Instrumentation & Measurement Magazine 23-2 - 13

Practical Aspects of a Pulse
Generator Calibration
Martin Hudlicˇka, Marco A. Azpúrua, and Murat Celep

easuring receivers are used for measurement of
radio disturbance in the frequency range typically 9 kHz to 18 GHz. Such receivers can be
either electromagnetic interference (EMI) receivers or spectrum analyzers with the quasi-peak (QP) detector [1], [2].
Requirements for measuring receivers are discussed in European CISPR documents (Comité International Spécial des
Perturbations Rádioélectriques) and US standards ANSI 63.2 (QP
parts derived from CISPR). Although novel techniques are being evaluated [3], the traditional way of checking compliance
of the receiver with requirements of these standards is using
a calibrated pulse generator [4]. The calibration of pulse generators is discussed in the standard EN 55016-1-1 [5], which
is the harmonized version of the international standard IEC/
CISPR 16-1-1 (currently Ed. 4) [6]. In the standard [5], however,
only a very brief description of the methods is given and technical details are hidden. The measurement uncertainty of the
pulse generator characterization is not discussed in the standards; however, it was discussed in several previous works
[7], [8]. This paper aims to provide a more thorough description of particular calibration methods together with practical
hints which may be useful for students, calibration engineers
and practitioners.

Pulse Generators
According to [5], a pulse generator is an instrument capable of
generating time-domain rectangular pulses, or a pulse-modulated RF signal. Rectangular pulses are typically used for lower
frequencies (bands A/B) and pulse-modulated RF signals for
higher frequencies (bands C/D) because of the risk of receiver
damage due to high peak voltages. The base-band pulse generators usually comprise an energy-storage device (electrostatic,
magnetic field) and a switch which discharges a fraction or all
of the energy into a load. The pulse-modulated RF generator
uses a harmonic signal with a pulse envelope. The spectrum
is similar to a rectangular pulse (upconverted to the carrier

frequency fc), in which the maximum of the spectrum is at fc.
The spectrum is uniform in a given bandwidth, which implies
that pulses with longer duration can be used with lower amplitudes compared to base-band pulse generators (lower risk
of measuring receiver damage). The typical spectrum of a rectangular base-band pulse and a pulse-modulated RF signal is
shown in Fig. 1.
The terminology used with the pulse generator characterization is summarized in Table 1. All quantities for
characterization of pulse generators have dimensional units
V/Hz or the mathematical equivalent.

Calibration Methods
The various pulse generator calibration methods will be
demonstrated on the example calibration of the CISPR pulse
generator IGUU2916 (base-band pulse generator, manufacturer Schwarzbeck, Germany). The generator is shown in Fig.
2. The methods are compared with regards to the measurement uncertainty, feasibility and required instrumentation.
The polarity was always (+), the amplitude of the main generator (mechanical relay contact) was always 60 dBμV, the
amplitude of the auxiliary (semiconductor switch) generator
was 40 dBμV and the pulse repetition rate was changed according to the band.
In the EN 55016-1-1 [5] (CISPR 16-1-1 [6]), there are specified impulse areas of a typical generator for both open-circuit
and 50 Ω load (Table 2). The values shown in this paper correspond to the measurement of the spectrum amplitude
(calculated from the impulse area) into 50 Ω nominal load.

Fourier Transform of a Time-Domain Pulse
Waveform
The spectrum amplitude is determined by direct acquisition
of the pulse generator output voltage using an oscilloscope
and conversion into the frequency domain. For this purpose,
a digital real-time oscilloscope (DRTO) or an equivalent-time

This work was supported by the project 15RPT01 RFMicrowave. This project has received funding from the EMPIR programme
co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme.
April 2020

Instrumentation & Measurement Magazine 23-2

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