6.5 KiB
Rhode and Schwarz Presentations - Long Island 10/24/2023
Presentation 1: James
- EmC presentations - gtime FFT
- Emissions
Summary:
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Compliance testing is required for most electrical devices
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Failure rate in full compliance is quite high
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Redesign + retest is retired
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Precompliance testing is very important
Questions:
- Anyone melted a probe? (people have definitely melted antennas)
Signal Generators
Topics:
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Primary purpose of signal generators
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Produces electrical wave forms of various a mplitudes, frequency and phase properties
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Signal sinusoidal (CW - Continuous wave, SMW-2WA - the “flagship” Signal Generator)
Why are they important?
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They provide close to ideal input signals to the device under test (DUE_
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They emulate real-worls signals in the case of complex - moulations 5G, LTE, Wifi
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Good performance ois important to minimize generators
Signal Generators → 1. Analog Generators 2. Digital Generators
Analog Signal Generators
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Frequency, basic modulation, boise and spectral p
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Major reason for switching to analog
Veector Signal Generators
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Frequency and level range
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Noise and spectral purity → modulation BW + capabilities
Analog
(insert image here)
Vector
(insert image here)
What do we need an analog generator for
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High quality singals
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Reference code
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Gain
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Component development / testing (ADCD_
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Receiver testing
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Military / radar applications
AM Frequency modulation FM frequency modulation Phase freqeuncy modulation
Analog Generator Selection Criterai -- things to consider
Primary:
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Frequency range
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Phase-noise
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Harmonics
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Output power
Secondary
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Switching speeds
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Frequency + amplitude accuracy
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Very bad modulation support
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Very important to understand your input signals
Vector Signal Generator Applciations
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Receiver testing - a huge applications
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Impairment generation
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Impulse testing
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Fading capbiliites, ability to generate attenuated delayed signals
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Radar echo preparations (GNSS)
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Multipath signal generators
Vecotr Signal Basics:
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Analog signals defined by magnitude
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Vector signals defined by: magnitude + phase
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Used in digita modulation
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LTE, SGNR, Wifi, Bluetooth, SatCOM
ASK, PSK, FSK
Generating IQ Values
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Start with Symbol that represents particular magnitude _ phase
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Magnitude + phase can be converted into can be converted into
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In-phase (“real”)
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Quadratic (“imaginary”)
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Simplifies the pair of IQ vzlaues
IQ Modulatior
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Converts base band (transmitting) signals into RF Signals
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This allows the AM FM PM to sum the signals
IQ Modulation Steps
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Many licensing keys that you buy/input
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ca n bring data in digitally (bring the IQ values in digitally) - various ways to define the baseband
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Can have a file of IQ values
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Specific data that has been mapped to IQ values
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Appropriate IQ values are generated based on what you selected
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Seiteis fo steps involved in creating a vector modulated signal
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Basic Digital Modulation - each variations of a signal magnitude _ phase represent a unique symbol
Each symbol represents a specific digital bit or combination of bits -
ASL - Amplitude of 100% and 50%
BPSK - phase 0 degrees and 180 degrees
Constellations (Symbol Mapping)
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Constellations - collection of symbols on a polar chart representing a signal and magnitude and phase
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X - acist depicting amplitude (I )
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Y - as depicting phase (Q)
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ASK depicts 2 symbols with 1 bit of info - modulating in amplitude
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BPSK chart depicts 2 symbols molulating only in phase
How do we add more bits/symbols/information for faster data transmission?
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Through QAM symbol mapping
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Could transmit only 1 bit previously can transmit 4 bits now!
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These mits make up the frame of our wifi, transmission, bluetooth, etc..
Modulation Bandwidth
- Some LTE at least 10 MHz of bandwidth requires
- Frequency - generators RF frequency , usually the carrier signal
- Bandwidth
- ** important tto distinguish what the signal rate is and what the bit-rate is **
- Flatness is the gain variation of the platform
Impairment Generation
- Another huge reason for vector
- previously talked about band base generation
- Able to do fading and noise injection
(include image here)
- impairment s emulate real-world effects
- Keeps up with standards as well
- Base band impairments - noise - SW interferes - impulse noise - phase noice -
- Fading - ability t o generate copies of a signal , attenuate them, or dopplegang them
AWFN impairments
- Additive white gaissian noise additive -
- Additive Combine dwith useful
- White: noise constant other frequency
- Gaussian - describes how noise changes over time ODFM (orthogonal)
- 23 ASK Constellations ODFM orthogonal
- Considered more immune than QM
- Device under test → mini circuits amplification
AWGN Generation
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Constellation drawn by the analyzer
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Analyzer (receiver basically) no trouble achieving
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Signal to rnoise ratio - APSK (PVB -52, Digital Viceo Broad cast
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This is very important for devices that are re-timing the circuit
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Needs to be able to filter out the (phase) noise that you inject
Phase noise impairment:
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Anything coming up in time domain (called jitter)
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Anything long0term in time domain (called wonder)
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Excessive phase noise can cause many issues
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Disturbance in communication systems for instance
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Phase noise can be addes to base bands signal by
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Define amount of phase noise at gain - frequency offsets
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Adding phase noise to signal leads to rotation
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Errors → adjacent signal / symbols bleeding into other symbols - bit-error
Impulse Noise impairment - many real wprld examples of impulse noise impairment
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unintentional - spark plugs motors,
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Intentional - radars, or bursty , modulation time
Fading:**