In this paper, a novel terahertz (THz) spectroscopy technique and a new graphene-based sensor is proposed. The proposed sensor consists of a graphene-based metasurface (MS) that operates in reflection mode over a broad range of frequency band (0.2 - 6 THz) and can detect relative permittivity of up to 4 with a resolution of 0.1 and a thickness ranging from 5 μm to 600 μm with a resolution of 0.5 μm. To the best of author's knowledge, such a THz sensor with such capabilities has not been reported yet. Additionally, an equivalent circuit of the novel unit cell is derived and compared with two conventional grooved structures to showcase the superiority of the proposed unit cell. The proposed spectroscopy technique utilizes some unique spectral features of a broadband reflection wave including Accumulated Spectral power (ASP) and Averaged Group Delay (AGD), which are independent to resonance frequencies and can operate over a broad range of spectrum. ASP and AGD can be combined to analyse the magnitude and phase of the reflection diagram as a coherent technique for sensing purposes. This enables the capability to distinguish between different analytes with high precision which, to the best of author's knowledge, has been accomplished for the first time.

Many configuration have been used for the array antenna and rectangular or triangular networks have been the most attentive topology. In fact, Synthesis techniques can take the advantage of periodicity of these type of networks. Concentric rings array are a special type of array antennas that are used in tracking radars and acoustic systems. This type of arrays does not have linear periodicity in a plane. Therefore, many methods that are based on the linear periodicity of elements are unable to deal with the difficulty of the calculations. Besides, the number of elements in this type of arrays may be very high or even thousands of elements which makes the synthesis procedure more complicated and time consuming. In this paper, these deficiencies and complexity have been reduced in very great extent by using non-uniform sampling and sectional excitation. In the proposed technique, each array is divided into the smaller sub-arrays making up more control over the symmetric array factor by sectional excitation. This control over array factor makes possible to synthesize asymmetric pattern from such circularly symmetric arrays. The results confirm that using sectional excitation maintains the parameters of the array factor at the desired values and this is done with less time.

In the present paper, a photoconductive antenna is designed to work as both pulse-terahertz emitter and receiver. The proposed two-port antenna benefits from polarization diversity with high sensitivity of polarization detection. The antenna electrodes consist of three arms and two gaps that can be excited by laser illumination. An 800 nm wavelength laser beam with output power of 80 mW, 100 MHz repetition rate, and 100 fs laser pulse duration is considered as optical excitation. Each port stimulates a pulse that its polarization is orthogonal to that of the other one according to their arrangement. Along with GaAs as photoconductive substrate beneath the antenna electrodes, an anti-reflection coating of Taconic RF-35 is used for depreciating unwanted terahertz echoes. The simulated results clarify that the proposed antenna shows polarization diversity and also, proper broadband behavior.