Modulation of An RF Transmit Signal

• US 20070252657A1
• Filed: 04/06/2006
• Published: 11/01/2007
• Est. Priority Date: 04/06/2006
• Status: Active Grant

• Current Assignee: Preco Electronics Incorporated (Sensata Technologies Holding Plc)
• Original Assignee: Preco Electronics Incorporated (Sensata Technologies Holding Plc)
• Inventors: Hayden, Douglas
• Granted Patent: US 7,548,133 B2
• Time in Patent Office: Days
• US Class Current: 332/117
• CPC Class Codes: H03C 3/245 by using semiconductor elements

Abstract

To modulate the frequency of a signal to be transmitted, the biasing voltage applied to a terminal of a transistor is dynamically modulated. To achieve this, the pulse width or a pulse amplitude of a control signal is modulated. Alternatively, a multi-bit control signal may be used to perform the modulation. The frequency of the transmitted signal is optionally modulated by varying the temperature of a oscillator. To vary this temperature, the current flowing through one or more resistive elements positioned in proximity of the oscillator is varied in response to the pulse width or amplitude of a second control signal. The temperature may also be changed by varying a multi-bit control signal. As the level of this current flow varies, the amount of heat emitted by the resistors vary, thereby changing the temperature of the oscillator which has a non-zero temperature coefficient.

Claims

1. A circuit operative to modulate oscillation frequency of a transmit signal, the circuit comprising:

a control block adapted to dynamically modulate a generated signal;

a filter adapted to modify a biasing voltage applied to a first terminal of a transistor in response to variations in the generated voltage signal; and

a pulse generator adapted to generate a pulse signal in response to detection of a transition of an oscillating signal;

said transistor adapted to generate a radio frequency signal in response to receipt of a low-to-high or high-to-low transition of the generated pulse.

2. The circuit of claim 1 wherein said generated signal is a pulse-width modulated signal.

3. The circuit of claim 1 wherein said generated signal is an pulse-amplitude modulated signal.

4. The circuit of claim 1 wherein said generated signal is a multi-bit signal, the circuit further comprising:

an analog-to-digital converter configured to convert the multi-bit signal to an analog signal.

5. The circuit of claim 1 further comprising an RC filter adapted to filter out high frequency components of the modulated signal.

6. The circuit of claim 5 further comprising an amplifier adapted to generate the biasing signal in response to receipt of the filtered modulated signal at its positive input terminal, wherein a negative input terminal of the amplifier is coupled to an output terminal of the amplifier.

7. The circuit of claim 6 further comprising an oscillator adapted to generate the oscillating signal.

8. The circuit of claim 7 wherein the generated signal is modulated by varying a value of a register disposed in the control block.

9. The circuit of claim 8 wherein said control block is a commercially available microcontroller.

10. The circuit of claim 9 wherein a gate terminal of said transmit transistor is coupled to the ground potential.

11. A method of modulating an oscillation frequency of a transmit signal, the method comprising:

modulating a generated signal dynamically;

varying a biasing signal in response to modulation of the generated signal;

applying the biasing signal to a first terminal of a transmit transistor;

generating a pulse in response to detection of a transition of a clock signal; and

applying the generated pulse to a second terminal of the transmit transistor;

12. The method of claim 11 wherein said generated signal is a pulse-width modulated signal.

13. The method of claim 11 wherein said generated signal is an pulse-amplitude modulated signal.

14. The method of claim 11 wherein said generated signal is a multi-bit signal, the method further comprising:

converting the multi-bit signal to an analog signal.

15. The method of claim 11 further comprising:

filtering out high frequency components of the modulated signal.

16. The method of claim 15 further comprising:

amplifying the filtered out modulated signal to generate the biasing signal.

17. The method of claim 16 wherein the generated signal is modulated by varying a register value.

18. The method of claim 17 further comprising:

coupling a gate terminal of said transmit transistor to the ground potential.

19. A circuit operative to vary oscillation frequency of an oscillator adapted to supply a clock signal, the circuit comprising:

one ore more resistive elements disposed in proximity of said oscillator; and

a control circuit adapted to vary current flow through the one or more resistors in response to modulation of a control signal, wherein the current flow through the one or more resistors is adapted to vary the temperature of the thereby to vary the frequency of the clock signal.

20. The circuit of claim 19 wherein said control signal is a pulse-width modulated signal.

21. The circuit of claim 19 wherein said control signal is an pulse-amplitude modulated signal.

22. The circuit of claim 19 wherein said control signal is a multi-bit signal, the circuit further comprising:

a digital-to-analog converter configured to convert the multi-bit signal to an analog signal.

23. The circuit of claim 19 wherein said control circuit comprises a transistor having a first terminal adapted to receive the modulated control signal, a second terminal coupled to a common node, and a third terminal coupled to the ground.

24. The circuit of claim 23 wherein a terminal of each of the one or more resistors is coupled to a supply voltage.

25. The circuit of claim 24 further comprising:

disabling circuit adapted to disable the clock signal in response to receipt of a disabling signal.

26. A method of varying a frequency of a clock signal, the method comprising:

modulating a control signal;

varying current flow through one or more resistive elements in response to the modulation of the control signal thereby to vary a heat generated by the one ore more resistors; and

varying a temperature of an oscillator in response to the variation in the generated heat.

27. The method of claim 26 wherein said control signal is a pulse-width modulated signal.

28. The method of claim 26 wherein said control signal is a pulse amplitude modulated signal.

29. The method of claim 26 wherein said control signal is a multi-bit signal, the method further comprising:

converting the multi-bit signal to an analog signal.

30. The method of 26 wherein the current flow through the one or more resistors is varied via a transistor having a first terminal adapted to receive the modulated signal, a second terminal coupled to a common terminal of the one or more resistors, and a third terminal coupled to the ground.

31. The method of claim 30 wherein a second terminal of each of the one ore more resistors is coupled to a supply voltage.

32. The method of claim 31 further comprising disabling the oscillating signal in response to receipt of a disabling signal.