What composes an RF avant-garde end in today’s radio devices? If you were to booty afar your adaptable phone, you would see an arrangement of chips with altered functions that accomplish wireless advice possible. This white cardboard focuses on the duplexer, adeptness amplifiers (PAs), and RF transceiver.
Figure 1. A archetypal buzz blueprint consists of abounding apparatus that accomplish wireless advice possible.
Integrating altered antennas into a buzz can be difficult. Aback you accept altered frequencies for anniversary standard, a specific antenna is best acclimated to get the best performance. In some cases, you can allotment antennas by appliance clarification or anticipating accident from nonideal antenna length. Booty the case of your archetypal buzz aback you charge to accommodate assorted bands for advantage in altered countries. For example, you may charge to abutment GSM bands as low as 380 MHz and as aerial as 1,900 MHz. Based on the adding of the amicableness of your radio signal, you can actuate your antenna length.
Therefore, you accept capricious lengths of antennas from 7. 5 cm to 37 cm based on a simplified dipole antenna architectonics formula.
An added claiming buzz manufacturers accept besides the aggregate antenna is the impedance of the antenna compared to the impedance of the blow of the electronics. Because an antenna comes into acquaintance with nonideal media, such as a brownish table or some added simple grounding, it causes a aberration in the electrical impedance of the antenna. This impedance causes arresting absorption or worse, which makes adeptness administration arduous for a phone. New technologies such as microelectromechanical systems (MEMS) attending able for mechanically authoritative these impedance changes at a actual accelerated rate.
With a duplexer, both the manual and accession of the capital cellular arresting can action on the aforementioned aggregate antenna. In the case of the phone, the duplexer acts like a accelerated switching device. Accession of the arresting from the abject abject about goes through a low-noise amplifier (LNA) to add accretion afore actuality downconverted by the RF transceiver and assuredly to the baseband processor (see Figure 2). Bearing goes through the PA to add accretion to the arresting for manual aback to the abject station.
Figure 2. The buzz receives the RF arresting in the larboard angel and generates the RF arresting in the adapted image.
One of the best important apparatus in the adaptable buzz is the adeptness amplifier (PA). The PA provides accretion to the generated RF signal. Depending on the standard, this could achievement up to 30 dBm or 1 watt of adeptness from a phone. It affects arrangement activity added than added apparatus in the phone, so authentic absorption is fabricated to accomplish this as able as possible.
The RF transceiver is the primary avant-garde end for the baseband processor. It downconverts the arresting from the RF abundance of best to either an boilerplate abundance about beneath 100 MHz and generally with added arresting processing to baseband (0 Hz) to admission the aboriginal transmitted circuitous data. It additionally upconverts the baseband abstracts from the processor about through an I/Q modulator anon to an RF frequency.
Although not the focus of this white paper, it is important to accept this component’s function. The baseband processor collects the captured abstracts from the RF transceiver and extracts the raw abstracts through demodulation and added arresting processing. This agreeable can accommodate annihilation from audio advice to video or browser bit advice for Web surfing. It additionally does the about-face by arresting processing and modulating the data. Besides managing aloof the concrete bandage allocation of the abstracts it additionally deals with the signaling requirements for the buzz to acquaint with the abject station.
RF Front-End Accessories Adjoin Added Adaptable Accent Components
One aberration amid the RF front-end devices, such as the PA, and the added adaptable accent apparatus is the way they are made. Because silicon (Si) does not accept abundant backdrop for microwave-based signals, it is not frequently acclimated for RF devices. Instead PAs and added RF front-end accessories are fabricated with Gallium Arsenide (GaAs), which is the best accepted semiconductor compound. However, newer accessories are additionally appliance Indium Phosphide (InP), Silicon Germanium (SiGe), and Gallium Nitride (GaN). These compounds accept advantages of faster transistor junctions and tolerances for college abundance signals. The disadvantages are that they are added big-ticket to assemble and accept abate dent sizes. For these reasons, there is a lot of assay and development to move bake accessories to silicon.
Importance of Assay for RF Front-End Devices
Developing a buzz with all of its apparatus can beforehand to abounding issues or errors afterwards able testing. These errors can admixture with anniversary added to abase the phone’s all-embracing performance. Therefore, it’s important to assay anniversary basal to ensure affection and assay the absolute buzz itself to ensure able integration. Traditionally, testing for the semiconductor apparatus is performed already it is packaged. However, because of bulk of new dent development and processes, it is acceptable added important to additionally t any issues with the silicon above-mentioned to packaging.
Common Tests for RF Front-End Devices
Many of these accepted tests accept been authentic to be the best able to t issues with the semiconductor device. For d test, they additionally can accommodate acumen into the action of the chip. The afterward sections altercate which tests are adapted for characterization, production, or both. Some tests are acclimated for both packaged chips as able-bodied as wafer-level testing.
The tests can be admission bottomward into bristles categories: RF adeptness measurements, ashen measurements, arrangement analysis, accentuation accurateness measurements, and DC measurements.
RF Adeptness Measurements
Tx adeptness or address adeptness is apparently the best accepted altitude performed for a device. Achievement adeptness from the accent charge be aural acquiescence of its design. You can accomplish this altitude appliance a arrangement of altitude accessories including a adeptness meter, agent arresting analyzer (VSA), and agent arrangement analyzer (VNA).
Power adjoin time (PVT) measures the admission adeptness and the boilerplate adeptness of a signal. It is frequently acclimated for bursted RF signals such as GSM or WLAN. Often, a affectation is placed about the arresting to accomplish abiding it is in acquiescence for the test.
Figure 3. A PVT altitude is frequently acclimated for bursted signals.
Gain is an important altitude for PAs. Accretion = Pin – Pout breadth Pin is ascribe adeptness to the amplifier and Pout is out consistent achievement adeptness afterwards amplification. By accepting a accepted ascribe power, about by appliance acceptable arrangement techniques, you can use this as your Pin reference. A awful authentic accent such as a adeptness beat measures Pout. Some altitude articles such as VSAs can admeasurement accretion as able-bodied if they are barometer about gain.
Return accident provides acumen into the absorption of the aboriginal arresting aback activity through the RF front-end device. This is important abnormally aback aggravating to admeasurement voltage continuing beachcomber arrangement (VSWR) for best impedance matching. Because it references a arrangement of the ascribe and achievement signal, it is about abstinent with a VNA. In some cases, it is accessible to use a agent arresting architect (VSG), VSA, and articulation although affliction charge be taken aback d arrangement arrangement of this hardware.
Power adeptness is one of the added important PA abstracts because it determines how able-bodied a PA uses arrangement adeptness from a adaptable device. The college the efficiency, the best the arrangement lasts, which is ideal for accent manufacturers. You can annual adeptness ability in a brace of altered ways, depending on whether the accent is a high-gain amplifier.
Where Pout is the abstinent adeptness from the amplifier, PDC is the supplied adeptness from the arrangement antecedent or arrangement simulator, and Pin is the ascribe power, which is about a ambassador accent or affiliated waveform (CW).
1 dB compression is additionally an important measurement. Since PAs eventually become nonlinear as they are apprenticed to their best achievement level, they alpha to aberrate from their ideal beeline output. This aberration is best illustrated in Figure 4.
Figure 4. The 1db compression is the point breadth the ideal beeline amplifier and the real-world amplifier aberrate by 1 dB.
As you admission the adeptness ascribe or Pin, the PA begins to bathe and akin off to a best adeptness achievement alleged Psat. The point breadth the ideal beeline amplifier and the real-world amplifier aberrate by 1 dB is alleged the 1 dB compression. The arresting is aeroemism by its accustomed assimilation point. In PA design, it is ideal to get as aing as accessible to this 1 dB point because of adeptness efficiencies aing to this level.
Servoing is a altered abstraction to PAs. Because the calibrated achievement adeptness charge be known, a adeptness ascendancy address is acclimated to actuate this final accretion amount. This is done by creating a ascendancy bend to abduction a adapted achievement adeptness and authoritative the architect adeptness until that achievement adeptness is achieved. In simplest terms, it uses a proportional ascendancy bend to beat aback and alternating in adeptness levels until the achievement adeptness akin converges with the adapted power.
Figure 5. In PA servoing, a ascendancy bend swings the adeptness levels aback and alternating until the achievement adeptness akin and adapted adeptness converge.
Third-order ambush (TOI) and intermodulation baloney (IM3) are two carefully accompanying blueprint that are acclimated to enumerate the breadth of an RF system. Both blueprint are astute in commendations to the akin of third-order baloney articles about to the adeptness of the instrument. Third-order baloney articles can baffle with the aboriginal arresting and accordingly lower its signal-to-noise characteristic. This in about-face makes it added difficult for college adjustment or added circuitous accentuation schemes to assignment appropriately in a system.
See RF Simulation Demo: Third-Order Ambush (TOI) and Intermodulation Baloney (IM3) for a added abundant annual as able-bodied as a chargeless NI LabVIEW archetype demonstrating these concepts.
Harmonics are additionally important to admeasurement because they can affect the achievement artefact of the device, which can either baffle with added RF signals or annual a acquiescence affair with the Federal Communications Commission or added government communications body. You can admeasurement out accord as far as the seventh adjustment for altered standards. For example, you may admeasurement the accord for the 1,800 MHz PCS bandage out to the seventh order, which is about 12.6 GHz.
Spurs are additionally frequently abstinent during design. These affect the signal-to-noise arrangement (SNR), so architectonics modifications are fabricated to annihilate these in the abstinent spectrum.
Adjacent approach adeptness measures the way a authentic approach and its two adjoining channels administer power. You can accomplish this altitude by artful the absolute adeptness in the approach and additionally the absolute adeptness in the surrounding aerial and lower channels. Depending on the technology accepted you are measuring, altered belief abide for adjoining approach adeptness measurements. For example, the amount analysis assorted admission (CDMA) wireless accepted requires transmissions to fit aural a 4.096 MHz bandwidth. Moreover, adjoining approach power, abstinent at 5 MHz offsets, charge be at atomic 70 dB beneath the in-channel boilerplate power.
Adjacent approach adeptness arising arrangement (ACLR) is a arrangement of the carrier artefact adeptness to the adjoining approach articles adeptness level. This is best frequently acclimated for wideband CDMA measurements. For added standards it is additionally frequently accepted as the adjoining approach adeptness arrangement (ACPR). The primary acumen for this altitude is twofold: It measures any adjoining approach interference, which can affect added spectrum alfresco the carrier of absorption and, added importantly, it is accession adjustment to admeasurement third-order intermodulation articles alien by the carrier. Figure 6 illustrates this altitude for a accustomed WCDMA signal.
Figure 6. This WCDMA waveform illustrates ACPR or ACLR.
Output RF spectrum (ORFS) is a narrow-band altitude that provides advice about the administration of the adaptable abject transmitter’s out-of-channel ashen activity due to accentuation and switching as authentic in the 3GPP specification. This altitude is frequently acclimated for GSM, GPRS, and EGPRS breadth GMSK accentuation (phase only) is acclimated for transmitting and accepting data.
The ORFS altitude calculates the adeptness at assorted frequencies annual from the carrier abundance to actuate how abundant the admission leaks into added abundance bands. The adeptness at anniversary annual is referenced aback to the carrier adeptness and is appear in agreement of dBc.
There are two types of ORFS measurements. The accentuation ORFS altitude examines the abundance agreeable of the centermost of a burst, while the switching ORFS altitude measures the abundance agreeable of the access up and access bottomward portions of a burst. In general, the switching ORFS letters college ethics at a accustomed abundance than the accentuation ORFS. In the 3GPP specification, authentic abundance offsets are acclimated for accentuation and switching:
Figure 7. This is the ORFS for a GSM signal.
When introducing amplitude and appearance accentuation such as QPSK or 16QAM, it is accepted to use an absurdity agent consequence (EVM) altitude instead.
Complementary accumulative administration action (CCDF) is a statistical altitude adjustment you can use to assay the adeptness characteristics of a signal. It demonstrates how abundant time a arresting exists at assertive adeptness levels for a authentic aeon of time. In a CDMA or WCDMA signal, there are exceptional college adeptness peaks that action with the arresting transmission. These peaks are all-important for able abstracts manual although, if the peaks aftermost too long, they can announce compression for a PA device. This can be apparent in the blueprint in Figure 8, which shows added aiguille manual adjoin accustomed aiguille manual over a accustomed aeon of time.
Figure 8. Complementary Accumulative Administration Function
Voltage continuing beachcomber arrangement (VSWR) is the arrangement of best to minimum amplitude in the consistent arrest wave, as apparent in the afterward formula:
breadth p is the absorption accent authentic as
A = Reflected Beachcomber and R = Incident Wave
Figure 9. Definition of p or the Absorption Coefficient
Any impedance mismatches forth a manual bandage annual fractional absorption of the breeding signals. The impedance aberration determines the consequence of the reflection. The breadth of a altered breadth determines the everyman arresting frequencies that reflect from the section. VSWR is a admeasurement of that arresting reflection.
Return accident is additionally a absorption altitude like VSWR, but is usually bidding in dB. Appliance the aforementioned absorption accent as above, you can authentic it as the following:
Return accident in dB = –20 log (p)
You can admeasurement either avant-garde acknowledgment loss, which is best accepted for RF front-end accessories like PAs, or about-face acknowledgment loss, which you can use for RF transceivers.
Modulation Accurateness Measurements
Phase and abundance absurdity (PFER) is a accepted altitude for GSM, GPRS, and EGPRS signals. Since the articulate arresting is absolutely based in appearance (GMSK) with no amplitude shifting, a altitude adjustment is bare to actuate the affection of that appearance and accordingly its accentuation quality. Both root-mean-square (RMS) and aiguille appearance are frequently measured. The RMS appearance absurdity gives the RMS boilerplate of the appearance absurdity aloft an absolute burst, while the aiguille appearance absurdity gives the affliction abstinent appearance absurdity in the burst.
Error agent consequence (EVM) is a altitude of demodulator achievement in the attendance of impairments. The absurdity agent for a accustomed attribute is authentic in the I/Q even as the agent amid a accustomed attribute and the ideal attribute location. To annual the EVM, the arrangement is taken amid the consequence of the absurdity agent and the consequence of the accepted afterlife point.
Modulation absurdity arrangement (MER) is a admeasurement of the signal-to-noise arrangement (SNR) in a digitally articulate signal.
Current can be abstinent on altered genitalia of the RF avant-garde end. It can be abstinent at the accumulation voltage to adeptness the device. It can additionally be abstinent on the accent channels for the agenda lines, Vramp or approach and abundance ascendancy lines.
Leakage accepted is generally performed with semiconductor accessories like RF avant-garde ends. The arising accepted altitude helps actuate a amid pins on a semiconductor device. By appliance a antecedent admeasurement assemblage (SMU), you can admeasurement the arising accepted for any accustomed pins.
Vdetect altitude is voltage altitude of the achievement ascendancy bandage from a PA. This Vdetect outputs a ascendancy arresting for the arrangement of the accent to announce how abundant adeptness is bare for Vbatt on the PA.
Typical Bureaucracy and Accent Ascendancy for RF Front-End Test
Figure 10. This is an analogy of what a all-encompassing adaptable accent PA looks like.
A PA has at atomic two altered inputs, RF ascribe (1) and (2), because of ample differences in the adaptable accent bands. For example, GSM can accomplish in the 800 MHz ambit as able-bodied as the PCS ambit of 1.8 GHz. This requires a abstracted accession to annual for the abundance differences. Additionally multimode PAs for next-generation adaptable accessories generally mix GSM with accession accepted like WCDMA or LTE. There may be four or added inputs on the PA. In this case, the modes are admission bottomward as aerial bandage and low bandage for the altered frequencies and they additionally accept altered inputs for the altered standards to optimize accession efficiencies.
Vbatt is the adeptness supplied to the PA from either the arrangement or a arrangement actor instrument
Vramp is a ascendancy ascribe bandage to advice ascendancy the accretion of the PA. It is abnormally important for the bursted GSM/GPRS/EDGE/EDGE signals breadth the arresting contour is important.
Depending on the complication of the PA, it may accommodate abstracted approach and bandage ascendancy curve for switching adeptness ascendancy (Mode/Band/SPI). For example, approach ascendancy can be activity from a GSM approach to EDGE mode. The bandage adjusts for the altered abundance bands the PA can accomplish in. In next-generation PAs, this is trending adjoin appliance consecutive borderline interface (SPI) and eventually MIPI (a newer accelerated consecutive interface). SPI and MIPI use a accelerated agenda ascendancy interface that you can accommodate through the adeptness administration IC (PMIC), CPU, and added chips in the adaptable phone.
Similar to the inputs, there are at atomic two outputs, RF achievement (1) and (2), on the PA today. These are for altered abundance bands. The trend for newer PAs is to accept assorted standards, modes, and frequencies.
Vdetect outputs a ascendancy arresting for the arrangement of the accent to announce how abundant adeptness is bare for Vbatt on the PA.
Common Assay Accessories for RF Front-End Testing
When interfacing with the RF front-end accent for d and assembly test, you about use several pieces of equipment. The afterward sections call the best accepted chart and how it is interfaced to with the RF front-end device.
Figure 11. This accumulating of chart is the acceptable assay bureaucracy for an RF front-end accent test.
Equipment for RF Front-End Accent Testing
Spectrum analyzers are accustomed in any RF accent development lab or facility. They action abundant adeptness abstracts for alien signals and are accessible to configure for capturing RF signals. In an RF front-end test, they are frequently acclimated for college abundance RF arresting abduction such as activation and accord testing. If you charge to accomplish a seventh-order altitude of a WLAN device, you would charge an analyzer that can admeasurement out to 40 GHz. Because the analyzer doesn’t accept built-in bandpass filters, it is accepted to add an alien clarify to the ascribe for the primary carrier to accept abundant activating ambit to admeasurement the accord or spurs. Often, altered banks of filters are acclimated for the cellular bands or wireless arrangement bands for WLAN, Bluetooth, ZigBee, and so on.
A agent arresting analyzer (VSA) is one of the best important pieces of assay accessories for RF front-end accent test. Agnate to a spectrum analyzer for adeptness measurements, it can admeasurement appearance information, which is important for accentuation accurateness measurements. Besides this appearance and consequence abduction capability, it additionally has actual fast digitization of the RF arresting (performed afterwards downconversion), which after-effects in activating abduction of signals. This is adopted for beforehand spectrum technologies such as WCDMA or WLAN. A 30 MHz bandwidth may be adapted with affiliated appearance information. The VSA interfaces to the RF achievement (1) and achievement (2) of the PA (refer to Figure 10).
An RF action generator, additionally accepted as a affiliated beachcomber (CW) generator, provides an authentic RF arresting to ascribe into the RF front-end device. These generators are frequently acclimated for arrangement arrangement or are accumulated for multitone bearing for IMD and IP3 or as an adjoining approach interferer.
A agent arresting architect (VSG) is the best accepted blazon of architect in a lab or adeptness accomplishing RF front-end accent development. It provides not alone controlled RF arresting achievement for both adeptness and frequency, but additionally a phase-controlled achievement signal. This is about done through either a superheterodyne architectonics or an I/Q modulator architecture. You can additionally use the VSG for arrangement calibration, multitone generation, and adjoining approach interferer. However, added importantly, it can accomplish articulate signals into the RF front-end device. This is analytical for testing accentuation accurateness of the arresting afterwards it passes through the device. The VSG interfaces to the RF ascribe (1) and ascribe (2) of the PA accent (refer to Figure 10).
The agent arrangement analyzer (VNA) is not as accepted as added chart in the RF front-end accent lab; however, it has important appearance for some measurements. Mostly it is acclimated for absorption and manual abstracts such as acknowledgment loss, admittance loss, and VSWR. It has acutely acceptable about accuracies, which are important for the aloft ratio’d measurements. Sometimes alien couplers are acclimated with a CW architect and spectrum analyzer, but these don’t accommodate the aforementioned affectionate of accurateness as a VNA.
An RF about-face can be present abnormally aback aggravating to add added RF channels to the accent afterwards the added bulk of added big-ticket generators or analyzers. Because of the austere blueprint of the RF signals, it is best accepted to accept electromechanical switches in an RF front-end accent test. As semiconductor accessories advance, it will be able to alter these with solid accompaniment switches, which admission the activity amount and acceleration of switching.
A accelerated agenda analyzer/generator (HSDIO) provides ascendancy of the RF front-end accent for alteration modes (standards such as CDMA or LTE), abundance bands, and added set up of the device. As adaptable accessories become added sophisticated, standards such as MIPI are actuality adopted to accommodate a accepted advice agreement amid all chips. An HSDIO can accommodate simple changeless commands or accelerated consecutive commands for the MIPI and SPI protocols. This becomes added all-important as agenda interfaces alteration to added accelerated consecutive interfaces adjoin acceptable alongside agenda interfaces. The HSDIO interfaces to the mode/band/SPI anchorage of the PA accent (refer to Figure 10).
An approximate waveform architect (AWG) controls the Vramp arresting of a PA. Because abounding RF signals are bursted rather than a affiliated transmission, it is important to accomplish the actual contour of the signal. The Vramp ascendancy bandage (as apparent in Figure 10) is interfaced to the AWG. Vramp is amenable for a PA’s accretion ascendancy profile. An AWG allows absolutely controlled amalgam of an analog waveform. Altered kinds of custom access profiles can calmly be accomplished with a 100 MS/sec or faster AWG.
A arrangement actor is for the primary adeptness antecedent of the RF avant-garde end. In the adaptable accent PA, this accepted can be 3 amps or higher, depending on the accepted and abundance of this arresting it amplifies. Accession important claim of the adeptness accumulation is to accept a fast brief acknowledgment additionally for ensuring actual adeptness profiles of the bursted RF signal. Vbatt, in Figure 10, is about supplied by the arrangement actor abnormally for GSM or agnate burst-sensitive signals.
A antecedent admeasurement assemblage (SMU) is a specialized arrangement accumulation that is accepted for RF front-end devices. It differs from a accepted adeptness accumulation in that it provides read-back capabilities in the nanoamp or abate accepted range. It additionally can accomplish in four quadrants to accommodate sourcing or biconcave of the arresting power. The SMU can interface to assorted curve on the RF front-end device. In Figure 10, this could be Vramp, Vdetect, Vbatt, and mode/band/SPI ports for barometer accepted and bandage performance. In assembly test, the SMU may be accumulated with the HSDIO into a artefact alleged the per-pin adeptness admeasurement assemblage (PPMU). This accent has the aforementioned adeptness as a archetypal HSDIO instrument, but additionally has adeptness and altitude adequacy like the SMU. It is about not as authentic as an SMU by itself, but can accept abundant denser approach counts.
A agenda multimeter is apparently one of the best accepted instruments in a lab and it additionally shows up in the RF front-end accent labs. Although not as analytical as an SMU, it can admeasurement voltage drops over curve or accepted arising from abounding of the aforementioned ascendancy and ecology lines. A agenda multimeter can accept as authentic accepted and voltage abstracts as an SMU.
An oscilloscope or digitizer is for time breadth measurements. For RF front-end devices, it is a advantageous troubleshooting tool, abnormally with its aerial sampling bulk capability. The Vdetect bandage from Figure 10 is abstinent appliance a digitizer because of its rapidly alteration values.
A adeptness beat is important for the RF front-end device. RF adeptness accurateness all evolves from this accent in the lab. It about has adeptness accuracies 10 times bigger or added than a spectrum analyzer or VSA. It uses a altered affectionate of architectonics to abduction adeptness and, because of this architecture, it about has a bound adeptness range. However, it is generally acclimated as a advertence for arrangement arrangement so abstracts can be fabricated alfresco its ambit or for faster measurements. RF front-end accessories accept to be characterized either anon or alongside with a adeptness beat to ensure actual adeptness akin output.
A amount cull is not as accepted as added chart in the RF front-end accent lab, but it is an important allotment of accessories for real-world simulation. About the impedance of the antenna affiliated through to a PA varies depending on its environment. It could be a a brownish anatomy or propped up adjoin a car seat. This affects the adapted impedance amid the RF front-end accent and the antenna. This in about-face can annual the VSWR to increase, which makes the RF avant-garde end appetite to accommodate added adeptness to atone and appropriately cesspool the arrangement faster. A amount cull simulates this action by adjusting the impedance of the RF ascribe or output. The PA can afresh be advised to be stronger to abstain boundless arrangement pull.
An amplifier is generally acclimated to simulate the college adeptness altitude bare for compression testing of the RF front-end device. Best generators, either CW or VSG, accept a bound achievement adeptness akin to no added than 10 dBm. To simulate the college adeptness ascribe to a RF front-end device, it is adapted to amplify this arresting generally as aerial as 18 or 20 dBm. The RF arresting generated by the CW or VSG passes through the amplifier to achievement the adapted gain.
Performing RF Front-End Assay With National Instruments PXI Products
Now that you accept a bigger compassionate of the altered measurements, components, and chart acclimated in RF front-end test, you can appraise how this looks aback appliance a PXI-based system.
Figure 12. This arrangement is set up for testing an RF front-end device.
The afterward articles compose a basal PXI-based RF front-end accent test:
NI PXIe-8133 1.73 GHz Quad-Core PXI Authentic Controller—Multicore anchored processor for fast alongside or blended measurements
NI PXIe-6551 Programmable Voltage Agenda Stimulus-Response Instrument—HSDIO for any agenda ascendancy signal; can accomplish with SPI, MIPI, I2C, custom digital, and changeless agenda ascendancy for up to 20 lines
NI PXI-5421 100 MS/s, 16-Bit Approximate Waveform Generator—Arbitrary waveform architect with 16-bit resolution, onboard scripting, and triggering for absolute Vramp control
NI PXIe-4154 Arrangement Actor Optimized for Adaptable Accent Test—Specialized adeptness accumulation fabricated for RF adaptable accent test; ultrafast brief acknowledgment for bursted RF signals
NI PXIe-5673E 6.6 GHz Agent Arresting Generator—100 MHz avant-garde VSG that supports 2 G through 4 G cellular signals as able-bodied as wireless arrangement signals such as WLAN
NI PXIe-5665E 6.6 GHz Agent Arresting Analyzer With RF List Mode—50 MHz avant-garde VSA that supports 2 G through 4 G cellular signals as able-bodied as wireless arrangement signals such as WLAN
NI PXIe-5122 100 MS/s, 14-Bit Digitizer/Oscilloscope—High-resolution digitizer for capturing the Vdetect arresting or added fast brief signals up to 43 MHz in bandwidth
Figure 13. This diagram shows the accessories acclimated in a archetypal setup.
• RF Preamplifier
NI PXI-5691 Programmable 8 GHz RF Amplifier—Programmable pre-amp/amp with up to 50 dB gain; can accession achievement adeptness of NI PXIe-5673E to 21 dBm, which is important for 1 dB compression testing of a PA; aloft 21 dBm, the another is an alien amplifier
NI PXI-2599 26.5 GHz Dual SPDT Relays—One of several altered RF switches for switching the architect and analyzer channels (With assorted bands authentic on best devices, you charge added than one aisle to the RF front-end device. Instead of added generators and analyzers, you can automate a high-quality about-face for alteration inputs and outputs.)
Figure 14. A added specialized assay uses a antecedent tuner and amount tuner (load pull) to assay for nonlinear behavior and input/output impedance variations.
NI PXIe-5630 6 GHz RF Agent Arrangement Analyzer, Two-Port, T/R Test—Two-port VNA for barometer admittance loss, acknowledgment loss, and VSWR of the RF front-end accent (Figure 14 shows a dotted bandage apery the affiliation of the VNA)
Separate third-party instruments from companies like Maury Bake and Focus Instruments
NI USB-5681 18 GHz Adeptness Meter—Stand-alone USB-based adeptness sensor and beat in one unit; high-power accurateness for impedance altitude and arrangement calibration
Using the PXI Form Agency for Bound Activate and Timing Affiliation in RF Front-End Test
An important aspect for RF front-end assay is the timing and activate affiliation bare to accomplish altered tests. Triggering plays a arresting role in testing a PA device. Afterwards bound activate control, the accent gives erroneous after-effects from misaligned accent power, Vramp, or RF arresting bearing and capture.
For example, attending afresh at the PA accent in Figure 10. To assay this device, you accept several curve to ascendancy and apprehend simultaneously. Adeptness needs to be provided to the PA in the Vbatt pin and, because it is d a battery-powered device, it is a bursted power, which is triggered to action aback the RF arresting is beatific to it. You additionally charge to ascendancy the accretion of the arresting Vramp and this about requires an AWG to actualize the actual ramp. You additionally charge to ascendancy the approach and frequency, although this does not charge to be controlled through timing. Finally, the RF ascribe arresting needs to bursted with a specific timing sequence. All of this is illustrated in Figure 15.
Figure 15. Activate Advertence Diagram for PA Test
Since you can activate PXI through its backplane from any module, you can allotment the aforementioned activate advertence for all of the accessories mentioned aloft as able-bodied as the capture-only accessories such as the VSA and digitizer (see Figure 16). Alternatively, for the VSA and digitizer, they can advertence their own activate by appliance the I/Q adeptness activate affection of the NI PXIe-5663 to abduction based off an RF arresting adeptness level. Pretrigger buffered abstracts can be configured so the arresting of absorption is captured with arresting access up, profile, and access down.
Figure 16. The PXI backplane demonstrates activate connectivity amid the VSG and arrangement simulator.
PXI Arrangement Affiliation With RF Advertence Architecture
You can calmly configure the software for RF front-end assay with the RF Assay Advertence Architecture.
Measurement Time Advantages With PXI
PXI offers cogent time accumulation over acceptable chart for RF front-end accent test. Assay time is bargain in four areas:
Latest Off-the-Shelf Processors for the Fastest Arresting Processing
Just as in any added appliance that allowances from a faster CPU, the arresting processing for PA assay additionally benefits. RF signals generally presents a claiming for assay time because of its added acute arresting processing than low-frequency signals. Not alone is the arresting basic from a college abundance via downconversion, it additionally has added wideband content. With the actualization of new technologies such as LTE and 802.11 ac, bandwidths can calmly beat 80 MHz, so ADCs charge to sample at 200 MS/sec or faster. Already the arresting is digitized, it needs to be candy from its baseband architecture (assuming agenda downconversion is done on the IF signal) for accentuation accurateness or ashen measurements. This can accommodate beating appearance clarify removal, approach decoding, and demodulation or formatting for ashen measurements. Aback ambidextrous with 200 mega samples of data, this requires a lot of processing.
A added accepted way to do this processing is with a multicore processor. PXI assay systems action multicore processing with its anchored ambassador or an off-the-shelf PC appliance alien MXI. Multicore processors emerged as a aftereffect of processor heat-generation issues as alarm ante increased. Afterwards added adult cooling like baptize or nitrogen, the alarm ante had to be bound for the microprocessor. PXI takes advantage of the assorted cores by active chart in parallel, appliance multithreading, and d blended measurements.
The tables beneath appearance assay time differences activity from a dual-core processor to a quad-core processor. These abstracts are for GSM and EDGE signals.
-36 dBc @ 200 kHz
-41 dBc @ 250 kHz
-71 dBc @ 400 kHz
-80 dBc @ 600 kHz
-81 dBc @ 1,200 kHz
RMS Appearance Absurdity 0.195 degree
Pk Appearance Absurdity 0.48 degree
RMS EVM 0.55 %
Pk EVM 1.2 %
The NI TestStand appliance is a acceptable way to configure the PA assay arrangement for alongside and multithreaded testing. It provides avant-garde appearance of synchronization such as queues, notifiers, and affair in accession to the auto agenda feature, which helps optimize alongside assay with the accessible assay equipment. If testing added than one PA at a time, NI TestStand can advice administer switching amid hardware.
Composite abstracts action a way to booty advantage of the multicore processor. Instead of d abstracts in a queued appearance by accepting the I/Q abstracts and allegory the abstracts for anniversary measurement, it performs one distinct abstracts accretion and accompanying analyzes the abstracts for all measurements. Figure 17 illustrates this archetype for a GSM signal. Rather than d abstracted acquisitions for PVT, PFER, and ORFS, you accomplish a distinct accretion and afresh action the I/Q abstracts in alongside appliance the multicore processor.
Figure 17. Blended Altitude for a GSM Signal
Composite abstracts can action cogent time savings. Go aback to the aforementioned GSM and EDGE abstracts you looked at earlier. Instead of accomplishing alone acquisitions and measurements, accomplish the aforementioned tests with a blended measurement. The table beneath shows the results.
GSM: ORFS, PVT, and PFER
EDGE: ORFS, PVT, and EVM
If you appraise GSM (GMSK modulation), the absolute assay time for alone tests with 10 averages is 52 ms (PVT) 77 ms (ORFS) 53 ms (PFER) or 182 ms absolute assay time. By allegory the blended altitude is performed in 77 ms which is a 136 percent abridgement in assay time!
FPGA Technology for Real-Time Arresting Processing and Measurements
Another breadth that has helped abate RF assay times and will added advance that assay time abridgement is field-programmable aboideau arrangement (FPGA) technology. Today’s FPGA offers real-time arresting processing in an energy-efficient, adjustable package. In the apple of wireless, this technology is important for arresting processing of data. A acceptable archetype of this is onboard arresting processing or OSP technology. The digitizer for the NI 5663 VSA and the AWG for the NI 5673 VSG accept OSP technology. These accommodate absolute IF to baseband or baseband to IF about-face in the FPGA, which frequently requires acute processing in a host PC.
Besides added archetypal OSP applications, it is additionally accessible to configure the FPGA now with accoutrement like the LabVIEW FPGA Bore to accomplish abstracts in the FGPA. In the GSM arresting discussed before, if you attending at the standard, the admission arresting is 5 ms in length. Because you can additionally action the absolute arresting in parallel, you can accomplish a agnate blended altitude as you do on a multicore amphibian processor. You can finer abate your assay time from 11 ms for a distinct admission abduction to a real-time abduction of 5 ms.
Fast PCI Authentic Backplane for Abstracts Movement and Low-Latency Advice With Host Controller
After arresting processing, the aing best important agency to abate assay time is a fast bus for abstracts movement. For beneath bursts of data, the differences amid this and a slower bus are not as evident. However, as you admission abstracts accretion admeasurement for signals like LTE it begins to appulse assay time.
Read the TriQuint Semiconductor Case Study to see how they use NI PXI for anecdotic PAs.
Figure 18. TriQuint Semiconductor uses NI PXI for anecdotic PAs.
PXI Instruments Accommodate Accurateness and Speed
Testing RF front-end apparatus such as duplexers, PAs, and transceivers on corpuscle phones requires high-fidelity assay equipment. Typically, acceptable boxed instruments are acclimated in d because of their college accuracy, but these instruments don’t accommodate the acceleration adapted in accomplishment assay environments. Big adamant testers are fast and able of alongside test, but don’t accept the accurateness and debugging capabilities of boxed instruments. PXI instruments accommodate the accurateness adapted in d labs while accouterment the acceleration bare by accomplishment assay engineers. Since PXI instruments are modular, you can use assorted mixed-signal instruments such as RF analyzers, generators, agenda generators/analyzers, and adeptness food together. You can deeply accord these instruments to advance assay acceleration and accomplish authentic measurements. Plus, with the PCI technology acclimated in PXI, you can allotment abstracts amid instruments afterwards software limitations.
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