  A novel broadband microwave (MW) spectrum measurement (BMSM) scheme based on
code-free optical undersampling and homodyne detection is proposed. The fully
analog generation of optical pulses with a far-less-than-Nyquist rate is only
through modulating cascaded electrooptical modulators by a single RF tone
instead of any high-speed coding sequence modulation. Homodyne detection will
reduce the analysis bandwidth of BMSM and enhance the detection performance of
weak signal. A multi-band signal with 20 GHz spectral range and SNR = 61 dB is
used to investigate the BMSM performance of this scheme, and the results show
good performance for BMSM. The potentials for further optimization in practice
are also discussed.
