1. A digital camera comprising:
a Central Processing Unit (CPU) that controls the digital camera after a start-up process is carried out;
a connection device connectable to a storage medium for storing information;
a monitoring circuit, including a register and a timer, that monitors a connection status of whether the storage medium is connected to or disconnected from the connection device; and
a communication device that enables said CPU to access a monitoring result stored in the register by the monitoring circuit when said CPU is turned ON in response to a user’s power-on instruction,
wherein said monitoring circuit monitors the connection status of the storage medium in response to a control signal at a predetermined time interval, which is determined by the timer, stores information of the disconnection in the register when the storage medium is disconnected from said connection device while said CPU is in the OFF state, and, until a user’s power-on instruction, maintains said CPU in the OFF state and maintains the register and the timer in the ON state,
wherein said communication device enables said CPU to acquire the information of the disconnection from the register by direct access to the register when said CPU is turned ON in response to the user’s power-on instruction, and
wherein said monitoring circuit continues monitoring the connection status of whether the storage medium is connected to or disconnected from the connection device, until the storage medium is disconnected from said connection device, and after the storage medium is disconnected from said connection device, said monitoring circuit stops monitoring the connection status of whether the storage medium is connected to or disconnected from the connection device and continues storing the information of the disconnection in the register to be acquired by direct access of the CPU when said CPU is turned ON.
2. The digital camera as claimed in claim 1, further comprising a time management device that manages time within the digital camera, and
wherein said monitoring circuit and said time management device are configured as a single device.
3. The digital camera as claimed in claim 1, further comprising a management information storage device that stores file management information from the storage medium, and
wherein when said CPU determines, based on the monitoring result stored in said register, that the storage medium has not been disconnected from the connection device, said CPU reads out the file management information from said management information storage device to carry out the start-up process, whereas when said CPU determines that the storage medium has been disconnected from the digital camera at least once, said CPU reads out the file management information from the storage medium to carry out the start-up process.
4. The digital camera as claimed in claim 1, wherein said CPU sets time intervals at which said monitoring circuit monitors the connection status of the storage medium, via said communication device.
5. The digital camera as claimed in claim 1, further comprising a determination device that determines time intervals at which said monitoring circuit monitors the connection status of the storage medium, based on the monitoring result stored in said register.
6. The digital camera as claimed in claim 1, further comprising a fixing device that fixes information stored in said register to information indicative of the storage medium being disconnected from the connecting device regardless of whether or not the storage medium is connected to or disconnected from the connecting device, when a predetermined condition is satisfied, and
wherein said CPU carries out the start-up process based on the fixed information.
7. The digital camera as claimed in claim 6, wherein the predetermined condition includes at least one of a condition that a voltage supplied to said monitoring circuit has become equal to or lower than a set voltage or a condition that a reset signal has been externally input to said monitoring circuit.
8. The digital camera as claimed in claim 6, wherein said register stores the information indicative of the storage medium being disconnected from the connecting device as the monitoring result.
9. The digital camera as claimed in claim 1, further comprising:
a first conversion device that converts a voltage from a first power supply, capable of supplying electric power to components of the digital camera, to a first voltage;
a second conversion device that converts a voltage from a second power supply, capable of supplying electric power to said monitoring circuit, including to said register, to a second voltage; and
a switching device that selectively switches between the first voltage and the second voltage to supply a selected one of the first voltage or the second voltage to said monitoring circuit, including said register included in said monitoring circuit.
10. The digital camera as claimed in claim 9, wherein said switching device carries out at least one of a control operation for supplying a higher one of the first voltage or the second voltage, or a control operation for preferentially supplying the first voltage.
11. The digital camera as claimed in claim 9, further comprising a charging device that causes the first power supply to charge the second power supply.
12. The digital camera as claimed in claim 9, further comprising a time management device that manages time within the digital camera, and
wherein said monitoring circuit, including said register, and said time management device are operated by common electric power supplied from one of the first power supply or the second power supply.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for crest factor reduction of a multi-carrier signal comprising a plurality of single-carrier signals, each single-carrier signal of the plurality of single-carrier signals having signal-specific spectral properties, the method comprising:
identifying a peak in the multi-carrier signal and a time of occurrence of the peak;
generating a plurality of cancellation pulses depending on the time of occurrence of the peak, wherein a particular cancellation pulse of the plurality of cancellation pulses is associated with a particular single-carrier signal of the plurality of single-carrier signals and wherein cancellation pulse-specific spectral properties of the particular cancellation pulse substantially match the signal-specific spectral properties of the associated particular single-carrier signal;
combining the plurality of cancellation pulses to form a combined cancellation pulse;
applying the combined cancellation pulse to the multi-carrier signal to reduce the peak;
weighting the plurality of cancellation pulses with a plurality of weighting factors prior to combining the plurality of cancellation pulses; and
adjusting the weighting factors depending on a plurality of variable distortion thresholds for the plurality of single-carrier signals, each variable distortion threshold of the plurality of variable distortion thresholds defining an allowable range of operation for one of the plurality of single-carrier signals with respect to distortions.
2. The method of claim 1, wherein the adjusting comprises an optimization of the weighting factors based on evaluating and minimizing a crest factor reduction distortion of the multi-carrier signal caused by the crest factor reduction.
3. The method of claim 2, wherein the optimization is a convex optimisation.
4. The method of claim 1, wherein two or more successive ones of the combined cancellation pulses are generated by two or more different pulse generators of a crest factor reduction circuit performing the method for crest factor reduction.
5. The method of claim 1, wherein the identifying the peak also produces at least one of a value of a peak amplitude of the peak and a peak phase of the peak, and wherein the generating the plurality of cancellation pulses depends on at least one of the peak amplitude.
6. A crest factor reduction circuit for a multi-carrier signal comprising a plurality of single-carrier signals, each single-carrier signal of the plurality of single-carrier signals having signal-specific spectral properties, the crest factor reduction circuit comprising:
a peak detector for identifying a peak in the multi-carrier signal and a time of occurrence of the peak;
a multi-pulse generator for generating a plurality of cancellation pulses depending on the time of occurrence, the multi-pulse generator comprising a plurality of pulse generators and a cancellation pulse combiner connected to a pulse output of the plurality of pulse generators and adapted to form a combined cancellation pulse, wherein a particular pulse generator of the plurality of pulse generators is associated with a particular single-carrier signal of the plurality of single-carrier signals and wherein cancellation pulse-specific spectral properties of a cancellation pulse generated by the particular pulse generator substantially match the signal-specific spectral properties of the associated particular single-carrier signal;
a pulse injector for injecting the combined cancellation pulse to the multi-carrier signal;
a weighting unit interposed between the plurality of pulse generators and the cancellation pulse combiner, the weighting unit being adapted to weight the plurality of cancellation pulses with a plurality of weighing factors prior to the combining the plurality of cancellation pulses; and
an adaptive adjuster adapted to adjust the weighting factors depending on a plurality of variable distortion thresholds for the plurality of single-carrier signals.
7. The crest factor reduction circuit of claim 6, wherein the adaptive adjuster is adapted to perform an optimization of the weighting factors based on evaluating and minimizing a crest factor reduction distortion of the multi-carrier signal caused by the crest factor reduction.
8. The crest factor reduction circuit of claim 6, comprising a plurality of the multi-pulse generators, the plurality of the multi-pulse generators being adapted to generate a plurality of combined cancellation pulses in a staggered succession.
9. The crest factor reduction circuit of claim 6, wherein the identifying the peak detector produces at least one of a value of a peak amplitude of the peak and a peak phase of the peak, and wherein the multi-pulse generator is adapted to generate the plurality of cancellation pulses depending on at least one of the peak amplitude and the peak phase.
10. A mobile communications transmitter comprising a crest factor reduction circuit according to claim 6.
11. A mobile communications base station comprising a crest factor reduction circuit according to claim 6.
12. A computer program product comprising a non-transitory computer-usable medium having control logic stored therein for causing processor to execute a method for crest factor reduction of a multi-carrier signal comprising a plurality of single-carrier signals, each single-carrier signal of the plurality of single-carrier signals having signal-specific spectral properties, the method comprising:
identifying a peak in the multi-carrier signal and a time of occurrence of the peak;
generating a plurality of cancellation pulses depending on the time of occurrence of the peak, wherein a particular cancellation pulse of the plurality of cancellation pulses is associated with a particular single-carrier signal of the plurality of single-carrier signals and wherein cancellation pulse-specific spectral properties of the particular cancellation pulse substantially match the signal-specific spectral properties of the associated particular single-carrier signal;
combining the plurality of cancellation pulses to form a combined cancellation pulse;
applying the combined cancellation pulse to the multi-carrier signal to reduce the peak; and
weighting the plurality of cancellation pulses with a plurality of weighting factors prior to combining the plurality of cancellation pulses; and
adjusting the weighting factors depending on a plurality of variable distortion thresholds for the plurality of single-carrier signals, each variable distortion threshold of the plurality of variable distortion thresholds defining an allowable range of operation for one of the plurality of single-carrier signals with respect to distortions.
13. A computer program product comprising a non-transitory computer-usable medium having control logic stored therein for causing a computer to manufacture a crest factor reduction circuit comprising:
a peak detector for identifying a peak in the multi-carrier signal and a time of occurrence of the peak;
a multi-pulse generator for generating a plurality of cancellation pulses depending on the time of occurrence, the multi-pulse generator comprising a plurality of pulse generators and a cancellation pulse combiner connected to a pulse output of the plurality of pulse generators and adapted to form a combined cancellation pulse, wherein a particular pulse generator of the plurality of pulse generators is associated with a particular single-carrier signal of the plurality of single-carrier signals and wherein cancellation pulse-specific spectral properties of a cancellation pulse generated by the particular pulse generator substantially match the signal-specific spectral properties of the associated particular single-carrier signal;
a pulse injector for injecting the combined cancellation pulse to the multi-carrier signal;
a weighting unit interposed between the plurality of pulse generators and the cancellation pulse combiner, the weighting unit being adapted to weight the plurality of cancellation pulses with a plurality of weighing factors prior to the combining the plurality of cancellation pulses; and
an adaptive adjuster adapted to adjust the weighting factors depending on a plurality of variable distortion thresholds for the plurality of single-carrier signals.