Sampling Setups for Antenna Fields
In electromagnetic field solvers a concept called field monitor or field request (or similiar) is very common: The desired electromagnetic fields are not calculated everywhere in space but only on a limited set of points defined in the field request. This saves resources and makes the computation of the electromagnetic fields feasible in the first place.
In AntennaFieldRepresentations.jl, a similar concept exists. A FieldSampling is a struct which defines the positions in which the electromagnetic fields of an AntennaFieldrepresentation shall be sampled. Furthermore, many Fieldsamplings allow to take the receive pattern of a realistic probe antenna into account. This way, rather complex and realistic antenna measurement setups can be modelled.
A FieldSampling can be used to create a TransmissionMap, a functional relationship between the coefficients of an AntennaFieldRepresentation and the output signals of the probe antennas defined by the FieldSampling[1]. The TransmissionMap serves as a linear operator (a matrix) between the coefficient vector of the AntennaFieldRepresentation and the vector of output signals of the probe antennas. Depending on the specific types of the AntennaFieldRepresentation and the FieldSampling, the algorithm implementing the matrix-vector product for the TransmissionMap will change. Particularly efficient algorithms arise for certain combinations of AntennaFieldRepresentations and FieldSamplings.
Every FieldSampling reserves a storage for the measured values of the $S_{21}$-parameter between the probe antennas and an AntennaFieldRepresentation. Internally, the storage can have various forms to best match the situation described by the FieldSampling implementation. However, all FieldSamplings implement a common interface which let the user access the storage for the measured $S_{21}$-parameters a Base.AbstractVector.
Implementations of the type FieldSampling support the interface of Base.AbstractVector. In particular the methods Base.getindex and Base.setindex! are supported which allow to access the measurement vector by indexing the struct representing the fields directly by square brackets [].
FieldSampling Interface
Any subtype of FieldSampling implements the following methods[2]:
| Method name | Optional | Fallback method | Short Description |
|---|---|---|---|
Base.size | No | See interface of Base.AbstractVector | |
Base.getindex! | No | See interface of Base.AbstractVector | |
Base.setindex | No | See interface of Base.AbstractVector | |
Base.similar | No | See interface of Base.AbstractVector | |
asvector | No | Return the measurement samples as a vector |
- 1Hertzian dipoles (short electric dipoles) and Fitzgerald dipoles (short magnetic dipoles) can formally be used as probe antennas to directly sample electric and magnetic fields of an
AntennaFieldRepresentation: Their output signals are directly proportional to the electric and magnetic field component which is parallel to their dipole orientation, respectively. - 2Note for developers: If you want to implement your own subtype of
FieldSampling, make sure to support this interface to adhere to the general functionality of this package.