Showing papers on "Return loss published in 1984"

Quarter-Wave Matching of Waveguide-to-Finline Transitions (Short Papers)

Abstract: This paper presents closed-form expressions for the design of a quarter-wave transition-matching transformer. This structure takes the form of a notch or protrusion cut in the finline substrate at the waveguide-to-finline interface. The dimensions of the transformer are calculated using a homogeneous waveguide model for the partially loaded sections. The characteristics of this model are found with perturbation theory. Several transformers were designed and measured. A 5-dB improvement in return loss over a full waveguide band is typical.

Power loss at a step discontinuity in an asymmetrical dielectric slab waveguide

Abstract: Power loss at an abrupt but small step discontinuity in an asymmetrical single-mode waveguide is analyzed. An integral expression is given for the power loss suffered by the transverse-electric and transverse-magnetic modes as a function of wavelength, film index, cover index, substrate index, and input and output waveguide widths so that any slab-waveguide discontinuity can be analyzed. Normalized power-loss plots are presented for two specific, commonly used waveguides with different degrees of asymmetry. It is shown that the magnitude of the power loss at a discontinuity depends more on the mismatch in the modal effective width than on the geometrical mismatch in waveguide width. In particular, close to cutoff, guides exhibit severe power loss even for small step size, whereas waveguides that are sufficiently far away from cutoff can tolerate a relatively large step discontinuity with surprisingly low power loss.

A Wideband 60 GHz 16-Way Power Divider/Combiner Network

Abstract: A 16-way, low-loss, wideband power divider/combiner network for V-band waveguide is described This network utilizes a section of radial waveguide operating in the TEM mode Over a frequency band of 55-67 GHz, this 16-way divider/combiner network has an insertion loss of 1 dB maximum and better than 12 dB return loss Matching elements which have been designed for each of the three transitions between different transmission media within this network are described in detail

Continuously variable phase shifting element comprised of interdigitated electrode MESFET

Abstract: A bidirectional continuously variable phase shifting element is described for incorporation in a monolithic microwave integrated circuit (a circuit which combines both passive and active circuit elements). The preferred active device for use in the phase shifting element is a variable resistance field effect transistor (MESFET), while the preferred passive circuit element is a short transmission line interconnecting the principal electrodes. A variable phase shift for an RF signal passing through the phase shifting element is obtained by adjusting the gate potential of the MESFET between full conduction and nonconduction. The change in conductivity of the MESFET causes the serial impedance of the phase shifting element to vary from a substantially resistive impedance to a substantially capacitively reactive impedance arrangement, which requires only a single active device, is applicable to frequencies generally above 1 GHz, and provides phase shifts up to 45° with reasonable insertion loss and return loss.

Optimal Waveguide to E-Plane Circuit Transitions with Binomial and Chebyshev Transformers

Abstract: This paper presents closed-form expressions for the design of quarter-wave transformer sections for matching fin line tapers to their commensurate waveguide. The formulae have been derived using perturbation theory and homogeneous waveguide models. Measurements show that such transformers improve the return loss of transitions by more than 5 dB over a whole waveguide band.

Quarter Wave Transformers for Matching Transitions Between Waveguides and Fin Lines

Abstract: This paper presents closed-form expressions for the design of a quarter-wave transition-matching transformer. This structure takes the form of a notch or protrusion cut in the finline substrate at the waveguide-to-finline interface. Measurements show a 5 db improvement in return loss over a full waveguide band due to such a transformer.

An MMIC/MIC-to-Waveguide Transition for Single- and Dual-Polarization Systems

Abstract: A simple, low-cost, 20-GHz MMIC/MIC-to-waveguide septum-type transition is described for rectangular, square, or circular waveguides operating in single- or dual-polarization modes. The MMIC is attached to a dielectric substrate surface with a circuit that transforms the waveguide impedance to that of the MMIC. Good insertion loss, return loss, and cross polarization are measured.

Design Consideration For Single-Mode Fiber Connectors

Abstract: Similarly as multimode fiber systems, practical single--mode systems require demountable connectors for terminating components, system reconfiguration, testing and maintenance. Since these single-mode systems are usually large - capacity long-haul systems, the connectors, as well as the other components, must have high performance characteristics so that the span lengths can be maximized. The first concern for the connector designer then is to minimize the insertion loss of the connectors. Since single-mode fibers have core diameters on the order of 5 to 10 microns, compared with 50 to 100 microns for multimode fibers, single-mode connector designs must provide fiber-to-fiber alignments to submicron precision. High-performance single-mode connectors, in both factory and field installed versions, have been reported that provide lateral offsets of less than 1 micron and angular misalignments of less than 0.5 degrees. For typical single-mode fibers, these alignments result in insertion losses on the order of 0.5 dB. Since reflections from connectors, and/or other components, may affect the longitudinal mode spectrum and noise characteristic of laser transmitters and cause system degradation, the return loss of the connector is also of concern to the designer. It has previously been reported that fiber-to-fiber end-face contact can substantially reduce reflections without the use of index matching, resulting in return losses of about 30 d2. Using Gaussian field theory, we will present the combined effect of lateral offsets, longitudinal offsets, and angular misalignments between two butt-jointed single-mode fibers having unequal mode-field radii. The expected insertion loss of connectors based on a statistical model of the effect of typical misalignments and fiber mismatches will be presented and compared with empirical measurements of single-mode connectors. Good agreement between the theoretical model and experimental data is realized.

Band-Pass Filters in Integrating Waveguide Technology and Adapters to Standard Waveguides

Abstract: Standard waveguide circuits do not lend themselves to integration as do circuits made according to the INWATE process. In this paper 10 GHz and 30 GHz INWATE band-pass filters which do not require tuning are described with regard to their manufacture and measurement results. At relative bandwidths of about 0.07 pass-band insertion loss is less than 0.6 dB and 0.8 dB. Temperature variations between -30°C and +60°C do not cause observable changes in the insertion loss characteristic. The 10 GHz filters include adapters to standard waveveguides which have been designed experimentally and separately. An adapter design chart for return loss > 17 dB is presented.