New answers tagged

1

You wouldn't think so, since 433MHz is only designated as ISM in Region 1, but there are some regulations that appear to allow a manually operated transmitter that stops transmission within 5 seconds of release of the button (or automatic transmit with bursts of < 5 seconds). (machine translation) (4.1.1) Operators operating at 314-316MHZ and 433-435MHZ:...


0

I don't believe anything is wrong with your transmission line. I think the periodic oscillations in transfer function is due to capacitive irregularities at the ends of your transmission line, they form a tank circuit. Is it possible that my pads (passives along the RF trace) and SMD pad of the GNSS module are indeed acting as a capacitor? Should I void the ...


0

If you're looking for a ready-made product, have a look at LoRa and RFM69 (You can find dev kits from Adafruit and SparkFun for instance). In Europe there is also another standard called Wize (dev kits) which builds upon Wireless M-Bus.


2

Results from a trace width calculator I use: Using Er = 4.8 (I normally use 4.2 since we use Isola 370HR) Gap between trace and upper ground plane = 6 mils, as used in Figure 5.1 Z = 50 ohms Trace width = 30 mils (36 mils for Er = 4.2) which closely matches with Figure 5.1. With a gap between trace and upper ground plane = 60 mils, the trace width is 100 ...


5

This is a very typical result that basically means you got a garbage output, because something overflowed in the filter synthesis computations, or there was catastrophic loss of precision, or some iterative algorithm failed to converge. Typically, when you start to write filter design software, you'll get such "results". The general idea is to ...


1

I think this is correct. The attached graphic is a GNURadio Frequency Sink for 103.5 WEZL, Charleston SC. This station is an HD station. The bandwidth of an FM station is specified as 200 kHz. Note the main signal clearly shows 200 kHz from 103.4 - 103.6. There are also sidebands that are about 100 kHz each at 103 - 104 and 106 - 107. This violates ...


3

Yes, there are these writings of Andrew Zonenberg, where he measures different configurations of adjacent breadboard columns. The real kicker is this figure: At 200 MHz, already 10% of the energy put into the field around one line can be extracted with its neighbor.


1

I made a bit of research and to be considered as a transmission line you would need at least Lambda/10. This is at this point that we consider that along the line you don't have the same voltage. This is also true for power lines! This at your frequency give a length of at least 6.7cm which you are well below.


2

If you use Saturn’s PCB software to choose a transmission line so it raises track temp. Say a 20’C rise above ambient by thickness and width for the impedance you want with coplanar gnd a track and a ground plane for low emissions reflected into an open circuit with impedances matched by electrical test. Then design a track for -40dB crosstalk, you have a ...


1

This is an excellent question that I have not had to consider for many decades so my answer is what I know. Some may be shocked that the ideal part is an $800 door-knob porcelain cap with gold-plated electrodes over palladium. Here are my rules of thumb for dielectrics for RF high power 1210 ~1/4W derate 50% or more if ESR>=50m and derate voltage 50% if ...


1

To answer your question, you will need to (a) simulate the filter with an EM simulator, to see where the currents in the copper are largest (often at the corners of the traces) or better yet (b) build the filter and measure the temperature rise when it’s used at high power. A multi physics type of simulation would find the current maximums and estimate the ...


0

A responsivity of 0.8 A/W is required. Is it only a property of the photodiode or does it depend also on the surrounding circuitry? Property of the photodiode. For a conventional photodiode each photon gives you one electron, but since shorter wavelength photons are more energic you get fewer per watt. In addition photodiodes aren't 100% efficient, ...


0

The 20 Ohm input resistance of your "transimpedance" amplifier is likely needed for stability. A photodiode may have too much capacitance to hook to the inverting input of your op-amp. It is double trouble if the photocell leads are long making a tuned circuit you don't want. You will likely need a small resistance in that path at least for ...


1

OTA’s are used to amplify current sources and the feedback R is the input resistance. The output resistance rises to the open loop Rs of any negative feedback amplifier as the gain reduces to u it’s at max GBW product thus a 50 ohm driver is a special consideration for video amps with high gain at 50 MHz and largely determined by the collector R. As you may ...


2

Where is the tank circuit? Which capacitors are participating? In AC signal analysis the DC supply appears as a short circuit, so you can imagine the positive supply rail as being connected to ground. The tank appears here: The coupling capacitor (the unlabeled one) should have a relatively large capacitance compared to C1, C2 and Cvar. The capacitance of ...


1

Your question is not clear. However if you designate an antenna at a certain frequency (2.45 GHz and 900 MHz), it is assumed these antennas are resonate at those frequencies. That means they are designed to be most efficient at those frequencies. Thus if you transmit at 2.45 GHz, the 900 MHz antenna will receive thoses signals but output a much lower level ...


0

I'm curious about the design of RF transformers with purposely designed non-unity coupling coefficient. If you are looking for some degree of precision in the value of k then use near-unity coupling transformers and use an external shielded inductor to create the uncoupled inductance you require. For example, if I made two air core inductors and placed ...


1

For example, if I made two air core inductors and placed them axially aligned in close proximity, what kind of ranges of coupling coefficient could I hope to achieve? And importantly, how accurate could I get that coupling coefficient to be? Way back in my early engineering days, we needed to implement a 50 MHz and a 500 MHz bandpass filter, with very good ...


3

Is it possible to measure the distance between two devices by using RF signal strength if the devices have no obstructions between them? If so then can 2 or 3 be used to get distance and direction? It is theoretically possible to measure distance between two devices using the signal strength of an RF signal. However, that is not a common approach, and it is ...


0

You can use coaxial cables, along with attenuators, power combiner/splitters and directional couplers. You can do it on a PCB, but the solution will be quite big and signals from different transceivers will couple to each other, unless you have a strict RX/TX scheduling. A better solution would be optical transceivers + fiber, even for short runs inside an ...


0

It would only be a problem if copper is touching copper (and if you run a Design Rule Check (DRC) then it will make sure that copper doesn't touch (unless it's the same net name, in that case you intended it to connect) The solder paste layer does extend to far beyond the footprints (unless you intended to do that), you may have issues manufacturing an ...


2

The most common approach is to design your microstrip or CPWG to match the component pads for devices in the path. For 0402 components, that means 20 mil trace, as you mentioned. And, yes, this means generally using all 0402 components for that RF path. If you use narrower trace (12 mil) with 20 mil pads, you will have unwanted parasitic capacitance at ...


2

Yes, the surfaces of a shield cannot be left floating and must be connected to ground with as much of a geometrically continuous connection as possible for lowest impedance.


2

Steering any array off bore-sight induces scan loss, or a loss in directivity. In the image you posted with the multiple beams, that graph is normalizing the patterns, hence why they all peak at 0 dB. With relative normalization against the unsteered array, the loss in directivity would be evident. It does however show the main beam broadening, which is a ...


1

The term "range gate/gating" can mean different things depending on the context and the radar system being talked about. In general, a "range gate" is a window in range observed for some purpose, mainly for detecting and tracking targets in a radar system. In legacy radar systems, analog circuits were used to define a time window (which ...


2

These sheets are made of a loss material – it has a \$\mu_r=\mu'+j\mu''\$ whose imaginary part is particularly high. Reflections happen when the boundary conditions enforce that – for example, a metal surface reflects well, because there can't be (much) E-Field inside the metal, leading to equation describing an incident wave having a solution where the ...


1

In these kinds of systems, "antenna" is a bit of a misnomer: instead, consider the two coils of the reader and the tag as primary and secondary windings of a transformer. A simple measurement on how much power can be pushed through the transformer allows the reader to determine the "short-circuit-ness" of the tag side, to stay within your ...


2

Is such a power limiter realized with an attenuator Usually no, as an attenuator would attenuate all signals so that means your receiver would become less sensitive. You actually want a "smart" attenuator that doesn't attenuate small signals but that does attenuate large signals. Note that the large (harmfull) signals aren't the ones that you're ...


1

A real sinusoid \$x(t) = \cos{(\omega t + \phi)}\$, when viewed in the frequency domain through a Fourier transform, consists of two complex sinusoids: one at positive frequency, and one at negative frequency: $$ x(t) = \frac{1}{2} e^{j \omega t + \phi} + \frac{1}{2} e^{-j \omega t + \phi} $$ The imaginary components of these two terms cancel out and the ...


3

Array factor does not show scan loss. Array factor is merely a multiplier. It's actually a common mistake for engineers to use the array factor as a gain value. Array factor gain does not change with scan angle or element spacing! To see scan loss, you need to calculate the directivity. However, for a uniform linear array (ULA) of isotropic elements you will ...


0

In order to track an object in 3D space, azimuth, elevation and range must be translated from 3 antenna with time and mobile spacial fixed reference. It is synchronous to rev/sec stored in integer relative time with 12bit counters and position rotated by the phase shift of the reflected pulse relative to each rotor angle to triangulate position and compute ...


1

I doubt it is processing power limitation since during the search mode the whole beam is processed. Hm the figures suggests you have a scanning beam: the radar can't observe the whole sky at once. So, until anything happens, you scan (as in: focus the beam at a spot, wait for the farthest sensible reflect, then you look at the next spot) the part of the sky ...


3

Range gate gives to the direction tracking process the timing "compare the monopulse beams now". Servo tracking range gate can drift away if there's a strong artificial echo which is timed to give at first a plausible "it's on the peak" indication and slowly moved away. Clever anti-jam systems and also an experienced radar operator can ...


Top 50 recent answers are included