Flat Bandwidth Research Articles

An Ultra-Wideband IF Millimeter-Wave Receiver With a 20 GHz Channel Bandwidth Using Gain-Equalized Transformers

This paper presents a CMOS millimeter-wave (mm-wave) receiver designed to meet the challenges in low-power, ultra-broadband, phased-array systems with a large number of array elements. This receiver employs a high intermediate-frequency (IF) heterodyne architecture to reduce the frequency and power consumption associated with distributing a local oscillator (LO). The receiver operates over a bandwidth of 51–71 GHz, while maintaining 20 GHz of bandwidth along the signal chain of the entire mm-wave front end, through a high-IF stage, and to the baseband output. To maintain a high fractional bandwidth (fBW) throughout the signal chain, this receiver employs multiple gain-equalized transformers . Receiver measurements show an overall flat bandwidth response of 20 GHz, with a total gain of 20 dB, a minimum double-sideband noise figure of 7.8 dB, and an input 1 dB compression power of $- 24 \text{dBm}$ while consuming 115 mW from a 1.1 V supply. The test chip, implemented in a six-metal layer 40 nm CMOS process, occupies an area (including pads) of $1.2 \text{mm}^{2}$ .

Correcting EM system bandwidth limitations

All EM transmitters, sensors and data acquisition systems have bandwidth limitations. Transmitters have upper bandwidth limitations due to finite slew rate issues, and systems have a lower bandwidth set by the base frequency used. Receivers and data acquisition systems ideally should have a flat bandwidth response that spans the transmitted signal bandwidth. The data acquisition system should sample fast enough to capture the highest frequencies of interest, with anti-alias filters to prevent data contamination from unwanted signals. Sensors however may have physical bandwidth limitations, for example fluxgates and feedback MT sensors may have an upper corner frequency of a few kHz, and ARMIT and feedback MT sensors have lower corner frequencies in the sub 1 Hz range. In many cases, the sensor corner frequency can be mathematically described as a single- or multi-pole response. In this case, it is possible to exactly deconvolve the data to exactly correct for the sensor imperfection. A limitation of this process is that noise as well as signal may be amplified in this correction process. Without correction, data may be incorrectly modelled or interpreted. This paper illustrates the correction of fluxgate (mostly a time delay of hundred or more microseconds), ARMIT 2 (where a significant but exact correction is required), ANT23 feedback and 3D3 dBdt data.

Flat Broadband Chaos in Mutually Coupled Vertical-Cavity Surface-Emitting Lasers

The flatness of chaos generated by mutually coupled vertical-cavity surface-emitting lasers (VCSELs) has been investigated experimentally in two configurations. Power variation between dc and the bandwidth frequency and flat bandwidth are used to quantitatively study the flatness of chaos. The power spectrum of chaos from a single VCSEL in both configurations is not flat due to a peak at relaxation oscillation frequency. This uneven nature will affect the application of chaos in random number generation. The experimental results show that the power spectra of chaos can easily be flattened by combining two uneven chaos. Flat bandwidth of the combined output can be 15 times higher than that of chaos from a single VCSEL at the optimum frequency detuning. The mechanism for this flattening is attributed to the frequency beating.

Spin susceptibility of Anderson impurities in arbitrary conduction bands

Spin susceptibility of Anderson impurities is a key quantity in understanding the physics of Kondo screening. Traditional numerical renormalization group (NRG) calculation of the impurity contribution $\chi_{\textrm{imp}}$ to susceptibility, defined originally by Wilson in a flat wide band, has been generalized before to structured conduction bands. The results brought about non-Fermi-liquid and diamagnetic Kondo behaviors in $\chi_{\textrm{imp}}$, even when the bands are not gapped at the Fermi energy. Here, we use the full density-matrix (FDM) NRG to present high-quality data for the local susceptibility $\chi_{\textrm{loc}}$ and to compare them with $\chi_{\textrm{imp}}$ obtained by the traditional NRG. Our results indicate that those exotic behaviors observed in $\chi_{\textrm{imp}}$ are unphysical. Instead, the low-energy excitations of the impurity in arbitrary bands only without gap at the Fermi energy are still a Fermi liquid and paramagnetic. We also demonstrate that unlike the traditional NRG yielding $\chi_{\textrm{loc}}$ less accurate than $\chi_{\textrm{imp}}$, the FDM method allows a high-precision dynamical calculation of $\chi_{\textrm{loc}}$ at much reduced computational cost, with an accuracy at least one order higher than $\chi_{\textrm{imp}}$. Moreover, artifacts in the FDM algorithm to $\chi_{\textrm{imp}}$, and origins of the spurious non-Fermi-liquid and diamagnetic features are clarified. Our work provides an efficient high-precision algorithm to calculate the spin susceptibility of impurity for arbitrary structured bands, while negating the applicability of Wilson's definition to such cases.

Effects of Raman pump power distribution on output spectrum in a multi-wavelength BRFL.

This paper aims to investigate changes in multi-wavelength Brillouin-Raman fiber laser (MBRFL) spectra characteristics that are influenced by variation of Raman pump power distribution along the two fiber-entry points. This is carried out by incorporating a Raman pump source with a set of couplers with various ratios. In this arrangement, the optimization of pumping ratio is properly carried out to achieve high number of lasing lines with 20 GHz spacing which yield the highest peak power discrepancy between odd- and even-order lasing lines and an excellent Stokes optical signal-to-noise ratio (S-OSNR). Employment of 50/50 coupler offers 212 flat amplitude channels with an average 27.5 dB S-OSNR and -10 dBm Stokes peak power when the Brillouin pump wavelength is set at 1543 nm. Achievements such flat and wide bandwidth MBRFL spectrum with 20 GHz spacing and excellent S-OSNR utilizing just a single pump source is significant in terms of simplicity and flexibility.

A stepped-plate radiator as a parametric array loudspeaker

A parametric array loudspeaker can generate a high directional audible sound beam in the air by the nonlinear acoustic interaction widely known as a “Parametric Array.” The advantage of the parametric array phenomenon is that it creates a narrow beam using the small aperture of an acoustic radiator. It can be used in many applications, including high directivity communication systems. However, the sound pressure level generated by the parametric array is very low, which necessitates a high efficiency and intensity of sound. This paper describes the application of a stepped-plate radiator in a parametric array loudspeaker. The stepped-plate radiator has two resonance frequencies (f1 = 75 kHz, f2 = 85 kHz) in the design frequency region, and three different steps that compensate for the phase difference in the flexural vibrating plate. This allows the generation of high directivity audible sound in the wide flat radiation bandwidth of the audible frequencies range (100 Hz to 16 kHz, difference frequency waves with equalization). [Work supported by ADD (UD130007DD).]

ZNO AND ZNO/PBS HETEROJUNCTION PHOTO ELECTROCHEMICAL CELLS

Photo Electrochemical Cell (PEC) can also be used for splitting of water into hydrogen and Oxygen. Here, ZnO nanorod PEC has been prepared in hydrothermal method and ZnO/PbS quantum dot PEC has been prepared by hydrothermal method and chemical bath deposition method. UV-Visible spectroscopy has been observed. Flat band voltage, bandwidth and majority charge carriers have been calculated from Mott-Schottky. Impedance variation at semiconductor and electrolyte junction has been observed with Electrochemical Impedance Spectroscopy (EIS).

Effect of Cascading Amplification Stages on the Performance of Serial Hybrid Fiber Amplifier

This study demonstrates simulation and experimental validation of a wideband serial hybrid Raman/erbium-doped fiber amplifier. Two configurations are adopted; in type A, a Raman amplifier is the first stage, and in type B, an erbium-doped fiber amplifier is the first stage. At low input signal power, the average gain level is 20 dB with a flat gain bandwidth of 40 nm for both configurations. The noise figure in type B is dominated by the erbium-doped fiber amplifier and produces lower values and flatter spectra than in type A. The gain of the proposed hybrid amplifiers is affected more by the second amplification stage.

Semi-lumped Balun Transformer using Coupled LC Resonators

This paper presents a semi-lumped balun transformer using conventional PCB process and its design theory and geometry for the maximally flat response and wide bandwidth using magnetically coupled LC resonators. The proposed balun is comprised of two pairs of coupled resonators which share one among three LC resonators. It provides an identical magnitude and phase difference of 180° between two balanced ports with DC isolation and an impedance transformation characteristic. Theoretical design and analysis were performed to optimize the inductance and capacitance values of proposed balun device for obtaining the wide bandwidth and maximally flat response in its pass-band. Three balun transformers with a center frequency of 500 MHz were demonstrated for proving the concept of design proposed. They were fabricated by using lumped chip capacitors and planar inductors embedded into a conventional 4-layered PCB substrate. They exhibited a maximum magnitude difference of 0.8 dB and phase difference within 2.4 degrees.

Improved Maximally Flat Wideband CIC Compensation Filter using Sharpening Technique

paper presents the design and implementation of sharpening of maximally flat cascaded integrator comb compensation filters. The modified sharpened cascaded integrator comb compensation filter is used to improve magnitude response and gain. For wide-band compensation fourth-order linear phase filters is considered. The decimation factor of CIC filter is D and number of adders are depends upon decimation factor D. The compensation filter is a multiplier less design which works at low rate. The comparison within some methods reported in the literature is provided.

Enhanced Flat Broadband Optical Chaos Using Low-Cost VCSEL and Fiber Ring Resonator

Low-cost vertical-cavity surface-emitting laser (VCSEL) and semiconductor optical amplifier (SOA) have been explored experimentally in a setup with a fiber ring resonator to generate flat broadband chaos. The effect of the frequency detuning between the fiber grating frequency and the free-running VCSEL's frequency, and the bias current of the SOA on the bandwidth of chaos has been studied. The results show that the bandwidth of the chaos is strongly dependent on the frequency detuning and the bias current of the SOA. Using the conventional definition of chaos bandwidth, the bandwidth of chaos with the fiber ring resonator can be about three times greater than that with a conventional mirror. In order to consider the flatness of the chaos spectra, the flat bandwidth of chaos is redefined as the frequency range between dc and the frequency where the power fluctuation is within ±3 dB. With this definition, the flat bandwidth of chaos with the fiber ring resonator is >10 times higher than that with conventional mirror feedback.

Spectrally intense terahertz source based on triangular Selenium.

The intensity of a nonlinear terahertz (THz) source is primarily given by its spectral density. In this letter, we introduce triangular Selinium (Se) as a novel THz emitter and show numerically its superior properties to the currently used crystals for intense THz generation. The excellent phase matching enables the applicability of elongated Se crystals which results in very high spectral flatness and broad THz bandwidth (0.5–3.5 THz), high conversion efficiency and THz pulse energy.The spectral THz density produced by optical rectification in Selenium exceeds those from contemporary crystal-based THz sources.

Numerical simulation for optimizing mode shaping and supercontinuum flatness of liquid filled seven-core photonic crystal fibers

A seven-core photonic crystal fiber filled with commercial index-matching liquids is designed to optimize mode shaping and supercontinuum flatness. Numerical simulation of supercontinuum generation in these liquid-filled seven-core PCFs is conducted at 25°C. The definition of spectral flatness measure is used to quantitatively describe SC flatness. Numerical simulations are performed to study the propagation of femtosecond pulse in the liquid-filled seven-core PCFs. Results show that mode shaping and supercontinuum flatness can be easily optimized and modified using the index-matching liquids in seven-core PCF without varying the structure of the air rings around the guiding cores. Simulations also show that 50fs pulses with a center wavelength of 1064nm generate relatively flat SC spectra in the 25cm-long liquid-filled PCF. A flat spectral bandwidth of 400nm (900–1300nm) is achieved with an applied pump power of 30kW. The simulation results demonstrate that using index-matching liquids to fill the inner ring of the seven-core PCF optimizes mode shaping and generates flat SC spectrum in specified wavelength region. Results further demonstrate that the SC flatness increased with increasing PCF dispersion corresponding to pump wavelength, on the premise that generated enough spectrum width, when the pump worked in the normal dispersion region. Temperature barely affects the spectrum flatness, but can affect spectrum broadening.

Temperature-independent broadband silicon modulator

We demonstrate a 20Gb/s temperature-independent silicon modulator based on symmetrical Mach–Zehnder Interferometer. The MMI coupler was used as splitter/combiner in symmetrical MZI for balanced propagation. The ±15°C temperature-independent eye diagrams were measured at 10Gb/s with over 15dB extinction ratio. Based on over 30nm flat optical bandwidth, the broadband modulation was demonstrated from 1530nm to 1560nm. The temperature-independent broadband silicon modulator is adaptable to interconnection and communication systems in practice.

Research on the Intermediate Frequency Receiver of L-Band

With the rapid development of wireless communications, there are more and more ​​stringent requirements on the wireless receiver, such as low power consumption, high reliability, low price, as well as smaller size. The design of RF receiver is the key to achieve this goal. According to the actual needs of the project, a double conversion IF receiver is designed. At first, the high frequency signal is changed to a higher IF, and the second output is a zero-IF signal. Experimental results show that the receiver has 100dB gain and a flat bandwidth.

Numerical simulation of supercontinuum generation in liquid-filled photonic crystal fibers with a normal flat dispersion profile

A photonic crystal fiber (PCF) filled with commercial index-matching liquids is designed to control the dispersion properties of PCF. Numerical simulation of supercontinuum (SC) generation in these liquid-filled PCFs is then conducted at a temperature of 25°C. The definition of spectral flatness measure (SFM) is introduced to quantitatively describe the SC flatness. Numerical simulations are performed to study the propagation of femtosecond pulse in the liquid-filled PCFs. Results show that using the index-matching liquids in PCF, the dispersion properties of the PCF can be easily engineered without changing in the geometry. Simulations also show that 50fs pulses with a center wavelength of 1060nm generate relatively flat SC spectra in the 25cm-long PCF with two Oil2-filled rings. With an applied pump power of 24kW, a flat (SFM=0.9670) spectral bandwidth of 700nm (900–1400nm) is achieved. Results further demonstrate that using index-matching liquids to fill the PCF inner ring can exactly control its dispersion properties and generate a flat SC spectrum in the specified wavelength region.

Dispersion Engineering of Slow Light in Ellipse-Shaped-Hole Slotted Photonic Crystal Waveguide

Wideband slow light in an ellipse-shaped-hole slotted photonic crystal waveguide (ESPCW) has been theoretically demonstrated. By adjusting the length of major and minor axes of air holes and tuning the holes position of the second row adjacent to the slot, the group index and bandwidth of slow light can be engineered effectively at the same time. Through the optimization of ESPCW structures by the plane wave expansion (PWE) method, the nearly constant group indices at 46, 80.7, and 215.5 are obtained, and we accordingly attain the flat bandwidths of 4.81, 2.66, and 1.02 nm around the operating frequency of 1550 nm, while the variation of each group index is restricted within ±10% range. Meanwhile, the normalized delay-bandwidth product stays around 0.14, with minimal dispersion on the order of 10 $^6 $ ps $^{2}$ /km for all the cases.

Wide-bandwidth zero-dispersion slow light in MKRs with a two-ring parallel connection structure based on an analogue of electromagnetically induced transparency

Based on an analog of electromagnetically induced transparency (EIT) in microfiber knot resonators with a two-ring parallel connection structure, a wide bandwidth and zero-dispersion slow-light waveguide is proposed. The EIT-like transmission spectrum with the variation of wavelengths for different coupling coefficients is numerical simulated. By appropriately adjusting the coupling coefficients of the two knot rings, a group time delay of about 72.4 ps with a flat wavelength bandwidth of about 82.7 pm and a full width at half-maximum of about 228 pm at one of the induced transparency windows is achieved theoretically. And the group time delay dispersion at the same induced transparency window nearly reaches to zero with a wavelength bandwidth of about 82.7 pm.

TUNABLE ACTIVE FILTERS FOR RF AND MICROWAVE APPLICATIONS

In this paper, we present a low-voltage tunable active filter for microwave applications. The proposed filter is based on a single-transistor active inductor (AI), that allows the reduction of circuit area and power consumption. The three active-cell bandpass filter has a 1950 MHz center frequency with a -1 dB flat bandwidth of 10 MHz (Q ≈ 200), a shape factor (30–3 dB) of 2.5, and can be tuned in the range 1800–2050 MHz, with constant insertion loss. A dynamic range of about 75 dB is obtained, with a P1dB compression point of -5 dBm. The prototype board, fabricated on a TLX-8 substrate, has a 4 mW power consumption with a 1.2 V power supply voltage.

A Broadband Inductorless Active Power Divider for 10 Gbps High Speed Transmissions

A broadband and compact inductorless active power divider is presented in this letter. By using the Darlington cell, the proposed monolithic active power divider demonstrates broad and flat bandwidth of output 1 dB compression point over the 3 dB bandwidth. The gain-bandwidth performance, input matching, and device ratio of the Darlington cell are presented to achieve broad bandwidth. The proposed active power divider exhibits a potential for the high speed transmissions due to its broad bandwidth, low amplitude/phase errors, low and flat group delay.