A reproduced signal processing circuit includes a variable gain amplifier to which a signal read from a medium by a reproducing head is inputted; an analog-to-digital converter for converting a signal outputted from the variable gain amplifier into a digital signal; and a variable frequency oscillator for supplying an operation clock signal to the analog-to-digital converter. A reproduced signal processing method includes the steps of operating a first control loop for controlling the variable gain amplifier; operating at least either one of a second control loop and a third control loop, the second control loop controlling the variable frequency oscillator, the third control loop controlling the variable frequency oscillator; filtering by analog filter means the read signal inputted to the variable gain amplifier; operating at least one of first, second, and third noise detecting operations, the first noise detecting operation detecting presence or absence of a noise by comparing an amplitude of the output signal from the variable gain amplifier with a predetermined threshold value, the second noise detecting operation detecting a noise during an operation period of the second control loop, the third noise detecting operation detecting a noise during an operation period of the third control loop; and changing the range of cutoff frequency of the analog filter means in accordance with a result from at least one of the first, second, and third noise detecting operations, thereby controlling at least one of the first, second, and third control loops.
A method for analog/digital conversion of a radiocommunication signal using an analog analog/digital converter preceded by variable gain amplifier, wherein the frequency band of the converted signal contains at least one useful channel, comprises steps for controlling the value of the gain of the amplifier in such a way that the power in the frequency band of the converted signal is less than a limit saturation value of the analog/digital converter. However, the power in the useful channel is substantially equal to a mean power level having a first predetermined value in the case of static propagation in the useful channel or a second predetermined value, different from said first predetermined value, in the case of dynamic propagation in the useful channel.
A receiver circuit contains first and second inputs for feeding in first and second input signals, and an output generating an output signal dependent on the input signals. A detector circuit has a first and second signal detectors connected to the first and second inputs, respectively. The signal detectors compare amplitudes of the input signals in each case with a detection threshold and in each case provide a detector output signal. The signal detectors each have a control input for setting the detection threshold, and the control input of the first signal detector is coupled to an output of the second signal detector and the control input of the second signal detector is coupled to an output of the first signal detector. A signal processing circuit receives the detector output signals and generates the output signal according to the detector output signals.
A method for providing a digital current signal from an analog armature current signal of a motor. The method includes subjecting the analog current signal to an analog-to-digital conversion to produce a first digital current signal having current ripples for each current ripple of the analog current signal. During start-up and run-down motor operation phases, the analog current signal is sampled at a sampling rate which is greater than an expected rate of the current ripples of the analog current signal to produce a second digital current signal having current ripples for each current ripple of the analog current signal during the start-up and run-down motor operation phases. The current ripples of the first and second digital current signals are then compared. The current ripples of the second digital current signal which are in non-conformance with the current ripples of the first digital current signal are evaluated.
A magnetically recorded data reproduction apparatus that reproduces magnetically recorded data using a magnetoresistive head and method thereof. The recorded data are reproduced by a magnetoresistive head and supplied to a reproduction amplifier. A signal from an AGC amplifier is supplied to an A/D converter and a digital PLL circuit. A digitized signal is then supplied to, for example, a Viterbi decoder 13 and the decoded signal is obtained at an output terminal 14. Thus, the effect of noise due to the so-called thermal asperity (TA noise) is removed, thereby preventing increases in the error rate of the reproduction signals due to the effect of TA noise and the occurrence of problems in equipment.
A preamplifier for correcting for thermal asperity transients in disk drives using magneto resistive read heads. The preamplifier has an input gain stage receiving a signal from the read head and an output buffer outputting a reader output to a read channel that is filtered of thermal asperity transients by a high pass filter positioned between the input gain stage and the output buffer. The high pass filter is voltage controlled based on an input control signal from a filter controller. The filter controller uses a low pass filter functioning as a peak detector to detect peaks in either the input or output voltage of the high pass filter. The low pass filter output is applied to a non-linear function generator generating the control signal for the high pass filter based on an increasing function of the absolute value of the low pass filter output.
