Signal Separation; A24 Transfer Switch - HP 8753E Service Manual

Signal Separation

The analyzer's test port couplers are used to separate signals incident to,
reflected from, and transmitted from the device under test. Each test port
coupler has a coupling coefficient factor of 16 dD.
The LED front panel board indicates whether the source power is incident on
the analyzer's test port 1 or test port 2. The analyzer's source power is directed
to test port 1 when making a forward transmission/reflection measurement.
Similarly, source power is incident at test port 2 when making a reverse
transmission/reflection measurement.
The A3 source output power is directed to either the analyzer's test port 1 or
test port 2 via a low loss solid state transfer switch. With this switch, all four
S-parameters can be updated continuously (for example: the data obtained from
a full 2-port calibration). In addition, the transfer switch provides termination
for the inactive test port in order to minimize the crosstalk between the source
and receiver sampler.
The test set interface board provides biasing for active devices under test with
an external dc voltage. This dc voltage is applied directly to the test port center
pm. In addition, the test set interface board provides the drive signal for the
12-26 Theoryof Operation