AT's Blog: Microelectronics Reliability, FA and more: 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)