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173 Threads found on edaboard.com: Why Modulation
How to draw the Phasor diagrams of A.M and F.M. what are the reasons for the following two cases (1). In A.M the resultant of the two side band vectors is always in-phase with carrier component ,why? (2). In F.M the resultant side band vector is always in phase-quadrature with carrier component,why?
why did you double the frequency shift specification? +/- 30 kHz sounds more like a reasonable range for 433 MHz band. Anyway, if the DEV input isn't suited to achieve the intended shift, you need to modify the transmitter circuit.
Hi, We all know that more complex modulation leads to higher data rate and PAPR. For example, 256 QAM has higher data rate and PAPR than 64 QAM. But, why ? Would you please tell me which keywords should I google ? Thanks a lot~!
Hi, I am developing a bldc motor controller and is in the starting one of the design file , i have seen the input stages are as follows: supply, emi filter, boost converter, phase shifted full bridge converter, synchronous rectifer and then comes the inverter. My doubt is why cant we directly give the boost converter output to inverter.
why and how does channel length modulation occurring in mosfets decrease the gain of amplifiers?
This code is simply a registered multiplexer of two constants, why is this so hard to figure out or determine if it works (by inspection alone)?
library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.STD_LOGIC_ARITH.ALL; use IEEE.STD_LOGIC_UNSIGNED.ALL; -- Entity Declaration entity bpsk_mod is Port ( clk : in std_logic; -- Processing clock valid_in : in std_logic; -- Input valid signal data_in : in std_logic; -- Input data signal reset : in std_logic; -- Asynchronous reset sig
why does usb transmit data via baseband digital signal, while ethernet has to carry data on modulated analogous signal? I assume you are referring to 1000BASE-T ethernet standard, which is mostly used for wired 1 GBPS links. It doesn't use modulation, but the workload is split over 4 twisted pairs, which are also operated in dupl
LPF out is average of "mod" voltage, not peak. Review the waveform and you'll understand why the output can't be 1 V.
There is a very simple reason for that, changing L changes the device properties significantly while you can increase the W by just putting multiple of these devices together. Also you would probably want to use a shorter channel usually because if you're going for a longer channel length why not just use an older, cheaper process. That is not to
why do you want to make an inverter but you cannot find a transformer for it?
Although it is SSB modulator with LSB output, changing sign in DSP formula will modulate output to upper side band. why are you preceeding well-known signal processing facts with the word "although"? It's exactly as you assume.
Because 0.1nH inductor value is too low for 1GHz, that's why the signal is should be at least 22nH-100nH..
NEVER connect LEDs in parallel unless you match their forward voltage. Pulsed LEDs appear to be dimmed which is why Pulse-Width modulation is used to dim car and bus tail lights. Your eyesight needs an on-time of 30ms or longer to have the same brightness as continuous current. If you pulse with over-current at a low frequency then the long on-
Instead of playing with I and Q signal after demodulation, why don't you think to make an AGC circuit at RF side of this receiver ?? For instance using a RF RSSI IC ( for instance from Analog Device ) will simplify your AGC circuit because these circuits work independent from modulation. I hope I understood your target well a simple cahin (...)
1553 modulation is Biphase , so clock recovery to 0.1% long term is normal, short term depends on Noise and method used, PLL or 1-shot at 3/4T i have no idea why they specify freq error on Biphase , when for Rx, only phase noise and phase margin counts.
why Data transmission at higher rates requires wider bandwidths?
Apart from the technical difficulties of dealing with controlled super high frequencies, and the danger of seeing inside my head (it's a dark, dark place!) you should consider why we use X-ray and gamma rays in existing applications. X-rays are used because they are easily blocked by dense objects, thats how they produce photographs to show our in
1. How do we choose a particular modulation scheme in RF Transceiver (Zigbee uses OQPSK),(Bluetooth LE uses GFSK).why zigbee uses OQPSK and BLE uses GFSK?why not other modulation schemes? 2. Is there any relationship between modulation scheme and path loss?.
Sensitivity is also function of wanted signal-to-noise ratio.You can also say for that as EVM,BER etc. That's why calculation only doesn't make sense mostly depends on the modulation,bit rate which you intend to use. You calculated signal level at the RX antenna and it has little meaning in terms of sensitivity.
1. PFM mode loop is open loop or close loop? 2. Is it required to do Stability Analysis for PFM loop ? If No why ?
Plot of ber vs ebno for qpsk in rayleigh channel using the object rayleighchan changes for each simulation. why does this happen? My code is as follows: % Create Rayleigh fading channel object. chan = rayleighchan(1/10000,0); % Generate data and apply fading channel. M = 4; % QPSK modulation order hMod = modem.pskmod('M', M,'InputTyp
why dont u suggest the buck converter ? Because of non isolation ? I have to get 311VDC for h-bridge of inverter. Not necessarily. You can operate the H-bridge with 350 to 390 V bus supply directly and adjust the modulation for constant output voltage.
Does anyone knows why isolation is needed when using one set of antennas (high gain donor and omni indoor), each other connected by a coax cable acting as passive repeater ? Thanks
Hi, Normally it is mentioned for the polar modulated transmitters, that envelope bandwidth expands due to polar modulation. Can any body tell what is the reason for it and how many times the bandwidth is expanded. regards
hi all i trying to pulse modulation code but i don't know the requirements of this coding plz tell me why are the requirements and how to write the code tell me i am search the some site their is no information abut us
why analog modulation, why 108 MHz? You are not allowed to use the FM broadcast frequency for data or private audio transmission, except for very short distance at ?W power, e.g. to feed your radio with recorded sound.
If all you are interested in is regulating the output power, why do you think you need polar feedback? You can achieve power control with a simple power sensor.
Hi Ashutosh why do you mention three voltage levels? In 16QAM you have 4 possible values for I and the same 4 for Q, giving the 16 possible combinations of the constellation. Regards Z
:???::sad::sad:
... why is lambda normally higher for PMOS than NMOS? David M. Binkley "Tradeoffs and Optimization in Analog CMOS Design" contains a (lengthy) discussion on this: Chap. 3.8.4.1 (pp. 131 ff. in my edition). Lengthy, because channel-length modulation (CLM) cannot easily be separated from other
Is there anyone has experience designing MIMO system for 26 GHz? why we should avoid using technique like VBLAST at 26 GHz? Also, why cross polarization technique is so popular at this frequency?
Hi, IBIS 5.0 has options for accurate power integrity simulation ie., gate modulation. Then why do you need to get the decap values for ur supplies.
Hello, why should many include a LPF AFTER the power amplifier and not BEFORE? It seems to me more suitable to cut any unwanted harmonics before they are amplified. Any ideas?
I have the option to set the following values ​​of my signal generator: carrier frequency, frequency deviation and LF Gen. (R&S SMB100) LF Gen is frequency of the modulation signal but why to I have to set 3 different frequencies? Isn't frequency deviation already defined as the 1/2(fmax-fmin)/fmod and fmax is
please, i did not understand why MSK is considered continuous phase modulation , i need the mathematical explanation of this concept ?
Hello, why noncoherent FSK is bandwidth inefficient in underwater acoustic channels? Thanks
Hi all, I would like to know whether there is any application requiring AM Mixer. From what I learnt about AM Receivers, there is no necessity to shift the RF signal to any IF level as the modulation basically depends on the amplitude modulation and its carried out by the envelope detector stages. In that case
80523 Hi friends. Is there any one who can explain that why over-modulation occurs in space modulation technique?. i think, it is possible to acquire the resultant vector by summing the two adjacent so why over modulation???? Regards
why bother? It is going to have horrible vswr. Put a 3 dB pad on either side of the two filters and you can probably live with it.
Hello, why noncoherent communication is bandwidth inefficient? Thanks
To avoid re-inventig the wheel (or at worst case the square wheel), why don' you use available cheap ASK (OOK) RF modules? 433 MHz can be used license free in many countries. If the solution is too simple, you can still build your own transmitter and receiver with available RF ICs. At least you'll learn much about suitable RF transmission techni
I can't see anything wrong with your code. I tried it, making minor modifications, in Scilab and it seems to me woking properly. I don't know why you said that for low Kp there is no modulation: I can see a modulated spectrum at least down to a Kp of 1. Take into account that armonic content will follows the Bessel "J" function, in fact: Yf
Hello I am doing some experiments with FM modulation. I have an RF generator connected to a function generator and a spectrum analyser. I have been adjusting the modulation index and measuring the amplitudes of the side frequencies. My question is: why is there a discrepancy between my measured side frequency amplitudes and
You can control LED brightness (if it is what you want to) by quickly switching the transistor on and off (PWM modulation). This way the power dissipated in the transistor will be minimum. Anyway, why have you a resistor in the emitter?
That was a rather primitive circuit. A single 100uF decoupling capacitor for V+ may be stable enough to let the circuit oscillate, maybe not, but as minimum add a 100nF ceramic capacitor. This is a very low quality FM modulator. why not use a IC built for this propose? Either a general FM oscillator or a specific for PAL, if it still exist. Can no
why are you doing the FM modulation in Proteus? can't you make it only in matlab? or why don't you use the FFT analyse in Proteus BTW.
what is the use of ifft block in ofdm ? asn: to provide orthogonal between carriers.. and to conver freq to time domain but how can we know ( before ifft block )it is in frequency domain? why can't we use fft block in transmitter and ifft blok in rx? diff bet mapper and modulator??
why that is given for bluetooth?what is the modulation technique using? Answer is here:
why zigbee uses OQPSK modulation,what is the formula for datarate(bit rate) caluculation and why the datarate is 250 Kbps ? what is the difference between single hop and multi hop?