Digital Phase Sensitive Detector

Project Title

Digital Phase Sensitive Detector

Project Area of Specialization Electrical/Electronic EngineeringProject Summary

We are basically making Digital Phase Sensitive Detectors that will help extract very low amplitude signals from signals having very high noise content.

Phase Sensitive Detector is a well-developed technique for measuring signals hidden in the noise. Nowadays, instrumentation for the latest technologies like THz detection, Magnetic Resonance, and Laser Applications use built-in DSP phase-sensitive detection.

A phase-sensitive detector is an instrument used to extract features of a sinusoidal component of a known frequency from a signal; accurate measurement may be made even when the small signal is obscured by noise sources many times larger. Given a measured signal and a frequency of interest, the instrument returns estimates of the amplitude and phase of the sinusoidal component of that frequency.

The digital technique eliminates many of the problems associated with analog phase-sensitive detectors like harmonic rejection, output offsets, limited dynamic reserves, and gains error. Fixed point mathematics will be used and it will be implemented using a DSP kit.

The achievement of this project will be a step in modern electronics systems development.

Project Objectives

The main objective of our project is to be able to improve the signal-to-noise ratio in a signal with high noise content. Also, we want to implement digitally using the processor. This will help us change filter coefficients much easier than analog ones.

• Understanding theory of analog and digital PSD.
• Deliverable Specifications.
• Implementation of digital PSD in MATLAB, using fixed-point and floating-point.
• Development of electronic hardware modules (low noise pre-amplifier, analog filters, ADC/DAC cards, and discriminators).
• Selection of Digital Signal Processor and DSP Kit.
• Understanding of selected Digital Signal Processor, DSP Kit, and Integrated Development Environment.
• Implementation of digital PSD modules (Reference signal generator, IQ demodulator, filters) in Digital Signal Processor.
• The interface of DSP Kit and electronics modules.

Project Implementation Method

General Idea:

It will be implemented using DSP Kit QQ2812. Data signal will be taken in real-time and after processing, the noise will be removed using the DSP kit mentioned above and the result will be shown on the function generator.

How does it work?
An input signal is given to our design through the Signal In node. After this, we have a low noise differential amplifier which is used to reduce external interference. Then we multiply the input signal with a gain to increase its magnitude however note that noise is also multiplied with the same gain and thus enhanced. Next, a local oscillator is used that generates a cosine wave and also passes it through a 90 degrees phase shift register to generate a sine wave. At this point, we have a sine and cosine wave and 2 multipliers, and also the input signal. What we do next is that one input to each multiplier is our signal after the gain block while the other input is cosine in one case and sine in the other.

The above is implemented in MATLAB using the DSP toolbox so far. Now, we will implement it practically on the DSP kit using assembly language. We will also make GUI using C-sharp language in Visual studio to make our project presentable. To check our results we will take signals from sound cards and function generators. 

Benefits of the Project

This project will help detect very low amplitude signals from signals that are covered with noise. Now, this is extremely helpful for mobile phone communication, GPS, and all sorts of communication.

Applications:

• Signal detection in RADAR (Military purposes)
• Voice recording systems to get a pure signal
• Improved Mobile phones services
• Intense electromagnetic interference while drilling prevents traditional analog phase-sensitive detection (APSD) from correctly acquiring the electromagnetic wave signal of logging while drilling (LWD).

After adding feedback in PSD, we can convert it into a Lock-in Amplifier which is an extension of our project. A number of important applications have been overlooked!

1. Absorption spectroscopy
2. A.C. bridges
3. Antenna patterns
4. Astronomical spectroscopy
5. Atomic absorption
6. Audio amplifier frequency response
7. Audiometry
8. Auger spectroscopy
9. Biomedical stimuli response measurements
10. Bode plots
11. Cochlear microphonics
12. Common mode rejection measurements
13. Complex impedance measurements
14. Contact potential measurements
15. Crosstalk in cables, amplifiers, etc.
16. C- V plotting
17. Cube interferometry
18. De Haas Van Alphen effect
19. Densitometry
20. Detective compensation
21. Displacement measurements
22. Doppler measurements
23. Dual-beam optical measurements
24. Eddy-current flaw testing
25. Edge shift in GaAs
26. Electrochemistry
27. Electroluminescence
28. Emission spectroscopy
29. E.P.R./e.s.r. spectroscopy
30. Filter calibration
31. Fluorescence spectroscopy
32. Frequency-response measurements
33. Frequency -shift measurements
34. Hall effect: single frequency
35. Hall effect: double frequency
36. Infra-red (near and far) spectroscopy
37. Interferometry
38. Klystron stabilization
39. Laser research
40. Line ripple measurement in the amplifier
41. power supplies
42. Magnetic-field measurements
43. Magnetometry
44. Magnetoresistance studies
45. Marx gauging
46. Mass spectroscopy
47. Microphone calibration
48. Microwave reflections, attenuation
49. Microwave spectroscopy
50. Moisture content measurement (C-G)
51. Molecular-beam spectroscopy
52. N.M.R. spectroscopy
53. N.O.R. spectroscopy
54. Nyquist plots
55. Operational amplifier gain measurement
56. Optical derivative measurements
57. Photometry
58. Plasma-physics research
59. Pyrometry
60. Radiometry
61. Raman spectroscopy
62. Ratiometric measurements
63. Resistance thermometry
64. R.F. measurements
65. Second sound
66. Seismic measurements
67. Semiconductor research
68. Source compensation
69. Spectrophotometry
70. Strain gauging
71. Stress-strain measurements
72. Temperature control
73. Temperature measurement
74. Torque measurements
75. Ultra-violet spectroscopy
76. Visible spectroscopy
77. Whistler signal measurements
78. Work function measurements
79. Young’s modulus
80. Zeeman effect

Technical Details of Final Deliverable

We will be using MATLAB for software implementation. This is because of the flexibility of use and wide range of applications of MATLAB. Now in order to program our project, we will be using the coding portion instead of Simulink so that we can see what is actually happening at each step and can review the errors accordingly.

Next, we will do all the coding using fixed-point mathematics after which we will check the whole algorithm using data from self-generated algos, microphone, and offline data from a function generator. After successful implementation and getting correct results, we will move on to the next step.

Next using C sharp, a GUI will be developed through which we will take real-time data. after getting the data we will not only perform the arithmetic operations on it like multiplication/ addition required in our project but we will also show the graphs and FFT of the data on the screen. 

In the end, we will be using DSP kit QQ2812 for the practical implementation of our project. We will use the application associated with it for the coding purpose i.e. code composer. And all the coding will be done in assembly language so that we can know from the basics what actually is happening. after this we will use real-time data to test our code and will successfully implement it.

Final Deliverable of the Project HW/SW integrated systemCore Industry TelecommunicationOther IndustriesCore Technology Internet of Things (IoT)Other TechnologiesSustainable Development Goals Industry, Innovation and InfrastructureRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	65000
DSP Kit QQ2812	Equipment	1	60000	60000
Stationery, printing and overheads	Miscellaneous	1	5000	5000