Doppler ultrasound blood flow detector???????

Why the receive signal (echo) is a Rf signal ????? i can use another type of amplifier for example i'm using a Rf tuning amplifier i can use another???

receive amplifier

The receive amplifier can be any ordinary type. The received signals are very small.

thanks for the answer, in this week i will probe my AC oscilator if i can obtain the sine wave i will upload the diagram here

well i have my local oscillator (2.25 Mhz) but i can't shift phase in 90° forward the problem is the high frequency i can't use Opams, so some here have a circuit that can shift phase 90° forward, i can use transistors??? or maybe only RC circuits????

i upload my oscillator circuit pls check

**broken link removed**

I need to know if all the required processing of the ultrasonic signal can be done by software or i must use some hardware before software processing. Does any one have ebook about the techniques used to process the reflected ultrasonic signal.

Pls another time i don't understand what is OL?? can u explaine me that?? ok so the frequency (echo) that i will capture is around (20-20 000Hz that's is the range audible) is that correct??? i sorry for my english is terrible thanks for all your advices!!!!!

You will have to operate the system at the transducer resonant frequency. the returned frequency will be in the audio range. You will have to tuse the LO in your mixer IC to suply the transmitter.

Hi Guys,

Great posts!

What ultrasound probes are you using? Femroal and poplited are best tuned to 4mHz and the peripheral artirial are 8 mHz. Has anyone got probes to suggest for either of these?

Using the quadrature the signals are broken into their complex and real signals using the I and Q channels respectively yes? Has anyone got a curcuit they could post on this?

I figure it goes like...

quadrature demod.
mix both complex and real channels with transmitted freq.
Bandpass filter - not sure of characteristics just yet - suggestions?
Amp both
A/D - both
DSP - phase detector or something like that. AD8302 would do the trick
D/A
LPF with cutoff at PRF/2 (max. meassured doppler phase)
= audio signal frequency coresponding to the velocity


The system i will be trying to build will have depth options (for every 13uS you can read the echo deeper by every centimeter). Has anyone designed a gain unit to operate at a funtion of time with factors of 100 (attenuation is 20dB per cm) per time t?

Also, you'd be probably better of using the pulse doppler system and isolating the emitter and receiver on the crystal you are using. It was suggested before... i think it might be your better option.

I found a sweet book in the library called Noninvasive Diagnostics Techniques in Vascular Disease - Eugene Bernstien which will point you in the right direction - alot of it is on B-mode diagnostics though. It's a bit old but still acurate.

If anyone could help that would be great

Quadtrature isn't needed it you have a 360 degree phase detector either that can ramp up to the 180 degrees then ramp down from 180-360, such that it can suggest which quadrant you are in, so is the phase change of 90 degrees (for the imaginary and real parts ) is worth it in the sense that a 360 phase chip can do the analysis for you?

Great post, guys!
I want some information on CW transducer too. Searched high and low for 10Mhz transducer and could not find it anywhere. Thanks for your input!

Hi Mate,

**broken link removed**

I found this company but i think they have problems replying in english. They can give you the peize eletric material at the round about frequency you want but you kind of need to build the case for it etc etc ( it think, so i am told, source is reliable but i'm yet to apply), cant remember what teh actually peizo status is but it a good reference for what you may want.... "vascular ultrasound" brings up a heap of info on CW if you do a google for it.

It seems there are onyl companies that build ultrasound systems (and not the transducers them selves). Let me know if you have any luck!!!!

https://www.smart-material.com/

thats the link,s sorry

Beaphster, Thanks for the link and reply. I had a look at the site. I prefer ready to use transducer if possible. But if that is not possible, or I may need to built a custum made transducer for a special purpose, this is the great place the get the material. Actually I have done google search for a couple of days, and they do not return much useful informations. As you mentioned, most of them are for medical systems used in hospital, and if I do find some transducer manufactures, they supply transducers ( alone priced from $1000 to $10000) to medical systems. They may not fit in my need and my budget, I just want a simple transducer. Actually, I have found a place to get transducers that will similar to what I wanted: **broken link removed**
But they say they only carry transducer for pulsed doppler flow meter. According to them, their transducer will not work with CW flowmeter. I do not understand why they are specific to pulsed, or CW. do you guys has any idea? Thanks.

beaphster said:

Hi Mate,

**broken link removed**

I found this company but i think they have problems replying in english. They can give you the peize eletric material at the round about frequency you want but you kind of need to build the case for it etc etc ( it think, so i am told, source is reliable but i'm yet to apply), cant remember what teh actually peizo status is but it a good reference for what you may want.... "vascular ultrasound" brings up a heap of info on CW if you do a google for it.

It seems there are onyl companies that build ultrasound systems (and not the transducers them selves). Let me know if you have any luck!!!!

Click to expand...

Hi W888k,

There could be a few reasons...

Sometimes the piezo matireal can explode when continues stimulation fo a period of time ios applied (but usually only over a period of hours) as this matireal is rather fragile and such like.

Pulse Doppler only use the one transducer for the detection and emitting process, where CW doesn't, because you are measuring an entirely diffferent outcome, and this material will have a better resonance and probably stop ringing the exact time you retard the power stimulation making it far superior product for Pulsing (but it should work for CW, unless I'm proven otherwise)... Pulse Doppler requires alot more thinking but it shouldn't hurt your budget.. I'm still in the process of making one however, so i won't speak too soon.

Does anyone know if PLL is a good solution? I'm not too farmiliar with PLL (phase lock-loop)...

beaphster:

Thanks for your input. I guess it is. It did not make sense if for the same frequency, pulsed wave can excite the transducer while the CW can not. sure pulsed flow meter is better for CW flow meter, but for my flow meter, I want somthing small and simple, that is why i go with CW. For the PLL, I heard from a friend once it might be good to use, however, I am not familiar with it either and did not have the chance to get my hand on it.

Gday,

w888t, What RF analysis are you looking at doing. I've done a bit more research into PPL but it usually deals with the higher frequencies (greater than 10Mhz, usually Ghz range) so i would be interested in how you are doing it or plan to do it.

Can anyone assist in the developement of PLL... The worry i have is that i will be using pulse doppler so there might not be enough time for the PLL to lock onto the signal, especailly if the signal is > 8MHz and pulsed on for only 8 cycles (maybe max. of 40).

I was going to mix the incoming with a quadratured version of the carrier arrangement then do some intergrating RC circuit stuff after filtering the carrier out so then i have the quadrant location, but am not confident in either this or the other PLL approach.. could someone ease my woes. Ideal I'd like to use a single supply source... any tips

Beaphster

Hi:

As I mentioned before I have no experience with PLL. Since that gave me headache. That was a few years ago and when I tried to some way to extract doppler frequency from carry frequency. I used a mixer instead. Sorry I can not help.

Hello CW Doppler Enthusiasts,

There is a new part, TI AFE8201 that when coupled to a 55X dsp
might be a (very) simple solution for doppler.
It would also allow a subtractive wall
filter to be built using the DAC.

Other Interesting Doppler Parts I have seen,

AD630 Demod
SA602A Gilbert Cell Mixer w/OSC
AD831 Mixer
AD8302 Gain / Phase Detector
ADS1605 A/D
LTC1407 Dual A/D
AN2201E04 Programable Filter

Have any of you prototyped with these parts?

Sonoman :agrue:

I would like to know from where can I get the piezoelectric crystal of half circle shape?