I have N number of time-domain complex signals. And I want to find the corresponding power spectral density of these signals. The usual way...

I have N number of time-domain complex signals. And I want to find the corresponding power spectral density of these signals. The usual way I think is to find the autocorrelation of the signals. Then, the fourier transform of it. My question is, how do I find the power spectral density of complex signals? Autocorrelation of complex signals? Autocorrelation of the magnitude of the complex signals? ...

Hi all, I'm planning to use Gold Codes in a DSSS Modem. The question is: The input data is complex but a gold code is not complex....

Hi all, I'm planning to use Gold Codes in a DSSS Modem. The question is: The input data is complex but a gold code is not complex. When spreading the complex data, do you simply set the imag part of the gold code to 0 and do a complex multiplication with the complex input data and again the same when despreading the data? Thanks for any suggestions, Jaco

I have a data set that is complex that i generated by using a hilbert transform. I wanted to add guassian noise (complex) to the data and then...

I have a data set that is complex that i generated by using a hilbert transform. I wanted to add guassian noise (complex) to the data and then do some processing. When i do this, is the correct method to add the hilbert tranform of the data to the hilbert transform of the noise? Or do i use a 'different' noise sequence and create complex additive noise to keep the I and Q of the noise uncorrela...

Hi all, I have a signal a+jb generated inside DSP. Now, I want to feed the signal to a quadrature modulator, upconvert it to 100MHz and measure...

Hi all, I have a signal a+jb generated inside DSP. Now, I want to feed the signal to a quadrature modulator, upconvert it to 100MHz and measure it with a spectrum analyzer or scope. My question is, the signal a+jb is complex, the quadrature upconversion is also complex, exp(j*2*pi*100e6). Will I see the complex signal, (a+jb)*exp(j*2*pi*100e6) on the spectrum? Also, for the complex sign...

when doing subband, you get the signal in complex value, and you do lms in complex value, when you reconstruct the complex e back to full-band...

when doing subband, you get the signal in complex value, and you do lms in complex value, when you reconstruct the complex e back to full-band e, how will you get real value back? or just take magnitude? Lee

OK, I understand that when you do an FFT on an array of real values you get an array of complex numbers. Where each complex number represents a...

OK, I understand that when you do an FFT on an array of real values you get an array of complex numbers. Where each complex number represents a frequency wave (sine), the magnitude representing amplitude of the wave and the argument (angle) representing the phase. But when you do an IFFT, what does a complex number represent in the output array? When you are working with IFFTs an

Sirs, I would like to get a clarification on expressing cosine using complex exponentials ... It is given in texts that A * cos (pi) = A/2 *...

Sirs, I would like to get a clarification on expressing cosine using complex exponentials ... It is given in texts that A * cos (pi) = A/2 * exp pow j * A/2 * pi + exp pow -(j * pi) When I plot the above two complex exponentials, I get 2 points on the complex plane but how these correspond to a single point of cosine signal, I am unable to get. And, how thesd eventually give a cosine sign...

I have implemented the basic overlap-add convolution using a standard complex FFT routine. This has lots of zeroes, first from padding data and...

I have implemented the basic overlap-add convolution using a standard complex FFT routine. This has lots of zeroes, first from padding data and IR (impulse response) to FFT size, then I have to copy data and IR to complex numbers (with zero imaginary part). Now I tried instead to replace the complex FFT routine with a real-valued FFT so I can skip copying all data and IR to complex numbers. ...

Sirs, I have few questions wrt to complex numbers. 1) I would like to know the main purpose of using complex numbers. 2) I would like to...

Sirs, I have few questions wrt to complex numbers. 1) I would like to know the main purpose of using complex numbers. 2) I would like to know given a number in complex notation, is it possible to convert this into a real number. Thanks, Manish

Hi forum, I have a complex input FFT core implementation for FPGA. Now I want redesign the core to reduce the logic for real input...

Hi forum, I have a complex input FFT core implementation for FPGA. Now I want redesign the core to reduce the logic for real input sequences. I use SDF (single delay feedback) architecture. Output is 1 complex sample per clock. The standard 2N real FFT with N complex FFT doesn't work for me. The difference between 2N and N point FFTs is only one butterfly stage (one complex multiplication a...

I repeatedly come across objections to using complex numbers for DSP. I wonder if there is a good way that I can explain without...

I repeatedly come across objections to using complex numbers for DSP. I wonder if there is a good way that I can explain without struggling? The current case concerns ultrasound, where the measurement is of pressure (on a transducer). My processing uses complex numbers, which naturally arise when I demodulate the signal. The question I am asked is, why are complex numbers necessary when the...

Dear All, I have a question about processing of complex signal in demodulating spread spectrum signals. I have a signal that is spread using a...

Dear All, I have a question about processing of complex signal in demodulating spread spectrum signals. I have a signal that is spread using a PN sequence. This received signal is at baseband and is complex i.e. The received samples are in complex format at baseband. I want to multiply this received signal at baseband the PN sequence so as to strip the modulated signal of the PN sequence. How can...

Greetings, I'm looking for a quick way to computing complex phase rotation in fixed-point, basically for a given complex number X and phase...

Greetings, I'm looking for a quick way to computing complex phase rotation in fixed-point, basically for a given complex number X and phase theta, I'd like to compute: Y = X exp(j theta). I know that I can use CORDIC to first find Z = exp(j theta), and then do a complex multiply, but I'm hoping for a shortcut given that I am only rotating, and not scaling. If it makes a differe...

Dear All, I have a question regarding hilbert transformer. If i take the bandpass signal and sample it it would be real. Now when i multiply...

Dear All, I have a question regarding hilbert transformer. If i take the bandpass signal and sample it it would be real. Now when i multiply it with a complex exponential to downconvert it I get a complex baseband signal. On the other hand, if i take the bandpass signal, pass it through a hilbert transformer and get a complex signal, and then downconvert using complex multiplication i get di...

Hello I need to invert square complex matrixes of sizes 52x52,64x64 and 128x128 in MS VC++6.I need to implement it as fast as possible....

Hello I need to invert square complex matrixes of sizes 52x52,64x64 and 128x128 in MS VC++6.I need to implement it as fast as possible. I have written a code for complex matrix inversion but it takes lot of time. (e.g. a complex matrix inversion of 52x52 matrix takes more than 2ms) Can any one tell me free intel library or any other related library to do my task more fastly? ...

Hi, I am digitizing an analog signal. Now I have real samples of the analog signal. I need to calculate the power of the signal with...

Hi, I am digitizing an analog signal. Now I have real samples of the analog signal. I need to calculate the power of the signal with these samples. Is this possible to calculate the power of the signal? Does it need complex samples to calculate? If complex samples are needed to calcuate the signal power How can I get complex samples from the real samples?

Hi all, What is the significance of complex FIR filters used? In general the inputs are the sequences of real values, then where can the...

Hi all, What is the significance of complex FIR filters used? In general the inputs are the sequences of real values, then where can the complex filters be used? If they are used for real inputs, then how do we interpret the complex outputs? Regards, Ishtiaq.

Hello DSPers, After reading the thread about "Why cplex filters" a question comes to mind: how to generate complex filter coefficients if i do...

Hello DSPers, After reading the thread about "Why cplex filters" a question comes to mind: how to generate complex filter coefficients if i do not wish to apply desired phase and amplitude correction to the original signal? I've passed the initial real signal through a Hilber Transformer, and have thus a complex analytic signal. I'm using a Blackfin DSP, and it has a complex fir function, as...

Hello: I'm trying to figure out how best to convert a complex signal to a real. I've heard of one approach that says to take the magnitude...

Hello: I'm trying to figure out how best to convert a complex signal to a real. I've heard of one approach that says to take the magnitude of the complex sample and use that as the real sample. And another approach where you just drop the imaginary part. Are there other techniques? If I'm looking to convert the complex signal to an audio format, is one approach better than the other?...

Hi, I have begun a complex number tutorial which shows how e^jwt works. It is...

Hi, I have begun a complex number tutorial which shows how e^jwt works. It is located: http://fourier-series.com/fourierseries2/complex_tutorial.html I have more work to do on this, but come take a look. I created these programs for complex numbers in order to explain the complex representaion of the fourier series. Brent