A differential crystal oscillator includes a source follower configured to receive an oscillatory signal and output a regenerated signal; a resonant network having a crystal and configured to terminate the oscillatory signal and determine an oscillation frequency of the oscillatory signal; a regenerative network configured to regenerate the regenerated signal; and a capacitive feedback network configured to provide a feedback from the regenerated signal to the oscillatory signal.

We disclose frequency doublers for use in millimeter-wave devices. One such frequency doubler comprises at least one passive mixer comprising at least one of the following: at least one transistor configured to receive a back gate voltage; at least one first input driver circuit; and two second input driver circuits. We also disclose a method comprising determining a target output voltage of a frequency doubler comprising at least one passive mixer comprising at least one transistor configured to receive a back gate voltage; determining an output voltage of the frequency doubler; increasing a back gate voltage of the at least one transistor, in response to determining that the output voltage is below the target output voltage; and decreasing the back gate voltage of the at least one transistor, in response to determining that the output voltage is above the target output voltage.

We disclose frequency doublers for use in millimeter-wave devices. One such frequency doubler comprises at least one passive mixer comprising at least one of the following: at least one transistor configured to receive a back gate voltage; at least one first input driver circuit; and two second input driver circuits. We also disclose a method comprising determining a target output voltage of a frequency doubler comprising at least one passive mixer comprising at least one transistor configured to receive a back gate voltage; determining an output voltage of the frequency doubler; increasing a back gate voltage of the at least one transistor, in response to determining that the output voltage is below the target output voltage; and decreasing the back gate voltage of the at least one transistor, in response to determining that the output voltage is above the target output voltage.

Methods and systems for a distributed transmission line multiplexer for a multi-core multi-mode voltage-controlled oscillator (VCO) may comprise a plurality of voltage controlled oscillators (VCOs) arranged adjacent to each other, where each of the plurality of VCOs are operable to generate an output signal at a configurable frequency, an impedance matching circuit comprising a respective driver and impedance matching elements coupled to each of the plurality of VCOs, and an output device coupled to the impedance matching circuit. The impedance matching elements may include capacitors and inductors. Between each adjacent pair of the respective drivers coupled to each of the plurality of VCOs, the impedance matching elements may include two inductors coupled in series between the drivers and a capacitor coupled to ground and to a common node between the two inductors. Impedance values of the capacitors and inductors may be configurable.