This example is a resistor-capacitor circuit (RC) driven by a voltage source. The circuit is built by using electrical linear elements. The circuit is designed to provide a cut off frequency of 4 GHz. The example file is rc_circuit.icp.
Fig 1. RC filter circuit
Circuits with elements that support ‘Electrical Node’ ports should be built as a sub-circuit using a Compound Element. The Compound Element scattering data solver allows for solving electrical circuits in time and frequency domain.
Fig 2. Compound Element solver using the scattering data analysis option
In this application example, the Optical Network Analyzer will calculate the filter complex transmission using the impulse response option. When using the impulse response, elements connected to the network analyzer will run in time domain. The Compound Solver will calculate the complex transmission of the RC filter and generate the equivalent digital filter of the device, allowing for time domain simulations. The complex transmission of the filter is depicted in the figure bellow, the 3dB cut off is 4GHz.
Fig 3. RC filter transmission, the measured cut off frequency is 4 GHz
S Parameters from electrical linear circuits
The Electrical Network Analyzer can measure s-parameters using a scattering data analysis solver. To measure the s-parameter of an electrical linear circuit at a given reference impedance, a Voltage Reference Port element should be used. The Reference Port element converts the electrical signal from the network analyzer output to the proper electrical wave parameters required as input and output values in the electrical circuit.
The circuit below is a band pass filter built using RLC (resistor, inductor, capacitor) elements. The example file is rlc_circuit.icp.
Fig 4. Band pass filter circuit using RLC elements
To measure the s-parameter, a matched load is required. The load impedance and the source impedance are typically set as the characteristic impedance, in this case the value is 50 Ω.
Fig 5. Device under test for characteristic impedance of 50 Ω
By adding one reference element to each port of the device, the network analyzer can measure the device's s-parameter at the given user defined impedance (50 Ω). Combining the Electrical Network Analyzer with the Reference Port Element allows comprehensive characterization of bidirectional electrical circuits at arbitrary input and output impedance.
Fig 6. Transmission (S21) and reflection (S11) s-parameters measured at 50 Ω