Apparatus and methods for timing offset compensation of frequency synthesizers are provided herein. In certain embodiments, an electronic system includes a frequency synthesizer, such as a fractional-N phase-locked loop (PLL), which generates an output clock signal based on timing of a reference clock signal. Additionally, the electronic system includes an integer PLL configured to compensate for a timing offset, such as a phase offset and/or frequency offset, of the frequency synthesizer based on timing of the output clock signal.

A charge pump includes: a switch circuit that switches a current source conducted to an output node based on a signal from a phase frequency detector included in a PLL circuit; a first current source that is the current source provided between a high potential node and the switch circuit, and supplies a current to the output node by a first conduction-type depletion mode MOS transistor forming a self-bias circuit; and a second current source that is the current source provided between a low potential node and the switch circuit, and draws the current from the output node by the first conduction-type depletion mode MOS transistor forming the self-bias circuit.

A phase locked circuit includes an oscillator configured to generate an output clock signal, a first phase detector configured to detect a phase difference between an input clock signal and a feedback clock signal based on the output clock signal, a second phase detector having a wider phase locking range than that of the first phase detector and configured to detect the phase difference between the input clock signal and the feedback clock signal, and a charge pump controller configured to control an output current of a charge pump included in the second phase detector based on the phase difference detected by the first phase detector. When the phase difference between the input clock signal and the feedback clock signal is within the phase locking range of the first phase detector, the oscillator and the first phase detector are connected to each other.

A phase locked circuit includes an oscillator configured to generate an output clock signal, a first phase detector configured to detect a phase difference between an input clock signal and a feedback clock signal based on the output clock signal, a second phase detector having a wider phase locking range than that of the first phase detector and configured to detect the phase difference between the input clock signal and the feedback clock signal, and a charge pump controller configured to control an output current of a charge pump included in the second phase detector based on the phase difference detected by the first phase detector. When the phase difference between the input clock signal and the feedback clock signal is within the phase locking range of the first phase detector, the oscillator and the first phase detector are connected to each other.

The invention provides a phase difference generator error compensation method of a digital frequency generator, wherein the digital frequency generator comprises a phase difference generator, the phase difference generator comprises a phase compensation module and an adjusting module, the phase compensation module provides at least two clock signals, the at least two clock signals comprise a first clock signal and a second clock signal, and a phase difference exists between the first clock signal and the second clock signal; the phase compensation module outputs a third clock signal according to the first clock signal and the second clock signal, and the third clock signal is a difference signal of the first clock signal and the second clock signal; the adjusting module compensates the error of the third clock signal according to the clock phase difference. The method has the benefits that process errors in the phase difference generator are compensated.

A voltage controlled oscillator (VCO) circuit and method achieves linearized frequency tuning over an extended range of analog tuning voltage by implementing a magnetic balun/transformer for biasing and coupling varactor elements. An active negative transconductance circuit of cross-coupled transistors have drains connected with a resonant tank circuit and at least a first varactor element having ends connected to respective first ends of respective first coils of a respective first and second magnetic balun. Respective second ends of respective first coils of respective first and second baluns are connected to a first reference supply voltage. A second varactor element has ends connecting respective first ends of respective second coils of said first and second baluns. A sinking of a bias current through the resonant tank circuit and the transconductance circuit generates an oscillating signal. A calibration method achieves precise VCO gain over wide tuning voltage range, thereby enhancing VCO linearity.

An output circuit comprises an output terminal (11), a first current mirror (12), a first pass transistor (13) and a first delivering terminal (14) coupled via the first current mirror (12) and the first pass transistor (13) to the output terminal (11).

A PLL frequency synthesizer includes a voltage controlled oscillator that outputs an oscillation signal having a frequency corresponding to a control voltage value, a phase comparison unit that outputs a phase difference signal representing a phase difference between a feedback oscillation signal and a reference oscillation signal, a charge pump that outputs a charge and discharge current according to the phase difference, a loop filter that outputs the control voltage value, which is increased or decreased according to a charge and discharge amount of a capacitive element, to the voltage controlled oscillator, a detection unit that detects a change rate of the control voltage value, and a control unit that adjusts the charge and discharge current, a characteristic of the loop filter, or a characteristic of the voltage controlled oscillator based on a detection result of the detection unit.

A method for a radar device is described. According to one example implementation, the method comprises generating an RF signal using a voltage-controlled oscillator (VCO), wherein the frequency of the RF signal depends on a first tuning voltage and a second tuning voltage. The method also comprises setting the second tuning voltage using a phase-locked loop coupled to the VCO, with the result that the frequency of the RF signal corresponds to a desired frequency. The first tuning voltage is changed in such a manner that the second tuning voltage set by the phase-locked loop corresponds approximately to a predefined value. Another example implementation relates to a method for a radar device comprising: generating an RF signal using a VCO, wherein the frequency of the RF signal depends on a tuning voltage, setting the tuning voltage using a phase-locked loop coupled to the VCO, with the result that the frequency of the RF signal corresponds to a desired frequency, and determining a differential VCO gain of the VCO. The bandwidth of the phase-locked loop is set on the basis of the determined VCO gain.

A circuit includes a first signal swapper including a first terminal coupled to a first current source, a second terminal coupled to a second current source, a third terminal coupled to a first current terminal of a first transistor, and a fourth terminal coupled to a third current terminal of a second transistor. The first signal swapper couples the first and second terminals to the third and fourth terminals responsive to a first control signal. First and second switches couple to a gate of the first transistor. The first switch receives the input oscillation signal and the second switch receives a first reference voltage. Third and fourth switches couple to a gate of the second transistor. The third switch receives the input oscillation signal and the fourth switch receives the first reference voltage. A second signal swapper couples to the first signal swapper and to the first and second transistors.