An XML data file representing the mixer's suppression of harmonic intermodulation products can be attached to the currently selected mixer. The file data is only utilized by the Spurious Report.
The measurements to construct an N by N suppression table over a statistically representative sampling can be extremely time-consuming and expensive. As a consequence, virtually no manufacturer provides such data, leaving the task to the engineer instead. Even if accurate data is available, a particular implementation may not agree with the corresponding analysis because higher-order products are sensitive to termination, frequency or power differences between the implementation and the mixer test setup. You cannot assume, for instance, that the data for a leaded package will have comparable suppression characteristics to an "equivalent" surface mount version.
Given these barriers, the prudent approach is to simply create tables that reflect worst-case scenarios. While a given mixer will provide varying degrees of suppression for all intermodulation products, it is a better design that strategically maximizes suppression through careful frequency planning and filter selection while pessimistically relying on the mixer's intermodulation characteristics.
As a convenience, numerous Mini-Circuit data files are supplied with SysCalc. It must be understood, however, that these data files suffer from the limitations described above, most notably small sampling. Furthermore, the data has aged somewhat (1996) leaving the possibility of error due to mixer design changes since the data was published. It is also not known whether the data reflects conservative performance or market-hype. Further investigation of the data with the vendor is highly advisable.
An example of the XML data file format used for mixers is shown below and is equivalent to data supplied by Mini-Circuits for its RMS-2 mixer. You can create your data files using Notepad (supplied with Windows) or with some other text editor. We suggest that you put the data file in a separate sub-directory under the Mixers directory. As shown, the structure allows for multiple data sets in the same file. You choose which data set you wish to use at the time you attach the file to a specific mixer..
<?xml version="1.0" ?>
<MixerData Vendor="Mini-Circuits" Model="RMS-2" Blocks="2">
<Block Id="1" Size="11" DC="1" Freq_Range="5-1000" LO_Level="7" RF_Level="-10" IF_Level="-17">
<Data>
<!-- LO Harmonic (Across), RF Harmonic (Down) -->
<Item>99 11 21 11 52 27 46 34 53 57 49 </Item>
<Item>21 0 28 13 46 28 44 38 43 46 46 </Item>
<Item>65 44 62 43 63 42 59 57 65 56 69 </Item>
<Item>62 64 62 57 60 52 65 62 71 58 66 </Item>
<Item>78 79 79 76 79 79 80 78 78 78 78 </Item>
<Item>78 79 78 78 79 76 79 78 80 76 78 </Item>
<Item>78 79 78 79 79 78 78 79 79 79 79 </Item>
<Item>80 79 77 78 79 76 79 75 78 79 80 </Item>
<Item>79 79 79 77 78 78 79 79 79 78 78 </Item>
<Item>78 79 79 79 78 78 78 80 79 79 78 </Item>
<Item>79 79 79 78 79 79 77 80 79 79 80 </Item>
</Data>
</Block>
<Block Id="2" Size="11" DC="1" Freq_Range="5-1000" LO_Level="7" RF_Level="0" IF_Level="-7">
<Data>
<!-- LO Harmonic (Across), RF Harmonic (Down) -->
<Item>99 20 33 23 57 39 58 64 70 57 65 </Item>
<Item>21 0 28 13 50 31 51 45 51 56 62 </Item>
<Item>47 37 48 37 62 41 57 56 78 58 88 </Item>
<Item>41 40 48 37 54 40 68 51 58 54 54 </Item>
<Item>65 58 56 56 58 50 62 49 63 64 69 </Item>
<Item>60 64 57 45 62 46 54 48 60 62 70 </Item>
<Item>77 77 75 69 71 67 64 84 66 65 70 </Item>
<Item>73 72 77 72 67 56 63 54 62 55 67 </Item>
<Item>84 85 85 86 84 82 69 67 77 67 75 </Item>
<Item>76 88 84 79 81 79 84 67 81 72 74 </Item>
<Item>87 86 88 89 88 87 87 83 74 76 74 </Item>
</Data>
</Block>
</MixerData>
The XML data shown above has been indented to show the hierarchal nature of the information. Various elements or keywords are shown in black. Each element is case sensitive and therefore must be typed as shown. Some of the elements have attributes which are colored in blue. Comments are enclosed in <!-- --> and are colored purple. Free form data is shown in red.
The MixerData element must occur only once in the file and has the following attributes:
| Vendor - | The vendor name. | |
| Model - | The mixer model. | |
| Blocks - | The number of blocks contained in the file. |
Each data file can contain an unlimited number of data blocks each representing a unique collection of data. The above file has two data blocks as delimited by the <Block></Block> elements. Each block must contain several attributes -
| Id - | A unique integer representing the data block. | |
| Size - | Specifies that there are Size rows and Size columns of data in the block | |
| DC - | 0 = DC data is not included in the file; 1 = DC data is included in the file. | |
| Freq_Range - | A description of the frequency range for which the data block is valid. Calculations are not affected by this attribute. | |
| LO_Level - | The LO drive at which the data block was measured. Calculations are not affected by this attribute. | |
| RF_Levell - | The RF level at which the data block was measured. Calculations are not affected by this attribute. | |
| IF_Level - | Resulting IF level for the above conditions. The difference between the RF and IF levels determine the insertion loss in either direction. The implied loss is displayed on the Parameters Page of the Component Properties dialog. |
Each block has Size Item elements each with Size entries separated by commas. Each entry represents the relative attenuation of the harmonic spur to the desired IF output. The horizontal axis represents the LO harmonic order while the vertical axis represents the RF harmonic order. If DC='1' then the first row and first column (0 X 0) represent the zero-th order or DC components. The 1 X 1 entry represents the 1st RF and 1st LO harmonics and, as such, has 0 as an entry (it is 0 dB down from itself). If DC='0' then the DC row and column are omitted, i.e., the 0 X 0 entry is the 1st RF and 1st LO harmonic. See Spurious Report for other applicable information.