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Advances in Passive Microwave Components (Digest No.: 1997/154), IEE Colloquium on

Date 22 May 1997

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Displaying Results 1 - 8 of 8
  • Linewidth reductions in garnet ferrites

    Publication Year: 1997 , Page(s): 3/1 - 3/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    The linewidth of a ferrimagnetic material is a measure of the magnetic loss caused by gyromagnetic resonance of the iron electrons. The authors investigate the effect of substitutions in YIG on properties such as saturation magnetisation, linewidth and Curie temperature. Initial results indicate that tin is effective in reducing linewidths and improving Curie temperature View full abstract»

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  • Mode matching design of three-way waveguide power dividers

    Publication Year: 1997 , Page(s): 5/1 - 5/4
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    The synthesis of three-way H-plane rectangular waveguide combiner/divider networks using mode matching is described. Predicted and measured results for a WG16 design example are given. The technique provides insight into the combiner/divider operation and a dramatic improvement in computing time compared to previously reported designs, based on optimization by finite element analysis View full abstract»

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  • Third order intermodulation performance of above resonance circulators

    Publication Year: 1997 , Page(s): 4/1 - 4/6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    One topic which has received little attention in the engineering literature is the optimisation of third order intermodulation products in stripline ferrite circulators biased above ferromagnetic resonance. A technique which may be used to gain insight into possible adjustments of this parameter is to construct an experimental mode chart detailing the resonant frequency variation of the first pair of degenerate counter-rotating modes in this sort of device and the main Kittel resonance as the external magnetic field is varied. In this paper a description of the intermodulation effect in terms of a nonlinear transfer function is presented as a preamble to the construction of experimental mode charts for two different gyromagnetic resonators and a study of their associated intermodulation performance View full abstract»

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  • Low loss ceramic dielectrics for microwave filters

    Publication Year: 1997 , Page(s): 6/1 - 6/6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Certain dielectric oxide single crystals display very low loss at microwave frequencies. On cooling the loss is generally observed to drop. The Q of sapphire at 10 GHz exceeds 106 at low temperatures of around 10 K. However, single crystals are expensive and the purpose of this research is to explore inexpensive, sintered polycrystalline alternatives. By very careful attention to purity, processing and microstructure Q values approaching those of single crystals have been achieved. The loss of polycrystalline ceramics of Al 2O3, Ba(Mg1/3Ta2/3)O3 (BMT) and Zr0.875Sn0.25Ti0.875O 4 (ZTS) has been studied. Alumina, Al2O3 has been studied as a model material for dielectric loss. Theory predicts that the loss in single crystal sapphire should follow a T5 dependence. However at low temperatures the loss is dominated by extrinsic losses due to crystal imperfection, residual dopant atoms, dislocations and other lattice defects and the T5 dependence does not hold In polycrystalline alumina the intrinsic loss is immediately masked by these extrinsic losses, even at room temperature, and a simple T dependence is observed. Results on polycrystalline alumina show that a Q of >5×104 at 10 GHz and at room temperature are possible and Q's well in excess of 105 at 10 GHz and 77 K can be achieved in a design made compact by the use of a HTS thick film shield View full abstract»

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  • Recent advances in microstrip filters for communications and other applications

    Publication Year: 1997 , Page(s): 2/1 - 2/6
    Cited by:  Papers (5)  |  Patents (16)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    Modern microwave communication systems require, especially in satellite and mobile communications, high-performance narrow-band bandpass filters having low insertion loss and high selectivity together with linear phase or flat group delay in the passband. Usually, these criteria are fulfilled using waveguide cavity or dielectric resonator loaded cavity filters because of their low loss. However, in order to reduce size, weight and cost, there has been a growing interest in planar structures. The disadvantage of high conductor loss of the planar filters using conventional conducting thin films can be overcome by replacing them with high-temperature superconducting (HTS) thin films. These can have a very low conductor loss. An alternative is by combining with active MMIC devices to compensate the loss. Under those driving forces many novel types of microstrip filters have recently been developed. This paper is intended to address this development. Different types of newly developed microstrip filters, particularly those developed at the University of Birmingham, such as slow-wave microstrip filters, cross-coupled microstrip filters and miniature dual-mode microstrip filters are presented View full abstract»

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  • Interconnect structures for integrated microwave and millimetre wave circuits: current status and trends

    Publication Year: 1997 , Page(s): 7/1 - 7/6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    Applications requiring high frequency IC interconnect range ever more widely: from cellular phones, indeed the entire wireless sector, to millimetre-wave automotive radars. Highly-miniaturised communications and radars require small and compact overall designs with unobtrusive antennas. Operating frequencies extend over many decades of the spectrum: from around 900 MHz to 1 THz (1,000 GHz) for submillimetre-wave technology. The technological capability is generally available now-commercially in the case of microwave and well into the millimetre-wave bands. There are, however, many areas in which leading-edge research is being performed. These include novel designs, the challenges of cost-critical applications, and high millimetre-wave or submillimetre-wave approaches. The possible available technologies range from microstrip to suspended substrate and dielectric waveguide, but the selection of an appropriate technology fix the interconnection of MMICs is a critical decision View full abstract»

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  • Filter design with lossy circuit elements

    Publication Year: 1997 , Page(s): 1/1 - 1/6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    Resonator losses in narrow-band microwave filters can lead to an unacceptable deterioration in performance. To avoid these effects large high Q resonators are often used. Alternatively, predistortion techniques may be used to correct for the effects of losses in bandpass filters. There is little information in the available literature on predistorted bandstop filters. In this paper a brief description of the effects of losses is followed by a review of classical predistortion for bandpass filters. This is followed by a presentation of new design techniques for predistorted transmission and reflection mode filters View full abstract»

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  • IEE Colloquium on Advances in Passive Microwave Components (Ref. No.1997/154)

    Publication Year: 1997
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (40 KB)  

    The following topics were dealt with: filter design with lossy circuit elements; microstrip filters and applications; linewidth reductions in garnet ferrites; above resonance circulators; mode matching design of waveguide power dividers; low-loss ceramic dielectrics; interconnect structures for integrated microwave and MM wave circuits View full abstract»

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