UWB LFM waveform phase and magnitude errors compensation using RF modulation

This paper presents a low cost and efficient method to compensate the phase and magnitude errors of transmitting ultra-wideband (UWB) linear frequency modulation (LFM) waveform with complex pre-distortion correction coefficients. In this method, a high linearity LFM waveform is generated by a direct digital synthesis (DDS) module. The phase and magnitude errors of the output LFM signal are sampled and analyzed by a digital oscilloscope. The pre-distortion coefficients can be calculated according to the measured data. The process of compensation is implemented by modulating the LFM waveform with pre-distortion coefficients from baseband signals. To verify this method, a wideband LFM waveform generator with predistortion compensation is designed and tested. The measured results show that, with compensation, the magnitude and phase errors can be evidently improved (the peak magnitude deviation is from 4.8 dB to 0.2dB, the peak phase deviation is from 60° to 15°, and the linearity performance of LFM waveform is improved to be less than 7×10^-5) within a 1.5GHz-wide frequency bandwidth.