Luc Lapierre

Joint optimization of the power-added efficiency and the error-vector measurement of 20-GHz pHEMT amplifier through a new dynamic bias-control method

This paper presents a method for the optimization of the power-added efficiency (PAE), as well as the error-vector measurement (EVM) of a 20-GHz power amplifier (PA) applied in this case to the M quadrature and amplitude modulations. A first key point lies in that both input and output biasing voltages of the solid-state power amplifiers (SSPAs) are dynamically controlled according to the RF power level associated with the symbol to be transmitted. The leading idea is that the dynamic biasing control is designed and implemented to keep fixed amplitude (AM/AM) and phase (AM/PM) conversion values, while the RF input power level changes. The power gain of the PAs can then be dynamically tuned to a fixed power gain corresponding to the compression gain behavior for which the PAE is optimum at low-, medium-, and high-input RF power levels. As a main consequence, PAE performances can be drastically improved as compared to classical backoff solutions and optimized while keeping a very good EVM. A Ka-band hybrid amplifier has been realized using an 8/spl times/75 /spl mu/m power pseudomorphic high electron-mobility transistor. The proposed linearization technique is validated by comparisons between measured PAE and EVM on the SSPA when a fixed and controlled bias are used.

A DC to 100 GHz high performance ohmic shunt switch

This paper presents a wideband ohmic shunt switch implemented on a coplanar waveguide (CPW). The switch is fabricated using a dielectric membrane with patterned metallic contacts that short the CPW line when it is electrostatically actuated. The switch has been extrapolated from measurements. It exhibits low insertion loss, good matching, high isolation from DC to W band (>20 dB up to 100 GHz) and very good mechanical properties with switching time <1/spl mu/s.

Analysis and elimination of parametric oscillations in monolithic power amplifiers

This work describes an analysis and design methodology for eliminating parametric oscillations in microwave power amplifiers. Large-signal stability analyses based on system pole-zero identification techniques are proposed to guide the design process towards a stable circuit. In order to demonstrate the proposed approach, parametric oscillations of a Ku-band MMIC power amplifier have been eliminated, while maintaining the original performances of the circuit.

Two-Stage GaN HEMT Amplifier With Gate–Source Voltage Shaping for Efficiency Versus Bandwidth Enhancements

In this paper a two-stage 2-GHz GaN HEMT amplifier with 15-W output power, 28-dB power gain, and 70% power-added efficiency (PAE) is presented. The power stage is designed to operate under class F conditions. The driver stage operates under class F-1 conditions and feeds the power stage with both fundamental and second harmonic components. The inter stage matching is designed to target a quasi-half sine voltage shape at the intrinsic gate port of the power stage. The goal is to reduce aperture angle of the power stage and get PAE improvements over a wide frequency bandwidth. In addition to the amplifier design description, this paper reports original time-domain waveform measurements at internal nodes of the designed two-stage power amplifier using calibrated high-impedance probes and large signal network analyzer. Furthermore, waveform measurements recorded at different frequencies show that aperture angle remains reduced over large frequency bandwidth. In this study, a PAE greater than 60% is reached over 20% frequency bandwidth.

Coupled Pade approximation-finite element method applied to microwave device design

In this paper, a fast and rigorous analysis method is presented, combining the Pade approximation and a finite element method. The method is applied to the design of two microwave devices: a narrow band bandpass filter and a broadband microwave module. The accuracy of this approach is demonstrated by the good agreement between the coupled Pade approximation-finite element analyses and the standard finite element ones, and also between the coupled Pade approximation-FE analysis and the experimental filter response.

A new satellite repeater amplifier characterization system for large bandwidth NPR and modulated signals measurements

Power consumption and dissipation of satellite payloads for space telecommunication systems are mainly due to power amplifiers. To increase system capacity with limited bandwidth, multicarrier operations are required. Linearity is specified to limit the signal distortion by the nonlinear power amplifiers. In order to minimize power consumption under those linearity requirements, accurate measurements have to be performed. The NPR is well known as the figure of merit for the intermodulation distortion performance of amplifiers in telecommunications. In this paper, the development of an accurate large bandwidth NPR measurement system is presented. It enables characterizations up to Ka band (17-21 GHz and 27-31 GHz for space telecommunications applications with typically 250 MHz bandwidth). Measurements made on power amplifiers have been used to optimize operating conditions.

Compact quasi planar silicon bandpass filters based on metallic periodic structure for Q and V band applications

Small size filters are presented here, they are based on a periodic lattice of metallic holes that form coupled silicon resonators. The first structure is a filter at 45 GHz with 8% bandwidth at -3 db, realized on 430 /spl mu/m thick high resistivity silicon wafer using a wet etching process. I/O CPW feeds are printed on the top of the substrate. The second structure is a filter at 58.5 GHz with 2% bandwidth at -3 db. The via holes lattice is realized with deep RIE process and the filter is bonded to a PCB with a flip chip technique. Based on the same principle, a CPW to waveguide transition is finally presented.

A novel behavorial model of power amplifier based on a dynamic envelope gain approach for the system level simulation and design

This paper presents a novel and non quasi static behavioral ( black box) model of power amplifiers. It takes into account nonlinear memory effects for an accurate prediction of signal distortions and power budget in communication systems. The model topology and the model extraction procedure are described. The model proposed in this paper can be derived either from envelope simulation results of a PA circuit design or from time domain envelope measurements of a PA driven by modulated stimuli. Examples of new measurements (i.e. : dynamic AM/AM conversion characteristics) highlight nonlinear memory of SSPAs. The behavioral model proposed is very well suited for an efficient implementation in system level software packages because it consists of an extension of the complex envelope gain function. The proposed complex gain which depends on the input envelope and its first time derivatives provides a great enhancement as compared to the memoryless static complex gain derived from classical AM/AM and AM/PM conversion characteristics.

Packaged Millimeter Wave Thermal MEMS Switches

This abstract describes MEMS thermally actuated millimeter wave switches. The switches are constructed using a stress controlled dielectric membrane, with patterned metallic contacts. The resulting switches can be operated at low voltage, without sacrificing the spring constant. The structure allows to build resistive switches up to millimeter wave. Full wave simulations were performed using FEM and MoM codes, and agree well with measurements. A wafer scale packaging technique has been developed to protect the components during the dicing stage, and for long term durability. The measured isolation are better than 35 dB between 30 and 40 GHz.

High-Current–High-Speed Dynamic Bias Control System Applied to a 100-W Wideband Push–Pull Amplifier

This paper presents a dynamic bias control system applied to a high power wideband amplifier. The amplifier used is based on a push-pull topology with LDMOS transistors and works in the 50-500 MHz frequency bandwidth. It delivers a nominal 100 W output power with 60% power-added efficiency (PAE) when it is fed with continuous signals. When it is driven by a 16QAM modulated signal, 6 dB input power back-off is necessary to keep an error vector measurement below 5%. This usual back-off technique results in lower PAE (43% in our case). By implementing the proposed bias control system, both 55% PAE and 5% EVM have been reached for 75 W average output power. The drain bias control circuit handles high currents and high voltages (7 A-28 V). The proposed implementation makes use of a class S modulator driven by a SigmaDelta modulator. Up to 1 Mbit/s envelope bit rate can be efficiently and accurately processed by using here dedicated circuits running at 20 MHz clock frequency.