Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
1
RF Front End Wireless Receiver for 2.4 Ghz
Band IEEE 802.15.4 ZigBee Standard
Rohan Shah, Adam Zander

Abstract—This paper describes the design of the RF front end
of a ZigBee receiver for wireless networks. The receiver consists of
a band pass filter, low-noise amplifier, a high gain amplifier, a
balanced down-conversion mixer and a low pass filter. The
receiver operates at a frequency of 2.4 Ghz. The low-noise
amplifier is able to achieve a minimum noise figure of 19 dBm. The
band pass filter is a third order Chebyshev filter with improved
attenuation. The low noise amplifier is used to reduce the inherent
noise in the receiver and to ensure efficient power consumption of
the receiver. Simulation results show that the receiver can achieve
a sensitivity level of -90 dBm and a third order intercept (IIP3) of
–20 dBm.
Index Terms—IEEE 802.15.4, RF front end, Low-Noise
amplifier (LNA), mixers, Band Pass Filter (BPF), Low Pass Filter
(LPF), Advanced Design System (ADS), Radio Frequency (RF),
Signal to Noise Ratio (SNR), Noise Figure (NF)
level of background noise. Certain components in an RF
signal chain can degrade the SNR due to the added noise
provided by the components. Noise factor (F) provides a
measurement of the degradation of the SNR. Noise Figure
(NF) provides us with the decibel (dB) value of the noise
factor for a device. It is simply the measured input SNR
divided by the output SNR. The specification says that the
maximum noise factor for a ZigBee device is 19dB. Since the
noise factor is relaxed, the required SNR is reduced,
increasing the sensitivity for a given bit error rate [4]. The
noise factor of our receiver is given by:
𝑁𝑜𝑖𝑠𝑒 𝐹𝑎𝑐𝑡𝑜𝑟 (𝐹) =
𝑆𝑁𝑅𝑖
𝑆𝑁𝑅𝑜
=
𝑆𝑖
.
1
𝑘𝑇𝑜 𝐵𝑊 𝑆𝑁𝑅𝑜
(1)
where Si is the input signal power, k is Boltzmann’s
constant and To is the room temperature.
𝑁𝐹 = 𝑆𝑖 (𝑑𝐵𝑚) + 174 − 10 log10 𝐵𝑊 − 𝑆𝑁𝑅𝑜 (𝑑𝐵) (2)
I. INTRODUCTION
T
HE IEEE 802.15.4 ZigBee standard is a low-power, lowdata rate, and short range wireless communication
standard. ZigBee is a specification for communication in a
wireless personal area network (WPAN). WPAN is a network
used for communication over a small area such as a home or a
personal workspace. ZigBee supports three operating
frequencies: 868 Mhz, 915 Mhz and 2.4 Ghz. The 2.4 Ghz band
has 16 frequency channels ranging from 2.405 Ghz to 2.48 Ghz
with 5 Mhz spacing. The duty cycle is defined as the time
percentage in a transmission session when a device is active.
ZigBee operates at a duty cycle of less than 1%. ZigBee can be
used to connect nearby devices wirelessly at a very low cost.
Applications of ZigBee include industrial automation, health
care monitoring, lighting control systems and efficient sensors
[4].
In this paper, we describe the general design of the RF frontend of a ZigBee receiver operating at 2.4 Ghz. We have defined
each component used in the design and have included a brief
overview of the design process associated with it.
II. ZIGBEE SPECIFICATIONS
A. Sensitivity
Signal-to-noise ratio (SNR) is a measure used in
engineering that compares the level of a desired signal to the
Project supported by EECS 411: Microwave Circuits. The report was
submitted on Monday 16th December 2013 at 5pm to Professor Amir
Mortazawi.
The minimum sensitivity for a ZigBee device is -92dB for
the 868 and 915MHz bands and -85dB for the 2.4GHz band.
The maximum sensitivity for all three bands is -20dB.
B. Third Order Intercept Point (IIP3)
If we inject a two-tone input voltage signal into the system,
it will consist of two frequencies ω1 and ω2 given by:
`
𝑣𝑖 = 𝑉0 (cos(𝜔1 𝑡) + cos(𝜔2 𝑡))
(3)
The output consists of different harmonics of the same tone
called intermodulation products. If ω1 and ω2 are close to each
other, the third order tones (2ω1 - ω2) and 2(ω2 - ω1) will not
be easily filtered and might cause distortion of the output
signal [6]. This effect is called third order intermodulation
distortion.
As the input voltage V0 increases, the voltage associated
with the third order products increases as V03. Hence the
output power of third order products increases as the cube of
the input power (Fig. 1). The hypothetical intersection point
where the first and third order powers would be equal is called
the third order intercept point denoted as IP3. It may be
specified as an input power level (IIP3) or output power level
(OIP3).
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
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III. THEORY & DESIGN ARCHITECTURE
A. Block Diagram
Fig. 2: Block Diagram of our ZigBee Receiver
Fig. 1: Third Order Intercept diagram for estimation of IP3
C. Dynamic Range and Battery Life
Battery life is one of the most important criteria for an
effective ZigBee device. In many applications, one can’t
afford to make regular trips back to a sensor to change the
battery. Most ZigBee data are handled using a beaconing
system where the sensor wakes up at specific intervals, checks
for the beacon, exchanges data, and then goes back to sleep.
ZigBee devices operate across a short range, which allows
the transmit power to be only 1mW or 0dbm. A ZigBee
receiver should be able to receive an input level up to -20dBm.
Since the transmit power requirement is 1mW or 0dbm, the
typical operating range of a ZigBee application is anywhere
from 10 to 20m. The power saving technique and low
transmit/receive power allows for low power consumption and
battery life of ZigBee devices to range from months to years.
The maximum permitted power level at the receiver input is
-20 dBm which leads to a dynamic range 65 dB or more.
Dynamic Range is given by:
2
𝐷𝑅 = (𝑂𝐼𝑃3 − 𝑁𝑜 )
(4)
3
where No is the output noise power and OIP3 is the third
order intercept point of the output power level of the receiver.
D. Summary
Table 1 below provides a summary of the specifications of
the IEEE 802.15.4 ZigBee receiver.
Table 1: ZigBee receiver specifications
Name
Value
Frequency
2400-2483.5
Band (MHz)
# of Channels
16
Channel
Spacing (MHz)
Data Rate
(Kbps)
Chip Rate
(Kchips/s)
Modulation
Scheme
Packet Error
Rate
5
250
2000
O-QPSK
< 1%
Name
Receiver
Sensitivity
Max. Receiver
Input
Jamming Res.
(adj. Ch.)
Jamming Res.
(alt. Ch.)
Rx to Tx turnaround time
Preamble field
for Synch.
Accuracy
Value
-85dBm
-20dBm
0dB
30dB
12 symbols
32 binary zeros
± 40 ppm
Each block from Fig. 1 was designed and constructed in
Advanced Design System (ADS). We used ADS because it
offers different tools that enable us to simulate our design over
a wide range of physical parameters. We were not required to
design a local oscillator for our receiver.
Table 2: Characteristics of a well-designed ZigBee receiver
Band Pass Filter
Low Noise
Amplifier
High Gain
Amplifier
Mixer
Total
Gain (dB)
> -5
> 10
NF (dB)
< 10
< 3.5
IIP3 (dBm)
N/A
>0
> 15
<5
>0
> -10
> 10
< 12
< 20
> -15
> -20
B. Receiver Operation
The incoming signal enters the receiver system via the
antenna. It passes through the BPF which is used to filter out
all the frequencies outside the operation range of 2.32-2.48
Ghz. The filtered signal is amplified by the LNA. The LNA
also increases the SNR of the input signal. The output signal
from the LNA is passed through a HGA that provides
additional gain. The final stage of the receiver is the mixer.
The mixer is used to down convert the signal from the HGA to
a lower intermediate frequency (IF) of 100 Mhz, which is then
sent to the IF processor. Our receiver consists of only front
end components; hence, all the IF components that follow are
beyond the scope of this project.
C. Substrate Information for Mircostrip lines
We designed all components and networks using microstrip
transmission lines because they provide the best
approximation of realistic transmission lines. We used the
same substrate specifications for the microstrip lines in all
stages of the design. The substrate used has the same
characteristics as the RT/duroid® 6035HTC High Frequency
Laminate. The substrate characteristics are:
εr = 3.55
tanδ = 0.002
H = 32 mil = 0.81 mm
T = 35 μm
σ = 5.8e7 Siemens/m
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
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IV. BAND PASS FILTER
A. Circuit Design
The BPF is the first stage of the receiver which is used to
filter the incoming RF signal from the antenna as shown in
Fig. 2 It requires 0dB attenuation at 2.4 Ghz ± 5 Ghz for the
adjacent channel and 20 dB attenuation for the alternate
channels. We chose to design a 0.5 dB equal-ripple Chebyshev
filter using cascaded coupled microstrip transmission lines.
The order of our BPF was N = 3 and we used (N+1) = 4
transmission lines to construct it on ADS.
𝜋∆
𝜋∆
𝑍0 𝐽1 = √ , 𝑍0 𝐽𝑛 =
2𝑔
2√𝑔
(5)
𝑍0𝑒 = 𝑍0 [1 + 𝐽𝑍0 + (𝐽𝑍0 )2 ]
(6)
𝑍0𝑜 = 𝑍0 [1 − 𝐽𝑍0 + (𝐽𝑍0 )2 ]
(7)
𝑛 𝑔𝑛−1
1
We used (5), (6) and (7) to calculate the physical parameters
for an ideal coupled line band pass filter. Using these
parameters from Table 3, we designed the coupled microstrip
BPF (Fig. 3). The gn values refer to the element values that are
obtained from existing data on equal-ripple filters (Table 3).
Table 3: Physical Parameters of coupled microstrip lines used in the BPF
n
1
2
3
4
gn
1.5963
1.0967
1.5963
1.0000
Z0e (Ω)
60.01
52.05
52.05
61.16
Z0o (Ω)
42.58
48.103
48.103
48.10
The results show that the attenuation of the microstrip BPF
is almost as good as that of the ideal BPF at 2.4 Ghz (Fig. 4 &
5). The filter met our requirements and worked well.
Fig. 5: S21 (transmission coefficient) of our coupled microstrip line BPF
C. Momentum Simulation
Momentum is a tool within ADS that lets us simulate our
design in the real world. Momentum simulated our design
using the laws of physics as in the real world to ascertain its
functionality. We will provide details and simulations results
of our Momentum BPF layout in this section.
Fig. 6: Layout of our coupled line BPF in Momentum. Physical parameters are
listed in Table 3.
Fig. 3: Schematic of BPF using coupled micro-strip lines
B. Circuit Simulation
Fig. 7: S21 (transmission coefficient) of Momentum BPF
Our Momentum BPF works well at the design frequency of
2.4 Ghz (Fig. 7).
V. LOW NOISE AMPLIFIER
Fig. 4: S21 (transmission coefficient) of Ideal coupled microstrip line BPF
A. Circuit Design
Following the RF band-pass filter is a Low Noise Amplifier
(LNA). LNA’s are implemented in receivers to increase the
incoming signal power, while adding minimal noise [1]. We
used the ATF-331M4 GaAs transistor from Avago for our
LNA. To achieve minimal noise, we had to create appropriate
input and output matching networks (Fig. 9). The input
matching network consists of a series microstrip transmission
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
4
line and an open microstrip stub in shunt. This input matching
network of the LNA requires a reflection coefficient (Γs) that is
equivalent to the optimized reflection coefficient (Γopt).
Reflection coefficient is the ratio of reflected power with
respect to incident power. Γopt is the optimized reflection
coefficient for minimal noise and its value is provided in the
transistor’s data sheet.
Fig. 11: Noise Figure of LNA
Fig. 8: General Transistor Amplifier Circuit with matching networks
The output matching network consists of a series microstrip
transmission line and a short microstrip stub in shunt. This
output matching network must be designed to have a reflection
coefficient (ΓL) that is equivalent to the complex conjugate of
the reflection coefficient looking back into the transistor (Γout)
(Fig. 8). This design technique is used to achieve maximum
gain and have overall good matching.
Fig. 11 above shows the NF of the LNA (nf(2)) alongside
the minimal NF of the transistor (NFmin). Ideally we want
nf(2) = NFmin. However, to achieve the desired gain of the
LNA, we had to increase its NF.
C. Momentum Simulation
The Momentum layout shown in Fig. 12 below only
includes the input and output matching networks. These
networks must be spaced out appropriately to provide room
for the transistor to fit.
Fig. 9: Schematic of LNA with input and output matching networks
B. Circuit Simulation
Once the LNA was fully designed, we ran an S-parameter
simulation in ADS. From the S-parameter simulation, we were
able to obtain the overall gain and NF of the LNA across a
wide frequency range (Fig. 10 & 11).
Fig. 10: Gain of LNA
The overall gain of the LNA corresponds to its S21 value.
The S21 value is the red graph line in Fig. 10. The blue graph
line represents the maximum allowable gain the transistor can
achieve (Fig. 10). We can see that the overall gain of the
transistor almost equals the maximum allowable gain at our
designed frequency of 2.4GHz.
Fig. 12: Momentum layout of matching network for LNA
The momentum simulation results for overall gain and NF
are very similar to our S-parameter microstrip results.The gain
and NF of the Momentum Simulation are shown in Fig. 13
and 14.
Fig. 13: Gain of Momentum LNA
The overall gain of the LNA (S21) is very similar to the
overall gain obtained from the S-parameter microstrip
simulation. The peak at 2.4GHz tells us that we achieved good
matching for our LNA (Fig. 13).
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
5
B. Simulation
Similar to the LNA, the HGA was simulated using an Sparameter simulation in ADS. From the S-parameter
simulation, we can attain values for the HGA gain and NF
over a large frequency range (Fig. 16 & 17).
Fig. 14: Noise Figure of Momentum LNA
The NF of the Momentum simulation (nf(2)) was very low
at the operating frequency of 2.4GHz. This value is very
similar to the NF obtained in the microstrip S-parameter
simulation.
D. Summary of Results
The results we simulated met the ZigBee wireless standards.
Table 4 below compares our LNA values to the desired LNA
values for a ZigBee receiver.
Fig. 16: Gain of HGA
The gain of the HGA is much higher than the LNA. The S21
value is close to the maximum available gain at 2.4GHz,
which means there is good matching at that frequency.
Table 4: LNA Simulation Results
Gain (dB)
ZigBee
Microstrip
Momentum
12
13.56
13.79
Noise
Figure (dB)
3.50
1.60
1.79
Requirement
Met?
Yes
Yes
VI. HIGH GAIN AMPLIFIER
A. Circuit Design
After the LNA, the signal travels through a high gain
amplifier (HGA). A HGA is implemented to provide
substantial power gain to the signal (Fig. 15). The HGA
should also have low noise, but it is not as important as it is
for the LNA. We used the ATF-531P8 transistor from Avago.
To provide the maximum gain possible, the input and
output matching networks must be designed for simultaneous
conjugate matching. Simultaneous conjugate matching is a
design process to achieve optimal matching because it takes
both the input and output matching networks into account at
the same time. Simultaneous conjugate matching was
performed on ADS using a simulation tool. This simulation
tool provided us with the proper ΓS and ΓL values to design
our input and output matching networks. The input and output
matching networks were designed using series microstrip
transmission lines with open circuited stubs. After achieving
optimal gain and matching, we tuned the lengths of the
transmission lines and stubs to bring down the NF.
Fig. 15: Schematic of HGA with input and output matching networks
Fig. 17: Noise Figure of HGA
The NF for the HGA is still very good. The low NF of the
HGA will improve the accuracy of the receiver as a whole.
C. Momentum
The Momentum layout only includes the input and output
matching networks. These networks must be spaced out
appropriately to provide room for the transistor to fit (Fig. 18).
Fig. 18: Momentum layout of matching network for HGA
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
The momentum simulation results for overall gain and NF
varied slightly compared to our S-parameter microstrip results
(Fig. 19 & 20).
6
provides the proper down conversion from RF signal to the IF
signal. The down conversion of the mixer subtracts the LO
frequency from the RF frequency to get the IF signal. The IF
signal we used for our ZigBee receiver is 100MHz. This
frequency makes it easier to filter out the 16 ZigBee channels.
𝑓𝑅𝐹 = 𝑓𝐿𝑂 ± 𝑓𝐼𝐹
(8)
We first designed a 3dB branchline coupler using ideal
transmission lines. The S-parameters for a branchline coupler
are given by:
0
𝑗
[𝑆] = − [
√2 1
0
1
Fig. 19: Gain of Momentum HGA
The gain of the HGA was lower in the momentum
simulation than it was for the microstrip S-parameter
simulation. The boundary conditions of the HGA had more
significant affect as oppose to the LNA.
𝑗
0
0
1
1
0
0
𝑗
0
1]
𝑗
0
(9)
Using the S-parameters matrix (9), we can determine the
characteristic impedance of all the transmission lines (ZS and
ZP) within the coupler (Fig. 21).
Fig. 21: Schematic of 3dB Branchline Coupler using microstrip lines
𝑆21 = −
Fig. 20: Noise Figure of Momentum HGA
The NF of the momentum simulation was slightly higher
than the NF for the microstrip S-parameter simulation (Fig.
20). Both values are extremely good for a HGA.
D. Summary of Results
We plotted the stability factor and stability measure value of
the amplifier. Since the stability factor was greater than 1 and
the stability measure was greater than 0, the transistor was
stable. Our HGA meets all our design specifications (Table 5).
Table 5: HGA Simulation Results
Gain (dB)
ZigBee
Microstrip
Momentum
>15
20.38
15.12
Noise Figure
(dB)
<5
1.21
1.62
Requirement
Met?
Yes
Yes
VII. DOWN-CONVERSION MIXER
A. Circuit Design
The last stage of our design was a balanced mixer
consisting of a branchline coupler with two diodes. The two
diodes provide non-linearity to the system. This non-linearity
𝑗𝑍𝑠
𝑍0
,
𝑆31 = −
𝑍𝑠
𝑍𝑝
(10)
Using (10) we obtain ZS = 35.355 Ω and ZP = 50 Ω. We
implemented diodes in our circuit after building the coupler.
The diode we used was the HSCH-53xx Series Diode. It had
to be biased into its non-linear region in order for the mixer to
work. We designed a bias network which included dc feedlines (large inductors) and dc blocking caps (large capacitors).
The bias network allowed us to apply a bias current to each of
the diodes. From the equations below, we obtained an ideal
bias voltage of 0.1V.
At the end of our mixer is a Low Pass Filter (LPF)
comprised of a series inductor between two shunt capacitors.
The LPF filters out all the other signals generated by the mixer
except for the IF signal. We were not required to design the
LPF, but have included it in our circuit to provide better
matching conditions for the mixer.
B. Circuit Simulation
We ran a Harmonic Balance simulation in ADS to examine
the performance of the mixer. An S-parameters simulation will
not work for the mixer because the mixer is a non-linear
device. For the Harmonic Balance simulation, we had an input
RF power of -25dBm and an LO power of 9dBm. We acquired
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
7
results for down-conversion loss, NF, and IIP3. We used the
data in Fig. 22 to calculate the conversion loss of our mixer.
Fig. 23: Momentum layout of branch line coupler used in mixer
Fig. 22: RF Input Power and IF Output Power
We selected an input RF power (P RF) of -25dBm. The
output IF power is -32.583dBm.
We ran the momentum simulation to obtain the conversion
loss, NF, and IIP3 value to compare with the microstrip
Harmonic Balance simulation. We used the data in Fig. 24 to
calculate the conversion loss.
Conversion Loss = IF power – RF Power = -7.583dBm
Since the mixer is passive, the NF requirement is more
relaxed as opposed to that of the amplifiers. Since the mixer is
farther from the antenna, its NF has less of an impact of the
overall NF of the system.
Table 6: Output Noise Figure
Output Frequency
100 Mhz
Noise Figure (NF)
6.934 dB
Table 6 above shows the NF of the down-conversion mixer.
Since the mixer is comprised of mostly passive components,
the NF is almost equivalent to the conversion loss.
We used a special design guide on ADS to comprise the
IIP3 value of the mixer (Table 7).
Table 7: OIP3 and IIP3 values for mixer
OIP3 (dBm)
IIP3 (dBm)
9.485
17.941
Carrier- IMD
ratio (dB)
83.904
LO Power
(dBm)
9
Fig. 24: RF Input Power and IF Output Power
Conversion Loss = IF power – RF Power = -8.515dBm
The conversion loss of the momentum simulation is slightly
lower than the value we obtained from the microstrip
Harmonic Balance simulation.
Table 8: Output Noise Fig.
C. Momentum Simulation
After performing all the microstrip Harmonic Balance
simulations, we ran the corresponding momentum simulation.
We could only generate a layout for the branchline coupler,
since it was the only section of the mixer than contained
transmission lines (Fig. 23).
Output Frequency
100 Mhz
Noise Figure (NF)
7.142 dB
Table 9: OIP3 and IIP3 values for mixer
OIP3 (dBm)
-2.76
IIP3 (dBm)
5.7
The NF of the momentum simulation is very similar to the
NF of the microstrip Harmonic Balance simulation (Table 8 &
9). However, the IIP3 value is much lower. Lower IIP3 is
undesired because background signals could affect the desired
signal.
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
8
D. Summary of Results
Our passive mixer meets our receiver design specifications
(Table 10). Active mixers use transistors to provide a
conversion gain instead of a conversion loss. We designed the
HGA to compensate for the loss of gain.
The conversion gain was less than the theoretically
calculated gain for the entire front-end receiver. This low
conversion gain could be caused by worse matching
conditions as a result of cascaded stages. The NF results of the
entire receiver are displayed below in Table 11.
Table 10: Mixer Simulation Results
Table 11: Noise Figure for entire receiver
ZigBee
Microstrip
Momentum
Conversion
Loss
(dBm)
>-10
-7.58
-8.52
Noise
Figure
(dB)
<12
6.93
7.14
IIP3
(dBm)
Requirement
Met?
>-10
17.9
5.7
yes
yes
Output Frequency (MHz)
100
Noise Figure (dB)
5.15
Expected NF = 1.66 + (1.60-1)/(.59) + (1.21-1)/(.59*23.82) +
(6.93-1)/(.59*23.82*109.07)
Expected NF = 2.70
VIII. FRONT END RECEIVER SIMULATION
We connected all the components together according to the
block diagram arrangement (Fig. 2). In this section, we will
discuss the simulation results of each stage and the challenges
we faced in the design process.
A. Simulation
We first cascaded the microstrip BPF, LNA, HGA, and
mixer circuits together. To simulate the entire circuit, a
Harmonic Balance simulation was performed because of the
nonlinearity of the mixer. We simulated the gain, NF, and IIP3
for the entire circuit (Fig. 25). The gain for this simulation
corresponds to the conversion gain.
Expected NF (dB) = 10*log(2.70) = 4.31dB
The actual NF was slightly greater than what was expected
for the cascaded system. However, the NF is still very low.
From the equation above, we can see that the NF from the
mixer had little to no effect of the overall NF value. The IIP3
results of the entire receiver are displayed below in Table 12.
Table 12: Noise Figure for entire receiver
OIP3 (dBm)
0.44
IIP3 (dBm)
-16.7
The IIP3 was affected the most when we cascaded the
components of the ZigBee receiver. The IIP3 decreased
considerably, which is undesirable. Although it decreased, it
remained above the threshold for the ZigBee protocol.
B. Momentum Layout Simulation Results
After completing the simulation results for the entire
microstrip schematic, we cascaded all of our momentum
layouts for the BPF, LNA, HGA, and Mixer. We then ran a
Momentum simulation to obtain the down-conversion gain, NF,
and IIP3 results for the entire Momentum schematic (Fig. 26).
Fig. 25: Conversion Gain of Entire System
Conversion Gain = IF power – RF power = 20.458 dBm
𝐸𝑥𝑝𝑒𝑐𝑡𝑒𝑑 𝐶𝑜𝑛𝑣𝑒𝑟𝑠𝑖𝑜𝑛 𝐺𝑎𝑖𝑛(𝑑𝐵) = 𝐺𝑎𝑖𝑛(𝐵𝑃𝐹) +
𝐺𝑎𝑖𝑛(𝐿𝑁𝐴) + 𝐺𝑎𝑖𝑛(𝑀𝑖𝑥𝑒𝑟)
(11)
Exp. Gain = -2.37dB + 13.56dB + 20.38dB – 7.58dB = 24dB
Fig. 26: Conversion Gain of Entire System
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
Conversion Gain = IF power – RF power = 17.85 dBm
Expected Conversion Gain (dB) = Gain(BPF) + Gain
(LNA) + Gain (HGA) + Gain (Mixer)
Expected Conversion Gain = -3.40dB + 13.79dB + 15.12dB
– 8.52dB
Expected Conversion Gain = 17 dB
The conversion gain of the momentum simulation matched
our expectations. The conversion gain was less than the
microstrip simulation because of the difference in HGA gain.
The NF results we obtained from our Momentum simulation are
shown below in Table 13.
Table 13: Noise Figure of Entire System
Output Frequency
100 Mhz
Noise Figure (NF)
15.55 dB
Expected NF = 1.96 + (1.79-1)/(.56) + (1.62-1)/(.56*23.79)
+ (7.14-1)/(.56*23.79*32.5) = 3.43
Expected NF (dB) = 10log(3.43) = 5.35dB
The NF that was measured was much higher than the
expected NF from our calculations (Table 13). This poor result
could be due to the discontinuities between different stages of
the receiver. The measured NF still meets the ZigBee standard.
Table 14: OIP3 and IIP3 of Entire System
OIP3 (dBm)
1.93
IIP3 (dBm)
-7.11
The IIP3 value we attained from the momentum simulation
was much better than our IIP3 from the microstrip harmonic
balance simulation (Table 14).
C. Summary
To have a fully functioning ZigBee receiver, the simulation
results we achieved for the entire cascaded system must meet
the overall ZigBee standard. All the components in the
cascaded system were necessary to meet these standards.
Table 15: Overall Receiver Specifications
Gain (dB)
ZigBee
Microstrip
Momentum
>15
20.46
17.85
Noise Figure
(dB)
<19
5.15
15.55
IIP3 (dBm)
>-20
-16.7
-7.11
We have exceeded the standards specifications for a ZigBee
front-end receiver (Table 15). The device can now be sent to a
chip manufacturer to be fabricated and used.
9
IX. CONCLUSION
We were tasked to design and simulate a ZigBee receiver
using ADS. To design each stage of the ZigBee receiver, we
used the knowledge obtained from our EECS 411 lectures and
laboratory assignments. After designing, we cascaded all the
stages together and ran simulations to see if our receiver met
the ZigBee specifications. Based on our simulation results, we
have completed our goal of designing and simulating a frontend ZigBee receiver.
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
10
APPENDIX
The entire circuit schematics are shown below:
Fig. 27: The ADS schematic of the Balanced Mixer using Microstrip Transmission Lines and Non-Ideal Lumped Components
BPF
LNA
HGA
Mixer
Fig. 28: The full, cascaded ADS schematic of a Front-End ZigBee Receiver using Microstrip Transmission Lines
BPF
LNA
Fig. 29: The full, cascaded Momentum Layout of a Front-End ZigBee Receiver
HGA
Mixer
Shah & Zander, ZigBee Receiver Design, EECS 411, University of Michigan Ann Arbor, Fall 2013
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Wolfram Kluge et al.,”A Fully Inegrated 2.4-Ghz IEEE 802.15.4Compliant Transceiver for ZigBee Applications” IEEE J. Solid-State Circuits,
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[2] Amr Amin Hafez et al.,”Design of a low-power ZigBee receiver frontend for wireless sensors” Microelectronics Journal, vol. 40, pp. 1561-1568,
2009
[3] Liu Weiyang et al.,”A low power 2.4 Ghz transceiver for ZigBee
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[6]
David M. Pozar,”Microwave Engineering”, 4th edition, 2005
[7] Antonio Liscidini,”Single stage RF quadrature front-end receivers for
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