The document describes a method for building an impedance matching network for a transistor using S-parameter data and optimization tools in ADS simulation software. The transistor of interest operates from 220-270 MHz, where reference designs are unavailable. Input and output impedances are extracted from S-parameter files. An existing matching network design at a nearby frequency is used as a starting point. Optimization replaces ideal components with real ones, achieving over 30 dB return loss while degrading slightly from the ideal simulation. The method demonstrates synthesizing a matching network when reference designs are unavailable.

1. Building Impedance Matching network based on S-Parameter
from manufacturer
Aizuddin Nuruddin, Tengku Azhar, Zharfan Hamdan, Khairom Nizam Mohamed, Ahmad Redzman
Wireless, Photonics and System Technology, MIMOS Berhad.
Technology Park Malaysia 57000 Bukit Jalil Kuala Lumpur
Email – aizuddin@mimos.my
Abstract: To maximise power transfer in a radio
frequency (RF) system, impedance matching is
necessary. Advance design tools such as those
available in Agilent Advance Design Software
(ADS) has greatly made the impedance
matching process simpler, faster, and more
accurate. In the absence of a reference design at
a particular non-popular frequency range, the
Optimize feature in ADS may be useful to build
the impedance matching network. This paper
describes the method of using this feature to
synthesise the impedance matching network for
the above mentioned frequency for the
MMZ09332BT1 from Freescale, using ideal and
real components based on the original s-
parameters provided by the manufacturer.
Index Term- Matching network, s-parameters.
I. Introduction
Impedance matching is often a part of the larger
design process for a radio frequency (RF) system.
Impedance matching is a network placed between a
load and source. Matching network is required to
make the impedance seen looking into the
matching network to be equivalent with the
characteristic impedance of the network, Zo. If the
source impedance, Zs, and the load impedance, ZL,
of a transmission system are not equal, reflection of
power will occur, such not all signal would be able
to be delivered to the load. Reflections are
eliminated on the transmission line by a matching
network. Impedance matching or sometimes
referred to as tuning is important for many reasons,
among others:
- Maximum power is delivered when the
source is matched to the load [1]
- Match of sensitive receiver components
(antenna, low-noise amplifier, etc.)
improves the signal-to-noise ratio of the
system by improving its noise
performance.
- Impedance matching in digital network
will reduce amplitude and phase errors,
thus contribute to better error vector
magnitude (EVM).
- Stability of amplifier is depending on the
source and load impedance. Power
amplifier works best at matched load and
source impedance
- Reliability of an amplifier is compromised
if there is mismatch between the load and
the source. High reflected power back to
the source from the load will heat up
power amplifier. At the same time,
mismatch in the circuit could make the
amplifier to operate with poor efficiency
which means higher circulating current.
Amplifier in turn will work with higher
junction temperature and thus
compromising long term reliability.
Several types of practical matching networks are
available [2] and the selection is normally based on
what is important for the designer. Factors that may
be important in the selection of a particular
matching network include the following:-
- Complexity - A simpler matching network
is usually cheaper, more reliable, and less
lossy than a more complex design.
- Bandwidth- In many applications, it is
desirable to match a load over a band of
frequencies as modern applications require
a wideband of operation. This will
correspondingly increase design
complexity.
Whilst impedance matching can be tedious and
lengthy process in the past, advance in computer-
aid made the process simpler, faster, and more
accurate. One of the design tools that is available
to a designer is Agilent ADS (Advance design
system). Advance design system offers multiple
tools and features to help designer build match
network.
II. Background
MMZ09332BT1 is a Heterojunction Bipolar
Transistor (InGaP HBT) manufactured by
Freescale Semiconductor. It covers frequency of
operation from 130 to 1000 MHz. Most of the
time, a designer will be supplied with a reference

2. design that he or she does not need to build a match
circuit at frequency of interest. Normally these
reference designs are available for operation in
popular frequency. In rare cases however,
designer will need to work on non-popular
frequency where such reference design is not
available. This paper will present a method to
build an impedance matching network using
Optimize feature in Agilent ADS simulation
software. In this particular paper, authors
specifically work on Freescale MMZ09332BT1 as
part of a transmitter line up. MMZ09332BT1 is
used as a tune circuit for the transmitter. The
frequency of interest is 220 MHZ until 270 MHZ.
The bandwidth is 50 MHZ; as such the match
network will need to consider a topology that will
allow for wideband of operation.
III. Method
It is very clear from the manufacturer datasheet that
220MHz to 270 MHz is not a popular frequency.
As such both the input and output match network
need to be built independently. Freescale however
make the s-parameter data available to designer.
The authors take the below approach to build the
match network for both input and output of the
device
i. Get the s-parameter data from
manufacturer, extract input and output
impedance
ii. From datasheet, the reference design with
the closest frequency of operation is
picked for reference
iii. Perform optimization using ideal
component
iv. Plot all the paramaters again: S21, S22,
S11
v. Replace ideal components with real
components in simulation
vi. Plot all the paramaters of simulated value
with real components: S21, S22, S11
Fig. 1 is the S2P file that is provided by
manufacturer. It details out the test condition and
measurement reference plane as a guide for
simulation purpose.
Fig. 1: S2P file for MMZ09332BT1
A quick look into the gain performance of the
device is as in Fig. 2 below. The device maximum
available gain is typically at 30.5 dB.
Fig. 2: Device performance across frequency
Fig. 3: S22 and S11 across frequency
The gain of the device is quite close to typical, but
a quick assessment on the small signal gain S21,
shows that it is not at its full potential. The return
loss S11 and S22 (Fig. 3) for both input and output
are poor and this can result in amplifier instability
as well as poor reliability.
From manufacturer s-parameter file, the output and
input impedance information is extracted.
! Copyright-Freescale Semiconductor, Inc., 2015
! 08/24/2015
! Rev.0
! MMZ09332BT1 S-Parameters
! 10 MHz-4 GHz
! VCC1 = VCC2 = VBIAS = 5 Vdc, ICC1Q = 80 mA, ICC2Q = 60 mA
! Measurement Reference Plane: RF pins at edge of package body
!
# hz S ma R 50
! freq magS11 angS11 magS21 angS21 magS12 angS12 magS22 angS22
!
10000000 0.677852185 178.77844
0.0193547003 -96.449257 0.000119438049 80.376389
1.17461159 -32.7024
12493750 0.69197728 178.34561
0.0402415083 -98.440826 0.000469939229 -15.212961
1.24055312 -43.394432
14987500 0.687577474 176.9538
0.0749411236 -104.41002 0.000478690986 -39.428894
1.33472251 -53.772949
17481250 0.685460084 176.89978
0.127804693 -109.608 3.98978506e-005 68.907753
1.42609719 -65.113762
19975000 0.676563392 175.89542
0.198030576 -115.01767 0.000122292029 129.52623
1.4890173 -77.836777

3. Fig. 4: S2P simulation for MMZ90332BT1
Fig. 5: Extract of impedances from Smith Chart
The input and output impedances at 3 frequencies
are as in Table 1 below
Frequency
(MHz)
220 250 270
Impedance
(ohms)
18.2+j*21.1 22.4+j*24.5 26.4+j*26.9
1(a)
Frequency
(MHz)
220 250 270
Impedance
(ohms)
5.7-j*3.3 5.9-j*2.3 5.9-j*1.8
1(b)
Table 1: (a) Input and (b) Output impedances
The next step is to perform optimization for both
input and output impedance. The configuration of
match network can be in many forms. Agilent
ADS simulation offers at least 2 tools (Wizards) to
synthesise the match network at any impedance;
Smith Chart impedance matching and component
based/PCB impedance matching [2][3][4]. Both of
these methods offer unique control to a designer.
Designer can design for best bandwidth or simplest
network, depending on the desired objective. Very
often, a match network is a trade-off between
bandwidth, loss in network and complexity [2][5].
In the method presented in this paper, designer is
using a rather non-conventional method whereby
match network is synthesized from a known
network based at different band of frequency. This
known network is used as a starting value for
Agilent simulation to start from. From MMZ09332
datasheet, the closest available match network with
a reference design is at 136-174 MHz.
Fig. 6: MMZ09332BT1 match network [6]
Table 2: MMZ09332BT1 match components [6]
The values for input and output match are copied
into Agilent ADS simulation. Simulation is
performed and the result is compared to the
measured result obtained from data sheet. Fig. 7, 8
and 9 below are the performance data according to
datasheet.
Fig. 7: S11 versus Frequency [6]

4. Fig. 8: S22 versus Frequency [6]
Fig. 9: S21 versus Frequency [6]
Fig. 10: Simulation at 174MHz
Fig. 11: Response with Freescale S-parameters
Result from datasheet (Fig. 7, 8 and 9) and
simulated responses based on s-parameter provided
by manufacturer in Fig. 11 are similar. Peak gain is
at around 150 MHz with S21 of around 33 dB in
both responses. Return loss for both input and
output are also similar in value and response.
The match network circuit from 136 – 174 MHz as
in the datasheet is copied to Agilent ADS and the
values are used as starting value for simulation.
Fig. 12: Simulation at 250MHz

5. Simulation is set up to run as above (Fig. 12). The
goal is set to a return a loss of less than -30 dB in
both output and input. Simulation return a set of
values and the result obtained as in Fig. 13 below.
Fig. 13: Response versus Frequency with unmatch
(S21) and match (S56) impedance network
Fig. 14: Return loss of unmatch impedance at
i/p(S11) and o/p(S22) as compared to return loss
of match impedance at i/p(S66) and o/p(S55).
Output return loss is about 35 dB better comparing
between before and after match network. Un-
match circuit has about -5dB output return loss
whilst the match circuit has about -40 dB of return
loss. In input, there is an improvement of 22 dB in
return loss. Unmatch circuit is about -8 dB in
return loss whilst circuit with match network is
about -30 dB. The gain of the circuit has also
improved by around 7 dB. The circuit is re-
simulated with actual value made available by
component manufacturer. This is done to ensure the
circuit is still performing as expected when taking
account of stray element in real components.
Fig. 15: Response of ideal compare to real
components
Fig. 16: I/p and o/p return loss of ideal compare to
real components
Simulation above predicts that there is a difference
in performance comparing simulation with ideal
and real components. Degradation in performance
however is acceptable. The simulated value in the
match network is good for PCB fabrication.
IV. Conclusion
Based on the method above, match network for a
particular frequency for a particular device can be
synthesised using known matched network at
different frequency although there is a slight
degradation of performance in simulations when
using real components. Hence Agilent ADS
simulation tool is a useful method to synthesise an
impedance matching network at a particular non-
popular frequency (250MHz) for MMZ09332BT1
based on its known S parameters at closest
frequency range (136-174MHz). This method of
using the same tool can also be explored for
synthesizing match network for other RF devices.
In addition, other advance design sytem simulation
tools with similar capability and features may also
be explored to synthesise and build the impedance
matching networks of RF devices.

6. REFERENCES
[1] C. Bowick, RF Circuit Design, 1st ed.,
Howard W. Sams & Co. Inc., Indianapolis,
Indiana, USA, 1982.
[2] Vendelin, Pavio and Rohde, Microwave
Circuit Design Using Linear and Nonlinear
Techniques, 2nd
ed., John Wiley & Sons Inc.,
USA, 2005.
[3] Agilent ADS Quick Start 2011.
[4] Smith-Chart Software and Related
Documents.http://www.fritz.dellsperger.net/smi
th.html. Retrieved on 3rd
November, 2020.
[5] Frederick Ray I. Gomez, “Design of
Impedance Matching Networks for RF
Applications,” Asian Journal of Engineering
and Technology (ISSN: 2321 – 2462) Vol. 06 –
Issue 04, September 2018.
[6] Freescale Semiconductor, Technical Data
Doc. Number:MMZ09332B Rev 0, 8/2015.