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This paper presents a cost effective solution for remote radiofrequency temperature sensing, taking advantage of a Schottky junction nonlinear characteristic and the device integration in a properly designed dual-frequency radiator. Once the proposed integrated active antenna is interrogated with a CW excitation, the level and phase of the third harmonic response signal gives information of the tag...
In this paper, a frequency agile phase-conjugating active antenna is presented, for its use in full-duplex and secure retrodirective communication links. Two enhancement-mode PHEMT's are properly combined to simultaneously act as a subharmonic and a 180-degree singly balanced resistive mixer, allowing downconversion of an AM interrogating signal as well as retransmission of a BPSK response. A varactor-controlled...
This paper presents two frequency converting PHEMT-based active antennas to be used in RFID applications. A proper characterization of the transistor nonlinear behavior revealed the existence of two biasing regions where the response signal, the second harmonic or the IF component, can be generated with maximum conversion gain and phase opposition. This attractive issue has been taken advantage of,...
In this paper, an exhaustive study of different equivalent circuits of an aperture coupled patch permits to develop a suitable circuit model. The vast majority of these models are able to reproduce the antenna behavior around the first resonance frequency, but the proposed equivalent circuit is also capable of duplicating the radiator input impedance in the two next harmonics. Over such model two...
This paper presents an active reflectarray with the capability of steering the main beam and achieving different amplitude distributions. The amplitude and phase of the scattered field from each reflectarray element is controlled by the use of an IQ modulator. An aperture coupled patch with perpendicular microstrip feeds is employed as radiating element. One of its ports is employed to receive the...
In this paper, a novel highly linear circularly polarized active antenna with gain control is presented. A printed patch is used as the output 90?? hybrid in a HEMT balanced amplifier, whose branches provide gain control based on a new biasing strategy. Low intermodulation distortion (IMD) and reduced DC power consumption are assured along The proposed radiating structure could be efficiently integrated...
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