A Termination Insensitive Amplifier for Bidirectional Transceivers
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Contents
A Termination Insensitive Amplifier for Bidirectional Transceivers
Through Hole Version
Surface Mount Version
W7ZOI Design
- Paper - A Termination Insensitive Amplifier for Bidirectional Transceivers - W7ZOI (Wes Hayward) design
- Transistor Models and the Feedback Amplifier
- Termination Insensitive - input impedance that does not depend upon the output load
- Bi-directional - amplifiers in both directions
- 50 ohms in/out
- BNC or SMA Connectors
- Transformer-less
- Power applied to one half at a time - determines signal flow direction
- ~30 mA per side
- SMT or Through Hole versions
- SMT version fits in 80x50x20mm aluminum case
W7ZOI Schematic
* Use
- Between RF/LO mixer (IF output/input) and crystal filter
- Between Crystal Filter and Product Detector / Balanced Modulator
Schematic in KiCAD
- Schematic (pdf file)
- Single channel
- With SPICE directives
- Both channels
- With SPICE directives
NGSPICE Simulation
- NGSPICE run from KiCAD
- +24 dB @12V
- 2N3904 Alternate Node Sequence (MMBT3903 - SOT23)
- KiCAD order 1 2 3 is the SPICE normal order
- NGSPICE order: 3 1 2
- Closely matches
- Across Band
Measurements
- Powering only L-R side
- 30 mA power supply current
- 12V
NanoVNA Measurements (Through-hole)
Left-to-right flow
- At 9 MHz
- S21 - sweep 1-30 MHz
- S11 VSWR - sweep 1-30 MHz
Right-to-Left flow
- At 9 MHz
- S21 - sweep 1-30 MHz
- S11 VSWR - sweep 1-30 MHz
NanoVNA Measurements (SMT)
- Re = 150
- A bit more gain
Left-to-right flow
- At 9 MHz
- S21 - sweep 1-30 MHz
- S11 VSWR - sweep 1-30 MHz
Right-to-Left flow
- At 9 MHz
- S21 - sweep 1-30 MHz
- S11 VSWR - sweep 1-30 MHz
CAD
Through Hole CAD
- 2.4" x 2.4"
- 2.0 hole center-to-center
SMT CAD
Test Procedure
Test Equipment
- Unit Under Test (UUT)
- NanoVNA
- 30 dB attenuator tap on Triple attenuator
- RF Demo Kit
- (3) SMA to SMA Male:Male cables
- Benchtop Power Supply DPS3005
- 12V Power Supply
- Current Limit set at 100 mA
Calibrate NanoVNA
- Cable #1 from RF out of NanoVNA (upper jack) to left side of 30 dB attenuator
- Cable #2 from right side of 30 dB attenuator to left side of RF Demo Kit
- Multiple positions for open, through, and short
- Cable #3 from right side of RF Demo Kit to input of NanoVNA (lower jack)
Test UUT
- Replace RF Demo Kit with UUT
- Test each direction at a time
- Power up Left to right, test
- Power up right to left, test
- Should show gain of about 20 dB at 10 MHz
Enclosure
- The SMT version is designed to fit in a 80x50x20mm Extruded Aluminum Project Box
- W7ZOI_TIA_SMD_CUTOUTS.pdf Panel marking template
Videos
Assembly Sheet
- W7ZOI TIA Assembly Sheet - Rev 1 - Through-hole version
- W7ZOI TIA SMT Assembly Sheet - Rev 1 - SMT version
