GB1496205A - Wire-less transmission of items of data between active interrogation devices and passive response devices - Google Patents

Abstract

1496205 Remote interrogation of passive response devices SIEMENS AG 15 April 1975 [24 May 1974] 15325/75 Heading H4L [Also in Division B7] In a system comprising passive response devices each containing resonators having different resonant frequencies scanned by a frequency-sweep interrogation signal from an active interrogation device, when the usable frequency band of the interrogation signal is smaller than the frequency band required for transmission, the resonators of a response device are divided into two or more groups of resonators whose resonant frequencies all lie within the usable frequency band and are interrogated consecutively. The system may be used for the location or identification of railway locomotives (Figs. 1-2, not shown), the interrogation and response devices being respectively in the train and on the track, or vice-versa. Part of the frequency band may be rendered unusable temporarily as a result of local interference with or by an external signal field (Fig. 3, not shown). If, for example, part 9-13 of a frequency band 1-13 is rendered unusable, the response device c may be replaced by two devices cl, c2 each covered by a frequency range (f u , f o <SP>1</SP>) instead of the whole range (f u ,f o ). Alternatively, the lower or middle part of the range may be unusable (figs. 5, 6. not shown) when the devices are limited to the same or different frequency sub-ranges (f u <SP>1</SP>, f a ) or (f u -f u <SP>11</SP>, f o <SP>11</SP>-f o ). An interrogation device a, Fig. 7 for vehicle location may contain a microwave unit m1 comprising an interrogation signal transmitter 15, a frequency control device 16 and means 14 for switching between two antennµ b 1 , b 2 (e.g. one for each rail). The incoming signal contains bits TI, TZ indicating respectively that temperature compensation is required (detected by a device 20) and whether the signal is from one device C or two partial devices Cl, C2. The signal passes to an amplifier 18 whose output causes a device 23 to operate switches 14, 17 to select the antenna receiving the signal, and to a pulse shaper 19 and a code checking device 21 from which a number output 25 is derived. A device 24 determines whether temperature compensation is required and whether the signal is in one or two parts, and controls device 16 and an output unit 22 according- ly. Other embodiments (Figs. 8, 9, not shown) may be used for vehicle identification. The groups of resonators may respond to interrogation signals of different polarities (Figs. 10, 12, not shown). A high power signal may be transmitted with the frequency-sweep signal to select groups for interrogation in dependence on its frequency, attenuation in the response device being by microwave diode (Figs. 11, 13, not shown). Command signals may also be transmitted.