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

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Jul 24, 2002
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ultrasonic bioinstrumentation christensen djvu

Well i build a blood flow detector and i really like know about more about this like circuit rf amplifier, mixer, demodulator detector, audio amplifier etc?? i really appreciate any information that u have!!! but more about the mixer if i can use a simple transistor like 2n2222 or BC457c the frequency that i will work is 2 Mhz and i will work with crystal PZT5 and i don't have much information about this any information will be receive like much happiness!!!!! 8O

about the mixer?????

I know that i must have one mixer??? well the question is if i can use NE602 for this propose??? :(

use regular radio circuits

The electrical portion of your system works just like ordinary radio equipment. You can use the mixers that are used in ordinary radios as long as they have an IF frequency response that goes to DC. This is because the frequency output will be below audio frequencies during part of the blood flow cycle.

But i can use the NE602 ???

Yes i know that i very similar the radio equipment, buti can use this Ci coz is very sheat and internally have a oscillator and mixer only i must creat a RF tuning amplifier for i can capture the echo??? and of course after the mixer i must creat a rectifier detector, after that a pass low filter and after a pass high filter??? ok another question is the echo how is the value approximat??? for example is my oscillator is working to 2 MHZ and the echo can be of 1.999 Mhz or value more low than that??? any suggestion??? plssssssss :cry:

usual design

The usual design method from years ago was to use a zero IF type receiver. Use the crystal controlled transmitter oscillator as the receiver LO. The easiest system method is to use two transducers, one for transmit and one for receive. You will need an RF amplifier in the receiver ahead of the mixer which can be the 602. The IF will be an audio type tone which can be low pass filtered to remove the 2 MHz feed through and then amplified by ordinary op amp circuits. The output signal frequency is related to the blood flow speed.


Very interesting, flatulent. As you say, it is symple DIRECT CONVERTION RECEIVER, such one i did 25 years ago for SWL :).

Please tell me, what is construction of transducers, and what is disposition of these transducers on a body?

Is this method suitable for any other flowing liquid or only for blood?

Best Wishes! klug.


The transducers are made from slabs of piezoelectric materials. The thickness is chosen to be at mechanical resonance for the frequency you select. The electrodes are placed on opposite sides of the slab.

The transducers are placed so that they point as close as possible to the flow direction.

Any fluid will work. This method was once tried for fuel flow in airplane engines. Because the frequency shift is dependent on fluid speed, it only works well with fast flows.

Other flow measurement methods work better when you do not have to stay outside of the pipe that the flow is in (called noninvasive measurement). Electromagnetic flow meters use the hall effect if the fluid has ions in it. Sewage is one example. I once designed a flow meter for sewer pipes. Testing them was a stinky job.


Well i will use for receiver the ne602 like u said coz this CI have the oscillator and mixer inside of course i will bulid a RF amplifier and i will try to use another circuit for receiver i will use oscillator, Rf amplifier and i will chance the mixer for adder circuit and after the pass low filter, but u can tell me about the echo??? is that i don't have idea the frequency of the echo??? of course must be more lower than oscillator in this case 2Mhz, and the PTZ5 the output voltage than this crystals can give me is about 1.75 Volts is that correct??? of course the transducer i bought i didn't build!!!!! any suggestion??? thanks for reply this topic!!!!!!! 8)

adjust frequency to transducer resonance

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.


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!!!!!

Hi Friends!

Flatulent, thanks for nice explanation! :lol:

Ironjaycuttler, you can simply calculate frequencies :

anyway you will need make some calculations in your meter. Take in account that the range of commonly detected normal flow speeds of blood is 10 to 100 cm.s-1. It is from :

**broken link removed**

Wish you Good Luck! klug.


Well thanks for all the people here in the forum, well here in Mexico there isn't much information (spanish) about ultrasound and more for medical aplications people like me search another options for can complete our investigation and thanks for this forum coz i can get information!!!!!! well i will report about this investigation int this topic so pls keep in touch and any suggestion is well received!!!

For flatulent!!!

Well another favor pls!!!!! if u have information about zero IF type receiver??? any webpage?? pdf format??? 8) anyway thanks for help!!!!

Hi ironjaycuttler!

Try to use google. Search by "direct conversion receiver". You will find a lot of schemes.

I have a link to very good book about DC receiving, but it is on Russian. Anyway you can look to circuit diagrames.

Best Wishes! klug.


hello klug well thanks for the information but tell me with what program can i open the file??? well like i told u the liast time i will try to build this device and one option that i have for oscillator is use SN74LS14N but i don't know if i will have problems when this signal (square) and the receiver signal (sine wave) to time to this signals are introduce to mixer i will have problems??? i mean the two signals must be sine wave??? the sn74ls14n is a good option??? is cheap, i can buy in any place here in my city, the output voltage level that this device give is around 2.1 Volts with this level of voltage i don't think damage the crystal ceramic PZT5 well if any person have suggestions are welcome thankssssssss!!!!! :wink:

Hi ironjaycuttler!

Take DjVu plugin for IE here:

Look at the page 26 (I mean number of page in a printed book), there you will find beginning of mixers description.

Page 26 - diod balanced mixer (Fosc = Frx). Left wire is from signal, right to amplifier, bottom wire to oscillator. You need not to put C5 capacitor, becouse you will need frequency band down to DC.

Page 27 - left from signal, right from osc, bottom to amplifier. Fosc=Frx .

Page 28 - left from signal, right to amplifier, bottom from osc. You will need not to put C4. Fosc=Frx/2 .

Page 29 - Look at circuit on top. Left from signal, right to amplifier, bottom from osc. Fosc=Frx/2.

Complete DC receiver you can find on page 56.

Use silicon diods with low capacitance. Oscillator voltage on mixer input need to be near 0.7 - 0.8 V.

All these mixers have dynamic range 70 to 80 db/mkV. For more big signals you will have parasitic AM. I think it is not very essential for you, becouse you will have no additional signals at input.

If your oscillator will make square shape signal then you will have more receiving of harmonic frequency 2*(Fs-Fosc). Maybe it is not so important for you. Anyway you can make LC filter to clean oscillator shape.

Heh, I have never used DC receiver to measure liquid flow by ultrasound, so maybe you will need some additional view on this problem.

Best Wishes! klug.


Hey very interesting information my friend Klug !!!!! Well i want make another question about heartbeat per minute??? this is a frequency for example 100 heartbeat per minute the question is this is same like frequency Hz??? or how i can know the echo that i receive is heartbeat per minute??? i don't know if u understand me :(

Hi ironjaycuttler!

As you know, frequency is quantity of cycling per second. We are defining pulse as quantity of heartbeats per minute. So,


With your ultrasound meter you are measuring the blood flow speed. You are not measuring pulse. To count pulse you need to count quantity of positive deviations (accelerations) of blood flow per minute.

Best Wishes! klug.


Klug well i doing a pdf format i really like that u can see this file of course after that i finish it!!!! that bad news is that is in spanish but u can see the little work that i'm doing!!!!!! well is all thanks for help!!!!



i need some information (lectures,ebooks,...)about mems based flow sensors.

would you please kindly help me?

mems123 :oops:

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