eldo_user

Optimization
Types of Design Objective
Range Constraints Objectives
This topic explains how to specify design objectives that define bounds on extracted measures.
These types of objectives are called equality constraints or range constraints and correspond to
relations such as l≤ f i (x) ≤ u.
Equality constraints are range constraints with equal lower and upper bounds: l=u.
Objectives that define ranges on measures are specified using the .OBJECTIVE command by:
* Range constraint
.OBJECTIVE EXTRACT_INFO LABEL=F_I
+ {$MACRO|FUNCTION}
+ LBOUND=L UBOUND=U
When the objective f i does not need to be bounded by a lower or an upper value, the parameters
may be omitted. For example, if a design objective must be positive f i ≥ 0 (its lower bound is 0),
you can specify the following:
* Positive objective
.OBJECTIVE EXTRACT_INFO LABEL=F_I
+ {$MACRO|FUNCTION}
+ LBOUND=0.0
The Eldo Optimizer SQP Algorithm handles them directly as hard constraints. These objectives
must be satisfied at the solution of the problem.
Notes
• The iterates (the successive values of design parameters taken during optimization) may
not satisfy the constraints. If the optimization problem appears to be feasible, the
constraints will be satisfied at the solution, or in the vicinity of a solution.
• In general, inequality constraints are more relevant than equality constraints as
equalities are more difficult to satisfy. Consider the objective of fixing the input power
matching of a low noise amplifier at a frequency of 2.4GHz:
.EXTRACT AC LABEL=S11_dB@2.4GHz YVAL(SDB(1,1),2.4G)
+ GOAL=-15
A more appropriate objective is to specify a tolerance on the target value, for example
±1dB.
The Eldo optimizer SQP method does not enable you to specify a tolerance on equality
constraints. Instead you can combine GOAL objectives to center the design and range
constraints with the same objective in separate statements.
• The limitation above also means that equalities and inequalities are mutually exclusive.
The parameter EQUAL cannot appear inside the same objective statement as the
parameters LBOUND and UBOUND.
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Eldo® User's Manual, 15.3