Uploaded March 2022 | Updated September 2026, 3 weeks ago
A comprehensive review of all approaches to linear and nonlinear stability analysis in high frequency circuits, followed by an introduction of a powerful new technique called Winslow Stability analysis that replaces all 28 tedious traditional stability simulation with just 1. Tom Winslow – the inventor of WS Probe for this comprehensive stability analysis explains why. A demo illustrates how this is done and concludes with a novel EM-circuit excitation technique to locate the causes of instability so that you can fix your design before building hardware. The Q&A session features more Tom Winslow’s explanations.
0:00 Keysight Technologies Company Overview
2:00 Introduction to Tom Winslow & Stability Analysis
2:51 Why design for Stability in High Frequency circuits?
4:00 Stability (K) factor
4:49 Problem: Lots of Stability analysis approaches
5:17 Even more stability simulation techniques
5:45 Winslow Probe simplifies Linear/Nonlinear Stability Analysis – 1 simulation replaces 28
6:30 Agenda: Understanding & Simplifying Stability Complexity
7:13 Background – Review of Feedback Systems
8:44 Finding Closed Loop Instability – Right Hand Plane Poles/Zeros, Cauchy’s Principle
10:04 Idealized Feedback Loop Simulation – OscTest
11:17 OscTest assumptions can lead to Inaccuracy
12:17 Middlebrook loop gain technique
18:20 Hurst bilateral loop gain technique
14:19 Fundamental concepts in Stability Analysis
14:32 Four common techniques give conflict answers – which is correct?
15:19 Fundamental Stability measures provide context; Nodal equations - Driving Point Impedance; Transfer functions - Return Ratio
17:34 Return Ratio and Return Difference – need to access internal transconductance
18:16 Driving Point Admittance : Kurokawa oscillation condition
19:37 Modern Return Ratio – Normalized Determinant Function (NDF)
20:58 Modern Driving Point Admittance – Auxiliary Generator (Y-AG) Kurokawa condition
21:29 True Return Ratio (TRR) external loop gain characterization
22:28 TRR assumes simple device model
23:54 TRR related to Driving Admittance
24:52 Loop Gain – a valuable intuitive design tool
25:39 Summary of Return Difference, Driving Point Admittance & Loop Gain
26:36 Unifying Stability Simulation using in-situ probing
27:02 Challenge: Each Stability Analysis requires a different setup
28:07 Tom Winslow introduction and reasons for inventing WS probe for unified stability analysis
31:46 WS probe is accurate under arbitrary levels of feedback
35:35 WS probe computes all stability figures of merit in a single simulation !
37:09 1 WSP simulation = 4 OscTest simulations
37:51 1 WSP simulation = 4 Middlebrook loop gain simulations
38:20 WSP simulation = Hurst loop gain simulation
38:48 1 WSP simulation = 4 Total Return Ratio simulations
39:16 WSP simulation = Normalized Determinant Function simulation
39:51 1 WSP simulation = 14 Driving Point Admittance simulations (1 simulation per node) in Auxiliary Generator method
40:58 Stability Analysis for Large Signal simulation
42:15 WS Probe extends Stability Analysis easily to nonlinear large signals
43:30 WS simulation simplifies stability analysis & deriving impedance/admittance measures
44:40 Demo of WS probe in ADS
46:55 Need to model feedback loop to detect instability
47:14 Electromagnetic RFPro analysis to identify potential feedback loops
47:45 Instability revealed under large signal excitation
48:33 Identifying direction of unstable feedback
49:47 Circuit-EM excitation to visualize and locate causes of unstable feedback
50:39 Output to Input unstable feedback identified
50:58 Output unstable feedback through ground loop identified
51:19 Fixing causes of instability by targeting feedback mechanisms
51:43 Verify instability fixes with EM visualization
52:06 Closing & Summary – WS probe comprehensively perform small/large signal stability analysis with a single setup to replace 28 traditional different simulations
53:50 Q&A
Apply for a Free Trial at keysight.com/find/mytrial.rfmw.vi
See Part 2 of 2 at youtu.be/Nmo_-K3vgo8
A comprehensive review of all approaches to linear and nonlinear stability analysis in high frequency circuits, followed by an introduction of a powerful new technique called Winslow Stability analysis that replaces all 28 tedious traditional stability simulation with just 1. Tom Winslow – the inventor of WS Probe for this comprehensive stability analysis explains why. A demo illustrates how this is done and concludes with a novel EM-circuit excitation technique to locate the causes of instability so that you can fix your design before building hardware. The Q&A session features more Tom Winslow’s explanations.
0:00 Keysight Technologies Company Overview
2:00 Introduction to Tom Winslow & Stability Analysis
2:51 Why design for Stability in High Frequency circuits?
4:00 Stability (K) factor
4:49 Problem: Lots of Stability analysis approaches
5:17 Even more stability simulation techniques
5:45 Winslow Probe simplifies Linear/Nonlinear Stability Analysis – 1 simulation replaces 28
6:30 Agenda: Understanding & Simplifying Stability Complexity
7:13 Background – Review of Feedback Systems
8:44 Finding Closed Loop Instability – Right Hand Plane Poles/Zeros, Cauchy’s Principle
10:04 Idealized Feedback Loop Simulation – OscTest
11:17 OscTest assumptions can lead to Inaccuracy
12:17 Middlebrook loop gain technique
18:20 Hurst bilateral loop gain technique
14:19 Fundamental concepts in Stability Analysis
14:32 Four common techniques give conflict answers – which is correct?
15:19 Fundamental Stability measures provide context; Nodal equations - Driving Point Impedance; Transfer functions - Return Ratio
17:34 Return Ratio and Return Difference – need to access internal transconductance
18:16 Driving Point Admittance : Kurokawa oscillation condition
19:37 Modern Return Ratio – Normalized Determinant Function (NDF)
20:58 Modern Driving Point Admittance – Auxiliary Generator (Y-AG) Kurokawa condition
21:29 True Return Ratio (TRR) external loop gain characterization
22:28 TRR assumes simple device model
23:54 TRR related to Driving Admittance
24:52 Loop Gain – a valuable intuitive design tool
25:39 Summary of Return Difference, Driving Point Admittance & Loop Gain
26:36 Unifying Stability Simulation using in-situ probing
27:02 Challenge: Each Stability Analysis requires a different setup
28:07 Tom Winslow introduction and reasons for inventing WS probe for unified stability analysis
31:46 WS probe is accurate under arbitrary levels of feedback
35:35 WS probe computes all stability figures of merit in a single simulation !
37:09 1 WSP simulation = 4 OscTest simulations
37:51 1 WSP simulation = 4 Middlebrook loop gain simulations
38:20 WSP simulation = Hurst loop gain simulation
38:48 1 WSP simulation = 4 Total Return Ratio simulations
39:16 WSP simulation = Normalized Determinant Function simulation
39:51 1 WSP simulation = 14 Driving Point Admittance simulations (1 simulation per node) in Auxiliary Generator method
40:58 Stability Analysis for Large Signal simulation
42:15 WS Probe extends Stability Analysis easily to nonlinear large signals
43:30 WS simulation simplifies stability analysis & deriving impedance/admittance measures
44:40 Demo of WS probe in ADS
46:55 Need to model feedback loop to detect instability
47:14 Electromagnetic RFPro analysis to identify potential feedback loops
47:45 Instability revealed under large signal excitation
48:33 Identifying direction of unstable feedback
49:47 Circuit-EM excitation to visualize and locate causes of unstable feedback
50:39 Output to Input unstable feedback identified
50:58 Output unstable feedback through ground loop identified
51:19 Fixing causes of instability by targeting feedback mechanisms
51:43 Verify instability fixes with EM visualization
52:06 Closing & Summary – WS probe comprehensively perform small/large signal stability analysis with a single setup to replace 28 traditional different simulations
53:50 Q&A
Apply for a Free Trial at keysight.com/find/mytrial.rfmw.vi
See Part 2 of 2 at youtu.be/Nmo_-K3vgo8
