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7

Where the proximity to a ground conductor only happens for a short length of track, a small fraction of a wavelength, you can regard it as an extra lumped capacitance to ground. Depending on the quality you need from the track, you can ignore it, or you can thin the track down at that point to make it a little inductive, which turns the shunt C into a ...


4

100Hz or 120Hz noise is often caused by power-supply ripples or rectifier glitches. those being twice the mains frequency in different locations.


4

Can I use a 2.4 GHz rated parabolic MIMO antenna for 700 MHz Verizon 4G LTE data? The gain of an antenna, that is, how much it focuses in one direction, is pretty much proportional to its size divided by the wavelength. Generally, antennas don't work (well) for frequencies they're not designed for, but you can consider a parabolic dish more of a reflector ...


4

Just regard it as an amplifier with feedback where the real input is set to a value of zero: - in negative feedback the feedback signal is added to the input signal, in positive feedback is subtracted. So in the first situation we use and adder circuit, in the second one a subtractor circuit. Feedback +/- input is the same as feedback +/- 0 when the ...


2

The efficiency of typical RF trasmitter is between 20...30% for AM transmitters, and 40...70% for FM transmiters. It means, the transmitter expects on main power 2...4x greater than output power. For your example, 100,000W = 100kW on RF output means needs about 200...400kW of mains.


2

An MZM modulator requires fairly high voltage. (Also search on EO, electro-optic modulator. Also Lithium Niobate, the dielectric material typically used.) Drivers for EO electro-optical materials usually employ an RF amplifier, followed by a tuned circuit (an impedance-match network, series-resonant Pi type,) designed for the drive frequency. The tuned ...


2

Q1: Does the nonlinearity of the amplifier near 1 dB point actually mean that the impedance is changing, and hence I have to re-optimize? Yes, the impedance changes. Impedance matching is a concept based on the fact that the system behaves linearly. That means doubling the input signal will double all internal signals and the output signal. Also any ...


2

First off, it can be hard to tell the difference to the untrained ear between power line frequencies and their harmonics. It's really important to try and measure the frequency (or frequencies) of the noise, as that can provide important clues as to what might be wrong. Measuring the spectrum with a microphone-based FFT worked really well. If the tone knobs ...


2

Yes, that's possible, and you'll find directive multi-band antennas commercially-off-the-shelf. These internally mostly resemble Yagi-Uda antennas, but don't have the same director sizing as actual Yagi-Udas. Probably, they were designed starting as Yagi-Uda, and then stochastically optimized in simulation until they worked well enough on multiple ...


2

The internet is different than the radio spectrum: you explicitly need a license to transmit in any radio band! With Wifi, Bluetooth and the like, you buy devices that are tested to only operate in so-called license-free bands, where an exception to that rule exist. Since you're not a radio engineer, you'd not start by trying to build a device that fits ...


2

Curves in the left are two different presentations how the reflection factor seen by the feeding circuit depends on frequency. The yellow curve is the standing wave ratio which is calculated from the absolute value R of the reflection factor with formula SWR= (1+R)/(1-R). It's not measured directly, it's calculated. You should see that it's quite near 1 at 2,...


1

The plots on the right are the antenna patterns at 3 different frequencies. The plot on the left looks like it's the measured S11 (input return loss), though the scale values don't make sense.


1

For CE (or the new RED now) is not compulsory to use a RF shield. Using a shield will help you with unwanted spurious emissions. That is, if you are radiating at 2.4GHz by your antenna, from your PCB there will be unwanted emissions at different harmonics frequencies 4.8GHz, 6.2GHz... etc, these emissions are regulated and you if you emit more than what the ...


1

I am going to simplify this for you. No, you cannot use the 2.4 GHz antenna for 700 MHz. The parabolic part of the antenna may still provide a little bit of gain, but it won't work nearly as well as it did at 2.4 GHz. More importantly, the antenna is probably not passive. I base this on the fact that the band specified is very narrow if it were a purely ...


1

The gain and directivity of a parabolic dish is inversely related to the wavelength of the signal and directly related to the size (diameter) of the dish. The wavelength at 700 MHz is approximately 3.5 times greater than 2.4 GHz. Hence keeping the dish size constant and lowering the frequency (increasing the wavelength) by 3.5 will result in a drop in gain ...


1

Option 1 should be best. It has less GND impedance than Option 2 because it is closer to the antenna and it has better capacitive coupling to the other GND layers. I do not understand the cited text and I can not think of a single reason why you not should connect all the GNDs you have together as good and close as possible. An antenna is like a ...


1

Once happened something similar to us, also at 900MHz. We had a ceramic antenna soldered in our PCB with a very small ground plane. As the performance was very poor we contacted the antenna manufacturer and they propose adding a copper tape directly to our ground plane, that improved a lot the efficiency. The copper tape was something like this: https://www....


1

Theoretically this would work, but there are some real life limitations. For instance, with a 20 dB pad, is the expected reflected power still within range of the analyzer? Also, the return loss of the pad would have to be pretty good (~better than 30 dB) to get accurate results. If you have known test units that you could try with and without the pad ...


1

If you just added, then all the baseband energy would still be in the baseband. 0 - 5 kHz or so, assuming we're talking about analog. So it wouldn't be transmitted by an antenna that works at 531 - 1602 kHz. It also wouldn't be separated from the signal of any other channel operating on the same system.


1

Looks like a 433 MHz oscillator, transistor "R25". The trace that likely radiates RF is around the perimeter, in yellow on the "bottom" side of the PCB: The transistor collector is fed DC battery voltage through "L3" marked in yellow.


1

You might use a diplexor in the antenna feed. I believe such a construct will provide 2 output channels.


1

In general, can I use the ADCMP552 as negative LVECL (even though it's only specced for positive ECL)? Yes. The chip doesn't know which node in your circuit is "ground". So you can connect VCC to the node you call ground, and the chip's AGND pin to what you think of as -3.3 V, and the chip won't know anything but that there's 3.3 V potential difference ...


1

Non linearities in the transistor will inevitable make the loop gain equal to 1 at some peak to peak amplitude and, the natural impact of this is that the amplitude is difficult to precisely predict (not normally a big deal). The second impact is that the sine wave output will be naturally flattened on one or both peaks and, again, this is often not regarded ...


1

In feedback systems the feedback signal is fed back to the input of the amplifier. This definition does not require that it is added or substracted from an external input signal. In oscillating systems there is no input node - however, if you want you can create an input node and you can use it - for test resp. calculation purposes - to connect an external ...


1

Often the quoted transmitter power is the Effective Radiated Power (or ERP). This includes the gain of the antenna which can be high if the intention is to beam the signal in a specific direction. As Tim states in the comments, this means that a lower transmit power is actually required for a given signal at the receiver; this may seem to result in ...


1

Cellphone service is not required for GPS, and for hiking is actually detrimental since powering a 2-way radio wastes limited battery. When back country hiking, I take an old smartphone in airplane mode. With the cell radio powered down, I'm often good for a week or more on a single charge. If you need more than that, bring a battery pack.


1

simulate this circuit – Schematic created using CircuitLab


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