Data slicer reference generator for multiple burst data signals
View Patent ↗A slice level reference generator and method for performing improved data slicing operations when gaps are present in a data stream is disclosed that involves applying a nominal reference signal to the comparator the during signal gaps. In one embodiment, a receiver circuit includes a slice level detector and a comparator that operate in a conventional manner, and control circuitry that utilizes a signal detector and a switch to store a slice level reference signal generated by the slice level detector during a first signal burst, and to apply the stored reference signal to the comparator during signal gaps. In one embodiment a timer circuit is used to detect signal gaps. In another embodiment a predetermined fixed reference signal is applied to the comparator during signal gaps.
1. A receiver circuit for generating a digital output signal in response to a received analog signal, the analog signal being characterized by a first signal burst and a second signal burst separated by a signal gap, the receiver circuit comprising:
a slice level detector for generating a slice level reference signal in response to an amplitude of said analog signal;
a comparator having a first terminal connected to receive the analog signal, a second terminal, and means for generating said digital output signal on an output terminal; and
means for applying said slice level reference signal to said second input terminal of said comparator during said first and second signal bursts, and for applying a predetermined nominal reference signal to said second input terminal of said comparator during said signal gap.
2. The receiver circuit according to claim 1 , wherein said means comprises:
a switch having a first terminal connected to the second input terminal of the comparator, a second terminal, and a control terminal;
a nominal reference source for generating said predetermined nominal reference signal; and
means for controlling said switch to transmit said slice level reference signal from the slice level detector to said second input terminal of said comparator during said first and second signal bursts, and for controlling said switch to transmit said predetermined nominal reference signal from said nominal reference source to said second input terminal of said comparator during said signal gap.
3. The receiver circuit according to claim 2 , wherein said means for controlling comprises a timer circuit including a reset terminal connected to an output terminal of said comparator, a clock input terminal for receiving a clock signal, and an output terminal connected to a control terminal of the switch, wherein said timer circuit includes means for transmitting a control signal to said switch only when said digital output signal drops below the predetermined amplitude for a predetermined number of cycles of said clock signal, whereby said switch connects said second input terminal of the comparator to receive the nominal reference signal from the reference source.
4. The receiver circuit according to claim 3 ,
wherein said switch comprises a MOS transistor connected between the slice level detector and the second input terminal of the comparator, and
wherein the reference source comprises a capacitor having a first terminal connected to the second terminal of the comparator, and a second terminal connected to a fixed voltage source.
5. The receiver circuit according to claim 4 , wherein the slice level detector comprises means for generating a positive signal peak level signal and a negative signal peak level signal of said analog signal, and for generating said slice level reference signal by combining the positive and negative signal peak level signals.
6. The receiver circuit according to claim 2 ,
wherein the reference source comprises a reference voltage generator,
wherein said switch comprises a MOS transistor connected between the reference voltage generator and the second input terminal of the comparator.
7. The receiver circuit according to claim 6 , wherein the second input terminal of the comparator is connected to receive the slice level reference signal from the slice level detector.
8. The receiver circuit according to claim 7 , wherein the slice level detector comprises means for generating a positive signal peak level signal and a negative signal peak level signal of said analog signal, and for generating said slice level reference signal by combining the positive and negative signal peak level signals.
9. A receiver circuit for generating a digital output signal in response to a received analog signal, the analog signal being characterized by a first signal burst and a second signal burst separated by a signal gap, the receiver circuit comprising:
a slice level detector for generating a first slice level reference signal in response to an amplitude of said analog signal during said first data burst, and for generating a second slice level signal in response to an amplitude of said analog signal during said second data burst;
a comparator having a first terminal connected to receive the analog signal, a second terminal, and means for generating said digital output signal at a first level when said received analog signal is greater than a signal applied to said second terminal, and for generating said digital output signal at a second signal level when said received analog signal is less than the signal applied to said second terminal;
means for applying said first slice level reference signal to said second input terminal of said comparator during said first signal burst, for storing the first slice level reference signal and for applying said stored first slice level reference signal to said second input terminal of said comparator during said signal gap, and for applying said second slice level reference signal to said second input terminal of said comparator during said second signal burst.
10. The receiver circuit according to claim 9 , wherein said means comprises:
a switch having a first terminal connected to the second input terminal of the comparator, a second terminal connected to the slice level detector, and a control terminal;
means for controlling said switch to transmit said first and second slice level reference signals from the slice level detector to said second input terminal of said comparator during said first and second signal bursts, respectively, and for controlling said switch to isolate the second input terminal of the comparator from said slice level detector during said signal gap; and
a capacitor connected to said second input terminal of said comparator such that said capacitor stores said first slice level reference signal during said first data burst, and applies said stored first slice level reference signal to said second input terminal during said data gap.
11. The receiver circuit according to claim 10 , wherein said means for controlling comprises a timer circuit including a reset terminal connected to an output terminal of said comparator, a clock input terminal for receiving a clock signal, and an output terminal connected to a control terminal of the switch, wherein said timer circuit includes means for transmitting a control signal to the control terminal of said switch only when said digital output signal drops below the predetermined amplitude for a predetermined number of cycles of said clock signal.
12. The receiver circuit according to claim 11 , wherein the slice level detector comprises means for generating a positive signal peak level signal and a negative signal peak level signal of said analog signal, and for generating said slice level reference signal by combining the positive and negative signal peak level signals.
13. A method for generating a digital output signal in response to a received analog signal, the analog signal being characterized by a first signal burst and a second signal burst separated by a signal gap, the method comprising:
applying the analog signal to a first input terminal of a comparator;
generating a slice level reference signal in response to an amplitude of said analog signal;
applying said slice level reference signal to a second input terminal of the comparator during said first and second signal bursts, and
applying a predetermined nominal reference signal to said second input terminal of the comparator during said signal gap.
14. The method of claim 13 , wherein the slice level reference signal comprises controlling a switch connected between said second input terminal of said comparator and one of said slice level detector and a nominal reference source, wherein the predetermined nominal reference signal is generated by said nominal reference source.
15. The method of claim 14 , wherein controlling said switch comprises comparing said digital output signal with a clock signal, and transmitting a control signal to said switch only when said digital output signal drops below a predetermined amplitude for a predetermined amount number of cycles of said clock signal.
16. The method claim 15 ,
wherein applying said slice level reference signal comprises storing a first slice level reference signal generated during said first signal burst, and
wherein applying said predetermined nominal reference signal comprises applying said stored first slice level reference signal to said second input terminal of the comparator during said signal gap.
17. The method of claim 16 , wherein generating said slice level reference signal comprises generating a positive signal peak level signal and a negative signal peak level signal of said analog signal, and combining the positive and negative signal peak level signals.
18. The method of claim 14 , wherein applying said predetermined nominal reference signal comprises controlling a switch to pass said predetermined nominal reference signal from a reference voltage generator to said second input terminal of the comparator during said signal gap.