# Tag Info

37

In short: receiving is much more complicated than transmission. You'll notice that whatever you measure in the real world is overlaid with noise. The problem "seeing all this noise with a bit of signal in it, how do I know what the transmitter meant to transmit" is the central problem that communications engineering tries to solve. So, to receive a ...

17

Well, first off, you're looking at a microcontroller. The datasheet also says it will draw 3.4mA without any radios on, so you can only attribute 3.5mA to radio reception. And then, if you look at the block diagram, you find this: That's right, a software-defined radio with its own ARM core. This allows, as TI says, an awful lot of future-proofing; they can ...

8

However, it's not clear to me why would the generated sine wave need to be with similarly high amplitude in the case of reception, compared with the case of transmission. The thing is, it's not a high amplitude. 0 dBm of transmit power is 1 milliwatt and a power of 1 milliwatt into 50 ohms is 224 mV RMS i.e. a small voltage but, a voltage that is also about ...

6

They weren't originally designed for it, but I have seen applications that use bidirectional radio chips such as the TI CC1101 to pass control/status data in both directions through a coax alongside DC power and another RF signal. The chip handles a lot of the details and is relatively easy to set up with a microcontroller. In fact, in one design, a very ...

5

TL;DR - The cable won't have any affect on the measurement if you take the measurement properly. If you have a VNA, you should be calibrating it before taking a measurement. Typically done with a SOLT (Short, Open, Load, Thru) calibration kit for coaxial cables (and just SOL for a 1-port measurement). The VNA measures the response of the standards in the ...

3

The LM386 is an IC. The triangle is just a symbol use on a schematic diagram to represent the IC. If you consult the manufacturer's datasheet for the LM386, you should find a full description and schematic of the internal circuit, and also a description of the physical package of the part, with the dimensions and pin locations.

3

You seem to be plotting the direct voltage output, but that's not how they're describing it. What they defined is a voltage sensitivity, which they give as ($f$ in GHz): $$\gamma_1=\frac{0.52}{I_S(1+\omega^2C_j^2R_SR_V)}\xrightarrow{C_j=0.1p, R_S=50,R_V=\frac{0.026}{I_S}}\frac{10^3}{f^2+2\cdot 10^6I_S}$$ Here there is a datasheet for HSPS8101 where, at ...

3

So, sounds like a bandpass filter, followed by a power detector. Detection can be as easy as a diode rectifier followed by a simple RC lowpass. Feed that into a transistor as switch. Amplification might be necessary at some step. Sorry that it's not more specific than that, but you probably know that in RF engineering, things very much depend on the actual ...

3

You're using an S-parameter model. An S-parameter model is a small signal model of a device and is only valid within a certain frequency range. Also this S-parameter model might be valid only for a certain biasing condition (this is indeed the case here). That frequency range generally does not include DC (0 Hz) so you cannot and should not expect that an S-...

3

Signal reliability may be improved either by putting more power into the transmission, or putting more effort into extracting a signal from the "noise" (unwanted nearby signals). The reason the receivers for these little radios need more power than the transmitters is that the transmitter power is restricted by emissions regulations. One could ...

3

Array antennas are the basis for beam forming. With array antennas, you can control the directivity by driving each antenna of the array with a different phase.

3

MY vna is 50 ohm source impedance, what values and which type of network would you use? First convert 4 - j22 to a parallel capacitor and resistor (8.258 pF and 125 ohms) Try this calculator. Assume an LC pad to will match 50 ohm to 125 ohm (may need a slight mod) Recognize that the LC pad needs too little capacitance compared to 8.258 pF Resonate out most ...

2

WiFi channel 0 and channel 4 overlap slightly so interference is theoretically possible. Channel 1, 6 and 11 are the only channel that can be used interference free from one another (you can look at this picture from Wikipedia). That said, there are many other possible causes of interference e.g. Bluetooth, Microwaves usw. or the AP might just be to far away....

2

The module you talk about has a supply voltage of 5 volts It has a maximum output power of 100 mW That's 2.24 volts RMS into a 50 ohm load That's 6.32 volts p-p That sounds about right for a class C output driver running on 5 volts The problem isn't the addition of gains (dB) but the module running out of ability to produce more power on its output ...

2

I'd consider using one of these: -

1

I did only a rough calculation, but assuming a 50 ohm driver and load, you will lose about 5% of signal power due to reflection.

1

If you insist on using RF, you might get some joy from super-regenerative receiver circuits. These normally pulse at supersonic frequencies. Circuit time constants could be slowed to pulse-per-second. Very simple circuit having just a few transistors Low power drain from a few battery cell Super-regen circuits are both transmitter and receiver combined. ...

1

Here is my question, given that the source is 50 ohm terminated, will the amplitude that I measure at the scope depend on the length of the cable? ... It seems to me that the first signal will hit the scope and then reflect and this will cause the signal to double relative to the 50 ohm terminated case. however, the reflected signal travels back to the ...

1

Pin Diodes work well up into the GHz range as switches or harmonic devices from subharmonic pulses rich with harmonics. So I don’t see the diode being a limitation. The pulse width must be less than the period to contain as much energy as possible.

1

The schematic contains the PIN diode approx. DC model, there are no high frequency components on it. The 2mA from the -400V can be set by R3. The 200mA PIN diode forward current is set by R1. DC Transfer Characteristic: The switching times are set by L1. If the 5V isn't enough to PIN diode forward current, the power supply voltage of U1 can be increased ...

1

First off PC's emit a large amount of EMI, even with the case properly grounded they can cause AM radio signals to be completely 'drowned out'. A PC has multiple clocks and DC DC converters with very large switching currents and emits radiation. If your a 'nice' person you'll use a properly grounded case that is made of metal or other shielding material. If ...

1

If we can increase the directivity of the single element antenna by increasing its electrical size then why do we need array antennas? Increasing the size of a single element means it will certainly receive unwanted lower frequencies and this might make the electronics more complex. It also means that the impedance of the antenna at the "wanted" ...

1

frequency devision multiplexing: With consumer satellite hardware signalling is done using voltage modulation and 22 kHz tone bursts if the data rate is low I'd send the signal up the line by modulating the supply voltage (eg switching between 13V and 15V ) and signal back down using 22kHz bursts. Are there existing components or ICs to facilitate such a ...

1

How would you combine DC power, bi-directional serial data, and an RF signal on a $\color{red}{\text{single}}$ 50-Ohm coax feed-line? Let's not forget what the question says regards cables: - $$\color{red}{\boxed{\text{the single coax feed-line}}}$$ Regular UART level serial data comms would interfere with RF reception but you could certainly modulate ...

1

Impedance and frequency, other are not relevant. Gain is possible with directed antenna or with antenna that has shaped radiation pattern. You should first elaborate what radiation pattern you would like. Example of omnidirectional antenna pattern:

1

Put on the solder mask. Metal being directly exposed only brings heartburn. Soldermask (unless made of some weird material) generally has very little effect on 2.4GHz RF. You're likely to have much worse loss from that far-too-simple matching network. Note that the (old?) Nordic RF beacons (also round) put soldermask over their antennas (which were just a ...

1

I use paste solder, a SMD rework hot air gun with a small nozzle and a soldering iron to solder center pins in coax connectors (for connectors that do not allow crimping). Fill the pin with paste, apply extra to the wire near the pin, heat up the pin and conductor, then hit the conductor (not the pin) with a hot iron and some additional solder to complete ...

1

I wanted to create a circuit, Um, no. What you describe encompasses at least one relatively beefy computer that has a network interface and runs an operating system with a network stack. What kind of things should I start to learn and where. Honestly, "recognizing things you can and cannot build with your current resources" is what you should ...

1

The inductor needs to block 10MHz and 950-2150Mhz. To "block" them you want the impedance of the inductor to be much larger than the impedance of the line it T's the DC into. If the line is 50 ohms then you want an inductor of > 500 ohms. Use ZL = 2 x Pi x Freq x L = 500 Ohms At 10MHz, ~8uH is 500 Ohms At 950Mhz, ~84nH is 500 Ohms At 2150MHz, ~...

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