A 140–500GHz CMOS THz Spectroscope with 1MHz Resolution Based on Multi-Branch Rotational Symmetric Sensing Surface

This paper proposes a fully integrated wideband high-resolution THz spectroscope using a multi-branch rotational symmetric sensing surface. The interaction between the sensing surface and the incident signal is exploited to extract spectral information. Such surface is formed by the multi-branch structure, which can not only expand the induction frequency range but also increase the effective induction area. Besides, the proposed multi-branch structure can support multiple detectors to achieve high detection accuracy. Meanwhile, consistent responses for incident signals in different polarization directions can be achieved by the rotational symmetric characteristic of the proposed sensing surface. Therefore, high-resolution signal detection within a wideband can be achieved. To verify the mechanisms, a THz spectroscope is implemented in a 40-nm CMOS process with a size of 0.99 × 0.8 mm² including all I/O pads. The measurement results exhibit the THz spectroscope features a 140 to 500 GHz detection range with 1 MHz frequency resolution.