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24

Digikey sources their parts from the manufacturers and adds a retail mark up. The alibaba seller takes remnants from someone's production run (or possibly salvaged parts, or if you're unlucky counterfeit or reject parts) they don't pay full price. Usually it's remnants, someone makes 10000 products and has 500 parts on the last 3500 part roll left over and ...


9

I would say that they are probably counterfeit,this is a well known problem when buying from china, you cant be sure that they are original unless you are buying from a trusted chinese supplier. Most of the time they work alright if you are not pushing them to the spec limits,here are some links that can help you through this problem of chinese counterfeit ...


5

Your assumption seems to be that filtering only one time is enough. That might be true but it might also not be true, it depends factors like: How much filtering outside your band of interest is needed? If there are strong signals present at frequencies you do not want, you might want to suppress these as much as possible before they end up (with too much ...


4

The antenna resonates at a particular frequency Not true. A whip (monopole) antenna (for example) produces an optimum output level for frequencies that are close to one-quarter wavelength. It will also produce a decent output level for frequencies surrounding that optimum frequency and the "spread" of those frequencies from "centre" can be considerable and ...


3

Shall I connect the GND of the bus to my GND via balun or what? Conducted emissions (Rf through cables) can be stopped with ferries or inductors. However placing a baulun or other impedance on the ground to block high frequencies can have unintended consequences. Ground inductance can create common mode voltages (ground bounce) from fast switching currents ...


2

The width of the stripline is not a design target in itself. You design a transmission line to have a specific impedance, to match the antenna or whatever is at the other end of the transmission line (or both, if possible). So, you're right to calculate based on your actual substrate and copper properties. Both 1.3 and 0.3 mm are feasible widths, and ...


2

You are struggling because the diagram you are looking at doesn't say anything about how to mount the antenna. Figure 9 is a GPS receiver with a connector for an external antenna. Farnell has a datasheet for your antenna. This datasheet includes a layout for the test jig used in their tests of the antenna, as well as drawings that show how to design the ...


2

The wavelength of 60Hz is huge. In your convenient local-lab measurements, you will be in the "near field" where the Efield acts independent of the Hfield (magnetic field). Simply dangling a wire from a 10Meg Ohm scope probe should get you volts of 60Hz. Bring the wire near the scope's powercord. Or near any light fixture. Set the scope to 20 or 50 ...


2

No. Relative permittivity (a real number the way you specified it) and \$\tan\delta\$ are two different properties of a material. You can have a low-loss and a high-loss material with the exact same real part of the permittivity. You should probably re-read your material; you'll find something about complex-valued wavenumbers, and you'll see why ...


2

At RF, there is nothing as simple as a conductor. It is quite possible that these features are doing several things (improving radiation, reducing interference, at different frequencies). The design will be partly by simulation, and likely partly by comparison of a handfull of prototypes with 'variations on a theme'. For example, #1TL looks like it could be ...


2

Probably slot antennas, you could figure out the length by the width, length and the material around it. I'm not sure if these are antennas for the wifi module or a way to null the RF from the wifi modules (I'm not an antenna expert, I mostly design things to stop RF propagation). They most likely had a electromagnetic FEM solver to design a board like this ...


2

JRE's answer has already identified that the connector on the Nordic board is a switch type, so none of these examples have both antenna options connected at once. As to the other part of your question - why can't both be connected at once - the answer is impedance matching. The integrated antenna will be designed to present a particular characteristic ...


2

I took a look around the Nordic documentation. You don't need a jumper on the Nordic board because the RF connector it uses has a switch. The connector is of SWF type (Murata part no. MM8130–2600) with an internal switch. By default, when there is no cable attached, the RF signal is routed to the onboard PCB trace antenna.


1

I don't design these kinds of antennas and my books on the topic are at work, so I'm not sure, but you will find you already got into trouble with your length calculation. You used the speed of light in a vacuum to calculate the length. (notice the 'in a vacuum' part). On a PCB the wave will travel more slowly. Your microstrip tool helpfully points out that ...


1

I would like to know if the same trick can work with NFC readers No the same trick cannot work with near-field tags using aluminium foil. Aluminium foil placed close to the tag will act as a partially shorted turn of wire and reduce the magnetic field due to eddy current losses in the aluminium. However, you can purchase rubberized ferrite sheets that can ...


1

If you want to be on the safe side and have enough board real state, I highly recommend you simply use a 1"x1" ceramic patch antenna soldered to your PCB. The patch antenna is circularly polarized while most of the PCB trace antennas are linearly polarized. This gives the patch antenna at least 3dB of performance advantage since GPS satellites transmit ...


1

After testing the actual setup, I was able to get a successful exchange between the smaller reader and the larger tag. Comparing the same tag on another, larger reader show that the smaller tends to have more erroneous transactions and the range is very limited, but I am still able to get valid transactions with a valid CRC.


1

Microchip has technical information about antenna design at 13.56 MHz. Start with AN710 "Antenna Circuit Design for RFID Applications".


1

Well, the antenna contacts are on the top of the module under the metal cap – you'd have to build an RF transmission line (for example, a coax cable, or a microtrip line) to attach any antenna at any other point than that. Since that is relatively complicated and hence relatively expensive, these modules where designed and tested to work with the antenna ...


1

Antennas don't have "range"! An Antenna is the interface/converter between the electrical signal that the electronics use and the air, where the signal travels as an EM-wave. There is nothing in the antenna that defines the range. Sure, the choice of antenna and how you use it influences the range of the system but the antenna itself does not determine the ...


1

You're right, this is a ground plane, but as the antenna to the right is a PIFA, its characteristics are most influential on the antenna impedance and its radiation pattern. This looks like a way to be flexible about antenna matching: If after design some parameters of the board change (e.g. PCB substrate \$\varepsilon\$), or its surroundings (e.g. battery ...


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