Example Of Using Fixture Simulator; Measurement Circuit Example For A Dut With Balanced Port; Evaluation Using An Actual Test Fixture - Agilent Technologies ENA Series User Manual

Fixture Simulator

Example of Using Fixture Simulator

Example of Using Fixture Simulator
In this section, the fixture simulation function is explained based on an evaluation example
for a DUT (balanced SAW filter) with a balanced port.

Measurement circuit example for a DUT with balanced port

Figure 7-20 shows an example of a measurement circuit used to evaluate a balanced SAW
filter. DUT port 1 is an unbalanced port connected to source impedance Rs and input
matching circuit L1. DUT port 2 is a balanced port connected to an output matching circuit
(C1, C2, and L2) and load resistance RL.
Figure 7-20 Measurement circuit of balance SAW filter

Evaluation using an actual test fixture

Generally, a test fixture as shown in Figure 7-21 is fabricated for evaluating the
characteristics of a DUT in a measurement circuit by using a network analyzer.
In typical use, a network analyzer performs measurements at a 50 Ω port reference
impedance and in a single-ended (unbalanced) state. Therefore, DUT port 1 can be
connected directly to the test port of the network analyzer.
On the other hand, DUT port 2 is a balanced port that cannot be connected directly to the
test port of the network analyzer. Usually, a balun (BALance-UNbalance transformer) is
used to convert the DUT's balanced port to an unbalanced port and to connect the
converted port to the test port of the network analyzer. Matching circuits are mounted in
the test fixture as shown in Figure 7-21.
306 Chapter 7