Communications Satellite Corporation

Comsat Corporation

Communications Satellite Corporation (comsat)

Albert Edward Williams

Ali E Atia

Amir Ibrahim Zaghloul

John I Upshur

Ozlem Killic

Mohammed Mahbubur Rahman

Rene R Bonetti

This disclosure describes a method to generate large numbers of spot beams for multiple-beam satellite systems using smaller apertures. This is done by dividing the basic spot beam that has 3 to 4 dB of gain drop within the beam into a number of smaller 1-dB sub-beams. This has the effect of reducing the required peak gain for the antenna by 2&#x2013;3 dB, thus reducing its size by as much as 50%. The frequency band allocated to the basic beam will be divided among the sub-beams. However, the frequency re-use among the basic beams can be maintained. Frequency allocations have to be coordinated among all beams. This concept is especially applicable to phased arrays using digital beam formers. The DBF complexity is a function of the number of array elements, and is less dependent on the number of beams. Reducing the array size, and consequently reducing the number of elements helps in reducing the complexity, power and mass of the DBF.

Smaller aperture antenna for multiple spot beam satellites

Asynchronously-tuned coupled resonator cavities are implemented having a minimum set of inter-resonator couplings, wherein the filter design incorporates only series and parallel couplings. By way of example, 8 order filter topologies having three transmission zeros, no cross-couplings, and only eight series and/or parallel couplings can be achieved.

Asymmetric response bandpass filter having resonators with minimum couplings

The present invention is directed to reducing the number of components required to minimize intermodulation distortion within the wide transmission frequency band used by a satellite communications repeater system. In particular, at least two TM.sub.010 mode cavity is cascaded to a plurality of TE.sub.113 mode cavities to form a narrow band-pass, wide band-stop filter for receiving and outputting channel signals to the multiplexer manifold of a satellite repeater. The filter thus constructed realizes the narrow band-pass response required in microwave communications, while eliminating the spurious resonance frequencies normally eliminated by additional filter components. In this manner, the size and weight considerations of the satellite system are improved without loss in performance.

Microwave filter with a wide spurious-free band-stop response

The relative positions of the cavities in known single or dual mode multiple coupled cavity waveguide bandpass filters are rotated to achieve new filter structures in which the primary cavity couplings remain intact while the secondary couplings are shifted. The cavity rotation provides design flexibility since the input and output ports can now be taken from the same side of the filter structure. An additional advantage in dual mode filters is that the rotation permits the physical separation of input and output cavities, thereby providing increased isolation and eliminating spurious out-of-band coupling.

Multiple coupled cavity waveguide bandpass filters

Multiple coupled high Q cavities are used to generate odd order elliptic function band-pass filters using a minimum number of cavities connected by simple and resonant coupling elements. A specific embodiment of a 3-pole, 20 MHz band-pass wave guide cavity filter centered at 3890 MHz is disclosed. Couplings between cavities may be either on the end walls or the side walls. The simple coupling elements may be simple coupling holes, and the resonant coupling elements may be a non-shorting screw in a window between cavities.

Odd order elliptic function narrow band-pass microwave filter

A plural cavity waveguide filter comprising a plurality of cascaded waveguide cavities each resonating in first and second independent orthogonal modes is disclosed. The cavities may be either square and/or circular resonating in the TE.sub.101 or TE.sub.111 modes, respectively. The filter makes it possible to realize the general class of coupled cavity bandpass transfer filter functions by providing that the input and output couplings to the filter be physically connected to the first physical cavity. A general set of canonical couplings can then be achieved within the structure.

Canonical dual mode filter

A waveguide structure composed of circular waveguide cavities resonant in the TE.sub.011 mode is capable of realizing the most general bandpass filter characteristics with significant decreases in filter loss and gain slope. In addition to the commonly used Tchebychev and Butterworth functions, the structure can realize general transfer functions including the elliptic function. In its simplest form, the structure is composed of four cylindrical cavities which form a building block for more complex filters. The first and second cavities and the third and fourth cavities each have their side walls in contact and their end walls in common planes. The third and fourth cavities are superposed to the first and second cavities with their adjacent end walls in a common plane, but the second and third cavities are offset so that they overlap at one-half diameters. The first and second cavities are coupled by means of a centrally located side wall slot, as are the third and fourth cavities. Coupling between the second and third cavities is by means of a radial slot in their adjacent end walls, and the first and fourth cavities are similarly coupled. However, to generate the most general class of coupled transfer functions, the sign of the coupling between the first and fourth cavities and between the second and third cavities must be different. This is accomplished by the offset of the second and third cavities.

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Bethesda, MD, United States of America

Albert Edward Williams