The Reference Signal Path
The Test Signal Path
The S11 and S21
Measurements
The Sampler Control Switching
Troubleshooting the Test Set
Theory of Operation
•The reference signal is routed from the switch/splitter through the
•The signal is then applied to A10, the a1 sampler assembly, where it is
•Because the RF power is being routed to Port 1, the a1 IF signal is used to phase lock the network analyzer. Had the RF power been routed to Port 2, the a2 IF signal would have been used to phase lock the network analyzer.
•The test signal is routed from the switch/splitter (A18) to the 60 dB programmable attenuator (A16) for Port 1.
•The signal may then be attenuated in 10 dB steps or passed through without attenuation to Port 1 bias tee (A7).
•A bias supply to provide dc voltage to Port 1 bias tee can be connected to J8 on the rear panel of the test set, also.
•The RF signal rides this dc level which is used to turn active devices on (bias ON) so their
•Beyond the bias tee, the test signal travels to the directional coupler (A6).
•At the coupler, the incident RF power is applied to the device under test.
•The signal reflected from the DUT is separated from the signal incident to the DUT by the Port 1 coupler (A6).
•The reflected signal exits the coupler and is applied to b1 sampler (A12), then is
•The S11 measurement is the ratio of the two IF signals from a1 and b1 samplers.
•The incident signal is transmitted through the DUT, through Port 2 coupler, then into b2 sampler (A13).
•The incident signal is
•The samplers may be turned on and off, depending upon the parameter being measured.
•Sampler switching is controlled by a microprocessor on the
HP 8517B