Mixer Performance Simulations

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Revision as of 09:27, 7 April 2011 by Neihart (Talk | contribs) (Linearity using IIP3)

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Conversion Gain

  • You must first instance ports for the RF, LO, and IF ports of the mixer (analogLib -> Sources -> Independent -> port). If your mixer requires differential inputs/outputs then refer to the separate tutorial on how to drive differential signals.
  • Edit the properties of the RF port
    • Set the Resistance to 50 Ω and the Port number to 1
    • Set the Source type to dc
    • Click OK
  • Edit the properties of the LO port
    • Set the Resistance to 50 Ω
    • Set the Port number to 2
    • Set the Source type to sine
    • Fill in the flo for the Frequency name 1
    • Frequency 1 should be either 2.2 GHz (for low-side injection) or 2.6 GHz (for high-side injection)
      • This is the frequency of the local oscillator signal
    • Fill in Amplitude 1 (Vpk) with the amplitude of your LO signal
    • Click OK
  • Edit the IF port
    • Set the Resistance to 50 Ω and the Port number to 3
    • Set the Source type to dc
    • Click OK
  • In the Analog Design Environment, enable the pss analysis
    • Verify that only flo is displated in the Fundamental tones section
    • Select Beat Frequency and click Auto Calculated
    • Select Number of harmonics under Output harmonics and fill in the value of 0
      • This number of ourput harmonics is required by the pxf analysis that we will use to perform the conversion gain simulation
    • Set the Accuracy Defaults (errpreset) to conservative
    • Set the Additional Time for Stabalizatoin (tstab) to a time larger that the settling time of your system
      • Run a short tran simulation to find the time when all of the voltages in your mixer have settled and there is no "ringing"
    • Click OK
  • In the Analog Design Environment, select pxf analysis (pxf stands for periodic transfer function)
    • Set Sweep type to default
    • Under Output Frequency Sweep Range (Hz) select Start-Stop
    • Set Start to 1 MHz and Stop to 400 MHz
  • Set the Sweep Type to Linear
    • Select Number of Steps and set the value to 1000
    • Set Sidebands to Maximum Sideband and enter the value 3
    • Under Output select probe and then selct the IF port
    • Click OK
  • Run the simulation
  • To view the results for the conversion gain simulatoin click Results -> Direct Plot -> Main Form ...
    • Set the Analysis to pxf
    • Set the Function to Voltage Gain
    • Set Sweep to sideband
    • Select sidebands -1 and 1 (hold down the ctrl key to select multiple sidebands)
      • This is the sideband that provides us the conversion gain of our RF frequency of interest
    • Set Modifier to dB20
    • Click on the RF port in the schematic

LO Feed Through

  • You must first instance ports for the RF, LO, and IF ports of the mixer (analogLib -> Sources -> Independent -> port). If your mixer requires differential inputs/outputs then refer to the separate tutorial on how to drive differential signals.
  • Edit the properties of the RF port
    • Set the Resistance to 50 Ω and the Port number to 1
    • Set the Source type to sine
    • Enter frf for the Frequency name 1
    • Enter 2.4 GHz for Frequency 1
    • Enter prf for Amplitude 1 (dBm)
    • Click OK
  • Edit the properties of the LO port
    • Set the Resistance to 50 Ω
    • Set the Port number to 2
    • Set the Source type to sine
    • Fill in the flo for the Frequency name 1
    • Frequency 1 should be either 2.2 GHz (for low-side injection) or 2.6 GHz (for high-side injection)
      • This is the frequency of the local oscillator signal
    • Fill in Amplitude 1 (Vpk) with the amplitude of your LO signal
    • Click OK
  • Edit the IF port
    • Set the Resistance to 50 Ω and the Port number to 3
    • Set the Source type to dc
    • Click OK
  • In the Analog Design Environment, enable the pss analysis
    • Verify that both frf and flo are displated in the Fundamental tones section
    • Select Beat Frequency and click Auto Calculated
      • The beat frequency should be 200 MHz (your IF frequency)
    • Select Number of harmonics under Output harmonics and fill in the value of 15
    • Set the Accuracy Defaults (errpreset) to conservative
    • Set the Additional Time for Stabalizatoin (tstab) to a time larger that the settling time of your system
      • Run a short tran simulation to find the time when all of the voltages in your mixer have settled and there is no "ringing"
    • Click OK
  • Run the simulatoin
  • To view the results for the conversion gain simulatoin click Results -> Direct Plot -> Main Form ...
    • Set the Analysis to pss
    • Set the Function to Voltage
    • Choose Differential Nets under the Select optoin if you have a differential output
    • Set Sweep to spectrum
    • Set Signal Level to Peak
    • Choose dB20 for the Modifier
    • Select the IF output nets on the schematic to plot the result
    • Place a marker on the harmonic that appears at you LO frequency (2.2 GHz for low-side injection or 2.6 GHz for high-side injection)and read the value

Noise Figure

  • You must first instance ports for the RF, LO, and IF ports of the mixer (analogLib -> Sources -> Independent -> port). If your mixer requires differential inputs/outputs then refer to the separate tutorial on how to drive differential signals.
  • This simulation does not require an IF port so remove the IF port (and accompanying balun circuitry if you have a differential IF signal)
  • Edit the properties of the RF port
    • Set the Resistance to 50 Ω and the Port number to 1
    • Set the Source type to dc
    • Click OK
  • Edit the properties of the LO port
    • Set the Resistance to 50 Ω
    • Set the Port number to 2
    • Set the Source type to sine
    • Fill in the flo for the Frequency name 1
    • Frequency 1 should be either 2.2 GHz (for low-side injection) or 2.6 GHz (for high-side injection)
      • This is the frequency of the local oscillator signal
    • Fill in Amplitude 1 (Vpk) with the amplitude of your LO signal
    • Click OK
  • In the Analog Design Environment, enable the pss analysis
    • Verify that only flo is displated in the Fundamental tones section
    • Select Beat Frequency and click Auto Calculated
    • Select Number of harmonics under Output harmonics and fill in the value of 0
    • Set the Accuracy Defaults (errpreset) to conservative
    • Set the Additional Time for Stabalizatoin (tstab) to a time larger that the settling time of your system
      • Run a short tran simulation to find the time when all of the voltages in your mixer have settled and there is no "ringing"
    • Click OK
  • In the Analog Design Environment select the pnoise analysis
    • The PSS Beat Frequency (Hz) should read 2.2G (2.6G if you are using high-side injection)
    • Set Output Frequency Sweep Range (Hz) to Start-Stop
    • Set Start to 1 MHz and Stop to 1 GHz
    • Set Sweep Type to Logarithmic
    • Use 100 points per decade
    • Under sidebands select Maximum sideband and set it to 30
    • Under Output, select voltage and select the appropriate node for the IF on your schematic
    • For the Input Source select port and select the RF port
    • For Reference side-band select Enter in field and enter -1
    • Click OK
  • Run the Simulation
  • To view the results for the conversion gain simulatoin click Results -> Direct Plot -> Main Form ...
    • Set the Analysis to pnoise
    • Set the Function to Noise Figure
    • Click Plot

Linearity using IIP3

  • You must first instance ports for the RF, LO, and IF ports of the mixer (analogLib -> Sources -> Independent -> port). If your mixer requires differential inputs/outputs then refer to the separate tutorial on how to drive differential signals.
  • Edit the properties of the RF port
    • Set the Resistance to 50 Ω and the Port number to 1
    • Set the Source type to sine
    • Enter frf for the Frequency name 1
    • Enter 2.4 GHz for Frequency 1
    • Enter prf for Amplitude 1 (dBm)
    • Click on Display small signal params and enter prf in the PAC magnitude (dBm) field
    • Click OK
  • Edit the properties of the LO port
    • Set the Resistance to 50 Ω
    • Set the Port number to 2
    • Set the Source type to sine
    • Fill in the flo for the Frequency name 1
    • Frequency 1 should be either 2.2 GHz (for low-side injection) or 2.6 GHz (for high-side injection)
      • This is the frequency of the local oscillator signal
    • Fill in Amplitude 1 (Vpk) with the amplitude of your LO signal
    • Click OK
  • Edit the IF port
    • Set the Resistance to 50 Ω and the Port number to 3
    • Set the Source type to dc
    • Click OK
  • In the Analog Design Environment, enable the pss analysis
    • Verify that both frf and flo are displated in the Fundamental tones section
    • Select Beat Frequency and click Auto Calculated
    • Select Number of harmonics under Output harmonics and fill in the value of 2
    • Set the Accuracy Defaults (errpreset) to conservative
    • Select Sweep and make sure that Variable is selected and enter prf for Variable Name
    • Under Sweep Range select Start-Stop
    • Set Start to -25 and Stop to +5
    • Set Sweep Type to Linear
    • Set Step Size to 5
    • Click OK
  • In the Analog Design Environment enable the pac analysis
    • Under Input Frequency Sweep Range (Hz) chosse Single-Point
    • Set Freq to 2.402 GHz
    • Under Sidebands select Array of indicies
    • Enter -11 -13 (with a space between) in the Additional indicies field
      • These numbers correspond to the harmonic of the beat frequency that corresponds to the fundamental and IM3 components
    • Clic OK
  • Run the Simulation
  • To view the simulation results
    • Click Results -> Direct Plot -> Main Form ...
    • Under Analysis select pac
    • Under Function select IPN Curves
    • For Circuit Input Power select Variable Sweep ("prf")
    • Enter -20 for Input Power Extrapolation Point (dBm)
    • Under 1st Order Harmonic select -11 202M
      • This is our downconverted fundamental component assuming low-side injection (2.402 GHz - 2.2 GHz = 202 MHz)
    • Under 3rd Order Harmonic select -13 198M
      • This is our downconverted IM3 component assuming low-side injection ([2*2.4 GHz - 2.402 GHz] - 2.2 GHz = 198 MHz)
    • Select the IF port on your schematic