Showing papers on "L band published in 1998"
01 Jan 1998
TL;DR: Several system alternatives are being considered for provision of mobile and personal satelite services in the near future, and the interesting frequency range covers L/S-band, K/Ka-band and the EHF-band.
Abstract: Several system alternatives are being considered for provision of mobile and personal satelite services in the near future. Many proposals adopt nongeostati onary satellite constellati ons, thus the channel characteristi cs are not stationary. Furthermore, multiple access techniques under consideration range from narrowband to wideband (e.g. CDMA) solutions. Finally, due to the requirement of being virtually global, a satellite system should provide service in a wide range of environmental conditions. The interesting frequency range covers L/S-band, K/Ka-band and the EHF-band.
11 citations
TL;DR: In this paper, the microwave emissions at 1.413 GHz (L band) and 2.65 GHz (S band) from a silt loam soil exhibited an oscillatory behavior in time as the soil was being irrigated.
Abstract: Observations of the microwave emissions at 1.413 GHz (L band) and 2.65 GHz (S band) from a silt loam soil exhibited an oscillatory behavior in time as the soil was being irrigated. The oscillations are attributed to interference between reflections from the air-soil interface and the wet soil-dry soil interface as the latter moved down in the soil. The magnitude of the first oscillation at L band was 56 K, and at S band it was 40 K, with oscillation damping out after about three cycles to the brightness temperature expected for the wet soil. The emission was modeled using a coherent model, and the results show qualitative and quantitative agreement with the observations.
10 citations
20 May 1998
TL;DR: In this paper, the design of a flat rotary joint with a very broad operating frequency band is described, which enables practical elimination of signal amplitude/phase and impedance changes considered as a function of rotation angle.
Abstract: The design of a flat rotary joint with a very broad operating frequency band is described. The solution proposed here enables practical elimination of signal amplitude/phase and impedance changes considered as a function of rotation angle. Low transmission and reflection loss have also been achieved. According to experimental results presented in this paper, fractional bandwidth of the model exceeds 50%, with maximum SWR of 1.8.
1 citations
11 May 1998
TL;DR: Two ICs have been implemented as part of a mobile digital satellite radio receiver that makes a superheterodyne frequency conversion from L band to 1.84 MHz IF, with a high level of integration, i.e only a SAW filter outside the chip.
Abstract: Two ICs have been implemented as part of a mobile digital satellite radio receiver. An RF front-end stage makes a superheterodyne frequency conversion from L band to 1.84 MHz IF, with a high level of integration, i.e only a SAW filter outside the chip. A fully digital channel decoder receives the IF signal from the RF front-end and converts it by means of an integrated 6-bit half flash A/D converter. Its main functions are a QPSK demodulator, a Viterbi decoder, a Reed-Solomon decoder, a deinterleaver and TDM extraction. The analogue input signal carrier is 1.84 MHz while the maximum chip frequency is about 10 MHz in order to optimize power consumption. Output data are transferred using a serial interface at a maximum rate of 128 kbit/s, The channel decoder is implemented using a five-metal layer CMOS 0.35 /spl mu/m process, complexity is 1.5 million transistors, dissipating 50 mW with die size of 23 mm/sup 2/. For the RF front-end, implemented in a 20 GHz bipolar process, die size is 16 mm/sup 2/, power consumption is about 200 mW, and includes on-chip low noise amplifier, 3.6 GHz oscillator and two PLL loops.