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RF Mixer Downconversion

Simulation of a superheterodyne downconversion stage using the RFMixer block. A high-frequency RF signal is mixed with a local oscillator (LO) to produce an intermediate frequency (IF) output.

Mixer Model

The RFMixer performs ideal time-domain multiplication:

MATHDISPLAY0ENDMATH

For sinusoidal inputs at frequencies MATHINLINE2ENDMATH and MATHINLINE3ENDMATH, the output contains sum and difference frequencies:

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System Setup

We set up a downconversion scenario:

RF signal at 1000 Hz
LO at 900 Hz
Expected IF at 100 Hz (difference) and 1900 Hz (sum)

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Connections

The RF source connects to the mixer's rf input (port 0), the LO source to the lo input (port 1). The mixer output goes to both a scope and spectrum analyzer.

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10:58:24 - INFO - LOGGING (log: True)
10:58:24 - INFO - BLOCKS (total: 5, dynamic: 1, static: 4, eventful: 0)
10:58:24 - INFO - GRAPH (nodes: 5, edges: 6, alg. depth: 2, loop depth: 0, runtime: 0.064ms)
10:58:24 - INFO - STARTING -> TRANSIENT (Duration: 0.10s)
10:58:24 - INFO - --------------------   1% | 0.0s<1.2s | 760.2 it/s
10:58:24 - INFO - ####----------------  20% | 0.2s<0.6s | 1193.0 it/s
10:58:24 - INFO - ########------------  40% | 0.4s<0.4s | 1223.0 it/s
10:58:24 - INFO - ############--------  60% | 0.5s<0.3s | 1205.8 it/s
10:58:24 - INFO - ################----  80% | 0.7s<0.2s | 1185.1 it/s
10:58:24 - INFO - #################### 100% | 0.8s<--:-- | 1196.7 it/s
10:58:24 - INFO - FINISHED -> TRANSIENT (total steps: 911, successful: 911, runtime: 848.69 ms)

Time-Domain Results

The mixer output shows the characteristic beat pattern of two closely spaced frequencies.

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Frequency-Domain Analysis

The spectrum of the mixer output should show two peaks at the sum and difference frequencies: MATHINLINE0ENDMATH Hz and MATHINLINE1ENDMATH Hz.

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