Radio Frequency Transceiver Metal Layer Change Impact on Calibration Matrices
Metal layer changes alter integrated transceiver parasitic reactances, corrupting factory calibration matrices and degrading RF performance without recalibration.
Predistortion Matrix
Meaning
Mathematical model compensates for the non-linear behavior of a power amplifier in a radio transmitter. The predistortion matrix applies an inverse transformation to the digital signal before it reaches the analog components. This correction helps to produce an output that is a faithful representation of the intended waveform.
Inverse Transformation
The coefficients within the array are calculated by comparing the input signal to a feedback sample of the amplified output. By applying the predistortion matrix, the system nullifies the gain compression and phase shifts introduced by the amplifier. This results in a more linear response across the entire power range of the transmitter.
Processing Load
Real time implementation of this technique requires heavy digital signal processing resources. The size of the predistortion matrix determines the precision of the correction and the complexity of the math involved. More complex matrices can correct higher order distortions but also consume more power, which is a factor for mobile handsets or remote sensors.
The algorithm must update the values frequently to account for changes in temperature and load impedance. This prevents the distortion from returning as the environment shifts.
Spectral Efficiency
Linearization allows the transmitter to operate closer to its saturation point without violating emission masks. When the predistortion matrix is optimized, the device can use higher order modulation schemes like 256 qam. This improves the data rate of the link while maintaining compliance with regulatory standards for out of band emissions.