Abstract: A filter pack is formed of a pleated filter section and a channel that forms a frame. The filter section may be formed of a non-woven polymer material which has been pleated. The filter section may have edge banding along at least a portion of its periphery. The filter section may be retained in the frame by an adhesive. One or more filter sections may be combined to form a filter pack. The frame may be continuously formed from an extruded plastic which may be folded to provide a one, two, three or four part frame. The frame may be provided with living hinge and mechanical locking features. A foldable edge band may be provided to allow the joining of multiple filter sections into larger filter packs.

Abstract: In an amplifier circuit having an amplifier path, a new pre-distortion arrangement is provided. The amplifier circuit includes a signal source, an intermediate amplifier stage, and a power amplifier stage connected sequentially, in series along the amplifier path. The power amplifier stage includes one or more amplifiers operationally connected in parallel, and one or more pre-correction circuits. Each of the amplifiers subjecting an inputted signal to shifts away from their intended values. Each of the pre-correction circuits is associated with one of the amplifiers and connected between an output of the intermediate amplifier stage and the associated amplifier. Each of the pre-correction circuits pre-distorts the signal input to the associated amplifier to compensate for the distortion caused by the associated amplifier.