Gottfried Magerl

High-efficiency harmonic-control amplifier

A half-sinusoidally driven class-A harmonic-control amplifier (hHCA) combines the advantage of high gain of class A with the advantage of high drain efficiency of class F. Consequently, power-added efficiency is increased as compared with state-of-the-art high-efficiency amplification techniques. As this innovative amplifier concept consists of a pulse-forming class-B amplifier stage followed by a class-A power-amplifier stage, intermodulation distortion is low even in saturation. The realization of such a two-stage hHCA offers 71% overall efficiency, 27.9 dBm output power, and 22.4 dB gain at 1.62 GHz. Two-tone measurements at 1 dB gain compression, where the amplifiers single-carrier (SC) overall efficiency is still 64%, has demonstrated thirdand fifth-order intermodulation distortion of -29 and -21 dBc, respectively.

Rectangularly driven class-A harmonic-control amplifier

A rectangularly driven class-A harmonic-control amplifier (rHCA) is studied, which combines the advantage of high device drain efficiency (/spl eta//sub D/) of a switched-type amplifier with the advantage of high gain (G) of class-A operation, thus maximizing its power-added efficiency (PAE). In this rHCA, harmonics are controlled such that drain-to-source voltage becomes half-sinusoidal. This reduces the necessary supply voltage without degrading output power. In comparison with a class-F amplifier using the same transistor, the realization of such an rHCA has demonstrated 0.4-dB larger output power, 3.8-dB increased gain, 4% higher PAE, and 22% lower drain supply voltage at 1.62 GHz.

A New Quadrature PWM Modulator With Tunable Center Frequency for Digital RF Transmitters

State-of-the-art quadrature-type modulators for all-digital radio-frequency (RF) transmitters operate optimally at an RF center frequency (fc) that is a fraction of the modulator switching rate. This is a major limitation if the modulators of this type are to be used in multichannel transmitter systems. In this brief, a novel quadrature modulator based on pulsewidth modulation with controllable in-band distortion is presented, which permits continuous adjustment of fc in digital domain. In addition, distortion generation related to digital upconversion of pulsed baseband signals is studied, and suitable compensation methods are given. The performance of the proposed modulator is compared with those of previously published encoding methods in terms of reconstructed RF signal quality and computational complexity. The evaluation results suggest that significant improvements in signal band distortion can be expected with a computational load suitable for real-time reconfigurable hardware realizations.

High efficiency harmonic control amplifier

A new high efficiency amplifier concept which ideally delivers 100% drain efficiency and class A gain is described. The power amplifier realized with a commercially available GaAs FET has demonstrated 74% power-added efficiency, 27.9 dBm output power, and 14.4 dB gain at 1.62 GHz.

Radiation-trapping in cylindrical and spherical geometries

Abstract We solve the Holstein radiation-trapping equation numerically for cylindrically and spherically symmetric geometries. For Doppler and Lorentz lineshapes, we give analytical fitting equations for the trapping factors and for the shapes of the 10 lowest-order modes. For Voigt profiles, we modify the classical Walsh-interpolation formula so that it is now applicable at all opacities and for all modes. The results are checked by Monte Carlo simulation and by comparison with existing approximations. Our fits and interpolations yield 2–20% accuracy.

Infrared microwave sideband laser spectroscopy of the ν3 and 2ν3 ← ν3 bands of 13CH3F☆

Abstract A large number of transitions in the ν 3 and 2 ν 3 ← ν 3 bands of 13 CH 3 F have been recorded at Doppler-limited resolution by means of an infrared laser microwave sideband spectrometer. The sidebands were generated in a CdTe crystal that was simultaneously irradiated by a CO 2 infrared laser and a high-power microwave source operating in the 8- to 18-GHz region. The J and K structures of the bands were well resolved except for the lowest K values. Frequencies of transitions involving J values up to 47 and K values up to 16 are reported. Vibration-rotation parameters for the v 3 = 0, 1, and 2 states were obtained by fitting to the experimental frequencies. These parameters reproduce the experimental values with an rms deviation of 3.8 MHz for the fundamental band and 2.5 MHz for the hot band.

Radiation-trapping in a plane-parallel slab

Abstract We treat the trapping of resonance radiation in a plane-parallel slab geometry, emphasizing the importance of higher-order spatial modes of excited atoms. The whole range of opacities and all commonly encountered line shapes (single or hyperfine-split spectral lines of Lorentzian, Doppler, or Voigt profiles) are covered. For the basic line shapes (Doppler and Lorentz), we solve the Holstein-Biberman equation numerically and give simple analytic fitting formulas for the shape and the trapping factor of the ground mode and higher-order modes. The results are checked and extended to more general line shapes with a quite different approach, a Monte-Carlo simulation. For the treatment of Voigt profiles, we modify common interpolation formulas for the trapping factor to make them applicable at all opacities. We critically review the Milne-Samson theory that is often used in the low-opacity regime for arbitrarily complicated lineshapes; a new definition of the equivalent opacity considerably increases its range of applicability. Almost all practically occurring radiation-trapping problems in a plane-parallel slab geometry can be treated with the present approach.

Ridged Waveguides with Inhomogeneous Dielectric-Slab Loading

The dispersion equation of the ridged waveguide with inhomogeneous dielectric-slab Ioading is derived. Numerical results for the cutoff frequencies of the three lowest order TE/sub m0/ modes are given which substantiate the feasibility of the modal expansion and field-matching technique employed. For a Teflon-slab loaded ridged waveguide, a 40-percent decrease of dominant-mode cutoff frequency, simultaneously providing 20-percent enhanced TE/sub 20/-mode separation compared to an empty ridged waveguide, is demonstrated.

Broadband electronically tunable resonant microwave modulators for CO2 lasers

An electro‐optic microwave modulator generating frequency‐swept sidebands 26–31 GHz offset from a CO2 laser carrier is described. Resonant enhancement of the modulating field allows as low as 8‐mW microwave drive power. Electronic tuning of the resonances by a ferrite phase shifter inside the cavity increases the FWHM modulation bandwidth from 140 MHz (untuned) to 4 GHz.

Direct frequency reading laser spectroscopy: ν3 Fundamental and Stark effect of CH3F

Abstract The frequencies of 63 transitions in the ν 3 fundamental have been measured with a tunable sideband laser. The following excited-state constants have been derived: ν 0 = 1048.61000 (44) cm −1 , ( A ′ − A ″) = −293.77 (90) MHz; B = 25 197.570 (20) MHz, D J = 56.61 (22) kHz, D JK = 521.6 (56) kHz, D ′ K − K ″ K = −97.7 (70) kHz. Resolution is limited by the laser stability, i.e., ⋍1 MHz. The accuracy in absolute frequency is generally 13 MHz ( Δ ν ν = 4 × 10 −7 ) while the relative error in measurement is believed to be ≤5 MHz. On the Q (6,6) and Q (6,4) transitions the Stark effect was observed at moderate field strengths. Stark as well as source modulation has been applied.