Method and Apparatus for Detecting RF Field Strength
AssigneeRFMicron, Inc.
InventorsShahriar Rokhsaz, Edwin de Angel
Life of this patent
Estimating the term…
Abstract
A method and apparatus for detecting RF field strength. A field strength reference generator develops a field strength reference current as a function of a field strength of a received RF signal; and a field strength quantizer develops a digital field-strength value indicative of the field strength reference current. In one embodiment, detected field strength is used to dynamically vary the impedance of a tank circuit whereby, over time, induced current is maximized.
Claims30
In an RF communication system in which an external transmitter electromagnetically couples a signal of predetermined frequency, fC, to a receiver separated by an air gap from the transmitter, a method for dynamically maximizing a received power transfer by adjusting a tuning circuit of the receiver, the tuning circuit comprising an antenna and a capacitor, a capacitance of which can be varied in a selected one of first and second directions, the method comprising the steps of:
- (1) selecting one of said first and second directions;
- (2) capturing a first current response of the tuning circuit to the signal transmitted by the transmitter;
- (3) varying the capacitor in said selected first or second direction;
- (4) comparing the captured first response to a second current response of the tuning circuit to the signal currently transmitted by the transmitter;
- (5) if the comparison made in step 4 indicates that the second current response is weaker than the captured first response, selecting the other of said directions;
- and (6) returning to step 2.
A power detector for use in an RF receiver, the detector comprising:
- a power reference generator adapted to develop a power reference current as a function of a power transferred via a received RF signal;
- and
- a power quantizer, responsive to the power reference current, adapted to develop a digital field power value indicative of the power reference current.
A power detector for use in an RF receiver, the detector comprising:
- a power reference generator adapted to develop a power reference voltage as a function of a power transferred via a received RF signal;
- and
- a power quantizer, responsive to said power reference voltage, adapted to develop a digital field power value indicative of said power reference voltage.
A field strength quantizing detector for use in an RF system, the detector comprising:
- a regulator circuit adapted to conduct a first current proportional to the field strength of a received electromagnetically coupled RF signal;
- a current source circuit adapted to develop a field strength reference current in response to a digital input;
- a reference circuit coupled to said regulator and to said current source and adapted to develop a mirrored current as a function of said first current and said field strength reference current;
- and
- a control circuit adapted to:
- capture said mirrored current;
- compare said captured mirrored current against a predetermined threshold value;
- increase said field strength reference current in response to an indication that said field strength current is insufficient;
- and
- cease operation of said control circuit in response to an indication that said field strength reference current is sufficient.
In an RF system comprising a regulator, a current source, a reference circuit, and a control circuit, a method of quantizing field strength comprising the steps of:
- (1) conducting a first current proportional to the field strength of a received electromagnetically coupled RF signal;
- (2) developing a field strength reference current in response to a digital input;
- (3) developing a mirrored current as a function of said first current and said field strength reference current;
- (4) capturing said mirror current;
- (5) comparing said captured mirrored current against a predetermined threshold value;
- (6) changing said field strength reference current in response to an indication that said field strength current is insufficient;
- and
- (7) ceasing operation in response to an indication that said field strength reference current is sufficient.
A field strength quantizing detector for use in an RF system, the detector comprising:
- a regulator circuit adapted to conduct a first current proportional to the field strength of a received electromagnetically coupled RF signal;
- a current source circuit adapted to:
- develop a field strength reference current in response to a digital input;
- and
- develop a reference voltage on a sensing node in response to said field strength current;
- a reference circuit coupled to said regulator and to said current source and adapted to:
- develop a mirrored current as a function of said first current and said field strength reference current;
- and
- further develop said reference voltage on said sensing node in response to said mirrored current;
- and
- a control circuit adapted to:
- capture said reference voltage;
- compare said captured reference voltage against a predetermined threshold value;
- change said field strength reference current and further develop said reference voltage in response to an indication that said field strength current is insufficient;
- and
- cease operation of said control circuit in response to an indication that said field strength reference current and said reference voltage are sufficient.
In an RF system comprising a regulator, a current source, a reference circuit, and a control circuit, a method of quantizing field strength comprising the steps of:
- (1) conducting a first current proportional to the field strength of a received electromagnetically coupled RF signal;
- (2) developing:
- a field strength reference current in response to a digital input;
- and
- a reference voltage on a sensing node in response to said field strength current;
- (3) developing:
- a mirrored current as a function of said first current and said field strength reference current;
- and
- further developing said reference voltage on said sensing node in response to said mirrored current;
- (4) capturing said reference voltage;
- (5) comparing said captured reference voltage against a predetermined threshold value;
- (6) changing said field strength reference current and further developing said reference voltage in response to an indication that said field strength current is insufficient;
- and
- (7) ceasing operation in response to an indication that said field strength reference current and said reference voltage are sufficient.
A maximum current detection circuit in an RF system comprising:
- a current shunt circuit adapted to conduct a first current proportional to a received signal;
- a current mirror circuit coupled to said current shunt circuit and adapted to:
- conduct a second current that is proportional to said first current;
- and
- produce a reference voltage that is proportional to said second current;
- an analog-to-digital converter (“ADC”) coupled to said current mirror circuit and adapted to:
- generate a first digital value if said reference voltage is below a first voltage value;
- generate a second digital value if said reference voltage is above a first voltage value;
- and
- output an ADC value that is a selected one of said first digital value and second digital value;
- a digitally controlled current source (“DCCS”) coupled to said current mirror and said ADC and adapted to modify said reference voltage in response to receiving a DCCS code;
- and
- a digital logic block coupled to said ADC and said DCCS and adapted to:
- sweep said DCCS code from a first value to a second value;
- and
- save a first copy of said DCCS code corresponding to the first instance of ADC value indicating said reference voltage is above said first voltage value.
A tuning circuit for dynamically varying the impendence of a tank circuit comprising an inductor and a capacitor, the capacitance of which can be varied in a selected one of first and second directions, the tuning circuit comprising:
- a voltage regulator coupled to said tank circuit adapted to maintain a constant voltage, said voltage regulator further comprising a current shunt circuit adapted to conduct a first current proportional to a received signal;
- a current mirror circuit coupled to said current shunt circuit and adapted to:
- conduct a second current that is proportional to said first current;
- and
- produce a reference voltage that is proportional to said second current;
- an analog-to-digital converter (“ADC”) coupled to said current mirror circuit and adapted to:
- generate a first digital value if said reference voltage is below a first voltage value;
- generate a second digital value if said reference voltage is above said first voltage value;
- and
- output an ADC value that is a selected one of said first digital value and second digital value;
- a digitally controlled current source (“DCCS”) coupled to said current mirror and said ADC and adapted to modify said reference voltage in response to receiving a DCCS code;
- and
- a digital logic block coupled to said voltage regulator and said tank circuit and adapted to:
- save a first copy of said DAC code corresponding to the first instance of ADC value indicating said reference voltage is above said first voltage value;
- sweep said DCCS code from a first selected value to a second selected value;
- determine a polarity of the change in a previous value of said DCCS code and current value of said DCCS code;
- select one of said first and second directions in response said polarity;
- and
- selectively vary the capacitance of said capacitor in said selected direction.
A power detector for use in an RF receiver, the detector comprising:
- a power reference generator adapted to develop a power reference signal as a function of a power transferred via a received RF signal;
- and
- a power quantizer, responsive to said power reference signal, adapted to develop a digital field power value indicative of said power reference signal.
Dependencies are inferred from the claim text.