Techniques are described for tuning a resonant circuit using differential switchable capacitors. For example, embodiments can operate in context of a power amplifier with a tunable resonant output network. To tune the network, multiple differential switchable capacitors are provided in parallel. Each differential switchable capacitor can include a pair of capacitors, each coupled between a respective internal node and a respective differential terminal; and the internal nodes are selectively coupled or decoupled using a respective electronic switch (e.g., transistor). Switching on one of the differential switchable capacitors forms a capacitive channel having an associated capacitance. Each differential switchable capacitor can also include a switch network to selectively pull the internal nodes to a high or low voltage reference according to the selected operating mode.

Techniques are described for tuning a resonant circuit using differential switchable capacitors. For example, embodiments can operate in context of a power amplifier with a tunable resonant output network. To tune the network, multiple differential switchable capacitors are provided in parallel. Each differential switchable capacitor can include a pair of capacitors, each coupled between a respective internal node and a respective differential terminal; and the internal nodes are selectively coupled or decoupled using a respective electronic switch (e.g., transistor). Switching on one of the differential switchable capacitors forms a capacitive channel having an associated capacitance. Each differential switchable capacitor can also include a switch network to selectively pull the internal nodes to a high or low voltage reference according to the selected operating mode.

A radio frequency identification (RFID) tag includes an antenna structure operable to receive a radio frequency (RF) signal, an RF signal circuit operable to, when enabled, produce the RF signal, a sensing element operably coupled to the antenna structure, a memory, and a processing module. When in a calibration mode, the processing module adjusts the input impedance until a measured power level is substantially equal to the desired input power level, and generates a first digital value based on the amount of the adjustment a power difference between a measured first input power level and a desired power level, and stores the first digital value in the memory, where the first digital value is representative of a known condition. In a sense mode, the processing module adjusts the input impedance until a second measured power level is substantially equal to the desired input power level, and generates a second digital value based on the amount of the adjustment a power difference between a measured first input power level and a desired power level, and the desired power level, and stores the second digital value in the memory, where the second digital value is representative of an unknown condition.

A radio frequency identification (RFID) tag includes an antenna structure operable to receive a radio frequency (RF) signal, an RF signal circuit operable to, when enabled, produce the RF signal, a sensing element operably coupled to the antenna structure, a memory, and a processing module. When in a calibration mode, the processing module adjusts the input impedance until a measured power level is substantially equal to the desired input power level, and generates a first digital value based on the amount of the adjustment a power difference between a measured first input power level and a desired power level, and stores the first digital value in the memory, where the first digital value is representative of a known condition. In a sense mode, the processing module adjusts the input impedance until a second measured power level is substantially equal to the desired input power level, and generates a second digital value based on the amount of the adjustment a power difference between a measured first input power level and a desired power level, and the desired power level, and stores the second digital value in the memory, where the second digital value is representative of an unknown condition.

An apparatus and associated method are provided involving one or more registers configured to store a plurality of values including a first value corresponding with a first capacitance, and a second value corresponding with a second capacitance. Further included is a decoder configured to decode the values into corresponding capacitive settings. Also included is one or more capacitive elements in electrical communication with the decoder. Such one or more capacitive elements are configured to exhibit different capacitances, based on the capacitive settings. Also included is control circuitry in electrical communication with the decoder and the one or more registers. Such control circuitry is configured to control a transition of the capacitance of the one or more capacitive elements from the first capacitance to the second capacitance, by creating a plurality of additional values between the first value and the second value for being decoded by the decoder.

An apparatus and associated method are provided involving one or more registers configured to store a plurality of values including a first value corresponding with a first capacitance, and a second value corresponding with a second capacitance. Further included is a decoder configured to decode the values into corresponding capacitive settings. Also included is one or more capacitive elements in electrical communication with the decoder. Such one or more capacitive elements are configured to exhibit different capacitances, based on the capacitive settings. Also included is control circuitry in electrical communication with the decoder and the one or more registers. Such control circuitry is configured to control a transition of the capacitance of the one or more capacitive elements from the first capacitance to the second capacitance, by creating a plurality of additional values between the first value and the second value for being decoded by the decoder.

A wireless communication system includes a plurality of wireless sensors. A wireless sensor includes a radio frequency (RF) receiving circuit, and a sensing element, where the sensing element affects the resonant frequency of the RF receiving circuit. The wireless sensor further includes a processing module operable to determine a first value for an adjustable element of a plurality of elements for a known environmental condition, a second value for the adjustable element for an unknown environmental condition, a difference between the first and second values that corresponds to a change, and to generate a coded value representative of the change. The wireless communication system further includes one or more sensor computing devices coupled to the plurality of wireless sensors via a network. A sensor computing device includes a second processing module operable to receive the coded value and determine a sensed environmental condition based on the coded value.

A wireless communication system includes a plurality of wireless sensors. A wireless sensor includes a radio frequency (RF) receiving circuit, and a sensing element, where the sensing element affects the resonant frequency of the RF receiving circuit. The wireless sensor further includes a processing module operable to determine a first value for an adjustable element of a plurality of elements for a known environmental condition, a second value for the adjustable element for an unknown environmental condition, a difference between the first and second values that corresponds to a change, and to generate a coded value representative of the change. The wireless communication system further includes one or more sensor computing devices coupled to the plurality of wireless sensors via a network. A sensor computing device includes a second processing module operable to receive the coded value and determine a sensed environmental condition based on the coded value.

In accordance with an embodiment, a method of operating an RF system includes filtering a wideband RF signal using an adjustable center frequency bandpass filter to produce a filtered RF signal; amplifying the filtered RF signal to produce an amplified RF signal; and band stop filtering the amplified RF signal to produce a band stopped RF signal.

In accordance with an embodiment, a method of operating an RF system includes filtering a wideband RF signal using an adjustable center frequency bandpass filter to produce a filtered RF signal; amplifying the filtered RF signal to produce an amplified RF signal; and band stop filtering the amplified RF signal to produce a band stopped RF signal.