I tried to use a single directional coupler to create a reflectometer and was hoping to measure both amplitude and phase of reflected signal.

My setup is a follows:

The directional coupler is from MiniCircuits ZFDC-10-182-S+

^{simulate this circuit – Schematic created using CircuitLab}

I have tested my design with different loads, 0R, 50R, 100R, 100R||3.3pF ect.

But only the magnitude (VMAG) measurements are correct, the phase (VPHS) measurements does not seems to be correct. And I cannot find any relation, between different loads and expected vs. measured phase.

So should it possible to measure phase information with a directional coupler?

Or am I doing it wrong ?

My measurement:

50R: VPHS=0.88V, VMAG=0.16V

Open: VPHS=1.242V, VMAG=0.763V

Short: VPHS=0.282V, VMAG=0.69V

100R: VPHS=1.455V, VMAG=0.50V

100R||10pF: VPHS=0.58V, VMAG=0.66V

100R||3.3pF: VPHS=1.18V, VMAG=0.57V

I tried to use a single directional coupler to create a reflectometer and was hoping to measure both amplitude and phase of reflected signal.

My setup is a follows:

The directional coupler is from MiniCircuits ZFDC-10-182-S+

^{simulate this circuit – Schematic created using CircuitLab}

I have tested my design with different loads, 0R, 50R, 100R, 100R||3.3pF ect.

But only the magnitude (VMAG) measurements are correct, the phase (VPHS) measurements does not seems to be correct. And I cannot find any relation, between different loads and expected vs. measured phase.

So should it possible to measure phase information with a directional coupler?

Or am I doing it wrong ?

My measurement:

50R: VPHS=0.88V, VMAG=0.16V

Open: VPHS=1.500V, VMAG=0.76V

Short: VPHS=0.282V, VMAG=0.69V

100R: VPHS=1.455V, VMAG=0.50V

100R||10pF: VPHS=0.58V, VMAG=0.66V

100R||3.3pF: VPHS=1.18V, VMAG=0.57V

Edit: My open load now seems correct, before I measured open load as "no load" in the cable, but this resulted in a capacitance in the cable end SMA connector. I have now made an open load as an trimmed down SMA connector. I still don't get why the magnitude i higher, but that is maybe related to the load on the source being changed.

I tried to use a single directional coupler to create a reflectometer and was hoping to measure both amplitude and phase of reflected signal.

My setup is a follows:

The directional coupler is from MiniCircuits ZFDC-10-182-S+

^{simulate this circuit – Schematic created using CircuitLab}

I have tested my design with different loads, 0R, 50R, 100R, 100R||3.3pF ect.

But only the magnitude (VMAG) measurements are correct, the phase (VPHS) measurements does not seems to be correct. And I cannot find any relation, between different loads and expected vs. measured phase.

So should it possible to measure phase information with a directional coupler?

Or am I doing it wrong ?

I tried to use a single directional coupler to create a reflectometer and was hoping to measure both amplitude and phase of reflected signal.

My setup is a follows:

The directional coupler is from MiniCircuits ZFDC-10-182-S+

^{simulate this circuit – Schematic created using CircuitLab}

I have tested my design with different loads, 0R, 50R, 100R, 100R||3.3pF ect.

But only the magnitude (VMAG) measurements are correct, the phase (VPHS) measurements does not seems to be correct. And I cannot find any relation, between different loads and expected vs. measured phase.

So should it possible to measure phase information with a directional coupler?

Or am I doing it wrong ?

My measurement:

50R: VPHS=0.88V, VMAG=0.16V

Open: VPHS=1.242V, VMAG=0.763V

Short: VPHS=0.282V, VMAG=0.69V

100R: VPHS=1.455V, VMAG=0.50V

100R||10pF: VPHS=0.58V, VMAG=0.66V

100R||3.3pF: VPHS=1.18V, VMAG=0.57V