A system for a target image reconstruction includes a stepped frequency transmitter configured to emit a stepped frequency waveform having different constant frequencies at different periods of time and a modulator configured to modulate the stepped frequency waveform emitted at each period of time with a modulation signal to output a modulated stepped frequency waveform with an increased bandwidth. The system includes a transceiver configured to transmit the modulated stepped frequency waveform to a target and to accept reflection of the modulated stepped frequency waveform reflected from the target, a mixer to interfere the unmodulated stepped frequency waveform and the reflection of the modulated stepped frequency waveform to produce a beat signal of the interference of the unmodulated stepped frequency waveform with the reflection of the modulated stepped frequency waveform, and a signal processor to reconstruct an image of the target from the beat signal.

A self-oscillating spread spectrum frequency control loop contains a gated voltage-controlled oscillator (VCO) which receives a digital signal that can start or stop its oscillation. The VCO generates a spread spectrum carrier by receiving a triangle wave signal from a delaying ramp generator in a loop, its ramp direction controlled by a frequency comparator. The loop generates a spectrum spread as wide as possible above a minimum frequency. RF isolators that utilize low-pass filters in the transmitter and high-pass filters in the receiver, where the F-3 dB cutoff frequencies of both filters vary in a correlated manner, are used to not produce spread spectrum frequencies below the minimum frequency. Die from a given wafer lot, when designed such that the low- and high-pass cutoff frequencies track, can be used to form RF digital isolators whose minimum spread spectrum frequency does not go below the minimum frequency required by that wafer lot.

A self-oscillating spread spectrum frequency control loop contains a gated voltage-controlled oscillator (VCO) which receives a digital signal that can start or stop its oscillation. The VCO generates a spread spectrum carrier by receiving a triangle wave signal from a delaying ramp generator in a loop, its ramp direction controlled by a frequency comparator. The loop generates a spectrum spread as wide as possible above a minimum frequency. RF isolators that utilize low-pass filters in the transmitter and high-pass filters in the receiver, where the F-3 dB cutoff frequencies of both filters vary in a correlated manner, are used to not produce spread spectrum frequencies below the minimum frequency. Die from a given wafer lot, when designed such that the low- and high-pass cutoff frequencies track, can be used to form RF digital isolators whose minimum spread spectrum frequency does not go below the minimum frequency required by that wafer lot.

An oscillator includes a tunable resonant circuit having an inductance and a variable capacitance coupled between first and second nodes, and a set of capacitances selectively coupleable between the first and second nodes. An input control node receiving an input control signal is coupled to the variable capacitance and set of capacitances. The tunable resonant circuit is tunable based on the input control signal. A biasing circuit biases the tunable resonant circuit to generate a variable-frequency output signal between the first and second nodes. A voltage divider generates a set of different voltage thresholds, and a set of comparator circuits with hysteresis compares the input control signal to the set of different voltage thresholds to generate a set of control signals. The capacitances in the set of capacitances are selectively coupleable between the first and second nodes as a function of control signals in the set of control signals.

An aircraft includes an engine and a first variable frequency generator having a first rotor that is rotatable at a rate that is based on a rotational rate of the engine to cause the first variable frequency generator to generate a first multiphase signal. The aircraft further includes a second variable frequency generator having a second rotor that is rotatable at the rate to cause the second variable frequency generator to generate a second multiphase signal. The first multiphase signal is phase aligned with the second multiphase signal. The aircraft further includes one or more switches coupled to a first electrical system and configured to selectively provide power to the first electrical system based on either the first multiphase signal or the second multiphase signal.

An aircraft includes an engine and a first variable frequency generator having a first rotor that is rotatable at a rate that is based on a rotational rate of the engine to cause the first variable frequency generator to generate a first multiphase signal. The aircraft further includes a second variable frequency generator having a second rotor that is rotatable at the rate to cause the second variable frequency generator to generate a second multiphase signal. The first multiphase signal is phase aligned with the second multiphase signal. The aircraft further includes one or more switches coupled to a first electrical system and configured to selectively provide power to the first electrical system based on either the first multiphase signal or the second multiphase signal.

A self-oscillating spread spectrum frequency control loop contains a gated voltage-controlled oscillator (VCO) which receives a digital signal that can start or stop its oscillation. The VCO generates a spread spectrum carrier by receiving a triangle wave signal from a delaying ramp generator in a loop, its ramp direction controlled by a frequency comparator. The loop generates a spectrum spread as wide as possible above a minimum frequency. RF isolators that utilize low-pass filters in the transmitter and high-pass filters in the receiver, where the F-3 dB cutoff frequencies of both filters vary in a correlated manner, are used to not produce spread spectrum frequencies below the minimum frequency. Die from a given wafer lot, when designed such that the low- and high-pass cutoff frequencies track, can be used to form RF digital isolators whose minimum spread spectrum frequency does not go below the minimum frequency required by that wafer lot.

A self-oscillating spread spectrum frequency control loop contains a gated voltage-controlled oscillator (VCO) which receives a digital signal that can start or stop its oscillation. The VCO generates a spread spectrum carrier by receiving a triangle wave signal from a delaying ramp generator in a loop, its ramp direction controlled by a frequency comparator. The loop generates a spectrum spread as wide as possible above a minimum frequency. RF isolators that utilize low-pass filters in the transmitter and high-pass filters in the receiver, where the F-3 dB cutoff frequencies of both filters vary in a correlated manner, are used to not produce spread spectrum frequencies below the minimum frequency. Die from a given wafer lot, when designed such that the low- and high-pass cutoff frequencies track, can be used to form RF digital isolators whose minimum spread spectrum frequency does not go below the minimum frequency required by that wafer lot.

A digital isolator comprising a set of bipolar transistors and an inductor capacitor (LC) oscillator coupled to the set of bipolar transistors in series, wherein the LC oscillator is configured to be turned on and off based on the current applied to the set of bipolar transistors or the LC oscillator and generate a set of differential signals based on the current flowing through the set of bipolar transistors and mimicking the operational characteristics of an optocoupler.

A frequency synthesizer circuit included in a sensor circuit of a computer system may include a voltage-controlled oscillator circuit that may generate an oscillator signal. A three-point injection technique may be used to modulate the frequency of the oscillator signal. The three-point injection includes a low-frequency component that drives a feedback divider, and two high-frequency components that drive the voltage-controlled oscillator circuit. The strengths of the three injection points are aligned using samples of a tune signal generated using results of a comparison of a referenced signal and a frequency divided version of the oscillator signal.