Power Ratios?

Started by Anonymous in comp.dsp1 year ago 14 replies

I'm confused by some code I wrote to measure signal amplitude from a CODEC. The FPGA sampled for some period of time squaring the samples and...

I'm confused by some code I wrote to measure signal amplitude from a CODEC. The FPGA sampled for some period of time squaring the samples and summing them up. I did not take the square root of the result, at least not in the FPGA. I would expect this result to be proportional to the power in the signal. When I compare this number at multiple frequencies to get the variations,


Correlation Versus Simple Filter

Started by Randy Yates in comp.dsp1 year ago 10 replies

Gentle Readers, Ok, I've been out of DSP for way too long so maybe this is a stupid question, but in the interest of getting my feet wet...

Gentle Readers, Ok, I've been out of DSP for way too long so maybe this is a stupid question, but in the interest of getting my feet wet again, here goes. Let's say we have a tone which we want to detect. Which is going to give better performance, correlation followed by a threshold or a simple bandpass filter followed by an energy detector and threshold? -- Randy Yates, DSP/Embedded ...


Ultrasonic speech

Started by Anonymous in comp.dsp1 year ago 1 reply

A client for unknown reasons wants to emit speech in teh frequency range above 20kHz. I was wondering what is the best way around this to do a...

A client for unknown reasons wants to emit speech in teh frequency range above 20kHz. I was wondering what is the best way around this to do a frequency shift. Then presumably I would need a sound card on a PC with high sampling rate and ultrasonic amplifier and loudspeaker. (this can be bought). So I sample at say 44.1KHz as usual a section of speech and store to wav file. Then I


Elwyn Berlekamp RIP

Started by Steve Pope in comp.dsp1 year ago 2 replies

A few of us had the great fortune to work with Elwyn Berlekamp during our careers. He passed away on April 9, 2019. The most prolific and...

A few of us had the great fortune to work with Elwyn Berlekamp during our careers. He passed away on April 9, 2019. The most prolific and most genius expert on algebraic coding, Berlekamp also contributed significantly to game theory, cryptology, and quant. He was a member of the USA National Academies of both Engineering and Science, recipient of both the Shannon Award and the Hamming M...


Homodyne complex frequency shift

Started by DSP newbie in comp.dsp1 year ago 5 replies

Hi, the input signal is sin(t), I multiply it with cos(t) to get the I component and sin(t) to get the Q component. So...

Hi, the input signal is sin(t), I multiply it with cos(t) to get the I component and sin(t) to get the Q component. So then I(t)=sin(t)*cos(t)=0.5*sin(2t) Q(t)=sin(t)^2 I would expect only the DC component to persist, but instead I have two quickly wiggling waves. What is missing to shift 1kHz to DC without introducing the mirror frequencies? Thanks in advance!


Multiple PDM mic recording

Started by Qe in comp.dsp1 year ago

How to record multiple PDM mics at 16KHz? What is a recommended soundcard/HW that can be used?

How to record multiple PDM mics at 16KHz? What is a recommended soundcard/HW that can be used?


Threshold of hearing compensation

Started by Anonymous in comp.dsp1 year ago 5 replies

There are several new consumer headphone products on the market that allow you to measure your threshold of hearing using an app on your phone and...

There are several new consumer headphone products on the market that allow you to measure your threshold of hearing using an app on your phone and then auto-adjust an equalizer to boost the areas where your threshold is high (indicating hearing loss at those frequencies). I’m no audiologist but this seems suspicious to me; I don’t think having a high threshold is the


short pulse generation with DSK6416

Started by farzinalm in comp.dsp1 year ago 2 replies

Hello, I'm trying to generate short pulses with DSP's 32-bit timer. I'm using the DSK6416 board (@1GHz) . I need to have pulse widths as...

Hello, I'm trying to generate short pulses with DSP's 32-bit timer. I'm using the DSK6416 board (@1GHz) . I need to have pulse widths as short as 10ns-50ns and be able to change the duty-cycle. I try to read the CNT register of the timer and set DATOUT to be driven on TOUT pin of timer when the proper width has reached. The problem is that when I use the TIMER_setDatOut API it is not possible...


Efficiency of Midi->Freq and back

Started by MatthewA in comp.dsp1 year ago 2 replies

I'm writing something with a lot of conversions between midi and frequency in a timing tight situation and I'm wondering about efficiency. (in C)...

I'm writing something with a lot of conversions between midi and frequency in a timing tight situation and I'm wondering about efficiency. (in C) What are the community's experiences with this? Would a 1 or 10 cent interpolated lookup table be more efficient? Is there a way to make the log less expensive? Does caching and comparing the last input and output help? Thanks for any insig...


High-order EMA works great - but why?

Started by Piotr Wyderski in comp.dsp1 year ago 3 replies

I have a classic digital PLL with multiplier-based phase detector, intended to lock at 50Hz. The sampling frequency Fs is 25kHz, the...

I have a classic digital PLL with multiplier-based phase detector, intended to lock at 50Hz. The sampling frequency Fs is 25kHz, the loop filter bandwidth varies between Fc=10Hz to 40Hz, as I am experimenting with different filter structures. The PLL itself works like a charm and my reference filter is a 500th order FIR: fir1(500,Fc/(Fs/2)). To a reasonable degree the loop converges to a ...


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