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.

Systems and methods are provided for implementing bandstop filters (e.g., RF/microwave bandstop filters) that can automatically tune to a frequency of an interfering signal. Embodiments of the present disclosure provide automatically tunable signal-tracking bandstop filters with a significant reduction in response time, complexity, size, weight, and cost when compared to conventional devices.

Systems and methods are provided for implementing bandstop filters (e.g., RF/microwave bandstop filters) that can automatically tune to a frequency of an interfering signal. Embodiments of the present disclosure provide automatically tunable signal-tracking bandstop filters with a significant reduction in response time, complexity, size, weight, and cost when compared to conventional devices.

Various examples are provided related to bimodal electron paramagnetic resonance (EPR). In one example, a bimodal resonator includes a detection coil; first and second excitation coils, where the excitation coils are non-parallel separated by a fixed angle; and excitation controllers coupled to the first and second excitation coils. The excitation controllers can adjust radio frequency (RF) fields generated by the first and second excitation coils to produce a resonator field substantially parallel with the detection coil. In another example, a method including generating a first RF field by exciting the first excitation coil; generating a second RF field by exciting the second excitation coil; and producing a resonator field substantially parallel with a detection coil of the bimodal resonator by adjusting the RE field of the first excitation coil, the RF filed of the second excitation coil, or both.

Various examples are provided related to bimodal electron paramagnetic resonance (EPR). In one example, a bimodal resonator includes a detection coil; first and second excitation coils, where the excitation coils are non-parallel separated by a fixed angle; and excitation controllers coupled to the first and second excitation coils. The excitation controllers can adjust radio frequency (RF) fields generated by the first and second excitation coils to produce a resonator field substantially parallel with the detection coil. In another example, a method including generating a first RF field by exciting the first excitation coil; generating a second RF field by exciting the second excitation coil; and producing a resonator field substantially parallel with a detection coil of the bimodal resonator by adjusting the RE field of the first excitation coil, the RF filed of the second excitation coil, or both.

Various examples are provided related to bimodal electron paramagnetic resonance (EPR). In one example, a bimodal resonator includes a detection coil; first and second excitation coils, where the excitation coils are non-parallel separated by a fixed angle; and excitation controllers coupled to the first and second excitation coils. The excitation controllers can adjust radio frequency (RF) fields generated by the first and second excitation coils to produce a resonator field substantially parallel with the detection coil. In another example, a method including generating a first RF field by exciting the first excitation coil; generating a second RF field by exciting the second excitation coil; and producing a resonator field substantially parallel with a detection coil of the bimodal resonator by adjusting the RE field of the first excitation coil, the RF filed of the second excitation coil, or both.

Various examples are provided related to bimodal electron paramagnetic resonance (EPR). In one example, a bimodal resonator includes a detection coil; first and second excitation coils, where the excitation coils are non-parallel separated by a fixed angle; and excitation controllers coupled to the first and second excitation coils. The excitation controllers can adjust radio frequency (RF) fields generated by the first and second excitation coils to produce a resonator field substantially parallel with the detection coil. In another example, a method including generating a first RF field by exciting the first excitation coil; generating a second RF field by exciting the second excitation coil; and producing a resonator field substantially parallel with a detection coil of the bimodal resonator by adjusting the RE field of the first excitation coil, the RF filed of the second excitation coil, or both.