Strategies to enhance the data density in synchronous electromagnetic encoders

Altres ajuts: ICREA awardIn this paper, we report two different strategies to enhance the data density in electromagnetic encoders with synchronous reading. One approach uses a periodic chain of rectangular metallic patches (clock chain) that determines the encoder velocity, and dictates the instants of time for retrieving the bits of the identification (ID) code. However, contrary to previous electromagnetic encoders, the ID is inferred at both the rising and the falling edges of the clock signal generated by the clock chain. Moreover, the bits of information are not given by the presence or absence of metallic patches at their predefined positions in the so-called ID code chain. With this novel encoding system, a bit state corresponding to a certain instant of time is identical to the previous bit state, unless there is a change in the envelope function of the ID code signal, determined by the additional non-periodic ID code chain. The other encoding strategy utilizes a single chain of C-shaped resonators, and encoding is achieved by considering four different resonator dimensions, corresponding to four states and, hence, to two bits per resonator of the chain. Thus, with these two strategies, the data density is twice the one achievable in previously reported synchronous electromagnetic encoders

High Data Density Absolute Electromagnetic Encoders Based on Hybrid Time/Frequency Domain Encoding

Altres ajuts: Institució Catalana de Recerca i Estudis AvançatsThis article presents a novel concept for the implementation of electromagnetic encoders exhibiting very high data density per unit length (DPL), a figure of merit (FoM) of such systems. Encoding is based on a hybrid scheme that exploits both the frequency and time domains. The encoders consist of rows of inclusions (linear strips) of different sizes, periodically arranged to form a chain (with four columns). The bits corresponding to each row are read sequentially in a time-division multiplexing scheme, whereas the size of the inclusions provides frequency encoding. The main relevant aspect of the proposed system concerns the reader, based on a power splitter architecture with either two outputs (prototype A) or four outputs (prototype B). It is shown that the data capacity per row in one of the encoders read through prototype B is 8.78 bits, whereas the data density is as high as DPL = 29.26 bit/cm, an unprecedented value in this type of encoders. The proposed system can be used as a near-field synchronous chipless-radio frequency identification (RFID) system, or as a position and velocity sensor. In the latter case, the system is able to provide the absolute encoder position, provided the number of bits per row (or position) is enough to discern the different number of encoder positions (up to 440 different positions for prototype B, corresponding to the indicated number of bits)

Frequency-Coded and Programmable Synchronous Electromagnetic Encoders Based on Linear Strips

This letter presents electromagnetic encoders where encoding is achieved by considering four different inclusions, particularly linear strips of different length, etched at the predefined positions of the encoder chain, and transversely oriented with regard to the chain axis. Since the length of the strips determines their resonance frequencies, it follows that the 2-bits per inclusion, corresponding to the four possible different states (strip lengths), are frequency-coded. Thus, the reader is a microstrip line with a series gap fed by four harmonic (carrier) signals tuned to the resonance frequencies of the four considered encoder strips. By encoder motion over the reader, each carrier signal is amplitude modulated, with envelope functions exhibiting a peak each time a strip of the encoder chain tuned to the resonance frequency of the considered carrier signal crosses the axis of the reader line. The functionality of the system is experimentally validated in this letter. It is also shown that the encoders can be programmed by considering identical strips and by cutting them appropriately, according to the desired code. The proposed encoders are intrinsically synchronous. Such encoders are useful for measuring displacements and velocities, as well as for the implementation of synchronous near-field chipless radiofrequency identification tags with sequential bit reading