aperture-coupled patch type was designed and produced using a LTCC process. The results show a 13.8% bandwidth from the 10-dB return loss and an 8.3% bandwidth from the 15 dB loss. The 0.6-dB loss was caused only by the transition itself. The transition proposed in this article would be used in designing transitions that allow components with a center frequency of 60 GHz and microstrip lines for an input/output terminal, embed a waveguide port. 3. B.J. Jang, I.B. Yom, and S.P. Lee, Millimeter wave MMIC low noise amplifiers using a 0.15um commercial p-HEMT process, ETRI J 24 (2002), 190-196. 4 [5]. Application of the SCM technique appears to be attractive as the SCM transmission may coexist with any form of baseband communication, and the multiplexing and separation of signals/channels are performed in the electrical domain by inexpensive RF/microwave devices. SCM systems operating over MM fibers that have been demonstrated till now were exclusively digital ones with few (typically one or two) high bit rate channels [2,3].In this article, we show for the first time that there is a possibility of high-quality transmission of analog TV channels (AM) by the employment of SCM technique beyond the baseband of MM fiber. EXPERIMENTThe goal of the experiment was to verify whether analog TV signals (videoþaudio) in PAL format may be successfully transmitted beyond the baseband of MM fiber. We used a typical (FDDI grade) silica GI fiber with 50 lm core and modal bandwidth of 500 MHz km at 1310 nm manufactured by Corning. The fiber was 4.4 km long, and its frequency response under actual conditions (OFL excitation) is shown in Figure 1. The 3 dB baseband width was around 150 MHz, which is in good agreement with the data sheet value calculated for 4.4 km long fiber (500 MHz km/4.4 km). Along this fiber, we transmitted four complete analog TV (PAL) channels of AM-DSB format. The choice of DSB instead of typical VSB format was dictated by the type of TV modulators, we owned. The latter made possible the selection of the channel subcarrier frequency in the UHF range. Due to the MM fiber frequency response, we used the interval between 607.25 and 703.25 MHz as the SCM transmission band.A block scheme of the transmission system is shown in Figure 2. Audio/video signals from four DVD players modulated amplitudes of four subcarriers. Due to the DSB modulation format, the minimum subcarrier spacing was 16 MHz, which is double the 8 MHz standard PAL channel separation. These AM-DSB signals were fed to variable gain amplifiers used for signal level equalization in all channels. The signals from amplifiers outputs were added in a 4 Â 1 RF combiner and through another variable gain amplifier (necessary for modulation index adjustment) drove a commercial 1310 nm DFB laser used in CATV systems (ORTEL 1688 built in commercial CATV transmitter). The mean optical power in the fiber was around 2 mW. The modulating signal was monitored by an oscilloscope. After the transmission in MM fiber, the signals were photo-detected (JDSU ETX100 photod...
INTRODUCTIONPrinted-circuit lines have become the standard transmission lines in today's MIC. During the last thirty years hundreds of papers have discussed their properties, their behaviour and the modifications most suitable for particular applications. The conductor-backed coplanar waveguide and the conductor-backed slotline (CBSL) are interesting transmission lines since they enable circuits to be located on a metal base, ensuring improved mechanical strength, good heat sinking and easy dc biasing. Their great drawback is a leakage of power in the substrate resulting in undesired coupling to the neighbouring circuit sections. That is why the CBSL has stood somewhat at the margin of the interest of designers and only a few publications [1-3] have worked on analyzing it.The purpose of this paper is to bring the attention of designers back to the CBSL and to clarify the line features in terms of the even and odd mode dispersion characteristics. Two new dominant modes are revealed and the influence of line dimensions on CBSL properties is presented. The dependence of the dispersion characteristics on the slotwidth exhibits a new unexpected evolution not previously observed on other planar transmission lines. Measurement of the even dominant wave and the even 1st leaky wave confirms theoretically derived observations. Conclusions drawn from the analysis result in recommendations for CBSL users.
-This paper presents a detailed full-wave analysis of the conductor-backed slotline. The occurrence of an even dominant mode is revealed. This mode may propagate alone from dc up to the frequency at which the first leaky mode sets up. Nonphysical solutions of the dispersion equation and also the second leaky mode, taking power in the substrate, are identified. The first odd space leaky mode revealed on the CBSL enable an entirely uniplanar leaky wave antenna to be designed. The dispersion characteristics of particular revealed modes and their field distributions on the cross-sectional plane are also presented.
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