An Approach for High Bandwidth Wireless Communications with Arbitrary IQ Mismatch

The growing demand for high data rates requires communication systems with great analog bandwidths and high spectral efficiency. In [1], [2], a multicarrier enabled baseband subsampling multiple input multiple output system (MBS- MIMO) has been proposed for wideband applications of the Discrete Multitone (DMT) modulation, the baseband version of OFDM. MBS-MIMO divides the DMT signal into subbands, each one sampled at a fraction of the Nyquist rate. Unlike competing methods like time-interleaved sampling (TI) or Hybrid Filter Bank (HFB) converters, MBS-MIMO does neither require equally spaced sampling, nor equal gains in the subbands, nor high-order subband filters. It has a wider dynamic range than TI converters and extends the bandwidth of the employed converter technology by the number of subbands chosen. This present paper demonstrates that MBS-MIMO can be used for carrier-frequency transmission, too, using an IQ modulator and demodulator. It turns out that, without any further measures, the MBS-MIMO receiver has the ability to compensate for frequency dependent IQ modulator gain and phase imbalance. An IQ modulated MBS-MIMO system at 3,5 GHz with adjustable IQ imbalance has been set up to prove the concept.