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US 7,680,224 B2Granted
Apparatus and method for automatic frequency correction for a receiver system
AssigneeSilicon Laboratories Inc.
InventorsAndras Hegyi, Peter Onody
Life of this patent
Estimating the term…
Abstract
A system and method is shown for automatic frequency correction in a receiver, where the number of clock cycles in a baseband data signal, such as an I or Q channel of the receiver or an XOR of the I and Q channels, for a “1” state and a “0” state of a received data signal are each determined and the difference between the two is used to calculate a subsequent frequency offset correction value. The subsequent frequency offset correction value is added to a current offset correction value to obtain an actual offset correction value. The actual offset correction value is then used to adjust the frequency of the receiver clock.
Claims14
An automatic frequency control circuit for a receiver circuit, the circuit comprising:
- a first time measurement timer having a clock input configured to receive a reference clock signal, an enable input configured to receive a received data signal, and a first ready output configured to become active when the first time measurement timer counts a predetermined number of reference clock cycles when the first time measurement timer is enabled, where the first time measurement timer is enabled responsive to a first logic state of the received data signal;
- a second time measurement timer having a clock input configured to receive the reference clock signal, an enable input configured to receive the received data signal, and a second ready output configured to become active when the second time measurement timer counts the predetermined number of reference clock cycles when the second time measurement timer is enabled, where the second time measurement timer is enabled responsive to a second logic state of the received data signal;
- a first counter having a clock input configured to receive a baseband data signal of the receiver, an enable input configured to receive the received data signal, a stop input coupled to the first ready output of the first time measurement timer, and an output for a count value of the first counter, where the first counter is enabled responsive to the first logic state of the received data signal;
- a second counter having a clock input configured to receive a baseband data signal of the receiver, an enable input configured to receive the received data signal, a stop input coupled to the second ready output of the second time measurement timer, and an output for a count value of the second counter, where the second counter is enabled responsive to the second logic state of the received data signal;
- a subtractor having a first input coupled to the output of the first counter and a second input coupled to the output of the second counter, and an output for a difference of the count values of the first and second counters;
- an AND logic gate having a first input coupled to the ready output of the first time measurement counter, a second input coupled to the ready output of the second time measurement counter, and an output;
- a first latch having an input, an enable input coupled to the output of the AND logic gate, and an output;
- a second latch having an input coupled to the output of the first latch, an enable input configured to receive a control signal, and an output;
- and
- an adder having a first input coupled to the output of the subtractor, a second input coupled to the output of the second latch, and an output coupled to the input of the first latch.
7 more elements
A method for automatic frequency correction in a receiver, the method comprising the steps of:
- recovering a received data signal from a baseband data signal;
- counting a predetermined number of reference clock cycles during a “1” state of the received data signal to measure a “1” time interval;
- counting the number of transitions in the baseband data signal during the “1” time interval to obtain a “1” count value;
- counting a predetermined number of reference clock cycles during a “0” state of the received data signal to measure a “0” time interval;
- counting the number of transitions in the baseband data signal during the “0” time interval to obtain a “0” count value;
- determining a difference between the “1” and “0” count values to obtain a difference value;
- adding the difference value to a current offset value to obtain an actual offset value;
- latching the actual offset value when “1” and “0” time intervals have been measured;
- outputting the actual offset value responsive to a control signal;
- adding the actual offset value to a stored frequency control value to obtain a corrected frequency control value;
- and
- controlling a frequency synthesizer for the receiver using the corrected frequency control value.
9 more elements
A method for automatic frequency correction in a receiver, the method comprising the steps of:
- recovering a received data signal from a baseband data signal;
- counting a predetermined number of reference clock cycles during a “1” state of the received data signal to measure a “1” time interval;
- counting the number of transitions in the baseband data signal during the “1” time interval to obtain a “1” count value;
- counting a predetermined number of reference clock cycles during a “0” state of the received data signal to measure a “0” time interval;
- counting the number of transitions in the baseband data signal during the “0” time interval to obtain a “0” count value;
- determining a difference between the “1” and “0” count values to obtain a difference value;
- adding the difference value to a current offset value to obtain an actual offset value;
- latching the actual offset value when “1” and “0” time intervals have been measured;
- and outputting the actual offset value responsive to a control signal;
- where the baseband data signal is one of an I baseband data signal channel of the receiver, a Q baseband data signal channel of the receiver, and an exclusive ORing of the I and Q baseband data signal channels.
7 more elements
A system for automatic frequency correction in a receiver, the system comprising:
- means for determining a number of transitions in a received baseband data signal for a “1” state of a received data signal, where the received data signal and is derived from the received baseband data signal;
- means for determining a number of transitions in the received baseband data signal for a “0” state of the received data signal;
- means for calculating a difference between the number of transitions in the received baseband data signal for a “1” state of the received data signal and the number of transitions in the received baseband data signal for a “0” state of the received data signal to obtain a subsequent frequency offset correction value;
- means for adding the subsequent frequency offset correction value to a current frequency offset correction value to obtain an actual frequency correction value;
- means for capturing and storing the actual frequency correction value;
- means for controlling the receiver clock frequency using the actual frequency correction value;
- means for detecting valid data in the received data signal;
- and
- means for initiating automatic frequency correction responsive to detecting valid data in the received data signal.
6 more elements
A system for automatic frequency correction in a receiver, the system comprising:
- means for determining a number of transitions in a received baseband data signal for a “1” state of a received data signal, where the received data signal and is derived from the received baseband data signal;
- means for determining a number of transitions in the received baseband data signal for a “0” state of the received data signal;
- means for calculating a difference between the number of transitions in the received baseband data signal for a “1” state of the received data signal and the number of transitions in the received baseband data signal for a “0” state of the received data signal to obtain a subsequent frequency offset correction value;
- means for adding the subsequent frequency offset correction value to a current frequency offset correction value to obtain an actual frequency correction value;
- means for capturing and storing the actual frequency correction value;
- means for controlling the receiver clock frequency using the actual frequency correction value;
- where the baseband data signal is one of an I baseband data signal channel of the receiver, a Q baseband data signal channel of the receiver, and an exclusive ORing of the I and Q baseband data signal channels.
4 more elements
Dependencies are inferred from the claim text.