Abstract-In this work, a millimeter wave microstrip frequency-mixer design based on graphene is presented. The desired frequency mixing behavior is obtained using a nonlinear component consisting in a microstrip line gap covered by a graphene layer. The circuit includes microstrip filters that have been designed to obtain a high isolation between the input and output ports. The nonlinear behavior of the frequency mixer has been experimentally evaluated in the 38.6-40 GHz input signal frequency range, for different values of the input power and local oscillator power.

Abstract-In this work, a sub-millimeter wave frequency scanning 8 × 1 element antenna array is presented for its use in a terahertz imaging system operating in the 220-330 GHz frequency band. The antenna array is formed by eight open ended waveguides, a phaseshifting network implemented with WR-3 rectangular waveguides and a power divider. Dielectric rods are used to improve the radiation patterns at large beam-steering angles. Prototypes of antenna arrays with and without the dielectric rods have been manufactured and experimentally characterized. A beam-steering range greater than 40 • has been obtained for a frequency sweep between 270 GHz and 330 GHz.

In this work, a subharmonic frequency mixer for millimeter wave applications has been designed. The mixing and multiplication phenomena are simultaneously achieved via a nonlinear component consisting in a microstrip line gap covered by a graphene film coating. The circuit structure is made up of various filters, which have been optimized to ensure high port-to-port isolation. The nonlinear behavior of the subharmonic frequency mixer has been experimentally evaluated within the 39-40.5 GHz RF frequency band. The frequency downconversion is achieved by mixing the RF signal with the second harmonic component of a 17.9 GHz LO signal. Conversion losses are minimized by generating a return path for IF, through the use of a quarter wavelength open-ended stub.

Abstract-In this work, a nonlinear technique for the optimization of the synchronization bandwidth of Rationally Synchronized Oscillators (RSO) is presented. The circuit is forced to operate near a Hopf bifurcation point which is created around the frequency of the input reference signal. Under this operating regime, the reference signal is strongly amplified and the synchronization bandwidth of the circuit is considerably improved. A 5-3 GHz rationally synchronized oscillator has been optimized using the proposed method. The manufactured RSO provides a 5 MHz synchronization bandwidth with a reference signal power of −22 dBm, in good agreement with simulation results.

Abstract-In this work, a novel multi-carrier Tx-Rx system based on rationally synchronized oscillators to be used in RF-source localization applications is presented. The Tx subsystem is composed by two rationally synchronized oscillators, with different operation frequency, which share the reference signal. This signal is transmitted together with the one generated by the oscillators. In the Rx subsystem, the reference signal is provided by an oscillator which is synchronized with the received reference signal. According to the simulation results, with the proposed approach, the determination of the relative phase variation suffered by the transmitted signals, due to the propagation channel, can be achieved with an error less than 0.6 • . It is also shown that the dynamic response of the system can be optimized by properly selecting the operation point of all oscillators.