RF Testing-Equipments, skills, measurements during RF testing

This article on RF testing covers RF equipments,skills and measurements performed during RF testing. It mentions common types of RF testing performed on RF components or systems.

Introduction: As we know RF systems are evolving from complete analog to digital or mixed signal type. Due to this, testing a RF system has become very critical tasks. There are numerous tests performed on RF DUT (Device Under Test) using sophisticated RF equipments to determine PASS/FAIL criteria based on standard specifications.

RF System block diagram,rf testing

RF System can be divided into transmitter and receiver sections.
• Transmitter consists of baseband Tx part (Physical layer Transmitter), DAC (Digital to Analog), IF modulator (i.e. I/Q modulator), RF up conversion, PA (Power Amplifier) etc. Baseband Tx part uses FEC encoder, interleaver, data mapping (bits to symbols conversion), baseband filtering etc.
• Receiver consists of LNA (Low Noise Amplifier), RF down conversion, IF demodulator (i.e. I/Q demodulator), ADC (Analog to Digital), baseband receiver part. Baseband Rx part uses baseband filtering, data de-mapping (symbols to bits conversion), de-interleaver, FEC decoder (i.e. viterbi or CTC) etc.
• Both uses AGC (Automatic Gain Control) in order to take care of dynamic range of signal it their respective chain.
• Antenna is used for RF signal transmission and reception for over the air (OTA) testing. RF upconversion converts modulated IF output of IQ modulator to modulated RF output. IQ modulator processes I/Q baseband data and provides modulated IF as output. RF downconversion converts modulated RF to modulated IF. IQ demodulator takes modulated IF and provides I/Q baseband data. Filtering helps to narrow down the bandwidth of RF system and at the same time ensure that system meets required BER.

RF Testing is categorized into following based on life cycle of the RF DUT. It is often recognised as radio conformance tests.
• Prototype testing: This test is conducted both at unit or module levels and at system level.
• Production testing: This requires testing of multiple DUTs to acertain RF units are working as per designed specifications before final deployment or dispatch to customers.
• Environment and reliability tests: It covers climate tests such as temperature, humidity, altitude, bump, accelerated life tests etc. QM 333 Chart is used for the RF testing at various temperatures/humidity levels.
• Field testing: This is performed for prototype system after installation. It is conducted to verify short term and long term stability performance specifications.

RF Equipments and skills required during RF Testing

➤RF engineers require following skills in order to meet expectations of the stakeholders in the RF company. • RF domain skills: Knowledge of RF design, transmission line concepts such as S-parameters, digital RF communication system etc.
• RF Test Equipments: Should be familiar with RF signal generator, signal analyzer, spectrum analyzer, power meter etc.
• Programming language: Some RF jobs may require knowledge of programming languages such as C, C++, MATLAB or Labview. Automation jobs require knowledge of Python language to develop or use automation tools.
• Communication skills: RF engineers should be good in written and verbal skills.

➤Following are the RF test equipments used during RF testing.
• Spectrum Analyzer: It is the most generic tool used for frequency versus power measurement. This frequency analysis tool helps in identifying frequencies such as spurious, harmonics etc. in the span set by the user.
• Signal Generator: It has options to generate either baseband IQ signal or modulated RF signal. It is used for testing receiver functionalities of RF DUT. Signal generator is available as software version or hardware module or combination of both.
• Signal Analyzer: It has options to analyze either baseband IQ signal or modulated RF signal. It is used for testing transmitter functionalities of RF DUT. Signal analyzer is available as software version or hardware module or combination of both.
• Power Meter: It is used along with various power sensors to measure peak and average power of RF signals. Power meters are available for lower frequency as well as higher frequency measurements. It measures power in units of dBm or dBW.
• There are other equipments such as noise figure meter, network analyzers, noise dosimeter etc. Refer RF Test Equipments >> for more information.

RF Measurements performed during RF Testing

RF measurements during RF testing

The figure-2 depicts common RF measurements performed during RF testing at various stages of RF DUT life cycle.

Other RF Testing for RF components and Systems

Links to useful Testing and Measurements

Following are the links to other useful measurements available on Test and Measurement World website.
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Current measurement vs Voltage measurement
Inductance measurement vs Capacitance measurement
Difference between Power and Energy measurements
EMC measurement vs EMI measurement
Electric and Magnetic Field Measurements