X3C19P1-05S Datasheet, PDF (13/22 Pages) Anaren Microwave – 5dB Directional Coupler

Model X3C19P1-05S
Rev B
In terms of S-parameters, IL_therm can be computed as follows:
IL_therm = −10 ⋅ log_{10 } S₁₁ ² + S₂₁ ² + S₃₁ ² + S₄₁ ² _{} (dB)
(5)
The thermal resistance and power dissipated within the unit are then used to calculate the average total input power
of the unit. The average total steady state input power (P_in) therefore is:
∆T
P_in
=
P_dis
¹
−
10
−
IL_therm
10

=
R
¹
−
10
−
IL_therm
10

(W )
(6)
Where the temperature delta is the circuit temperature (T_circ) minus the mounting interface temperature (T_mnt):
∆T = T_circ − T_mnt (^oC)
(7)
The maximum allowable circuit temperature is defined by the properties of the materials used to construct the unit.
Multiple material combinations and bonding techniques are used within the Xinger III product family to optimize RF
performance. Consequently the maximum allowable circuit temperature varies. Please note that the circuit
temperature is not a function of the Xinger case (top surface) temperature. Therefore, the case temperature cannot
be used as a boundary condition for power handling calculations.
Due to the numerous board materials and mounting configurations used in specific customer configurations, it is the
end users responsibility to ensure that the Xinger III coupler mounting interface temperature is maintained within the
limits defined on the power derating plots for the required average power handling. Additionally appropriate solder
composition is required to prevent reflow or fatigue failure at the RF ports. Finally, reliability is improved when the
mounting interface and RF port temperatures are kept to a minimum.
The power-derating curve illustrates how changes in the mounting interface temperature result in converse changes
of the power handling of the coupler.
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