Abstract: An arbitration and synchronization method and system for allowing multiple processors to access a shared memory includes an arbitrator. The arbitrator is operable with the processors for enabling each of the processors exclusive access to the memory for a predetermined time period on a rotating basis. In operation, a time period of a time frame is associated with each of the processors. The time periods of the time frame are then counted. The arbitrator then enables a processor to have exclusive access to the shared memory for the time period associated with the processor when the counted time period is the time period associated with the processor.

Abstract: A digital signal processing architecture for an audio system combines multiple functions in programmable and reconfigurable blocks to achieve an efficient use of hardware and chip area. AM, FM, and audio functions can be performed using the same reconfigurable hardware while taking into account the different sample rates and processing functions required for each.

Abstract: A carrier-based signal is received from a tuner and is digitized to produce a digital intermediate frequency (IF) signal. Automatic gain control is applied to the carrier-based signal either prior to or after digitization. An adaptive intermediate frequency bandwidth control system detects IF signal level after channel filtering. The level is compared to a predetermined threshold having a value related to the known signal level of the AGC'ed signal which is being input to the channel filter in order to provide a measure of either 1) the presence of interfering adjacent channels, or 2) reception or a weak signal which can't be compensated for by AGC. The IF bandwidth is narrowed in either circumstance. Digital FIR or IIR filtering is used. The invention allows bandwidth switching to be done very quickly with minimal transient effects. A threshold value is selected depending upon the IF channel bandwidth being used at any given time.

Abstract: An adaptive intermediate frequency bandwidth control system detects IF signal levels both before and after channel filtering. The two levels are compared to provide a measure of the presence of interfering adjacent channels. This measure is compared to a programmable threshold and the IF bandwidth is narrowed if any interferers are detected. Digital FIR or IIR filtering is used. The invention allows bandwidth switching to be done very quickly with minimal transient effects. A difference threshold is selected depending upon the IF channel bandwidth being used at any given time.

Abstract: A radio receiver avoids overshoot or undershoot of its audio output caused by inadequate AGC loop response when driving under an underpass and then back into an unobstructed environment. The AGC loop response time is changed upon detection of the sudden decrease in signal level when entering the underpass. The state of the AGC loop prior to entry into the underpass is stored. Upon exiting the underpass, the stored values are restored so that a proper reception level is immediately obtained.

Abstract: A digital mixer-filter-decimator (MFD) is disclosed which is reconfigurable so that it can be used in both modes of operation of a dual mode receiver such as an AM/FM receiver. In either mode of operation the MPD performs filtering and decimation operations on separate data streams containing alternate samples of a digital input data stream. In the FM mode a mixing operation is also enabled to produce a complex output comprising in-phase and quadrature components. The mixing operation is disabled in the AM mode and the filtered and decimated outputs are combined to provide a real output. The same decimator filter can be used in both modes.