An antenna tuning circuit achieves robust performance in a closed loop antenna tuning system due to the addition of protection circuits. In one instance, a protection circuit to detect an overload condition based on a threshold value may be included in the antenna tuning circuit. The antenna tuning circuit also includes a protection state register coupled to the protection circuit to store one or more safe states of operation to which the circuit is restored in response to detecting the overload condition. The antenna tuning circuit also includes a bus interface coupled to the protection state register to transmit an indication of a state of operation of the circuit to an external tuning control device coupled to the circuit and to receive pre-defined protection actions from the external tuning control device in response to the indication of the state of operation.

An antenna tuning circuit achieves robust performance in a closed loop antenna tuning system due to the addition of protection circuits. In one instance, a protection circuit to detect an overload condition based on a threshold value may be included in the antenna tuning circuit. The antenna tuning circuit also includes a protection state register coupled to the protection circuit to store one or more safe states of operation to which the circuit is restored in response to detecting the overload condition. The antenna tuning circuit also includes a bus interface coupled to the protection state register to transmit an indication of a state of operation of the circuit to an external tuning control device coupled to the circuit and to receive pre-defined protection actions from the external tuning control device in response to the indication of the state of operation.

Various NLTL frequency comb generator embodiments are disclosed for compressing rise time, fall time, or both rise time and fall time of an input signal to generate an output signal comprising multiple harmonics of the input signal. The NLTL frequency comb generator may comprise a plurality of segments cascaded in series with each segment comprising a series inductor, a shunt capacitor, and a reverse shunt capacitor for balanced signal compression. The shunt capacitor and the reverse shunt capacitor may be varactors or Schottky diodes that have voltage-dependent capacitance. As a result, both rise time and fall time of the input signal are compressed along the NLTL frequency comb generator. With a sinusoidal signal input, the output signal may be close to a square wave. Such a square wave output naturally suppresses all even harmonics, which can be valuable for odd harmonics signal extraction or filtration.

Various NLTL frequency comb generator embodiments are disclosed for compressing rise time, fall time, or both rise time and fall time of an input signal to generate an output signal comprising multiple harmonics of the input signal. The NLTL frequency comb generator may comprise a plurality of segments cascaded in series with each segment comprising a series inductor, a shunt capacitor, and a reverse shunt capacitor for balanced signal compression. The shunt capacitor and the reverse shunt capacitor may be varactors or Schottky diodes that have voltage-dependent capacitance. As a result, both rise time and fall time of the input signal are compressed along the NLTL frequency comb generator. With a sinusoidal signal input, the output signal may be close to a square wave. Such a square wave output naturally suppresses all even harmonics, which can be valuable for odd harmonics signal extraction or filtration.