Transmit amplitude independent adaptive equalizer
View Patent ↗Transmit amplitude independent adaptive equalizers are provided that compensate for transmission losses in an input signal when the transmit signal amplitude is unknown. Several embodiments are provided, including a first embodiment having an equalizer core, a controllable-swing slicer and an amplitude control loop, a second embodiment having an equalizer core, a fixed-swing slicer and a control loop, a third embodiment having an equalizer core, a variable gain amplifier, and a variable gain amplifier control loop, and a fourth embodiment having an equalizer core, a fixed-swing slicer, a variable gain amplifier, and a variable gain amplifier control loop.
1. An equalizer comprising:
a variable gain amplifier coupled to an input signal from a transmission medium and a variable gain control signal that applies a variable gain to the input signal to generate an equalizer core input signal having a pre-determined signal swing;
an equalizer core coupled to the equalizer core input signal that applies a frequency dependant gain to the variable gain amplifier output to compensate for attenuation of the input signal caused by losses incurred in the transmission medium and generates a core output signal;
a fixed-swing slicer coupled to the core output signal that converts the core output signal to a digital output signal having the pre-determined signal swing; and
a variable gain amplifier control loop (VG-Loop) coupled to the core output signal and the digital output signal that compares the core output signal with the digital output signal and generates the variable gain control signal;
wherein the VG-Loop comprises;
a first filter coupled to the core output signal that filters the core output signal to a frequency range at which the input signal incurs minimal attenuation from the transmission medium and generates a first low-frequency signal; and
a second filter coupled to the digital output signal that filters the digital output signal to a frequency range at which the input signal incurs minimal attenuation from the transmission medium and generates a second low-frequency signal;
wherein the first and second low-frequency signals are compared by the VG-Loop.
2. An equalizer comprising:
a variable gain amplifier coupled to an input signal from a transmission medium and a variable gain control signal that applies a variable gain to the input signal to generate an equalizer core input signal having a pre-determined signal swing;
an equalizer core coupled to the equalizer core input signal that applies a frequency dependant gain to the variable gain amplifier output to compensate for attenuation of the input signal caused by losses incurred in the transmission medium and generates a core output signal;
a fixed-swing slicer coupled to the core output signal that converts the core output signal to a digital output signal having the pre-determined signal swing; and
a variable gain amplifier control loop (VG-Loop) coupled to the core output signal and the digital output signal that compares the core output signal with the digital output signal and generates the variable gain control signal;
wherein the VG-Loop comprises:
a first envelope detector that detects an energy level in the core output signal and generates a first energy-level output; and
a second envelope detector that detects an energy level in the digital output signal and generates a second energy-level output;
wherein the VG-Loop compares the first and second energy-level outputs.
3. An adaptive equalizer, comprising:
a first core circuit comprising a transfer function circuit and a first amplifier coupled to the output of the transfer function circuit, the first amplifier operable to provide a variable gain in response to a first amplifier control signal, the first core circuit operable to receive a first input signal and the first amplifier control signal and generate a first core output signal;
a second amplifier operable to receive a transmission medium input signal and a second amplifier control signal and apply a variable gain to the transmission medium input signal in response to the second amplifier control signal and generate an amplified transmission medium input signal;
a summing circuit operable to receive the amplified transmission medium input signal and the first core output signal to generate an equalizer core output signal;
a slicer circuit operable to receive the equalizer core output signal and convert the equalizer core output signal to a digital output signal;
a first gain control loop circuit coupled to the summing circuit output and the slicer output and operable to process the equalizer core output signal and the digital output signal to generate the first amplifier control signal; and
a second gain control loop circuit coupled to the summing circuit output and the slicer output and operable to process the equalizer core output signal and the digital output signal to generate the second amplifier control signal.
4. The adaptive equalizer of claim 3 , wherein the first input signal comprises the amplified transmission medium input signal.
5. The adaptive equalizer of claim 3 , wherein the first input signal comprises the transmission medium input signal.
6. The adaptive equalizer of claim 3 , wherein the first gain control loop circuit comprises a plurality of high-pass filters.
7. The adaptive equalizer of claim 3 , wherein the second gain control loop circuit comprises a plurality of low-pass filters.
8. The adaptive equalizer of claim 3 , wherein the slicer circuit comprises a fixed-swing slicer.