A voltage controlled oscillator (VCO) circuit is disclosed. The VCO circuit comprises a VCO tuning circuit comprising a primary inductive coil. In some embodiments, the VCO tuning circuit is configured to generate a VCO output signal at a first resonance frequency. The VCO circuit further comprises a filter circuit comprising a secondary inductive coil. In some embodiments, the filter circuit is configured to resonate at a second, different, resonance frequency, in order to filter a noise associated with the VCO tuning circuit. In some embodiments, the primary inductive coil associated with the VCO tuning circuit and the secondary inductive coil associated with the filter circuit are concentrically arranged with respect to one another. Further, in some embodiments, the primary inductive coil associated with the VCO tuning circuit and the secondary inductive coil associated with the filter circuit are magnetically decoupled with respect to one another.

Certain aspects relate to a semiconductor die. The semiconductor die includes a voltage-controlled oscillator (VCO), wherein the VCO includes a resonant capacitor, and a resonant inductor coupled in parallel with the resonant capacitor. The resonant inductor includes a first elongated portion and a second elongated portion that are parallel with each other. The semiconductor die also includes a voltage supply line configured to route a supply voltage to the VCO, wherein the voltage supply line includes a first portion that runs parallel with the first and second elongated portions of the resonant inductor and is located between the first and second elongated portions of the resonant inductor.

For communication across a capacitively coupled channel, an example circuit includes a first plate substantially parallel to a substrate, forming a first capacitance intermediate the first plate and the substrate. A second plate is substantially parallel to the substrate and the first plate, the first plate intermediate the substrate and the second plate. A third plate is substantially parallel to the substrate, forming a second capacitance intermediate the third plate and the substrate. A fourth plate is substantially parallel to the substrate and the third plate, the third plate intermediate the substrate and the fourth plate. An inductor is connected to the first plate and the third plate, the inductor to, in combination with the first capacitance and the second capacitance, form an LC amplifier.

A voltage-controlled oscillator (VCO) includes a power supply node configured to have a power supply voltage. A reference node is configured to have a first reference voltage. A transformer-coupled band-pass filter (BPF) is coupled to a cross-coupled pair of transistors. The cross-coupled pair of transistors and the transformer-coupled band-pass filter are positioned between the power supply node and the reference node.

Various technologies described herein pertain to non-inverting multi-mode oscillators. An oscillator circuit can include a non-inverting sustaining amplifier and a feedback network. The non-inverting sustaining amplifier includes an amplifier input and an amplifier output. The feedback network includes a crystal, an input portion, and an output portion. The crystal of the feedback network can be connected between the amplifier input and the amplifier output of the non-inverting sustaining amplifier. The input portion of the feedback network can be connected between the amplifier input and ground, and can include an inductor realized using a tank circuit. Further, the output portion of the feedback network can be connected between the amplifier output and ground, and can include a capacitor. Moreover, the crystal can operate in series resonance mode or parallel resonance mode.

An oscillator circuit (10) for generating quadrature-related first and second oscillation signals having equal frequencies comprises a first oscillation circuit (VCO_I) configured to generate the first oscillation signal having a first controllable frequency, a second oscillation circuit (VCO_Q) configured to generate the second oscillation signal having a second controllable frequency; and a controller (100) configured to enable and disable oscillation of the first and second oscillation circuits (VCO_I, VCO_Q) and to control the first and second controllable frequencies, such that when the oscillation is enabled, the first and second controllable frequencies are controlled to be initially unequal and then to become equal.

Apparatus for communication across a capacitively coupled channel are disclosed herein. An example circuit includes a first plate substantially parallel to a substrate, thereby forming a first capacitance intermediate the first plate and the substrate. A second plate is substantially parallel to the substrate and the first plate, the first plate intermediate the substrate and the second plate. A third plate is substantially parallel to the substrate, thereby forming a second capacitance intermediate the third plate and the substrate. A fourth plate is substantially parallel to the substrate and the third plate, the third plate intermediate the substrate and the fourth plate. An inductor is connected to the first plate and the third plate, the inductor to, in combination with the first capacitance and the second capacitance, form an LC amplifier.

Systems and methods are provided for generating reference signals with high interference immunity. A signal source may generate reference signals having a particular reference frequency based on characteristics of the source of the reference signals, for use in driving at least one component in a system. One or more processing may then process the generated reference signals, based on particular frequency positions relative to the particular reference frequency and other operations and/or components of the system. The processing may include filtering at the particular frequency positions. The particular frequency positions may correspond to the harmonics positions of the particular reference frequency. The signal source may be a crystal oscillator.

A digital modulating device includes an oscillator that generates an oscillation signal, and a frequency doubling modulator that includes: a single-ended to differential converter converting the oscillation signal into two periodic signals; two inductors respectively receiving the periodic signals and respectively providing two input signals; a switching circuit; and two amplifier circuits. When the switching circuit operates in a first state, the amplifier circuits respectively amplify the input signals to respectively generate two amplified signals that are combined into a combined signal at a common node thereof. When the switching circuit operates in a second state, the amplifier circuits do not perform amplification.

A digital modulating device includes an oscillator that generates an oscillation signal, and a frequency doubling modulator that includes: a single-ended to differential converter converting the oscillation signal into two periodic signals; two inductors respectively receiving the periodic signals and respectively providing two input signals; a switching circuit; and two amplifier circuits. When the switching circuit operates in a first state, the amplifier circuits respectively amplify the input signals to respectively generate two amplified signals that are combined into a combined signal at a common node thereof. When the switching circuit operates in a second state, the amplifier circuits do not perform amplification.