RF front-end for impulse UWB communication systems

In this paper, we propose a multi(six)-port radio frequency (RF) front-end including both modulator and demodulator for impulse ultra-wideband (UWB) communication systems. This RF front-end validates full channel (3GHz-4GHz) uniform phase spectrum modulation scheme by using a six-port phase modulator and demodulator. Both the modulator and demodulator adopt the same six-port circuit structure. This kind of quasi-symmetric transceiver front-end is relatively easy to design and fabricate. To validate the proposed RF front-end for UWB communications, a wideband signal with a 1GHz bandwidth is generated from a 2ns pulse and up-converted using a center frequency of 3.5GHz. The 3GHz-4GHz signal is applied to the RF input of a six port modulator and digital data is simultaneously fed to the baseband inputs of the modulator. This operation produces a signal whose phase spectrum is uniformly modulated. Two input ports of the six-port demodulator are fed respectively with the received phase modulated signal and the reference non-modulated signal. The demodulator's four outputs provide different signals used to determine the modulation states with an algorithm based on the six-port circuit features. A proof-of-concept experiment has been realized using this multi-port RF front-end and a field programmable gate array (FPGA) based digital signal processing (DSP) platform implementing the demodulation algorithm and synchronization control. Both measurement and simulation results validate the proposed front-end and corresponding algorithms for a 1GHz UWB channel.