Abstract: Misfiring of individual cylinders in an internal combustion engine is detected based on sensing exhaust pressure during each operating cycle of the engine. A pressure signal is sampled and digitized during each cycle to form an input vector for a pattern classifier. Predetermined internal coefficients of the trained classifier enable the classifier to discriminate between firing and misfiring cylinders in real time with a high degree of accuracy. Overall system cost is reduced by sharing a pressure transducer with an exhaust gas recirculation system on the internal combustion engine.

Abstract: The invention enhances the ability of rear seat passengers in a vehicle to hear the speech of a front seat occupant. Two spaced microphones in the front seat area pick up speech signals which are differentially amplified and filtered in a bandpass filter and at least one notch filter. The filter signals are reproduced through speakers in the area of the rear seat. Differential amplification of the microphone signals results in greatly reduced acoustic feedback from the speakers to the microphones. The communication system of the invention is highly integrated into other communication and audio systems in the vehicle.

Abstract: An automotive sound system achieves manufacturing flexibility by joining a common chassis which implements radio functions with additional boards that are specific to either a cassette, CD, or DAT mechanism which is to be joined with the radio as an integral unit. Each board is controlled by a microcontroller and the separate microcontrollers are connected by a shared bus.

Abstract: A voltage-controlled amplifier employs an operational amplifier with negative feedback for setting the gain. A voltage variable resistance such as a junction-field-effect transistor (JFET) is employed as part of a variable voltage divider for controlling the amplifier gain. Resistors in series and in parallel with the JFET determine minimum and maximum resistances corresponding to upper and lower limits for the amplifier gain. Thus, multiple channels of an amplifier can be provided with closely matched characteristics even using separate JFETs in each separate channel which have unmatched characteristics.

Abstract: An electrical connector includes terminals and receptacles mating at an angle relative to the horizontal force applied to couple them. Keying flanges mounted on a terminal housing slide along guide channels of a receptacle frame in a first direction, and are then directed along keying slots in a second direction, angularly related to the first direction, to mate the terminals and receptacles mounted in the receptacle frame. The connector is compact and may be assembled with application of a single coupling force in one direction. The angular disposition of terminals and receptacles provides improved resistance to uncoupling. A system of such electrical connectors is provided, including means for preventing cross-connection of unrelated circuits and components. Finally, a method for interconnecting electrical circuits and components with such electrical connectors is provided.

Abstract: A variable bandpass filter for filtering RF antenna signals to improve selectivity and reduce intermodulation distortion in an FM radio receiver includes a series resonant circuit which is modified to avoid blocking of AM signals. A bypass inductor is connected in parallel with the series resonant capacitor. The bypass inductor has a self-resonant frequency located between the AM and FM bands so that series resonant performance is maintained at FM frequencies and the bypassing function is exhibited at AM frequencies.

Abstract: A multichannel amplifier employs field-effect transistors to vary the gain of operational amplifiers in each respective channel. Gain matching of the respective channels is obtained by providing each channel with a respective DC bias voltage which compensates for differences in pinch-off voltage of the field-effect transistors. The invention permits the use of inexpensive, unmatched JFETs in the amplifier. Close gain tracking achieves very accurate stereo imaging in an audio system.

Abstract: An automotive sound system achieves manufacturing flexibility by joining a common chassis which implements radio functions with additional boards that are specific to either a cassette, CD, or DAT mechanism which is to be joined with the radio as an integral unit. Each board is controlled by a microcontroller and the separate microcontrollers are connected by a shared bus.

Abstract: The reception of FM broadcast signals having a selected high sound quality is determined according to criteria including a low noise level and the absence of interference. The high quality information is employed to terminate a scan tuning operation or to activate an ultrasonic noise filter to improve listening quality of the FM audio output. The absence of noise and interference is determined by examining a particular frequency range from the FM field intensity line generated by an intermediate frequency circuit.

Abstract: Systematic errors in manufacturing of position markers of an internal combustion engine position sensing system are corrected by a procedure which detects nonuniformities in the placement of the position markers using an engine coastdown without combustion in the cylinders. Since the coastdown comprises a smooth deceleration, any nonuniformities detected in the velocities calculated for individual firing intervals during the coastdown are a manifestation of nonuniformities in the position marker placement. These nonuniformities are used to calculate correction factors which are stored for use when calculating velocities during engine combustion.

Abstract: The stereo separation provided by a radio receiver is controlled in dependence on the radio frequency environment at the receiver antenna. The blend curve for determining stereo separation in dependence on the field intensity of a received signal is dynamically shifted to maintain the average magnitude of a blend control signal at a predetermined magnitude if the field intensity is above a threshold. Otherwise the blend control signal follows a lower limit blend curve of predetermined shape.

Abstract: A method and apparatus are provided for reliably detecting misfires in an internal combustion engine during actual driving conditions by monitoring fluctuations in engine speed between consecutive firing intervals. An average acceleration over a series of firing intervals is removed from an individual acceleration measurement corresponding to a particular firing interval to give an acceleration deviation which is then normalized to an expected torque to provide a power loss measurement. The power loss measurement indicates the occurrence of a misfire with a high signal-to-noise ratio. The information derived from misfire detection can be used to prevent destruction of a catalytic converter by unburned fuel mixtures and can be used to improve vehicle driveability by correcting for or indicating needed service for the vehicle. The misfire detection is implemented using existing sensors and processors and is adapted to be done on-board a vehicle in real time.

Abstract: A variable frequency RF passband filter is calibrated to maximize the sensitivity of a radio receiver using reference frequencies applied based on the clock operation of a digital processor within the receiver. The reference frequency passing through the variable passband filter is mixed to the intermediate frequency of the receiver and its level is detected. A frequency counter verifies that a measureable reference frequency signal has in fact been mixed to the intermediate frequency in order to avoid errors. The correct control voltage signal for the variable passband filter corresponding to each receiver frequency can thus be conveniently and inexpensively determined and stored for use during normal operation of the receiver.

Abstract: A method and apparatus are provided for reliably detecting misfires in an internal combustion engine during actual driving conditions by monitoring fluctuations in engine speed between consecutive firing intervals. An average acceleration over a series of firing intervals is removed from an individual acceleration measurement corresponding to a particular firing interval to give an acceleration deviation which is then normalized to an expected torque to provide a power loss measurement. The power loss measurement indicates the occurrence of a misfire with a high signal-to-noise ratio. The information derived from misfire detection can be used to prevent destruction of a catalytic converter by unburned fuel mixtures and can be used to improve vehicle driveability by correcting for or indicating needed service for the vehicle. The misfire detection is implemented using existing sensors and processors and is adapted to be done on-board a vehicle in real time.

Abstract: An FM broadcast receiver includes apparatus for measuring signal quality. Signal-to-noise ratio in the received signal is determined by isolating a noise component of the received audio signal, multiplying the isolated noise component by a gain determined by received field intensity, and comparing peak amplified noise against a reference. The derived signal-to-noise ratio can be employed to stop an automatic scan tuning operation or can be employed to provide a display of received signal-to-noise ratio.

Abstract: An automotive audio system is provided such that system controls, either pushbutton keypad or rotary switches, connect to an external interrupt pin of a microcontroller capable of restarting the microcontroller from its halt or power-down state. A control activity results in the microcontroller waking up from its halt state, monitoring the system control, and recording system parameter changes in a keep-alive memory. For example, the volume of the system can be changed while the system main power and functions are off. In another embodiment, the microcontroller can be woken up in order to display time-of-day information while both the audio system and the automobile are turned off. After displaying the information or changing the system parameter, the microcontroller returns to its halt state in order to conserve battery power. When the audio system is fully turned on, the most recent parameter setting that was recorded is used to initialize the system.

Abstract: An automotive electrical system including a wiring harness incorporates a dedicated test line passing through critical connectors and components for allowing detection and isolation of improperly connected connectors. The dedicated test line can feed through expansion connectors, termination connectors, and junction blocks. A respective impedance is connected between the dedicated test line and ground at each respective connector. Connector fault detection and isolation is achieved by measuring the total impedance presented at the beginning of the test line. The measured impedance uniquely identifies the locations of any improperly connected connectors.