For this example, we have an external force driving a spring
which is terminated on the other end at a rigid wall.
Figure F.16 shows the physical diagram
and the electrical equivalent circuit is given in
External force driving a spring terminated
by a rigid wall.
Electrical equivalent circuit of the compressed
spring of Fig.F.16.
Figure F.18 depicts the insertion of
an infinitesimal transmission line, and
Fig.F.19 shows the result of converting the spring
impedance to wave variable form.
Intermediate equivalent circuit for the
force-driven spring in which an infinitesimal transmission line
section has been inserted to facilitate conversion of the spring
impedance into a wave-variable reflectance.
Intermediate wave-variable model of Fig.F.17.
The two-port adaptor needed for this problem is the same as that for
the force-driven mass, and the final result is shown in
Note that the spring model is being driven by a force from a zero
source impedance, in contrast with the infinite source impedance
interpretation of Fig.F.8b as a compressed spring. In this
case, if the driving force goes to zero, the spring force goes
immediately to zero (``free termination'') rather than remaining
Next Section: Spring and Free MassPrevious Section: Force Driving a Mass