TinySA

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

• tinySA wiki
• R&L page

Attenuators

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

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

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

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

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

• Verify no shorts between centers and ground

30 dB Attenuator

• Pi Attenuator Calculator

• 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

• LTSPICE Simulation

20 dB Attenuator

• 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)

• LTSPICE Simulation

Measurements

No Stimulus

• 50 Ohm terminator on Low port

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