1 / 23

The Active Circulator

The Active Circulator. Isolation. V tr. V rx. V ant. Insertion. Specs Insertion Loss < -.5dB Isolation > -15db Frequency > 30 MHz 10W < Power < 50W. 3 NPN Circulator. Small Signal Diagram Purpose: Design a CCW circulator out of a 3-port, 3-transitor network.

sara-craig
Download Presentation

The Active Circulator

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Active Circulator Isolation Vtr Vrx Vant Insertion Specs Insertion Loss < -.5dB Isolation > -15db Frequency > 30 MHz 10W < Power < 50W

  2. 3 NPN Circulator Small Signal Diagram Purpose: Design a CCW circulator out of a 3-port, 3-transitor network. Design: Construct h-parameter admittance matrix. Then find transistor parameters that make it behave like a circulator.

  3. Tanaka-Lee Schematic

  4. Experiment Results Operating Points: Vtrs= 100mV, f = 1kHz Results: Isolation = -19.33dB, Insertion Loss = -1.012dB Power = 1.13mW

  5. Simulation

  6. Considerations Cons: Bias Current Vbe Overdrive Rpi Sensitivity Pros: High Frequency Parameters Easily Calculated Symmetric

  7. Basic Model Purpose: A more “flexible” op-amp Design Specs: V1=V2=7.5V V3=-0.8V IR1=IR2=1mA

  8. 3-Port Scheme • Idea from the topology in the proposal

  9. Continued: Simulation Result Insertion Loss: -1.41DB Need simplification for analysis purpose.

  10. Simplified Topology

  11. Continued-Simulation Result

  12. Continued-Small Signal Test Signal From the Transmitter (f_input=1kHz) Vtransmitter=49.60mV Vantenna=25.2mV Vreceiver=1.84mv F(-3db)=298.7kHz Insertion Loss=-6DB Isolation Loss=-31.50DB Signal From the Receiver (f_input=1kHz) Vantenna=49.8mV Vreceiver=43mv Vtransmitter=0mV F(-3db)=805.3kHz Insertion Loss=-1.27DB Isolation Loss=-Inf

  13. Continued Large Signal Test Signal From the Transmitter (f_input=1kHz) The largest input signal before distortion is 11.5V Signal From the Receiver (f_input=1kHz) The largest input signal before distortion is 4.0V Clipping Distortions

  14. Continued-Bandwidth

  15. Basic Model Purpose: To understand the limiting factors involved with Op-Amps used in this topology 3-Port, Symmetric, Op-Amp Topology Method: Push the limits of readily available LM741 Op-Amps, to better understand the capability of this topology.

  16. Testing Results Small Signal Test: Ro: 11k VBIAS: +/- 20 DC Vtr : 250mVpp Vant(-3dB) occurred at 180 kHz Large Signal Test: Ro: 11k VBIAS: +/- 20 DC Vtr : 17Vpp Vant(-3dB) never occurred, clipping Clipping occurred at 8kHz, yielding calculated slew rate of .427 V/us Isolation: Ideal operating condition, 1 Vpp @ 1 kHz : -23.7 dB Small Signal max frequency: -10.17 dB Large Signal max frequency: -29.19 dB

  17. Alternative Model This model was determined to be too finicky with resistance mismatching. Far too much distortion was found in the experiments, and the topology was abandoned The input was a sinusoid…

  18. Topology Modeled for our purpose, not a true circulator

  19. Simulation Results

  20. Testing Results • Small Signal Test: Ro: 11k VBIAS: +/- 20 DC Vtr : 200mVpp Vant(-3dB) occurred at 224 kHz • Large Signal Test: Ro: 11k VBIAS: +/- 20 DC Vtr : 1Vpp Vant(-3dB) occurred at 200kHz • Dr. Young mentioned frequency should be our focus, not power, • hence, the significantly smaller large signal voltage. • Isolation: Ideal operating condition, 1 Vpp @ 1 kHz : -25.03 dB Small Signal max frequency: -29.05 dB Large Signal max frequency: -49.11 dB

  21. Summary • Pros: Simplest design Specifications easiest realized • Cons: Voltage divider Frequency limited to available Op Amps Heating Issue Phase shift at frequency limits

  22. Conclusion There are many paths we can take. Pursue high power: Op/Diff amp design Pursue high frequency: 3 transistor Pursue a compromise… We recommend the Op/Diff amp design because it is the most realizable.

  23. Questions?

More Related