Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

VHF/UHF transmitter- how to change the frequency?

Status
Not open for further replies.
J

jasonomb

Newbie level 6
Joined
Sep 19, 2009
Messages
13
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,347
transmiter vhf uhf

RFMD,RF2514,I want to know how to change the frequency?
The DT said ,It can fine-tuned via internal varactor diodes, but when I change the voltage of Pin10, the frequency didn't change,,,,,who can help me??thanks
 

VHF/UHF TRANSMITTER

Pin 10 is not the Varactor access, but the VCO tank.

Pin 12 gives you the access to VCO tuning.

I've noticed you added an inductor on VCO. If you want to run at lower freqs, just be aware that the available divition ratio is the proper one to give you lock condition in the synth.

I hope it can help.

Mazz
 

    J

    jasonomb

    Points: 2
    Helpful Answer Positive Rating
I use the pin12, but the frequency also did not change 。。IS my design has any problem??
 

Is someone use the Rf2514 before???Help!!!
 

There is no external tuning port on this chip! If you try to inject a DC tuning voltage into pin 12, you will be bucking the internal charge pump circuit, which is internally connected to the varactor diodes. They mislabeled the pin 12, it should not read "charge pump" output, it should read "connection point for loop filter capacitors".

This chip is obviously designed only for phase locked operation, not for manual tuning, so the only way you can change the frequency (slightly) is to pull the frequency of the reference crystal oscillator by using varactors in parallel with the crystal.
 

    J

    jasonomb

    Points: 2
    Helpful Answer Positive Rating
NOW,I using the varactor C1 3-10PF , the frequency change too much, how can I change the frequency slightly??
 

waiting for your answer·············
 

jasonomb said:
NOW,I using the varactor C1 3-10PF , the frequency change too much, how can I change the frequency slightly??
Click to expand...
The only way to change the output frequency is to change the reference frequency.The output will be changed by factor of 32 or 64 depending on programming.

The reference frequency can be changed by slightly by connecting a trimmer capacitor in serial but don't forget, changing in reerence frequency will be resulted 32 or 64 times in the output frequency..so 1kHz changing will be 32 or 64 kHz at the output..
This is not a robust solution...
The best solution is to use another programmable PLL is to provide a variable but stable reference frequency for the main PLL..
 

    J

    jasonomb

    Points: 2
    Helpful Answer Positive Rating
I understand now, thanks

Added after 1 hours 9 minutes:

If I off the power 3.3V of pin10,pin11,
let the PLL charge pump is disabled,then use 3.2V supply,is that ok?The frequency will change ???
 

I'm sorry but you request is not really detailed to give an answer, IMHO.

You're saying that you need to change the frequency, but:
what is the freq. you are running now?
what is your target freq?
do you need a lock condition or will you run in free oscillation?

Mazz
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top