Why is a multicoupler alias the RF switch matrix so important? Sagax Communications among the wide variety of signal intelligence and spectrum monitoring products also deals with such devices. For example the antenna splitter SDU-500. In this post you can read about the functions and importances of RF switch matrixes.
The challenge
Regarding RF signal distribution and selection technology we may encounter some problems to solve. However the real challenge is not to handle the low level siganal with enough sensitivity. Or handling high level signals with input attenuation. The real challenge is to do both of them. Thus one of the ultimate figure of merit of the RF system is the instantaneous dynamic range. Especially with wide frequency range and wide bandwidth RF signal distribution components.
Generally in the RF signal routing segment of the integrated radio system we found signal distributors and signal selectors. They often form a blocking or non-blocking RF switch matrix configuration. In receiver systems we usually found non-blocking matrixes, as we need to deliver the antenna signal to multiple receiver inputs. In test and measurement systems we may meet with blocking matrixes where one test instrument makes measurements on one port of the device under the test. All of them have to work in the widest frequency range of the integrated system. So they are especially sensitive disturbing large signals which may block the reception of weak signals.
RF switch matrix testing
For testing the instantaneous dynamic range of the RF devices we have already presented 3rd degree intermodulation measurements. One of the figure of merit could be that the distance of the largest signal can be delivered to the input of the system and 3rd order intermodulation components. This can be converted to the intercept points which is the theoretical junction of the level of the signal and distortion components. You can read more about intermodulation here:
Setting up an intermodulation measurement test sounds easy. However in real life the test equipments interact with each other. Before any actual test, first you have to be sure that the performance of the test system itself is better than the expected target performance of the system under the test. These intermodulation tests can be done in smaller bandwidth where the two test tone and their intermodulation components fall into the bandwidth of the device under test, for instance a narrow-band monitoring receiver. Or it can be done in wider frequency range as we did during our last receiver test:
Concluison:
Next time your are looking for signal routing components for your system look after the dyanamic range performance results! Like intermodulation test results or intercept point specifications.
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