Circuit and method for processing an automatic frequency control signal
AssigneeFreescale Semiconductor, Inc.
InventorsWilliam Eric Main, Danielle L. Coffing, Klaas Wortel
Life of this patent
Estimating the term…
Abstract
An integrated demodulator tuning circuit (10, 60) receives differential currents at input terminals (12, 46) and provides an AFC signal at an output terminal (48). The AFC current characteristic has a dead band (72) in the output current generated when the integrated demodulator tuning circuit (10, 60) operates under the condition where the difference between the currents supplied at the input terminals (12 and 46) is at or below a set threshold value. The set threshold value is determined by the relative sizes of the transistors (14, 16 and 20, 36, 38 and 40) that form the current mirrors connected to the input terminals (12, 46).
Claims21
An injection-locked demodulator circuit with Automatic Frequency Control (AFC), comprising:
- an injection-locked oscillator having a first input for receiving a modulated signal;
- a multiplier having a first input for receiving the modulated signal and a second input for receiving a signal generated by the injection-locked oscillator;
- a tuning circuit coupled to an output of the multiplier for receiving first and second input signals, the tuning circuit disabling the AFC until a difference in the first and second input signals reaches a threshold value, the tuning circuit comprising:
- first and second current mirrors coupled between a first input terminal that receives the first input signal and the output of the tuning circuit, the first current mirror receiving a first current and the second current mirror providing a first portion of an output current;
- third, fourth and fifth current mirrors coupled between a second input terminal that receives the second input signal and the output terminal of the tuning circuit, the third current mirror receiving a second current and the fifth current mirror providing a second portion of the output current, wherein the first and second input terminals receive a differential signal from the multiplier;
- and
- first and second transistors coupled from inputs of the respective second and fourth current mirrors to a first power supply conductor for preventing the second current mirror from providing the first portion of the output current and the fifth current mirror from providing the second portion of the output current;
- and
- a filter having an input coupled to an output of the tuning circuit and an output coupled to a second input of the injection-locked oscillator.
A circuit for providing an automatic frequency control signal having first and second input terminals coupled for receiving a differential current and an output terminal that supplies a current that is a function of a difference of the differential current, the circuit comprising:
- a first current path from the first input terminal to the output terminal comprising first and second current mirrors coupled between the first input terminal and the output terminal of the circuit, the first current mirror receiving a first current and the second current mirror providing a first portion of the output current;
- a second current path from the second input terminal to the output terminal, the second current path comprising third, fourth and fifth current mirrors coupled between the second input terminal and the output terminal of the circuit, the third current mirror receiving a second current and the fifth current mirror providing a second portion of the output current;
- and
- first and second switches coupled for receiving a signal that disables the respective first and second current paths from providing the current that is the function of the difference of the differential current.
A tuning circuit having first and second input terminals and generating an automated frequency control signal at an output terminal, comprising:
- first and second transistors that form a first current mirror and have first current conduction terminals commonly coupled to a first power supply conductor and control terminals commonly coupled to a second current conduction terminal of the first transistor and to the first input terminal;
- third and fourth transistors that form a second current mirror and have first current conduction terminals commonly coupled to a second power supply conductor and control terminals commonly coupled to a second conduction terminal of the third transistor and to a second current conduction terminal of the second transistor
- fifth and sixth transistors that form a third current mirror and have first current conduction terminals commonly coupled to the first power supply conductor and control terminals commonly coupled to a second current conduction terminal of the sixth transistor and to the second input terminal;
- seventh and eighth transistors that form a fourth current mirror and have first current conduction terminals commonly coupled to the second power supply conductor and control terminals commonly coupled to a second conduction terminal of the eighth transistor and to a second conduction terminal of the fifth transistor;
- and
- ninth and tenth transistors that form a fifth current mirror and have first current conduction terminals commonly coupled to the first power supply conductor and control terminals commonly coupled to a second conduction terminal of the tenth transistor and to a second conduction terminal of the seventh transistor, and the second conduction terminal of the ninth transistor being coupled to the output terminal of the tuning circuit.
A method for generating an Automatic Frequency Control (AFC) signal having a dead band region where the AFC signal is not responsive to a difference in first and second input signals, comprising:
- transferring a first signal received at a first input to an output through a first path;
- transferring a second signal received at a second input to the output through a second path for combining with the first signal in generating the AFC signal;
- and
- exceeding a threshold in the AFC before generating the dead band region by transferring the first and second signals to the output.
A method for generating an Automatic Frequency Control (AFC) signal based on a modulated signal, comprising:
- providing first and second input terminals for receiving a differential current;
- providing an output terminal that supplies an output current that is a function of a difference of the differential current;
- providing a first current path from the first input terminal to the output terminal;
- coupling first and second current mirrors between the first input terminal and the output terminal, the first current mirror receiving the first current and the second current mirror providing a first portion of the output current;
- providing a second current path from the second input terminal to the output terminal;
- coupling third, fourth and fifth current mirrors between the second input terminal and the output terminal, the third current mirror receiving the second current and the fifth current mirror providing a second portion of the output current;
- and
- selectively disabling the first and second current paths from providing the output current.
A method for generating an Automatic Frequency Control (AFC) signal in an injection-locked demodulator, comprising:
- providing the injection-locked demodulator with an unmodulated signal at the carrier frequency of the modulated signal;
- providing the injection-locked demodulator with a modulated signal;
- and
- providing a differential current at first and second inputs;
- coupling a plurality of current mirrors between the first and second inputs and an output terminal;
- combining first and second current portions from the plurality of current mirrors to form an output current;
- and
- selectively disabling the output current and thereby disabling the AFC signal in the presence of the modulated signal to prevent detuning the injection-locked demodulator.
A method of generating an Automatic Frequency Control (AFC) signal having a deadband region in a demodulator, comprising:
- transferring a first current signal received at a first input to an output through a first path;
- transferring a second current signal received at a second input to the output through a second path for combining with the first signal in generating the AFC signal;
- tuning the demodulator relative to a threshold value determined by relative sizes of transistors that form current mirrors in a tuning circuit of the demodulator;
- and
- maintaining the AFC signal in the dead band region until a difference in the first current signal and the second current signal exceeds the threshold value in either polarity upon which the AFC signal is serially passed to an AFC filter and an oscillator.
Dependencies are inferred from the claim text.