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In this letter, we have proposed and demonstrated a novel mixer that requires no local oscillator (LO), but mixes the radio frequency (RF) with its Doppler shifted frequencies on a nonlinear reconfigurable composite right/left-handed transmission line, on which a moving reflective surface is controlled by an external digital circuit. An incident RF encounters a frequency shift when reflected from this moving surface and a difference frequency between the incident frequency and Doppler shifted frequency is generated on this nonlinear transmission line. This kind of mixer has the advantage in high frequency and cognitive radio applications since an LO is not required, meanwhile the intermediate frequency is also tunable electronically. [ABSTRACT FROM PUBLISHER]

The Doppler effect has well-established applications in astronomy, medicine, radar and metrology. Recently, a number of experimental demonstrations of the inverse Doppler effect have begun to appear. However, the inverse Doppler effect has never been observed on an electronically reconfigurable system with an external electromagnetic wave source at radio frequencies (RF) in experiment. Here we demonstrate an experimental observation of the inverse Doppler shift on an electronically reconfigurable RF metamaterial structure, which can exhibit anomalous dispersion, normal dispersion or a stop band, depending on an applied bias voltage. Either inverse or normal Doppler shift is realized by injecting an external RF signal into the electronically reconfigurable metamaterial, on which an electronically controllable moving reflective boundary is formed. The effective velocity of this boundary and the resulting frequency shift can be tuned over a wide range by a digital switching circuit. This work is expected to open up possibilities in applying the inverse Doppler effect in wireless communications, radar and satellite navigation. [ABSTRACT FROM AUTHOR]