Abstract: Level-holding circuits 16, 17 sample and hold the output of quadrature detecting circuit 11 at adjoining apertures of eye patterns of demodulated multi-level QAM signal components and at the middle point of the adjoining apertures, respectively. Thus, location information on a phase plane of demodulated signal such as (I0, Q0), (I1, Q1), and (I1/2, Q1/2) are obtained. Frequency deviation detecting circuit 18 calculates the amplitude and the direction of the frequency deviation of regenerated carrier based on the location information. The output of frequency deviation detecting circuit 18 is added to phase error signal in synthesizing circuit 20. The result of addition is applied to VCO 15.

Abstract: In a cellular radio communication system, a downlink signal is multicast from a cental station and multiple base stations receive the multicast downlink signal via transmission links and respectively transmit the downlink signal on radio waves of same frequencies so that a cluster of adjoining areas is illuminated with the radio waves. A mobile station having a tapped-delay line equalizer receives signals from the base stations via multipath fading channels and equalizes the received signals. Interference between the transmitted signals is avoided by adjusting the relative propagation delay times of the transmission links so that the signals received by the mobile station occur within the tapped-delay line length of the equalizer.

Abstract: A frequency sweep circuit including: a pull-in verification wave generator for generating a verification signal for pull-in verification; a sweep wave generator for generating a frequency sweep signal; a first adder for adding an output from the pull-in verification wave generator and an output from the sweep wave generator; a correlation determining unit for receiving a phase difference signal representing a phase difference between a received carrier wave and a recovered carrier wave, and an output from the first adder, determining presence/absence of a correlation between the phase difference signal and the output, and outputting a control signal for controlling the sweep wave generator; a second adder for adding the output from the first adder to the phase difference signal; a digital-to-analog converter for receiving an output from the second adder; a loop filter for receiving an output from the digital-to-analog converter; and a voltage-controlled oscillator for receiving an output from the loop filter

Abstract: An idling speed control system is provided in an internal combustion engine which has an intake passage led to cylinders of the engine, a throttle valve installed in the intake passage, a bypass passage bypassing the throttle valve and an air-flow controller installed in the bypass passage for controlling the amount of air flowing in the bypass passage. The system comprises a first device which detects an engine torque which causes a fluctuation of rotation speed of the engine; and a second device which controls the air-flow controller in accordance with the detected engine torque.

Abstract: The fuel supply apparatus for a multiple-cylinder internal combustion engine is comprised of a fuel supply means through which a fuel amount is injected into each combustion chamber of the engine. The fuel amount is corrected by fuel supply amount correcting means in a controller of the fuel supply apparatus, in accordance with intake port pressure near the fuel supply means to maintain a proper fuel injection even in various intake pressure conditions. The intake port pressure is estimated by intake port pressure estimating mean in the controller to search a data map in the intake port pressure estimating means, in accordance with an engine speed, an opening degree of the throttle valve, and an crankangle at the fuel injection start time.

Abstract: A throttle is disposed in the intake port per cylinder. At idle, the throttles are closed. The pressure in the intake port per cylinder increases during the intake valve closed period due to flow admitted to the intake port downstream of the throttle until it recovers to ambient before the valve overlap period. The flow rate is controlled individually per cylinder such that it is higher during the intake valve closed period than it is during the intake valve opened period. This allows the increased valve overlap to be used without increasing the residual mass fraction in the cylinder. As a result, the stability engine operation at idle and part load range is improved.

Abstract: An intake air control system for a multi-cylinder reciprocating internal combustion engine. The intake system is comprised of a plurality of intake air passages which are respectively communicable with a plurality of combustion chambers each defined in each engine cylinder. A communication passage is contained with each intake air passage to establish communication between upstream and downstream sides of a throttle valve disposed in each intake air passageway. A bypass valve is disposed in each communication passage to control the flow amount of air flowing through the communication passage, in accordance with an output torque in each cylinder. The opening degree of the throttle valve is controlled in accordance with a target opening degree set in accordance with a depression angle of an accelerator pedal.

Abstract: Improvement is introduced in a conventional feedback control system for supplying an optimal air-fuel mixture to an internal combustion engine on the basis of a sensed component of exhaust gases thereof.

Abstract: A plasma jet ignition system with means for storing plasma ignition electric energy is disclosed wherein a switching means responsive to an ignition timing signal is connected between a charging terminal of a capacitor of the storing means. A plasma ignition electric charge stored in the capacitor is discharged when the switching means is operated in accordance with the ignition timing signal, thereby preventing an irregular discharge of the stored plasma ignition electric energy during each ignition timing interval.

Abstract: A fuel control system for an internal combustion engine includes an exhaust gas sensor from which feedback control signal is derived, a limiter for limiting the maximum and minimum voltages of the control signal and a triangular wave generator. The triangular wave has a constant amplitude peak of which the maximum value is slightly greater than the maximum voltage of the control signal and the minimum value is slightly below the minimum voltage of the control signal. A comparator is provided to produce an output at one of two binary levels depending upon whether the control signal is above or below the instantaneous value of the triangular wave. The output from the comparator is a train of pulses whose duty cycle ranges from predetermined minimum to maximum values which correspond respectively to the minimum open and closure times of air-fuel mixing control valves.

Abstract: A closed loop mixture control system for an internal combustion engine of a motor vehicle is provided with a voltage divider connected across the terminals of a single source of DC potential mounted on the vehicle to develop an offset voltage which is combined with the output of an exhaust gas sensor having a bipolar output characteristic. One of the polarities of the exhaust gas sensor output is compensated for by the offset voltage.

Abstract: A closed loop air-fuel ratio control system for an internal combustion engine is adapted to produce a control signal to be supplied to an air-fuel ratio regulator for regulating the air-fuel ratio of the air-fuel mixture to be supplied to the engine. The control signal is varied in amplitude in dependence on a concentration of a component in the exhaust gases upstream of a converter or reactor in the exhaust system. The control signal is composed of an integral component and a proportional component, the magnitude of the proportional component being dependent on that of the integral component.

Abstract: A closed-loop emission control system for an internal combustion engine having an exhaust composition sensor includes an averaging circuit for generating a signal representative of the average value of the sensed exhaust composition, and a balanced differential amplifier receptive of the average and instantaneous values of the sensed composition to generate an output indicating the difference therebetween. A DC bias is applied to the differential amplifier to fluctuate the difference signal above and below the DC bias level.

Abstract: A resistance circuit is connected to a differential signal generator to remove undesirable change of an air-fuel ratio control signal by compensating for temperature-dependent variation of internal resistance of an exhaust gas sensor.

Abstract: A closed-loop mixture control system for an internal combustion engine includes an exhaust composition detector to provide information on the air-fuel ratio of the mixture to be controlled and a circuit arrangement which clamps the system to a rich mixture ratio when the operating characteristic of the composition detector becomes abnormal due to either an open or short circuit condition.

Abstract: A clamping circuit is provided between a differential signal generator (such as a differential amplifier or a comparator) and a control signal generator (such as an integrator and/or a proportional amplifier) of an electronic closed loop control system for controlling an air-fuel ratio of the air-fuel mixture supplied to an internal combustion engine. The clamping circuit generates a signal whose maximum and maximum levels are symmetrical with respect to the half value of a potential of a d.c. power source provided for the clamping circuit.

Abstract: A feedback control system for controlling the air/fuel ratio of a combustible mixture fed to an internal combustion engine based on the output of an exhaust sensor includes an input circuit of a high input impedance, which serves as a prefatory circuit to a control signal producing circuit to match the high internal impedance of the sensor at low exhaust gas temperatures. The input circuit has an operational amplifier with its noninverting input terminal connected to the sensor and, optionally, two or more switchable resistors to adjust the input impedance.

Abstract: A feedback fuel pipe is provided, between a fuel reservoir and a portion of a main fuel pipe communicating with a discharging nozzle, for controlling the amount of fuel fed back to the fuel reservoir, which control is actually performed by valve means which is provided in the feedback fuel pipe and responsive to a signal representing at least one engine operating condition.

Abstract: A float bowl of an automotive engine carburetor is air-tightly covered by a diaphragm which is securely fixed to an electromagnetic transducer to be vibrated for controlling air pressure acting on the fuel being confined within the float bowl, whereby the amount of fuel delivered to the engine from the float bowl is controlled in dependence of the electrical signal applied.

Abstract: Various engine operating conditions are detected by a number of strategically located sensors which convert physically measurable quantities into proportional electrical signals. Such signals are firstly converted into analog signals representative of rectilinearly approximated relation between the input measurable quantities and the amount of fuel necessary for any given engine cycle and secondly converted into a series of command pulses by an exponential converter so that the width of the pulse closely indicates the ideal curvilinear relation between the input quantities and the required fuel quantity.