Higher ORDER MODE ANALYSIS USING FINITE DIFFERENCE

HIGHER ORDER MODE ANALYSIS USING FINITE DIFFERENCE

Coaxial waveguides and the determination of their cutoff frequencies have been discussed by Marcuvitz . This involves finding zeros of a function that involve products of Bessel functions of 1st kind and 2nd kind for TM modes and products of derivatives of Bessel functions of 1st kind and 2nd kind for TE modes. These zeros pertain to a certain order and need a number of iterations to be performed to obtain a set of cutoff wavenumbers. Finite difference methods in the conventional form have been applied t0 a variety of cross sections. However, the same technique involving the formation of rectangular meshes to a circular coaxial waveguide does not seem to be appealing in context with the selection of truncation boundaries and appropriate adjacent node points for the region between the inner and outer conductors. The increase in the number of spurious modes generated and the decrease in accuracy are also detrimental to this choice of meshing technique.
In my approach, the curvilinear rectangular grid formation  is used to mesh the region between the two conductors which enables us to encompass the cross-sectional region completely thus eliminating the necessity of truncation of the boundary. This also yields much accurate result than the conventional rectangular grid formation and is much simpler than the cumbersome method of finding roots from the closed form expressions. The Laplacian operator appearing in the Helmholtz equation in polar form is represented as a five-point difference operator along the radial and circumferential directions. The eigen values which give cutoff frequencies are evaluated from the characteristic equation expressed in terms of matrices obtained from a set of simultaneous equations satisfying the boundary conditions.
Read Complete Article…

Comments

  1. Anil PandeyNovember 25, 2016 at 7:05 PM

    same analysis can be done using Finite Element Method (FEM) solver also

    ReplyDelete

Post a Comment

Popular posts from this blog

Image
Slotted Waveguide Array Antenna Slotted antenna arrays used with waveguides are a popular antenna in navigation, radar, and other high-frequency systems. A waveguide is a very low loss transmission line. It allows propagating signals to a number of smaller antennas (slots). Each of these slots allows a little of the energy to radiate. Slot impedance and resonant behavior for a single slot are dependent on slot placement and size. Its exceptional directivity in the elevation plane gives it quite high power gain. The slotted waveguide has achieved most of its success when used in an omnidirectional role To make the unidirectional antenna radiate over the entire 360 degrees of azimuth, the second set of slots are cut on the back face of the waveguide. An 8×8 planar four pole X-band Tchebyshev dual inductive post substrate integrated waveguide filter from 10.15 GHz to 10.7 GHz is designed for terrestrial broadcasting. The filter is designed on the 5870 with a relative dielectric
Read more

Dual Channel Rotary Joint

Image
A Rotary Joint (RJ) is a wide spread microwave device that is used to change the direction of microwave propagation between two waveguides by rotating one with respect to another. Rotary joints find many applications in radar and satellite earth stations for functions such as polarization rotation; antenna feed systems and azimuth and elevation motions. Many styles of rotary joints are available for a variety of environmental conditions. Multichannel rotary joints must be carefully designed to achieve low channel loss and small rotational variations of this loss.   A n investigation was first carried out to review the state of the art in the field of multiple-channel rotary joints and to select the types of propagation modes that best satisfied the special system needs. A review of possible design approaches led to the selection of a concentric coaxial line configuration for the main body of the rotary joint, with integral transitions to waveguide at both ends for minimum over
Read more

QFN Package Simulation

Image
he Quad Flat No-lead (QFN) package is a CSP (plastic encapsulated package) with a copper lead frame substrate. QFN type package is one of the most cutting-edge IC packaging technologies in the electronics. The QFN is a leadless package where electrical contact to the PCB is made by soldering the leads on the bottom surface of the package to the PCB, instead of the conventional formed perimeter gull wing leads. The QFN-type package is known for its small size, cost-effectiveness and good production yields. QFN also possess certain mechanical advantages for high-speed circuits including improved co-planarity and heat dissipation. The QFN has pins on 4 edges of the bottom surface of the package. The QFN can have either a square or rectangle body as well as symmetric or asymmetric terminal patterns. The QFN was introduced to replace the gull wing lead Quad Flat Package (QFP) because the component leads are embedded in the plastic and cannot be bent during handling to insure consistent
Read more