Optenni Lab — Calculation of radiation efficiency

Optenni Lab calculates the antenna radiation efficiency from the impedance and measured total efficiency data, which do not have to use the same frequency grid. The impedance (S-parameter) data is read from a Touchstone file and the radiation efficiency data is read from a text file where possible comment rows will be ignored and the data can be specified using different frequency units (e.g. MHz or GHz) and either in linear of dB scale. The coupling to other antenna ports will be taken into account in the calculation of the radiation efficiency.

In addition, when a matching circuit has been constructed, Optenni Lab calculates the total efficiency through the circuit, taking into account impedance mismatch, losses in the matching circuit, the radiation efficiency and coupling to the other antennas.

Optenni Lab — Calculation of electromagnetic isolation

In the analysis of isolation between two antennas, it is well known that the matching of both antennas affects the isolation. To remove the effect of antenna matching Optenni Lab can calculate the so called electromagnetic isolation where at each frequency two antenna ports have been simultaneously conjugate matched and the other ports are terminated with given impedances. For two-port systems, the electromagnetic isolation gives the worst-case isolation and the obtained isolation is always better than this due to impedance mismatch. The concept of electromagnetic isolation is used e.g. in the analysis of diversity antennas.

Electromagnetic isolation calculation allows you to

  • Quickly calculate the effect of antenna placement to isolation by normalizing the matching of both antennas
  • Show the effect of an isolating element (e.g. metamaterial) to obtainable isolation
Electromagnetic isolation
Antenna S-parameters of a two-port antenna system and the calculated electromagnetic isolation, all in dB.

More information

For more information about the concept of electromagnetic isolation, see for example
 

Optenni Lab — Automatic matching circuit synthesis

Optenni Lab's matching circuit synthesis is fast and easy to use. You do not need any impedance matching or circuit simulation skills to optimize matching circuits in Optenni Lab. You can generate matching circuits in less than ten seconds using the four steps at right.

Within seconds, Optenni Lab synthesizes, optimizes and ranks a number of circuit topologies. For each generated circuit, Optenni Lab shows the circuit topology, the S parameters of the matching circuit and the input impedance on the Smith chart.

In matching circuit generation you can also:

  • Take into account losses in matching circuit components
  • Use inductor and capacitor models from a component library
  • Specify the topology manually
  • Fix some component values
  • Set upper and lower limits for the component values
  • Carry out tolerance analysis
  • Tune the generated circuits interactively

In manually created topologies you can use the following components:

  • Inductors
  • Capacitors
  • Resistors
  • Transmission lines
  • 2-port S parameter blocks (e.g. accurate component models)

The components can be placed in series and parallel or inside hierarchical parallel and series resonators. Thus it is possible to define and optimize quite complex matching circuit topologies.

For each frequency range in the pass band, a different target level for efficiency can be specified. In addition, stop band attenuation targets can be given.

Note that matching circuit synthesis works with arbitrary frequency-dependent complex termination impedances. The S parameters of the circuit are calculated using the theory of power waves, which correctly describes the propagation of power in the matching circuit.

Procedure for matching circuit generation


1. Read in the impedance file in Touchstone format
menu touchstone

2. Select the frequency ranges from a menu
Select frequency range


3. Select the number of components in the circuit
Select number of components


4. Press OK.
Press OK

Optenni Lab — Estimation of obtainable bandwidth

Optenni Lab offers tools for estimating the obtainable bandwidth from antenna impedance curves using the bandwidth potential  and Q factor approaches.

Bandwidth potential

In the bandwidth potential calculation, Optenni Lab constructs for each frequency a two-component matching circuit and calculates the obtained maximal impedance bandwidth. It repeats the analysis for all frequencies and gives a curve that shows what kinds of bandwidths can be obtained at different frequencies.

With the bandwidth potential calculation you can

  • Compare differently matched antennas to show which one offers best obtainable bandwidth
  • Verify if the bandwidth is large enough for the desired application even if the antenna was not originally resonant
  • Check on which frequencies the antenna gives maximal bandwidth

The bandwidth potential calculation speeds up the antenna design process. You can quickly estimate the obtainable antenna bandwidth from a measured or simulated prototype without explicitly tuning the antenna to resonance at the desired frequency range. If the bandwidth is not sufficient, you can modify the design and calculate the bandwidth potential until the specifications have been met. Then you can tune the antenna to resonance by changing the antenna geometry or by generating a matching circuit with Optenni Lab.

Optenni Lab offers two ways of calculating the bandwidth potential:

  1. Standard: At each frequency, the impedance is conjugate matched to the generator impedance and the symmetric impedance bandwidth is recorded at a desired matching level.
  2. Optimized: At each frequency, the symmetric bandwidth through a two-component matching circuit is maximized and this bandwidth is recorded.

 

Bandwidth potential
Example of standard and optimized bandwidth potential. The vertical axis is relative bandwidth as a percentage of the center frequency.

 

Q factor estimation

In addition, Optenni Lab can estimate the antenna Q factor based on the impedance data directly. This method is less accurate than the bandwidth potential calculation especially if the impedance data is noisy or if multiple resonances are present.

More information

For the theory of the bandwidth potential calculation, see for example The Q factor calculation is explained in
 

Optenni Lab — Conjugate matching

In addition to general matching circuit optimization, Optenni Lab calculates two-component matching circuits that obtain conjugate matching to the generator impedance at a single frequency (critical coupling) or maximize the bandwidth around the starting frequency at a given matching level (overcoupled matching). Either the total bandwidth or the symmetric bandwidth around the starting frequency is maximized. Also the two-component matching circuit generation works with an arbitrary frequency-dependent complex termination impedance. When the termination impedance is real (e.g. 50 Ohm), an exact match can be obtained at a single frequency.

The difference between the two matching circuit generation approaches in Optenni Lab is that the general matching circuit generation tries to obtain as good matching as possible over a given frequency range and a given number of components, whereas the two-component matching tries to maximize the bandwidth at a given matching level.

The conjugate matching and symmetric bandwidth maximization procedures are used in the calculation of the bandwidth potential.

 
Matching to 50 Ohm
Matching to 50 Ohm
Impedance matching with optimized bandwidth
Matching with optimized symmetric bandwidth