Modulation of an RF transmit signal

• US 7,548,133 B2
• Filed: 04/06/2006
• Issued: 06/16/2009
• 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 Todd
• Primary Examiner(s): Pascal; Robert
• Assistant Examiner(s): Goodley; James E
• Application Number:
  US11/278,936
• Publication Number:
  US 20070252657A1
• Time in Patent Office: 1,167 Days
• Field of Search: 332/117, 332/120, 375/297, 455/102, 455/108
• US Class Current: 332/120
• 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 signal to generate a biasing 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 burst at a harmonic of the frequency of the generated pulse in response to receipt of a low-to-high or high-to-low transition of the generated pulse signal wherein voltage of the biasing signal selects the harmonic of the frequency of the pulse signal.

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:

a digital-to-analog 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. 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 signal;

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;

an RC filter adapted to filter out high frequency components of the modulated signal;

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; and

an oscillator adapted to generate the oscillating signal,

wherein the generated signal is modulated by varying a value of a register disposed in the control block,

wherein said control block is a commercially available microcontroller, and

wherein a gate terminal of said transmit transistor is coupled to the ground potential.

19. The circuit of claim 10 wherein said generated signal is a pulse-width modulated signal.

20. The circuit of claim 10 wherein said generated signal is an pulse-amplitude modulated signal.

21. The circuit of claim 10 wherein said generated 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.

22. The circuit of claim 10 further comprising an RC filter adapted to filter out high frequency components of the modulated signal.

23. The circuit of claim 22 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.

24. The circuit of claim 23 further comprising an oscillator adapted to generate the oscillating signal.

25. The circuit of claim 24 wherein the generated signal is modulated by varying a value of a register disposed in the control block.

26. The circuit of claim 25 wherein said control block is a commercially available microcontroller.

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;

applying the generated pulse to a second terminal of the transmit transistor to generate a radio frequency burst at a harmonic of the frequency of the generated pulse in response to a low-to-high or high-to-low transition of the generated pulse, wherein voltage of the biasing signal selects the harmonic of the frequency of the generated pulse.

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. 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;

filtering out high frequency components of the modulated signal;

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

varying a register value for modulate the generated signal; and

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

27. The method of claim 18 wherein said generated signal is a pulse-width modulated signal.

28. The method of claim 18 wherein said generated signal is an pulse-amplitude modulated signal.

29. The method of claim 18 wherein said generated signal is a multi-bit signal, the method further comprising:

converting the multi-bit signal to an analog signal.

30. The method of claim 18 further comprising:

filtering out high frequency components of the modulated signal.

31. The method of claim 30 further comprising:

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

32. The method of claim 31 wherein the generated signal is modulated by varying a register value.