Impinj, Inc.

Cypress Semiconductor Corporation

Jay A Kuhn

John D Hyde

Theron Stanford

Christopher J Diorio

Ronald A Oliver

Harley K Heinrich

Charles J T Peach

Shailendra Srinivas

Amita Patil

Alberto Pesavento

Charles Peach

Robert M Glidden

Jaskarn Johal

Andrew Edward Horch

Ronald Lee Koepp

Jonathon C Stiff

Ronald E Paulsen

Dennis Kiyoshi Hara

An RFID IC may operate at a relatively low clock frequency while impedance matching to an antenna is being tuned to increase the amount of power that the IC can extract from an incident RF wave. A tuning circuit tunes the impedance matching by adjusting a variable impedance coupling the IC and the antenna. The IC may power-up with a low clock frequency or reduce its current clock frequency to a lower clock frequency prior to tuning or during the tuning process, and may increase its clock frequency upon completion of tuning or during the tuning process.

RFID tag clock frequency reduction during tuning

Embodiments are directed to rectifiers using a single bias current or bias current path to bias multiple rectifying elements. A rectifier that has multiple rectifier stages coupled together serially includes a bias current path coupled to each of the rectifier stages. Thee bias current path is configured to simultaneously bias rectifying elements in each of the rectifier stages by using a bias current to bias a first rectifying element and reusing the bias current to bias other rectifying elements.

RFID tag rectifiers with bias current reuse

Backflow in rectifiers may be reduced via biasing. Upon determining that backflow within a rectifier is likely, one or more rectifying elements in the rectifier may be debiased, via analog or digital means. The debiased rectifying elements become less conductive or nonconductive, thereby reducing or preventing backflow. The determination of backflow likelihood may be performed based on a signal to be backscattered or the amplitude-modulated envelope of an incident RF wave, and may be digital or analog in nature.

Rectifier backflow reduction via biasing

Embodiments are directed to rectifiers using a single bias current or bias current path to bias multiple rectifying elements. A rectifier that has multiple rectifier stages coupled together serially includes a bias current path coupled to each of the rectifier stages. The bias current path is configured to simultaneously bias rectifying elements in each of the rectifier stages by using a bias current to bias a first rectifying element and reusing the bias current to bias other rectifying elements.

Embodiments are directed to mitigating power-based impedance changes in Radio Frequency Identification (RFID) tags. The intrinsic impedance of components in an RFID tag front-end may change as incident RF power on the tag changes, causing the input impedance of the front-end to change and altering the RF properties of the RFID tag. A number of approaches can be used to mitigate input impedance variations due to power variations. One approach involves adjusting the operating point of one or more components in the RFID tag front-end to change their intrinsic impedances so as to counteract or mitigate the RF-power-based input impedance variation.

Impedance-change mitigation in RFID tags

An RFID tag tuning circuit may be capable of adjusting the impedance matching between an RFID integrated circuit (IC) and an antenna on an RFID tag to increase the amount of power that the IC can extract from an incident RF wave. The tuning circuit switches a variable impedance coupling the antenna and the IC between several different impedance settings, where each impedance setting differs from an adjacent impedance setting by a respective impedance step size and at least one impedance step size has a different value than another impedance step size. The tuning circuit may switch the variable impedance by incrementing through a counter, decrementing through the counter, or performing some search algorithm. The tuning circuit may also initialize the variable impedance based on a default impedance setting or a random impedance setting derived from a random counter.

Self-tuning of RFID tags using nonuniform impedance steps

Data stored in nonvolatile memory on a Radio Frequency Identification (RFID) tag integrated circuit may have a 'margin' associated with how strongly the data is written to the memory. Upon receiving a wireless margin read command, the RFID IC determines whether the margin for one of more data values stored in memory exceeds a margin threshold. The IC may determine the margin by applying bias voltages or currents to the memory cells storing the data values. If the determined margin does not exceed the margin threshold, the IC may respond with an error code.

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Seattle, WA, United States of America

Jay A Kuhn