ZJ_Matching is an antenna matching network optimization tool. It is an installation‐free software. Just download and unzip the file and run the ZJ_Antenna_Matching.exe. There is another strip‐down version, ZJ_Matching_Mini, which fits into a 640 × 480 pixels monitor and can be used on a Windows®‐based vector network analyzer (VNA).

The software can be used to design a matching network for an antenna which can have up to two different scenarios, for example

1. To design a matching network for a whip–stubby antenna which has two positions: extended and retracted
2. To design an antenna matching network that gives a balanced performance between the free space and the talking position

To design a matching network for a cell phone antenna, many commercial software packages, such as Agilent ADS®, Microwave Office®, and so on, can be used. When I was working for the industry as an antenna engineer, I did feel, although those commercial codes were very powerful, they were not very efficient and were a kind of overkill when used in an antenna matching network designing, which normally uses less than four components. Thus, I decided to write this software in my spare time. The first version was written in 2003, and I have been modifying it since then. After I made my career U‐turn in 2007, the software can now be released to public.

This is a freeware, so you can use and distribute it as you wish. But I am not responsible for any consequences of using this software.

Have fun!

• File lists:

  There are seven files in the package:

  

  The values of C_value.txt and L_value.txt files are capacitor and inductor values used in the software. These values are good enough for most applications. But both files can be edited according to capacitors and inductors available to you.

• Current supported data format:
  1. TOUCHSTN.S1P
  2. TOUCHSTN.S2P (only the first port can be seen)
  3. TOUCHSTN.SNP (only the first port can be seen)
  4. CITIFILE (only the basic single segment format)
• Version History:
  1. You need to load at least one antenna data file to use the software. Two sample files, extended.s1p and retracted.s1p, are included in the software package. You can use them for practice.

     1.4.1	1 September 2007	First public release
     1.0	20 February 2003	Initial version

     1. When the software starts, only the top “load file” button is accessible.
     2. After you load the first file, the second “load file” button will be accessible. Loading the second data file is optional. If you have two scenarios, you can load the second one. When you are optimizing an antenna, both antenna scenarios share the same matching network, so you can check out the antenna response of both scenarios simultaneously. When you load two data files, both of them MUST have identical frequency span and data points. Otherwise, the software will reject the second file.

        

  2. After loading a file, the software reports some information. If you cannot see the following information, it means the data format is not compatible.
     1. The software indicates what data format the loaded file is. The software currently only supports TOUCHSTN and CITIFILE formats.
     2. The software also indicates the minimum frequency and maximum frequency of the loaded file.
     3. The plot on the Smith chart should be same as what you saw on your network analyzer; otherwise, it is most likely because you have saved the file as unformatted data which does not includes the port extension you have made. Read the user manual shipped with your VNA and save the data file as formatted data.
     4. Voltage standing wave ratio (VSWR) or return loss (RL) data should also be same as what you saw on your network analyzer.

        

  3. There are some settings you can change.
     1. You can highlight up to two interested bands. Band‐I will be marked by blue color on both the Smith chart and the VSWR/RL plots. Band‐II will be marked by green color.
     2. You can switch the display format between the VSWR and the RL.
     3. The red circle in the Smith chart is the VSWR 2 : 1 circle.
     4. In the VSWR/RL plot, the grid is 100 MHz each grid along the x‐axis. Along the y‐axis, the unit of VSWR plot is 1/grid and that of the RL plot is 5 dB/grid.

        

  4. You can modify the matching network to simulate the response in the Smith chart, the VSWR, or the RL format.
     1. If looking from antenna side, the top one is the first component. You can add up to four matching components. Each component can be series inductor (Serial L), shunt inductor (Shunt L), series capacitor (Serial C), or shunt capacitor (Shunt C). The unit for capacitor is pF and for inductor is nH.
     2. You can use pull‐down menus to adjust the matching component value. If you cannot find the value you need, modify C_value.txt and L_value.txt files according to capacitors and inductors available to you. Restart the software with a valid modification.
     3. The black line inside the graphic area is the original antenna response without the matching network. The blue line is the response of the matched antenna.

        

  5. The software also supports tolerance analysis. Either Band I or II has to be selected before tolerance analysis can be done. The tolerance analysis shows the worst case that might happen.
     1. You can use pull‐down menus to adjust the component tolerance from 0 to 20%.
     2. The tolerance result is only shown in VSWR or RL plots.