Understanding the role and implications of impedance in RF transmission lines and antennas is vital to successful system performance. The importance of impedance matching, minimizing reflections, and keeping a low VSWR means these topics have been studied extensively, ranging from analytical perspectives through many physical designs and implementations. This section looks at some matching techniques. […]
FAQ
Negotiate through 1/f noise challenges towards sample sizes into the 100s of years
Measuring and determining 1/f voltage noise over a multiple-year sample requires an operational amplifier and effective 1/f knowledge. This article shows how to identify and determine the actual op amp 1/f voltage noise across a sample size of years and explains why the 1/f voltage noise is a non-issue at higher frequencies. After many years […]
VSWR and impedance, Part 4: Measurements
Understanding the role and implications of impedance in RF transmission lines and antennas is vital to successful system performance. The previous section looked at the basics of VSWR. This section looks at two approaches to measuring impedance and VSWR. Q: What do engineers and users need to know? A: For some applications, such as connecting […]
VSWR and impedance, Part 3: Implications
Understanding the role and implications of impedance in RF transmission lines and antennas is vital to successful system performance. The previous sections looked at the basics of impedance and VSWR. This section looks at the implications of VSWR measurements. Q: Why should I care about reflected waves due to impedance mismatch and resultant non-unity VSWR? […]
VSWR and impedance, Part 2: Reflected power
Understanding the role and implications of impedance in RF transmission lines and antennas is vital to successful system performance. Part 1 of this article looked at the basics of impedance matching and power transfer. This part looks at the closely related topic of nominal impedance and VSWR. Q: Why all this worry? Aren’t RF systems […]
The basics of VSWR and impedance, Part 1
Understanding the role and implications of impedance in RF transmission lines and antennas is vital to successful system performance. In any design requiring transfer of an RF signal and its energy from one functional block or component in a system to a subsequent one in the signal chain, there’s almost always the issue of impedance […]
Understanding the lock-in amplifier, Part 2: The homodyne solution
The lock-in amplifier allows tiny signals from sensors to be captured with precision despite unavoidable noise limitations and other test and measurement challenges of the signal chain. Part 1 of this article looked at the challenges of capturing low-level signals such as from a photodetector despite unavoidable signal-path noise, drift, offsets, and other imperfections. This […]
Understanding the lock-in amplifier, Part 1: The sensing challenge
The lock-in amplifier allows tiny signals from sensors to be captured with precision despite unavoidable noise limitations and other signal-chain test and measurement challenges. There are some basic test and measurement instruments common to scientific labs and engineering benches of all types, whether electronic, biomedical, chemical, optical, or mechanical. Among these are the digital voltmeter, […]
Sigma Delta ADC vs. SAR vs. Pipeline: How to Choose
Assuming that you are familiar with the fundamental specifications of an ADC and what they mean, the next step is to know your entire signal chain well and then work to fit the ADC to the requirements. After carefully determining signal chain requirements, then select your ADC with the understanding that if the ADC is […]
Reducing ringing or reflections by controlling impedance lines
What is a controlled impedance line? For one thing, the term has to do with Printed Circuit Board (PCB) traces and layouts, which get more complex with higher frequency signals. Generally, you need not worry much about controlling impedance in traces unless you are working with signals at or above 50 MHz. However, most of […]