# Tag Info

### How are S-Parameters and Reactance related, can one be calculated from the other?

Maxim Tutorial 2866, equation 2; along with other sources; cover this. Essentially: $$Zin = Zo \left( {1+S_{11}} \over {1-S_{11}} \right)$$ where Zo is your measurement system impedance, generally ...
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1 vote
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### How is this possible: Crystal filters for FM signals?

11MHz/100,000 = 110Hz of deviation allowed. Our signal is frequency modulated with ± 75kHz so would this mean data loss? Yes. Broadcast FM needs 200 kHz bandwidth. Traditionally wideband broadcast FM ...
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### Analog television: What is the difference between the first IF and second (demodulated) IF?

It's helpful to include a link to the datasheet even if, as you note, it doesn't explain the circuit operation. Why is the video carrier frequency 38.9 MHz but the audio 33.4 MHz? On-air the audio ...
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### Frequency Counter Input Impedance

RF has signal integrity issues at 1 MOhm above 50 MHz due to resonance. The low impedance dampens the ringing from inductance and self capacitance of cable or reflections from longer cables from ...
1 vote
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### Simple Diode Mixer Help

In an unbalanced single diode mixer it is important to provide a DC path through the diode to ensure that the bias conditions are correct. There should be significant conduction occurring during the ...
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### How to Use a 2.4GHz Chip Antenna for ESP32 Design

I am 2 years late, The product specification document http://www.molex.com/pdm_docs/ps/PS-47948-001-001.pdf has a layout guide, Pleas follow it.

### Can I solder a wire antenna to the exposed PCB antenna of a BBC Micro Bit to boost its bluetooth signal?

Sure you can. Cut the trace antenna and solder a suitable 50 ohm 2.4ghz tuned antenna to it, and ground. But should you? You may find that you have little to no performance increase. The trace antenna ...
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### What is the link between conjugate matching efficiency and amplifier efficiency?

You'll find that the Wikipedia article you mention does make a distinction between maximum power transfer and maximum efficiency. It further states that "The theorem results in maximum power ...
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Can your SDR measure signal strength at specific frequency? If so a simple test is to measure the noise power at a frequency where no signals are present (maybe place Antenna/LNA in shielded box). ...
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### Audio noise when transmitting radio packets using the ESP32

So I figured it out. I assumed that the 5V line (actually battery, so more like 3.7V), was not susceptible to noise and was 100% consistent. It was not. Apperently there was something like 100mV noise ...
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With that enormous power density of 1kW/m**2 at the receiver location, it would be difficult to design a single directional antenna feeding a discrete rectifier that is small enough to function at 35 ...
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For starters, if you want to maximize the amount of power you capture, you want as big an aperture (antenna capture area) as you can build. You said you can expect a power density of 1 Kw/m^2 at the ...
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### Costas Loop QPSK/4QAM

Thank you Tesla23 for your comments/help. I got the loop working, the graphic in my question works. My error was some incorrect signal conditioning when I was driving the mixers.
1 vote
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### How to choose a sweep range for a known and unknown device with a VNA?

With just a VNA, you're only able to check the impedance match of the antenna, not its radiation pattern, gain, or other characteristics. If you know the intended frequency range for use, there's no ...
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### Allow 12v power through when RF transmitter is close

MAX9075 is a comparator, and its two inputs (marked + and -) can be swapped to invert the logic. Note that the comparator is not suitable to drive a 12 V load directly - you should instead use a ...
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### RF high power amp bias scheme

Fred, I was thinking of something like this. Not perfect, but very simple. I think my issue might be the R1 resistor. The R1 is the gate, so I guess I could assume High Z. The node between R2 and R3 ...
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### RF high power amp bias scheme

Here is my proposed solution. Please revise and let me know if you have any concerns or point to details I may have forgotten.
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### Bandpass filter doesn't work when implementing PCB

Each track has both inductance, capacitance and resistance and thus a characteristic impedance from Z^2=L/C I believe you only have trace inductance. That will not work. There are ways that do work. I ...
1 vote

### Diode SPICE data accuracy at high frequencies?

You cannot extrapolate Spice data where geometric impedances affect the conductance and junction capacitance assumptions in the datasheet. "Measured at a LO frequency of 9.375 GHz, with an IF ...
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### Synchronized two frequency source seems to have phase drift

The problem is that AWGs are often, well usually, binary based internally. The attitude of many AWG manufacturers is that once you can approximate your desired frequency to the nearest μHz, it's '...
• 140k
1 vote
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### Antenna feed trace keep it short or long?

Optimize positioning of the antenna on the PCB: it should be at the upper right corner, not halfway up the right edge. Minimize bends and jogs in the microstrip transmission line. Every discontinuity ...
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### Designing GPS matching network with TESEO and chip antenna

Since you're using the LNA and SAW filter, you need to include the series capacitors, but they don't play a role in impedance matching. Why? The reactance of a 120 pf capacitor at 1.5 GHz is less than ...
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### Does an antenna have to be impedance matched to its transmitter circuit or the transmission line from it?

Antenna, transmission line, transmitter/receiver don't need to be matched. A better question would be 'what are the consequences of any degree of mismatch?' Mismatch causes signal reflections, which ...
• 140k
1 vote
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### Does an antenna have to be impedance matched to its transmitter circuit or the transmission line from it?

Does an antenna have to be impedance matched to its transmitter circuit or the transmission line from it? If the t-line is short i.e. less than one-tenth of a wavelength of the carrier frequency, ...
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