Tunable Power Amplifier Research Articles

Modeling and analysis of single-mode widely tunable all-fiber Ho-doped CW master oscillator power amplifier system

We report the design of an all-fiber single-mode polarization maintaining widely tunable Ho-doped master oscillator power amplifier (MOPA) system operating in the wavelength range of 2005-2135 nm based on a pre-amplifier and two power amplification stages. The single clad Ho-doped active fibers in the ring cavity based master oscillator, pre-amplifier, and power amplifiers are pumped using 1950 nm semiconductor laser diode pump sources. The amplification of the MOPA system is investigated over the entire spectral range of 2005-2135 nm. The highest output power achieved by the continuous wave (CW) Ho-doped MOPA system is 43 W at a wavelength of 2028.6 nm using pump power of 20 W with power conversion efficiency (PCE) of 90% for second power amplifier while the total pump power of Ho-doped MOPA system is 45 W. Optical bandpass filters (OBPFs) are employed between different stages of MOPA system to enable amplification over the wider spectral range of 2005-2135 nm by suppressing the amplified spontaneous emission (ASE). Not using OBPFs results in amplification that is limited to the spectral range of 2045-2130 nm. Therefore, a penalty of 45 nm can be avoided at the expense of using the OBPFs between different stages of MOPA system. This flexible MOPA system can be used in multiple applications, especially for space-borne high power transmitters operating in atmospheric transmission windows.

A novel dual mode configurable and tunable high-gain, high-efficient CMOS power amplifier for 5G applications

This paper presents a novel dual mode configurable and tunable power amplifier (PA) that achieves a wide-bandwidth and high gain across a operational frequency spectrum of 20 to 30 GHz. The proposed PA used two-stage tunable PA which can be configured as a tunable synchronous mode or tunable stagger-tuned mode PA. PA is implemented by using a distortion-free varactor at the input and output tank of PA. The designed PA includes a high-Q CMOS active inductor (CAI) which provides a widely tunable output matching network. The resistive feedback is used for self-biasing in the designed PA which helps to enhance the linearity, stability of common source (CS) amplifier. The inter-stage impedance matching network consists of shunt and series resonance circuits are employed for maximum power added efficiency (PAE). Furthermore, the capacitive coupled reuse technique is implemented in each stage between the cascaded transistor to reduce the power consumption. A proposed PA is designed using a 65 nm CMOS technology. A measured power gain at the synchronous operation of PA is 28.4 ±0.5 dB with 1.31 GHz bandwidth while power gain at staggered operation is 22.1 ±0.5 dB with 3.71 GHz bandwidth. The measured saturated power (Psat) is 14.21 dBm and the noise figure (NF) is 5.2 dB. The group delay (GD) variation for staggered operation is 57 ±10 ps from 20-30 GHz. A proposed PA exhibits good linearity (IIP3) of 14.5 dBm and PAE is 47.5 % at 24 GHz. The power consumption of a designed PA is 48.56 mW with a supply voltage of 1.2 V.

Fully integrated CMOS tunable power amplifier using reconfigurable input/interstage/output matching networks

This paper presents a two-stage tunable power amplifier (PA) fully-integrated in 130 nm CMOS process. This multi-band PA consists of reconfigurable input, interstage, and output matching networks in order to tune the center frequency in use. The proposed tunable power amplifier enables three different bands with center frequency of 900 MHz, 1450 MHz, and 1900 MHz. By switching these bands, the designed power amplifier covers frequency range of 700 MHz–2200 MHz known as Long-Term Evolution mobile network. As a result, the proposed tunable power amplifier obtains small-signal gain (S21) of 27.8 dB/29.4 dB/28.6 dB, saturated output power (Psat) of 22.4 dBm/23.0 dBm/23.2 dBm, and power added efficiency of 21.0%/23.7%/25.0% at three targeted frequency bands, respectively. The proposed fully-integrated triple-band power amplifier chip layout occupies an area of 2.25 mm2 including bond pads.

Initial verification of a bandwidth tunable Ku-band power amplifier designed by the HySIC concept

Initial verification of a bandwidth tunable Ku-band power amplifier designed by the HySIC concept

A 0.75–2.5-GHz All-Digital RF Transmitter With Integrated Class-E Power Amplifier for Spectrum Sharing Applications in 5G Radios

We propose a digitally intensive, reconfigurable RF transmitter with an integrated, tunable Class-E power amplifier (PA) which can be configured to operate from 0.75 to 2.5 GHz in discrete bands, while delivering an output power of 11.5 dBm up to 1.5 GHz and 6.5 dBm up to 2.5 GHz. Digital signal processing is exploited to suppress sampling spurs up to the harmonics of the carrier, thus eliminating the need for sharp RF filters. The proposed techniques make the transmitter adaptable to signals of different bandwidths and to different carrier frequencies with minimal overhead in power and area when compared to other digital transmitter designs. Digital predistortion is used to linearize the PA. The transmitter also includes clock correction circuitry for correcting duty cycle and quadrature errors. A generic design methodology is mathematically developed for a reconfigurable Class-E PA with a fixed series inductor. This transmitter scales well with technology and can be potentially used for spectrum sharing (SS) applications in fifth generation (5G) radios. Implemented in a 130-nm CMOS technology, the proposed transmitter occupies an area of 1 mm2. A maximum output power of 13.7 dBm with a maximum efficiency of 27% is obtained at 1 GHz.

Fast Optimization Algorithm for Evanescent-Mode Cavity Tuner Optimization and Timing Reduction in Software-Defined Radar Implementation

Dynamic spectrum allocation will require cognitive radar transmitters to change operating frequency and bandwidth in real time. This will require high-power reconfigurable circuitry to improve radar performance by simultaneously increasing 1) the output power of the transmit waveform and 2) the power-added efficiency of the power amplifier. This circuitry is also used to mitigate cochannel interference by maintaining sufficiently linear performance so that the output waveform conforms to a given spectral mask. In this approach, a 90-W evanescent-mode cavity tuner is reconfigured using a specially designed gradient search to find the best combination of resonant cavity position numbers. This approach will be much more flexible for field use than typical Smith-chart-based load-pull searches, which require a characterization that is susceptible to drift. Experimental results are presented showing that the efficiency, output power, spectral performance, and estimated maximum radar detection range are improved significantly by retuning the matching network at each operating frequency. Additionally, this article discusses innovations to reduce or eliminate time bottlenecks in a cognitive radar system for impedance tuning, reducing the time needed for complete impedance tuning searches from minutes to seconds. This significant timing reduction makes tunable power amplifiers a feasible option for future use in spectrum sharing by cognitive radar systems.

Concept for Continuously Tunable Output Filters for Digital Transmitter Architectures

This paper presents a novel output filter approach for continuously frequency-tunable digital power amplifiers, suitable for future seamless and band-less applications in 5G, e.g. for cognitive radios (CR). The presented tunable output filter is based on a multi-bandstop lowpass response to regenerate the original microwave signal at the output of the digital amplifier stage by suppressing unwanted frequency components. Compared to conventional tunable bandpass solutions, it offers higher tunability, higher linearity, good power handling capability and moderate losses especially around the carrier frequency. A tunable power amplifier (PA) demonstrator consisting of a 4-stage digital GaN PA MMIC and the novel tunable filter, is designed and fabricated for a carrier frequency range from 1 GHz to 3 GHz. Tunability is achieved by using commercial barium strontium titanate (BST) varactors. Small signal measurements were performed to evaluate tunability and suppression capabilities of the novel filter structure, which reveal a frequency tunability of 67% with a suppression level of at least 13 dB for the undesired frequency components. The proposed filter structure exhibits a linearity over the tuning range with an OIP3 between 66 dBm to 70 dBm and high power handling capability. Finally, the performance analysis of the tunable PA demonstrator shows an peak efficiency of 70%. Due to frequency limitations of the used PA stage, the efficiency slowly degrades to 20% at the upper frequency band edge. Simultaneously, the output power varies between 27 dBm to 31 dBm.

Extended 9.7 nm tuning range in a MOPA system with a tunable dual grating Y-branch laser.

In this Letter, we present a tunable Y-branch hybrid master oscillator power amplifier (MOPA) with 5.5W output power, emitting between 973.7 and 983.4nm. The MO is a monolithic Y-branch distributed Bragg reflector (DBR) diode laser, which is collimated and coupled into a tapered amplifier using cylindrical microlenses in a compact 25 mm×25 mm conduction cooled laser package. The wavelength spacing between the two laser branches is 2.2nm. Each branch can be electrically tuned by up to 7.5nm of quasi-continuous wavelength tuning, which in combination covers up to 9.7nm of spectral range. Over this range, an output power variation of 0.5% and 0.2% is observed for the left and right arms, respectively, while maintaining a spectral width of less than 17pm. In addition, the MOPA system can be operated as a dual-wavelength system by operating both branches simultaneously. The presented device is suitable for nonlinear frequency conversion applications.

Self-Optimizing IoT Wireless Video Sensor Node With In-Situ Data Analytics and Context-Driven Energy-Aware Real-Time Adaptation

It is well understood that data-acquisition by distributed sensors and subsequent transmission of all the acquired data to the cloud will produce a “data deluge” in next-generation wireless networks leading to immense network congestion, and data back-logs on the server which will prevent real-time processing and control. This motivates in situ data analytics in energy-constrained wireless sensor nodes that can perform context-aware acquisition and processing of data; and transmit data only when required. This paper presents a camera-based wireless sensor node with a self-optimizing end-to-end computation and communication design, targeted for surveillance applications. We demonstrate support for multiple feature-extraction and classification algorithms, tunable processing depth and power amplifier gain. Depending on the amount of information content, accuracy targets and condition of the wireless channel, the system choses the minimum-energy operating-point by dynamically optimizing the amount of processing done on the sensor itself. We demonstrate a complete system with ADI ADSP-BF707 image processor, OV7670 camera sensor, and USRP B200 software defined radio; and achieve $4.3\times $ reduction in energy consumption compared with a baseline design.

Hybrid Integrated Microfluidic Channels on Multilayer Organic Substrate and on Copper for Tuning and Cooling an RF Reconfigurable S-/C-Band GaN-Based Power Amplifier

In this paper, a gallium nitride (GaN)-based power amplifier (PA) is cooled and tuned thanks to multifunctional hybrid microfluidic channels integrated on a multilayer organic substrate composed of liquid crystal polymer and ceramic-filled polytetrafluoroethylene. The tuning microchannels are integrated in the organic materials, while the cooling microchannels are micromachined in a copper carrier. The tuning allows the PA to switch the frequency of operation from 2.4 to 5.8 GHz and vice versa. Heat removal is achieved by the motion of distilled water below the GaN die, while tuning is achieved by swapping air and acetone inside the source and load matching network microchannels. The novel idea behind the design of such tunable PAs relies on the design of microfluidically tunable matching networks. For the first time, tunability parameters are introduced and a generic methodology is described for the design of microfluidically tunable matching networks for any dies, frequencies, fluids, or stackups. The measured power added efficiency (PAE) and output power (P out ) are: 1) PAE = 33.9% and P out = 37.1 dBm at 2.4 GHz with acetone and 2) PAE = 51.1% and P out = 37.9 dBm at 5.8 GHz with air. The liquid cooling seems to have no effect on P out for all measurements but shows a 1.5% increase in PAE for the 5.8-GHz measurements.

Design of a tunable sequential power amplifier

ABSTRACTA tunable sequential power amplifier (SPA) is presented in this article. The proposed SPA, including a tunable coupler, a carrier amplifier, a peaking amplifier, and a combining coupler is fabricated on Isola I‐TeraMTRF boards with 3.45 dielectric constant and 0.508 mm substrate thickness. A conventional SPA (nontunable) is also designed for reference and performance comparison. Measurement results show that the tunable SPA provides about 2 dB higher gain and 1 dB higher power output comparing with the reference design. The measurement results match well with the analysis. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2899–2901, 2015

A New Frontier in Ultralow Power Wireless Links: Network-on-Chip and Chip-to-Chip Interconnects

This paper explores the general framework and prospects for on-chip and off-chip wireless interconnects implemented for high-performance computing (HPC) systems in the context of micro power wireless design. HPC interconnects demand very high (≥ 10 Gb/s) transmission rates using ultraefficient (~ 1 pJ/bit) transceivers over extremely short (≤ 100 cm) ranges. In an attempt to design such wireless interconnects, first a model for the wireless communication channel properties is developed. The use of CMOS-based energyefficient on-off keying (OOK) transceiver architectures operating in the 60-90 GHz bands is considered as a practical solution. In order to address strict performance requirements of wireless HPC interconnects, and taking advantage of the recent developments in device scaling, compact low-power and innovative circuits based on novel double-gate MOSFETs (DG-MOSFETs) are proposed in the implementation of the architecture. The performance of a compact low-noise amplifier (LNA) design using common source (CS) inductive degeneration with 32 nm DGMOSFETs is investigated by quantitative analysis and simulation. The proposed inductor-less two-stage cascode cascade LNA is optimized for 90 GHz operation and has the advantage of gain switching over its CMOS counterpart without the use of additional switching transistors, which makes it remarkably power efficient and faster. As further examples of efficient and compact DG-MOSFET circuits for OOK transceiver design, a three-stage CS 5 dB tunable power amplifier operating up to 90 GHz, and a novel 90 GHz voltage controlled oscillator are also presented. This is followed by the proposal of an array of four monopole antennas studied using full-wave EM solver.

(Invited) Commercial CMOS-Integrated RF-MEMS

RF-MEMS are an enabling technology for high performance tunable and reconfigurable communications and radar applications. In this paper, we describe the successful integration of RF-MEMS with a 0.18 µm, high voltage RF-CMOS process that is fabricated on 200 mm wafers. The RF-MEMS device is hermetically encapsulated at the wafer level at the conclusion of the process. The RF-MEMS device is a switchable capacitor arrayed to form tunable capacitor arrays that can be used in various applications such as tunable matching networks, tunable filters, tunable power amplifiers, or tunable front ends more generally. The CMOS-integrated, hermetic encapsulated RF-MEMS can be moved through any final back end of line (BEOL) packaging and assembly process to deliver flip-chip or wafer level chip scale packaged devices. The commercial CMOS-integrated RF-MEMS process and product qualification are imminent at the preparation of this paper

Adaptive Electronics with Ferroelectric Capacitors

Tunable ferroelectric capacitors such as barium strontium titanate(BST) operating in the paraelectric region offer a tunability of 50%, within a applied voltage of ± 6V up to 10 GHz. They can be successfully used for a variety of adaptive frequency circuits for communication systems on a variety of substrates. These include tunable filters, tunable multiband power amplifiers and voltage controlled oscillators.

A High-Power and Highly Linear CMOS Switched Capacitor

A new CMOS switched capacitor is developed to be used for high-power applications such as a power amplifier, where high voltage handling capability and low distortion are two major factors. In order to demonstrate superior performance of the proposed structure over a conventional structure, two designs are analyzed and compared while maintaining comparable small signal characteristics such as a 2:1 tuning ratio and a quality factor. The maximum applicable voltage swing of the proposed structure is improved over the conventional structure by a factor of VDD / Vth, or 12 dB in this design. The proposed structure also shows a greatly improved two-tone third-order inter-modulation distortion characteristic with a maximum 34 dB improvement. This proposed structure is a suitable component for tunable CMOS power amplifier applications.

Using MEMS Capacitive Switches in Tunable RF Amplifiers

A MEMS capacitive switch suitable for use in tunable RF amplifiers is described. A MEMS switch is designed, fabricated, and characterized with physical and RF measurements for inclusion in simulations. Using the MEMS switch models, a dual-band low-noise amplifier (LNA) operating at GHz and GHz, and a tunable power amplifier (PA) at GHz are simulated inm CMOS. MEMS switches allow the LNA to operate with 11 dB of isolation between the two bands while maintaining dB of gain and sub- dB noise figure. MEMS switches are used to implement a variable matching network that allows the PA to realize up to 37% PAE improvement at low input powers.