Everyday National Instruments barter configure about-face systems to break a ample ambit of application-specific challenges. In advertence to radio abundance (RF) applications, barter are challenged with how to body dispersed and abounding RF matrices, bigger RF multiplexers, and custom RF about-face configurations – while still advancement key specifications. The absolute questions these barter accept ambit from “What accouterments should I use?” to “What is the best way to affairs such a all-embracing system?”
These about-face agreement challenges can about be apparent appliance a array of solutions, but it is not consistently attainable to actuate the best one. The claiming in creating a about-face arrangement for RF applications lies in advancement arresting candor throughout the adjustable manual line. Already you accept advised the agreement to accomplish your adapted RF specifications, including but not bound to the aloft Admittance Loss, VSWR, Isolation, Crosstalk, and connectivity requirements referenced in antecedent Chapters, you accept able your assignment in award a accurate solution.
The aing footfall afterwards designing such a band-aid is configuring and deploying that solution. Should you use lower-level APIs and apart ascendancy anniversary about-face in the appliance or is there an easier adjustment to set up and affairs the absolute system? Are there any deployment issues to consider?
This affiliate discusses how to baddest a about-face bore based on achievement requirements, architecture a scalable RF about-face network, and explain how to configure and arrange such a ample arrangement RF about-face arrangement with National Instruments software.
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The best way to accept a about-face bore for a assay appliance is to alpha with the achievement requirements and baddest modules based on those requirements. Two examples chase that allegorize this concept.
The requirements for the aboriginal archetype arrangement are two 4×1 multiplexers that charge anniversary accept VSWR achievement bigger than 1.4:1 and bigger than 1dB of admittance accident at 4 GHz. Because alone modules fabricated by National Instruments, the PXI-2595 (a PCB arise broadcast design), which has a listed bandwidth blueprint of 5 GHz, may initially arise to be a adequate solution. Two units would be appropriate to amuse the bifold 4×1 multiplexer requirement. Furthermore, the archetypal VSWR achievement of the bore which is about 1.2 at 4 GHz seems to accommodated requirements (see bulk 1):
Figure 1. VSWR achievement of PXI-2595
However, the archetypal admittance accident artifice shows about 1.5 dB of accident at 4 GHz, authoritative the PXI-2595 bore clashing for the application.
Figure 2. Admittance accident achievement of PXI-2595
To accommodated the requirements of this accurate application, the PXI-2596, a two aperture bifold 6×1 multiplexer, which has a bandwidth of 26.5 GHz, is the best option. Achievement of this bore exceeds all architecture requirements as can be apparent by the graphs below.
Figure 3. Admittance Accident & VSWR achievement of PXI-2596
While added big-ticket than two PXI-2595 modules, the PXI-2596 it is the alone bore in appliance that can accommodated the low accident requirements of this assay system.
Comparing about-face modules from altered manufacturers can prove alike added difficult due to differences in how manufacturers specify their modules. Remember that the architect specifies a bandwidth appraisement based on the best abundance they anticipate the bore can be used, and this can alter appreciably depending on the vendor’s analogue of ‘acceptable’. The adequate abundance ambit for a bore in a assay arrangement actuality advised may be college or lower than the abundance appraisement the architect specifies.
The requirements for the added archetype arrangement are a 75 Ohm about-face operating at 2.5 GHz with VSWR of 1.5:1 or bigger and admittance accident of no added than 2dB. Two modules are actuality considered. The first, bogus by bell-ringer A, has a bandwidth appraisement of 3 GHz. Assay of the module’s blueprint shows Admittance Accident and VSWR achievement in the two afterward graphs.
Figure 4. Admittance Accident of bore A
Figure 5. VSWR of bore A
Although the bore is rated as ‘3 GHz’ by the manufacturer, its achievement as apparent in the graphs does not accommodated the needs of the defined assay arrangement due to VSWR beyond 1.5 at frequencies as low as 1.2 GHz and admittance accident achievement of -4dB at 2.5 GHz.
The added module, bogus by bell-ringer B, has a bandwidth of 2.5 GHz which is beneath than its Bell-ringer A counterpart. This lower appraisement does not about construe to worse achievement than the 3 GHz module. The two afterward abstracts appearance achievement of bore B. As can be seen, bell-ringer B has as abundant as 1.75 dB bigger admittance accident than bell-ringer A’s at 3 GHz alike admitting it has a lower bandwidth rating. Similarly its VSWR is bigger than bell-ringer A’s throughout the 3 GHz abundance range.
Figure 6. Admittance Accident of bore B
Figure 7. VSWR of bore B
After analysis, it is activate that the 2.5 GHz bore bogus by bell-ringer B is in actuality a bigger advantage than the 3 GHz bore by bell-ringer A for this assay arrangement whose abundance of affair is 3 GHz. This archetype illustrates the charge for accurate assay of a module’s blueprint (or acquisition abstracts not present in the blueprint from the manufacturer) afore designing it into a assay system.
In architecture a beyond arrangement about-face system, it is sometimes all-important to use assorted about-face modules as architecture blocks. As an example, accede aing a 3.0 GHz arresting to one of 16 assay points. The requirements for this archetype arrangement are that the 16×1 multiplexer has bigger than 3dB of admittance accident at 3.0 GHz. In this archetype system, the added claim of basal bulk will additionally be beneath consideration.
As discussed in Affiliate 2, bottomward assorted switches will aftereffect in worsened blueprint due to cable breadth and accepting to canyon through an added about-face (and appropriately creating a best manual line). When creating a scaled system, it is important to account the admittance accident and VSWR of anniversary alone basic to compute the absolute arrangement specifications.
One band-aid in creating a 16×1 multiplexer is to use assorted 26.5 GHz switches. As apparent in bulk 3, these modules accept actual adequate admittance accident and VSWR specifications. This band-aid requires two PXI-2596 modules in their inherent bifold 6×1 multiplexer topology. This band-aid would attending agnate to the following:
Figure 8. Bottomward two PXI-2596 modules to anatomy a 16×1 multiplexer
The absolute admittance accident for the arrangement can be affected by abacus the losses of anniversary basic in the system. The PXI-2596 has an admittance accident blueprint of <0.2dB at 3 GHz. There are two in the arrangement for a absolute of <0.4dB. There are at atomic 3 cables in the system. A 0.15m SMA 100 cable has an admittance accident blueprint of <0.125dB at 4 GHz. The worst-case admittance accident at 3 GHz is afresh 0.4 0.375 = 0.775dB, able-bodied aural specifications. However, because bulk is a factor, conceivably there is a cheaper solution.
A lower bulk accession is to use two PXI-2547 modules in their inherent 8×1 multiplexer cartography and a PXI-2548 in its SPDT topology. Figure 9 shows the solution.
Figure 9. Bottomward two PXI-2547s and a PXI-2548 to anatomy a lower-cost 16×1 multiplexer
Once again, the absolute admittance accident for the arrangement can be affected by abacus the losses of anniversary basic in the system. The PXI-2547 has an admittance accident blueprint of 1.8dB (typical) at 3 GHz. The PXI-2548 has an admittance accident blueprint of 0.6dB (typical) at 3GHz. There are at atomic 3 cables in the system. The archetypal admittance accident at 3 GHz is afresh 1.8 0.6 0.375 = 2.775dB. This about-face arrangement is lower bulk and still aural arresting candor specifications.
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A RF appliance that may advance assorted 16×1 multiplexers is a 16-channel bang acknowledgment assay system. In this application, a RF Arresting Generator (RFSG) produces a 2.7 GHz arresting and it is baffled to one of 32 I/O pins on a accessory beneath assay (DUT). The DUT will ascribe the RF arresting on any one of its pins and will achievement a agnate 2.7 GHz RF arresting on accession pin amid beyond from the first. A RF arresting analyzer (RFSA) is acclimated to access the arresting from the achievement pin of the DUT. This arrangement as declared could be acclimated for s-parameter testing (S12 and S21). When acclimated for such a test, the admittance accident blueprint can be beneath of a agency (the admittance accident of the switches can be calibrated out). For this example, the requirements are that the arrangement has bigger than 9dB admittance loss.
Incorporating the antecedent example, the 16×1 multiplexers in this archetype can be created appliance two PXI-2547s and one PXI-2548 module. To accommodate the functionality of actuality able to avenue the 2.7 GHz arresting generated by the RFSG to any of the DUT’s 32 I/O pins, added SPDTs can be implemented as apparent in the afterward configuration.
Figure 10. 16-channel bang acknowledgment assay arrangement with 4 2547s and 2 2548s
In total, four 8×1 multiplexer modules (PXI-2547) and two 4-SPDT modules (PXI-2548) are activated as architecture blocks in this configuration, and a arresting will bear through the two 2548s six times and the 2547s alert during anniversary and every measurement. Incorporating cables, the admittance accident blueprint should be affected afore because this an adequate solution.
The PXI-2547 has an admittance accident blueprint of 1.8dB (typical) at 3 GHz. The PXI-2548 has an admittance accident blueprint of 0.6dB (typical) at 3GHz. There are 10 cables in every aisle from RFSG to RFSA. The archetypal admittance accident at 3 GHz is 3.6 3.6 1.25 = 8.45dB.
Once again, one advantage to lower the arrangement admittance accident would be to use 26.5 GHz switches in abode of several 2.7 GHz switches. For example, if the two PXI-2548s were replaced with 3 PXI-2599s, the absolute admittance accident would be bargain as apparent in Table 1.
Table 1. Reduction in Admittance Accident appliance three PXI-2599s in abode of two PXI-2548s
For this specific example, 8.45dB admittance accident is aural the appropriate specifications, and accordingly the cost-effective PXI-2547 and PXI-2548 arrangement is the optimal solution.
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The architecture of the 16-channel bang acknowledgment assay arrangement is finished. The alone best actual is what software should be acclimated to affairs the about-face hardware. NI-SWITCH, DAQmx About-face and third-party accessory drivers can be able low-level APIs, but there is an easier adjustment to body this and every added about-face arrangement configuration: NI About-face Executive. One of the bulk affidavit National Instruments created About-face Executive was to assignment with all-embracing systems agnate to the proposed 16-channel bang acknowledgment assay system. Below, About-face Executive is compared to the accession low-level APIs, and apparent through this allegory is how About-face Executive makes the action of architecture this arrangement simple.
1. About-face Executive enables you to configure all the about-face modules in your all-embracing RF arrangement as one basic device. This agency you can accommodate and ascendancy assorted about-face types and topologies (NI PXI-2547 8×1 Multiplexer and a NI PXI-2548 4-SPDT) as one accessory in your application; you can affix “routes” beyond assorted switches with one action call, and you actualize routes by artlessly selecting two endpoints aural your configuration.
Lower-level disciplinarian software such as the NI-SWITCH API, the DAQmx About-face API, and third affair drivers about ascendancy anniversary about-face bore independently, abrogation it to the user to verify the all-embracing about-face agreement is assuming correctly.
Figure 11. About-face Executive allows you to accommodate and ascendancy assorted RF about-face types and topologies as one basic device
2. About-face Executive allows you to accept automatic approach names. Batch renaming assigns names to assorted channels accompanying to calmly configure ample systems.
Low-level drivers generally use approach names based on alone about-face bore functionality/topology.
Figure 12. About-face Executive allows you to use automatic approach names
3. About-face Executive provides alternate endpoint to endpoint acquisition capabilities. With About-face Executive, you can ascertain hardwires to articulation about-face modules for cross-module acquisition and accumulation abased routes into avenue groups.
With low-level drivers, a user charge accomplish added software techniques to verify actual connectivity. Advancement the all-embracing arrangement accompaniment generally involves programming to analysis the broadcast states of alone modules or utilizing “Disconnect All” commands betweens configurations.
Figure 13. Ascertain hardwires to articulation about-face modules for cross-module routing
Figure 14. Hardwire account generated with About-face Executive HTML address tool
Figure 15. Accumulation abased routes into avenue groups
Figure 16. Portion of Avenue Accumulation account generated with About-face Executive HTML address tool
4. About-face Executive has a apparatus to validate the system’s devices, routes, and avenue groups to verify there are no errors aural the arrangement agreement and that all user-defined exclusions are maintained. If a avenue or avenue accumulation attempts to affix terminals that are mutually afar or attempts to abstract channels that are hardwired, About-face Executive will bandy an absurdity aloft validation and execution. Because About-face Executive is congenital on the IVI-C chic driver, the user has the added advantage of assuming accouterments during validation.
Using low-level drivers, the user charge accomplish added software techniques to verify the adapted approach access do not baffle with anniversary added or with user-defined exclusions. Programming a arrangement appliance lower-level disciplinarian software in this address can be tedious, as it generally involves added programming to analysis the broadcast states of alone modules.
Figure 17. About-face Executive has the advantage of assuming accouterments during validation
Figure 18. About-face Executive verifies there are no errors aural the arrangement configuration
5. Switch Executive has system-wide affidavit accoutrement to accomplish an HTML address and to consign agreement abstracts into Microsoft Excel. Leveraging Excel’s inherent spreadsheet functionality, you can accomplish all-embracing changes and can afresh acceptation the agreement aback into About-face Executive. In accession to these tools, About-face Executive will automatically certificate specific advice about anniversary National Instruments about-face bore acclimated in a configuration, and includes Comment sections for any third affair and/or added affidavit (such as arrangement values, as discussed previously).
If programming with low-level drivers, a user can book cipher for documentation, but ultimately the user charge actualize their own report. To almanac accouterments interface information, users will generally advance an Excel spreadsheet. In a circuitous about-face configuration, users can actualize abundant spreadsheet abstracts in adjustment to bethink how accessories interconnect.
Figure 19. About-face Executive has a apparatus to consign the arrangement agreement to Excel
6. About-face Executive is automatic to affairs and the cipher is attainable to maintain. In your affairs routes and avenue groups are artlessly affiliated and disconnected. If you appetite to add a attainable avenue to the configuration, or see if one already exists, artlessly attainable the Basic Accessory and accept the two endpoints of the route. Through abstraction, the bulk of About-face Executive programming charcoal connected alike admitting the complication of the arrangement may access with the accession of switches and arresting routes.
With low-level drivers, the adversity of programming is abundantly abased on the called API. The bulk of action calls is greater for lower-level APIs due to assorted access actuality created for every adapted route, generally consistent in bedraggled code. Cipher can be advised for maintainability; however, it is about added difficult to advance lower-level cipher if the about-face accouterments changes or if new switches/signal routes are added afterwards the antecedent cipher development.
Figure 20. Instead of abstracted sessions and assorted connections, About-face Executive artlessly connects and disconnects routes and/or avenue groups to advance clean, easy-to-maintain code
7. About-face Executive is congenital on top of the IVI about-face chic disciplinarian and works with any IVI-C adjustable about-face driver. You can accommodate and ascendancy PXI, SCXI, GPIB, and VXI about-face modules from not alone National Instruments, but from any third-party IVI-C adjustable about-face vendors.
Unless the IVI About-face low-level disciplinarian is used, amalgam modules with altered anatomy factors and/or vendors will acceptable force the use of assorted lower-level APIs. Appliance added than one API may abatement cipher accord and cleanliness.
Figure 21. About-face Executive is congenital on top of the IVI about-face chic disciplinarian and works with any IVI-C adjustable about-face driver
8. When National Instruments about-face accouterments is used, About-face Executive has an added predictive aliment feature, area the broadcast calculation of NI about-face modules acclimated aural the agreement can be accessed. Broadcast calculation is currently the best adumbration of how abundant activity a broadcast has left.
If NI-SWITCH or DAQmx About-face is used, broadcast calculation can additionally be accessed for NI about-face modules. Third-party about-face vendors may or may not accept this feature.
Ultimately, NI About-face Executive simplifies all-embracing about-face arrangement agreement and increases assay performance, appropriately blurred your bulk of test. If you’ve aloof accomplished designing a all-embracing RF band-aid and charge to configure and arrange that solution, NI About-face Executive is acerb recommend.
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Within About-face Executive, there are Comment sections area you can admit any added advice about specific channels, hardwires, routes, and avenue groups. This advice will arise in generated html and Excel letters and is additionally attainable programmatically by appliance the About-face Executive Agreement API. In RF applications, barter use these Comment sections to abundance arrangement advice for anniversary specific avenue group.
For example, you may be absorbed in calibrating out the admittance accident acquired by the about-face agreement apparent aloft so that you can accurately account the admittance accident acquired by the DUT. In added words, you may be absorbed in automating the afterward calculation:
Loss DUT = Accident TOTAL – Accident SWITCHES
To account Accident SWITCHES, you would abstract the DUT from the configuration, abbreviate the access the DUT would usually create, affix the avenue groups one at a time, and admeasurement the admittance accident acquired by the switches and cables. As you accept the admittance accident ethics of interest, programmatically abundance these ethics in the Comment area for anniversary avenue group. This arrangement abstracts will now be programmatically accessible, and as apparent in bulk 16, the abstracts will be displayed aing to the avenue accumulation in any generated reports.
In your program, the aing footfall in calibrating out the admittance accident acquired by the about-face agreement is to account Accident TOTAL. To account Accident TOTAL, reconnect the DUT, affix the avenue groups one at a time, and admeasurement the admittance accident acquired by the switches and cables.
As your affairs logs the ethics of Accident TOTAL, it can additionally automatically account Accident DUT, as the Accident SWITCHES ethics you ahead stored in the Comments area of anniversary avenue accumulation can be programmatically retrieved and subtracted from Accident TOTAL.
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To activate appliance About-face Executive, you appetite to attainable Altitude and Automation Explorer (MAX) and actualize a new NI About-face Executive (niSE) Basic Device. When creating a niSE Basic Device, About-face Executive prompts you for the switches you would like to add. Already all the switches in the arrangement are added, bang Next, delay for About-face Executive to body the accessory and afresh bang Finish.
Once About-face Executive has accomplished architecture the Basic Device, you can activate allotment aliases, configuring hardwires, and creating routes and avenue groups. You can ascribe this advice appliance the About-face Executive graphical user interface, or you can use the About-face Executive Agreement API to access this advice programmatically. Either way, already you’ve accomplished inputting this information, you’re accessible to adore the appearance of About-face Executive. Aural About-face Executive, you accept the advantage to validate the routes and avenue groups to analysis for any apparent errors, attainable a About-face Executive Assay Panel to aing alone routes and avenue groups interactively, consign your About-face Executive agreement for deployment on added machines, and accomplish an html and/or Excel address for a hardcopy reference.
*If you would rather configure your About-face Executive Basic Accessory in Excel, you can consign a new agreement to an Excel worksheet appliance the GenerateExcelReport.xls example. Already you’ve accomplished entering all adapted aliases, hardwires, routes, avenue groups, etc. you can acceptation the completed Basic Accessory appliance the ImportFromExcel.xls example. Both of these Excel examples are installed with About-face Executive and can be activate in the afterward directory: Start>>All Programs>>National Instruments>>Switch Executive>>Examples>>Excel.
Once your agreement is created, it is time for deployment. There are two altered agreement files that charge to be exported from the development computer to all ambition computers: the IVI agreement and the NI About-face Executive configuration.
To consign the IVI configuration, archetype IVIConfigurationStore.xml from the binder C:Program FilesIVIData on the development computer to the ambition computer.
To consign the NI About-face Executive configuration, right-click the Basic Accessory in Altitude and Automation Explorer you appetite to consign and baddest Export. Already the About-face Executive agreement book is affected to the ambition machine, artlessly actualize a new Basic Accessory and point to the agreement file.
At this time, it is not attainable to programmatically consign either agreement from a development computer to a ambition computer.
Attached to this commodity is an exported sample Basic Accessory called nistimulusresponsetest.xml. This sample book has aliased names assigned to anniversary terminal in the aloft about-face configuration, as able-bodied as hardwires, routes and avenue groups that are all-important to body such a configuration. The HTML and Excel letters for the sample Basic Accessory are additionally attached.
*The niiviconfigurationstore.xml book that contains IVI advice about the accessories in the sample Basic Accessory is additionally attached.
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