Self-biased Structure Research Articles

Phase formation, microstructure and gyromagnetic properties of c-axis oriented M-type hexaferrite applied to self-biased circulator

Self-biased structure based on hexaferrite demonstrates potential for achieving planar miniaturization of microwave circulator. Appropriate magnetocrystalline anisotropy field Ha and high squareness ratio Mr/Ms are indispensable for hexaferrite to meet with specific operating frequency and reduce loss of circulator, respectively. Gd3+-Mg2+ co-substitution is introduced to adjust Ha of M-type hexaferrite Sr1-xGdxFe12-xMgxO19 (SrM, x= 0.00, 0.05, 0.10, 0.15, 0.20, 0.25) while maintaining valence equilibrium. A Mr/Ms as high as 0.88 is achieved through ceramic process combined with magnetic field orientation. The ferromagnetic resonance linewidth of 774 Oe is detected by perturbational method based on coplanar waveguide at 43 GHz. Finally, A self-biased circulator using slotted structure based on SrM is designed, showcasing effective circular transmission functionality at Ku band.

Reconfigurable metasurface design via coplanar self-biasing structure

Reconfigurable metasurface enriches the functional integrated design into the originally limited space. Electrical control, through the external power supply to control the electromagnetic response control, is a common and simple control method. However, current methods of electrical control require external biasing circuits and even metallized through-holes to power the metasurface, thus leading the design and machining of the metasurface more complicated. In order to address this problem, we propose a coplanar self-biasing structure with feeder-structure multiplexing. Metasurface design is generated under connectivity control, and the electromagnetic responses under different voltage states are searched. The designed metasurface is fabricated and verified by measurement, which can prove that the metasurface can control one-dimensional far-field scattering beams. Moreover, the deicing function of the metasurface with integrated biasing line is verified by infrared measurement. All the measured results are consistent well with the expected targets, which shows the effectiveness of our ideas. Importantly, our design opens up a new way to simplify the reconfigurable metasurfaces design, which has a wide application value in the dynamic control of metasurfaces.

Detection of inhomogeneous magnetic fields by magnetoelectric composite

Magnetoelectric (ME) composites can be useful due to their wide range of possible applications, especially as sensors of weak magnetic fields at room temperature for magnetocardiography and magnetoencephalography techniques in medical diagnostic equipment. In most works on the topic of ME composites, structures are tested in uniform magnetic fields; however, for practical application, a detailed consideration of the interaction with inhomogeneous magnetic fields (IMF) is necessary. In this work we made measurements of IMF with radial symmetry of individual thin wire with AC voltage with different placements of ME sensor. A ME self-biased structure b-LN/Ni/Metglas with a sensitivity to magnetic field of 120 V/T was created for IMF detection. The necessity of external biasing magnetic field is avoided by a nickel layer and its remanent magnetization. ME composite shows a non-zero ME coefficient of 0.24 V/(cm·Oe) in absence of DC external magnetic field. It is shown that output voltage amplitude from ME composite, which is located in AC IMF, is dependent from relative position of investigated sample and magnetic field lines. Maximum ME signal is obtained when long side of ME sample is perpendicular to the wire, and symmetry plane which divides the long side in two similar pieces contains an axis of the wire. In frequency range from 400 Hz to 1000 Hz in absence of vibrational and other noises a limit of detection has value of (2 ± 0.4) nT/Hz1/2.

A Compact 1.0–12.5-GHz LNA MMIC With 1.5-dB NF Based on Multiple Resistive Feedback in 0.15-μm GaAs pHEMT Technology

In this paper, a 2-stage compact wideband low-noise amplifier (LNA) monolithic microwave integrated circuit (MMIC) with multiple resistive feedback (MRFB) is presented. From the DC point of view, the proposed MRFB functions as a self-biasing structure to bias transistors in the optimal condition, improving the noise figure (NF) and linearity. Meanwhile, by employing MRFB with source degeneration and input inductor, the proposed LNA achieves wideband flat gain at the AC side. In comparison with traditional topologies, a wide bandwidth of more than 11.5 GHz with low noise figure of less than 2.5 dB can be achieved. To verify the proposed LNA structure, a chip prototype is fabricated in a 0.15- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> GaAs E-mode pHEMT process with a compact die size of only 0.75 mm2 including all the testing pads. From the measurement results, the proposed LNA circuit features a 1.0 to 12.5 GHz 3-dB working bandwidth (172% fractional bandwidth), 23.6 peak gain, 1.51 dB minimum NF, 66.7± 15 ps group delay, and 24.3/12.6 dBm best OIP3/OP1dB, respectively. The total DC power is around 87.5 mW from a single 2.5-V power supply.

A nano-power sub-bandgap voltage and current reference topology with no amplifier

A sub-bandgap current and voltage reference operating at ultra-low quiescent current is proposed for energy harvesting and battery-operated systems. Using a single bipolar junction transistor (BJT) and no operational amplifier (opamp), the current reference is generated from proportional-to-absolute-temperature (PTAT) and complementary-to-absolute-temperature (CTAT) voltages combined in a simple three-branch self-biased structure, while the voltage reference is derived by driving the current reference to a temperature-insensitive resistor. The line sensitivity (LS) is enhanced by incorporating cascode devices into the original configuration. Designed in a 0.18-µm standard CMOS process, the proposed architecture occupies an active area of 609 µm × 755 µm with around 47 nA current consumption regardless of temperature. The generated current and voltage references are 6.7 nA and 180 mV, and their temperature coefficients (TC) are 32.76 ppm/°C and 34.80 ppm/°C across the temperature range from −40 to 120 °C, respectively. The minimum supply voltage is 1.1 V, and the line sensitivity of the voltage and current reference are 0.031%/V and 0.03%/V, respectively, over the supply voltage range of 1.1–1.8 V.

Self-Biased Bidomain LiNbO3/Ni/Metglas Magnetoelectric Current Sensor.

The article is devoted to the theoretical and experimental study of a magnetoelectric (ME) current sensor based on a gradient structure. It is known that the use of gradient structures in magnetostrictive-piezoelectric composites makes it possible to create a self-biased structure by replacing an external magnetic field with an internal one, which significantly reduces the weight, power consumption and dimensions of the device. Current sensors based on a gradient bidomain structure LiNbO3 (LN)/Ni/Metglas with the following layer thicknesses: lithium niobate—500 μm, nickel—10 μm, Metglas—29 μm, operate on a linear section of the working characteristic and do not require the bias magnetic field. The main characteristics of a contactless ME current sensor: its current range measures up to 10 A, it has a sensitivity of 0.9 V/A, its current consumption is not more than 2.5 mA, and its linearity is maintained to an accuracy of 99.8%. Some additional advantages of a bidomain lithium niobate-based current sensor are the increased sensitivity of the device due to the use of the bending mode in the electromechanical resonance region and the absence of a lead component in the device.

Strong electric field tuning of magnetism in self-biased multiferroic structures

A new type of multiferroic heterostructure has been proposed in this work with strong electric field tuning of magnetism. It is composed of a self-biased magnetic layered structure with perpendicular magnetic anisotropy (PMA) and one piezoelectric substrate. Two configurations were investigated by a modeling approach, Ni/Ni/Ni/PMN-PT with Cu as spacer and Terfenol-D/CoFeB/Ni/PMN-PT. Magnetic multilayers at their resonance exhibit multiple absorption peaks from acoustic and optical modes of spin interaction between adjacent magnetic layers. A piezoelectric substrate transfers electric field induced strain to adjacent magnetic layer and thus shifts resonance frequencies of the multiferroic structure by tuning magnetic effective fields through magnetoelastic coupling. It has been demonstrated computationally that the resonance frequencies for the simulated structures could be up to 76 GHz under zero magnetic bias field. A larger tunability (> 100%) is achieved with applied electric field to the PMN-PT [011] substrate. Resonance mode selectivity is present in the configuration Terfenol-D/CoFeB/Ni/PMN-PT wherein one desired mode exhibits a much higher tunability compared to other modes. This enables the total mode number to be tuned by merging or diverging different modes under E-field.

A simple and high performance charge pump based on the self-cascode transistor

A novel charge pump for phase locked loops application based on the self-cascode (SC) transistor is presented. The proposed charge pump is simple and adds just a few number of transistors to basic charge pump circuit. The SC transistor is self-biased and has high output impedance and lower voltage headroom. Threshold voltage reduction method is used in SC transistor to reduce transistor size, increase the output resistance and help to improve the self-biased structure. The post layout simulation for the charge pump with SC transistor is performed using 180 nm CMOS technology. Based on the Monte Carlo process variation and corner case simulation a 2% current mismatch over the voltage range of 0.35–1.48 V is observed.

A low-power low-noise amplifier with fully self-biased feedback loop structure for neural recording

This paper presents a fully self-biased, low-power LNA for neural recordings. Due to the capacitor coupling and low-supply voltage in LNA, the appropriate dc bias voltages for saturating the input transistors NMOS and PMOS of LNA should be separately provided. This paper focuses on the effects of different feedback ways to obtain input dc bias voltage, and proposes a completely self-biased structure to obtain the bias voltage directly from the inner nodes of the circuit. This connected way avoids using extra dc biasing circuit totally, saves capacitor area effectively and reduces the high-pass corner frequency greatly. Furthermore, the proposed method eliminates the likelihood for initial DC latch-up in the traditional way, making the circuit more stable. Simulated in a 0.18-µm CMOS process, the LNA consumes 1.2 µA from a 0.6 V supply, and achieves an input referred noise of 4.98 µVrms (1–10 kHz), corresponding to a noise efficiency factor of 2.13. Simulated CMRR and THD exceed 77 dB and 75 dB, separately.

An improved non-linear current recycling folded cascode OTA with cascode self-biasing

An improved non-linear current recycling folded cascode operational transconductance amplifier with cascode self-biasing is presented in this paper. To improve the gain-bandwidth and slew rate of traditional current recycling folded cascode amplifier, the adaptive biasing class-AB input stage and non-linear current recycling output stage are utilized to improve the effective transconductance and maximum output current. In addition, a cascode self-biasing structure is applied to the output stage to prevent the PMOS current mirror from entering the linear region during the large signal current. Both the conventional and the proposed current recycling folded cascode amplifier are all designed on SMIC 0.18 μm. The simulation results show that the proposed non-linear current recycling amplifier achieves 2.1 times the gain-bandwidth and 5.4 times the slew rate that of conventional current recycling amplifier, with only 25% extra power consumption.

Design of a Bandgap Voltage Reference Working in Subthreshold Region with Low Voltage, High Precision in a Wide Temperature Range

In this paper, a bandgap voltage reference working with high precision in a wide temperature range is proposed. The proposed bandgap voltage reference adopts self-biased structure without using resistor and operational amplifier. It adopts 6 stages of the proportional to absolute temperature circuit to increase temperature range. And it uses linearity compensation circuit to improve the temperature coefficient. Supported by GSMC 0.13 μm technology, with 1.2V supply voltage, the proposed bandgap voltage reference can generate a steady 66 mV reference voltage. Within the temperature range of -100 to 145 °C, the temperature coefficient is 8.5486 ppm/°C and the line sensitivity is 0.19245 mV/V. And the bandgap voltage reference covers a core area of 0.00396 mm2.

Self-biased magnetoelectric charge coupling in transducer of SmFe2, Pb(Zr,Ti)O3 stack, and stepped horn substrate with multi-frequency effect

This paper presents a broadband, self-biased magnetoelectric (ME) charge coupling in a transducer comprising of a negative magnetostrictive SmFe2 plate, a piezoelectric Pb(Zr,Ti)O3 (PZT) stack, and a stepped horn substrate. By using the SmFe2 plate with a large anisotropic field, an outstanding self-biased piezomagnetic effect is realized. The horn serves as a waveguide with multiple resonances and converges vibrating energy excited by the SmFe2 plate from the wide side to the narrow side, which results in a higher vibrating magnification at the position of the PZT-stack. Then, a strong mechanical-electric coupling is realized by the use of the PZT-stack with high capacitance. Consequently, several large peaks of ME charge response with magnitudes of 1.02–18.99 nC/Oe in the 0.1–50 kHz range are observed at zero-biased magnetic field. This demonstrates that the proposed broadband self-biased structure may be useful for multifunctional devices such as low frequency AC magnetic field sensors or multi-frequency energy harvesters.

Two-path inverter-based low noise amplifier for 10–12 GHz applications

This paper presents a two-path inverter-based low-noise-amplifier (LNA) in TSMC 0.18µm CMOS technology for 10–12GHz frequency band applications. The primary path provides a flat and high enough gain within the interested frequency band. The secondary path ensures the input impedance matching for the proposed LNA. A peaking inductor is applied to the gate of inverters NMOS transistor. With this technique, the parasitic capacitance of MOS transistors will be appropriately compensated at high frequencies. Furthermore, resistive shunt feedback is applied to CMOS inverters in order to extend the amplifier bandwidth. The feedback resistor makes the LNA to be a self-biased structure. The proposed LNA consumes 10.3mW from a 1.8V supply. The amplifier gain is high enough and S21=12.8dB while the gain flatness is 0.55dB in the whole frequency band. The structure is optimized for minimum noise figure (NF) and the NF is 2.1–2.3dB within the bandwidth. The input impedance is matched and S11 is less than −10dB. The linearity of the LNA is sufficient and IIP3 is equal to −11dBm.

Self-Biased Magnetoelectric Composites: An Overview and Future Perspectives

Abstract Self-biased magnetoelectric (ME) composites, defined as materials that enable large ME coupling under external AC magnetic field in the absence of DC magnetic field, are an interesting, challenging and practical field of research. In comparison to the conventional ME composites, eliminating the need of DC magnetic bias provides great potential towards device miniaturization and development of components for electronics and medical applications. In this review, the current state-of-the-art of the different self-biased structures, their working mechanisms, as well as their main characteristics are summarized. Further, the nature and requirement of the self-biased magnetoelectric response is discussed with respect to the specific applications. Lastly, the remaining challenges as well as future perspective of this research field are discussed.

Versatile CMOS bio‐potential amplifier for high‐density neural recording applications

A fully-integrated low-power and area-efficient bio-potential amplifier for high-density neural recording applications is presented. Using a self-biased amplifier structure, the bio-potential amplifier can operate at a lower power with a reduced active area. The Miller capacitance and area-efficient pad techniques harnessed in the amplifier also help to dramatically shrink the area of the amplifier. This implantable bio-potential amplifier was fabricated using a 0.35 µm CMOS process and was verified on a bench top by observing ex vivo biological signals.

A LOW POWER AND VARIATION-INSENSITIVE CURRENT-MODE SIGNALING SCHEME

Process and supply variations all have a large influence on current-mode signaling (CMS) circuits, limiting their application on the fields of high-speed low power communication over long on-chip interconnects. A variation-insensitive CMS scheme (CMS-Bias) was offered, employing a particular bias circuit to compensate the effects of variations, and was robust enough against inter-die and intra-die variations. In this paper, we studied in detail the principle of variation tolerance of the CMS circuit and proposed a more suitable bias circuit for it. The CMS-Bias with the proposed bias circuit (CMS-Proposed) can acquire the same variation tolerance but consume less energy, compared with CMS-Bias with the original bias circuit (CMS-Original). Both the CMS schemes were fabricated in 180 nm CMOS technology. Simulation and measured results indicate that the two CMS interconnect circuits have the similar signal propagation delay when driving signal over a 10 mm line, but the CMS-Proposed offers about 9% reduction in energy/bit and 7.2% reduction in energy-delay-product (EDP) over the CMS-Original. Simulation results show that the two CMS schemes only change about 5% in delay when suffering intra-die variations, and have the same robustness against inter-die variations. Both simulation and measurements all show that the proposed bias circuits, employing self-biasing structure, contribute to robustness against supply variations to some extent. Jitter analysis presents the two CMS schemes have the same noise performance.

Self-Biased Differential Dual Spin Valve Readers for Future Magnetic Recording

For future magnetic recording, one challenge is that the shield to shield spacing (SSS) of readers cannot be scaled down to achieve the linear density requirement. A differential dual spin valve (DDSV) has been proposed to improve the linear resolution as it does not rely on the magnetic shields to diminish the interference from adjacent bits. The side reading becomes more and more challenging as the track width shrinks to below SSS to accommodate high track density, in particular for a DDSV reader in which no magnetic shield or larger SSS is used. A self-biased DDSV structure is proposed to replace the conventional abutted junction stabilization scheme. In the self-biased DDSV readers, two side shields are put at the both sides of the sensor across the track direction in the replacement of the hard bias (HB). The stray fields from the two free layers in the DDSV sensor bias each other to stabilize the domain structure of the free layers. Preliminary analysis shows that the self-bias DDSV is also robust against the spin torque-induced magnetic instability. Simulation results indicate that the self-biased DDSV reader has much better reading sensitivity for the opposing fields generated by magnetic transitions than HB-stabilized sensor. It is found that for DDSV readers, the mag-noise is less significant due to a larger signal field and thicker free layer. Current perpendicular to the plane (CPP)-DDSV sensors have been fabricated and show very good differential effect in the real operating mode. The magnetoresistance performance of individual spin valve in CPP-DDSV sensors has been obtained through measurements with applied field and pinning field parallel to the easy axis of the free layer.

A $2\times V_{\rm DD}$-Enabled Mobile-TV RF Front-End With TV-GSM Interoperability in 1-V 90-nm CMOS

A 2 × VDD-enabled mobile-TV RF front-end with TV-GSM interoperability is described. It is an on/off-chip codesign employing externally three customized UHF/VHF preselect filters, an RF switch, and a balun. The integrated part includes: 1) a cascode-cascade inverter-based low-noise amplifier that features a high gain-to-power efficiency; 2) a linearized C-2C attenuator using reliably-overdriven MOS switches; 3) an inductive-peaking feedforward path that evens out the passband variation; and 4) two cascode I/Q mixer drivers capable to drive passive mixers with small gain and bandwidth reduction. Gate-drain-source engineering and self-biased structures are the keys enabling performance optimization with low power and no reliability risk. Fabricated in a 90-nm CMOS process with 1-V thin-oxide devices, the RF front-end measures 68-dB rejection at GSM-900 uplink, 0.7-dB passband roll-off, 3.9-dB noise figure, and -5.5-dBm third-order intercept point at a maximum voltage gain of 26.2 dB. The core occupies 0.28 mm2 and draws 15 mW. The achieved power-performance metrics compares favorably with the prior state of the art.

A Corona-Charged Self-Biased Radiation Dosimeter

In this letter, we report on a new solid-state structure for an integrating microdosimeter. The device consists of a silicon bar enclosed by a compound dielectric bilayer of silicon dioxide/parylene acting as an ionization getter/electret. The dielectric bilayer is corona charged to establish a self-biasing structure that achieves high sensitivity without the need for a large applied voltage. For a 0.5 × 0.7 × 0.3 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> sensor with a dynamic range of 15 Gy, a sensitivity of 50 kΩ/Gy was measured.

NUMERICAL STUDY OF BEHAVIOURAL SUB-HARMONICALLY PUMPED MIXER IN A NOVEL STRUCTURE

A Sub Harmonically Pumped (SHP) mixer suitable for direct conversion receiver in 3G mobile frequency band is presented. This mixer is realized with N anti-parallel diode pairs (APDPs) and designed in self-biased structure to obtain minimum noise flgure and conversion loss. In this paper, a simultaneous signal and noise analysis CAD routine to analyze a circuit consists of Arbitrary Number of anti- parallel diode pairs in self-biased structure is proposed. Then the results of this CAD routine are conflrmed with other method. The mixer is optimized to obtain a maximally ∞at conversion gain and minimum Noise Figure over various LO powers. The proposed CAD is used to obtain the optimum number of APDPs. Also the optimum self-biased resistance and output load are calculated.