be connected directly to the radiator halves 11 12 of the reflecting antenna element 10 or can u2014 as depicted in fig1 u2014 be connected to the radiator halves 11 12 via a converter device 9 this converter device 9 can convert an output quantity of the load impedance 8 into an impedance or a voltage so that interconnecting the load impedance 8 and the converter device 9 creates a passive sensor with wireless readout for physical or chemical measured values of the system states of the technical system 7 0030 fig2 is a frequency diagram power density s f as a function of frequency f of a radio signal 13 with a frequency f transmitted by an evaluating antenna element 1 cf fig1 a radio signal 14 reflected by a reflecting antenna element 10 has a reflection frequency f r which corresponds essentially to the transmission frequency f moreover additional reflection frequencies f r1 to f r4 appear in sidebands of the reflected radio signal 14 while the transmitted radio signal 13 of the evaluating antenna element 1 is thus found in a narrow main band region the reflected radio signal 14 of the reflecting antenna element 10 also includes frequency components f r1 f r4 in sideband regions so that there is no interference or only very minor.