Myat, Inc.

Andrew Passive Power Products, Inc.

Electronics Research, Inc.

Derek J Small

John A Lunn

Ingo B Joedicke

Wade O Kemp

A method and apparatus are disclosed for combining digital sidebands with an FM analog signal for IBOC transmission by a single antenna. Specifically, a high power filter combiner for combining an FM analog and a digital signal of the same channel, or frequency, is disclosed. The combiner has two inputs that respectively receive an FM analog and a digital signal to be transmitted in the same FM channel. The combiner has mild tuned filters interposed between the inputs and the output which are tuned to pass the FM analog signal while reflecting the digital signal such that the passed FM analog signal and the reflected digital signal combine as IBOC, i.e., an FM analog signal with digital sideband signals. The combined IBOC signal is provided at an output of the combiner, capable for transmission through a single antenna.

Medium loss high power IBOC combiner

A bandpass filter makes use of at least one waveguide cavity that is thermally compensated to minimize drift of a resonant frequency of the cavity with thermal expansion of cavity components. The compensation relies on deformation of the shape of at least one cavity surface in response to thermally-induced dimensional changes of the cavity. A control rod is used to limit the movement of a point on the deformed surface, while the rest of the surface moves with the thermal expansion. The control rod is made of a material having a coefficient of thermal expansion that is significantly different than that of other filter components. The rod may also be arranged to span more thermally expandable material than defines the filter such that, as the filter expands, the point of deflection is moved toward the interior of the filter beyond its original position. A similar effect may be accomplished by connecting the control rod to an end deflecting rod that does the actual limiting of the movement of the deflection point. If the end deflecting rod has a coefficient of thermal expansion that is higher than that of the control rod, the end deflecting rod will expand with temperature relative to the end of the control rod, forcing the deflection point inward.

Temperature compensated high power bandpass filter

A multiple-section bandpass filter for broadcast communications includes adjacent waveguide segments with a perpendicular connecting segment between them to form a U-shaped signal path. The waveguide cavities of the segments may be extruded and rectangular in cross section, and have a groundplane spacing that allows signal propagation between filter sections by evanescent coupling. Resonators in each of the adjacent segments have a separation that establishes the coupling bandwidths without the need for passive decoupling structures. A cross coupling conductor between the adjacent segments provides a capacitive or inductive coupling between them. A decoupling structure may be located in the connecting segment.

Multiple-section bandpass filter for broadcast communications

A bandpass filter makes use of at least one waveguide cavity that is thermally compensated to minimize drift of a resonant frequency of the cavity with thermal expansion of cavity components. The compensation relies on deformation of the shape of at least one cavity surface in response to thermally induced dimensional changes of the cavity. A control rod is used to limit the movement of a point on the deformed surface, while the rest of the surface moves with the thermal expansion. The control rod is made of a material having a coefficient of thermal expansion that is significantly different than that of other filter components. The rod may also be arranged to span more thermally expandable material than defines the filter such that, as the filter expands, the point of deflection is moved toward the interior of the filter beyond its original position. In an alternative embodiment, an end plate of each cavity is secured to the rest of the cavity along its periphery, and has a convex shape facing away from an interior of the cavity. As the cavity expands radially, it forces the convexity of the end plate inward, compensating for the expansion in other cavity dimensions.

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Raymond, ME, United States of America

Derek J Small