A Passive Surface Acoustic Wave Identification Tag ("SAW-ID tag") device utilizes pulse compression techniques and a large number of coding possibilities for identifying articles at enhanced ranges. The SAW-ID tag device provides a piezoelectric substrate having bus bars, spaced electrode taps between the bus bars and a built-in antenna, with an input chirped SAW transducer having a dispersive, complementary matched filter response to an input expanded chirp signal from an expanded linear FM chirp waveform actively generated by a nearby chirp transmitter. The input expanded chirp signal is fed into the input chirped SAW transducer through the built-in antenna, to compresses the input expanded chirp signal into a narrow, compressed pulse signal propagating toward the electrodes taps. The spacing of the electrode taps establishes the desired unique time-ordered coding. The electrode taps sample the narrow, compressed pulse signal and provide narrow, compressed pulse samples propagating a coded, pulse train output transmitted via the antenna to a nearby interrogation means to identify the tagged article. The preferred embodiment is an SAW-ID tag device with a piezoelectric quartz substrate about 1 inch long, a built-in dipole antenna and five (5) spaced electrode taps, establishing several million coding possibilities. Also disclosed are methods of identifying articles using an SAW-ID tag device, and methods of selectively disconnecting and connecting electrodes to facilitate mass production.

A technique of providing numerous distinct conductive patterns on a piezoelectric substrate is accomplished using only two masking apparatus. One masking apparatus defines a common portion or structure for each of the patterns. The second masking apparatus defines numerous distinct patterns, each corresponding to a different alignment position with respect to the common structure already formed on the substrate. One application for this technique is in economic production of coded SAW devices which may serve as coding or decoding devices, filters, or correlators, each of the SAW devices having a different individual code.

In a passive surface wave sensor for measured value determination, a measured value is transmitted by radio from a remote measuring location to an interrogation device, which transmits energy by radio to a sensor element as an interrogation pulse. The surface wave sensor is suitable for contactless measured value acquisition. A surface wave configuration is the sensor element and a surface wave reference element is provided for phase discrimination and/or propagation time measurement. As a further development, a sensor operated with chirped transmitting signals and having chirped reflectors is provided, in which the configuration has a reference function in place of the reference element. A sensor constructed in such a way that it has a chirped function has the characteristics of an imminently temperature-compensated sensor for measuring other physical or similar variables.

A coding scheme is specified which, compared to the prior art and with the system having a structure resolution of the same magnitude, allows an enlarged code size for the same number of code elements, and/or by which fewer code elements are required per code for a predetermined code size. The code elements are disposed with basic values in a matrix defined in a novel manner, with the matrix having a finer subdivision of the basic values than the subdivision corresponding to the structure resolution. Further development with mean-value formations are possible.