Difference between revisions of "TinySA"

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* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
 
* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
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Revision as of 16:49, 6 September 2021

TinySA - Spectrum Analyzer - Specifications

User interface

  • Display resolution 320*240 pixels
  • Screen diagonal 2.8"
  • 16 bits per RGB pixels
  • Resistive touch control
  • Jog switch control
  • USB serial port control
  • Optional TTL USART port (SW not yet implemented) on the internal PCB
  • Linear power supply to avoid switching noise.

The input/output specification of the tinySA is split over the 4 modes

Low input mode spec

  • Input frequency range from 100kHz to 350MHz
  • Input impedance 50 ohm when input attenuation set to 10dB or more.
  • Selectable manual and automatic input attenuation between 0dB and 31dB in 1 dB steps
  • Absolute maximum input level without attenuation of +10dBm
  • Absolute maximum input power with 30dB attenuation of +20dBm for short period
  • Input Intercept Point of third order modulation products (IIP3) with 0dB attenuation of +15dBm
  • 1dB compression point at +2dBm with 0dB attenuation
  • Power detector resolution of 0.5dB and linearity versus frequency of +/-1dB
  • Absolute power level accuracy after power level calibration of +/- 1dB
  • Lowest discernible signal using a resolution bandwidth of 30kHz of -102dBm
  • Frequency accuracy equal to the selected resolution bandwidth
  • Phase noise of -90dB/Hz at 100kHz offset and -115dB/Hz at 1MHz offset
  • Spur free dynamic range when using a 30kHz resolution bandwidth of 70dB
  • Manually selectable resolution filters of 3, 10, 30, 100, 300, 600kHz. Automatic selection of one of the 57 resolution filters.
  • On screen resolution of 145 or 290 measurement points.
  • Scanning speed of over 1000 points/second using largest resolution filters.
  • Automatic optimization of actual scanning points to ensure coverage of the whole scan range regardless of the chosen resolution bandwidth
  • Spur suppression option for assessing if certain signals are internally generated or actually present in the input signal

High input mode spec

  • Input frequency range from 240MHz to 960MHz
  • As there is no input bandfilter strong signals outside the 240MHz to 960MHz range can cause distortion of the in band signals
  • Absolute maximum input level without attenuation of +10dBm
  • Input Intercept Point of third order modulation products (IIP3) of -5dBm
  • 1dB compression point at -6dBm with 0dB attenuation
  • Power detector resolution of 0.5dB and linearity versus frequency of +/-1dB
  • Absolute power level accuracy after power level calibration of +/- 1dB
  • Lowest discernible signal using a resolution bandwidth of 30kHz of -115dBm
  • Frequency accuracy equal to the selected resolution bandwidth
  • Spur free dynamic range when using a 30kHz resolution bandwidth of 50dB
  • Selectable (automatic and manual) resolution filters of 3, 10, 30, 100, 300 and 600kHz
  • Optional 25dB to 40dB frequency dependent input attenuator. The power level error with this attenuator activated increases to +/- 15dB
  • On screen resolution of 145 or 290 measurement points.
  • Scanning speed of over 1000 points/second using largest resolution filters.
  • Automatic optimization of actual scanning points to ensure coverage of the whole scan range regardless of the chosen resolution bandwidth

Low output mode spec

  • Sinus output with harmonics below -40dB of fundamental
  • Output frequency range from 100kHz to 350MHz
  • Output level selectable in 1dB steps between -76dBm and -6dBm
  • Optional AM, narrow FM and wide FM modulation or slow sweep over selectable frequency span

High output mode spec

  • Square wave output
  • Output frequency range from 240MHz to 960MHz
  • Output level selectable in variable increments between -38dBm and +13dBm
  • Optional narrow FM and wide FM modulation or slow sweep over selectable frequency span

Reference generator spec

  • Optional square wave output with fundamental at -25dBm connected to high input/output
  • Frequency can be set to 1MHz, 2MHz, 4MHz, 10MHz, 15MHz or 30MHz.

Battery spec

  • Charging time max 1 hour on 500mA minimum USB port or USB charger
  • Operation on fully charged battery for at least 2 hours
  • Maximum input level
    • 0 dBm = 1 mW
    • dBm = 10*LOG(milliwatts)
    • -10 dBm = 0.1 mW
    • +10dBm = 10 mW
    • +20dBm = 1000 mW
  • 3.3V at 50 Ohm = 0.2178W
    • 217.8 mW = 23.4 dBm

References

Attenuators

Chart mW vs dbM.PNG

Construction

  • Single side copper clad PCB
    • Approx 2"x1"
  • Clean with steel wool
  • Solder SMA connectors
    • Use large alligator clips to hold while soldering
    • Solder on sides only

Atten 01 SMAs 720px.jpg

  • Cut "T" Shaped pads
    • I used nibbler
  • Center fits between connector ground pins
  • Glue down pads with Superglue

Atten 02 Pads 720px.jpg

  • Solder center pin with big solder blob
    • A bit too high for direct contact
  • Verify raised pad does not short to ground

Atten 03 Solder CenterPads 720px.jpg

  • Solder side resistor(s)
  • Leave room for center resistor(s)

Atten 04 Solder Side Resistors 720px.jpg

  • Measure side resistors from pad to ground
  • Should match value
  • Solder center resistor(s)

Atten 05 Solder Center Resistors 720px.jpg

  • Verify no shorts between centers and ground

30 dB Attenuator

Atten30dB P116-720px.jpg

30dB Attenuator.PNG

  • Built
    • Standard 5% resistor values
    • R1 = 820 in parallel with 22K = 790.6 ohms
    • R2 = 2 paralleled 120 Ohm 1/4W resistors paralleled with 470 ohms = 53.2 ohms
    • Flat from 0-30 MHz
    • Measured attenuation is flat
      • -30.01dB at 1 MHz
      • -30.24dB at 30 MHz
    • Input Impedance - 53.1 ohms, 21.3nF
    • SWR 1.06
    • 1/2W max (5VDC max, 0 ohm source)
  • NanoVNA scan data

30dB Attenuator NanoVNA Setup Curve 900MHz.PNG

30dB Attenuator NanoVNA Data 900MHz.PNG

  • LTSPICE Simulation

LTSPice 30dB.PNG

20 dB Attenuator

20dB Attenuator.PNG

  • Build
    • Standard 5% resistor values
    • R1 = 2 of 510 in parallel also in parallel with 8.2K = 247.3 ohms
    • R2 = 2 paralleled 150 Ohm 1/2W resistors paralleled with 330 ohms = 61.11 ohms
    • Flat from 0-30 MHz
    • Measured attenuation is flat
    • Input Impedance - tbd ohms, tbd nF
    • SWR tbd
    • 1W max (8.6 V max, 0 ohm source)

20dB Attenuator NanoVNA Setup Curve 900MHz.PNG

20dB Attenuator NanoVNA Data 900MHz.PNG

  • LTSPICE Simulation

LTSPice 20dB.PNG

Measurements

No Stimulus

  • 50 Ohm terminator on Low port

Tiny-SA App v1.1.19.20.PNG

VFO-003

  • VFO-003
  • 20 MHz
  • 3.3V square wave drive
  • Rich odd harmonic content
  • Lots of other noise
  • Using 20 dB attenuator (from above)
  • 1-301 MHz

VFO-002 20dB 001.PNG

Videos