Low-noise driver and low-noise receiver for self-mix module

1. A system comprising:

a laser microphone comprising:

a self-mix interferometry unit, (i) to transmit via a laser transmitter at least one outgoing laser beam towards a human speaker, and (ii) to receive an optical feedback signal reflected from the human speaker, and (iii) to generate an optical self-mix signal by self-mixing interferometry of the at least one outgoing laser beam and the received optical feedback signal;

wherein the self-mix interferometry unit comprises a laser-diode and a photo-diode;

wherein the laser-diode is associated with a laser driver TX;

wherein the photo-diode is associated with a photodiode receiver;

wherein at least one of the laser driver TX and the photodiode receiver, implements integrally a mechanism for reducing noises;

wherein the laser driver TX comprises:

a Direct Current (DC) Digital-to-Analog Converter (DAC) to generate a Direct Current (DC) having a first bandwidth;

a Modulator DAC to separately generate an Alternating Current (AC) having a second, different, bandwidth;

wherein the laser driver TX generates a drive current to the laser-diode, by utilizing (i) said Direct Current having the first bandwidth, and also (ii) said Alternating Current having the second, different, bandwidth.

2. The system of claim 1 ,

wherein the laser driver TX comprises:

a summing unit to combine (i) said Direct Current having the first bandwidth, and (ii) said Alternating Current having the second, different, bandwidth;

wherein the laser driver TX utilizes output of said summing unit, to generate said drive current supplied to the laser-diode.

3. The system of claim 1 ,

wherein the laser driver TX comprises:

an attenuator to attenuate said Alternating Current and to produce attenuated Alternating Current;

a summing unit to combine (i) said Direct Current having the first bandwidth, and (ii) said attenuated Alternating Current having the second, different, bandwidth;

wherein the laser driver TX utilizes output of said summing unit, to generate said drive current supplied to the laser-diode.

4. The system of claim 1 ,

wherein the laser driver TX comprises:

an attenuator to attenuate said Alternating Current and to produce attenuated Alternating Current, wherein the attenuator comprises at least one of: (I) a resistor, (II) an opposite-direction current;

a summing unit to combine (i) said Direct Current having the first bandwidth, and (ii) said attenuated Alternating Current having the second, different, bandwidth;

wherein the laser driver TX utilizes output of said summing unit, to generate said drive current supplied to the laser-diode.

5. The system of claim 1 ,

wherein the laser driver TX comprises:

an attenuator to attenuate said Alternating Current and to produce attenuated Alternating Current, wherein the attenuator comprises a cut filter;

a summing unit to combine (i) said Direct Current having the first bandwidth, and (ii) said attenuated Alternating Current having the second, different, bandwidth;

wherein the laser driver TX utilizes output of said summing unit, to generate said drive current supplied to the laser-diode.

6. The system of claim 1 ,

wherein the laser driver TX comprises:

an attenuator to attenuate said Alternating Current and to produce attenuated Alternating Current, wherein the attenuator comprises a cut filter;

a summing unit to combine (i) said Direct Current having the first bandwidth, and (ii) said attenuated Alternating Current having the second, different, bandwidth;

wherein said attenuator and said summing unit are an integrated unit;

wherein the laser driver TX utilizes output of said summing unit, to generate said drive current supplied to the laser-diode.

7. The system of claim 1 ,

wherein a ratio of (i) the first bandwidth of the Direct Current, to (ii) the second bandwidth of the Alternating Current, is smaller than 1/4.

8. The system of claim 1 ,

wherein a ratio of (i) the first bandwidth of the Direct Current, to (ii) the second bandwidth of the Alternating Current, is smaller than 1/8.

9. The system of claim 1 ,

wherein the first bandwidth of the Direct Current is in the range of 3.80 to 4.40 KHz; and

wherein the second bandwidth of the Alternating Current is in the range of 42 to 46 KHz.

10. The system of claim 1 ,

wherein the first bandwidth of the Direct Current is in the range of 3.0 to 5.0 KHz; and

wherein the second bandwidth of the Alternating Current is in the range of 69 to 76 KHz.

11. The system of claim 2 ,

wherein a ratio of (i) the first bandwidth of the Direct Current, to (ii) the second bandwidth of the attenuated Alternating Current, is smaller than 1/5.

12. The system of claim 2 ,

wherein a ratio of (i) the first bandwidth of the Direct Current, to (ii) the second bandwidth of the attenuated Alternating Current, is smaller than 1/9.

13. The system of claim 2 ,

wherein the first bandwidth of the Direct Current is in the range of 3.75 to 4.50 KHz; and

wherein the second bandwidth of the attenuated Alternating Current is in the range of 41 to 47 KHz.

14. The system of claim 2 ,

wherein the attenuator comprises a Low Pass Filter (LPF) that provides an attenuation factor of:

H

⁡

(

n

)

=

1

1

+

n

2

wherein harmonies in a Fourier expansion of the attenuated signal are proportional to 1/n,

wherein “n” is the number of harmony;

wherein an input of the LPF receives an input having harmonies according to the following formula:

A ( n )=√{square root over (1+ n 2 )}/ n

15. The system of claim 2 ,

wherein the attenuator comprises a Low Pass Filter (LPF) that provides an attenuation factor of:

H ( n )

wherein harmonies in a Fourier expansion of the required signal are F(n),

wherein “n” is the number of harmony;

wherein an input node of the LPF receives an input having harmonies according to the following formula:

A ( n )= F ( n )/ H ( n )

wherein the harmonies at an output node of the LPF correspond to the required signal A(n).

16. The system of claim 1 ,

wherein the photo-diode receiver comprises a hardware demodulation unit to perform hardware-based signal demodulation prior to Analog-to-Digital Conversion (ADC).

17. A system comprising:

a laser microphone comprising:

a self-mix interferometry unit, (i) to transmit via a laser transmitter at least one outgoing laser beam towards a human speaker, and (ii) to receive an optical feedback signal reflected from the human speaker, and (iii) to generate an optical self-mix signal by self-mixing interferometry of the at least one outgoing laser beam and the received optical feedback signal;

wherein the self-mix interferometry unit comprises a laser-diode and a photo-diode;

wherein the laser-diode is associated with a laser driver TX;

wherein the photo-diode is associated with a photodiode receiver;

wherein at least one of the laser driver TX and the photodiode receiver, implements integrally a mechanism for reducing noises;

wherein the photo-diode receiver comprises a Direct Current (DC) cancellation unit to remove a Direct Current component of an output signal of said photo-diode receiver.

18. The system of claim 1 ,

wherein the photo-diode receiver comprises a Direct Current (DC) cancellation unit to remove a Direct Current component of an output signal of said photo-diode receiver, by utilizing a current source with opposite direction prior to performing Trans-Impedance Amplification (TIA).

19. The system of claim 1 ,

wherein the photo-diode receiver comprises a Direct Current (DC) cancellation unit to remove a Direct Current component of an output signal of said photo-diode receiver, by utilizing a resistor, prior to performing Trans-Impedance Amplification (TIA).

20. The system of claim 1 ,

wherein the photo-diode receiver comprises a Trans-Impedance Amplification (TIA) unit to amplify a signal that consists of (i) self-mixed signal component, and (ii) modulation component, wherein said signal already excludes any Direct Current (DC) component prior to entering said Trans-Impedance Amplification (TIA) unit.

21. A system comprising:

a laser microphone comprising:

a self-mix interferometry unit, (i) to transmit via a laser transmitter at least one outgoing laser beam towards a human speaker, and (ii) to receive an optical feedback signal reflected from the human speaker, and (iii) to generate an optical self-mix signal by self-mixing interferometry of the at least one outgoing laser beam and the received optical feedback signal;

wherein the self-mix interferometry unit comprises a laser-diode and a photo-diode;

wherein the laser-diode is associated with a laser driver TX;

wherein the photo-diode is associated with a photodiode receiver;

wherein at least one of the laser driver TX and the photodiode receiver, implements integrally a mechanism for reducing noises;

wherein the photo-diode receiver removes a Direct Current component of an output signal of said photo-diode receiver, prior to digitization of said output signal.

22. The system of claim 1 ,

wherein the laser driver TX comprises:

a summing unit to combine (i) said Direct Current having the first bandwidth, and (ii) said Alternating Current having the second, different, bandwidth;

wherein the laser driver TX utilizes output of said summing unit, to generate said drive current supplied to the laser-diode;

wherein the photo-diode receiver comprises a Direct Current (DC) cancellation unit to remove a Direct Current component of an output signal of said photo-diode receiver prior to performing Trans-Impedance Amplification (TIA).

23. The system of claim 1 , further comprising at least one acoustic microphone; wherein the system is a hybrid acoustic-and-optical sensor.

24. The system of claim 17 , further comprising at least one acoustic microphone; wherein the system is a hybrid acoustic-and-optical sensor which is comprised in a device selected from the group consisting of: a laptop computer, a smartphone, a tablet, a portable electronic device, a vehicular audio system.