Common Mode Rejection Circuit

• US 20130135057A1
• Filed: 11/25/2011
• Published: 05/30/2013
• Est. Priority Date: 11/25/2011
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Mobile Communications GmbH (Intel Corporation)
• Inventors: Roithmeier, Andreas
• Granted Patent: US 8,773,211 B2
• Time in Patent Office: Days
• US Class Current: 331/117.FE
• CPC Class Codes: H03B 2200/0054 including measures to switch a filter, e.g. for frequency tuning or for harmonic selection
• CPC Class Codes: H03B 2201/035 the parameter being another frequency, e.g. a harmonic of the oscillating frequency
• CPC Class Codes: H03B 2202/05 Reduction of undesired oscillations through filtering or through special resonator characteristics
• CPC Class Codes: H03B 5/1215 the current source or degeneration circuit being in common to both transistors of the pair, e.g. a cross-coupled long-tailed pair
• CPC Class Codes: H03B 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H03B 5/124 the means comprising a voltage dependent capacitance
• CPC Class Codes: H03B 5/1265 switched capacitors
• CPC Class Codes: H03B 5/1284 the parameter being another frequency, e.g. a harmonic of the oscillating frequency

Abstract

An electrical circuit includes a circuit element and a common mode rejection circuit element. The circuit element is configured to operate at a selected frequency within a variable frequency range and the common mode rejection circuit element is configured to reject a common mode current through the circuit element, wherein the common mode rejection circuit element is adjustable.

Claims

1. An electrical circuit comprising:

a circuit element configured to operate at a selected frequency within a variable frequency range; and

a common mode rejection circuit element configured to reject a common mode current through the circuit element, wherein the common mode rejection circuit element is adjustable.

2. The electrical circuit according to claim 1, wherein the common mode rejection circuit element is adjustable as a function of the selected frequency or another performance parameter of the circuit element.

3. The electrical circuit according to claim 1, wherein the common mode rejection circuit element comprises a resonant circuit, a resonance frequency of which is adjustable in order to adjust the common mode rejection circuit element.

4. The electrical circuit according to claim 3, wherein the resonant circuit is configured to adapt the resonance frequency such that the resonance frequency is equal to a second harmonic frequency with respect to the selected frequency.

5. The electrical circuit according to claim 3, wherein the resonant circuit comprises:

a plurality of switchable capacitors connected in parallel to each other and to an inductor for adjusting the resonance frequency;

or

a plurality of switchable inductors connected in series and connected in parallel with a capacitor for adjusting the resonance frequency.

6. The electrical circuit according to claim 2, wherein the common mode rejection circuit element comprises a controller configured to receive an information on the selected frequency and to adjust the common mode rejection circuit element in response thereto.

7. The electrical circuit according to claim 1, wherein the common mode rejection circuit element is connected in series between the circuit element and ground.

8. The electrical circuit according to claim 1, wherein the circuit element comprises an oscillator, mixer, buffer, operational amplifier or differential amplifier.

9. An electrical circuit comprising:

a circuit element configured to operate at a selected frequency within a variable frequency range; and

means for rejecting a common mode current through the circuit element as a function of the selected frequency.

10. An oscillation device comprising:

an oscillator configured to provide a variable oscillation frequency; and

a common mode rejection circuit element connected to the oscillator in series and comprising a resonant circuit configured to reject a common mode current through the oscillator, wherein a resonance frequency of the resonant circuit is adjustable.

11. The oscillation device according to claim 10, wherein a resonance frequency of the resonant circuit is adjustable as a function of the oscillation frequency or another performance parameter of the oscillator.

12. The oscillation device according to claim 10, wherein the oscillator comprises a differential amplifier, one or more inductors and an adjustable capacitor for selecting the oscillation frequency, wherein the adjustable capacitor is connected in parallel with the one or more inductors.

13. The oscillation device according to claim 12, wherein the common mode rejection circuit element is connected in series between the differential amplifier and ground.

14. The oscillation device according to claim 12, wherein the differential amplifier comprises a differential transistor pair coupled to a common source node via which the oscillator is connected to the common mode rejection circuit element,

wherein each transistor of the differential transistor pair is coupled with the other transistor via a mutual feedback loop, and

wherein the adjustable capacitor and the one or more inductors are connected between two drain contacts of the differential transistor pair.

15. The oscillation device according to claim 12, wherein the differential amplifier comprises two differential transistor pairs which are coupled as push-pull stages,

wherein a type of the transistors of a first differential transistor pair differs from a type of the transistors of a second differential transistor pair,

wherein each transistor of the two differential transistor pairs is coupled with the other transistor of the respective differential transistor pair via a mutual feedback loop, and

wherein the adjustable capacitor and the one or more inductors are connected between a common drain contact of a first push-pull stage and a common drain contact of a second push-pull stage.

16. The oscillation device according to claim 15, wherein the oscillator comprises a further common mode rejection circuit element connected between a further common source node of the second differential transistor pair and a power supply, wherein the further common mode rejection circuit is configured to reject a common mode current through the oscillator.

17. A method for operating an electrical circuit comprising a circuit element and a common mode rejection circuit element, the method comprising the following steps:

operating the circuit element at a selected frequency within a variable frequency range;

adjusting the common mode rejection circuit element based on the circuit element; and

rejecting a common mode current through the circuit element by use of the common mode rejection circuit element.

18. The method according to claim 17, wherein the step of adjusting the common mode rejection circuit element is performed such that the common mode rejection circuit element is adjusted as a function of the selected frequency or another performance parameter of the circuit element.

19. The method according to claim 17, wherein the step of adjusting the common mode rejection circuit element is performed by switching a plurality of parallel capacitors of a common mode rejection circuit element or by switching a plurality of serial inductors of the common mode rejection circuit element.

20. The method according to claim 18 further comprises a step of receiving an information on the selected frequency from the circuit element and using the information in adjusting the common mode rejection circuit element.

21. A method for operating an oscillation device comprising an oscillator and a common mode rejection circuit element, the method comprising the following steps:

outputting a variable oscillation frequency by use of the oscillator;

adjusting a resonance frequency of a resonant circuit of the common mode rejection circuit element based on the oscillator; and

rejecting a common mode current through the oscillator by use of a common mode rejection circuit element.

22. The method according to claim 21, wherein the step of adjusting the resonance frequency is performed such that the resonance frequency is adjusted as a function of the variable oscillation frequency or another performance parameter of the oscillator.