Abstract: A system provides for remote monitoring using asynchronous code division multiple access (CDMA) communication techniques between a base station and one or more transponders. Each transponder is attached or otherwise associated with an object or an environment to be monitored. Upon receipt of an interrogation signal, a transponder generates and transmits a coded transponder signal containing the monitored data. The coded transponder signal is generated using a spreading code. Each transponder is associated with a unique, mutually exclusive set of spreading codes. Each spreading code is based on a unique transponder address and the monitored data to be sent. A detector asynchronously monitors received signals for any of the available spreading codes. Once the detector detects a particular spreading code, the base station can identify the source transponder and extract the monitored data.

Abstract: A system provides for remote monitoring using asynchronous code division multiple access (CDMA) communication techniques between a base station and one or more transponders. Each transponder is attached or otherwise associated with an object or an environment to be monitored. Upon receipt of an interrogation signal, a transponder generates and transmits a coded transponder signal containing the monitored data. The coded transponder signal is generated using a spreading code. Each transponder is associated with a unique, mutually exclusive set of spreading codes. Each spreading code is based on a unique transponder address and the monitored data to be sent. A detector asynchronously monitors received signals for any of the available spreading codes. Once the detector detects a particular spreading code, the base station can identify the source transponder and extract the monitored data.

Abstract: A system provides for remote monitoring using asynchronous code division multiple access (CDMA) communication techniques between a base station and one or more transponders. Each transponder is attached or otherwise associated with an object or an environment to be monitored. Upon receipt of an interrogation signal, a transponder generates and transmits a coded transponder signal containing the monitored data. The coded transponder signal is generated using a spreading code. Each transponder is associated with a unique, mutually exclusive set of spreading codes. Each spreading code is based on a unique transponder address and the monitored data to be sent. A detector asynchronously monitors received signals for any of the available spreading codes. Once the detector detects a particular spreading code, the base station can identify the source transponder and extract the monitored data.

Abstract: A system and method provides for calibrating a corner frequency of a tunable filter coupled to a read channel of a data storage system to a desired frequency. A signal having a frequency equal to the target corner frequency is generated. A gain of the signal is adjusted to a gain threshold. The gain of the signal is then increased from the gain threshold by a pre-established amount, such as by 3 dB. The corner frequency of the signal is shifted until the gain of the signal is substantially equal to the gain threshold, at which point the corner frequency of the tunable filter is calibrated to the desired frequency. The signal generated is a peak-detectable signal. The corner frequency of a tunable filter may be a low or high corner frequency appropriate for filtering a data signal or a servo signal. The corner frequency calibration circuitry may be implemented in-situ the read channel circuitry of a data storage system.

Abstract: An apparatus and method for calibrating a cutoff frequency of a tunable filter, such as a tunable filter coupled to a read channel of a data storage system is disclosed. A calibration circuit includes a variable gain amplifier (VGA), an envelope detector, and a tunable filter coupled therebetween. A calibration signal having a preestablished frequency representing a specified cutoff frequency associated with the tunable filter is applied to the VGA. The gain of the amplifier is adjusted until an amplitude of an output signal provided by the filter is substantially equal to a first predetermined amplitude. A cutoff frequency of the filter is then adjusted until an amplitude of an output signal provided by the filter is substantially equal to a second predetermined amplitude, at which time the desired cutoff frequency of the tunable filter is precisely established. A single cutoff frequency or the low and high cutoff freqencies of a range of cutoff frequencies may be calibrated.

Abstract: A system and method are provided for calibrating a corner frequency of a tunable filter using an ADC code difference method. A method for calibrating a corner frequency of a tunable filter in a direct access storage device includes generating a signal having a frequency within a pass band of the tunable filter to be passed to the tunable filter. The gain of the signal is adjusted to a first threshold level. The corner frequency of the signal is shifted to a second threshold level, whereby the corner frequency of the tunable filter is calibrated at a desired frequency. A system for calibrating a corner frequency of a tunable filter in a direct access storage device includes calibrate control logic coupled to a tunable filter. A signal source generating a signal having a frequency within a pass band of the tunable filter to be passed to the tunable filter is coupled to the tunable filter by a variable gain amplifier. An analog-to-digital converter (ADC) is coupled to the tunable filter.

Abstract: An apparatus and method for estimating an amplitude of a readback signal obtained from a data storage medium and input to a gain modifying amplifier involves sensing an amplifier output signal in response to a readback signal applied to the amplifier. An amplifier control signal is produced which is representative of a difference between the amplifier output signal and a reference signal. A compensation signal associated with a temperature coefficient of amplifier gain is generated, and an estimate signal indicative of the amplitude of the readback signal is produced using the compensation signal. The estimate signal is representative of readback signal amplitude when the estimate signal has a magnitude equivalent to that of the difference signal and a polarity opposite that of the difference signal.

Abstract: A method for measuring an amplitude of a readback signal obtained from a data storage medium involves transmitting the readback signal to a gain modifying amplifier, such as a variable gain amplifier (VGA), preferably provided in the read channel. A voltage signal associated with a loop gain of the amplification circuitry is sensed and compared with a number of control voltage signals, each of the control voltage signals being associated with a corresponding digital word value. The digital word value associated with a control voltage signal that is equal to the sensed voltage signal represents the relative amplitude of the readback signal. Gain characterization circuitry may further be combined with readback signal amplitude measuring circuitry, preferably in-situ a read channel, to obtain the absolute amplitude of a readback signal.

Abstract: A method and system for calibrating analog integrated circuits. Initially, a single calibration circuit is formed integral with a group of analog integrated circuits. A control signal and a calibration signal are generated from the calibration circuit. Next, the control signal and the calibration signal are selectively coupled to an input of a particular analog integrated circuit among the group of analog integrated circuits. The particular analog integrated circuit is then selected for calibration via the control signal.

Abstract: Methods and apparatus are provided for detecting servo information in a direct access storage device. A plurality of data symbols are read from a disk to produce a readback signal. Each data symbol and each sequence of data symbols contains servo identification information. A correlation filter provides a matched filter function of an expected readback signal of the plurality of data symbols to produce a correlated readback signal. A threshold detector is coupled to the correlation filter for identifying a threshold signal representative of the data symbol. A data separator responsive to the threshold detector windows the threshold signal and provides clock and data signals. The data separator includes a digital variable frequency oscillator (VFO) which optimally centers incoming servo information from the disk in a timing window and provides standard clocked data for a servo processor. The threshold detector has a variable threshold voltage that is programmed using a trim digital-to-analog converter (DAC).