I used sbl-1 mixer for decreasing signal frequency from 3.174 MHz to 10 kHz. The generated signal has high noise level. The butterworth and sallen-key filter was used to eliminate noise, nevertheless there is the noise. There is also the possibility of sending images of the circuit. How can i eliminate the noise?

Please help me.

Thank you

 

Hello,

Can you give a full schematic of the circuit?
Also the use of a breadboard for RF is not done.
The long wires and the breadboard itself will give you a lot of crosstalk.

Bertus

 

You have no idea on what noise you really have with the setup you are using. With the wires suspended in the air like you have, they are able to pick up all kinds of stray signals.

NEVER expect a plugin type experimenter's board to give you good results. Also, NEVER use them for anything RF.

Google "RF PROTOTYPING" and see if you can get any techniques on how to properly do what you want.

 

Hello,

One of the possibilities for RF prototyping that will not cost to much is the manhattan style.
This page shows you some examples:
http://www.sdmakersguild.org/the-art-of-manhattan-style-circuit-construction/
And have a look at the attached PDF.

Bertus

 

One of the possibilities for RF prototyping that will not cost to much is the manhattan style.

Also look up "dead bug" style. For RF prototyping, ALWAYS use a ground plane.

 

Hello,

Can you give a full schematic of the circuit?
Also the use of a breadboard for RF is not done.
The long wires and the breadboard itself will give you a lot of crosstalk.

Bertus

Thanks for your attention
The schematic of circuit is in attachment file.

 

Hello,

What are the signal levels you are using?
The RF may be upto +1dBm, the LO may be upto +7 dBm.
+1 dBm is about 0.7 Vpp.
+7 dBm is about 1.4 Vpp.

Bertus

 

Hello,

What are the signal levels you are using?
The RF may be upto +1dBm, the LO may be upto +7 dBm.
+1 dBm is about 0.7 Vpp.
+7 dBm is about 1.4 Vpp.

Bertus

The function generator was used as an local oscillator. Its voltage (peak to peak) is 5 V and Its current is probably 20 mA .The voltage of RF (peak to peak) is about 600 mV.

 

Hello,

Then try to reduce the LO voltage to about 1.4 Vpp.

Bertus

 

The AD9850 module was also used as an local oscillator. Its voltage (peak to peak) is 1 V, But there is still noise.

 

Hello,

Do you still use the breadboard?
The breadboard will not work for RF.
There are other ways for prototyping suggested.

Bertus

 

Hello,

Do you still use the breadboard?
The breadboard will not work for RF.
There are other ways for prototyping suggested.

Bertus

that's sad..breadboard for testing before final product

can use wire wrap method?

 

The function generator was used as an local oscillator. Its voltage (peak to peak) is 5 V and Its current is probably 20 mA .The voltage of RF (peak to peak) is about 600 mV.

So was your LO 5 V peak to peak or 600 mV peak to peak? An SBL-1 is designed for a LO input level of +7 dBm, it will not work well with an LO input level too far off of this design value. +7 dBm translates to 1.4 volts peak to peak (in a 50 ohm system).

And and since you are using a function generator, are you driving the LO port with a sine wave, a square wave, or other?