IDENTIFICATION DEVICE

Abstract: Method and device for individual identification using electronic interrogation by transmission and reception of signals of a certain frequency from a transmitter/receiver unit. The device comprises an identification chip (1), comprising an inactive code carrier (2), such as a SAW-component, and an antenna (4), where the antenna (4) receives the transmitted signal which then is applied to the code carrier (2), and a signal, superimposed with the individual code of the code carrier, is reflected from the code carrier (2). Two signals (f0, f1) of different frequencies are mixed after reception by the antenna (4), and are applied to the code carrier (2), which reflects a coded signal (f2'). This coded signal (f2') is mixed with the first transmitted signal (f0) to provide a second coded signal (f1'), having a frequency corresponding to the frequency of the second transmitted signal (f1).

Description: IDENTIFICATION DEVICE. 1 The present invention concerns a method for individual identification using electronic interrogation, and an identification chip for this purpose, according to the introductory part of patent claim 1, resp. 2. The invention is based upon an identification chip having an inactive code carrier, which typically comprises a so-called SAW (Surface Acoustic Wave) - component. Such SAW-components are well known for individual identification. The SAW- component is coded, so that each chip has its own code, which gives a unique identification of the chip, and the object to which it is fastened. In addition, each chip contains an antenna, and optionally components for impedance matching and physical encapsulation. The use of such indentification chips is based upon a central unit comprising a transmitter and a receiver, generating a microwave signal, which is transmitted and received by the antenna on the identification chip. The signal is then converted to an acoustic surface wave, which propagates along the SAW-component, and gives reflections, mirroring the code of this component. These reflected signals are then converted to an electronic signal. This signal is transmitted from the chip and is received by the receiver in the central unit, where it is further processed for dermining the individual identification. There are many different embodiments of these components in respect of code methods, code length, physical geometry, choice of material, etc. Furthermore, it is also known to use so-called BAW (Bulk Acoustic Wave) - components for similar purposes. A disadvantage with SAW-chips is that they are relatively narrow-banded, so that each kind of chip must be manufactured with a special geometry. This makes it more difficult to provide efficient utilization of frequencies above 1 GHz. It is therefore an object of the present invention to provide a method and a device for individual identification using electronic interrogation of the above mentioned kind which permits a more flexible use of frequencies. The object of the invention is achieved with a method having features as stated in the characterizing part of patent claim 1 and an identification chip for use in connection with the invention is stated in the characterizing part of patent claim 2. Further features in the device are stated in the dependent claims. In the following, a preferred embodiment of the invention will be described with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of a device for use according to present invention, Fig. 2a and 2b are frequency diagrams for signals transmitted from the transmitter/receiver unit, Fig. 3a and 3b are frequency diagrams for reflected, coded signal, and Fig. 4 is a more detailed drawing of the components which are parts in a device according to present invention. Fig. 1 shows an identification chip according to present invention. The identifica- tion chip is generally denoted 1, and comprises a code carrier 2, e.g. a SAW-com- ponent, a frequency mixer 3, and an antenna 4. Signals from a transmitter (not shown) are received by the antenna 4 and are propagated via the mixer 3, to the code carrier 2. From the code carrier 2 a signal is reflected via the mixer 3 and trans¬ mitted to the antenna 4, and back to transmitter/receiver unit (not shown). Fig. 2a is a frequency diagram illustrating the signal which is transmitted from the transmitter. In this example of an embodiment, an interrogation signal fj is trans¬ mitted together with a carrier signal f 0 . This signal is received by the antenna 4 in the identification chip 1. In the mixer 3, a mixed signal f 2 , shown in Fig. 2b, is extracted and taken to the code carrier 2. The signal f 2 preferably has a frequency which is the frequency difference of the signals f, and f 0 . Fig. 3a shows the reflected signal f 2 . from the code carrier 2. This signal f 2 . has superimposed thereon the indiviual code carrier 2. Signal f 2 . is then again mixed, so that an identification coded mixing signal denoted f, is formed, as shown in Fig. 3b. As a result the transmitted and received signals f 0 , f,; f 0 , f v , have a much higher fre- quency than the signals f 2 ; f 2 . which are used internally in the indentification chip 1. In Fig. 4 is shown a specific embodiment of present invention. An identification chip 1 comprises a SAW-component 2 of per se known kind. The antenna 4 is an aperture-connected microstrip antenna. Furthermore, the mixer 3 from Fig. 1 comprises a diode 5. The antenna 4 is connected to a transducer 7 via an impedence match 6. The transducer 7 converts the electronic signal to and from a surface acoustic wave. The antenna 4 receives signals with frequencies f, and f 0 . These signals are mixed by a diode 5, so that a mixed difference signal is transferred to the transducer 7 and is converted to a surface acuostic wave for the code carrier 2. In a further embodiment the mixing signal can come from a frequency source which is internal of the identification chip. It is also possible to use this technology with other kinds of code carriers, such as BAW (Bulk Acoustic Wave). The mixer 3 may constitute more than one diode, or be acheived in other ways which are known to the person skilled in the art.

Claims: Claims: 1. Method for individual identification using electronic intenogation by transmis¬ sion and reception of signals of a certain frequancy from a transmitter/receiver unit, wherein an identification chip (1), comprising a inactive code carrier (2), such as a SAW-component, and an antenna (4), where the antenna (4) receives the transmitted signal which then is applied to the code carrier (2), and a signal, superimposed with the individual code of the code carrier, is reflected from the code carrier (2), characterized by comprising the following steps: transmission, from the transmitter/receiver unit, of a first and a second signal (f 0 , fi) of different frequencies, mixing the two signals (f 0 , f,) after reception thereof by the antenna (4), to provide a third signal (f 2 ), having a frequency which is a combination of the frequencies of the first and the second signals (f 0 , fj), applying the third signal (f 2 ) to the code carrier (2), so that the code carrier ref¬ lects a first coded signal (f 2 .) having a frequency conesponding to the frequency of the third signal (fj), mixing the first coded signal (f 2 .) with the first transmitted signal (f 0 ) resulting in a second coded signal (f r ), having a frequency conesponding to the frequency of the second transmitted signal (f,), and reflecting the second coded signal (f r ) to the transmitter/receiver unit. 2. Identification chip for individual identification using electronical interrogation by transmission and reception of a signal from a transmitter/receiver unit, having a certain frequency, where the identification chip (1) comprises an inactive code carrier (2), such as a SAW-component, and an antenna (4), where the antenna (4) is provided for receiving the transmitted signal, which then is applied to the code carrier (2), and the code carrier (2) provides a reflected signal superimposed with the individual the code of code carrier (2), characterized by the antenna (4) being provided to receive two signals (f 0 , f,) having different frequencies, a mixer (3), provided for mixing the two signals (f 0 , fi) resulting in a third signal (f 2 ) having a frequency which is the combined frequencies of the first and the second signals (f 0 , f,), a signal path (6, 7) provided for applying the mixed signal (f-) to the code carrier (2), for the provision of a reflected, coded signal (f 2 .) from the code carrier, wherein the signal path (6, 7) applies the reflected, coded signal (f 2 .) to the mixer (3), and the mixer is further provided for mixing the reflected, coded signal (f 2 .) with one of the transmitted signals (f 0 ) for the provision of a second coded signal (f r ) having a frequency conesponding to the second transmitted signal (f,), and which is supplied to the antenna (4) for reflection to the transmitter/receiver unit. 3. Identification chip according to claim 2, characterized by the signal path (6, 7) comprising a transducer (7). 4. Identification chip according to claim 2 or 3, characterized by the mixer (3) comprising a diode (5). 5. Identification chip according to claim 2 or 3, characterized by the mixer (3) comprising a plurality of diodes (5). 6. Identification chip according to any one of claims 2-5, characterized by the signal path (6, 7) further comprising a inactive network (6) for impedance matching. — 7. Identification chip according to any one of claims 2-6, characterized by the antenna (4) comprising a plurality of aperture connected micro strip antennas. 8. Identification chip according to any one of claims 2-6, characterized by the code carrier (2) being a SAW (Surface Acoustic Wave) - component. 9. Identification chip according to any one of claims 2-6, characterized by the code carrier (2) being a BAW (Bulk Acoustic Wave) - component. 10. Identification chip according to any one of claims 2-6, characterized by the code carrier (2) comprising a frequency source.

Inventors: KIRKNES STEFFEN, KIRKNES, STEFFEN
Applicants: KIRKNES STEFFEN, MICRO DESIGN AS
Application year: 1993
Main classification: H04B1
IPC codes: G01S13, H04B1