3rd Order Intermodulation Distortion Research Articles

High modulation frequency low distortion 1.3 μm MQW-DFB-LDs for subcarrier multiplexed fibre-optic feeder systems

A remarkable improvement has been attained for intermodulation distortion and spectrum linewidth performance for 1.3μm DFB LDs by introducing thin barrier MQWs and short cavity configurations. Less than −85dBc in 3rd order intermodulation distortion and more than 50MHz in spectral linewidth have been simultaneously obtained from devices modulated by two 1.5 GHz signals.

Method for measuring 3rd-order intermodulation distortion in GaAs f.e.t.s

A technique for characterising the 3rd-order intermodulationdistortion properties of GaAs f.e.t.s as a function of the load admittance presented to the output of the device is described. These properties can be determined for virtually any load admittance, including a purely reactive termination. A practical f.e.t example is included for illustration.

Modelling the 3rd-order intermodulation-distortion properties of a GaAs f.e.t.

A simple analytical model of the 3rd-order intermodulation-distortion properties of a GaAs field-effect transistor is proposed. The model takes into account the distortion-producing nonlinearities of the Schottky-bairier junction, the trans-conductance and the drain conductance. Parameters of the model are presented for a GaAs f.e.t. of 0.5 μm gate length, and the model-predicted distortion characteristics are compared with measured data.

7.9–8.4 GHz GaAs m.e.s.f.e.t. amplifier

A 4-stage balanced GaAs m.e.s.f.e.t. amplifier has been developed for the 7.9–8.4 GHz satellite-communication frequency band. Linear gain of 26±0.5dB and 150 mW power at 1 dB compression were obtained across the design band. The small-signal gain, phase linearity, group delay and noise figure are described as a function of frequency. Large-signal gain saturation, 3rd-order intermodulation distortion, gain and phase against temperature and a.m.-to-p.m. conversion data are also presented.

Contribution to mixer intermodulation distortion of nonlinearity in the diode forward characteristics

It is shown that nonlinearity in the forward characteristics of Schottky-barrier devices contributes significantly to the levels of 3rd-order intermodulation distortion in the output of balanced diode mixers. Predicted performance agrees well with results obtained from a typical h.f. mixer.