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Microwave Theory and Techniques, IEEE Transactions on

Issue 9 • Date Sept. 2013

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Displaying Results 1 - 25 of 42
  • Table of contents

    Page(s): C1 - C4
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  • IEEE Transactions on Microwave Theory and Techniques publication information

    Page(s): C2
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  • Properties and Numerical Solutions of Dispersion Curves in General Isotropic Waveguides

    Page(s): 3161 - 3168
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1858 KB) |  | HTML iconHTML  

    In this paper, some properties of dispersion curves in general isotropic piecewise homogeneous waveguides are rigorously derived. These properties are leveraged in a numerical implementation capable of determining the dispersion curves of such waveguides with cross-section materials that can be highly conductive (such as copper). In a numerical example, the influence of a lossy shielding conductor on the complex modes of a shielded dielectric image guide is investigated for the first time. View full abstract»

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  • Below-Cutoff Propagation in Metamaterial-Lined Circular Waveguides

    Page(s): 3169 - 3178
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    This paper investigates the propagation characteristics of circular waveguides whose interior surface is coated with a thin metamaterial liner possessing dispersive, negative, and near-zero permittivity. A field analysis of this system produces the dispersion of complex modes, and reveals in detail intriguing phenomena such as backward-wave propagation below the unlined waveguide's fundamental-mode cutoff, resonant tunneling of power, field collimation, and miniaturization. It is shown how the waveguide geometry and metamaterial parameters may be selected to engineer the lined waveguide's spectral response. Theoretical dispersion and transmission results are closely validated by full-wave simulations. View full abstract»

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  • Exact Cutoff Wavenumbers of Composite Elliptical Metallic Waveguides

    Page(s): 3179 - 3186
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    The cutoff wavenumbers of eccentric nonconfocal elliptical metallic waveguides are calculated in this paper. The solution is obtained using expansions in terms of the elliptical wave functions, in combination with the related addition theorem. The method presented here is exact, and allows the study of more complex elliptical waveguide geometries, like rotated elliptical interfaces arbitrarily placed inside the outer elliptical interface, or studies for possible change of the operational bandwidth. The solution is validated compared with other published results from the literature. The known problem of an elliptical metallic waveguide loaded by a concentric nonconfocal strip is revisited and discrepancies noticed by other authors are justified. Numerical results are presented for the cutoff wavenumbers for various composite elliptical waveguides for both TM and TE modes. View full abstract»

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  • Compact Microstrip Dual-/Tri-/Quad-Band Bandpass Filter Using Open Stubs Loaded Shorted Stepped-Impedance Resonator

    Page(s): 3187 - 3199
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    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- Ω 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. View full abstract»

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  • Tunable Bandpass Filter With Independently Controllable Dual Passbands

    Page(s): 3200 - 3208
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    This paper presents a two-pole dual-band tunable bandpass filter (BPF) with independently controllable dual passbands based on a novel tunable dual-mode resonator. This resonator principally comprises a λ/2 resonator and two varactor diodes. One varactor is placed at the center of the resonator to determine the dominant even-mode resonant frequency; the other is installed between two ends of the resonator to control the dominant odd-mode resonant frequency. These two distinct odd- and even-mode resonances can be independently generated, and they are used to realize the two separated passbands as desired. Detailed discussion is carried on to provide a set of closed-form design equations for determination of all of the elements involved in this tunable filter, inclusive of capacitively loaded quarter-wavelength or λ/2 resonators, external quality factor, and coupling coefficient. Finally, a prototype tunable dual-band filter is fabricated and measured. Measured and simulated results are found in good agreement with each other. The results show that the first passband can be tuned in a frequency range from 0.77 to 1.00 GHz with the 3-dB fractional-bandwidth of 20.3%-24.7%, whereas the second passband varies from 1.57 to 2.00 GHz with the 3-dB absolute-bandwidth of 120 ± 8 MHz. View full abstract»

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  • Shorted-Ended Stepped-Impedance Dual-Resonance Resonator and Its Application to Bandpass Filters

    Page(s): 3209 - 3215
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    In this paper, a short-ended stepped-impedance dual-resonance resonator is presented. Analysis of its resonance characteristics is carried out, from which the design graph is given. By controlling the impedance and length ratios of the resonator, for the first time, the first three pairs of resonant modes corresponding to three passbands within a single resonator can be controlled freely in a wide reasonable range. First, a bandpass filter (BPF) with the first spurious occurring at 4.2 f0 is designed. Second, in the dual-/tri-band BPFs design, according to the voltage distributions along the resonator, the feedlines with two arms supply the needed external coupling for the two/three passbands simultaneously, and good impedance matching can be achieved in each passband. Lastly, three filters with one, two, and three passbands are fabricated and measured, which show good agreement with the simulated results. View full abstract»

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  • CAD Procedure for High-Performance Composite Corrugated Filters

    Page(s): 3216 - 3224
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    The design of waveguide low-pass filters is accomplished with a new method, where focus is on the upper stopband performance rather than passband or roll-off requirements. Using an efficient multimode variational formulation, composite filters are generated by direct optimization from an arbitrary number of partial corrugated subelements, each showing mutual TE10-mode passband and different nonintersecting passbands corresponding to higher order modes. The flexibility of this method leads to optimal filter solutions, having the designer full control over key dimensional features, i.e., minimum gap and cavity length. It is therefore possible to design low-pass filters exhibiting broad stopbands free of spurious propagation, without penalties of higher losses, lower power handling capability, larger size, and/or increased manufacturing complexity. Simulated and measured results demonstrate significant advantages over filters designed with conventional methods. View full abstract»

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  • Multi-Frequency Impedance Transformers for Frequency-Dependent Complex Loads

    Page(s): 3225 - 3235
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2653 KB) |  | HTML iconHTML  

    In this paper, a general synthesis method is proposed for the design of multi-frequency impedance transformers (MFITs) for arbitrary frequency-dependent complex loads (FDCLs) by adopting the concept of multi-frequency inverters (MFIs). An MFI, which is placed between two susceptance blocks, is constructed with a transmission line and two-side multi-frequency susceptances (MFSs), whose values at multiple frequencies are independently specified. By merging neighboring susceptances, we get a very simple Pi-shaped topology of MFITs, which in theory has no limitation on the number of matching frequencies. The MFS blocks are realized with one or more parallel shunt stubs, providing needed susceptance values at several specified frequencies. A genetic algorithm is used in extracting the circuit parameters of the parallel stubs. Several dual-, triple-, and quad-frequency impedance transformers for FDCLs are designed for illustrating the design methods. Experiment and simulation results are compared with good agreement, validating the feasibility of the theory. The designed impedance transformers are concise in circuit and compact in dimensions. View full abstract»

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  • High-Directivity MEMS-Tunable Directional Couplers for 10–18-GHz Broadband Applications

    Page(s): 3236 - 3246
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    This paper reports on two novel concepts of area-efficient ultra-wideband microelectromechanical systems (MEMS) reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. Concept 1 is based on symmetrically changing the geometry of the ground coupling of each signal line, while Concept 2 is simultaneously varying both the ground coupling and the coupling between the two signal lines. This enables uniform and well predictable performance over a very large frequency range, in particular a constant coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity. For an implemented micromachined prototype 3-6-dB coupler based on Concept 1, the measured isolation is better than 16 dB, and the return loss and directivity are better than 10 dB over the entire bandwidth from 10 to 18 GHz. Concept 2 presents an even more significant improvement. For an implemented 10-20-dB prototype based on Concept 2, the measured isolation is better than 40 dB and the return loss is better than 15 dB over the entire bandwidth from 10 to 18 GHz for both states. The directivities for both states are better than 22 and 40 dB, respectively, over the whole frequency range. The measured data fits the simulation very well, except for higher through-port losses of the prototype devices. All devices have been implemented in a silicon-on-insulator RF MEMS fabrication process. Measured actuation voltages of the different actuators are lower than 35 V. Reliability tests were conducted up to 500 million cycles without device degradation. View full abstract»

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  • An In-Phase Output K!a -Band Traveling-Wave Power Divider/Combiner Using Double Ridge-Waveguide Couplers

    Page(s): 3247 - 3253
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    A Ka-band traveling-wave power divider/combiner, which is based on double ridge-waveguide couplers, is presented. The in-phase output, which is a challenge of the waveguide-based traveling-wave power divider, is achieved by optimizing the equivalent circuit of the proposed structure. The novel ridge-waveguide coupler has advantages of low loss, high power capability, and easy assembly. Finally, the proposed power divider/combiner is simulated, fabricated, and measured. A 15-dB measured return-loss bandwidth at the center frequency of 35 GHz is over 28%, a maximum transmission coefficients amplitude imbalance of ±1 dB is achieved, and the phase deviation is less than ± 12° from 32 to 39 GHz. View full abstract»

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  • Theory and Design of Intrinsically Switched Multiplexers With Optimum Phase Linearity

    Page(s): 3254 - 3264
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    This paper presents the theory, design, and implementation of a new class of component called an intrinsically switched multiplexer, which is comprised of a number of contiguous bandpass filter channels that can be independently switched on and off with very low architecture-related insertion loss and flat group delay across adjacent switched-on channels. Coupled-resonator filter topologies are identified that allow for optimum performance of contiguous bandpass channel filters through the crossover frequencies, and a new intrinsically switched coupling section that provides for low on-state insertion loss and high broadband off-state isolation is presented. In addition, it is shown that the channel filters can be combined in a scalable fashion with the use of lossy manifolds. A three-channel eight-state intrinsically switched multiplexer microstrip prototype was designed, built, and tested and gives 6.7 dB of passband insertion loss and 0.15-ns p-p group delay ripple over 72% of the passband. View full abstract»

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  • Analysis of Drain-Current Nonlinearity Using Surface-Potential-Based Model in GaAs pHEMTs

    Page(s): 3265 - 3270
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    In this paper, we present a physics-based model for accurate simulation of intermodulation distortion (IMD) in GaAs pseudomorphic HEMTs at 2 GHz. We combine the surface-potential-based drain-current model previously developed by us with the standard topology used in these devices for accurate nonlinear simulations. The proposed model is in excellent agreement with measured IMD data at multiple dc bias points varying from close-to cutoff voltage to the high-conduction region. We also analyze the impact of various model elements and physical effects on IMD behavior of the device. Furthermore, the popular Volterra series coefficients for the drain current nonlinearity are analyzed and their relative importance with respect to the overall device nonlinearity is assessed. View full abstract»

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  • A Negative Feedback Looped Voltage-Controlled Ring Oscillator With Frequency Voltage Converter

    Page(s): 3271 - 3276
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    This paper proposes a negative feedback looped voltage-controlled ring oscillator (VCRO) with a frequency voltage converter (FVC) to suppress the phase noise. Measurement results of the negative feedback looped VCRO fabricated in a one-poly six-metal 1.8-V 0.18- μm CMOS process show that the phase noises are -90, -90, -94, -102, and -110 dBc/Hz at 1-kHz, 10-kHz 100-kHz, 1-MHz, and 10-MHz offset from 922.9-MHz output frequency, respectively. The proposed negative feedback looped VCRO reduces the phase noise of a conventional VCRO by 35 ~ 8 dB from 1 kHz to 1 MHz. Measurement results show that the FVC can be combined with various VCRO and LC voltage-controlled oscillator architectures in a negative feedback loop to improve their phase-noise characteristic further. View full abstract»

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  • A Unified Method for the Analysis of Phase and Amplitude Noise in Electrical Oscillators

    Page(s): 3277 - 3284
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    This paper describes a unified method to quantify and compare amplitude and phase noise induced by white and colored noise sources in electrical oscillators. The proposed approach relies on the Floquet theory of linear time-varying systems and on the application of averaging techniques to simplify the stochastic equations. Closed-form expressions for the phase and amplitude power spectrum are provided. These results are validated via comparisons with SpectreRF simulations and measurements. View full abstract»

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  • Noise Measurements of Discrete HEMT Transistors and Application to Wideband Very Low-Noise Amplifiers

    Page(s): 3285 - 3297
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    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- Ω 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. View full abstract»

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  • Impact of Nonlinear C_{bc} on HBT Doherty Power Amplifiers

    Page(s): 3298 - 3307
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    Theoretically, the load modulation of carrier amplifiers in Doherty power amplifiers (PAs) achieves a 3-dB higher gain and a higher power-added efficiency (PAE) at a 3-dB back-off power due to the two times larger load impedance (2Ropt), compared to those at the peak power. In this paper, we analyze the impact of nonlinear Cbc on the gain behavior of heterojunction bipolar transistors (HBT) that shows nearly identical gain and a lower PAE with 2Ropt. In the environment, the gain distribution of carrier and peaking amplifiers is explained for the linear operation of the Doherty PA with the imperfect load modulation. We also explore harmonic controls for the Doherty PA using class-F matching network to enhance efficiency at a given back-off power and propose a method using a second-harmonic short circuit at the input of the carrier amplifier to compensate for the signal distortion caused by nonlinear Cbc. To validate the efficiency improvement while achieving high linearity, a Doherty PA is fabricated and tested using a long-term evolution signal having a 10-MHz bandwidth and a 16-quadrature amplitude modulation (16-QAM) 7.5-dB peak-to-average power ratio. The proposed Doherty PA achieves a PAE of 45% and an adjacent channel leakage ratio of -34 dBc at an average output power of 29 dBm. The total consumed power of the proposed PA at this output power represents a reduction by 4.5% and 29%, respectively, to that of a conventional class-F-type Doherty and a class-AB PA. View full abstract»

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  • A Doherty Architecture With High Feasibility and Defined Bandwidth Behavior

    Page(s): 3308 - 3317
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    This paper presents a complete and rigorous theoretical investigation of a Doherty architecture with a novel output combining network. The benefits in terms of bandwidth and feasibility held by the proposed topology are investigated and compared with the conventional one. In particular, the theoretical analysis demonstrates that the proposed output combiner allows to implement a Doherty amplifier with defined bandwidth (narrower or broader) without worsening in performances. Moreover, the proposed solution results in a more feasible structure with respect to the classical one, especially when high output power levels are sought. The theoretical results are validated through the design and realization of a prototype based on commercial GaN active devices. Experimental results show 42-dBm output power and 65% peak efficiency with a flat behavior in the 1.95-2.25-GHz frequency band (i.e., 14% of relative bandwidth) under continuous wave signal. Moreover, 50% average efficiency at 38-dBm average output power with -45 dBc of adjacent channel power ratio is demonstrated under 5-MHz 3GPP driving signal using a simple polynomial digital pre-distortion. View full abstract»

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  • An Extended-Bandwidth Three-Way Doherty Power Amplifier

    Page(s): 3318 - 3328
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    This paper expounds a three-way Doherty power amplifier (3W-DPA) as a solution to the need for high-efficiency wideband power amplifiers when driven by multi-standard signals. The paper begins with a theoretical analysis of 3W-DPA architecture from which the governing equations are derived. This analysis enables the identification of circuit parameters for maximizing bandwidth. A comprehensive methodology was devised to address the practical design challenges resulting from the transistor nonidealities: nonlinear input capacitance, transistor package, and output capacitance. Based on this methodology, a fully analog 30-W 3W-DPA was designed and implemented using GaN packaged transistors. The 3W-DPA prototype maintained an average drain efficiency of 55% at an output back-off of up to 9 dB, over the frequency range of 0.73-0.98 GHz. The 3W-DPA was successfully linearized when driven with 20-MHz four-carrier wideband code division multiple access (WCMDA) signals. 830- and 900-MHz power-added efficiencies of 47% and 53% was achieved at 32- and 35-dBm average output power, corresponding to a peak-to-average power ratio of 11.7 and 7.14 dB, respectively. View full abstract»

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  • High-Efficient Hybrid Buck Converter With Switch-on-Demand Modulation and Switch Size Control for Wide-Load Low-Ripple Applications

    Page(s): 3329 - 3338
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2342 KB) |  | HTML iconHTML  

    Considering the tradeoff between efficiency and output ripple over a wide load range, a monolithic dc-dc buck converter with switch-on-demand modulation (SODM) and switch size control (SSC) is presented in this paper. SODM achieves a hybrid mode of pulse skip and pulse width modulation (PWM) without mode detection circuit. The converter's on time is adaptively adjusted with the load demand, achieving low output voltage ripple. Detecting the output of the error amplifier by a comparator, the SSC circuit can select appropriate switch size according to load current for reducing switching loss in a light load. The threshold level of the comparator varies with respect to the amount of slope compensation, which maintains a substantially constant switch size changing point. Experimental results show that the fabricated converter with the proposed scheme achieves high efficiency from 83% to 96% over a wide load range from 10 mA to 5 A. The switch size is 1/4 of the maximum value when load current is below 1 A with 0.5-A hysteresis. Also, the measured maximum output ripple is less than 10 mV. View full abstract»

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  • A 0.7–2.7-GHz Blocker-Tolerant Compact-Size Single-Antenna Receiver for Wideband Mobile Applications

    Page(s): 3339 - 3349
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    Passive-mixer-first receivers have recently demonstrated flexible, low-noise, and high-linearity performance. Likewise, capacitive coupling element antennas have been demonstrated to be a viable choice for mobile handset integration. This paper combines these two advances into a single-antenna wideband receiver that achieves a 0.7-2.7-GHz reception band. The compact-size wideband tunable antenna achieves an efficiency of 45%-69% and occupies a volume of 2500 mm3. The front-end integrated circuit achieves an input compression point of +5 dBm with a noise figure of 4 dB while occupying only 0.3 mm2 of active die area. Additionally, an interface impedance study is performed to find the optimal impedances around the passive mixer and to demonstrate the different design tradeoffs of a passive-mixer-first receiver. A local oscillator duty-cycle adjustment circuit and its effect on the receiver performance is also presented. View full abstract»

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  • A 3.8-mW 3.5–4-GHz Regenerative FM-UWB Receiver With Enhanced Linearity by Utilizing a Wideband LNA and Dual Bandpass Filters

    Page(s): 3350 - 3359
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    A low-power regenerative frequency-modulated ultra-wideband (FM-UWB) receiver with wideband signal reception and linear FM-AM conversion is implemented in 65-nm CMOS for short-range communication systems. Different from the conventional regenerative FM-UWB receiver having the narrowband low-noise amplifier (LNA), the proposed receiver employs a wideband LNA and dual bandpass filters (BPFs) to improve the robustness against narrowband interference and frequency shift-keying demodulation with a relaxed Q requirement of the BPF. A 3.5-4-GHz FM-UWB receiver consisting of a stacked LNA, dual BPFs, two envelop detectors, and a subtractor successfully performs FM demodulation through wireless transmission from a 100-kb/s FM-UWB transmitter, consuming the total power of 3.8 mW. View full abstract»

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  • Design of Ultra-Low-Power 60-GHz Direct-Conversion Receivers in 65-nm CMOS

    Page(s): 3360 - 3372
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    This paper has explored an ultra-low-power design of two 60-GHz direct-conversion receivers in a 65-nm CMOS process for single-channel and multi-channel applications under the IEEE 802.15.3c standard, respectively. One subthreshold biasing 0.4-V transconductance mixer is designed with a compact quadrature hybrid coupler (160 μm × 210 μm with measured 3-dB intrinsic loss) in receivers to achieve low power (8 mW for single channel and 12.4 mW for multi-channel) and high gain (55 dB for single channel and 62-dB for multi-channel). One three-stage low-noise amplifier employs high- Q passive matchings. A double-layer-stacked inductor is utilized for matching in the single-channel receiver and a high-impedance transmission line is utilized for matching in the multi-channel receiver, respectively. In addition, one new modified Cherry-Hooper amplifier is applied for the variable-gain amplifier design to achieve high gain-bandwidth product and high power efficiency. The single-channel receiver is implemented with 0.34- mm2 chip area. It is measured with a power consumption of 8 mW, a minimum single-sideband noise figure (NF) of 4.9 dB, a 3-dB bandwidth of 3.5 GHz, and a maximum conversion gain of 55 dB. The multi-channel receiver is implemented with 0.56- mm2 chip area. It is measured with a power consumption of 12.4 mW, a 3-dB bandwidth of 8 GHz (59.5 ~ 67.5 GHz), and a maximum conversion gain of 62 dB. The measurement results show that the two demonstrated 60-GHz direct-conversion receivers can achieve high gain and low NF with ultra-low power in 65-nm CMOS. View full abstract»

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  • A CMOS Transmitter Leakage Canceller for WCDMA Applications

    Page(s): 3373 - 3380
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    A transmitter (TX) leakage canceller is proposed for improving the dynamic range of the receiver (RX) for wideband code division multiple access applications. A TX leakage canceller circuit in this paper is simple in implementation and has low noise figure (NF) contribution. It is a feed-forward canceller that samples a reference signal from the TX output and injects the amplitude-adjusted and phase-rotated signal to the RX chain. The canceller circuit is integrated with a low-noise amplifier and implemented in a 0.18-μm CMOS technology. A cancellation of 23 dB is achieved with only 10-mA current consumption increase and low NF increase. View full abstract»

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