proposed technique achieves an image rejection ratio greater than 35 dB in the entire 2 GHz bandwidth and an error vector magnitude lower than 3%. [ABSTRACT FROM PUBLISHER]

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]

This paper reports an area-efficient and tunable bandwidth (BW)-extension technique for a wideband CMOS amplifier to handle very high rate (50+ Gb/s) signaling while keeping a low jitter penalty. We identify its architectural advantages by correlating the performances with the frequency domain (magnitude and group delay (GD) responses) and time domain (impulse and step responses) and comparing them with the existing solutions. Specifically, our technique enables a flexible ac characteristic by introducing a tunable grounded active inductor in the bridged-shunt peaking topology, offering: 1) a high BW enhancement ratio (BWER = $2.65\times$ ); 2) BW-power scalability with small in-band gain variation; and 3) fine tunability of the passband gain without affecting the BW, GD, and power. The experimental prototype is a 65-nm CMOS four-stage differential amplifier occupying just 0.0077 mm2. It delivers a 15-dB gain over a 43-GHz BW with 45-mW power consumption. Small in-band gain variation (0.58 dB) and ripple (1.53 dB) are concurrently achieved with low in-band GD variation (17 to 35.3 ps) and ripple (18.3 ps). The achieved figure of merit of 5.48 [(dc Gain $\times$ BW)/Power] compares favorably with the prior art. [ABSTRACT FROM AUTHOR]

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 demonstrates the feasibility of very compact and broadband square waveguide bends able to transmit both linear and circular polarizations. A careful control of the bend profile for dual-linear polarization or the use of a new septum-polarizer-like geometry for dual-circular polarization allows to reach full band operation ~34% in the first case and broadband operation ~20% for the second application. Experimental validations show excellent agreement with the theoretical predictions thus effectively extending the previous bandwidth limitations. [ABSTRACT FROM PUBLISHER]

Three novel wideband balanced-to-unbalanced filtering power dividers based on coupled lines are proposed in this paper. Multifunctional power dividers can replace various cascaded single devices to decrease integration mismatching loss and circuit size. The wideband response can be easily realized by the coupled lines structures. To further improve the differential-mode passband selectivity, open/shorted coupled lines and half-wavelength open stubs are applied to introduce two transmission zeros near the passband, respectively. In addition, a resistor in the middle of two single-ended ports can be used to realize isolation between out ports. To verify the proposed concepts, three prototypes of wideband balanced-to-unbalanced filtering power dividers operating at 2 GHz are designed and fabricated with the 4-dB differential-mode bandwidths of 80.5%, 71.5%, and 80%. All the structures show good performances for differential-mode out-of-band suppression, common-mode suppression, and isolation. [ABSTRACT FROM PUBLISHER]

This paper reports a new measurement method for wideband radiofrequency power amplifier (PA) characterization and digital predistortion. The proposed measurement procedure significantly relaxes the sampling rate requirement on the analog-to-digital converters of the feedback path. Successful PA linearizations were achieved in the presence of 20, 40, and 60-MHz LTE-A signals using a vector signal analyzer with sampling speeds equal to only 24, 40.96, and 61.44 Ms/s, respectively. Despite these very low sampling rates, a quasiperfect cancellation of the PA distortions was achieved (more than 50 dBc in terms of ACLR), in all tests, over bandwidths including up to fifth-order intermodulation distortions. Such a correction bandwidth is much wider than the observation bandwidths associated with the receiver sampling rates. [ABSTRACT FROM PUBLISHER]

This paper presents a highly symmetric 1\! :\! n concentric vortical transformer (CVT) technology, which can be implemented with slab inductors. The CVT and several widely used planar transformer structures are analyzed to show the characteristic distinction of the CVT. The proposed CVT was developed in an integrated passive device technology along with the popular distributed active transformer (DAT) for comparison. Under the same real-part impedance transformation ratio at 2.4 GHz, the outer diameter of the CVT is only 48% of the DAT. Moreover, 89.4% transformation efficiency and 191% - \1-dB fractional bandwidth are achieved by the CVT from a high coupling coefficient of 0.9. The symmetric nature of the CVT makes it capable of achieving far less variation than the DAT in resistance and reactance among multiple input ports when used for power combining. [ABSTRACT FROM PUBLISHER]

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]

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]

The continuously increasing demand for wide bandwidth creates great difficulties in employing digital predistortion (DPD) for radio frequency (RF) power amplifiers (PAs) in future ultra-wideband systems because the existing DPD system requires multiple times the input signal bandwidth in the transmitter and receiver chain, which is sometimes almost impossible to implement in practice. In this paper, we present a novel band-limited digital predistortion technique in which a band-limiting function is inserted into the general Volterra operators in the DPD model to control the signal bandwidth under modeling, which logically transforms the general Volterra series-based model into a band-limited version. This new approach eliminates the system bandwidth constraints of the conventional DPD techniques, and it allows users to arbitrarily choose the bandwidth to be linearized in the PA output according to the system requirement without sacrificing performance, which makes the DPD system design much more flexible and feasible. In order to validate this idea, a high-power LDMOS Doherty PA excited by various wideband signals, including 100-MHz long-term evolution advanced signals, was tested. Experimental results showed that excellent linearization performance can be obtained by employing the proposed approach. Furthermore, this technique can be applied to other linear-in-parameter models. In future ultra-wideband systems, this new technique can significantly improve system performance and reduce DPD implementation cost. [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]

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 wideband transformer-coupled CMOS power amplifier (PA). On-chip transmission-line transformers are used as key components of matching networks at output, input, and interstage. The wideband on-chip transformer is harnessed without any additional inductive devices so that a wideband power characteristic can be achieved. The PA is fabricated using a 0.18-\mu\ m CMOS process. It provides a saturated output power of 21.5 dBm with the power-added efficiency (PAE) of 20.3%, and the output 1-dB gain-compressed power (P1\ {dB}) is 20.2 dBm with the PAE of 14.8% at 9.5 GHz, respectively. The small-signal gain is 25.3 dB and the 3-dB bandwidth is 6.5 GHz (6.5–13 GHz). The die area is 1.34 mm \times 0.47 mm. Among the reported X/Ku-band CMOS PAs, this amplifier achieves the highest figure of merit, and also shows suitable performances for phased-array systems. [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]

This paper presents a 20–32-GHz wideband BiCMOS mixer with an IF bandwidth of 12 GHz. The mixer utilizes an inductive peaking technique to extend the bandwidth of the downconverted IF signal. To our knowledge, the proposed mixer achieves the widest IF bandwidth using silicon-based technologies in K-band. Analytical expressions for the conversion gain and output noise of the proposed mixer are presented. The wideband mixer is implemented using 0.18-\mu\ m BiCMOS technology and occupies an area of 0.19 \ mm^2. It achieves a conversion gain of 3 dB, a noise figure between 10.5 and 13.0 dB, and an IIP3 higher than 0.5 dBm with a power consumption of 18 mW from a 1.8-V supply. [ABSTRACT FROM PUBLISHER]

This paper presents the design and implementation of a low power wideband mixer for multistandard receivers, covering global system for mobile communications, universal mobile telecommunications system, wireless local area network, Bluetooth, and ultra-wideband. The circuit topology is based on the folded technique with a current reuse shunt feedback RF input stage operating at a low supply voltage of 1 V. The mixer offers a peak gain of 12.8 dB, a 3-dB bandwidth from 1 to 10.5 GHz, and a minimum double-sideband noise figure of 7.6 dB. The input referred compression point is better than -15 dBm with an output referred intercept point of better than 5.75 dBm over the entire bandwidth. The mixer circuit was fabricated in a 65-nm standard CMOS process and draws 5 mA of dc current, leading to a power dissipation of only 5 mW. Gain and noise performance can be further increased when operating at nominal supply voltage of 1.2 V at the expense of an increasing power dissipation. [ABSTRACT FROM AUTHOR]