Robust and economic but precise and high-resolution analysis of optical spectra is of immense interest in optical communications, spectroscopy, sensing, and many other fields. Conventional optical spectrum analyzers utilize either movable gratings, interferometers, heterodyning or Brillouin scattering. Besides the large size, limited robustness and high costs, spectrometers with a high resolution, like interferometers and Brillouin scattering, usually measure only limited bandwidths, while grating-based spectrometers can measure a large bandwidth but, with limited resolution. Here we present preliminary results of a silicon integrated optical spectrum analyzer with wide operational range and high resolution. The device utilizes two spectral filtering devices in succession, namely an integrated high-Q microring resonator with tunable resonance frequency and a wavelength division demultiplexer. The narrow resonances of a tunable ring resonator enable high resolution measurements of the power distribution of unknown signals at multiple positions according to the free spectral range. Subsequently, the individual resonances are separated by a wavelength division demultiplexer with a much broader bandwidth. The narrow and equidistant resonances are placed so that each resonance falls within a separate channel of the demultiplexer. The power of each subchannel is monitored during tuning of the ring by simple low bandwidth photodiodes. If one scan corresponds to the tuning of the ring resonances over the full width of one channel of the demultiplexer, the combination of all channels will represent the whole spectrum of the signal under test. Preliminary experiments show a resolution of 98 MHz.