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A direct quadrature phase shift keying modulator based on six-port technology is presented. The modulator comprises a six-port circuit, a switch matrix and open and short terminations. Using this modulator, direct phase shift keying modulation was achieved. Six-port technology has the advantage of signal integrity, low power consumption and physical scalability to attain different frequencies of operation and extendibility to M-ary phase shift keying. Experiment results demonstrate performance with an output phase difference from 0.8 to 4.5 and an amplitude difference from 0.5 to 2.7 dB. A data throughput of 200 Mbits was attained.

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Abstract-Multi(six)-port impulse radio (MIR) validates the full channel (3-4 GHz) novel quaternary phase spectrum modulation (QPSM) scheme using a six-port modulator and demodulator circuits. Due to the lack of a monocycle generator, a 1-GHz spectral phase channel is generated from a rectangular pulse signal, upconverted using filters, mixer, and a local oscillator. The 3-4-GHz signal is applied to the RF input of a six-port modulator and digital data is simultaneously fed to a switch matrix terminating four ports of the modulator with either a short or open circuit. This operation produces an output signal in the QPSM scheme. One input port of the six-port demodulator is fed with the received phase-modulated signal and a second input port is fed with the reference nonmodulated signal. The demodulator's four outputs provide signals of different amplitudes used to determine the modulation states with digital signal processing (DSP) algorithms. Modulation algorithms, demodulation algorithms, and synchronization control are implemented on a field-programmable gate-array-based DSP platform fitted with four analog-to-digital converters. Measurements and simulation results are presented to validate the MIR hardware and software in an operating 1-GHz ultra-wideband channel.Index Terms-Quaternary phase spectrum modulation (QPSM), six-port demodulator, six-port modulator, ultra-wideband (UWB).

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A significant amount of work has been carried out on the application of six-port receivers for single carrier communications and for the impulse ultra-wideband radio, however a small interest has been shown on the research of its use for orthogonal frequency division multiplexing (OFDM) communication systems. OFDM and its derived forms are now essential multi-carrier modulation techniques for various present and future high speed wireless communication systems. In this paper, we investigate the possible application of direct conversion six-port receiver for the OFDM signal. The application of six-port receiver for the OFDM signal proves its suitability for the present and future wireless communication systems based on standards such as IEEE 802.11x, 802.16x and 802.15.

-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 proofof-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 frontend and corresponding algorithms for a 1GHz UWB channel.