https://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&feed=atom&action=historyPhase-Sensitive Detection - Revision history2024-03-29T12:18:59ZRevision history for this page on the wikiMediaWiki 1.35.9https://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9657&oldid=prevEricN: /* '''Example Circuit''' */2009-01-07T01:59:29Z<p><span dir="auto"><span class="autocomment">'''Example Circuit'''</span></span></p>
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<td class="diff-context diff-side-deleted"><div>== '''Example Circuit''' ==</div></td>
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<td class="diff-context diff-side-deleted"><div>The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is Max4526.</div></td>
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<td class="diff-context diff-side-added"><div>The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is Max4526.</div></td>
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<td class="diff-deletedline diff-side-deleted"><div><a name="movedpara_3_1_lhs"></a>[[Image:phase_sensitive_detection_ckt.jpg|right|Circuit diagram of the phase sensitive detector]|thumb|350px]]</div></td>
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<td class="diff-context diff-side-deleted"><div>Here is an illustration of the working principle of the example circuit.</div></td>
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<td class="diff-context diff-side-deleted"><div>(1)The magnified signal from the X+ and X- pins of the photodiode.</div></td>
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<td class="diff-context diff-side-added"><div>(1)The magnified signal from the X+ and X- pins of the photodiode.</div></td>
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</table>EricNhttps://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9655&oldid=prevEricN: /* '''Example Circuit''' */2009-01-07T01:57:02Z<p><span dir="auto"><span class="autocomment">'''Example Circuit'''</span></span></p>
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</table>EricNhttps://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9654&oldid=prevEricN: /* '''Example Circuit''' */2009-01-07T01:56:30Z<p><span dir="auto"><span class="autocomment">'''Example Circuit'''</span></span></p>
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<td class="diff-addedline diff-side-added"><div>[[Image:<ins class="diffchange diffchange-inline">phase_sensitive_detection_ckt|right|Circuit diagram</ins> of<ins class="diffchange diffchange-inline"> the</ins> phase sensitive <ins class="diffchange diffchange-inline">detector]|thumb|350px</ins>]]</div></td>
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</table>EricNhttps://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9296&oldid=prevZhao: /* '''Method''' */2008-12-11T23:39:58Z<p><span dir="auto"><span class="autocomment">'''Method'''</span></span></p>
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<td class="diff-context diff-side-deleted"><div>A phase sensitive detection can be split into 6 stages:</div></td>
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<td class="diff-deletedline diff-side-deleted"><div>1. Modulation: Modulate the signal at a certain frequency.</div></td>
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<td class="diff-addedline diff-side-added"><div><ins class="diffchange diffchange-inline">'''</ins>1.<ins class="diffchange diffchange-inline">'''</ins> Modulation: Modulate the signal at a certain frequency.</div></td>
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<td class="diff-deletedline diff-side-deleted"><div>2. Pre-amplification: A high-speed amplifier required to amplify the signal (along with the noise) to a suitable level for succeeding circuit. We can also stick in a high pass filter (can be a capacitor) after amplification, just to eliminate the DC portion of the noise.</div></td>
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<td class="diff-addedline diff-side-added"><div><ins class="diffchange diffchange-inline">'''</ins>2.<ins class="diffchange diffchange-inline">'''</ins> Pre-amplification: A high-speed amplifier required to amplify the signal (along with the noise) to a suitable level for succeeding circuit. We can also stick in a high pass filter (can be a capacitor) after amplification, just to eliminate the DC portion of the noise.</div></td>
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<td class="diff-deletedline diff-side-deleted"><div>3. Reference circuit: Usually a pulse wave at the modulating frequency, which can be from a function generator, or a 555 timer, or PIC, etc.</div></td>
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<td class="diff-addedline diff-side-added"><div><ins class="diffchange diffchange-inline">'''</ins>3.<ins class="diffchange diffchange-inline">'''</ins> Reference circuit: Usually a pulse wave at the modulating frequency, which can be from a function generator, or a 555 timer, or PIC, etc.</div></td>
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<td class="diff-deletedline diff-side-deleted"><div>4. Multiplier: At this stage, we multiply the pre-amplified signal (along with the noise) with the reference signal. One easy way to do multiplication is suggested here: we use the reference signal to turn on and off an analog switch periodically, and let the modulated input signal pass the analog switch. So when the switch is ON (meaning connected to the input pin of the integrator), the output is ‘<math>input \times 1</math>’, and when the switch is OFF (meaning connected to the ground), the output is ‘<math>input \times 0</math>’. </div></td>
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<td class="diff-addedline diff-side-added"><div><ins class="diffchange diffchange-inline">'''</ins>4.<ins class="diffchange diffchange-inline">'''</ins> Multiplier: At this stage, we multiply the pre-amplified signal (along with the noise) with the reference signal. One easy way to do multiplication is suggested here: we use the reference signal to turn on and off an analog switch periodically, and let the modulated input signal pass the analog switch. So when the switch is ON (meaning connected to the input pin of the integrator), the output is ‘<math>input \times 1</math>’, and when the switch is OFF (meaning connected to the ground), the output is ‘<math>input \times 0</math>’. </div></td>
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<td class="diff-deletedline diff-side-deleted"><div><a name="movedpara_8_1_lhs"></a>5. Integrator (demodulation): Let the multiplied signal pass through an integrator. The multiplied signal can have a lot of components – almost all of them will become zero after integration (see explanation in the mathematical model), but the one which is the product of the modulated signal and the reference signal will remain, because they are at the same frequency and the same phase angle. This is the essence of phase sensitive detection – only the product of the two signals that are ‘in phase’ will remain after integration. ‘In phase’ means the two signals share common frequency and phase angle. We can also do amplification at the integration stage by sticking in a feedback resistor (see the example circuit diagram), just for convenience.</div></td>
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<td class="diff-deletedline diff-side-deleted"><div><a name="movedpara_8_3_lhs"></a>6. Low pass filter: After integration, the signal is recovered and demodulated to a DC output. However, it may not be a perfect DC voltage due to high frequency spikes that still exist. That’s why the low pass filter come into play.</div></td>
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<td class="diff-addedline diff-side-added"><div><a name="movedpara_10_0_rhs"></a><ins class="diffchange diffchange-inline">'''</ins>5.<ins class="diffchange diffchange-inline">'''</ins> Integrator (demodulation): Let the multiplied signal pass through an integrator. The multiplied signal can have a lot of components – almost all of them will become zero after integration (see explanation in the mathematical model), but the one which is the product of the modulated signal and the reference signal will remain, because they are at the same frequency and the same phase angle. This is the essence of phase sensitive detection – only the product of the two signals that are ‘in phase’ will remain after integration. ‘In phase’ means the two signals share common frequency and phase angle. We can also do amplification at the integration stage by sticking in a feedback resistor (see the example circuit diagram), just for convenience.</div></td>
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<td class="diff-addedline diff-side-added"><div><a name="movedpara_12_0_rhs"></a><ins class="diffchange diffchange-inline">'''</ins>6.<ins class="diffchange diffchange-inline">'''</ins> Low pass filter: After integration, the signal is recovered and demodulated to a DC output. However, it may not be a perfect DC voltage due to high frequency spikes that still exist. That’s why the low pass filter come into play.</div></td>
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</table>Zhaohttps://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9295&oldid=prevZhao: /* '''Example Circuit''' */2008-12-11T23:39:22Z<p><span dir="auto"><span class="autocomment">'''Example Circuit'''</span></span></p>
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<td class="diff-deletedline diff-side-deleted"><div>The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is <del class="diffchange diffchange-inline">Maxim 4056</del>.</div></td>
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<td class="diff-addedline diff-side-added"><div>The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is <ins class="diffchange diffchange-inline">Max4526</ins>.</div></td>
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</table>Zhaohttps://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9294&oldid=prevZhao: /* '''Overview''' */2008-12-11T23:38:11Z<p><span dir="auto"><span class="autocomment">'''Overview'''</span></span></p>
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<td class="diff-context diff-side-deleted"><div>One effective way to recover the small signal buried by large ambient noise is to use the so called phase sensitive detector, or lock-in amplifier. A phase sensitive detector achieves narrow bandwidth amplification by reducing the noise content at falling outside the interested bandwidth.</div></td>
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<td class="diff-context diff-side-added"><div>One effective way to recover the small signal buried by large ambient noise is to use the so called phase sensitive detector, or lock-in amplifier. A phase sensitive detector achieves narrow bandwidth amplification by reducing the noise content at falling outside the interested bandwidth.</div></td>
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<td class="diff-deletedline diff-side-deleted"><div>When the noise is white in nature, we can reduce its level of magnitude dramatically by limiting the bandwidth of detection, which includes the frequency occurring to the signal while excludes the frequencies occurring to the noise. Phase sensitive detection enables extremely narrow bandwidth detection (0.001Hz is normal). Typical application scenario is using electric transducers where the amplitude of noise is in mili volts and the signal falls into nano volt region. Sophisticated phase sensitive detector can extract signals buried in noise that is <del class="diffchange diffchange-inline">107</del> times larger in magnitude. </div></td>
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<td class="diff-addedline diff-side-added"><div>When the noise is white in nature, we can reduce its level of magnitude dramatically by limiting the bandwidth of detection, which includes the frequency occurring to the signal while excludes the frequencies occurring to the noise. Phase sensitive detection enables extremely narrow bandwidth detection (0.001Hz is normal). Typical application scenario is using electric transducers where the amplitude of noise is in mili volts and the signal falls into nano volt region. Sophisticated phase sensitive detector can extract signals buried in noise that is <ins class="diffchange diffchange-inline"><math>10^7</math></ins> times larger in magnitude. </div></td>
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<td class="diff-context diff-side-deleted"><div>In this article, we focus on a quick and easy method of building a phase sensitive detector from op-amps and analog switches.</div></td>
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<td class="diff-context diff-side-added"><div>In this article, we focus on a quick and easy method of building a phase sensitive detector from op-amps and analog switches.</div></td>
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<td class="diff-context diff-side-deleted"><div>== '''Mathematical model''' ==</div></td>
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<td class="diff-context diff-side-added"><div>== '''Mathematical model''' ==</div></td>
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</table>Zhaohttps://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9293&oldid=prevZhao: /* '''Commercial phase sensitive detectors''' */2008-12-11T23:37:31Z<p><span dir="auto"><span class="autocomment">'''Commercial phase sensitive detectors'''</span></span></p>
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<td class="diff-context diff-side-deleted"><div>This link below provides some useful information on commercially available phase sensitive detectors, or lock-in amplifiers.</div></td>
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<td class="diff-context diff-side-added"><div>This link below provides some useful information on commercially available phase sensitive detectors, or lock-in amplifiers.</div></td>
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<td class="diff-deletedline diff-side-deleted"><div>[http://www.thinksrs.com/products/SR810830.htm]http://www.thinksrs.com/products/SR810830.<del class="diffchange diffchange-inline">htmSRS series Lock-in amplifiers</del></div></td>
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<td class="diff-addedline diff-side-added"><div>[http://www.thinksrs.com/products/SR810830.htm]<ins class="diffchange diffchange-inline">SRS series Lock-in amplifiers: </ins>http://www.thinksrs.com/products/SR810830.<ins class="diffchange diffchange-inline">htm</ins></div></td>
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</table>Zhaohttps://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9292&oldid=prevZhao: /* '''Commercial phase sensitive detectors''' */2008-12-11T23:36:54Z<p><span dir="auto"><span class="autocomment">'''Commercial phase sensitive detectors'''</span></span></p>
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<td class="diff-context diff-side-deleted"><div>This link below provides some useful information on commercially available phase sensitive detectors, or lock-in amplifiers.</div></td>
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<td class="diff-context diff-side-added"><div>This link below provides some useful information on commercially available phase sensitive detectors, or lock-in amplifiers.</div></td>
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<td class="diff-deletedline diff-side-deleted"><div>[http://www.thinksrs.com/products/SR810830.htm]<del class="diffchange diffchange-inline">SRS</del> series Lock-in amplifiers</div></td>
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<td class="diff-addedline diff-side-added"><div>[http://www.thinksrs.com/products/SR810830.htm]<ins class="diffchange diffchange-inline">http://www.thinksrs.com/products/SR810830.htmSRS</ins> series Lock-in amplifiers</div></td>
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</table>Zhaohttps://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9290&oldid=prevZhao: /* '''Example Circuit''' */2008-12-11T23:33:50Z<p><span dir="auto"><span class="autocomment">'''Example Circuit'''</span></span></p>
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<td class="diff-context diff-side-deleted"><div>The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is Maxim 4056.</div></td>
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<td class="diff-context diff-side-added"><div>The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is Maxim 4056.</div></td>
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<td class="diff-context diff-side-deleted"><div>[[Image:schematic of phase sensitive detection.jpg]]</div></td>
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</table>Zhaohttps://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9289&oldid=prevZhao: /* '''Example Circuit''' */2008-12-11T23:32:28Z<p><span dir="auto"><span class="autocomment">'''Example Circuit'''</span></span></p>
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<td class="diff-context diff-side-deleted"><div>The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is Maxim 4056.</div></td>
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<td class="diff-context diff-side-added"><div>The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is Maxim 4056.</div></td>
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<td class="diff-context diff-side-deleted"><div>[[Image:schematic of phase sensitive detection.jpg]]</div></td>
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<td class="diff-context diff-side-deleted"><div>Here is an illustration of the working principle of the example circuit.</div></td>
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<td class="diff-context diff-side-deleted"><div>(1)The magnified signal from the X+ and X- pins of the photodiode.</div></td>
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<td class="diff-context diff-side-added"><div>(1)The magnified signal from the X+ and X- pins of the photodiode.</div></td>
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</table>Zhao