Analogue Linearization

Several analogue techniques were conceived from the early days of AM broadcasting. Amongst these are feedback, feed forward and predistortion all of which are still widely used. Analogue predistortion and feedforward have been applied in multi-carrier applications such as satellite communications and more recently in cellular communication base station hardware.

The company has extensive experience in the design and optimization of analogue predistortion and feedforward systems.

Digital predistortion

In many ways digital and analogue predistortion are analogous; in both techniques, the input signal is multiplied by the inverse of the amplifier’s nonlinear characteristics. The major difference being that in analogue techniques the RF signal is inverted, where as in DPD the predistortion happens earlier in the transmitter chain and before the digital information is modulated. The predistortion at the base-band level (low frequency) enables the application of digital signal processors for the generating of the inverse transfer characteristics.

Telecom Technologies has extensive experience in the design of DPD systems.

Power Amplifier Memory effects

One major difficulty in implementing digital predistortion systems is the presence of memory effect in RF power amplifiers. The memory effect in an RF PA is many ways analogous to a mechanical flywheel system. (Click on the flywheel systems below.)

Mechanical flywheel

The two systems are similar as they both exhibit “memory effects” by storing energy. Although the design of digital predistortion circuitry is at an advanced level of maturity, the correction of memory effects in power amplifiers is a major challenge in DPD systems, particularly in multi-carrier applications such as wide band CDMA (WB-CDMA).

Telecom Technologies has developed pioneering techniques to correct for amplifier memory effects. Contact the company for more details.