{blockLibraryPP_blocksPP_FF_RFSS_BlocksetFF_IdealizedSS_BasebandFF_MixerPP_label}
RF and IQ modulator and demodulator models with interference and noise.
blockType: Mixer
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Path in the library: |
Description
The unit {blockLibraryPP_blocksPP_FF_RFSS_BlocksetFF_IdealizedSS_BasebandFF_MixerPP_label} represents four complex mixers of the main frequency band as well as interference and noise. The block models four types of mixers: modulator, demodulator, IQ modulator and IQ demodulator. Signal distortion is IQ gain and phase mismatch where appropriate, and noise includes system noise and LO phase noise.
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The idealised block model {blockLibraryPP_blocksPP_FF_RFSS_BlocksetFF_IdealizedSS_BasebandFF_MixerPP_label} assumes that the input and output ports are matched.
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The idealised block model {blockLibraryPP_blocksPP_FF_RFSS_BlocksetFF_IdealizedSS_BasebandFF_MixerPP_label} is single band with an assumed carrier frequency value. Therefore, the block {blockLibraryPP_blocksPP_FF_RFSS_BlocksetFF_IdealizedSS_BasebandFF_MixerPP_label} can only generate one sideband at the output.
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The mixer block mask icons are dynamic and indicate the current set of applied noise parameters. For more information, see. Mixer Block Icons.
Algorithms
Mixer block architectures and design equations
Here are the architectural models for the block {blockLibraryPP_blocksPP_FF_RFSS_BlocksetFF_IdealizedSS_BasebandFF_MixerPP_label}. Here is the mixer and phase noise data for all cases.
Modulators and Demodulators
The modulator and demodulator architectures include system noise, phase noise, and nonlinear polynomials for carrier translation. A random number generator is used as input to generate phase noise.
The output of an ideal modulator and demodulator circuit with nonlinearities, , is given by this equation:
where
IQ modulator
The primary IQ modulator consists of two mixers, and . The mixers convert baseband signals into RF signals and are typically used in direct conversion architectures. The mixers and are responsible for introducing gain, gain imbalance, phase imbalance and nonlinearity into the IQ demodulator.
The output signal of the IQ modulator, , is defined as:
where
The linear gains of the modulators and are given in Eq:
where
IQ Demodulator
The architecture of the IQ demodulator is shown below. The in-phase, , and quadrature component, , of the modulated signal are the outputs of and , respectively. The mixers, and , are responsible for introducing gain, gain unbalance, phase unbalance and nonlinearity into the IQ demodulator.
The output of the IQ demodulator, , is as follows
where
The linear gains of the modulators and are given in this equation.
where
Mixer unit sidebands
Upper and lower sidebands
The expression for shows the formation of the upper and lower sidebands, and , and the effect of the difference between the input carrier and LO signal values on the sine function. Application of the trigonometric identity:
to the expression of the product of mixers, , gives
where the term associated with the higher output frequency, , is the upper sideband, and is the lower sideband. Set the Type of mixer parameters to mod.
For demodulators, only the lower sideband can be used as the output.
Selecting a mixer by type
When selecting a mixer type, this table shows the available sideband options according to the block parameters LO phase offset, IQ gain imbalance and IQ phase imbalance.
| Mixer type | Distortion | Noise |
|---|---|---|
Modulator |
LO phase offset and nonlinearities. |
LO phase offset, mixer and system noise. |
Demodulator |
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IQ Modulator/Demodulator |
Gain imbalance, phase imbalance and nonlinearity. |
Mixer block icons
This table shows how the block icons will change depending on the values of the parameters Type of mixer, Options to mixer noise to system and Add LO phase noise to LO signal.
| Type of mixer | Options to mixer noise to system | Add LO phase noise to LO signal: off. | Add LO phase noise to LO signal: on. |
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Modulator
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Demodulator
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IQ Modulator
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IQ-Demodulator
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Literature
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Razavi, Behzad. "Basic Concepts in RF Microelectronics", 2nd edition, Prentice Hall, 2012.
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Kundert, Ken."Accurate and Rapid Measurement of IP2 and IP3," The Designer Guide Community, May 22, 2002.
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Kasdin, N.J.. "Discrete Simulation of Colored Noise and Stochastic Processes and 1/f α Power Law Noise Generation." Proceedings of the IEEE 83, no. 5 (May 1995): 802-27. https://doi.org/10.1109/5.381848.