Uwe Rosenberg

Advanced multimode cavity filter design using source/load-resonance circuit cross couplings

Several degenerate resonances of one cavity are simultaneously coupled to the same interface (waveguide) port that represents source or load of the network. This new method extends significantly the design possibilities for multimode cavity filters-odd-order true elliptic function designs are now possible along with other conspicuous design variants by novel coupling structures. Experimental verification is provided for this approach by a three-order elliptic function filter realized with one triple-mode cavity.<<ETX>>

A Novel Band-Reject Element for Pseudoelliptic Bandstop Filters

A novel band-reject element for the design of inline waveguide pseudoelliptic band-reject filters is introduced. The element consists of an offset partial-height post in a rectangular waveguide in which the dominant TE10 mode is propagating. The location of the attenuation pole is primarily determined by the height of the post that generates it. The element allows the implementation of weak, as well as strong coupling coefficients that are encountered in asymmetric band-reject responses with broad stopbands. The coupling strength is controlled by the offset of the post with respect to the center of the main waveguide. The posts are separated by uniform sections of the main waveguide. An equivalent low-pass circuit based on the extracted pole technique is first used in a preliminary design. An improved equivalent low-pass circuit that includes a more accurate equivalent circuit of the band-reject element is then introduced. A synthesis method of the enhanced network is also presented. Filters based on the introduced element are designed, fabricated, and tested. Good agreement between measured and simulated results is achieved

Power splitting transition for circularly polarized feed networks

A new power splitting transition is introduced that is based on a step transformer approach for interfacing two square waveguides with a mutual alignment of the cross sections of 45/spl deg/. It is shown to provide high-performance matching properties while maintaining easy and low-cost fabrication. A well-suited mode matching CAD has been used for study and hardware design. Verification is provided by experimental results of transitions realized for the 27 GHz band.

High-performance transitions for overmoded operation of elliptical waveguides

Overmoded elliptical waveguide systems are shown to provide considerable lower insertion loss compared with standard types using the frequency band with exclusive TE/sub c11/ fundamental mode propagation. The considerations for the overmoded waveguide operation are outlined. A novel transition design based on transformer steps with curved cross sections and containing means for higher order mode control is established for interfacing the oversized elliptical cross section with the standard rectangular waveguide ports. The accurate determination of the transition structure maintaining high performance demands is obtained by a suitable computer-aided-design procedure. The overmoded waveguide approach, including the transition design, is proven by computed and experimental results for a millimeter-wave design.

Design of bandstop filters using cylindrical metallic posts

The paper presents the design, implementation and measured performance of waveguide band-reject filters based on partial height cylindrical metallic posts. The posts are inserted in a uniform waveguide in which the dominant TE10 is propagating. Each post provides an attenuation pole at a frequency which is adjusted mainly by its height. The offset of the post from the center of the waveguide is used to control the strength of the coupling between the waveguide mode and the post. Optimization is used to correct for dispersion effects and the fact the attenuation pole and the coupling coefficients are slightly affected by the offset and the height of the post, respectively. Measured performance of a 3rd order band-reject filter with metallic posts shows very good agreement with computed results once losses are taken into account.

Compact Diplexer Design Using Different E-Plane Triplets to Serve Contiguous Passbands with High Interband Selectivity

An advanced compact E-plane triplet cavity arrangement is introduced to provide either the implementation of transmission zeros (TZs) above or below of a filter passband. The principle configuration allows the realization of inductive (TZ above passband) and capacitive (TZ below passband) irises to accommodate with the respective sign conventions for the filter couplings. This general triplet cavity structure is applied to a compact diplexer design using 6th order filters with asymmetric responses at 10GHz. Each filter consists of two cascaded triplets controlling independently two TZs close to one side of the passband to satisfy the high interband selectivity of the contiguous receive and transmit bands. The overall design concept has been proven by the realization of the diplexer. Good agreement of computed and measured results are obtained. Moreover, the comfortable margins regarding the requirements admit of production without the need of any tuning

Advanced Receive/Transmit Diplexer Design For Emerging mm-Wave Access Radio Applications

The application of asymmetric filter characteristics with transmission zeros (TZs) in advanced diplexer designs is shown to provide low insertion loss while maintaining the high interband isolation for the operation of radio equipment. The transmission zeros of each filter at finite frequencies are realized by dedicated cavity resonances at the single filter input ports (extracted poles) and by triplet sections in the signal paths between the single and common port interfaces. Consequently, the individual TZs of each filter can be controlled independently in an overall compact cavity structure. All cavities are arranged in an H-plane structure. The interfacing of the respective cavities at all ports by E-plane T-junctions facilitates the compactness. The interfaces are realized at one side (below the cavity structure) for easy integration and mounting. The frequency allocations of the different channels can be easily exchanged by mounting the diplexer in a 180-degree position. This is possible due to a point symmetry for the single channel ports with respect to the common port. The validity of the approach has been proven by an advanced diplexer design for a new 39GHz access radio application. The diplexer with 6th order filters - each having an asymmetric response with two TZs - exhibits good coincidence of theoretical and measured results and thus proves the novel design approach

New Dual-Mode Circular Cavity Pseudo-Elliptic Filters

The paper presents a new design of dual-mode circular cavity filters. The circular cavities are homogeneous and contain no coupling elements. Each cavity can generate and control one transmission zero at a finite frequency. A major advantage of these new filters is their ease of fabrication by milling techniques. The cavities and the coupling elements can be milled out of a single metallic piece which is then completed by a metallic cover plate