### James (Jim) kain (@jekain314)

Dan --I assume the Out-of-Bounds Emissions (OOBE) are from neighbor transmitters operating at 802.11 (e.g., independent neighbor 20MHz channels sensed by the antenna)....

I assume the edge subcarriers (6 outter subcarriers at each edge) transmit zero to enable band-pass filtering of the neighbor 20MHz 802.11 channels. Why is it that...

Thanks Dan (and others) ... Below/attached is my math-only attempt to answer from a time-domain perspective. The derivation assumes the per-carrier QPSK symbols...

Consider a 64-subcarrier OFDM signal with QPSK modulation and all 64 subcarriers have data. Each of the 64 subcarriers will have the same amplitude (assume 1.0)...

Kaz ..Thanks for your patience. I see your point. My proposed approach of re-purposing the IQMixer with two real-only inputs would actually work -- as I showed with...

Kaz ... maybe you inserted too many zeros?Not sure what this does: zeros(1,122)maybe should be zeros(4,125) -- put zeros into elements 4 through element 125.there...

The input vector of length 128 has the added terms to force a "real" output from the IFFT. You are correct, I am plotting the "real" component (left) and the "imaginary"...

kaz --maybe try the following if its easy.Generate a time function from a sum-of-three-single-tones.s(t) = (Cos(t)+Sin(t)) + (Cos(2t)-Sin(2t)) + (-Cos(3t)-Sin(3t))QAM= ...

Kaz -- no need for politeness -- I am looking for someone to show me why the real-only paths wont work -- so I dont waste more of my time. My goal is a hardware...

Kaz ..The channel will indeed modify the phase and amplitude --- this is the key purpose of multicarrier waveform -- to be able to establish the required phase/amplitude...

also could addXXX = fft(y)Test to see if xxx = xx -- this must be true.If we do the code twice and add in the IQMixer up/down conversion (+LPF) for the TWO real...

The output from the IFFT (real-only after extending the input to 2N) is the sum of all the QAM-modulated individual subcarriers. After up-down-conversion by the...

maybe go back to the code you wrote -- the octave code below. You indicated you didnt get a real output. I downloaded Octave and will try this.x = randn(1,64)+j*rand(1,64); ...

kaz ---The A1,B1 (complex A1+iB1), extended to 2N terms, is input to the IFFT to produce 2N real-only time-points -- we just call this "I" because its the baseband going...

I added a video showing simulation results for OFDM with real-only datapaths.https://www.youtube.com/watch?v=9aKPk-OfnMc

The file shows simulation results that address use of real-only OFDM transmissions.Simulation Results for OFDM with real-only transmission

Sorry for delayed response .. I'm working on a simulation to demo the results described below. You stated:....most channel effects of interest to comm systems that...

I think the long play is robustness/graceful degradation to channel disturbance with fixed BER and spectrum use. The real-only path recursive solutions provide a...

The s1(t) and s2(t) are two totally independent communication signals. Just like two separate MIMO streams. If I can send 54mbps on s1(t), then I can also simultaneously...

So sorry kaz --- I'm not a Matlab programmer.I hand-bang this stuff using Visual Studio and C/C++. The issue may be the mechanization of FFTW -- its very well documented...

Eric -- your credentials are indeed impressive. And I agree that suggesting a 2x datarate improvement for a 50-yr-old tech is a bit like anti-gravity boots. My background...

thanks for noting this confusion.I was (erroneously) referring to the FFTW software implementation of the IFFT. There, the input array is a complex array (each array...

Slartibartfast -- thanks for your patience. I admit I didnt follow your semantic explanation. With OFDM, at the transmitter, we start in the frequency domain --...

I am thinking of an app that does both comm and GNSS in the presence of unwanted (and unknown) signals. The AD9084 4Tx4Rx transceiver chip has a "Spectrum Sniffer/Monitor"...

I was under the impression that the IQMixer had the ability to send two independent time-history signals, s1(t) and s2(t), within the same bandwidth. From the...

Consider a 64 subcarrier OFDM waveform with 20MHz bandwidth. At the transmitter, we would generate 64 complex numbers (A(n) + jB(n)) n=1, 2, 3, .... 64 using the...

cant seem top open the attachments ..when I click, nothing happens.maybe just send to: jekain314@waldoair.com

Thanks Matt (and Chuck) for your thoughtful response(s). I am getting in to the communications field after "retiring" from another engineering field -- solely because...

My question came from considering the goals of SDR to move the ADC closer to the antenna (e.g., Direct RF sampling) -- also the youtube article below that discussed...

I am looking at the pre-release Analog Devices AD9084 -- APOLLO MxFE. This has 4TX and 4Rx and ADC/DAC at 20/28 Gsps. There is also a less capable but similar...

A key to robust-to-disturbance high-speed data transfer is the multicarrier waveform. The preamble's individual tones with predefined phase/amplitude act to calibrate...

Charlie .. Thanks for the detailed note.wow ... that goes way back. I found your/Gold's original Lerner filter work at Lincoln Lab circa 1965:https://apps.dtic.mil/sti/tr/pdf/AD0627146.pdfI'll...

Use this form to contact **jekain314**

Before you can contact a member of the *Related Sites:

- You must be logged in (register here)
- You must confirm you email address