A C‐band ultra‐low‐power consumption HMIC amplifier for intelligent transportation system applications

Abstract

Gaussian beam with an effective width of 10 m. While the BPM does not account for the reflected optical beam, it could be used to estimate the transmitted field when the metallic reflector is properly represented by its imaginary refractive index. The metallic shutter is thus modelled in the BPM analysis by a complex refractive index n m ϭ 0.4 ϩ j 8.3 [8]. A calculation window with 30 m ϫ 30 m is used with a number of grid points 128 ϫ 128. Simulation results for optical attenuation versus the shutter position at different shutter thickness are shown in Figure 5. We can also observe the same behaviour (peak in the received power and change in the attenuation sensitivity) at larger shutter thicknesses. This could be explained by the beam reflection from the shutter edge, which increases with the increase in shutter thickness. Such behavior is extremely important for the accurate modelling of the VOA, as it affects both its linearity and sensitivity. CONCLUSIONWe studied the effect of shutter thickness on the attenuation of an optomechanical VOA. Both the experimental and simulation results show that shutter thickness affects the functional behaviour of the VOA attenuation curve, by introducing a peak in the received power. The peak disappears when using a lensed fiber with the shutter located at the plane of the bean waist. These results are important for the precise modelling and design of an optomechanical VOA. A more complete analysis would also require studying the effect of shutter thickness on the polarisation-dependant loss. We are currently investigating this effect. INTRODUCTIONA radio frequency tag and interrogator is a system allowing contactless identification and tracking in applications ranging from computerized club entry, automatic billing, animal tag and track, to automatic waste management [1]. Such a system is awakened by an interrogating signal and sends back a coded response. A potential application in intelligent transport systems (ITSs) concerns dedicated short-range communications (DSRC), in which information is exchanged between roadside interrogators and on-board transponders. The European prestandard that defines the framework for DSRC recommends a 5.8-GHz carrier frequency within a 10-MHz bandwidth [2]. Since the communication distance extends from a few meters (vehicle tolling applications) to several tens of meters (traffic information), the tag should have a local RF source and be powered by an internal wristwatch battery. In this application, low power consumption in the active tag is very important for conserving battery life. An injection-locked directmodulation scheme is one solution to achieve a low-power-consumption active tag. In this scheme, an amplifier is needed to amplify the received weak interrogating signal for locking the local oscillator, thus stabilizing it to the interrogating frequency. By doing so the information to be transmitted can then be directly modulated on this frequency and transmitted back to the interrogator. A high-gain and low-power-consumption ampl...