Motorola Corporation

Charles Choi

Raymond L Sokola

Louis Jay Vannatta

James C Baker

David Grant Cason

Michael F Moutrie

Dale F Bengtson

The present patent application includes a discussion of a signal compensation apparatus (119). The apparatus is implemented in a digital radiotelephone (101) having diversity receivers (111, 113). The signal compensation apparatus utilizes three control loops and a branch selection switch circuit to substantially diminish the undesired gain and DC offset present in the selected received data signal. Portions of the apparatus are implemented in a digital signal processor (DSP) (249) for rapid adjustment of the control loops when switching to a different receiver branch.

Data signal compensation apparatus for use in a receiver

An interdigital microstrip transmission line filter (100) includes three electrically conductive strips (104, 106 and 108) each coupled to grounded portions (110 and 120) on one end and coupled to respective capacitive loading pads (112, 116 and 114) on the other end. Input and output pads (130 and 140) may be coupled to signals from other circuitry located off or on the same substrate (150). Grounded portion (110) extends between capacitive loading pads (112 and 114) for minimizing undesired coupling between non-adjacent strips (104 and 108). As a result, the unique microstrip filter (100) has a frequency response that is substantially devoid of passband transmission zeros.

Narrow bandwidth microstrip filter

A unique ceramic bandpass filter is disclosed that is comprised of a dielectric block having one or more holes extending from its top surface to its bottom surface and further having input and output electrodes each disposed on the dielectric block at a predetermined distance from a corresponding hole. The dielectric material is preferably a ceramic comprised of BaO, TiO.sub.2 and ZrO.sub.2. If there is only one hole in the dielectric block, the input and output electrodes may be arranged around that hole. If there are two or more holes in the dielectric block, one electrode may be located near the hole at one end and the other electrode may be located near the hole at the opposite end of the dielectric block. The dielectric block is entirely plated with copper or silver with the exception of portions near each hole and the input and output electrodes. Each plated hole is essentially a coaxial resonator. Coupling between adjacent coaxial resonators provided by the plated holes can be adjusted by slots or additional holes located therebetween. Two or more of unique ceramic bandpass filters can be intercoupled to provide a filter with greater selectivity or a multi-band filter for combining and/or frequency sorting two or more signals into/from a composite signal.

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Schaumburg, IL, United States of America

Charles Choi