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76 Threads found on Carrier Frequency Offset
What's CFO(carrier frequency offset)? What mean? Why use it?
Hello I am new to this forum and new to OFDM Can some body explain the mechansims that cause carrier Freq. offset... i keep reading unmatched local osc. at TX and RX. but what OSC? the carriers are generated by IFFT/FFT there is no physical OSC. THere are RF and IF osc. which also can cause but not the main concern... Doppler can (...)
I find that in some algorithm the received signal(atfer matched filter) is expressed as: r(t)=∑Sk*exp{j*(Δωt+Θ)}*g(t-kT-τ)+n(t) 2 questions: 1, why is Sk a complex array? If so, it will impact the angle of correlation of r(n)(sampled) and the final offset not only contain the carrier frequency (...)
Did you mean where frequency offset is more than 1/2 of the carrier spacing in the preamble?
it means that @10 KHz offset we measure the phase noise at carrier frequency plus (+) or minuse (-) 10khz? is it truse?
ok fine but what about carrier recovery?
I can't understand your code, and maybe I am wrong but it is probably the code is completely wrong. At least there should be a modulation signal such as random bit sequence. And then the bit sequence is modulated with QPSK format on a carrier. Then the frequency offset should be added to the carrier. You can assume the (...)
Hi, I am trying an algorithm for CFO cancellation. I would like to know how well the algorithm performs with respect to the CFO required for commercial systems. Unfortunately, after googling a lot (web+scholar) I could not find any proper table/list/article that defines what is the allowed CFO in relevant applications. I believe there sho
Hi all, I'm implementing STBC-MIMO and MIMO-OFDM system using SDRs. Before doing actual coding, I'm working on MATLAB simulation of CFO estimation and recovery and channel estimation. I'm reading some Dr. Giannakis' papers about joint CFO and channel estimation. Besides Dr. G, I know that many people have researched joint CFO and channel es
Hi greeting.. At digital receiver, carrier frequency offsets cause rotating constellation plot. Can someone explain me how this is visualized in mathematical equation. :) PN
The following code is used to estimate and correct the frequency offset errors for a single carrier system %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% freqoffset = 0; phaseoffset = 0; hPFO = comm.Phasefrequencyoffset('frequencyoffset', (...)
Hi Esourour! FCCH appears only once in a while - GSM specs will tell you how often. Please, consider if that is often enough to do estimation. If FCCH occurs not often enough then you should do what your collegue offered - go for midamble in every burst. While FCCH is purely sinusoidal, midambles are not due to GMSK modulation. Midambles a
analog AFC circuits are designed for a single carrier modulation. It changes the tuning of the receiver so that the mean/median peak of the power spectrum is in the center of the IF stages. There may be more sophisticated DSP methods of doing this.
if the upconversion mixer have a feed through then the output of the mixer will have the carrier frequency un modulated , then in reciver this component will appear as DC offset but this may not ahppen coz the TX freq is different fromRX and that's why there is duplexer at the anteena khouly
Say there are spurs 1 MHz from the carrier, on either side, that are -30 dBc. Think of them as phase modulation sidebands, with a modulation frequency of 1 MHz. If you divide by 2 the carrier frequency halves, the modulation frequency of 1 MHz does not change, but the phase deviation does (gets smaller), (...)
Hi, Are you able to acquire the signal with the modulation? What is happening to the carrier during acquisition. BR M
Phase noise is measured as dBc/Hz. dBc stands for dB per carrier i.e measured noise power with respect to the carrier power. Phase noise takes a skirt like shape with noise being higher closer to the carrier. The offset frequency is the difference in frequency between the (...)
I need this thesis very very urgent I search alot to find link for downloading I coldn't find but,I have all it's detail name: carrier frequency offset ESTIMATION IN MIMO OFDM SYSTEMS A DISSERTATION Submitted in partial fulfillment of the requirements for the award of the degree of MASTER OF TECHNOLOGY in ELECTRONICS AND (...)
Hi guys, I have this question, I know in OFDM system, when you upconvert the signal with certain carrier frequency with certain sampling frequency and when you downconvert it, if the carrier frequency is same, but the sampling is not, then you will have a sampling frequency (...)
In Zero-IF receivers after mixing the LO with the incoming signal the carrier would appear as a DC offset. If the LOs are slightly offset, due to crystal tolerances, there appears to be a large signal near zero, at a couple of kHz. Is this signal just filtered out with a high-pass filter? Is this phenomena still considered to be a DC (...)
I need to know why the phase noise of oscillators are generally seen at 100 Hz offset from the carrier ? is there any reason for the measurement at this frequency offset in RADAR application?:?:
Hello all, I've a GFSK modem. Packets begin with a preamble of alternating zeros and ones. The first stage is frequency offset estimation(FOE) that counts the no of zero crossings(ZC's) within a certain window (16 bits for example)then estimates the carrier freq offset. I've added a code, within the FOE algorithm, to (...)
I am not sure about the practical chips of FFT/IFFT, but as far as the MATLAB is concerned you can use FFT/IFFT of any size, but it is most efficient in terms of computation when the number of subcarriers is in the form of 2^x. If you have an FFT/IFFT of size 128 and you only need to transmit 72 subcarriers, then you will need to nul
to point to the drip rf is a circle like a plop but ssb is a plop plipp { the plipp being the next circle out like mushrooms grow but at the frq in circles at your antenna {dipole} radiation pattern is ssb the plipp of the plop without the plop{the plop is filtered out s
Paper with some algorithms carrier synchronization of offset QPSK, J. B. Berner,; P. W. Kinman, 2002 IEEE Aerospace Conference , March 9, 2002 :)
Hi,Willem How is your vco's phase noise perfomances at the offset frequency of 100kHz and 1MHz from the carrier frequency? thanks.
Amplitude Modulation Source Function The general syntax for including a single-frequency, frequency-modulated source in an independent voltage or current source is: Syntax Vxxx n+ n- AM < (> sa oc fm fc <)> or Ixxx n+ n- AM < (> sa oc fm fc <)> The arguments are: Vxxx, Ixxx Independent voltage source, which exhibits the amplitudem
Hi If you use low IF, you will need only one ADC. If you use zero IF, and your modulation scheme is like an FSK which signal spectrum is not symmetric around carrier, you should use two ADCs and I/Q downconversion. Regards
Hi all, Is it correct to say that by divided the VCO frequency by a N divider, the VCO phase noise a frequency offset N*f from the carrier will become the Phase noise of the signal after division at a frequency offset f (N*f/N) from the carrier? Thanks for your explanations.
what is meant by the following terms : 1- channel eqaulization 2- carrier offset frequency thanks chanel equalization means compensating the system response with the intent to get a satisfatory response for interested bands, for example, get linear phase response for different frequency carrier (...)
For a VCO I measured in lab -30dBrad?/Hz of phase noise. Most of the examples I've seen express the phase noise in units of dBc/Hz, which I understand is the ratio of noise with respect of the carrier at a frequency offset. What does rad?/Hz mean ?? regards !
In the base band you need to add a dc which will turnout as carrier leakage. Is this what you are looking for. Madhukar
Hello Frnds!!! i have a deep doubt related to DC subcarrier. i.e. As per Wimax802.16d PDF: "DC subcarrier is the subcarrier whose frequency is equal to the RF centre frequency of the transmitting station." what is the significance of "RF centre frequency of the transmitting station." (...)
The carrier recovery is achieved together with timing recovery in DSSS. The reason is the SNR in DSSS is quite low, which makes the carrier recovery loop difficult to get a correct results
Seems to me that the PLL loop is not locked. If locked you should see a pure sinewave carrier. For measuring phase noise: * Use the phase noise module if the spectrum analyzer has one * Use noise measurement at 10/100 kHz offset with the VCO locked
Well, imagine a carrier with some sort of small frequency modulation going on. If there is a single tone at frequency Fm modulating the carrier, the spectrum can be approximated by: sideband power in dbc = 20 Log (Δf/(2* Fm)) where Δf is the frequency deviation, and Fm is the modulating (...)
When you design an amplifier for low noise figure, you are designing it so that the TOTAL added noise power of the amplfier is low. You integrate over a wide frequency range, say 1 Hz to 20 MHz offset from the carrier, and the total integrated noise power yields your amplifier noise figure. When you design a low phase noise amplifier, (...)
Send known data, find the amount of rotation, from this find the frequency offset. Then, for subsequent unknown data, multiply this frequency with the with incoming carrier and filter our unwanted frequency. Thus you rotate is back to correct value - b
Hello, Phase noise is often expressed as the noise density, PSD , referenced to the carrier power at a certain frequency offset from the carrier. Phase noise, Side band noise = (PSD (at offset) ) / (carrier power) When you convert this to decibels, you get dBc/Hz. The "c" (...)
Hi KericWard I had the 2nd edition in mind. I just checked the 2nd and 3rd edition and they are quite different in several aspects. Gardner says in the preface of 3rd ed.: Several parts of the second edition have been omitted: the chapters on optimization and synchronization, and the mathematical appendix. ... Synchronization (recovery of carr
hi, i'm doing a comprfassion between ofdm and cdma. doppler spread destroy the orthogonality between the sub carriers in OFDM and cause ICI. but i cant figure if and how doppler spread effects CDMA (not MC CDMA but DS CDMA) i mean, every user spread its information with PN code on all the BW can somone explein how and why is it effects\dosen
To know the lower integration frequency, you would want to know something about the way the communications system works. Lets say it is a 64 QAM system that has a carrier tracking loop in the receiver. Such a system has a carrier tracking loop. Lets say you are sending 10 Mbps of data, and the carrier tracking control (...)
DCRs use a method of phase locking the local oscillator to the received carrier in order to properly process AM and FM. It is necessary to eliminate frequency drift. The output of the mixer is then the demodulated signal. It might need a lot of audio amplification if the signal level is low (due to lack of AGC and the need to tolerate strong signal
Hi I would really appreciate it if someone could help me. (Sort out some confusion :-)) I am intending to use the 74hc4046 to demodulate a FSK signal. The carrier centre frequency is around 165Khz and the deviation is around +/-2.5%. So I am using a frequency offset. (I am not using any frequency (...)
I guess Fant has probably presentetd the best way of acheiving lowest phase noise! You said that you had HP10811 on hand and this is a sc-cut ovencontrolled oscillator which used to be THE standard which everyone else did compare to. I am not sure what the phase noise is at 10 Hz offset but I would guess -130 to -135 dBc/Hz. Ulrich Rohde shows
In general you are using a double side band modulator to get your low frequency (or DC) input signal higher in frequency so it can be amplified as an AC signal. This way you are out of the 1/f noise region of the amplifier and the DC offset and drift of the amplifier does not come into play. At the output of the amplifier you synchronously (...)
If your VCO is frequency modulated, how you will be able to measure PN ?? It's impossible !! PN is essentially frequency/phase modulation with noise and how you will extract this deviation from main modulation?? I mean, when you make a frequency/phase modulation, how will you define this noise modulated signal?? The way of measurement of (...)
This is my intuitive approach: An instantaneous change in Phase produces a change in frequency and viceversa. If the modulating signal is varying the PM or FM signals are the same. The only diferences are probably with DC or DC level. In FM a DC level will shift the carrier to another frequency. In PM a DC level will not change the freq. (...)
Hi Professional, I remember that Phase noise which often refer to CW carrier for GSM TXVCO can be used to calculate GSM modulated power for certain offset to (desired channel) frequency. It means that if I want to get TXVCO PN requirement by the clue of modulation spectrum of GSM @ 400KHz offset, which is -60dBc, then, (...)