EMRFD Message Archive 15259

Message Date From Subject
15259 2019-03-17 02:31:46 Ashhar Farhan Low noise integrated VCOs
How do the integrated circuits like Si570 manage to build low noise VCOs without large components?
From HF experience, we know that LC oscillators provide the low,.clean energy. In GHz range, it needs a transmission line resonator. However, I can't see how either of these can be built into these VCOs.
Can anyone illuminate me?
73, f.
15260 2019-03-17 03:42:58 Russell Shaw Re: Low noise integrated VCOs
15261 2019-03-17 05:17:13 Lasse Moell Re: Low noise integrated VCOs
It seems it is now possible to realize a fairly high-Q resonator on die at frequencies 5GHz and above.
I have been playing with the LMX 2594 with an integrated VCO (8-15 GHz) and it amazes me how good the performance is.
Once chip covers 10 MHz to 15 GHz!!!! The free running performance of the VCO is not bad at all, and puts a very high demand on the reference not degrade the phase noise in closed loop.

One thing that may contribuet is a limited range of a VCO, the chip often integrates several VCO's (more than 5 to cover an octave) and uses clever ways of linearize the tuning.

/Lasse SM5GLC


17 mars 2019 10:31:32 +01:00, skrev Ashhar Farhan farhanbox@gmail.com [emrfd] :
 


How do the integrated circuits like Si570 manage to build low noise VCOs without large components?
From HF experience, we know that LC oscillators provide the low,.clean energy. In GHz range, it needs a transmission line resonator. However, I can't see how either of these can be built into these VCOs.
Can anyone illuminate me?
73, f.



15262 2019-03-17 06:56:47 Tayloe, Dan (Noki... Re: Low noise integrated VCOs
The SI570 uses a mechanically vibrating silicon lever.  It has to be pretty small to run at the frequency they are running it at.  I am not clear on how they tune it so it can be used locked in a VCO.

- Dan, N7VE

Sent from my Galaxy Tab® A


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15267 2019-04-14 16:04:47 winston376 Re: Low noise integrated VCOs
When I read the tech data on this ic I thought it used internal dividers controlled by external I2c commands
15268 2019-04-14 22:39:06 Ashhar Farhan Re: Low noise integrated VCOs
Dan,
the crystal oscillator of Si570 runs at a fixed frequency of just above 100 MHz. It is then, locked to a VCO that runs between 4 and 5 Ghz, using a fractional divider. The output of the VCO is then divided down to a lower range using an integer divider. 
Simiarly, the Si5351 uses a VCO that is locked to a 27 Mhz or 25 MHz crystal reference. The VCO itself runs between 600 MHz and 900 MHz. It is divided down to the required frequency between 5 KHz and 200 MHz.
- f

15269 2019-04-15 13:18:04 Dana Myers Re: Low noise integrated VCOs
15270 2019-04-16 23:14:33 Ashhar Farhan Re: Low noise integrated VCOs
ugh, got it. one should never change coffee so quickly.
- f