The Work of CISPR Sub-Committee A Radio Interference Measurements and Statistical Methods

Abstract

A review is made of the CISPR specifications for radio interference measuring apparatus, in par­ ticular with quasi-peak detectors. Other equip­ ment specified for general measuring methods as artificial mains networks, antennas and the absorbing clamp are also presented. A couple of topics in the present work of Sub-Committee A are mentioned. Terms of reference The terms of reference for Sub-Committee A in­ cludes measuring apparatus and general mea­ suring methods. Statistical methods of evalua­ tion are incorporated as well (but not discussed in this paper). Measuring apparatus CISPR has defined specifications for radio in­ terference measuring apparatus in the fre­ quency bands 10—150 kHz, 0.15—30 MHz, 3 0 -3 0 0 MHz and 3 0 0 -1 000 MHz. The apparaFrequence de repetition des impulsions en hertz Pulse repetition frequency in hertz Figure 1 Pulse response curve for 0.15 30 MHz measuring apparatus tus are in the first place intended to measure impulsive interference such as is generated by electric motors, switches, thyristor controls, ig­ nition systems etc. The oldest of the specifications is the one valid for the frequency range 0.15—30 MHz. It aims at specifying a measuring equipment which as good as possible gives readings corresponding to the subjective annoyance caused by im­ pulsive interference when listening to AM sound broadcasting. The specification is based upon investigations made already in the 1930’s. It was then found that the best way to carry out the measurements was to use a quasi-peak de­ tector with specific time constants. Another basic parameter is the i.f. bandwidth which is standardized to 9 kHz at 6 dB down. Figure 1 gives the specified relation between the sen­ sitivity of the measuring apparatus and the rep­ etition rate of identical impulses, for a constant meter reading. CH2294-7/86/000-0100 $01 -00(C)1986 IEEE 100