Dual-band impedance transformation networks for integrated power amplifiers

This paper shows that the two most common impedance transformation networks for power amplifiers (PAs) can be designed to achieve optimum transformation at two frequencies. Hence, a larger bandwidth for the required impedance transformation ratio is achieved. A design procedure is proposed, which takes imperfections like losses into account. Furthermore, an analysis method is presented to estimate the maximum uncompressed output power of a PA with respect to frequency. Based on these results, a fully integrated PA with a dual-band impedance transformation network is designed and its functionality is proven by large signal measurement results. The amplifier covers the frequency band from 450 MHz to 1.2 GHz (3 dB bandwidth of the output power and efficiency), corresponding to a relative bandwidth of more than 100%. It delivers 23.7 dBm output power in the 1 dB compression point, having a power-added efficiency of 33%

Analysis and design of an efficient, fully integrated 1-8GHz traveling wave power amplifier in 180nm CMOS

Traveling wave amplifiers (TWAs) offer the advantage of broadband amplification and a closed set of equations that allow deriving the RF gain by means of treating TWAs as discrete transmission line approximations. Up to now, however, the significant losses associated with CMOS integrated inductors have been neglected. This work presents a new approach for determining the transmission line losses and phase constants that will bring about an enhanced gain prediction accuracy. The theory is verified by means of a realized design example. The working principle of the integrated DC supply inductor is discussed, whose performance is based on the inductors self-resonance effect. When applying a supply voltage Vdd of 2.4V, the measured compression point P1dB and the power added efficiency PAE at 2.4GHz amount to 16.9dBm and 19.6%, respectively. At 5.5GHz, a value of 16.6dBm for P1dB and an associated PAE of 13.9% are achieved. The peak RF gain for these output power values reaches 11dB, and values greater than 8dB are obtained up to 7GH

A 30 Gb/s High-Swing, Open-Collector Modulator Driver in 250 nm SiGe BiCMOS

This paper presents a modulator driver realized as a breakdown voltage doubler which can provide a high output swing of 7.6 Vpp,diff for load impedances as low as 30 Ω, thus overcoming the limitation imposed by the collector-emitter breakdown voltage. The open-collector design gives an important degree of freedom regarding the modulator load to be driven, while significantly reducing the circuit's power consumption. The driver is capable of running at 30 Gb/s while dissipating 1 W of DC power. Thanks to the inductorless design, the active area occupied by the circuit is only 0.28 mm × 0.23 mm. The driver was realized in a 250 nm SiGe BiCMOS technology

Theoretical Considerations Regarding the Application of Received Signal Strength within Heterogeneous Indoor Positioning Systems

Nowadays, there are a variety of different indoor positioning systems, where some of them use communication hardware taking advantage of the Received Signal Strength (RSS) such as Wireless Local Area Networks (WLAN) or Bluetooth. These variants are employed if low cost is of primary importance. However, the accuracy provided is in the meter range. The alternative are positioning-tailored approaches like Frequency Modulated Continuous Wave (FMCW) radar, Ultra-WideBand (UWB) radar or phase-based positioning, which offer superior accuracy in the low decimetre range. If there is such a system in use, the question arises whether there is any improvement, if utilizing additional RSS measurements, which are performed by most systems anyway. With the help of the Cram´er-Rao Lower Bound (CRLB), this paper demonstrates that these additional readings can improve accuracy significantly, thus widen the application field for RSS from a low-budget only technique to enabling enhanced accurate positioning. To demonstrate this statement we compare the CRLB for Time of Arrival (ToA) with hybrid ToA/RSS. Our evaluations show that in practice the CRLB is approximately divided by two, if incorporating the RSS for each base station

Design of bendable high-frequency circuits based on short-channel InGaZnO TFTs

A unique requirement of flexible electronic systems is the need to simultaneously optimize their electrical and mechanical performance. Amorphous InGaZnO thin-film transistors (TFTs) fabricated on free-standing large-area plastic substrates address this issue by providing a carrier mobility >10 cm 2 /Vs, and bendability down to radii as small as 25 μm. At the same time, limitations such as a constrained minimum lateral feature size, the lack of appropriate p-type materials, or the influence of strain have to be considered when designing circuits. Here, models describing the scaling and bending behavior of flexible InGaZnO TFTs, together with the design of strain insensitive circuits operating at megahertz frequencies are presented

Flexible InGaZnO TFTs with fmax above 300 MHz

n this letter, the AC performance and influence of bending on flexible IGZO thin-film transistors, exhibiting a maximum oscillation frequency (maximum power gain frequency) fmax beyond 300 MHz, are presented. Self-alignment was used to realize TFTs with channel length down to 0.5 μm. The layout of this TFTs was optimized for good AC performance. Besides the channel dimensions this includes ground-signal-ground contact pads. The AC performance of this short channel devices was evaluated by measuring their two port scattering parameters. These measurements were used to extract the unity gain power frequency from the maximum stable gain and the unilateral gain. The two complimentary definitions result in fmax values of (304 ± 12)MHz and (398 ± 53) MHz, respectively. Furthermore, the transistor performance is not significantly altered by mechanical strain. Here, fmax reduces by 3.6% when a TFT is bent to a tensile radius of 3.5 mm

Spatial Distribution of Nucleosynthesis Products in Cassiopeia A: Comparison Between Observations and 3D Explosion Models

We examine observed heavy element abundances in the Cassiopeia A supernova remnant as a constraint on the nature of the Cas A supernova. We compare bulk abundances from 1D and 3D explosion models and spatial distribution of elements in 3D models with those derived from X-ray observations. We also examine the cospatial production of 26Al with other species. We find that the most reliable indicator of the presence of 26Al in unmixed ejecta is a very low S/Si ratio (~0.05). Production of N in O/S/Si-rich regions is also indicative. The biologically important element P is produced at its highest abundance in the same regions. Proxies should be detectable in supernova ejecta with high spatial resolution multiwavelength observations.Comment: To appear in the Conference Proceedings for the "10th Symposium on Nuclei in the Cosmos (NIC X)", July 27 - August 1 2008, Mackinack Island, Michigan, US