W. Bächtold

The design of varactor-loaded transmission-line phase shifters using lumped elements is discussed in this paper. A monolithic-microwave integrated-circuit (MMIC) phase shifter is fabricated to verify the proposed topology. Only one control voltage is required for phase control. Within a continuously adjustable phase-control range of 360/spl deg/ and a frequency range from 5 to 6 GHz, a low transmission loss of 4 dB/spl plusmn/1.7 dB is measured. The phase shifter is realized with a commercial 0.6-/spl mu/m GaAs MESFET process and requires a chip area of only 0.8 mm/sup 2/. To the knowledge of the authors, the best results reported to date are reached for a continuously adjustable passive phase shifter with comparable circuit size. The presented circuit is well suited to wireless adaptive antenna transceivers, operating in accordance with the 802.11a, high-performance radio local-area-network and high-speed wireless-access-network type-a standard.

The design and results of an ultra-compact single-load reflective-type monolithic-microwave integrated-circuit phase shifter at 6.2 GHz for a satellite radar system is presented in this paper, which has been fabricated using a commercial 0.6-/spl mu/m GaAs MESFET process. A 3-dB 90/spl deg/ coupler with lumped elements enables significant circuit size reduction in comparison to former approaches applying microstrip branch line or Lange couplers. Phase control is enabled using MESFET varactors with capacitance control ratios (C/sub max//C/sub min/) of only four. Equations are derived to precisely describe the phase control ranges versus capacitance control ratios for different load configurations to allow efficient optimizations. Furthermore, the design tradeoff between low loss and high phase control range is discussed. Within a phase control range of 210/spl deg/, a loss of 4.9 dB/spl plusmn/0.9 dB and a 1-dB input compression point of higher than 5 dBm was measured for the designed phase shifter. The circuit size is less than 0.5 mm/sup 2/, which, to our knowledge, is the smallest reflective-type phase-shifter size reported to date.

An ultracompact reflective-type monolithic microwave integrated circuit (MMIC) phase shifter is presented, fabricated using a commercial 0.6-/spl mu/m GaAs MESFET process. The circuit has been developed for low-cost smart antenna receivers, operating in accordance to the IEEE 802.11a and the high-performance radio local area network (HIPERLAN) wireless network standards at C-band. Capacitance control, required for phase control, is performed by usual MESFETs with capacitance control ratios (C/sub max//C/sub min/) of less than four. The impact of the reflective terminations on the maximum phase-control range and the corresponding loss is discussed. This investigation comprises single capacitive terminations, single resonated terminations, and terminations with two resonated loads-in parallel (DRL). With the DRL terminations, phase-control ranges of over 360/spl deg/ have been reached even with such limited capacitance control ranges. A transformation network is proposed for the DRL termination to reduce loss and loss variations. In this configuration, maximum signal losses of 9 and 3 dB, and 1-dB input compression points of higher than 2 and 8 dBm were measured for the phase shifter at 5.2 GHz within phase-control ranges of 360/spl deg/ and 90/spl deg/, respectively. The branch-line coupler of the phase shifter has been realized by using lumped elements, thereby minimizing the circuit size. The total chip area is only 0.9 mm/sup 2/, which to our knowledge is the smallest size for a passive reflective-type phase shifter with 360/spl deg/ phase-control range reported to date.

<i>Context. <i/>Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays.<i>Aims. <i/>We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation.<i>Methods. <i/>W3 IRS5 was observed by HIFI on the <i>Herschel<i/> Space Observatory with deep integration (2500 s) in 8 spectral regions. <i>Results. <i/>The target lines including CH, NH, H<sub>3<sub/>O<sup>+<sup/>, and the new molecules SH<sup>+<sup/>, H<sub>2<sub/>O<sup>+<sup/>, and OH<sup>+<sup/> are detected. The H<sub>2<sub/>O<sup>+<sup/> and OH<sup>+<sup/> <i>J<i/> = 1–0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H<sub>2<sub/>O<sup>+<sup/> and OH<sup>+<sup/> also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds.<i>Conclusions. <i/>The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation.

A design-oriented analysis of microwave transmission-line class-E and class-F amplifiers is presented in this paper. Multiharmonic transmission-line load networks are analyzed and compared in terms of harmonic suppression and their effects on output power and efficiency. Based on this study, a design of highly efficient monolithic-microwave integrated-circuit amplifiers has been carried out. To allow circuit optimization and to simplify the design process, analytic expressions were derived for the most practical multiharmonic transmission-line networks. Fabricated amplifiers achieve state-of-the-art efficiency of 56.2% and 59.0% for class-E and class-F operation at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> -band for power levels of 19.1 and 20.0 dBm, respectively. Moreover, without the need for supplementary filtering sections, harmonic suppression for operation well into compression is better than -25 and -30 dBc for the transmission-line class-F and class-E amplifiers, respectively.