SINE OSC for 30.01 and 2495 MHz (?) sOLUtions?

[Fovakis]

Ηello! I want for my mixers sine frequencies for supply.+7dBm at 30.010 KHz and +4DbM at 2495 MHz...

Any solutions please? Crystals, Integrated, VCO, Synth ....

I am very confused..

Kindly Regards,
George

 

[BigBoss]

For 30kHz, crystal oscillator may be used..
For 2495MHz, LC oscillator ( Colpitts,Clapp, Differential etc.) should be considered..

 

[jcaram]

It sounds like you are trying to up-convert a 30kHz baseband to 2.4GHz RF, right? If you are designing a transmitter you will need more specs. For the RF you will probably need a synthesizer, otherwise your frequency will be moving around. For the baseband you can use whatever you want. Make a crystal oscillator with a crystal and inverter gates and then put a low pass filter to get a sine wave. Your 2.4 GHz don't have to be a sine wave if it's the LO driving your mixer. Actually the closer to a square wave the better. Amplify your signals as needed.

JP

 

[Fovakis]

Dear BigBoss, jcaram

i have attached a pdf, please check. Yes it is an upcoverter. At the moment i am doing the experiments usings Sine Signal Genarator to both mixers ..

*Αt 30MHz as i understand i will buy a crystal from ebay they are cheap (restancular pulses they have output as i know,right?), inverter gates and the the filter. I believe it will not be difficult to make this..i have an oscilloscope in my house so i will begin it right now to find schematics or something...

*About the high frequency. When i start i used only a VCO but there were phase noice to much so i put a signal generator at the moment. So first of all ...don't have to be a sine wave..wow!!!!That's really cool.why please? A square wave has got a lot of frequencies right so why this? Although as i understand i must buy a synth i cannot make in on my own right?

Many thanks i am a beginner in the RF-area

Kindly Regards,
George

 

[jcaram]

Ok, so both the 30MHz and 2.4GHz are local oscillators (LO). They should both be as much like as a square wave as possible.

This is how mixers work. The LO must reverse the polarity as hard as possible. While the LO is near zero (a sine wave is much more time near zero than a square wave), there is no signal output from the mixer, thus the conversion loss is high. Yes, a square wave will have 3rd order harmonics, this is, f, 3f, 5f, etc, but the mixer will generate harmonics anyway. So you drive your mixer hard with the LO and band-pass filter afterwards.

You definitely want a synthesizer for the 2.4GHz. Fortunately this is a very popular frequency these days, so you can find a single chip synthesizer with built in VCO. Search for that in digikey.com, or whatever supplier is near you.

Good luck,

JP

 

[biff44]

a better way would be make 2.495 MHz pll, and use digital phase sifter as a frequency translator to shift it to 30.010 kHz.

 

[tony_lth]

30K to 2.495M, some harmonics can't be filtered since they are in the working band except separating different bands with switch.

 

[Fovakis]

so you can find a single chip synthesizer with built in VCO. Search for that in digikey.com, or whatever supplier is near you. JP

Thanks for this help, i really appreciate this! Single chip synthesizer with built in VCO, can you please send me in inbox one product like this because i don't understand how tou search about it. :|

I am begginer in the field of RF so you can understand...

Kindly Regards,
George

 

[jcaram]

Hi there again. A synthesizer is a Phase-lock loop (PLL) driving a VCO. One example would be the Texas Instruments TF3765. You give it a reference frequency from a crystal, say 25 MHz, and it can generate an output from 300 to 4800 MHz in steps of a few kHz. Analog devices, Linear Technologies, and others also carry similar devices.
JP

 

[Fovakis]

Many thanks for your reply jcaram. As i understand it is too difficult to make a synthesizer for high frequency. I must buy one...but this later...

At the time about the 30,01MHz is it too easy to make one with output at 3-5dBm? There is no need of PLL to correct the phase frequency that will have for input to my mixer? I don't want to get bored from my questions but i am doing many things alone in the lab....

Best Regards,

George

 

[jcaram]

Hi Fovakis,
Sorry for the long delay. The crystal is your most accurate (for little money) source. If you can find a crystal of the exact frequency you need, that would be perfect. The simplest circuit would be a crystal with capacitors shunt to ground on each terminal, and an inverter going from one side to the other. Take the output from the output of the inverter.
JP

 

[Fovakis]

https://i1284.photobucket.com/albums/a578/fovos1/P5181092_zps5ee33fa8.jpg


Hi jcaram many thanks for your helpful replies. Yes it would be nice ..but i cannont find crystal osc 30.010khz

I think maybe the solution of a DDS would be better..because we are making mearuments with many frequencies maybe it would be better to have a tunable frequency.. do you know about these ?

i am thinking about this one:**broken link removed**

I need for my mixer +7dBm and 50 Ohm impedance, 30.010 khz also i want to memorize the settings when i close the l.o because i want it as part of the transmitter. You believe is this good? i can find dds only in ebay .. in digikey for exaple they have only the chips :O