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.

Simulating Cross Coupled VCO

Status
Not open for further replies.

InspectorGadget

Junior Member level 1
Joined
Oct 17, 2012
Messages
17
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,283
Activity points
1,432
As part of an assignment for my RF course I've been asked to pick an element of a specific RF circuit from a research paper given to us and do some simple simulations of that device.
The part I chose was the Voltage Controller Oscillator from a PLL. Our task is pretty vague, but essentially we must simply create a circuit in PSPICE/Cadence etc and simulate it to show functionality (in my case that it oscillates!).

I've been trawling through the interwebz researching the various types of VCO out there. Most info just shows simplified schematics and very few hard figures/details.

Attached is a screenshot of my PSPICE schematic for a cross coupled, LC tank, VCO (although in this case to keep it simple I just put a fixed cap in rather than a varactor). The problem is that after running transient analysis I only see a 12V DC voltage at the OUTP node. I'm sure I'm doing something very simple wrong, but if anybody had some pointers for getting myself an oscillation I'd be very happy. :smile:
 

Attachments

  • VCO.jpg
    VCO.jpg
    162 KB · Views: 76

One thing of importance is whether the drain tank inductors are truely separate and isolated as shown in PSPICE diagram or a single tapped inductor having cross coupling.
 

Does it oscillate ?? To check this, you should verify the negatif impedance which is seen toward active part of your VCO.
In fact, there are few methods(open loop gain,oscillator driving point impedance and phase etc) to see the that the oscillation conditions are satisfied or not but first step is to check negative impedance.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top