PWB
PWB
Product by :
ONERA
Scope :
POWER BALANCE (PWB) models are developed in order to qualify and quantify electromagnetic interactions induced in an electrically large system from a macroscopic point of view.
Features :
The PWB code addresses EM problems in a frequency range where the system under test is larger than the wavelength. The method is a based on a statistical description of EM phenomena (as in a Mode Stirring Reverberating Chamber) and conservation of energy in oversized enclosures.
The entire EM problem is modelled as a topological network (as in classical EM topology) where nodes represent absorption phenomena, transfer of energy between EM volumes…
All elementary EM phenomena (or nodes) are supposed to be independent from each other and are therefore quantified via a coupling cross section. Finally, this network is solved via the BLT equation (as in CRIPTE for multiconductor transmission line applications) and mean power density/mean dissipated power at each node extremity of the initial network are calculated. This approach makes the assumption of linear EM problems and is developed in frequency domain.
In HIRFSE, the PWB approach is an elementary brick of the proposed highfrequency scenario to solve the internal EM problem, the external environment being solved by any computer code able to calculate this environment at high frequency. In HIRF SE practical validations of coupling with OKTALSE’s SERAY asymptotic code have been demonstrated.
Figure 1: High Frequency scenario proposed in HIRFSE including PWB approach
Consequently, to solve an EM problem at high frequency with the POWER BALANCE approach and computer code, one has to :

Build the interaction diagram and its corresponding topological network by listing and linking all EM interactions and EM dissipative phenomena inside the system under test. An example is given below in Figure 2. The user can create, characterize and modify networks.
Figure 2: Example of an EM problem and its modelling via the POWER BALANCE approach

Quantify and characterize all nodes of this network through coupling cross section (CCS) models. The coupling cross section is defined as the ratio between a dissipated power of a component and power density seen by this component. Under the assumption of independency of EM interactions, validated models of CCS of typical EM phenomena are available in the existing code :
 losses in metallic and dielectric walls,
 antennas,
 dielectric “pseudo spherical” objects,
 absorbing objects which have been experimentally characterized,transfer through apertures when EM environment on both sides are pseudo randomized (EM environment are considered as random plane wave spectrum, similar to EM environment in MSRCs). Various geometries of apertures can be considered (circular, slots, rectangular, ellipsoid, circular and rectangular gaskets, loaded apertures..)
 wires. Wires are models as dissipative objects. In this case, this model is derived from the antenna theory.

Define source terms as incident power density generator or power generator. The PWB code is also able to process Efields and Hfields computed by a 3D code on identified points of entry of the incident EM interference (as cockpit or windows for example).

Solve the BLT equation implemented in the PWB code in order to get induced mean power density and/or induced mean dissipated power at each extremity of branches and nodes.
Moreover, PWB offers the opportunity to compute and save mean CCS of the above mentioned EM phenomena but also equivalent CCS of subnetworks in order to store them in a data base and reuse them if necessary in other EM problems.
Screenshots :
Figure 3: The PWB code in the CuToo platform
Figure 4: Combined application of PWB with SERAY on Evektor’s VUT100 and implementation in the framework (courtesy Evektor, EMCC and OKTALSE)
Figure 5: Application of PWB approach on Dassault’s F7X aircraft (HIRFSE): topological results and application of HIRF SE’s passfail criteria approach (courtesy Dassault)
References :

I. Junqua, JP. Parmantier, F. Issac,
A network formulation of the PWB method for high frequency coupling,
Journal of Electromagnetics, October 2005

I. Junqua, JP. Parmantier, L. Guibert,
Assessment of high frequency coupling in a generic object by the Power Balance method,
EMC Zurich 2007, Munich, September 2007
 JP. Parmantier, I. Junqua,
EM Topology: from theory to application,
UltraWideband ShortPulse Electromagnetics 7, Sabath, F.; Mokole, E.L.; Schenk, U.; Nitsch, D. (Eds.), pp 312, 2007, XVI

I. Junqua, JP. Parmantier, F. Issac,
A network formulation of the PWB method for high frequency EM coupling applications,
Interactions Notes 576, November 2002
 Isabelle Junqua, JeanPhilippe Parmantier, Pierre Degauque,
FieldtoWire Coupling in an Electrically Large Cavity: a SemiAnalytic Solution,
IEEE Transactions on EMC, Vol 52, n°4, pp 10341040 November 2010
 Isabelle Junqua, François Issac, Martine Liénard, Pierre Degauque,
On the Power dissipated by an antenna in Transmit Mode or in Receive Mode in a Reverberation Chamber,
IEEE Transactions on EMC, Vol 54, n°1, pp 174180 February 2012
Contacts :
Solange Bertuol (solange[dot]bertuol[at]onera[dot]fr)
JeanPhilippe Parmantier (jeanphilippe[dot]parmantier[at]onera[dot]fr)
Isabelle Junqua (isabelle[dot]junqua[at]onera[dot]fr)