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Polyphase filter I- and Q-imbalance measurement

Question asked by MiKa on Dec 7, 2010
Latest reply on Dec 8, 2010 by MiKa
as the topic states I'm trying to measure the IQ-imbalance (amplitude + phase) of an active polyphase filter using the 4-port E5071B analyser. I've been reading the manuals a while and I need your advice on how to proceed.

Background: 2-port analysers are familiar to me. At first I tried to measure the imbalances with a 20GHz 4-channel scope but the accuracy is just not enough to get reliable measurements.

Set-up: the DUT has a differential input and differential I- and Q-outputs. So six terminals all together. According to the manual my options are the following:
1. Single-ended input - balanced output. A balun has to used at the input which creates some imbalance (might be able to de-embed). In this set-up I and Q outputs have to measured separately. Is the relative phase difference between I and Q outputs maintained? What about the settling of the circuit, can enough of delay be configured so that the measurement takes the steady-state signal?

2. Balanced input - balanced output. Same as 1. but with with balanced input. Is the input signal truly differential (on at the same time) or are the signals fed to the ports at different time points?

3. External input - 2 Balanced outputs. I couldn't find from the manuals if this type of measurement is possible. A balun has to be used at the input side, but the outputs would all be measured at the same time. I know that the GBIP bus can be used to send the *TRG command to trigger the device manually, but can the device be configured to a listen only mode and how?

Other information which has to taken into account is also greatly appreciated.