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

Cross Coupled LC oscillator design

Status
Not open for further replies.
G

gkini19

Newbie level 5
Joined
Jul 22, 2021
Messages
8
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
86
Hi guys,

I was looking for a video or a document that discusses the detailed design of cross coupled LC oscillator with 18-20 GHz. I have read the design procedure from RF microelectronics Razavi. But if have a video or document would be better, please post the links if you know.
 

Sort by date Sort by votes
I'm not familiar with the Razavi design but here's a simulation made from series LC bridged across the emitter legs of 2 cross-biased transistors. Another topology has an H-bridge using 4 transistors.

A common guideline is to use an inductor value which is between 1,000 and 100,000 times the capacitor value.

LC series across emitter legs of cross-biased NPN 1400 MHz.png
 
Upvote 0 Downvote
Every case is different while an oscillator being designed.But as a rule of thumb is to obtain sufficient negative resistance by adjusting biasing current such that all losses in the tank circuit are far compensated by this negative resistance.In additional to this, Noise requirements, Amplitude specifications, Harmonic demands play role in oscillator designs.There is no straightforward design methodology except some well known topologies but it looks like "cut and try" technique.
 

Upvote 0 Downvote
Thanks for the reply.

so first we find the resistance of the LC tank circuit by S parameters, is it right ?

Then we build the cross-coupled pair and have a transconductance more or equal to the R of LC Tank
 

Upvote 0 Downvote
gkini19 said:
so first we find the resistance of the LC tank circuit by S parameters, is it right ?Then we build the cross-coupled pair and have a transconductance more or equal to the R of LC Tank
Click to expand...
Not more or equal..The rule of thumb \[ 3*R_{p}\leq |R_{active}| \]
 
Last edited:

Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top