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Neural signal recording and optical stimulation using implantable devices have become a ubiquitous method to treat brain disorders, yet there lie some shortcomings, such as size, weight, and functionalities of the implants. This work presents a commercial off-the-shelf (COTS) component-based miniaturized wireless optogenetic headstage with simultaneous optical stimulation and electrophysiological recording for freely moving rats. The system includes a battery-based neural stimulator consisting of a low-dropout (LDO) regulator, an oscillator, and a μ LED. The electrophysiological signal recording system includes an intracortical neural probe implemented on a shape memory polymer (SMP) substrate, an array of neural amplifiers with an integrated analog-to-digital converter (ADC), a transceiver IC, and a ceramic antenna. A digital sub-1-GHz transceiver integrated with a low-power microcontroller (MCU) is used to transmit the acquired neural data to a remote receiver unit, followed by offline spike detection and sorting in LabVIEW. The front-end recording amplifiers provide a gain of 45.7 dB with the input-referred noise of 2.4μVrms . The integrated multiplexer (MUX) with the ADC allows sampling of the amplified voltage at a configurable sampling rate of 160–480 kSamples/s. The total power consumption of the stimulation and the recording system is 23 mW. The dimension of the headstage device is 13.5×21.3 mm, weighing 4 g without the battery. The system is experimentally validated in an in vivo setting by placing the headstage on the head of a male rat and recording the neural signals from the ventral tegmental area (VTA) of the brain. This integrative neural signal recording and spike sorting approach would be useful for the development of a closed-loop neuromodulation system. 

A high-gain SIW elliptically polarized antenna combination of a dipole and loop antenna based on substrate-integrated waveguide (SIW) is proposed for millimeter-wave (mm-wave) applications. The dipole and loop antenna are differentially excited by a longitudinal slot etched on the top layer of SIW. The proposed combination of dipole and loop antenna forms a parallel electric dipole and magnetic dipole, which radiates two orthogonal electric field components and 90∘ phase difference in the far-field radiation when they are excited with the same phased signal. The proposed antenna achieves a realized gain of 8.346 dBi, with a radiation efficiency of 89.40% at 60 GHz. 

This paper presents the design and simulation of a 24 GHz 1×5 series-fed microstrip patch antenna array and its performance analysis with structural deformation. The optimized design comprises of 5 antenna elements arranged in series, where the entire design is symmetric about the center antenna element. The parameters such as S11 , gain vs. theta plots are analyzed with and without the material deformation. The shape deformation analysis is indeed needed to determine the performance efficiency of the designed antenna when deployed on drones, where the antenna needs to be flexible enough to be aligned with the curvature of drone's body. The simulation results are analyzed to see how best can the proposed antenna array can perform with the structural deformation. 

This paper presents modeling and optimization of the steering range of a microstrip planar phased array antenna to steer the unidirectional near-field focused beam towards a certain direction. This antenna can be implemented in headstage-based neural stimulation system and wireless recording system for optogenetic neuromodulation applications. The proposed phased-array antenna consists of sixteen elements that are designed to provide a uniform power transmission over the 27 cm×23 cm×16 cm rat behavioral cage area. The proposed transmitter (TX) antenna implements a near-field-based wireless power transmission system operating at 2.4 GHz frequency. The phased array antenna steers the beam from -30° to 60° in the elevation plane by feeding the individual elements with different phases using four 4-bit phase shifters. A design analysis of the beam-steering approach of the phased array antenna is presented and the corresponding simulation and measurement results are included in this paper. 

This paper presents a high-gain and broadband radial elliptical-slot array (RESA) antenna with side-lobe mitigation technique for low-cost satellite communication systems. The aperture of the proposed slot array antenna comprises a set of orthogonal elliptical slots with monotonic slot length variation alongside the radius of the aperture. The design comprises radiating slotted top plate and bottom ground plate parallel to one another separated by an optimal distance of 5.25 mm which is 1.05λ . The design is back-fed using a disk-head radiator probe. The overall dimensions of the proposed slot array antenna with the air-gap taken into account are 300×300×5.75mm3 . Simulation results show that the proposed slot array antenna has a broadband operating frequency range from 45 GHz to 110 GHz and beyond, covering both V and W frequency bands with a fractional bandwidth of 88.8%. The peak gain of the proposed design is 35.6 dBi at 60 GHz. The array exhibits a maximum half-power beam width of 9.5°, a low sidelobe magnitude of - 4.12 dBi and a overall simple design indicates its suitability for low-cost SATCOM (satellite communications) applications. 

This paper presents a highly efficient single-layer substrate-integrated waveguide (SIW) based leaky-wave antenna (LWA) for the millimeter-wave unmanned aerial vehicle (UAV) communication system. The leaky wave-based radiating part of the unit cell includes a combination of two Y-shaped slots with 46° stretched V etched on the top SIW, resulting in a W-shaped structure. The proposed array achieves a high gain of 13.47 dBi for the frequency range of 56.3 GHz to 63.4 GHz covering the unlicensed band, with a fine matching level below -21 dB. Using the leaky wave antenna's frequency scanning capability, the proposed antenna exhibits a scanning range of 38°. The designed antenna shows a promising solution for the UAV-to-UAV applications due to its low profile and compactness and is well-suited for the single-layer low-cost printed circuit board fabrication process using Rogers RT 5880 as substrate. The radiation pattern for the achieved bandwidth shows an average half-power angular beamwidth of 12.1°, resulting in a radiation efficiency of more than 62% for the elements arranged uniformly at a distance of 0.456λ . Following an overall low-profile compact size of 6.48×4 λ corresponding to 3.24×0.2 cm and improved performance, the antenna achieves an elliptical polarization at 60 GHz for an axial ratio equal to 3.5 dBi. 

Miniaturization of the neuromodulation system is important for non-invasive or sub-invasive optogenetic application. This work presents an optimized wireless power transfer (WPT) system integrated with an on-chip rectification circuitry and an off-chip stimulation circuitry for optogenetic stimulation of freely moving rodents. The proposed WPT system is built using parallel transmitter (TX) coils on printed circuit board (PCB) and wire-wound based receiver (RX) coil followed by a seven-stage voltage doubler and a low dropout regulator (LDO) circuit designed in 180 nm standard Complementary Metal Oxide Semiconductor (CMOS) process. A pulse stimulation is used to stimulate the neurons which is generated using a commercially available off-the-shelf (COTS) components based oscillator circuit. The intensity of the stimulation is controlled by using a COTS based LED driver circuit which controls the current through the μ LED. The total dimension of the RX coil is 8 mm × 3.4 mm. The maximum power transfer efficiency (PTE) of the proposed WPT system is ∼ 35% and the power conversion efficiency (PCE) of the rectifier is 52%. The proposed system with reconfigurable stimulation frequency is suitable for exciting different brain areas for long-term health monitoring. 

This paper presents the design of a 23.7 to 29.9 GHz wide tuning range VCO (Voltage Controlled Oscillator) designed using a 180 nm CMOS process. In order to achieve a good phase noise performance and get a wide frequency tuning range, cross-coupling and gate biasing techniques are utilized in the proposed cross-coupled LC VCO architecture. The simulated phase noise of −130 dBc/Hz is achieved at a 1 MHz offset. With the supply voltage of 1.8 V, the total power consumption of the VCO is 32.04 mW. The proposed VCO has good performance in terms of low-phase noise and has a wide frequency tuning range, which makes it highly suitable for millimeter wave-based applications.