Approximate Design Method Research Articles

The design of sealing devices for thermo-plasticised stretching of fibres in saturated steam

By using an approximate design method for multi-chamber sealing head devices for high-temperature plasticised stretching of fibres, it is possible to establish optimum parameters for the sealing heads (number of chambers and diameter of apertures) so as to ensure a minimum and economically acceptable amount of steam leakage.

Approximate design methods for high response digital control systems

Approximate design methods for high response digital control systems

Approximate method for plug nozzle design

Approximate method for plug nozzle design

Coupled Circular Cylindrical Rods Between Parallel Ground Planes

The normalized self and mutual capacitances of periodic, circular cylindrical rods located between parallel ground planes are presented graphically. The capacitances were determined by solving the appropriate integral equation by numerical methods. Charts of self and mutual capacitance are given for rod diameter-to-ground plane spacing ratios varying from 0.05 to 0.8 and for very small to very large spacings between rods. Accuracy of the data is believed to be generally better than 2 per cent for the normalized mutual capacitance and generally better than 1 per cent for the normalized self capacitance. An approximate design method is also presented that permits using the data to synthesize filters (such as interdigital and comb-line filters) that require rods of nonequal diameters and spacings. An example of the design method is given, and a filter is constructed from the resulting data. The filter response was measured and found to agree closely with that called for by the theory.

Design of Wide-Band (and Narrow-Band) Band-Pass Microwave Filters on the Insertion Loss Basis

A method for design of band-pass microwave filters is described that combines the image and insertion-loss points of view to give an approximate design method having simplicity, but also high precision. This method is applicable for filter designs ranging from narrow to very wide bandwidths (2 to 1 or more). The desired insertion loss characteristic is obtained by use of a lumped-element, Tchebycheff, or maximally flat (or other) low-pass prototype. With the aid of the concept of impedance inverters, the prototype is converted into a cascade of symmetrical (but differing) sections. The image properties of symmetrical sections of the band-pass microwave filter structure are then related to those of corresponding sections of the prototype. Straightforward design equations are given for filters using short-circuited or open-circuited stubs, and also for filters using parallel-coupled lines. Mapping functions are derived that permit accurate prediction of the microwave filter cutoff characteristic from that of the prototype. The responses of a number of filter designs were computed, and a Tchebycheff filter with a 2.2 to 1 band-width was built and tested. The reponses of all of the filter designs were in close agreement with the prescribed characteristics, and the accuracy of the mapping functions was verified.