| Patent application number | Description | Published |
|---|
| 20090028576 | Frequency-Domain Equalization of the Fiber Optic Channel - Systems and methods for frequency-domain compensation in optical communication systems. In pre-equalization embodiments, the transmitter transforms the data stream into a frequency domain signal and applies a compensation filter before transforming it back into a pre-distorted time domain signal. As the pre-distorted time domain signal propagates through the optical channel, optical dispersion effects counter the pre-distortion, producing an equalized signal at the channel output. In post-equalization embodiments, the receiver transforms the received signal into a frequency domain signal and applies a compensation filter before transforming it back into an equalized time domain signal. Pre-equalization may prove less expensive due to the square-law characteristic of photodetectors employed by most receivers. | 01-29-2009 |
| 20090279893 | ANALOG FINITE IMPULSE RESPONSE FILTER - According to one embodiment of the invention, a programmable finite impulse response (FIR) filter is implemented with differential isolation circuits to isolate parasitic capacitance from attenuating an output signal at both a first and second differential output terminals of the FIR filter. The FIR includes a track and hold circuit and a summing circuit that provides operational advantages to the FIR filter. | 11-12-2009 |
| 20100052778 | Nth Order Tunable Low-Pass Continuous Time Filter for Fiber Optic Receivers - According to one embodiment of the invention, a circuit comprising a plurality of operational transconductance amplifiers (OTAS) is described. The first OTA has differential input and differential output. The second OTA also has differential input, where a first output of the first OTA is coupled to the first differential input of the second OTA, which is an inverting input. A second output of the first OTA is coupled to the second input of the second OTA, which is a non-inverting input. The first differential output being coupled to a first input of the first OTA and the second differential output being coupled to a second input of the first OTA for negative feedback and current biasing. | 03-04-2010 |
| 20100102888 | TIMING RECOVERY FOR PARTIAL-RESPONSE MAXIMUM LIKELIHOOD SEQUENCE DETECTOR - An embodiment of the present invention is a technique for timing recovery. A frequency acquisition loop locks a voltage controlled oscillator (VCO) clock of a multi-band VCO to a reference clock. The frequency acquisition loop generates first and second feedback clocks from the VCO clock. A data lock phase loop generates a driving signal corresponding to a phase error signal from interleaved partial response signal (PRS) samples based on the second feedback clock. The driving signal controls the multi-band VCO in a data phase lock mode. A lock detect controller detects a frequency lock condition in a frequency lock mode and a data lock condition in the data phase lock mode based on the first feedback clock and the reference clock. | 04-29-2010 |
| 20100209115 | Frequency-Domain Equalization of the Fiber Optic Channel - Systems and methods for frequency-domain compensation in optical communication systems. In pre-equalization embodiments, the transmitter transforms the data stream into a frequency domain signal and applies a compensation filter before transforming it back into a pre-distorted time domain signal. As the pre-distorted time domain signal propagates through the optical channel, optical dispersion effects counter the pre-distortion, producing an equalized signal at the channel output. In post-equalization embodiments, the receiver transforms the received signal into a frequency domain signal and applies a compensation filter before transforming it back into an equalized time domain signal. Pre-equalization may prove less expensive due to the square-law characteristic of photodetectors employed by most receivers. | 08-19-2010 |
| 20100271107 | ANALOG FINITE IMPULSE RESPONSE FILTER - According to one embodiment of the invention, a programmable finite impulse response (FIR) filter is implemented with differential isolation circuits to isolate parasitic capacitance from attenuating an output signal at both a first and second differential output terminals of the FIR filter. The FIR includes a summing circuit that provides operational advantages to the FIR filter. | 10-28-2010 |
| 20100281348 | CALIBRATION METHOD AND CIRCUIT FOR AN ADD-COMPARE-SELECT LOOP - One embodiment of the invention features a programmable gain stage in analog update circuitry to overcome the accuracy limitation of the circuit gain and the maintenance of small finite number of possible sequence estimates. | 11-04-2010 |
