A system (10A, 10B) for determining at least one parameter of a sheet dielectric sample (18A, 18B) using terahertz radiation, the system (10A, 10B) comprising: at least one terahertz transmitter (22A, 22B) configured to output a pulse of terahertz radiation to the sheet dielectric sample (18A, 18B); a terahertz receiver (24A, 24B) configured to receive at least a portion of the pulse of terahertz radiation from the sheet dielectric sample (18A, 18B), wherein the terahertz receiver (24A, 24B) is configured to output a measured waveform based on the terahertz radiation received by the terahertz receiver (24A, 24B); a control unit (42, 42A, 42B) in communication with the terahertz receiver (24A, 24B) and configured to receive the measured waveform from the terahertz receiver (24A, 24B); the control unit (42, 42A, 42B) is configured to: choose at least one region of interest of the measured waveform, compare the at least one region of interest of the measured waveform to a model waveform, wherein the model waveform is derived from a reference waveform recorded when the sheet dielectric sample (18A, 18B) is not present, vary at least one parameter of a model waveform to minimize the difference between the model waveform and the measured waveform, and determine the at least one parameter of the model waveform so that the model waveform best matches the measured waveform, wherein the at least one parameter of the model waveform includes at least one of the following: thickness of a sheet dielectric model and complex index of refraction of a sheet dielectric model. at least one terahertz transmitter (22A, 22B) configured to output a pulse of terahertz radiation to the sheet dielectric sample (18A, 18B); a terahertz receiver (24A, 24B) configured to receive at least a portion of the pulse of terahertz radiation from the sheet dielectric sample (18A, 18B), wherein the terahertz receiver (24A, 24B) is configured to output a measured waveform based on the terahertz radiation received by the terahertz receiver (24A, 24B); a control unit (42, 42A, 42B) in communication with the terahertz receiver (24A, 24B) and configured to receive the measured waveform from the terahertz receiver (24A, 24B); the control unit (42, 42A, 42B) is configured to: choose at least one region of interest of the measured waveform, compare the at least one region of interest of the measured waveform to a model waveform, wherein the model waveform is derived from a reference waveform recorded when the sheet dielectric sample (18A, 18B) is not present, vary at least one parameter of a model waveform to minimize the difference between the model waveform and the measured waveform, and determine the at least one parameter of the model waveform so that the model waveform best matches the measured waveform, wherein the at least one parameter of the model waveform includes at least one of the following: thickness of a sheet dielectric model and complex index of refraction of a sheet dielectric model. choose at least one region of interest of the measured waveform, compare the at least one region of interest of the measured waveform to a model waveform, wherein the model waveform is derived from a reference waveform recorded when the sheet dielectric sample (18A, 18B) is not present, vary at least one parameter of a model waveform to minimize the difference between the model waveform and the measured waveform, and determine the at least one parameter of the model waveform so that the model waveform best matches the measured waveform, wherein the at least one parameter of the model waveform includes at least one of the following: thickness of a sheet dielectric model and complex index of refraction of a sheet dielectric model.