reference oscillator for phase loked loop design

ubp1507

i want to design PLL at 2.2Ghz (s-band) for that purpose i need a reference oscillator at about 550Mhz any one plz tell me that what is the maximum frequency available in crystal
can i use any other oscillator as a reference

upb1507

I am not shure about your design but reference oscillatiors with crystal are in the frequency range up to few tenths of megahertz. I believe 500MHz crystal do not exist.

jtos 3000 vco

Commercially available crystal resonators on 550 MHz you can not find but you can try one of following solutions. First is what I would do:

0. You can use one of hundreds PLL ICs available in that frequence range and follow the application note. Use a VCO like JTOS 3000 from mini-cicuits or similar from Z-comm.

1. I understood that you want just to generate one channel at 2.2 GHz and you do not need another frequencies. I suppose that you have just prescaler dividing by 4 and therefore you would like to have so high reference. If jou do not have extreme phase noise demands use a prescaler dividing by 64 (e.g. UPB 1507 ftom NEC) allowing you to get a crystal on 34.375 MHz and that you can buy easy. Second advantage is that you can use digital phase comparators instead of mixer that you must use for 550 MHz reference.

2. You can use 180 MHz 7th overtone crystal oscilator and use its 3d harmonic as reference for your loop. Drawbacks: you need filtering and amplifying for the harmonic and you must build the oscillator from discrete components. Of course it will also cost more. You can even try to use 11th or 13th harmonic of a crystal oscillator without a loop.

3. If frequency stability is not a very big issue for you, you can try to use SAW resonator oscillator as a reference.

Actually, the possibilities for generating a 2.2 Ghz signals are unlimited, maybe it is best for you to specify your problem exactly and the solition could be readily found.

Regards,
D

Why do you need such a high reference oscillator frequency? Can you provide a block diagram of your PLL so we can take a look?

Muhammad Furqan said:

i want to design PLL at 2.2Ghz (s-band) for that purpose i need a reference oscillator at about 550Mhz any one plz tell me that what is the maximum frequency available in crystal
can i use any other oscillator as a reference

Click to expand...

i need frequency and phase stability that's why i prefer PLL to lock the oscillator at 2.2Ghz and for reference i use divide by 4 that is 550Mhz
can divide by 64 give the stable output free from phase noice

Stability of the output frequency is the same as the stbaility of the reference oscillator. You can find reasonably priced 30 MHz TCxO (prescaler 64) with stability better of 2 ppm. With such loop you can get enough phase noise performance for any communication application. If you target radar application phase noise can be a problem but this demand additional analyze. Anyway, I would test the simplest solution.

Regards
D.

Debeli, if i use ubp1507 as a divide be 64 scheme then,
would i get crystal at 34.375Mhz easily
can this provide frequency stability because this would be used as the reference for 2.2 Ghz

Muhammad Furqan said:

Debeli, if i use ubp1507 as a divide be 64 scheme then,
would i get crystal at 34.375Mhz easily
can this provide frequency stability because this would be used as the reference for 2.2 Ghz

Click to expand...

1. you should specify required stability when you order your crystal from the supplier. ± 10 ppm can be achieved without compensation and resonator frequency is not a major factor here.
2. 34.375 MHz resonator is no problem for manufacturing, but if it is not produced in high quantities the price will be higher and delivery time will be longer. You should contact some distributors/manufactureres in your area to check availibility.
3. Using lower frequency reference oscillator does not influence output frequency stability by it self, but influence phase noise in loop bandwidth near to carrier. However, you should specify your phase noise requirements before you decide what reference frequency to use. From my experience I can tell that 34 MHz reference is suitable for 95% applications in 2GHz range.

Regards,
D.

It's important to know that the 2.2 GHz phaselocked oscillator will have the same stability in ppm as the reference crystal oscillator has in ppm. E.g. 2 ppm at 34.375 MHz is 2E-6*34.375E6=68.75 Hz stability of the crystal. But 2 ppm at 2.2 GHz is 2E-6*2.2E9=4.4 kHz stability of the 2.2 GHz phaselocked oscillator.

You can count backwards to verify this: 68.75 Hz crystal oscillator stability multiplied by 64 is 64*68.75 Hz=4.4 kHz.

Muhammad Furqan said:

Debeli, if i use ubp1507 as a divide be 64 scheme then,
would i get crystal at 34.375Mhz easily
can this provide frequency stability because this would be used as the reference for 2.2 Ghz

Click to expand...

Well I think mobile phone use tcxo, am not realy sure but u can find out
lots of mobile phone which u can take theire tcxo
good luck

By the way, I find some system users require the TCXO to be 10MHz or 20Mhz, for that easy to calculate, but that is hard to fit for the RF Frequency plan!

hi
can higher order frequency dividers like divide by 10----40 results in the increament of harmonics or frequency insatability

you might use few ten MHz xtal for DDS and use DDS output as a reference for your PLL. It might work.

Crystal oscillators are not noise free. With only a small divide ratio after your 550 MHz oscillator, you may find your closed loop close in phase noise is very poor.