Difference between revisions of "RF Tutorial Lesson 16: Building Frequency Conversion Mixers With Virtual Blocks"
Kazem Sabet (Talk | contribs) (Created page with "{{projectinfo|Tutorial| Building Frequency Conversion Mixers With Virtual Blocks |SysTUT5 6.png|In this project, you will build and test basic and harmonic mixer systems using...") |
Kazem Sabet (Talk | contribs) |
||
Line 11: | Line 11: | ||
|All versions|{{download|http://www.emagtech.com/downloads/ProjectRepo/SystemLesson5.zip System-Level Lesson 5}} }} | |All versions|{{download|http://www.emagtech.com/downloads/ProjectRepo/SystemLesson5.zip System-Level Lesson 5}} }} | ||
− | + | == What You Will Learn == | |
In this tutorial you will learn how to use RF.Spice's spectral processing and frequency conversion black-box virtual blocks such as frequency multipliers, up-converters, down-converters, etc. | In this tutorial you will learn how to use RF.Spice's spectral processing and frequency conversion black-box virtual blocks such as frequency multipliers, up-converters, down-converters, etc. |
Latest revision as of 18:24, 8 November 2016
Contents
What You Will Learn
In this tutorial you will learn how to use RF.Spice's spectral processing and frequency conversion black-box virtual blocks such as frequency multipliers, up-converters, down-converters, etc.
Building & Testing a Basic Mixer
The following is a list of parts needed for this part of the tutorial lesson:
Part Name | Part Type | Part Value |
---|---|---|
VLO | Voltage Source | Waveform TBD |
VIF | Voltage Source | Waveform TBD |
E1 - E2 | Voltage-Controlled Voltage Source | Connections & Dependencies TBD |
A1 | Multiplier Block | Defaults |
X1 | Generic Bandpass Filter Block | Defaults, Center Frequency = 14.25MHz, Bandwidth = 1MHz |
X2 | Generic Bandpass Filter Block | Defaults, Center Frequency = 14.25MHz, Bandwidth = 1MHz |
R1 - R3 | Resistor | 50 |
In Analog Tutorial Lesson 14, you analyzed a balanced mixer made up of six BJT transistors, an LC tank circuit and three coupling transformers. In other words, you built a physical circuit using real components. In RF.Spice A/D you can also use virtual blocks that accomplish similar functions but without exposing their internal circuit details. In many ways, virtual blocks act like 'Black-Box" parameterized subcircuit models.
A mixer is basically an analog voltage multiplier. When the two inputs of a multiplier, which is a two-signal analog operation block, are two sinusoidal signals with frequencies fLO (local oscillator) and fIF (intermediate frequency), its output will have two frequency components: fRF = fLO ± fIF. You can separate these spectral components using bandpass filters. Once again, you can realize physical filters using L & C components or use virtual blocks as you saw earlier in System-Level Tutorial Lesson 2. In that lesson, you defined a bandpass filter using its mathematical representation, i.e. its s-domain transfer function. RF.Spice's Generic Bandpass Filter Block allows you to simply specify the center frequency and bandwidth of your filter; the rest is taken care of!
Place and connect the parts as shown in the figure below. The two voltage-controlled voltage sources E1 and E2 are used to replicate the output signal of the multiplier block. In other words, both depend on the voltage at Node 3 with a unity gain.
Linear controlled sources can effectively be used to buffer different parts of your circuit or system and replicate various signals without causing undesirable loading effects. |
Set the waveforms of the two voltage sources VLO and VIF according to the following table:
|
|
Run a Transient Test of this circuit with the parameters specified below:
The simulation results are shown in the figure below. Once again, you can see that it takes quite a while until the amplitude of the output signals stabilizes. Scale the time axis and limit it to the interval t = [14.5μs, 15μs]. The figure below shows the output of the multiplier block along with the outputs of the two bandpass filters. Using the graph window's "Delta Line Mode" try to measure the periods of the filter output signals v(5) and v(7). You will find them to be about 70.2ns and 89ns, respectively, corresponding to the frequency of 14.245MHz and 11.236MHz, as you would have expected. Trying Out the Up-Converter and Down-Converter BlocksThe following is a list of parts needed for this part of the tutorial lesson:
An analog signal multiplier and a bandpass filter together form either a frequency up-converter or a frequency down-converter depending on the passband of the filter. In this part of the tutorial lesson, you will test RF.Spice's up-converter and down-converter blocks. These blocks assume that the two input signals have the same amplitude. Place and connect the parts as shown in the figure below. Note that you don't need buffering controlled source any longer. Set the waveforms of the two voltage sources VLO and VIF according to the following table:
|