Berry New South Wales and How to measure S Parameters

24th October 2016

Berry, New South Wales. Lovely little town surrounded by beautiful countryside.

Great Southern Hotel in Berry

Traditional House in Berry

The Old Post Office

All Roads Lead to Berry

y

Drawing Room Rocks

View from Drawing Room Rocks

Measuring S Parameters

• S11 and S21
• Measure magnitude and phase of incident, reflected and transmitted voltage signals
• Output is terminated in a perfect matched impedance Zo
• (Load that equals the characteristic impedance of the test system)
• Matched load impedance ensures no reflection
• S11 is equivalent to the input complex reflection coefficient or impedance of the DUT 
• S21 is the forward complex transmission coefficient. 
• Can measure S22 and S12 by placing source at port 2 and terminating port 1 in a perfect load 
• For packaging applications we are usually only interested with magnitudes, not phase, and can assume linear behaviour

Key Components 

• Source for stimulus
• Signal-separation devices
• Receivers that down convert and detect the signals
• Processor/display for calculating and reviewing the results

Output from Network Analyser

Need Test Fixtures

• Making quality RF measurements on devices with standard coaxial connectors is relatively easy. 
• Accurate measurements can be made using commercial calibration kits and standard error-correction routines found in most network analyzers 
• Devices without connectors are tough 
• Test fixture is needed to provide RF compatible electrical connection between the device and test equipment 
• In-fixture calibration standards are often required to achieve acceptable accuracy 
• Also mechanical constraints

Penang to Singapore to Sydney to Berry NSW and S Parameters for RF Packaging

18th October 2016

From Penang to Singapore to Sydney to Berry, New South Wales. A busy couple of weeks which is why the blog got delayed. 

Buddy Bears in Penang, USA, UK and UAE

Moldova has a sense of humour

Holland

Uzbekistan

Coming in to land in Sydney

Iconic Opera House

Iconic Bridge

Bigfoot to go up Coolangatta "Mountain" near Berry NSW

Shoalhaven River from Coolangatta Mountain

Ever wondered what those mysterious S Parameters are? 

Why do they keep on showing up in RF Packaging?

The “S” stands for “scattering”

Probably the most widely used measurements for RF packaging

Can be used to characterise the RF performance of a “black box” without knowing what is inside it

Why use S-parameters? 

Relatively easy to measure at high frequencies

Can measure voltage traveling waves with a vector network analyzer

Relate to familiar measurements (gain, loss, reflection coefficient etc) 

Most importantly  for RF package design and simulation S-parameters are easily imported and used for circuit simulations in electronic-design automation

S-parameters are the shared language between simulation and measurement

The Scattering (S)  Matrix

• Mathematical construct that quantifies how RF energy propagates through a multi-port network 
• Enables a complex network to be described as a simple "black box“ 
• For RF signal incident on one port, some fraction is reflected back out of the same port, some of it goes into that port and exits from one or more other ports 
• It may be amplified or attenuated 
• If the network has N ports the S-matrix will have N2 coefficients (S-parameters) 
• Each S parameter represents one possible input-output path.

S Parameters for two port network

• Note that S21 = b2/a1 is a measure of the output at port 2 as a function of input at port 1
• Only inject one signal at a time
• To measure S11, inject a signal at port 1 and measure its reflected signal
• To measure S21, inject a signal at port 1, and measure the output from port 2

• a and b  values be considered as complex  voltages representing both amplitude and phase
• Usually we are only interested in amplitude
• S-parameter amplitudes presented in one of two ways, linear magnitude or logarithmic based decibels (dB)
• Formula for decibels in this case is:
•  Sij(dB)=20 * log[Sij(magnitude)

S Parameters Matrix Representation

S Parameters are not the only way of representing networks but they are almost universally use in packaging applications

S Parameters:  Learn More

http://www.microwaves101.com/encyclopedias/s-parameters

http://www.ece.ucsb.edu/~long/ece145a/Notes4_Sparams.pdf

http://rf-mw.org/transmission_lines_and_distributed_systems_transmission_lines_using_s_parameters.html

Course and relaxation in Penang

4th October 2016

Forgot to mention last week the IEEE-IEM eETD Mini Colloquium held on 24th September at  PSDC in Bayan Lepas, Penang.

http://sites.ieee.org/malaysia-edmttssc/eetd-mini-colloquium/

http://www.psdc.org.my/

Two excellent speakers from Japan, the first Dr Hideto Hidaka, CTO of Renesas speaking about embedded flash memory for MCU applications, its history, technology and new developments. After lunch the second speaker Dr Hideto Hidaka, of Tokyo University described optical range finding techniques using smart image sensory.

My own talk was on Packaging and Reliability for MEMS, abstract below

In the last two decades MEMS devices have become ubiquitous in almost all aspects of our lives, particularly in the cars we drive and the phones we use. By modifying the fabrication techniques originally developed for integrated circuits, microscopic devices are created which match or exceed the performance of their conventional counterparts but are far smaller, lighter and cheaper. But MEMS devices present considerable challenges in packaging and reliability.

Unlike conventional IC chips, which can be considered as fairly robust, monolithic blocks, most MEMS have easily damaged, delicate moving parts which cannot withstand conventional IC packaging approaches. Moreover, many MEMS sensors need to be exposed to the outside world so unique packaging solutions are needed. Indeed packaging is usually a key part of the overall design and functionality of the device; it cannot be an afterthought.

MEMS can suffer from unique failure mechanisms that don’t affect conventional ICs, stiction, electrostatic charging, fatigue and wear are key examples.

The talk will highlight some of the packaging and reliability challenges, together with examples of solutions which have enabled MEMS devices to play such an important role in our lives.

The course on RF Package Technology : Principles, Issues and Challenges finished a week ago. Great feedback from the participants who came from big MNCs, Intel, Avago, Infineon, NI, and ON semiconductor. Would be great to get more participants from SMEs. 

Since then I have been relaxing in historic Georgetown, Penang.  Photos of some traditional houses