Amplifier Matching Research Articles

Analysis of Doherty Power Amplifier Matching Assisted by Physics-Based Device Modelling

The Doherty Power Amplifier represents one of the most promising solutions for the design of high-efficiency power stages. In the widely adopted ABC scheme, the Doherty Amplifier design critically depends on the accuracy of the device model in different operating conditions, ranging from class AB to class C. For the class C case, library models are often inaccurate, while experimental characterization is difficult since it must be carried out in large signal conditions and with varying gate bias. In this paper, we propose an alternative approach, based on physics-based Technological CAD (TCAD) simulations of the complete Doherty amplifier along with the analysis of its individual MAIN (class AB) and AUXILIARY (class C) stages. TCAD simulations seamlessly provide an accurate modelling of the device behavior in all operation classes, including the device turn-on and the nonlinear capacitances, and easily account for the cross-loading effects of the MAIN and AUXILIARY devices through the output network and the effect of the device feedback (gate-drain) capacitance on the input matching. Analyzing a GaAs Doherty stage at 12 GHz, we show that the input phase of the auxiliary stage can be exploited for the Doherty power amplifier optimization in terms of gain, linearity and efficiency, showing a 9 dB gain with less than 1 dB gain variation from back-off to peak power with a power-added efficiency exceeding 45% over a Doherty region extending to a more than 6 dB output power back-off.

Bifurcation and Entropy Analysis of a Chaotic Spike Oscillator Circuit Based on the S-Switch.

This paper presents a model and experimental study of a chaotic spike oscillator based on a leaky integrate-and-fire (LIF) neuron, which has a switching element with an S-type current-voltage characteristic (S-switch). The oscillator generates spikes of the S-switch in the form of chaotic pulse position modulation driven by the feedback with rate coding instability of LIF neuron. The oscillator model with piecewise function of the S-switch has resistive feedback using a second order filter. The oscillator circuit is built on four operational amplifiers and two field-effect transistors (MOSFETs) that form an S-switch based on a Schmitt trigger, an active RC filter and a matching amplifier. We investigate the bifurcation diagrams of the model and the circuit and calculate the entropy of oscillations. For the analog circuit, the "regular oscillation-chaos" transition is analysed in a series of tests initiated by a step voltage in the matching amplifier. Entropy values are used to estimate the average time for the transition of oscillations to chaos and the degree of signal correlation of the transition mode of different tests. Study results can be applied in various reservoir computing applications, for example, in choosing and configuring the LogNNet network reservoir circuits.

Measuring the Hannay geometric phase

The Hannay geometric phase is the classical analog of the well-known Berry phase. Its most familiar example is the effect of the latitude λ on the motion of a Foucault pendulum. We describe an electronic network whose behavior is exactly equivalent to that of the pendulum. The circuit can be constructed from off-the-shelf components using two matched transconductance amplifiers that comprise a gyrator to introduce the non-reciprocal behavior needed to mimic the pendulum. One may precisely measure the dependence of the Hannay phase on λ by circuit simulation and by laboratory measurements on a constructed circuit.

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%.

Cascaded Nonlinear-Optical Loop Mirror-Based All-Optical PAM Regenerator

An all-optical regeneration scheme based on cascaded nonlinear-optical loop mirrors (NOLMs) for pulse amplitude modulation (PAM) signals is proposed. The optimal working point (WP) of every NOLM can be set by means of the normalized power transfer function (NPTF) and normalized differential gain (NDG). As examples, the PAM-4 and PAM-8 regenerations based on cascaded two-NOLMs are demonstrated by optimizing the splitting ratios of the optical couplers and the gain coefficient of the inter-stage matching amplifier, achieving the Q-factor improvements of 25.32dB and 21.18dB, respectively. Compared to the conventional regenerator scheme, a 1.69dB signal-to-noise ratio (SNR) gain is achieved due to the flat power response within the regenerative range.

Real-Time Amplifier Load-Impedance Optimization for Adaptive Radar Transmitters Using a Nonlinear Tunable Varactor Matching Network

Future radar transmitters will need to be able to quickly reconfigure their radio-frequency circuitry to change operating frequency and spectral output while maintaining high power-added efficiency (PAE). In this paper, fast tuning of a tunable-varactor matching network is demonstrated to optimize the PAE while meeting requirements on the adjacent-channel power ratio. The tunable varactor network, a first-level prototype of a tunable radar amplifier matching network, incurs nonlinear performance, providing possible challenges to measurement accuracy. To address the issue of nonlinearities while maintaining ability to quickly reconfigure, the tunable-varactor network is characterized at different input power levels to allow useful performance in its nonlinear regime. The power-dependent characterization is used in an algorithm for optimization of an amplifier's PAE, by looking up the matching network characterization performed at the power estimated to be output by the amplifier. Measurement results show that this characterization enhances the consistency of the optimized PAE. Using the tunable varactor network reduces the optimization time to one-fourth of the time required when using the algorithm with a traditional mechanical load-pull tuner.

Piezoceramic Gauges for Measuring Rapidly Changing and Oscillatory Pressures

Designs of piezoelectric pressure gauges based on PZT-19 ceramics and equipment for testing and calibration of piezoelectric gauges are described. Tests of the developed piezoelectric transducers in a shock tube showed that their characteristics are stable in time, the sensitivity ranges from 5 to 50 mV/bar, the operating pressure range is up to 100 bar, and the frequency range with a high-resistivity matching amplifier is 10–5 × 105 Hz. The level of errors in measurements of pulse and oscillatory pressures is estimated as 5%.

A High-Performance 650-GHz Sideband-Separating Mixer—Design and Results

We presented the design and experimental results of a new sideband-separating (2SB) mixer for 600-720 GHz (ALMA Band 9). Although designed following the classical quadrature hybrid architecture, the emphasis of the optimization was this time not placed on ultimate phase and amplitude balance in the hybrid, but on the reduction and active suppression of reflections and standing waves. It turns out that, once the phase and the amplitude are sufficiently balanced, the image rejection ratio (IRR) starts being dominated by unbalanced parasitic reflections in the signal path, and further perfection of the hybrid's balance is not the way toward higher IRR. Four operational waveguide blocks were produced. IRRs above 15 dB over the entire band were obtained, depending critically on mixer matching. The noise temperature was not more than 20-30 K above the value expected from the individual mixer devices. With the RF circuits optimized thus, the performance becomes limited by the IF system, where similar interference and standing wave problems seem to occur. These are exacerbated when, for compactness (i.e., in arrays), cryogenic isolators between the mixers and amplifiers are omitted. We show that, because of the high performance of the mixers, an IRR of 10 dB can still be obtained without isolators. When, on the other hand, highly matched amplifiers are used, we expect that the full image rejection performance can be achieved even in array receivers. These 2SB mixers are intended for the future 2SB receivers on the APEX (Chile) and LLAMA (Argentina) observatories and for deployment in any other observatory that would benefit from sideband separation in the 600-720-GHz band.

Noise Cancelation? Explained!: The Role of Feedback in Noise-Canceling LNAs and Receivers

Inductorless wide-band low-noise amplifiers (LNAs) usually suffer from poor noise performance, mainly due to the high noise contribution of the matching device. Noise canceling (NC) is a technique used in wide-band LNAs [1]-[13] to nullify the noise contribution of the matching device at the output. NC techniques are often explained with the help of the block diagram shown in Figure 1(a), where the input signal from a source of internal impedance Rs is simultaneously fed to a matching amplifier and a voltage sensing amplifier.

6-18 GHz Reactive Matched GaN MMIC Power Amplifiers with Distributed L-C Load Matching

A commercial 0.25 μm GaN process is used to implement 6–18 GHz wideband power amplifier (PA) monolithic microwave integrated circuits (MMICs). GaN HEMTs are advantageous for enhancing RF power due to high breakdown voltages. However, the large-signal models provided by the foundry service cannot guarantee model accuracy up to frequencies close to their maximum oscillation frequency (Fmax). Generally, the optimum output load point of a PA varies severely according to frequency, which creates difficulties in generating watt-level output power through the octave bandwidth. This study overcomes these issues by the development of in-house large-signal models that include a thermal model and by applying distributed L-C output load matching to reactive matched amplifiers. The proposed GaN PAs have successfully accomplished output power over 5 W through the octave bandwidth.

Development of a low-noise amplifier for neutron detection in harsh environment

A fast matching charge amplifier for neutron spectroscopy in harsh environment has been developed and tested at the JET Tokamak. This front-end circuit is capable to operate at a distance up to 100 meters from a sensor without increasing its equivalent noise charge. Further improvements are possible by exploiting the intrinsic performance of silicon-germanium bipolar junction transistors.

Simulation of RF MEMS based matching networks and a single pole double throw switch for Multiband T/R Modules

Abstract. This work presents concepts and designs for two essential components of a frequency agile transmit and receive module based on Radio Frequency Micro Electro Mechanical System (RF MEMS) switches for the frequency range from 3.5 GHz up to 8.5 GHz. The advantages of a variable power amplifier (PA) matching compared to a fixed broadband solution are examined and discussed in context with the designed components. To demonstrate the principle functionality, an assembly concept is presented, which allows for the integration of a frequency agile 6 W power amplifier with surrounding components like phase shifters, switches and antennas. An RF MEMS switching element is introduced as a high isolation polarization switch, featuring low insertion loss as well as almost no DC power consumption.

Extensive 6.0-18.0 GHz Frequency Low Noise Amplifiers Integrated to Form LC-Feedback Oscillators

Low Voltage supplied radio-frequency (RF) CMOS devices by TSMC 0.18 micron process are used for the RF circuit designs of low noise amplifiers. Three components, low noise amplifiers (LNA), Class-E power amplifiers (PA), and LC oscillator simultaneously working at 6.0 to 18.0 GHz, are explored. The scenario combining two matched amplifiers, LNA and PA, and then amplifying the coupled signals from the oscillators is proven to be working. LNA usually runs prior to PA to suppress the noises, and thus the whole set functions like an integrated LNA, whose forward gain may be promoted as high as at least over 40 dB just as expected. At 6.0, 12.0 and 18.0 GHz, magnitudes of both S11 and S22 in the Smith Chart are deliberately tuned to approach to zero as shown. And Noise Figure determined to be 1.175 gives promising integrated circuit.

A 90-GHz InP-HEMT lossy match amplifier with a 20-dB gain using a broadband matching technique

We demonstrated a 90-GHz InP-HEMT lossy match amplifier (LMA) with a 20-dB gain for the first time. We obtained this performance with the power consumption of 220 mW, which is the smallest one ever reported for an over 80-GHz broadband amplifier. The amplifier acts as a C-R coupled amplifier in the low to medium frequency range and as an L-C match amplifier at the high frequencies. Therefore, this configuration provides both high gain and wide bandwidth. The key to achieve a 90-GHz bandwidth is broadband matching in the L-C match amplifier. In this paper, we propose a broadband matching technique with a low Q network and describe the design guideline for the excellent performance.

Radiation from a microstrip amplifier

A full-wave method is presented to investigate radiation from a microstrip amplifier. The spectral-domain dyadic Green's function, which takes into account both radiation and surface waves, is used to formulate an integral equation. The method of moments is then employed to find the current densities in microstrips and, subsequently, the scattering parameters of the amplifier. The radiated space and surface waves that are launched from the amplifier can be further expressed in terms of the dyadic Green's function and current densities. To verify the numerical results of scattering parameters and far-field radiation patterns, a UHF-band microstrip amplifier matching with single stubs has been implemented and measured. The comparison between simulation and measurement shows excellent agreement.

Determining the RF resistance and Q‐factor of air‐core inductors

AbstractAir‐core inductors are large‐body, low‐loss components that find frequent use in circuits such as RF power amplifier matching networks. The physical attributes of the inductors make loss characterization using standard commercial instruments (e.g., impedance analyzers or resonant coaxial lines) problematic. In this paper, a resistance and quality factor extraction technique based on low‐impedance microstrip test fixtures is demonstrated at frequencies near 800 MHz. It is shown that an inductor resistance on the order of 0.1–1 Ω can be accurately determined. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 89–93, 2001.

Construction and Commissioning of a 100 KW RF Amplifier System for Hanbit Central Cell Plasma Heating

To complete basic configuration for the RF heating scenario in Central Cell of the Hanbit mirror device, a RF amplifier system with a power of 100 kW and frequency range of 1.4 – 4.0 MHz, and a high power RF matching network have been developed in KBSI. The output pulse width of the amplifier ranges from 10 msec to 100 msec and the duty cycle is 100 msec/300 sec. The developed amplifier will be used for plasma production and heating by utilizing the slot antenna and the double-half-turn antenna, respectively.In this paper, we present the engineering design of the amplifier system and matching network, and experimental results such as power test of amplifier on dummy load, impedance matching test on the double-half-turn antenna in vacuum condition. Also, the first RF launching experiment result with the double-half-turn antenna on the target plasma which is produced by the slot antenna is presented.

High combining-efficiency X-band spatial power-combined array using a multilayered packaging architecture

The design of a high combining-efficiency spatial power-combined array is described in this paper. A multilayered stacked stripline architecture enables a compact stable design. An array incorporating antenna active impedance and proper amplifier matching is measured with a combining efficiency of 87%, radiating 6.8 W of an available 7.8 W into the ideal uniformly illuminated array directivity at 10.1 GHz.

Method and apparatus for determination of the total directional emissivity of opaque materials in the temperature range 300 to 600 K

A novel device for measurements of the normal and directional total emissivity of solid surfaces in the range 300–600 K is described. The measurements were performed using the radiation comparison method. A novel black-body radiation source is used as a standard. The detection system consists of a pyroelectric head, a preamplifier, a chopper, and a matching lock-in amplifier with analog recorder ourput. The device is simple and well suited for routine measurements. Comparison of our results with those of previous investigations shows a good agreement.

High Gain Equalizing Amplifier Integrated Circuits for a Gigabit Optical Repeater

Equalizing amplifier circuits for a gigabit optical-fiber transmission system are integrated on two monolithic chips implementing an advanced silicon bipolar process. Several new circuit techniques such as a broad-band 50-/spl Omega/ matching amplifier and an electrically controlled and adjusted peaking technique are employed. It is clarified that the main degradation factors of circuit stability are parasitic capacitance between the input and output terminals, and the crosstalk occuring through the wire bonding inductance. The maximum gain and 3-dB down bandwidth of the equalizing amplifier IC's are 64 dB and 1.2 GHz, respectively. The noise figure obtained is 4.5 dB within the dc to 2-GHz range.