## OT: Those arithmetic questions

Started by in comp.dsp1 year ago 25 replies

Often you see questions on social media such as - find the answer to 9/3(1+2) (they usually use the divide symbol which nobody uses of course...

Often you see questions on social media such as - find the answer to 9/3(1+2) (they usually use the divide symbol which nobody uses of course so= I have replaced it with a slash) and they spout on about order of operations and so left to right the answer= is 3x 3 =3D9 and the catch is that people answer 9/9 =3D 1. Ha, they don't= know their order of operations which was agreed by conve...

## Variable data rate PSK modem

Started by in comp.dsp1 year ago 9 replies

Dear All, I have a fixed data rate PSK receiver which works fine. Now I have to design a variable data rate PSK receiver. The Block Diagram...

Dear All, I have a fixed data rate PSK receiver which works fine. Now I have to design a variable data rate PSK receiver. The Block Diagram looks like this(Hope ASCII Art works): ADC-> AGC-> RRC-> Complex Mixer-> Coarse/Fine Carr.Recov-> Timing Rec-> BPSK/QPSK | | NCO---------------- When I try to add

## RF complex mixing

Started by in comp.dsp1 year ago 25 replies

Hello everyone. Could anyone explain please the next issues we know that there are no negative frequencies, so during real rf mixing the"-"...

Hello everyone. Could anyone explain please the next issues we know that there are no negative frequencies, so during real rf mixing the"-" frequencies fold back to positive F axis. so why during complex RF mixing the "-" Frequencies exist? I think that I understand that the complex signal can have "-" frequencies, but if we look at x(t)*cos and x(t)*-sin terms as ar real rf mixing

## replace zeroes with red noise before 2D FFT?

Started by in comp.dsp1 year ago 1 reply

I came across a claim in another forum for dealing with 2D FFT where there are dead traces (data is t-x domain before FFT). So if there is a...

I came across a claim in another forum for dealing with 2D FFT where there are dead traces (data is t-x domain before FFT). So if there is a dead channel, fill it with red noise whose amplitude matches roughly the other channels, then do the 2D FFT. Supposedly this minimises artefacts. Plausible?

## Frequency (Doppler) shift problem

Started by in comp.dsp1 year ago 7 replies

Hi all, I am processing satellite transmissions and assume no prior knowledge of the Doppler shift. Using a brute force technique I have been...

Hi all, I am processing satellite transmissions and assume no prior knowledge of the Doppler shift. Using a brute force technique I have been able to extract coarse Doppler and fit a polynomial. I wish to be able to use the polynomial to remove the Doppler components from the signal but have come up against a problem. Below is some (modified) code which illustrates the issue I'm

## charge pump related loop simulation in PLL

Started by in comp.dsp1 year ago 2 replies

Hello all: Though my question is not in the strict DSP, I cannot find another appropriate forum to discuss about it. As a hobby, I am interested...

Hello all: Though my question is not in the strict DSP, I cannot find another appropriate forum to discuss about it. As a hobby, I am interested in a PLL simulation. On numerous tutorials, I know there are current sources in a charge pump type phase detector. I realize that the current source makes the voltage cross the capacitor linearly increase. It is seen the Laplace transform of the RC ...

## Does decimating after Sampling mean loss of data?

Started by in comp.dsp1 year ago 1 reply

Dear All, I use an AD9371 board and on it the ADC samples the input at 1228 MHz, then the sampled data is decimated by 5 and a downsampling FIR...

Dear All, I use an AD9371 board and on it the ADC samples the input at 1228 MHz, then the sampled data is decimated by 5 and a downsampling FIR filter reduces the output rate to 122.8 MSPS. This is what I have as an input to the FPGA where demodulation occurs. The signal to be demodulated is an 80 MHz wide QPSK modulated one. For ideal demodulation I need a 320 MSPS (x4 symbol rate). My quest...

## Wavelength Dependency in RF Propagation?

Started by in comp.dsp1 year ago 9 replies

In an article in a recent issue of Microwaves & RF magazine, Jack Browne makes the following statement: Frequency plays a part in any link...

In an article in a recent issue of Microwaves & RF magazine, Jack Browne makes the following statement: Frequency plays a part in any link budget, especially for longer links, since long-distance links require the LONGER PROPAGATION DISTANCES of larger-wave-length, lower-frequency signals rather than smaller-wavelength, higher-frequency signals. (emphasis mine). I was miffed ...

## Wavelength dependency -2

Started by in comp.dsp1 year ago 1 reply

I enjoyed the article referenced below and noted that it said that 60GHz is the frequency which Oxygen molecules absorbed RF. Presumably other...

I enjoyed the article referenced below and noted that it said that 60GHz is the frequency which Oxygen molecules absorbed RF. Presumably other molecules have other frequencies, maybe some of them unknown at present which do the same thing. Can we therefore do the frequency response of an unknown Gas by passing RF through it? In that way finding chemical composition Thanks

## is true "Ormsby" filter trapezoidal /?\

Started by in comp.dsp1 year ago

I was looking through some open-source package, wherein the band-pass filter is described as ORMSBY. However, it has Hanning tapers, presumably...

I was looking through some open-source package, wherein the band-pass filter is described as ORMSBY. However, it has Hanning tapers, presumably to reduce the ringing/sidelobes in time domain. So is the name ORMSBY rather loosely defined?