New answers tagged

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All of these components are nominally 50 Ohms. For a receiver, improving the impedance match doesn't have a big payoff, so if you're not experienced, you are probably better off putting a DC blocking capacitor between the each stage and moving on. I'd suggest this, because the LNA may be biased internally in such a way as to have a DC voltage at either the ...


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It looks like an MCX. The inner diameter of the receptacle is spec'd at 3.45 +/- 0.03 mm, which is pretty close to your drawn width of 3.3 mm, and has some measurement error. The receptacle depth is spec'd at 4.0 mm, which matches your drawing. See dimensions labeled B and G in this MCX spec sheet: http://www.xmultiple.com/Suggested-MCX-5.htm


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It looks to me like an MCX connector. For example, this one from Amphenol: I'm not sure why this one doesn't seem to have the dielectric protruding around the center contact like yours, when it is shown in the general diagram below. The 3.5 mm inner diameter you measured is pretty close to correct: (Image source: Amphenol)


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Looks like you have calculated quarter wavelength at 4.7 GHz. You need to double the length of microstrip for 2.4 GHz. Check out the simulation and schematic. (I have use the same substrate and values you used) Try to do EM simulation in ADS with the layout for better and accurate results.


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Your microstrip lines are shown as 0.348" long, which is 8.84 mm. Given the speed of light in FR4 is roughly c/2 1, this corresponds to an electrical length of about 16 mm. As a Wilkinson is built with λ/4 line, it's tuned to a wavelength of about 64 mm, or a frequency of c/λ = 300e6 / 64e-3 = roughly 4.7 GHz, which is what your plot shows. Double the ...


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Add capacitors before the motor. Put wire mesh or screen around the motor and wires to act as a Faraday shield. Make sure your ground game is on point too. Try connecting a wire directly from the RX to the negative terminal of your power supply. Or do that with the motor, or both.


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The simplest solution might be to transmit an optical carrier using fixed <10 DEG LED in series aimed in each direction with IR Rx with AGC attached to each camera. Since < 100us sync error is needed at 16kHz or similar carrier f with the desired square wave Vsync at 30, 60, 120, 180 Hz or whatever is used. WIth AGC remote Rx chips having a Q of 10 or ...


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If I was doing this in one off or small volume I'd choose an RF chain that had the most chance of working with the minimum of effort. That would almost certainly have antenna, RF amplifier if used and GPS IC integrated in a module that I connected power and basic signals to. Even trying to implement a reference design with separate antenna + amplifier + GPS ...


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Here is a link to a bunch of AM radio schematics. A common theme is that the loopstick antenna is either a transformer or an autotransformer, tuned to resonate at the desired broadcast frequency by one-half of a dual-gang variable capacitor that also tunes the local oscillator. As above, this covers (in theory), two of the three coils in your image. https:/...


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You can purchase ready-made pre-tinned shields, known as "cake pans". Make sure to get the tinned ones, not the teflon-coated or aluminium ones. Useful for testing low noise stuff. Easy to drill, stick BNCs and feedthrough caps in the edges, etc. Flip the top one, put it on the other, clamp, you get a shielded box. Cookie tins work too, but are ...


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Boost the operating current, if FET. Insert a degeneration EMITTER resistor (or inductor) if bipolar.


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You can't (assuming you're not doing anything wrong with the amplifier so far, like supplying it with a supply voltage that's lower than appropriate). The IP3 is a central limitation of the physics of your amplifier's active components. You'd need a different amplifier.


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How can we show mathematically, for instance, that when the load impedance Zl is equal to Zo then reflection is zero Assume a transmission line of characteristic impedance \$Z_0\$ Assume an applied voltage (\$V_F\$) at one end of the line From the above, the current that flows (\$I_F\$) is \$V_F\$ divided by \$Z_0\$ When the voltage and accompanying ...


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The answer lies in how we convert a wireless signal. The wired signal uses some components to measure if the voltage is above some value to label the signal as HIGH or LOW, and voltage is defined from a common ground. The wireless signal comes out as a wave with a variety of frequencies, but if you've ever seen Galloping Gertie, the Tacoma Narrows bridge, ...


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I'll offer a bit of frame challenge here... The answer to "what is the difference between wired and wireless transmission?" is: there is no significant difference. But that's not the question you're asking 😁 Your question actually is: what's the difference between wired/wireless transmission, and optical transmission. There is no big difference ...


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It's a matter of the frequency components used in the transmission. A "baseband" transmission that has a DC component will need a common reference voltage, because the voltage above the reference carries information. Wireless systems encode data so the DC part of the signal does not carry information, which allows for data to be transmitted across ...


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Requiring a common voltage reference is not a property of all wired communication standards, just those which use voltage levels to encode the information being transmitted. As a counter-example, Ethernet BASE-T is a wired communication standard in which the data is transmitted by currents flowing though the cable, which in turn produce voltage differences ...


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You already worked out for yourself some of the important differences. One that you missed is power handling. The N-type connector can typically handle about 3x the signal power of the SMA without overheating: (Image source: Southwest Microwave) The peak power capability (governed by the dielectric breakdown limit) is similarly higher for N-type compared to ...


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There is no absolute voltage. Like altitude, you can only measure it relative to some reference level. But there is such a thing as absolute amplitude of a wave. You can tell the difference between noisy and quiet, and no reference level is required.


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From the type-N wikipedia page (linked), it's stated that the type-N connector is favored when ruggedness is required. What does this mean specifically? Type N is about 10 times larger than SMA this means it's harder to break. does this mean that the type-N connector has a higher rated number of mating cycles? That would be "durability" not &...


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Wired systems rely on current or voltage to carry signals. These can use a common reference, like early telegraph systems that literally used the earth as a signal return. That’s not strictly necessary though: wired systems can use different means to detect the presence of signal, like detecting edges or sensing a carrier signal. Radios use electromagnetic ...


3

Just to give one common example. Many digital radio systems use a system known as frequency modulation, in which a 0 and a 1 are encoded as slightly different frequencies (the technique is sometimes called shift keying). The broadcast signal is thus a continuous stream modulating regularly (at roughly the data bit rate) between these two frequencies. The ...


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But when we go to wireless communication, how does a receiver interpret the incoming data correctly? I know that electrical signals differ from EM communication. But why and how is a "1" sent is also received as "1" since there is no reference signal. In many RF systems that transmit data there is a reference. For instance, the ...


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I think that they are different because if you inject a signal into port 1 and short port 2 to ground you encounter an impedance of: First, you are not calculating \$Z_0\$ here. \$Z_0\$ is a given of the problem, typically 50 or 75 ohms, but in principle it could be chosen arbitrarily for your system. What you're calculating here is \$Z_{in}\$ the input ...


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Maxwell's equations are chock full of derivatives, which is to say that we only care about change not absolutes. A changing electric field becomes a magnetic one; a changing magnetic field becomes an electric one. An unchanging field does neither of these things. If one of the changing fields hits a wire or coil, we get a signal we can process. Beyond the ...


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It is possible to define S-parameters for networks intended to be used between systems of different impedance, for instance transformers or pads intended to work between 50 Ω and 75 Ω systems. However, when you are asked without further clarification to compute the S-parameters of a network, you should assume it's being used in a 50 Ω system. There may be ...


1

One approach is to forward_bias the diode. Create a series circuit: resistorA, diode, resistor+Capacitor, with top tied to 1.5volts and bottom tied to 1cm square of copper foil (Aluminum foil instantly has an insulating oxide surface, so you cannot get a reliable contact with that foil). If can get a HewlettPackard 5082-2935 diode (100 picosecond reverse ...


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The ISS86 diode has a capacitance of 0.85 pF and, at 5 GHz this is an impedance magnitude of 37.45 Ω making it pretty unsuitable as a diode detector because, in the forward direction, it will rectify (what you want) but, in the reverse direction it will still have high AC conduction due to the 37.45 Ω capacitive reactance. The MMBR941 has an \$f_T\$ of 8 GHz ...


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The manufacturer's documentation was originally wrong. The version you linked says it was from 2013. They have fixed documentation from 2018 on their website here The layout in the current documentation makes much more sense as the signal and ground are no longer shown as being connected: One thing that isn't clear even in the new documentation is that you ...


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The NNTP protocol can sync your R-pi's wall-clock times together and periodically correct for any drift. So at least at the system level there is a solution. However,the R-pi CSI-2 connector specifically lacks any provision for hardware sync or master clock, so that kind of kneecaps the whole scheme. Without frame sync, over time each camera's framing will ...


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IEEE 1588V2 protocol (client and server). It can sync nodes on a network using a master clock. This is a complex software solution (network and services setup, master clock setup etc). GPS - Each node can use a GPS receiver, usually these have 1pps signal. If the nodes are outside, this solution is the simplest (just add a GPS receiver to each PI). If these ...


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This circuit/sensor uses 81pF as the resonant cap. Thus we can have substantial input capacity of the amplifier (several PF) without serious upset to the energy storage and tuning. To avoid dampening, the interface needs to have impedance >> the reactance of 1Henry at 17,000 Hertz, which is about 100,000 ohms. First, lets bias that sensor to VDD/2 ...


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That opamp circuit is DC_blocked. Thus there no control of the VCO frequency. You may need some variant of P_I_D (using 2 or 3 of the components) to control both the center frequency, and control the dampening. I encountered such in the past.


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I'm using a TC2-1TG2 1 to 2 impedance trasnformer. I want to convert a 50 ohm load to 25 but I'm finding that the transformer only works for 50 to 100 If you want to impedance match a 50 ohm source to a 25 ohm load then you need to step down the voltage and not step it up. Try operating the transformer in reverse to how you connected it in your tests i.e. ...


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I am using a MFRC522 RFID reader I have read that it's antenna when in close proximity with metals then interference could be generated. When the coil is close to a conducting surface (i.e. a metal part) eddy currents are induced in the metal and the coil's magnetic field overall becomes reduced. This is because the eddy currents act like mini-shorted-turns ...


1

If the antenna impedance is well matched to my characteristic impedance, can I then simply ignore my pi network, open up the caps, and short the inductor ? Quite often not. Reason: the \$\pi\$ network is also a decent "remover" of high order harmonics and can make the difference between a product that is able to pass certification tests and a ...


2

My question is, when they claim a 1W radio, do they look for a peak of the signal or is it an integration of the entire bandwidth that is 1W. Power is necessarily the integral of all of the output across frequency. A helpful way to think about it, is if you transmitted into a resistor, how much would you heat it up? Some broadband power meters actually ...


1

This answer, regarding metal shields, included math from Richard Feynmann's lectures. He spoke of wire mesh with specific spacings between wires. For the field inside the mesh (aperature in a metal box), the field drops off exponentially: Why are many IR receivers in metal cages? The useful point about this (years old) answer is this you need to place the ...


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The spectrum analyser is making choices for various things like resolution bandwidth, video bandwidth, number of averages, according to an algorithm decided by the people who specified the instrument firmware. This was to optimise their idea of the SNR/time tradeoff in each offset span. You need to force the instrument to make your choice of those things if ...


1

You said the tags are 6 cm apart and I see you are using 13.56 MHz reader. Your antennas are conductive loops and they must be quite near each other. This introduces the possibility of mutual inductance occurring in the setup. Moreover, you are disabling the unused coils by terminating them with 50 Ω resistor to ground. That will allow current to flow in the ...


1

FM can be demodulated for ex. with a filter which converts frequency variations to amplitude variations. Add a rectifier (=crystal detector) and the demodulator is ready. And it's non-coherent because it's not based on mixing with the carrier. Phase modulation can be seen also as FM as you can see if you know the math formulas of FM and PM and understand the ...


5

The phase of a signal is only defined with respect to a reference. If the reference cannot be communicated, then the phase is meaningless. Often when phase modulation is used, it's treated as Differential Phase Modulation. It's not the absolute phase of any symbol that's relevant, it's the change of phase since the last symbol. Of course, as the symbol rate ...


4

First note that the Carlson formula is only an approximation. Second, narrowband FM is defined as FM modulation for which the modulation index is small compared to one. When this is the case, the Carlson formula reduces to the simpler formula and the spectrum of a narrowband FM signal is just the carrier and two sidebands spaced by the modulation frequency. ...


4

I assume that your quantity beta is the maximum momentary frequency offset per the maximum baseband signal frequency fm. That beta is called "modulation index" and it exists in the approximated formula of the needed transmission bandwidth which is the uppermost of your bandwidth formula options. In narrow band FM the modulation index is much ...


1

A compact (roughly measuring 3/4" x 1/2 "), 1 MHz 'canned' crystal oscillator may be used. It's also known as a DIL 14 oscillator, available in 5 V and 3.3 V versions. When plugged into a dual-in-line 14 pin socket, the pin numbering would be 1, 7, 8, 14 instead of 1, 2, 3, 4. A metre long piece of wire could serve as an antenna considering the ...


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Why is transformer coupling used in a simple slope detector? You don't need a transformer for a simple slope detector. This circuit would work providing you select the centre frequency to be one side of the LC tank resonant frequency: - Or maybe this diagram from an Analog devices article: -


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I am still wondering if that is physically possible to make it work for very short distances like in my bench and without the requirement of large and complex antennas A short monopole will work fine if you have a half decent earth. Alternatively, a short dipole will work at either end of the link. At circa 6.8 MHz, the wavelength is about 44 metres and a ...


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