Wide Bandwidth 90 Degrees Phase Shifter For

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1 DIPARTIMENTO DI ELETTRONICA E INFORMAZIONE Wide Bandwidth 90 Degrees Phase Shifter for Lock-in Amplifiers Marco Vergani – Davide Bianchi Advising Professor: Giorgio Ferrari Analog Design Contest - Texas Instruments - 13/11/2012 90° Phase shifter for lock-in Amplifiers IMPEDANCE MEASUREMENTS BIO-APPLICATIONS REFERENCE cos(t ) INPUT SIGNAL MATERIAL SCIENCE x A cos(t  ) 2 A cos( ) 2 DC OUTPUT x A sin( ) 2 OPTICS From Hz to MHz frequency span 90° shifter r 90° shifte Typical architecture: local oscillator required Analog Design Contest - Texas Instruments - 13/11/2012 2 90° Phase Shifter Concept Precise 90° delay Single-pole filter 3 Amplitude Recovering Variable Gain Amplifier AIN - VIN + VOUT VGA Vg Signal processing Negative feedback loop Analog Design Contest - Texas Instruments - 13/11/2012 AIN 90° Phase Shifter Concept 4 Phase shift Vout VGA Vg Cint Rint Positive peak extraction - Negative peak extraction + Vin 90° Single pole circuit Specifications • 90° shift • Output amplitude independent to frequency Rint Proposed Solution • Precise 90° delay through single pole network • Input and output amplitude matching through a Variable Gain Amplifier and a DC negative feedback Analog Design Contest - Texas Instruments - 13/11/2012 Quasi-peak detector configuration Vout Rint Cint + Vin Rint Asynchronous peak sampling and discharge VGA Vg ripple on Vg Harmonic distortion increasing at low frequency Analog Design Contest - Texas Instruments - 13/11/2012 5 Synchronous peak comparison Vout Rint Cint - Vin + Rint Asynchronous peak sampling Synchronous discharge NO RIPPLE TO BE FILTERED Analog Design Contest - Texas Instruments - 13/11/2012 6 NO RIPPLE at any Vg frequency 90° Phase Shifter architecture OPA4354 TLC3704 LMH6503 C V φ1 + Phase shift R C V R φ3 C V + Vout 1 x1 +5V Close 2 φ2 SW1 Close SW2 Rint Rint SW3 Open Close Open φ1 Close Open x1 Cint Open Close Close C V C V Vg R Open Vout 90° Vin Time R Open C V - φ2 - 3 Vin Vin + VGA + Vout Wide bandwith CMOS OTA amplifiers Logic ±5V push-pull linear comparators Linear VGA amplifier - 3 ICs 7 CS1 Open Analog Design Contest - Texas Instruments - 13/11/2012 φ3 SW4 VA VB φ3 CS2 Experimental Results & Outlook 8 4 decades frequency span: 30Hz -300kHz Leakage from the switches Switches speed • Phase Error < ±3° • Amplitude precision limited by mismatched charge injection of the discrete MOSFETs switches. Designing of a complete IC embedded lock-in Reference x Input x Analog Design Contest - Texas Instruments - 13/11/2012 90° shifter DC Real OUT DC Imaginary OUT 9 Thank you for the attention Analog Design Contest - Texas Instruments - 13/11/2012 Amplitude error 10 VB Rint Cint Vout - VA + Vin Analog Design Contest - Texas Instruments - 13/11/2012 Rint Vg Digital signal generation 11 Vin Time • Required to control the switches (discrete MOSFETs) • No external clock required: synchronous with the input signal Vout - Vout Vin φ1 Time R R φ3 + - R Open Time Vout 21 R +5V • Squared input sinusoids • Logic elaboration Analog Design Contest - Texas Instruments - 13/11/2012 312 + 23 Vin Open Close Close Open Open Open Close Close Close Close Open Open Close Close Open Open Open Close Close Open Open Close Close Open Open Close CloseClose Close Open Open Close 3 φ2 - Vout 1 Vin Open + OpenOpen Close