Modulator and method for producing a modulated signal

• US 20060280258A1
• Filed: 06/12/2006
• Published: 12/14/2006
• Est. Priority Date: 06/14/2005
• Status: Active Grant

• Current Assignee: Given Imaging Limited (Medtronic Plc)
• Original Assignee: Given Imaging Limited (Medtronic Plc)
• Inventors: Bettesh, Ido
• Granted Patent: US 7,778,356 B2
• Time in Patent Office: Days
• US Class Current: 375/274
• CPC Class Codes: H03C 3/095 applying frequency modulation to the loop in front of the voltage controlled oscillator
• CPC Class Codes: H03C 3/0958 applying frequency modulation by varying the characteristics of the voltage controlled oscillator
• CPC Class Codes: H04L 27/2014 in which the phase changes in a piecewise linear manner during each symbol period, e.g. minimum shift keying, fast frequency shift keying H04L27/201 takes precedence

Abstract

A modulator including a direct modulation synthesizer circuit, a reference frequency oscillator for providing an input reference signal to the direct modulation synthesizer circuit for locking a carrier frequency to a stable frequency and a pre-emphasis unit for receiving data bits and for producing a modulating signal for direct modulation of the direct modulation synthesizer circuit, the modulating signal having data bit dependent voltage levels.

Claims

1. A modulator for producing a modulated signal, the modulator comprising:

a direct modulation synthesizer circuit;

a reference frequency oscillator for providing an input reference signal to the direct modulation synthesizer circuit for locking a carrier frequency to a stable frequency;

a pre-emphasis unit for receiving data bits and for producing a modulating signal for direct modulation of the direct modulation synthesizer circuit, the modulating signal having data bit dependent voltage levels.

2. The modulator according to claim 1, wherein the modulated signal is a CPFSK signal.

3. The modulator according to claim 1, wherein the pre-emphasis unit is a digital-to-analog converter and each voltage level of the modulating signal is a function of the bit values of a given data bit and of the data bit preceding the given data bit.

4. The modulator according to claim 1, wherein the pre-emphasis unit is a digital-to-analog converter and each voltage level of the modulating signal is a function of the bit values of a given data bit and of more than one data bit preceding the given data bit.

5. The modulator according to claim 3, wherein the modulating signal has at least four voltage levels.

6. The modulator according to claim 5, wherein the at least four voltage levels are:

V0, if the given data bit is “

0” and

the preceding data bit is “

0”

;

V0-δ

V, if the given data bit is “

0” and

the preceding data bit is “

1”

;

V1, if the given data bit is “

1” and

the preceding data bit is “

1”

; and

V1+δ

V, if the given data bit is “

1” and

the preceding data bit is “

0”

;

where V1 and V0 are standard bit-voltage levels and V1 is greater that V0, and δ

V is a positive voltage enhancement value by which the standard bit-voltage levels are altered by the pre-emphasis unit.

7. The modulator according to claim 1, wherein the direct modulation synthesizer circuit comprises a voltage controlled oscillator, into which the modulating signal is inputted, a phase detector that produces a phase detector output signal by comparing the input reference signal with a local frequency signal outputted from a feedback frequency divider connected to the voltage controlled oscillator, a charge pump that receives the phase detector output signal and that has an output signal that is inputted into a loop filter that produces a filtered signal that is inputted into the voltage controlled oscillator together with the modulating signal.

8. The modulator according to claim 1, wherein the pre-emphasis unit comprises a digital-to-analog converter and a low pass filter of at least order two with damping factor having a value of less than one, the low pass filter being located between the digital-to-analog converter and the direct modulation synthesizer circuit.

9. The modulator according to claim 8, wherein the modulating signal outputted from the low pass filter to the direct modulation synthesizer circuit has two voltage levels.

10. The modulator according to claim 9, wherein the modulating signal has an overshoot if a given data bit is 1 and the data bit preceding the given data bit is 0;

and has undershoot if the given data bit is 0 and the data bit preceding the given data bit is 1.

11. The modulator according to claim 1, wherein the modulator is located in an in-vivo sensing device.

12. An in-vivo sensing device comprising a modulator for producing a modulated signal, the modulator comprising:

a direct modulation synthesizer circuit;

a reference frequency oscillator for providing an input reference signal to the direct modulation synthesizer circuit for locking a carrier frequency to a stable frequency;

a pre-emphasis unit for receiving data bits and for producing a modulating signal for direct modulation of the direct modulation synthesizer circuit, the modulating signal having data bit dependent voltage levels.

13. The in-vivo sensing device according to claim 12, wherein the pre-emphasis unit is a digital-to-analog converter and each voltage level of the modulating signal is a function of the bit values of a given data bit and at least of the data bit preceding the given data bit.

14. The in-vivo sensing device according to claim 12, comprising an imager, one or more illumination sources and an optical system.

15. A method for producing a modulated signal, comprising:

providing a direct modulation synthesizer circuit;

inputting a reference signal having a given frequency to the direct modulation synthesizer circuit for locking a carrier frequency to a stable frequency;

inputting a modulation signal to the direct modulation synthesizer circuit, the modulation signal having data bit dependent voltage levels; and

outputting the modulated signal from the direct modulation synthesizer circuit.

16. The method according to claim 15, wherein the modulation signal is provided by a pre-emphasis unit that receives data bits as input and the modulated signal is a CPFSK signal.

17. The method according to claim 16, wherein the pre-emphasis unit is a digital-to-analog converter and each voltage level of the modulating signal is a function of the bit values of a given data bit and of the data bit preceding the given data bit.

18. The method according to claim 17, wherein the modulating signal has at least four voltage levels.

19. The method according to claim 18, wherein the at least four voltage levels are:

V0, if the given data bit is “

0” and

the preceding data bit is “

0”

;

V0-δ

V, if the given data bit is “

0” and

the preceding data bit is “

1”

;

V1, if the given data bit is “

1” and

the preceding data bit is “

1”

; and

V0+δ

V, if the given data bit is “

0” and

the preceding data bit is “

1”

;

where V1 and V0 are standard bit-voltage levels and V1 is greater that V0, and δ

V is a positive voltage enhancement value by which the standard bit-voltage levels are altered by the pre-emphasis unit.

20. The method according to claim 15, wherein the direct modulation synthesizer circuit comprises a voltage controlled oscillator, into which the modulating signal is inputted, a phase detector that produces a phase detector output signal by comparing the input reference signal with a local frequency signal outputted from a feedback frequency divider connected to the voltage controlled oscillator, a charge pump that receives the phase detector output signal and that has an output signal that is inputted into a loop filter that produces a filtered signal that is inputted into the voltage controlled oscillator together with the modulating signal.

21. The method according to claim 15, wherein the pre-emphasis unit comprises a digital-to-analog converter and a low pass filter of at least order two with damping factor having a value of less than one, the low pass filter being located between the digital-to-analog converter and the direct modulation synthesizer circuit.

22. The method according to claim 21, wherein the modulating signal outputted from the low pass filter to the direct modulation synthesizer circuit has two voltage levels.

23. The method according to claim 22, wherein the modulating signal has an overshoot if a given data bit is 1 and the data bit preceding the given data bit is 0;

and has undershoot if the given data bit is 0 and the data bit preceding the given data bit is 1.