Spurious Harmonics Research Articles

Compact wide stopband microstrip lowpass filter using polygon patches and meandered lines

In this paper, a low pass filter based on T-Shaped resonator is presented. The T-Shaped resonator consists of meandered lines and rectangular patches. Also, the LC model and transfer function of the proposed resonator is presented. For suppression of spurious harmonics, a bandstop structure consists of hexangular patches and open stubs has been utilized. Finally, the wide stopband microstrip lowpass filter with cutoff frequency 2.72 GHz has been simulated, fabricated and measured. The LPF has good characteristics such as wide stopband and insertion loss lower than 0.18 dB in the passband region. The rejection level is less than -20 dB from 2.98 up to 21.3 GHz. The filter size is 10.5 mm×12.7 mm, or 0.131 λ<sub>g</sub>× 0.158 λ<sub>g</sub>, where λ<sub>g</sub> is the guided wavelength. The measured and simulated results of the filter is in good agreement with each other, which show the merits of low insertion loss and wide stopband.

Gradient Error Compensation in SC-MDACs

High speed data converter architectures such as pipelined analog-to-digital-converters (ADCs) typically consist of large capacitor arrays that are highly susceptible to systematic errors. Although significant efforts have been made in the literature to compensate linear and parabolic errors, the rotated parabolic components are less explored. These rotated parabolic components are responsible for spurious harmonics at the output of the converter, thereby degrading the linearity. In this article, we have investigated the origin of these rotated components, their impact on conversion linearity and discussed strategies to mitigate them. A placement technique along with one track routing solution, is proposed for complete compensation of the systematic errors. An algorithm is also provided to extend this technique to higher resolutions. The proposed technique is verified on the model of pipelined ADC, as well as current steering DAC. The incorporation of such technique results in near ideal linearity performance.

Design and fabrication of microstrip lowpass filter using asymmetric hairpin resonator

In this letter, a compact microstrip lowpass filter (LPF) is designed using serial connecting of two modified asymmetric hairpin resonators. The proposed design is consists of four open-circuited stubs that are used to suppress spurious harmonics in the stopband. The proposed filter has wide-stop band with attenuation level better than −28 dB from 2.16 up to 26.1 GHz and sharp roll-off. The proposed LPF has −3 dB cutoff frequency equal to 2.11 GHz, wide stopband width around 12th harmonic suppression and insertion loss less than 0.1 dB at about 85% of the passband. The excellent agreement is observed between the simulated results and measured values of the fabricated LPF.

Standard Cell-Based Ultra-Compact DACs in 40-nm CMOS

In this paper, very compact, standard cell-based Digital-to-Analog converters (DACs) based on the Dyadic Digital Pulse Modulation (DDPM) are presented. As fundamental contribution, an optimal sampling condition is analytically derived to enhance DDPM conversion with inherent suppression of spurious harmonics. Operation under such optimal condition is experimentally demonstrated to assure resolution up to 16 bits, with 9.4–239X area reduction compared to prior art. The digital nature of the circuits also allows extremely low design effort in the order of 10 man-hours, portability across CMOS generations, and operation at the lowest supply voltage reported to date. The limitations of DDPM converters, the benefits of the optimal sampling condition and digital calibration were explored through the optimized design and the experimental characterization of two DACs with moderate and high resolution. The first is a general-purpose DAC for baseband signals achieving 12-bit (11.6 ENOB) resolution at 110kS/s sample rate and consuming $50.8\mu \text{W}$ , the second is a DAC for DC calibration achieving 16-bit resolution with 3.1-LSB INL, 2.5-LSB DNL, $45\mu \text{W}$ power, at only $530\mu \text{m}^{2}$ area.

A compact high-temperature superconducting band-pass filter with wide upper stopband

A novel hair-pin resonator(NHR) composed of interdigital capacitor and fractal resonator is developed, which not only has compact in size but also has no harmonics up to three times of the fundamental frequency. The results show that the equivalent capacitance introduced by the interdigital capacitor at the conventional hair-pin resonator terminal plays a major role in suppressing the spurious harmonics, whereas the equivalent inductance has no improved harmonic rejection ability. A miniature five-pole wide-band HTS bandpass microstrip filter has been designed and fabricated with this NHR on a double-sided MgO-based DBCO thin film. Measurement at 79.4K shows that the fabricated HTS filter has less than 0.11 dB insertion loss and better than 20 dB return loss in the passband, and an ultra high spurious passband at about 3.3f0. Moreover, the simulated and measured results are found in excellent agreement in wideband response.

Low phase-noise oscillator based on SIW bandpass filter implementing at the Qsc-peak frequency

ABSTRACTIn this paper, a novel low phase-noise oscillator employing an substrate integrated waveguide (SIW) bandpass filter (BPF) embedded with a complementary spiral resonator (CSR) is proposed. The Qsc-peak frequency is chosen for the design of the oscillator to achieve optimal phase noise performance. The CSR exited by TM01 mode has been etched on the top metal of the circular cavity. Three transmission poles and three transmission zeros can be obtained by the proposed SIW BPF which is regarded as the frequency stabilization element. Meanwhile, a short summary about how to obtain a high Qsc-factor to achieve low phase noise performance has been illustrated. A C-band oscillator using a field effect transistor has been designed and experimentally demonstrated at 5.71 GHz with a 147.6 dBc/Hz phase noise at 1 MHz offset frequency. Moreover, the output power is −1.49 dBm with a figure of merit of −209.2 dBc/Hz and less than −32.8 dBm spurious harmonics is obtained.

Compact High-Isolation Base-Station Duplexer Using Triple-Mode Ceramic Cavities

A microwave duplexer with high isolation is presented in this paper. The device is based on triple-mode filters that are built using silver-plated ceramic cuboids. To create a six-pole, six-transmission-zero filter in the DCS-1800 band, which is utilized in mobile communications, two cuboids are cascaded. To shift spurious harmonics, low dielectric caps are placed on the cuboid faces. These caps push the first cuboid spurious up in frequency by around 340 MHz compared to the uncapped cuboid, allowing a 700-MHz spurious free window. To verify the design, a DCS-1800 duplexer with 75-MHz widebands is built. It achieves around 1 dB of insertion loss for both the receive and transmit ports with around 70 dB of mutual isolation within only 20-MHz band separation, using a volume of only 30 cm3 .

Ultra-Wideband Impulse Radar Through-Wall Detection of Vital Signs

This paper presents a new system for the detection of human respiration behind obstacles using impulse ultra-wideband (UWB) radar. In complex environments, low signal-to-noise ratios (SNRs) as they can result in significant errors in the respiration, heartbeat frequency, and range estimates. To improve the performance, the complex signal demodulation (CSD) technique is extended by employing the signal logarithm and derivative. A frequency accumulation (FA) method is proposed to suppress mixed products of the heartbeat and respiration signals and spurious respiration signal harmonics. The respiration frequency is estimated using the phase variations in the received signal, and a discrete short-time Fourier transform (DSFT) is used to estimate the range. The performance of the proposed system is evaluated along with that of several well-known techniques in the literature.

A Theoretical Model of Dual Tunable Optoelectronic Oscillator

A theoretical model of an electronically tunable multi-loop optoelectronic oscillator (OEO) based on photonic and microwave multiferroic delay lines has been developed. The theory takes into account a dispersion of electromagnetic waves in optical fibers and a dispersion of spin-electromagnetic waves in ferrite-ferroelectric structures. An expression for transfer function of the OEO circuitry was derived. The theory enables one to calculate transmission characteristics and suppression of spurious harmonics of the multi-loop OEOs. The features of both magnetic and electric tunabilities are investigated.

Experimental investigation of material nonlinearity using the Rayleigh surface waves excited and detected by angle beam wedge transducers

Angle beam wedge transducers are widely used in nonlinear Rayleigh wave experiments as they can generate Rayleigh wave easily and produce high intensity nonlinear waves for detection. When such a transducer is used, the spurious harmonics (source nonlinearity) and wave diffraction may occur and will affect the measurement results, so it is essential to fully understand its acoustic nature. This paper experimentally investigates the nonlinear Rayleigh wave beam fields generated and received by angle beam wedge transducers, in which the theoretical predictions are based on the acoustic model developed previously for angle beam wedge transducers [S. Zhang, et al., Wave Motion, 67, 141–159, (2016)]. The source of the spurious harmonics is fully characterized by scrutinizing the nonlinear Rayleigh wave behavior in various materials with different driving voltages. Furthermore, it is shown that the attenuation coefficients for both fundamental and second harmonic Rayleigh waves can be extracted by comparing the measurements with the predictions when the experiments are conducted at many locations along the propagation path. A technique is developed to evaluate the material nonlinearity by making appropriate corrections for source nonlinearity, diffraction and attenuation. The nonlinear parameters of three aluminum alloy specimens – Al 2024, Al 6061 and Al 7075 – are measured, and the results indicate that the measurement results can be significantly improved using the proposed method.

Theoretical Based Design of Ultra-Wideband Filter with Dual Band-Notch

In this paper, a compact ultra-wideband microstrip band-pass filter with single/dual-notched bands is proposed. The filter is theoretically designed based on a multiple-mode resonator which consists of a short circuit stub loaded-ring resonator. A multi stepped impedance resonator is also applied to reject unwanted in-band frequencies and extend the upper-stopband. The proposed filter is analyzed by utilizing graphs according to odd- and even-mode method. The resonant modes are allocated between 3.1 GHz to 10.6 GHz and transmission zeros are adjusted at upper stopband to create a sharp roll-off and suppress the spurious harmonics, as well as a compact physical size. Full-wave simulations are performed for three types of filters, with and without notch-bands, to verify theoretical results. The measurement results demonstrate that not only − 3 dB fractional bandwidth is more than 120% and but also at least − 20 dB suppression can be achieved at upper-stopband.

A Novel Compact CPW Multi-StopBand Filter with DGS Integrating Circular Ring Resonator

A novel and compact multi-band stop filter with good selectivity and wide upper pass band performance with good rejection based on defected ground structure (DGS) integrating a circular ring resonator to suppress undesired spurious bands frequency or harmonics in microwave and millimeter wave circuits is proposed. The presented filter has a compact size because the circular ring resonator is integrated in DGS, the both of them are etching in the ground plane.

Control System Optimization Techniques for Real-Time Applications in Fusion Plasmas: The RFX-mod Experience

A series of techniques is presented that has been developed to optimize the output magnetic field of the feedback control system on the RFX-mod reversed field pinch device. With the aim of minimizing the harmonic distortion and correcting localized error fields, these methods should be lightweight for real-time application and effective in improving the performance of a system that is routinely used for active control of magnetohydrodynamic plasma instabilities. The implementation of simple, linear algebra based, real-time optimization methods will be described along with proof of the beneficial effects sought. The focus of this paper is set on a spurious harmonics reduction technique based on the decoupling of sensors and actuators; a description of its derivation will be given together with the implementation in the control loop. A similar procedure for the compensation of faulted actuators will also be mentioned.

Single-sideband modulator for frequency domain multiplexing of superconducting qubit readout

We introduce and experimentally characterize a superconducting single-sideband modulator compatible with cryogenic microwave circuits and propose its use for frequency domain multiplexing of superconducting qubit readout. The monolithic double-balanced modulators that comprise the device are formed with purely reactive elements (capacitors and Josephson junction inductors) and require no microwave-frequency control tones. Microwave signals in the 4 to 8 GHz band, with power up to −85 dBm, are converted up or down in frequency by as much as 120 MHz. Spurious harmonics in the device can be suppressed by up to 25 dB for select probe and modulation frequencies.

Modulation calorimetry in diamond anvil cells. II. Joule-heating design and prototypes

Part I shows that quantitative measurements of heat capacity are theoretically possible inside diamond anvil cells via high-frequency Joule heating (100 kHz–10 MHz), opening up the possibility of new methods to detect and characterize transformations at high-pressure such as the glass transitions, melting, magnetic orderings, and the onset of superconductivity. Here, we test the possibility outlined in Part I, using prototypes and detailed numerical models. First, a coupled electrical-thermal numerical model shows that specific heat of metals inside diamond cells can be measured directly using ∼1 MHz frequency, with <10% accuracy. Second, we test physical models of high-pressure experiments, i.e., diamond-cell mock-ups. Metal foils of 2–6 μm-thickness are clamped between glass insulation inside diamond anvil cells. Fitting data from 10 Hz to ∼30 kHz, we infer the specific heat capacities of Fe, Pt, and Ni with ±20%–30% accuracy. The electrical test equipment generates −80 dBc spurious harmonics, which overwhelm the thermally induced harmonics at higher frequencies, disallowing the high precision expected from numerical models. An alternative Joule-heating calorimetry experiment, on the other hand, does allow absolute measurements with <10% accuracy, despite the −80 dBc spurious harmonics: the measurement of thermal effusivity, ρck (ρ, c, and k being density, specific heat, and thermal conductivity), of the insulation surrounding a thin-film heater. Using a ∼50 nm-thick Pt heater surrounded by glass and 10 Hz–300 kHz frequency, we measure thermal effusivity with ±6% accuracy inside the sample chamber of a diamond anvil cell.

A Compact Broadside Coupled Notched Band UWB Filter with Wide Upper Stopband

ABSTRACTA broadside coupled ultra-wideband (UWB) bandpass filter (BPF) with notched band and wide upper stopband is proposed and implemented. Initially, a broadside coupled UWB filter structure with good passband characteristics is developed. To this, split ring resonator (SRR) metal lines of half guided waveguide length are coupled to generate passband notch. Later, stub lines are embedded in the input and output (I/O) feeding lines whose attenuation poles suppress the spurious harmonics and widen the stopband. Finally, the proposed structure is fabricated and measured which establishes the authenticity of the full-wave electromagnetic response. The passband extends from 2.85 to 11.3 GHz with stopband of width 18 GHz and depth greater than 18 dB. The variation of group delay is less than 0.42 ns in the passband. The proposed structure is small in size measuring 11.08 × 11.7 mm2.

Phase-Based Methods for Heart Rate Detection Using UWB Impulse Doppler Radar

Ultra-wideband (UWB) pulse Doppler radars can be used for noncontact vital signs monitoring of more than one subject. However, their detected signals typically have low signal-to-noise ratio (SNR) causing significant heart rate (HR) detection errors, as the spurious harmonics of respiration signals and mixed products of respiration and heartbeat signals (that can be relatively higher than heartbeat signals) corrupt conventional fast Fourier transform spectrograms. In this paper, we extend the complex signal demodulation (CSD) and arctangent demodulation (AD) techniques previously used for accurately detecting the phase variations of reflected signals of continuous wave radars to UWB pulse radars as well. These detection techniques reduce the impact of the interfering harmonic signals, thus improving the SNR of the detected vital sign signals. To further enhance the accuracy of the HR estimation, a recently developed state-space method has been successfully combined with CSD and AD techniques and over 10 dB improvements in SNR is demonstrated. The implementation of these various detection techniques has been experimentally investigated and full error and SNR analysis of the HR detection are presented.

Enhanced Bandwidth and Diversity in Real-Time Analog Signal Processing (R-ASP) Using Nonuniform C-Section Phasers

We show that a continuously nonuniform coupled-line C-section phaser, as the limiting case of the step-discontinuous coupled-line multisection commensurate and non-commensurate phasers, provides enhanced bandwidth and diversity in real-time analog signal processing (R-ASP). The phenomenology of the component is explained in comparison with the step-discontinuous using multiple-reflection theory and a simple synthesis procedure is provided. The bandwidth enhancement results from the suppression of spurious group delay harmonics or quasi-harmonics, while the diversity enhancement results from the greater level of freedom provided by the continuous nature of the nonuniform profile of the phaser. These statements are supported by theoretical and experimental results.

Empirical modeless decomposition and modal identification method for nonstationary vibration processes

An empirical data decomposition method is developed in this study to accurately identify modeless component and intrinsic vibration modal terms separately from vibration processes, which are characterized by nonlinearity and nonstationarity. Two key innovations related to this method are proposed. One of them is associated with the definition of root mean square instantaneous amplitude, which is adopted as a meaningful supplement for vibration mode identification. It also acts as a critical criterion to visualize the nonstationarity of some vibration processes. The other innovation is the use of a predetermined maximum intrinsic time window and cubic spline interpolation technique for the empirical data decomposition method with the aim to decompose a modeless component from nonstationary processes. Unlike in other decomposition methods, a modeless component should be decomposed prior to modal analysis. The requirement of using spurious harmonics to represent nonlinear and nonstationary signals is fully eliminated via these two key innovations, thereby increasing the accuracy of the subsequent modal identification. Given the well-designed decomposition method, energy aliasing in data processing can also be effectively avoided. Significant conclusions about the complicated vibration processes composed of nonstationary and intrinsic modal terms are drawn by using the proposed empirical modeless decomposition and modal identification method.

Extension of 2D second-order irregular waves generation equations to non-continuous wavemaker shapes

Second-order Stokes-like solution of the wavemaker problem involves the participation of first order evanescent modes to the generation of spurious free harmonics. The unwanted free potential, and the paddle signal needed to suppress it, must be evaluated through series summation which, up to now, have been considered non-convergent for certain wavemaker configurations. This paper presents a demonstration of the convergence of these series summation for the historically discarded configurations.Following previous works, the free harmonics second order transfer function can obtained in two different ways. This operation reveals that the two alternative solutions match only if the lateral boundary condition is properly described. In particular, the domain restriction of non-continuous paddle shapes must be represented through left-continuous step functions. Conversely, if the support is limited only adjusting the integration limits, or the unit step function is non-zero at the origin, one of the two methods leads to an incomplete formulation.