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Click here to go to our H-tree antenna feed page
New for April 2019. An H-tree is a network of two-way in-phase power dividers (often reactive as opposed to Wilkinsons) that drives elements in an antenna aperture, as decribed on our H-tree page. On this page we describe a free spreadsheet, H_tree_antenna_feed_Rev_0.xlsx,that provides a convenient way to analyze antenna apertures. Go to our download area, it should be near the top, otherwise search (CTRL-F) on H-tree. Or just click the link below you lazy...
MW101 H-Tree Feed Network Spreadsheet
The text below started as a copy of the text that is in the spreadsheet under the "readme" tab.
Use this spreadsheet to calculate H-tree area (length and width), transmission line loss, antenna gain and directivity and more. The "RX gain" and "TX gain" functions are useful if you are if you are designing a BUC or LNB and want to know signal levels at element level versus at array level.
The blue fields are where you input data, unless you are brave enough to mess with the other calculations. Nothing is locked.
Start by entering descriptions and attenuations for the media you plan to use. Note that you will have to enter different attenuations for different frequencies, the spreadsheet does not attempt to scale attenuation with frequency. You can enter attenuation as a positive or negative number, we take the absolute value and add a minus sign so you can't screw this up.
For each stage you will need to use the pull-down menu to select the media you want.
Then enter your upper frequency, and the element spacing in wavelengths at that frequency. You can use different spacings in X and Y. The first split (nearest to the antenna element) is assumed to be in the X direction.
Then go down the sheet and select the media for each power divider. The spreadsheet will keep your data hidden as "Media 1", Media 2" etc., because the descriptions could get out of hand. Also, the LOOKUP function wants the table in alpha order, so we are forcing that...We included math down to a 2^14 elements. You might want to highlight the row where your design stops, or delet the rows below where your feed stops.
The media data we entered for microstrip, stripline and waveguide are bogus. Calculate your own attenuation constants and enter them in the table! Please use dB/mm.
You can change the frequency of the analysis, but you will have to change the media to the frequency-correct attenuation constants you entered using the pull down menus. The spreadsheet will calculate gain and directivity based on the frequency you enter.
Below is a plot that the spreadsheet provides... It shows the attenuiation of each split, and the cumulative attenuation. The example is not something you'd want to show at a design review, it has crazy loss!
Send questions/comments/suggested improvements to UE@microwaves101.com