Comprehensive numerical modelling of the performance of a second harmonic generation stage coupled with a low-gain optical parametric amplifier

We present a comprehensive model for predicting the full performance of a second harmonic generation-optical parametric amplification system that aims at enhancing the temporal contrast of laser pulses. The model simultaneously takes into account all the main parameters at play in the system such as the group velocity mismatch, the beam divergence, the spectral content, the pump depletion, and the length of the nonlinear crystals. We monitor the influence of the initial parameters of the input pulse and the interdependence of the two related non-linear processes on the performance of the system and show its optimum configuration. The influence of the initial beam divergence on the spectral and the temporal characteristics of the generated pulse is discussed. In addition, we show that using a crystal slightly longer than the optimum length and introducing small delay between the seed and the pump ensures maximum efficiency and compensates for the spectral shift in the optical parametric amplification stage in case of chirped input pulse. As an example, calculations for bandwidth transform limited and chirped pulses of sub-picosecond duration in beta barium borate crystal are presented.

Parametric optimisation of manufacturing tolerances at the aircraft surface

Up until now, aircraft surface smoothness requirements have been aerodynamically driven with tighter manufacturing tolerance to minimize drag, that is, the tighter the tolerance, the higher is the assembly cost in the process of manufacture. In the current status of commercial transport aircraft operation, it can be seen that the unit cost contributes to the aircraft direct operating cost considerably more than the contribution made by the cost of block fuel consumed for the mission profile. The need for a customer-driven design strategy to reduce direct operating cost by reducing aircraft cost through manufacturing tolerance relaxation at the wetted surface without unduly penalizing parasite drag is investigated. To investigate this, a preliminary study has been conducted at 11 key manufacturing features on the surface assembly of an isolated nacelle. In spite of differences in parts design and manufacture, the investigated areas associated with the assembly of nacelles are typical of generic patterns in the assembly of other components of aircraft. The study is to be followed up by similar studies extended to lifting surfaces and fuselage

Parametric study of nonlinear electrostatic waves in two-dimensional quantum dusty plasmas

The nonlinear properties of two-dimensional cylindrical quantum dust-ion-acoustic (QDIA) and quantum dust-acoustic (QDA) waves are studied in a collisionless, unmagnetized and dense (quantum) dusty plasma. For this purpose, the reductive perturbation technique is employed to the quantum hydrodynamical equations and the Poisson equation, obtaining the cylindrical Kadomtsev–Petviashvili (CKP) equations. The effects of quantum diffraction, as well as quantum statistical and geometric effects on the profiles of QDIA and QDA solitary waves are examined. It is found that the amplitudes and widths of the nonplanar QDIA and QDA waves are significantly affected by the quantum electron tunneling effect. The addition of a dust component to a quantum plasma is seen to affect the propagation characteristics of localized QDIA excitations. In the case of low-frequency QDA waves, this effect is even stronger, since the actual form of the potential solitary waves, in fact, depends on the dust charge polarity (positive/negative) itself (allowing for positive/negative potential forms, respectively). The relevance of the present investigation to metallic nanostructures is highlighted.

Idealised operation of zero-voltage-switching series-L/parallel-tuned Class-E power amplifier

An analysis of a modified series-L/parallel-tuned Class-E power amplifier is presented, which includes the effects that a shunt capacitance placed across the switching device will have on Class-E behaviour. In the original series L/parallel-tuned topology in which the output transistor capacitance is not inherently included in the circuit, zero-current switching (ZCS) and zero-current derivative switching (ZCDS) conditions should be applied to obtain optimum Class-E operation. On the other hand, when the output transistor capacitance is incorporated in the circuit, i.e. in the modified series-L/parallel-tuned topology, the ZCS and ZCDS would not give optimum operation and therefore zero-voltage-switching (ZVS) and zero-voltage-derivative switching (ZVDS) conditions should be applied instead. In the modified series-L/parallel-tuned Class-E configuration, the output-device inductance and the output-device output capacitance, both of which can significantly affect the amplifier's performance at microwave frequencies, furnish part, if not all, of the series inductance L and the shunt capacitance COUT, respectively. Further, when compared with the classic shunt-C/series-tuned topology, the proposed Class-E configuration offers some advantages in terms of 44% higher maximum operating frequency (fMAX) and 4% higher power-output capability (PMAX). As in the classic topology, the fMAX of the proposed amplifier circuit is reached when the output-device output capacitance furnishes all of the capacitance COUT, for a given combination of frequency, output power and DC supply voltage. It is also shown that numerical simulations agree well with theoretical predictions.

Inverse Class E amplifier and oscillator phase noise characteristics

This paper gives the first experimental characterisation of the phase noise response of the recently introduced Inverse Class E topology when operated as an amplifier and then as an oscillator. The results indicate that in amplifier and oscillator modes of operation conversion efficiencies of 64%, and 42% respectively are available, and that the excess PM noise added as a consequence of saturated Class E operation results in about a 10 dB increase in PM over that expected from a small-signal Class A amplifier operating at much lower efficiency. Inverse Class E phase transfer dependence on device drain bias and flicker noise are presented in order to show, respectively, that the Inverse Class E amplifier and oscillator follow the trends predicted by conventional phase noise theory. © 2007 EuMA.

Balanced class e amplifier based multimode modulator

In this paper we present an adaptation to the classical I/Q modulator topology which simultaneously allows it to operate both as a multi-modulation standard modulator, and as a high efficiency balanced amplifier. This is made possible by concurrently exploiting the ability of the Class E amplifiers to produce variable output power at maximum power added efficiency, PAE, by simple dc bias control while faithfully reproducing phase encoded signals. Experimental evidence for the behaviour of the modulator when operated in QPSK mode at 2.33 GHz with a 1 Msymbol/s rate shows that Error Vector Magnitude of less than 5% with amplifier PAE of 65% is possible. The multimode modulator presented here should lead to significantly reduced complexity, enhanced functionality transceivers for use in dc power sensitive handheld wireless applications. © 2007 EuMA.

Design strategies for dual-band class-e power amplifier using composite right/left-handed transmission lines

In this article we propose a technique for dual-band Class-E power amplifier design using composite right/left-handed transmission lines, CRLH TLs. Design equations are presented and design procedures are elaborated. Because of the nonlinear phase dispersion characteristic of CRLH TLs, the single previous attempt at applying this method to dual bond Class-E amplifier design was not sufficient to simultaneously satisfy, the minimum requirement of Class-E impedances at both the fundamental and the second harmonic frequencies. This article rectifies this situation. A design example illustrating the synthesis procedure for a 0.5W-5V dual band Class-E amplifier circuit simultaneously operated at 900 MHz and 2.4 GHz is given and compared with ADS simulation.

Inverse Class-E Amplifier With Transmission-Line Harmonic Suppression

This paper reports on the design methodology and experimental characterization of the inverse Class-E power amplifier. A demonstration amplifier with excellent second and third harmonic-suppression levels has been designed, constructed, and measured. The circuit fabricated using a 1.2-min gate-width GaAs MESFET is shown to be able to deliver 22-dBm output power at 2.3 GHz. The amplifier achieves a peak power-added efficiency of 64 % and drain efficiency of 69 %, and exhibits 11.6 dB power gain when operated from a 3-V supply voltage. Comparisons of simulated and measured results are given with good agreement between them being obtained. Experimental results are presented for the amplifier's response to Gaussian minimum shift keying modulation, where a peak error vector modulation value of 0.6% is measured.

2.4 GHz Class-E power amplifier with transmissionline harmonic terminations

The design procedure, fabrication and measurement of a Class-E power amplifier with excellent second- and third-harmonic suppression levels are presented. A simplified design technique offering compact physical layout is proposed. With a 1.2 mm gate-width GaAs MESFET as a switching device, the amplifier is capable of delivering 19.2 dBm output power at 2.41 GHz, achieves peak PAE of 60% and drain efficiency of 69%, and exhibits 9 dB power gain when operated from a 3 V DC supply voltage. When compared to the classical Class-E two-harmonic termination amplifier, the Class-E amplifier employing three-harmonic terminations has more than 10% higher drain efficiency and 23 dB better third-harmonic suppression level. Experimental results are presented and good agreement with simulation is obtained. Further, to verify the practical implementation in communication systems, the Bluetooth-standard GFSK modulated signal is applied to both two- and three-harmonic amplifiers. The measured RMS FSK deviation error and RMS magnitude error were, for the three-harmonic case, 1.01 kHz and 0.122%, respectively, and, for the two-harmonic case, 1.09 kHz and 0.133%. © 2007 The Institution of Engineering and Technology.