decreasing wave frequency with sbl-1 mixer

Thread Starter

jalil92

Joined Jun 7, 2019
7
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
 

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bertus

Joined Apr 5, 2008
21,263
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
 

SLK001

Joined Nov 29, 2011
1,548
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.
 

Thread Starter

jalil92

Joined Jun 7, 2019
7
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.
 

Attachments

Thread Starter

jalil92

Joined Jun 7, 2019
7
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.
 

Thread Starter

jalil92

Joined Jun 7, 2019
7
The AD9850 module was also used as an local oscillator. Its voltage (peak to peak) is 1 V, But there is still noise.
 

bertus

Joined Apr 5, 2008
21,263
Hello,

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

Bertus
 

Ylli

Joined Nov 13, 2015
1,030
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?
 
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