RF Output Power Research Articles

Multiscale Compact Modelling of UTC-Photodiodes Enabling Monolithic Terahertz Communication Systems Design

Due to the continuous increase in data traffic, it is becoming imperative to develop communication systems capable of meeting the throughput requirements. Monolithic Opto-Electronic Integrated Circuits (OEICs) are ideal candidates to meet these demands. With that in mind, we propose a compact and computationally efficient model for Uni-Traveling Carrier Photodiodes (UTC-PDs) which are a key component of OEICs because of their high bandwidth and RF output power. The developed compact model is compatible with existing SPICE design software, enabling the design of beyond 5G and terahertz (THz) communication circuits and systems. By introducing detailed physical equations describing, in particular, the dark current, the intrinsic series resistance, and the junction capacitance, the model accurately captures the physical characteristics of the UTC-PD. The model parameter extraction follows a scalable extraction methodology derived from that of the bipolar and CMOS technologies. A detailed description of the de-embedding process is presented. Excellent agreement between the compact model and measurements has been achieved, showing model versatility across various technologies and scalability over several geometries.

Reliability and failure analysis in power GaN-HEMTs during S-band pulsed-RF operating

This paper reports a reliability study on two technologies of AlGaN/GaN high-electron mobility transistors (AlGaN/GaN HEMTs) (Device “A” and Device “B”). A failure analysis study is conducted on devices stressed under real operating conditions for radar applications. The devices underwent pulsed-RF long ageing tests and after 11,000 h show a degradation in RF and DC performances (Drop of drain current and RF output power, pinch-off shift, decrease of the maximum of transconductance, lateral translation of transconductance, and increase of gate-lag and drain-lag). Hot electron effects are supposed to be the origin of the observed degradations and trapping phenomena within the passivation or GaN layers. Photon emission microscopy (PEM), Optical Beam Induced Resistance Change (OBIRCH), Electron Beam Induced Current (EBIC) measurements concur with this hypothesis. The three techniques reveal a non-uniform response and an inhomogeneous distribution along the gate fingers, in addition to the presence of some localized spots localized on the gate edge either on the drain side or on the source side. Spectral PEM analysis of these spots identifies a native defect that could be related to crystallographic defects such as dislocations or impurities. Atom probe tomography (APT) analysis on the two technologies of AlGaN/GaN HEMTs supports this hypothesis. APT results show the presence of some chemical impurities like carbon and oxygen. These impurities are in relatively significant concentrations in device “A” which could explain the high level of gate-lag and drain-lag in this device compared to device “B”.

Design and Simulation Investigations of W-Band Second Harmonic Periodically Dielectric-Loaded Gyro-TWT

ABSTRACT In this article, the complete design and beam-wave interaction studies of W-band gyro-TWT amplifier have been presented. The gyro-TWT has been designed to operate at second harmonic TE 02 mode to reduce the magnetic field requirement. A triode-type magnetron injection gun has been designed and optimized for low-velocity spread using E-GUN. A novel, mode selective input coupler with a gradually tapered slotted waveguide has been used to feed the desired TE 02 mode and suppress the reflection and spurious oscillations at the input end (upstream). To abridge the absolute instability of the operating mode and backward wave oscillations caused by spurious modes, a periodic lossy dielectric-loaded RF structure has been adopted. The particle-in-cell simulation of the amplifier predicted a peak RF output power of ∼500 kW with ∼3.6 GHz bandwidth, ∼20% efficiency, and ∼32.2 dB saturated gain for the DC input of 100 kV, ∼25 A with 4% axial velocity spread and velocity ratio of 1.22. Further, to extract the output power with minimum reflection, a double-disc window has been studied. An undepressed curved collector is also designed using E-GUN and its simulation predicted a maximum heat wall loading of ∼0.39 kW /cm2.

SiGe Push–Push VCO for Low-Power C-Band FMCW High-Resolution Radar Applications

In this letter, we present a low-complexity push–push voltage-controlled oscillator (VCO) that achieves over 17% highly linear MHz/V tunable bandwidth. Unlike traditional VCOs, the proposed design does not require dedicated voltage-sensitive reactance components such as varactors or other transistors. The frequency is controlled with the bias voltage of the SiGe transistors which are placed in push–push configuration. The VCO is implemented using discrete components, and occupies 81 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}$ </tex-math></inline-formula> on PCB. The measured phase noise @1 MHz is −103 dBc/Hz, the average power consumption is 18 mW, the RF output power is −1 dBm, and the supply voltage is 3.3 V. The tuning range is 5.15–6.15 GHz, and the figure of merit with tuning (FoMT) at center frequency is −170. The large tunable bandwidth is obtained without using voltages greater than the supply voltage. The linearity and tuning bandwidth are evaluated by implementing the design in a low-power C-band frequency modulated continuous wave (FMCW) imaging radar.

Design of Novel InP/InGaAs Photodetectors With NiO Transparent p-Region and Electrode

In this study, we report a new type of InGaAs/InP photodetector (PD) with nickel oxide (NiO) transparent p-region and electrode. By applying the NiO film, the device does not require the highly doped p-contact layer and the opaque p-contact metal electrode such as the traditional p-i-n PD. The epitaxial layer of the PD is simplified. Meanwhile, the optical power loss caused by the additional absorption in the highly doped p-contact layer can be avoided. With the fully covered transparent p-contact electrode, the PD can be illuminated from the p-side at the same time. The numerical simulation results show that the new structure can improve the 3-dB bandwidth and the RF output power of the PD.

S-Band Bifrequency MILO With Improved Performance

In this article, we present an improved design of a bifrequency magnetically insulated line oscillator (BFMILO). We begin with design expressions for the output section parameters considering transmission line impedance across the extractor. This helps in proper impedance matching so as to maximize the RF power exchange arising out of the intense beam-wave interaction. In order to reproduce more RF energy from the space charge limiting current at the load, a metal plate is inserted inside the collector cavity depth. Two tapered extractor vanes are imposed at the load side along with the stub, to enhance the RF power extraction and proper RF coupling. Simulation results show that the modified collector design generates an RF output power of ~3.8 GW at dual operating frequencies, namely, 3.05 and 3.32 GHz. The peak power conversion efficiency was estimated as 16.17% with an applied voltage of 500 kV and a beam current of 47 kA.

A Rectangular Vane-Type Relativistic Magnetron With Diffraction Output

In this article, a GW-level and high-efficiency $S$ -band eight-cavity relativistic magnetron with diffraction output (MDO) is proposed. A rectangular profile vane-type anode block is adopted to increase the volume of resonators, which leads to a promising higher output power. In particle-in-cell (PIC) simulations, the proposed eight-cavity MDO generates 2.5 GW output power with a power conversion efficiency of 70% when the applied voltage is 460 kV and the axial magnetic field is 0.44 T. The operation mode, $\pi $ -mode, oscillates at 2.75 GHz. The proposed eight-cavity MDO generates an RF output power over 2 GW in a wide range of voltages and magnetic fields, which exhibits its reliable performance in $\pi $ -mode.

Simulation Investigations of High Power Overmoded Relativistic Backward Wave Oscillator with Trapezoidal Resonant Reflector

An S-band high power relativistic backward wave oscillator using a trapezoidal resonant reflector and overmoded slow-wave structure is demonstrated by finite difference time domain based Particle-In-Cell code. The trapezoidal resonant reflector and slow-wave structure are chosen to improve the RBWO power handing capability to gigawatt (GW). The Trapezoidal resonant reflector enhances the pre-modulation during electron beam propagation, thus increasing the generated RF signal overall efficiency and coherency. The particle-in-cell simulation generated an RF output power ~5.4 GW in TM01 mode at ~3.6 GHz in a 2.0 T magnetic field and developed a 13.5 kA current for a 1.2 MV DC cathode voltage. The power conversion efficiency is achieved as ~33 %. Further, the influence of different design parameters on frequency, RF output power, and efficiency are analysed through Particle-In-Cell simulations.

Demonstration of a W-Band Traveling-Wave Tube Power Amplifier With 10-GHz Bandwidth

We present the experimental demonstration of a traveling-wave tube (TWT) power amplifier operating in the W-band (75-110 GHz) frequency range. The device is based on a serpentine waveguide (SWG) amplification circuit, a slow wave circuit type capable of high power and broad instantaneous bandwidth in the upper millimeter-wave range. A 20 kV, 140-mA round solenoid-focused electron beam powers the device. At 20 kV, we measure 215 ± 2 W peak RF output power at 93 GHz with 20.1 ± 0.15 dB saturated gain, pulsed at 0.1% duty. We observe 10-GHz instantaneous amplification bandwidth at 100-W minimum output power, covering the range 88-98 GHz. Operating at 20.8 kV, the TWT produces 285 ± 3 W at 91 GHz with 22.4 ± 0.15 dB gain, and 7 GHz, 3-dB bandwidth. The peak electronic efficiency measured is approximately 10%.

Beam–Wave Interaction Analysis Inside an Azimuthally Partitioned Axially Periodic Disk-Loaded Coaxial Structure for Bifrequency MILO

In this article, the electromagnetic (or RF) behavior of the azimuthally partitioned axially periodic metal disk-loaded coaxial structure was investigated using an equivalent circuit approach in the presence of the electron beam. In the analysis, the linearized Maxwell's fluid equation (also known as Vlasov-Maxwell's equation) was used to analyze the region in which the electron beam was present. The expression for the equivalent series inductance and shunt capacitance per unit length for the equivalent transmission line was derived in the electron beam present and absent case. The derived expressions include all the harmonics effects present inside the structure. Furthermore, the expression of the dispersion relation and temporal growth rate (TGR) was derived using the calculated equivalent series inductance and equivalent shunt capacitance. The output RF power and energy were also calculated analytically and validated through the PIC simulation. The results were compared with the already reported literature, and the relative error between them was below 5%. In addition, the effect of different beam parameters on the TGR behavior was also analyzed.

Power and Efficiency Enhancement of Reltron With Two-Stage RF Output

A novel configuration of a reltron was proposed to enhance its RF output power and efficiency by modifying the conventional design. In the proposed design, an additional power extractor waveguide cavity was put between the output waveguide and the beam dump to recover the remainder energy of the bunched electron beam transporting to the beam dump of the device. The RF electric field profile confirmed $\pi $ /2 mode resonance, ensuring intense electron bunching through the modulation cavity and a stable device oscillation. The 3-D particle-in-cell (PIC) simulation of the device predicted the RF output power of ~240 MW with ~38% efficiency extracted from the conventional output port and ~65 MW with ~10% efficiency from the additional extractor port. The combiner port provided an RF output power of ~295 MW with ~46% efficiency.

Study of mutual injection-pulling between two mutually-coupled single-loop optoelectronic oscillators

This paper analyzes the injection-locking and injection-pulling behavior of two mutually coupled single-loop free-running OEOs with nearby frequencies. We derive the phase dynamics equations of two mutually-coupled OEOs considering weak RF signal injection and the phase stability of the mutually injection-locked system is studied. Also, we present compact closed form expressions for the oscillation frequencies of two mutually injection-pulled OEOs in terms of the injection-ratios and the phase shifts of the mutually injected RF signals. The beat frequency of the mutually injection-pulled system is calculated in terms of the injection ratios. The influence of mutual injection-pulling on the RF output power spectrums of two OEOs are studied. It is shown that the RF output power spectrums of two mutually injection-pulled OEOs are highly asymmetric and strongly depends on the injection ratios. The experimental results corroborating the theoretical findings are given.

Analog radio-over-fiber links with a high SFDR for passive distributed antenna system applications using Lagrange multiplier optimization

An analog radio-over-fiber scheme with a high spurious-free dynamic range (SFDR) is proposed for constructing a passive distributed antenna system (DAS). By developing a Lagrange multiplier constrained optimization model, the best trade-off among RF output power, the polarization incident angle, and the RF power ratio is obtained. Consequently, the third-order intermodulation distortion and second-order harmonic distortion can be suppressed simultaneously simply by varying the polarization incident angle. The simulated and experimental results show that the proposed scheme is effective and feasible. Additionally, this Letter offers valuable insights into the nonlinear optimization, and it may be of great significance in future design and manufacture.

Linearity optimization of multi-octave analog photonic links based on power weighting, polarization multiplexing and bias control.

We present and demonstrate an approach to linearizing analog photonic links (APLs) with substantially enhanced multi-octave spurious-free dynamic range (SFDR). Combining with power weighting, polarization multiplexing and bias control techniques, the proposed approach enables the second-order harmonic distortion (HD2) and third-order intermodulation distortion (IMD3) to be suppressed simultaneously. To maximize the RF output power, an optimization model is established. The simulation results indicate that the maximum RF power can be attained when the power weighting factor and polarization incident angle are equal to 0.5 and 0.34 radians, respectively. The link is validated with a proof-of-principle experiment. The third-order SFDR is 112.3 dB·Hz2/3, corresponding to the improvement of 15.5 dB as compared with a quadrature-biased link. The second-order SFDR reaches as high as 94.6 dB·Hz1/2. Furthermore, the adjacent channel power ratio (ACPR) is measured to be up to 54.6 dBc, which is 5.4 dB greater than that of a quadrature-biased link. Finally, the system tolerances for the RF and optical input power are also investigated in terms of error vector magnitudes (EVMs). Therefore, by introducing optimization model, our scheme provides further insight into the APL linearization technique and a better performance is also achieved.

Power Efficient GaN HEMT High Power Amplifier Design Operating at 5-7GHz Bandwidth

For the next generation applications in mobile communication, radar and satellite communication we need the devices that can operate at high frequencies and high power with minimum power consumption. There is a growing importance in the recent years for the development of GaN transistors.This paper presents design of the power efficient GaN based high power amplifier operating in the bandwidth of 5GHz – 7GHz based on a 12 Watt Discrete Power GaN on SiC HEMT from TriQuint. In this manuscript the design of RF power amplifier, its stability, input and output matching impedance and performance for 5-7GHz is presented. Design and simulations of the power amplifier are carried out using Advanced Design System (ADS). Simulation results of device stability, gain and Power Added Efficiency (PAE) shows good accordance with the specifications and parameters of the device.In the design process, for better correlation in measurement and simulation results precision of passive element models are specially considered. In 1 dB compression point for the designed high power amplifier, the experiment and the simulation results show a Power Efficiency of 68%.

Power Efficient GaN HEMT High Power Amplifier Design Operating at 5-7GHz Bandwidth

For the next generation applications in mobile communication, radar and satellite communication we need the devices that can operate at high frequencies and high power with minimum power consumption. There is a growing importance in the recent years for the development of GaN transistors.This paper presents design of the power efficient GaN based high power amplifier operating in the bandwidth of 5GHz – 7GHz based on a 12 Watt Discrete Power GaN on SiC HEMT from TriQuint. In this manuscript the design of RF power amplifier, its stability, input and output matching impedance and performance for 5-7GHz is presented. Design and simulations of the power amplifier are carried out using Advanced Design System (ADS). Simulation results of device stability, gain and Power Added Efficiency (PAE) shows good accordance with the specifications and parameters of the device.In the design process, for better correlation in measurement and simulation results precision of passive element models are specially considered. In 1 dB compression point for the designed high power amplifier, the experiment and the simulation results show a Power Efficiency of 68%.

Millimeter-Wave Donor–Acceptor-Doped DpHEMT

In this article, we present GaAs millimeter-wave pseudomorphic high-electron-mobility transistor (pHEMT) using sophisticated AlGaAs-InGaAs–GaAs heterostructure with an In0.22Ga0.78As quantum well located inside an external quantum well formed by space charge regions in AlGaAs layers. In a heterostructure with this design, high mobility [5800 cm2/( $\text {V}\cdot \text {s}$ )] and high density ( ${4.7}\times {10}^{{12}}$ cm $^{-{2}}$ ) of two-dimensional electron gas at 300 K were obtained. The localization of hot electrons in an external quantum well leads to an increase in their drift velocity and to enhance the dc and RF performances of the device. A field-effect transistor based on such a heterostructure with a T-gate of $0.14~\mu \text{m}$ in length shows a specific current density of about 0.7 A/mm, transconductance of about 250 mS/mm, gate–drain breakdown voltage in the range 23–31 V, which corresponds to more than 2 W/mm specific output RF power according to a simple estimate. The transistor demonstrates impressive RF characteristics, the maximum stable gain (MSG) of more than 15 dB at 40 GHz and more than 10 dB at 67 GHz, ${f}_{t} = {45}$ GHz and ${f} _{\text {max}} = {250}$ GHz. The MSG at 40 GHz increases with increasing distance between the gates in the drain and is almost constant in the range 25–55 GHz.

Reliability Assessment Of AlGaN/GaN HEMTs on the SiC Substrate Under the RF Stress

This article reports a reliability study on AlGaN/GaN high-electron-mobility transistors under the RF stress. It shows a stabilization of the gate contact after the aging test. However, the degradation of RF performances and dc parameters is noticed. The degradations are mainly due to bulk traps located between gate-source or gate-drain and caused by hot-electron effects. The trap-related phenomena results in a reduction of the drain current and RF output power accompanied with transconductance degradation and pinch-off shift. These traps are characterized by gate-lag and drain-lag measurements and spectral photon emission microscopy. Photo emission measurements reveal an inhomogeneous distribution of light and the presence of native traps that could be related to crystallographic defects such as dislocations or impurities.

H-terminated diamond RF MOSFETs with AlOx/SiNx bi-layer passivation and selectively etched T-shaped gates

This paper reports a novel ALD-AlOx/PECVD-SiNx bi-layer structure to passivate the surface channels of the hydrogen terminated diamond transistors. The upper SiNx was selectively etched to fabricate the robust T-shaped gates, while the lower thin AlOx with high quality was retained as the gate insulator. The fabricated device with gate length of 0.3 μm demonstrated a high current density of 715 mA/mm, a low on-resistance of 8 Ω·mm, and an extrinsic fT/fmax of 10/20 GHz. RF power output characteristics were investigated at 2 GHz and a maximum output power density of 703 mW/mm was obtained at a low drain voltage of −15 V. It reveals that it is a promising solution for high stable and high power diamond RF transistors and microwave integrated circuits by using the AlOx/SiNx passivation structure.

Study on Load-Side Optimization in Bifrequency MILO Source

In this article, we present an in-depth study of bifrequency magnetically insulated transmission line oscillator (MILO) generating RF output power in S-band with azimuthal partition. It is proposed to optimize the parameters across the load side, inserting gold plate in the collector and tuning the collector cavity depth. The proposal aims at enhancing the power conversion efficiency by employing the concept of a tapered extraction region and implementing four stubs. The stubs help to achieve proper impedance matching, subsequently improving the output power. Further, loss-free FR-4 dielectric is used in extractor vanes which helps to reduce the RF power distribution in other modes. The use of gold plate stimulates space charge near the surface and helps in deflecting the electrons toward the interaction cavities. The presence of FR-4 extractor vane helps to generate spoke current near the collector. The proposed system provides improvised RF coupling of the electron beam to the interaction cavities. The peak power efficiency of ~12.7% is achieved through the device. The beam–wave interaction process is illustrated using space charge instability mechanism. Taking into account the Lagrangian of electrons relationship between angular momentum and torque due to angular force is also derived. This in-depth study helps in the deep understanding of magnetic insulation process inside the device toward developing the proficient MILO source.