Digitally controlled oscillator

• US 10,735,012 B2
• Filed: 12/21/2017
• Issued: 08/04/2020
• Est. Priority Date: 12/30/2016
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Pavlovic, Nenad
• Primary Examiner(s): Bythrow, Peter M
• Application Number:
  US15/849,683
• Publication Number:
  US 20180191364A1
• Time in Patent Office: 957 Days
• CPC Class Codes: G01S 13/343 using sawtooth modulation
• CPC Class Codes: G01S 7/032 Constructional details for solid-state radar subsystems
• CPC Class Codes: G01S 7/35 Details of non-pulse systems
• CPC Class Codes: H03K 3/0231 Astable circuits H03K3/0315 takes precedence
• CPC Class Codes: H03L 2207/06 Phase locked loops with a controlled oscillator having at least two frequency control terminals
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop
• CPC Class Codes: H03L 7/0991 the oscillator being a digital oscillator, e.g. composed of a fixed oscillator followed by a variable frequency divider H03L7/0995 takes precedence; fixed oscillators with means for selecting among various phases H03L7/0814
• CPC Class Codes: H03L 7/197 a time difference being used for locking the loop, the counter counting between numbers which are variable in time or the frequency divider dividing by a factor variable in time, e.g. for obtaining fractional frequency division H03L7/1806 takes precedence
• CPC Class Codes: H03M 1/0854 of quantisation noise

Abstract

A digitally controlled oscillator comprising a filtering digital to analogue converter, DAC, component and a voltage controlled oscillator, VCO, component comprising at least one control terminal arranged to receive a control voltage output by the DAC component; wherein the DAC component comprises a voltage generation component arranged to generate the control voltage and at least one configurable capacitive load component to which the control voltage is applied such that a filtering bandwidth of the DAC component is configurable by way of the at least one configurable capacitive load component.

Claims

1. A digitally controlled oscillator comprising a filtering digital to analogue converter (DAC) component and a voltage controlled oscillator (VCO) component comprising at least one control terminal arranged to receive a control voltage output by the DAC component, wherein the DAC component comprises a voltage generation component arranged to generate the control voltage and at least one configurable capacitive load component to which the control voltage is applied such that a filtering bandwidth of the DAC component is configurable by way of the at least one configurable capacitive load component.

2. The digitally controlled oscillator of claim 1, wherein the at least one configurable capacitive load component comprises:

a decouplable capacitance comprising a first terminal coupled to a reference voltage node,

a coupling switch coupled in series with the decouplable capacitance between an output node of the voltage generation component and a second terminal of the decouplable capacitance, and

a discharge switch coupled in parallel with the decouplable capacitance;

wherein the coupling switch is controllable via a first control signal to selectively couple the output node of the voltage generation component to the second terminal of the decouplable capacitance and the at least one control terminal of the VCO component, and the discharge switch is controllable via a second control signal to selectively create a discharge path between the first and second terminals of the decouplable capacitance.

3. The digitally controlled oscillator of claim 2, wherein the at least one configurable capacitive load component further comprises at least one fixed capacitance comprising a first terminal coupled to the reference voltage node and a second terminal coupled to the output node of the voltage generation component.

4. The digitally controlled oscillator of claim 2, wherein the second terminal of the decouplable capacitance is coupled to the at least one control terminal of the VCO component such that the coupling switch is coupled between the output node of the voltage generation component and the at least one control terminal of the VCO component such that when the coupling switch is controlled to decouple the output node of the voltage generation component from the second terminal of the decouplable capacitance, the decouplable capacitance remains coupled to the at least one control terminal of the VCO component.

5. The digitally controlled oscillator of claim 2, wherein the VCO component comprises a first control terminal and at least one further control terminal, and the DAC component comprises a first configurable capacitive load component coupled between the output node of the voltage generation component and the first control terminal of the VCO component and a at least one further configurable capacitive load component coupled between the output node of the voltage generation component and the at least one further control terminal of the VCO component.

6. A frequency-modulated continuous-wave radar system comprising a digitally controlled oscillator according to claim 1.

7. The frequency-modulated continuous-wave radar system of claim 6, wherein the digitally controlled oscillator is arranged to generate a chirp signal.

8. The frequency-modulated continuous-wave radar system of claim 7, wherein during a chirp phase of the chirp signal, the at least one configurable capacitive load component is configured to reduce the filtering bandwidth of the DAC component.

9. The frequency-modulated continuous-wave radar system of claim 8, wherein during a reset phase of the chirp signal, the at least one configurable capacitive load component is configured to increase the filtering bandwidth of the DAC component.

10. The frequency-modulated continuous-wave radar system of claim 9, wherein during a reset phase of the chirp signal, the at least a part of the configurable capacitive load component is discharged.

11. The frequency-modulated continuous-wave radar system of claims 6, wherein the digitally controlled oscillator forms part of a phase-locked loop.

12. A method of calibrating a nonlinearity of the VCO component of the digitally controlled oscillator of claim 1;

the method comprising for each control terminal of the VCO component;

configuring the digitally controlled oscillator into a reset state for the respective control terminal;

performing calibration of the VCO to determine an output frequency of the digitally controlled oscillator with the digitally controlled oscillator configured in the reset state for the respective control terminal;

determining a VCO frequency control configuration for the reset state for the respective control terminal; and

storing the determined frequency control configuration for use during chirp signal generation.

13. The method of claim 12, wherein the method comprising calibrating the nonlinearity of the VCO component for each control terminal in a given sequence.