Spice-Simulation Using LTspice Part 2 - IEC & Associates

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For a separate presentation of the two S-parameters right click on the diagram and chooseAdd Plot Planefor the parameter S21. Delete the S21-curve in the „old“ diagram and scale both diagrams again:102
15. Project 11: Double Balanced Mixer (= DBM = Ring Modulator)15.1. Fundamentals and DefinitionsThis well known circuit is used for converting frequencies without changing the information contents.We have two inputs and one output:Note:a) RF = radio frequency input. Here the applied signal amplitude must be small (typically below50...100mV)b) LO = local oscillator input. Here the signal must be high (typically up to several volts)c) IF = intermediate frequency output. Here we find the converted signals.This operates a multiplier circuit for the two input signals!When two sine signals are multiplied we get the following result:sin12( α )• sin( β ) = [ sin( α + β ) + sin( α − β )]This means for our circuit:At the output of the DBM the two input signals have disappeared and are now replaced by their sumfrequency and difference frequency!When using a square wave signal as the LO-input, then this signal consists of the fundamental frequency f1 andthe harmonics (with 3 x f1 , 5 x f1 , 7 x f1 , 9 x f1......).Not only the fundamental frequency but also the harmonics are now multiplied by the RF-signal in the DBM andproduce sum and difference frequencies with amplitudes that decrease linearly with the “harmonic’s degree”.So you get at the DBM’s output a lot of „signal pairs“ (= sum- and difference frequencies). Every pair islocated at a harmonic frequency.In practical applications the desired new frequencies must now be picked out with a lowpass or a bandpass filterby the user.103
Page 1 and 2: 12. Project 8: Thyristor Circuits12
Page 4: 12.4. Circuit with Gate Transformer
Page 7 and 8: 13.2. Echoes (= Reflections)At high
Page 9 and 10: 100m • sCable−6c) Signal runtim
Page 11 and 12: tdelayl=vcable100m• s= = 0,5μs82
Page 13 and 14: ) Open circuit at cable’s endChan
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Page 21 and 22: S12 is then the „reverse transmis
Page 23 and 24: 14.2. Example: 110MHz - Tchebyshev
Page 25: Step 3:The result is not so bad, bu
Page 29 and 30: 15.3. The necessary TransformersThe
Page 31 and 32: The polarity changing of the RF sig
Page 33 and 34: 16.2. Simple start: the Inverter (=
Page 35 and 36: 16.4. D FlipflopThis is the well kn
Page 37 and 38: 17. Project 13: Noise Simulation17.
Page 39 and 40: 17.1.2. Other Sources of NoiseEach
Page 41 and 42: At the output we addthe label „ou
Page 43 and 44: 17.3. Simulation of the Noise Figur
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Page 47 and 48: 18. Simulation of a Sine Oscillator
Page 49 and 50: The duration of theperiod is 28ms a
Page 51 and 52: And the FFT spectrum proves this.12
Page 53 and 54: Please remember:Every -- even the s
Page 55 and 56: 19.2. Simulation of a Single Pulse
Page 57 and 58: 19.3. Simulation of a Periodic Puls
Page 59 and 60: 19.5. The „Asymmetric Clipped“
Page 61 and 62: 20. The Secret of the Impulse Respo
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Page 65 and 66: At higher frequencies the influence
Page 67 and 68: Solution for a): Simulated S21 from
Page 69 and 70: Solution for d): FFTA simulation ti
Page 71 and 72: 20.2.2. Simulation of S11 (= input
Page 73 and 74: 21. Modulation21.1. Principle of Am
Page 75 and 76: 21.2 Amplitude Shift Keying (ASK)Th
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Now let us regard the simulated FFT
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The linear frequencyspectrum simula
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Spice-Simulation Using LTspice Part 2 - IEC & Associates

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