Model mixer in RF systems
RF Blockset / Circuit Envelope / Elements
The Mixer block performs signal frequency translation and nonlinear amplification.
For a given RF input signal, VRF = ARFcos(ωRFt) and an LO input signal VLO = AcLOcos(ωLOt), the mixer multiplies the signals at the input ports:
This mixing converts the frequency of RF signal to ωRF + ωLO and ωRF – ωLO. For the mixer to perform this operation correctly, you must include the frequencies ωRF + ωLO or ωRF – ωLO in the simulation frequencies the Configuration block calculates.
The Power gain specification for this block relates the power of a single-sideband (SSB) to the input.
After mixing the RF and LO signals, the mixer block performs amplification. To model linear amplification, the mixer scales the signals by the coefficient a1. A Voltage Controlled Voltage Source (VCVS), specified with a polynomial, implements nonlinear amplification. The polynomial includes saturation automatically and produces additional intermodulation frequencies.
[1] Grob, Siegfried, and Jürgen Lindner. “Polynomial Model Derivation of Nonlinear Amplifiers.” Department of Information Technology, University of Ulm, Germany.