dB Resolution Research Articles

Three-dimensional ultrafast ultrasound imaging of blood flow using row-column addressing array: A simulation study

Three-dimensional (3D) ultrafast imaging is important for ultrasound technology development. The traditional 3D imaging method based on fully sampled two-dimensional (2D) matrix often requires a large number of electronic channels with high density which limits the aperture size and imaging resolution in application. Recently developed row-column addressing (RCA) matrix effectively reduces the number of electronic channels from <i>N</i> × <i>N</i> to <i>N</i> + <i>N</i> by addressing the row and column elements. The beamforming strategy designed for 3D ultrasound imaging was based on the coherent compounding of orthogonal plane waves (OPW). Such a multi-angle OPW compounding strategy achieves virtual transmit focusing in both directions by transmitting a set of plane waves in one direction and receiving along the orthogonal direction, which finally leads to an isotropic point spread function (PSF). In this paper, multi-angle OPW method was investigated for 3D blood flow imaging using an RCA matrix with 128 rows and 128 columns, centered at 6 MHz. The delay and sum (DAS) beamforming was developed for coherent OPW compounding, and the singular value decomposition (SVD) filtering method was used for separating the dynamic blood flow signals from the static tissue signals and low-amplitude noise. The Doppler velocity was computed by the autocorrelation method, and finally the 3D power Doppler and color Doppler imaging of the blood flow were realized. To evaluate the imaging quality and investigate the effect of different OPW tilting angles, quantitative analysis was carried out using multiple parameters, including –6 dB resolution measurements of the PSF, SNR of the power Doppler images and velocity distribution of the color Doppler. The –6 dB resolution is improved from 0.986 mm to 0.493 mm with the number of angles increasing from 5 to 33. With 17 plane wave angles, the SNR of the power Doppler image reaches 30 dB, and the average deviation between the velocity distribution along the diameter of the blood flow phantom and the actual value is about 26.0%. In conclusion, results show that the ultrafast 3D imaging method based on RCA matrix can obtain 3D B-mode, power Doppler and color Doppler images. Increasing the number of tilting angles and enlarging the angle range can significantly improve the imaging quality. The proposed method can be helpful for developing 3D ultrafast ultrasound Doppler imaging and functional ultrasound imaging based on neuro-vascular coupling.

A High-Performance 3-D Imaging Technique Using Simultaneous Azimuth and Elevation Compounding.

A new technique for 3-D imaging with a row-column array (RCA) configuration has been developed. The technique requires an electrostrictive piezoelectric for the active substrate. While the top set of electrodes is connected to RF transmit and receive channels for conventional diverging wave imaging (DWI), the orthogonal bottom set of electrodes is connected to independently controlled variable dc bias channels. By implementing modulated bias patterns compounded across multiple pulses, fine delay control across the bottom elements can be achieved simultaneously with imaging with the top set of electrodes. This resulted in a high-quality two-way focus in both azimuth and elevation. A 20-MHz electrostrictive composite substrate was fabricated, and 64 top ×64 bottom electrodes were patterned and connected to custom beamforming and biasing electronics. The point spread functions were generated in all dimensions, and the -6 dB resolution was measured to be 93 [Formula: see text] axially, [Formula: see text] in the azimuth, and 328 [Formula: see text] in the elevation dimension. This was in good agreement with the simulated resolutions of 80, 273, and 280 [Formula: see text], respectively.

A Design of Analog Front-End with DBPSK Demodulator for Magnetic Field Wireless Network Sensors

This paper presents an on-chip fully integrated analog front-end (AFE) with a non-coherent digital binary phase-shift keying (DBPSK) demodulator suitable for short-range magnetic field wireless communication applications. The proposed non-coherent DBPSK demodulator is designed based on using comparators to digitize the received differential analog BPSK signal. The DBPSK demodulator does not need any phase-lock loop (PLL) to detect the data and recover the clock. Moreover, the proposed demodulator provides the detected data and the recovered clock simultaneously. Even though previous studies have offered the basic structure of the AFEs, this work tries to amplify and generate the required differential BPSK signal without missing data and clock throughout the AFE, while a low voltage level signal is received at the input of the AFE. A DC-offset cancellation (DCOC), a cascaded variable gain amplifier (VGA), and a single-to-differential (STOD) converter are employed to construct the implemented AFE. The simulation results indicate that the AFE provides a dynamic range of 0 dB to 40 dB power gain with 2 dB resolution. Measurement results show the minimum detectable voltage at the input of AFE is obtained at 20 mV peak-to-peak. The AFE and the proposed DBSPK demodulator are analyzed and fabricated in a 130 nm Bipolar-CMOS-DMOS (BCD) technology to recover the maximum data rate of 32 kbps where the carrier frequency is 128 kHz. The implemented DCOC, cascaded VGA, STOD, and the demodulator occupy 0.15 , 0.063 , 0.045 , and 0.03 of area, respectively. The AFE and the demodulator consume 2.9 mA and 0.15 mA of current from an external 5 V power supply, respectively.

Performance Analysis of a Gravity Gradient Referenced Navigation System

As an alternative way to overcome the weakness of the global navigation satellite system (GNSS) in hostile situation, a gravity gradient referenced navigation (GGRN) has been developed. This paper analyzed the performance of GGRN with respect to the initial errors, DB resolution as well as update rates. On the basis of simulations, it was found that the performance of GGRN is getting worse when initial errors exist but the navigation results are rapidly converged. Also, GGRN generates better results when DB resolution is higher and update rates are shorter than 20 seconds. However, it is difficult to deduce the optimal parameters for the navigation because some trajectories show better performance in case low-resolution DB is applied or long update rate is supposed. Therefore, further analysis to derive specific update conditions to improve the performance has been performed. Those update conditions would not be generalized for all cases although maximum improvement rate is over 200% in certain case. In the future, some more developments and tests on the combination of various geophysical data and/or algorithms are necessary to construct more stable and reliable navigation system.

X-Band 5-bit MMIC Digital Attenuator With Low Phase Shift

This paper presents the x-band 5-bit MMIC digital attenuator with low phase shift. Phase compensation techniques were used in the MMIC design to reduce the phase shift. This attenuator is fabricated with 0.2µm GaAs PHEMT process. Measurement results of the developed MMIC chips in the x-band show that the 5-bit MMIC digital attenuator has 0.5dB resolution and 15.5dB dynamic attenuation range, input return losses was less than 10dB and output return losses was less than 13dB for all attenuation states, RMS is less than 0.2dB; insertion loss is less than 3.8dB; phase shift error is less than 5°for 35 attenuation states; The MMIC chip size is 1.58 mm×2.95 mm×0.1mm. DOI : http://dx.doi.org/10.11591/telkomnika.v12i6.4742

Wideband 5-bit MMIC Digital Attenuator With High Precision

This paper mainly introduces the Wideband 5-bit MMIC digital attenuator with high precision. Firstly, the theories of basic GaAs digital attenuator MMICâ??s configurations are searched. Secondly, every possible configuration is contrasted, subsequently, appropriate topology is selected for each stage. This attenuator has been realized by 0.5µm GaAs pHEMT process. Simulation results of the digital attenuator has 0.25dB resolution and 7.75dB dynamic attenuation range, Input Voltage Standing Wave Ratio(VSWRIN) was less than 1.55 and Output Voltage Standing Wave Ratio(VSWROUT) was less than 1.6 for all attenuation states, high attenuation accuracy is less than ±0.26dB; insertion loss is less than 1.3dB; The layout of the digital attenuator with a chip size is 0.93 mmA?1.45 mm

High-Sensitivity Coherent Optical Time Domain Reflectometry Employing Frequency-Division Multiplexing

This paper proposes a novel parallel detection scheme for enhancing the sensitivity of coherent optical time domain reflectometry (C-OTDR). The proposed scheme is based on frequency-division multiplexing using a phase modulator and software processing. The performance advantages of the proposed method are clarified experimentally by comparison with a conventional C-OTDR. The detection sensitivity performance with the proposed method, operating at 40 frequency-division multiplexing, was improved by about 8 dB compared with the conventional method. We also clarified that the 3 dB resolution and Rayleigh dead zone of conventional C-OTDR and the proposed method were almost the same at a spatial resolution of 1 km.

Development of a SHA with 100 MS/s for High-Speed ADC Circuits

In this article, we have designed SHA, which has 12 Bit resolution at an input signal range of 1 Vpp and operates at a sampling speed of 100 MS/s in order to use at front of high speed ADC. SFDR(Spurious Free Dynamic Range) of the proposed system drops to approximately 66.3 dB resolution when the input frequency is 5 MHz, and the sampling frequency is 100 MHz, however, the circuit without a feedthrough has 12 bit resolution with approximately 73 dB.

A liquid lens-based broadband variable fiber optical attenuator

To the best of our knowledge, proposed is the first variable fiber optical attenuator (VFOA) using an electronically controlled variable focus liquid lens. The approach uses the changes in the radius of curvature of the liquid lens edge to enable an electronically controlled optical wedge that produces a varying beam tilt angle. In effect, changing beam tilt within a single mode fiber (SMF) lens free space coupling assembly leads to a polarization independent broadband VFOA design. The demonstrated VFOA experiment shows broadband operation over the 1530–1560 nm C-Band with a 40 dB dynamic range, <0.5 dB resolution, 0.3 dB polarization dependant loss, 4.3 dB fiber-to-fiber optical loss, 3 dB optical bandwidth from 1510 nm to 1700 nm, and switching time of <100 ms. Applications for this VFOA include use in hand held test and measurement equipment.

A vector intermodulation analyzer applied to behavioral modeling of nonlinear amplifiers with memory

A large signal vector intermodulation network analyzer with a dynamic range of 90 dB and phase resolution of better than 2/spl deg/ is reported. The analyzer is used in conjunction with a multislice behavioral model to characterize memory effects in three different RF power amplifiers: an MOSFET instrumentation amplifier, a multistage GaAs/silicon-based broadband microwave integrated-circuit amplifier, and an SiGe HBT monolithic-microwave integrated-circuit amplifier. The multislice behavioral model architecture builds on conventional single-tone AM-AM and AM-PM modeling extended to capture long-term memory effects that are characterized by asymmetric intermodulation distortion (IMD). Phase asymmetries of upper and lower IMD are captured. A systematic procedure for extracting the model is presented.

AN OPTIMAL DESIGN CONSIDERATION FOR HIGHER-ORDER DELTA–SIGMA AD CONVERTER

In this paper we proposed an approach for obtaining optimal stable modulator coefficients, which satisfy both SNR and stable input limit requirements. The empirical (3rd to 5th order) stable input limit formula is presented. Modulator examples are presented to demonstrate the usage of proposed method. The simulation results show that nearly 1-bit (6 dB) resolution is improved with the proposed method. The op-amp dc-offset influence on modulator performance is also discussed.

An Optimal Design Consideration for Higher-Order Delta-Sigma AD Converter

In this paper we proposed an approach for obtaining optimal stable modulator coefficients, which satisfy both SNR and stable input limit requirements. The empirical (3rd to 5th order) stable input limit formula is presented. Modulator examples are presented to demonstrate the usage of proposed method. The simulation results show that nearly 1-bit (6 dB) resolution is improved with the proposed method. The op-amp dc-offset influence on modulator performance is also discussed.

Effects of finite weight resolution and calibration errors on the performance of adaptive array antennas

Adaptive antennas are now used to increase the spectral efficiency in mobile telecommunication systems. A model of the received carrier-to-interference plus noise ratio (CINR) in the adaptive antenna beamformer output is derived, assuming that the weighting units are implemented in hardware, The finite resolution of weights and calibration is shown to reduce the CINR. When hardware weights are used, the phase or amplitude step size in the weights can be so large that it affects the maximum achievable CINR. It is shown how these errors makes the interfering signals leak through the beamformer and we show how the output CINR is dependent on power of the input signals. The derived model is extended to include the limited dynamic range of the receivers, by using a simulation model. The theoretical and simulated results are compared with measurements on an adaptive array antenna testbed receiver, designed for the GSM-1800 system. The theoretical model was used to find the performance limiting part in the testbed as the 1 dB resolution in the weight magnitude. Furthermore, the derived models are used in illustrative examples and can be used for system designers to balance the phase and magnitude resolution and the calibration requirements of future adaptive array antennas.

Low voltage fully differential CMOS voltage mode digitally controlled variable gain amplifier

In this paper, a voltage mode variable gain amplifier (VGA) is presented. A fully differential implementation is used to suppress the common mode noise and increase the dynamic range. The gain of the proposed VGA can be digitally controlled from 0 to 53dB, with a 1dB resolution. The gain control is performed in two stages; coarse control with a 6dB resolution and fine control with a 1dB resolution. Simulation shows that the bandwidth is about 15MHz at the maximum gain (53dB). The differential output third intercept point (OIP3) is 4V.

Fast simulation of sigma-delta modulators using SPICE

Presents a fast simulation method using SPICE. We traded the prohibitive time-consuming simulation problem for a much less time-consuming problem, plus a little analysis work. This makes it possible for one to use SPICE simulation to optimize the parameters in the modulator within a reasonable time period. Rounding and truncation errors within the circuit simulation algorithms typically set an upper limit on the measurable SNR on the order of 90 dB. This implies that very high-resolution modulators cannot correctly be simulated by SPICE. Fortunately, 90 dB resolution is adequate for most modern communication baseband A/D converters.

A high-frequency and high-resolution fourth-order ΣΔ A/D converter in BiCMOS technology

A high-performance cascaded sigma-delta modulator is presented. It has a new three-stage fourth-order topology and provides functionally a maximum signal to quantization noise ratio of 16 bits and 16.5-bit dynamic range with an oversampling ratio of only 32. This modulator is implemented with fully differential switch-capacitor circuits and is manufactured in a 2-/spl mu/m BiCMOS process. The converter, operated from +/-2.5 V power supply, +/-1.25 V reference voltage and oversampling clock of 48 MHz, achieves 97 dB resolution at a Nyquist conversion rate of 1.5 MHz after comb-filtering decimation. The power consumption of the converter is 180 mW. >

Low-reflectivity in-line variable attenuator utilizing optical fiber tapers

A single-mode inline variable optical attenuator utilizing optical fiber tapers is discussed. Optical attenuation control is achieved through axial separation between two tapers with beveled endfaces aligned within a ceramic sleeve. Increased axial separation causes increased coupling loss between the two taper fundamental modes. Insertion loss of 75 dB with continuous 0.05 dB resolution, and reflection return loss of better than 58 dB have been realized. Theoretical studies indicate low polarization and wavelength dependence, and inherent insertion loss of >

A seismic telemetry system of large dynamic range

Abstract An optimum telemetry system (OTS) has been developed that can be plugged directly into the front-end electronics of a field seismic station to enable large dynamic range (120 dB) data transmission, 60 dB resolution, and three-component seismic recording. This new system is designed to be accommodated within a conventional single ±125-Hz transmission channel. With CMOS microprocessors and a minimum of 64 kB memory, the OTS buffer stores 3.5 min of data for one channel or 1 min of data for three channels at 128 sps. The buffer storage can easily be expanded by an order of magnitude without significant increase in cost, but the present buffer size is sufficient for regional seismic networks of coverage less than 500 km in size; i.e., enough preevent memory is allowed for event trigger and gain-ranging operations. There is no sacrifice on timing accuracy, and to apply corrections to the travel-time delays is simple as the delays are exactly known. To guarantee the 60 dB resolution in a ±125-Hz FM transmission band, a new digital voltage-controlled oscillator has been designed for the OTS which keys the FM center frequency accurate to 0.1 per cent and practically eliminates the drift of the voltage-controlled oscillator center frequency. The OTS offers a practical solution to the severe signal-clipping problem that has plagued many high-performance telemetered seismic networks.

Piston attenuator as RF signal vernier in the 10-300 MHz range: determination and correction of spurious mode errors

Systematic errors in H11-mode piston attenuators from unwanted mode excitation have been measured for CW, and pulse modulated RF signals as well, up to 300 MHz with a new calibration circuit based on a linear RF-IF mixer. The attenuation deviation by spurious mode influence can be calculated from the determined amplitude ratio of superposed modes and can be corrected. In this way piston attenuators, originally designed for IF application, can also be used as RF verniers with 0.01 dB resolution up to 300 MHz and possibly higher with an accuracy depending on mixer linearity in the calibration circuit.

Low-Noise Wide-Band Amplifier System for Stochastic Beam Cooling Experiments

A new low-noise wide-band power amplifier system has been developed for stochastic beam cooling experiments. The system incorporates a low-noise preamplifier with a noise figure of 1.9 dB over a bandwidth range of 20 to 300 MHz, wide-band driver and buffer stages, a frequency characteristics shaping network, a remotely controlled wide-band attenuator with 0.1 dB resolution, a remotely controlled high resolution adjustable delay line, and a wide-band solid-state output power amplifier. The amplifier system has a maximum voltage gain of 140 dB over a bandwidth from 1.5 to 310 MHz, a signal group delay of 55.5 ns, and a c. w. output power level of 75 W. Particular attention was paid to minimizing the signal propagation time delay of the amplifier system, the propagation time delay change as a function of the system gain, and harmonic and intermodulation distortions. Using a new wide-band electron bombarded semiconductor output amplifier, the system will have a bandwidth from 30 to 400 MHz, a signal group delay of 37 ns and an output power of 100 W.