The SpurFinder program provides graphical information on the location of all spurious products in a frequency conversion process. The designer enters a defined INPUT FREQUENCY range, a defined OUTPUT FREQUENCY range, and a fixed LO FREQUENCY. The location of all spurious products up to "M" X RF and "N" X LO harmonics are displayed graphically. This program is a much improved tool from the old "Radar Handbook" spur charts, which are generic, normalized charts (sorry, Mr. Skolnik). These generic, normalized charts don't let you see the actual input and output frequencies to determine where the spurious frequencies are located. Click here to view a generic spur chart from the "Radar Handbook".
The program can be used for either be mixer down conversion or up conversion processes. The program is very easy to use. The input parameters needed are:
Input parameters are entered directly on the screen. Press the RUN button and the program will plot the spurious frequency locations. Each Spurious Product (±M X RF) + (±N X LO) is represented by a different line on the graph. The X and Y axis show the actual input and output frequencies (not normalized). The plots can be printed, and actual spurious information can be saved to a text file if needed.
If the application is a down conversion the input frequency or the "X-axis" would be the RF Input Frequency range. The "Y-axis," or output frequency range would be the IF frequency. If the application is an up conversion, the X-axis would be the lower IF frequency, and the Y-axis would correspond to the output RF frequency.
All plots created by this program can be printed. Once these spurious frequencies are plotted, mixer information can be looked up or measured to determine the relative amplitude levels of these spurious signals for each order of LO and RF harmonic. Once the spurious amplitude levels are determined, the preselection filtering requirements at the input to the mixer and the post-selection filter requirements at the output of the mixer can be determined. Actual filter rejection points can then be established and filter design can proceed from there.
There are many uses for this tool. For higher RF and microwave frequencies, various conversion schemes (different combinations of LO and IF frequencies) can be evaluated to determine which conversion scheme provides the best or optimum spurious responses. This can reduce cost in the receiver by reducing the requirements for the filters on each side of the mixer.
You can select and view spurious products any order up to order 20R X 20L
3 Different Conversion Modes
Capability to Load and Save SpurFinder Scenarios
Continuous Run Capability
Transfer SpurFinder information to TunerHelper
The charts can be read as follows:
For a given chart an input frequency is applied somewhere within the input frequency range. At this frequency a vertical line is drawn from top to bottom of the spur chart. At every point where a spur line crosses this vertical line, the output frequency of the spurious signal can be read on the output frequency axis. Tuning can be simulated by looking at various output spurious lines as vertical lines are placed at different points across the input frequency range.
Download SpurFinder for a free trial version. This trial version has all features available to the user except for the following limitation:
The full version is available for purchase for $129.99 (US Dollars). Buy now to unlock all program features.Software Download Page
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