title: A Low-Noise CMOS THz Imager Based on Source Modulation and an In-Pixel High-Q Passive Switched-Capacitor N-Path Filter.
abstract: This paper presents the first low noise complementary metal oxide semiconductor (CMOS) deletedCMOS terahertz (THz) imager based on source modulation and in-pixel high-Q filtering. The 31 × 31 focal plane array has been fully integrated in a 0 . 13 μ m standard CMOS process. The sensitivity has been improved significantly by modulating the active THz source that lights the scene and performing on-chip high-Q filtering. Each pixel encompass a broadband bow tie antenna coupled to an N-type metal-oxide-semiconductor (NMOS) detector that shifts the THz radiation, a low noise adjustable gain amplifier and a high-Q filter centered at the modulation frequency. The filter is based on a passive switched-capacitor (SC) N-path filter combined with a continuous-time broad-band Gm-C filter. A simplified analysis that helps in designing and tuning the passive SC N-path filter is provided. The characterization of the readout chain shows that a Q factor of 100 has been achieved for the filter with a good matching between the analytical calculation and the measurement results. An input-referred noise of 0 . 2 μ V RMS has been measured. Characterization of the chip with different THz wavelengths confirms the broadband feature of the antenna and shows that this THz imager reaches a total noise equivalent power of 0 . 6 nW at 270 GHz and 0 . 8 nW at 600 GHz.
authors.affiliation: Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus, Grenoble F-38054, France. assim.boukhayma@epfl.ch.|ICLAB, EPFL, Rue de la Maladière 71, Neuchâtel 2000, Switzerland. assim.boukhayma@epfl.ch.
authors.forename: Assim
authors.initials: A
authors.lastname: Boukhayma
authors.affiliation: Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus, Grenoble F-38054, France. antoine.dupret@cea.fr.
authors.forename: Antoine
authors.initials: A
authors.lastname: Dupret
authors.affiliation: Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus, Grenoble F-38054, France. jean-pierre.rostaing@cea.fr.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Rostaing
authors.affiliation: ICLAB, EPFL, Rue de la Maladière 71, Neuchâtel 2000, Switzerland. christian.enz@epfl.ch.
authors.forename: Christian
authors.initials: C
authors.lastname: Enz
keywords: CMOS; Gm-C; N-path; bandpass filter; high-Q; inductorless filter; low noise; sub-millimeter wave detectors; sub-millimeter wave imaging; terahertz direct detection; terahertz imaging; tunable