Tri Band Transceiver
1. Introduction
Wireless Testbeds provide the experimental facility to test the validity of
algorithms and also to test any wireless setup. The Electrical and Computer engineering
department at Stevens Institute of Technology currently has a high speed radio testbed
which is capable of transmitting and receiving at 2.4 GHz. 2.4GHz ISM band is free to
all, so many applications now are using this band. These applications include digital
cordless phone, WLAN (802.11b), HomeRF, RFID, microwave oven and many other
proprietary technologies. The large amount of units using the same band has raised the
issues of possible interference. This has caused WLAN to migrate to 5.7 GHz ISM band.
This has raised the need for a testbed which is capable of transmitting and receiving at
5.7GHz in order to analyze the latest in wireless technology. The objective of this project
is to design, build and test a portable wireless Transceiver board capable of operating at
the following three ISM bands, 915MHz, 2.4GHz and 5.7GHz.
1
Tri Band Transceiver
2. Existing 2.4 GHz Transceiver Board
The current RF transceiver board used in the Wireless Research Lab of Stevens
Institute of Technology is capable of transmitting and receiving frequencies in the range
of 2.4GHz. The initial approach to our project was to understand the functionality of this
design so as to come up with a design capable of handling three different frequencies.
2.1 Transmitter End
The basic components of the transmitter end of the transceiver are the Modulator,
Bandpass Filter, Mixer, LO source and Amplifier. This design also uses low pass filters
at the IQ end to remove noise from the data acquisition card. The data from the DAQ
cards are modulated at 70 MHz with the use of a ZMIQ-70ML modulator. The 70 MHz
needed for the modulation is provided by a frequency synthesizer. The modulated signal
is passed through a band pass filter with centre frequency of 70 MHz. This removes noise
from the modulated signal. The filtered signal is then fed into a mixer, ZAM-42, which
accepts the signal at the IF end and a frequency of 2.33 GHz by the frequency source at
the Local Oscillator input and produces a carrier signal at 2.4 GHz. This signal is
amplified before being transmitted.
2
Tri Band Transceiver
2.2 Receiver End
The receiver end of the board reverses the operation of the transmitter end. The
received signal is first sent through a low pass filter to remove most of the noise. This
signal is then fed into an amplifier before being sent into a mixer which receives a
frequency of 2.33 GHz from the LO and subtracts this from the 2.4 GHz signal input to
have a signal of 70 MHz generated at the output. A band pass filter is used to filter this
signal out and send the signal to the demodulator. The demodulator takes a 70 MHz input
from the Local Oscillator to demodulate the signal to have the original data recovered.
3
Tri Band Transceiver
2.3 Noise Figure calculations for 2.4 GHz design
Gain
Component
NF(dB)
(dB)
NFn
GAINn
1
SLP 2950
2
ZKL 2R5
3
ZAM 42
-8.5
0.141254
4
SBP 70
-1.5
0.707946
5
ZKL 1R5
-1
5
3
30
40
0.794328
3.162278
1.995262
1000
10000
59
Nftot =
2.722148
NF
4.3491
Gain
59 dB
2.4 GHz Wireless Testbed Setup
4
Tri Band Transceiver
3. Alternate Designs
Based on the existing 2.4 GHz, several different designs were considered for the tri band
receiver.
3.1 Double Mixer Design
The modulation of the signal is performed the same as that of the existing 2.4 GHz
design. (Refer to section 2.1) The modulated signal is then passed to the mixer.
Depending on which frequency you which to transmit the modulated signal at, you pick
the mixer. For 900 MHz and 2.33 GHz, only one mixer is used. In the case of the 5.7
GHz section, the signal is first converted to 2.815 GHz using a mixer and this signal is
then filtered and passed to a second mixer where it is converted to 5.7GHz. The reason
for using two mixers is to avoid the need of an extra frequency source to provide
frequency above 5 GHz. This brings the overall cost of the design down by a lot. The
downfall of this design is the extra mixer needed which could reduce overall quality of
the transmitted signal. The extra mixer and filter also means more board space required.
5
Tri Band Transceiver
3.2 Single Stage Conversion Design
This is an expansion of the current 2.4 GHz design where two extra mixers are used
working at 915 MHz and 5.7GHz. The major draw back of this design is that we will
require LO supplies which are operational at the three different frequencies. This will be
6
Tri Band Transceiver
both expensive and difficult to obtain. One alternate was to use Voltage Controlled
Oscillators as our LO supply. Upon further research on VCOs we came to the conclusion
that VCOs will not provide the stability that our system requires. On the receiver end, the
same three mixers will be used to down convert the signal. The modulation and
demodulation stage are the same as mentioned before.
7
Tri Band Transceiver
3.3 900 MHz Modulation
8
Tri Band Transceiver
3.4 Tripler Design
9
Tri Band Transceiver
3.5 Three Stage Conversion Design
The modulation for this design is carried out at 70 MHz as in the case of the existing
design. This is then scaled up to 900 MHz using a mixer. If a 900 MHz signal is required
this signal is transmitted. If a 2.4 GHz or 5.7 GHz signal is required then the signal is
passed onto the respective mixer. And then amplifier is used to amplifier the signal
before transmission.
10
Tri Band Transceiver
4. Final Design
The final design chosen for the transceiver was based on the Tripler design. This design
was picked since it required the least number of components as well as the smallest range
of frequency source.
4.1 Transmitter End
The analog signals from the DAC are first passed through a low pass filter to remove
noise. These are then modulated at 70 MHz using a ZFMIQ-70ML modulator. This
accepts an input of 70 MHz at the LO end and provides a modulated signal of 70 MHz at
the RF end. The 70 MHz at the LO end will be provided by the secondary output of a
dual output LO Synthesizer from Praxsym Eng. A splitter is used to split the 70 MHz
signal for the transmitter and receiver end. The modulated signal is then filtered using a
70 MHz band pass filter. Depending on what frequency is needed, the 70 MHz modulated
signal is input into the respective filter.
900 MHz: The 70MHz filtered signal is passed into the IF input of the ZX0525MH mixer. A frequency of 845 MHz, provided by the primary out of the dual output
LO synthesizer is provided at the LO input of the mixer. The frequency from the LO
synthesizer is first split into two using a splitter, which one of the signals sent to The
output signal at the RF end will be comprised of various signals at different frequencies.
One of these is the summation of the two frequencies which is 915 MHz.
2.4 GHz: The 70MHz filtered signal is passed into the same mixer, ZX05-25MH
as before. A frequency of 2.33 GHz is supplied to the LO input by the NovaSource G2.
The mixer will add the two frequencies together to obtain a signal at 2.4 GHz.
5.7 GHz: The 70 MHz filtered signal is passed into the ZX05-C60 mixer. A
frequency of 1.88 GHz from the NovaSource is passed through a Tripler, ATA 1424.
This Tripler has a built in amplifier at the front and back end so the signal is amplified
twice to minimize power loss. The tripled signal at 5.63 GHz is then input in to the LO
end of the mixer where it is added together with the 70 MHz signal to produce a signal of
5.7 GHz at the RF end.
The signal from the RF end of the mixer is amplified using a ZKL-2R5 amplifier before it
is transmitted.
11
Tri Band Transceiver
12
Tri Band Transceiver
13
Tri Band Transceiver
4.2 Receiver End
An antennae is used to receive the signal and the signal is transmitted to the respective
filter depending on which frequency the transceiver needs to be operated at.
915 MHz: The received signal is passed through a low pass filter with a cut off
frequency of 1000 MHz. This will ensure no frequencies above 1000 MHz get passed
through to the rest of the receiver. The filtered signal is then passed to an amplifier before
being fed into the RF input of the mixer. A frequency of 845 MHz from the LO
synthesizer is fed into the LO input. The difference of these frequencies, 70 MHz is
obtained at the IF end.
2.4 GHz: The received signal is passed through a low pass filter with a cut off
frequency of 2.9 GHz. The filtered signal is then passed to an amplifier before being fed
into the RF input of the mixer. A frequency of 2.33 GHz from the NovaSource G6 is fed
into the LO input. The difference of these frequencies, 70 MHz is obtained at the IF end.
5.7 GHz: A low pass filter with a cut off frequency of 6.5 GHz is used after the
antennae. The filtered signal is then passed to an amplifier before being fed into the RF
input of the mixer. A frequency of 5.63 GHz, which is obtained after tripling the input
from the NovaSource G6 is fed into the LO input. The difference of these frequencies, 70
MHz is obtained at the IF end.
The signal obtained at the IF end of mixer is fed into a Band pass filter. This is to
filter out the 70 MHz signal and reduce as much noise into the demodulator as possible.
The filtered signal is amplifier and passed to the demodulator. A frequency of 70 MHz
from the dual output synthesizer is used by the demodulator to separate the signal into the
Q and I phase.
14
Tri Band Transceiver
15
Tri Band Transceiver
4.3 Calculation of System Specifications
Noise Figure Calculations
Transmitter End
1
2
3
4
Component
ZFMIQ-70M
SBP 70
ZX05-C60
ZKL 2R5
Nftot =
NF
Gain
NF(dB)
7.2
5
67.60884
18.3000
15.4
Gain
(dB)
-6.2
-1.5
-6.9
30
15.4
NFn
5.248075
1
1
3.162278
GAINn
0.239883
0.707946
0.204174
1000
Cummulative
NFn
7.20000
7.20000
5.24807
18.30004
NFn
GAINn
0.794328
1000
0.204174
0.707946
10000
0.239883
Cummulative
NFn
#NUM!
4.3491
2.7221
4.3491
4.3629
4.3629
dB
dB
Receiver End
1
2
3
4
5
6
Component
LPS50006
ZKL 2R5
ZX05-C60
SBP 70
ZKL 1R5
ZFMIQ-70D
Nftot =
NF
Gain
Gain
(dB)
NF(dB)
n/a
-1
30
-6.9
-1.5
40
-6.2
54.4
5
n/a
n/a
3
7.2
2.73082
4.3629
54.4
0
3.162278
1
1
1.995262
5.248075
dB
dB
The mixers used for all three frequencies had the same noise figures and gain. Also the
three different low pass filters used had the same noise figures and gain therefore, the
overall NF and Gain of the transceiver operating at either of the three frequencies were
16
Tri Band Transceiver
the same. Noise figures and gains weren’t available for all the components hence we
could not accurately calculate the values.
Calculations for 915 MHz and 2.4 GHz design
Since the 915MHz and 2.4 GHz design use the same components, the calculations for
both are identical.
Stage
Part
Gain (dB)
Gain
IP3 (dBm)
IP3 (Watts)
1
ZKL-2R5
30
1000
31
1.258
2
ZK05-25MH
-9.8
.1047
18
.06309
3
ZKL-1R5
40
10000
31
1.258
Formula used to convert Gain (dB) to the ratio of powers.
10*Log
P2
= Gain(dB)
P1
P2
P1
Formula used to convert IP3 (dBm) to IP3(Watts) :
10*Log
IP3(Watts)
=IP3(dBm)
.001Watts
IP3(Watts)
Calculation for Minimum Detectable Signal (MDS):
MDS=[-174+NF(system) +10Log(BW(system))] dBm
=[-174 + 4.3491 +10Log(24000000)]
=-95.84 dBm
Calculation of net IIP3 for the receiver system:
1
G1G 2
G1
=
+
IIP 3 IIP 3(2) IIP 3(3)
which gives IIP3 = 6.27604*(10^-5) Watts
IIP3 (dBm)= 10*log(6.27604*(10^-5))
17
Tri Band Transceiver
= -42.03 dBm
Calculation of the Dynamic Range:
DR = [2 (IPs - MDS)/3] dB
= [2(-42.03-(-95.84))/3]
= 35.14 dB
Calculations for the 5.7 GHz system:
Stage
Part
Gain (dB)
Gain
IP3 (dBm)
IP3 (Watts)
1
ZKL-2R5
30
1000
31
1.258
2
ZK05-C60
-8.5
.1412
11
.012589
3
ZKL-1R5
40
10000
31
1.258
Calculation of IIP3, using above formula:
= -49 dBm
18
Tri Band Transceiver
4.4 Component List
Part Description
Part Number
Price
1
Low Pass Filter
SLP 15
$
34.95
2
Modulator
ZF MIQ 70ML
$
3
Band Pass Filter
SBP 70
4
Mixer
5
Qty
Company
Tel
Total Price
4
Minicircuits
1 800 654 7949
$
139.80
89.95
1
Minicircuits
1 800 654 7949
$
89.95
$
18.95
2
Minicircuits
1 800 654 7949
$
37.90
ZX05-25MH
$
39.95
2
Minicircuits
1 800 654 7949
$
79.90
Mixer
ZX05-C60
$
39.95
2
Minicircuits
1 800 654 7949
$
79.90
6
Amplifier
ZKL-2R5
$ 149.95
3
Minicircuits
1 800 654 7949
$
449.85
7
Low Pass Filter
SLP 2950
$
34.95
1
Minicircuits
1 800 654 7949
$
34.95
8
Low Pass Filter
SLP-1200
$
34.95
1
Minicircuits
1 800 654 7949
$
34.95
9
Low Pass Filter
L0065001
$ 385.00
1
Microwave Circuits
1 800 642 2587
$
385.00
10
Amplifier
ZKL-1R5
$ 149.95
1
Minicircuits
1 800 654 7949
$
149.95
11
Demodulator
ZF MIQ 70D
$
89.95
1
Minicircuits
1 800 654 7949
$
89.95
12
NovaSource G6
NS3-1700102
$ 750.00
1
Nova Engineering
1 800 341 6682
$
750.00
13
Tripler
ATA-1424
$ 324.00
1
Marki Microwave
408 778 4200
$
324.00
14
Splitter
ZX10-2-25
$
34.95
1
Minicircuits
1 800 654 7949
$
34.95
15
Splitter
ZX10-2-12
$
24.95
2
Minicircuits
1 800 654 7949
$
49.90
16
Splitter
ZX10-2-98
$
39.95
1
Minicircuits
1 800 654 7949
$
39.95
17
SMA Male Connectors
PE-4112
$
4.30
75
Pasternack Entp
949 261 1920
$
322.50
18
SMA Male Right Angle
PE-4083
$
15.95
20
Pasternack Entp
949 261 1920
$
319.00
$ 885.00
1
Praxsyms
217 897 1744
$
885.00
$
1
Staffol Brothers
$
35.00
$
4,332.40
310-01005819
LO Synthesizer
001
Internal Chassis
20
Board
35.00
19
201 653 6479
Tri Band Transceiver
4.5 Final Layout
20
Tri Band Transceiver
5. System View Simulation
5.1 Background Information
System View provided various RF communication token which allow for the simulation
of transceiver designs. Initial simulations did not prove productive and affect consulting
with representatives at Elanix, we were given several metafiles for ideal mixer and
modulators components. By modifying these design we were able to fairly accurately
simulate of design.
5.2 I/O Setup
Figure 1: I/O Setup Diagram
The same basic I/O setup was used for all simulations. I and Q inputs were simulated
using a PN generator to generate a random PN sequence of frequency 10MHz and
amplitude 2V. The two inputs are filtered using a 15MHz lowpass filter before being
passed onto the QTxRx metafile. The metafile consists of the transmitter end and receiver
end components responsible for the modulation and demodulation of the I and Q data.
The demodulated data is received as the I & Q output and is filtered using 15MHz low
pass filters. The data is displayed for analysis.
21
Tri Band Transceiver
5.3 Design Simulation
Figure 2: QTxRx900.mta
The I and Q input signals are first fed into the TxQMod metafile. This a modified version
of the metafile received from Elanix which simulates an IQ modulator. (refer to
modulation section for more details on the TxQMod metafile. The modulated data is sent
to the TxUpConvMainLib metafile. This metafile simulates a mixer. (Fig.3) The
modulated signal is multiplied with a sin wave of desired frequency to produce a signal
of that frequency. A band pass filter is used to remove noise from the signal. Two filters
were used in this simulation as one wasn’t enough to remove all the noise. (Refer to the
Extra filter section for more information)
22
Tri Band Transceiver
Figure 3: Mixer Simulation Setup
The receiver side of the simulation consists of a mixer (Fig.4) which down converts the
transmitted signal to 70 MHz. The filter design is identical to that used to in the
transmitter end except for the filters used. The band pass filters used which allow only
signals in the 70 MHz range to pass through.
23
Tri Band Transceiver
Figure 4: Mixer Simulation Setup
The 70 MHz signal is passed to the demodulator metafile which will separate the signal
into the I an Q components. (Refer to demodulation section for more information.)
24
Tri Band Transceiver
5.4 Simulation Results
900 MHz Design
(a)
(d)
(b)
(e)
(c)
(f)
2.4 GHz Design
(d)
(a)
(e)
(b)
(c)
(f)
5.7 GHz Design
25
Tri Band Transceiver
(a)
(d)
(b)
(e)
(c)
(f)
5.5 Multiple Filters
A common problem we discovered with the transmitted signal was that some of the
signal from the LO had leaked into the transmitted signal. This was identified using by
plotting the power spectrum graph of the transmitted signal. In the case of the 915MHz
design leakage was noticed at 845 MHz and for the 2.4 GHz design, the leakage was at
2.33 GHz. Both these frequencies are equal to the respective LO frequencies of the
designs. The solution to this was found my using multiple band pass filters after the up
conversion stage. (Figure 5)
26
Tri Band Transceiver
Two band
pass filters
being used.
Figure 5
Simulation Results
900 MHz Tx Signal using one filter
900 MHz Tx Signal using two filters
27
Tri Band Transceiver
2.4 GHx Tx Signal using one filter
2.4 GHx Tx Signal using two filters
2.4 GHx Tx Signal using three filters
28
Tri Band Transceiver
5.6 Simulation using real components
System View provides in its library several RF components. Two of these, passive mixer
and amplifier are used in our design and we tried to run simulations using these
components. These components are meant to simulate real components taking into
account noise figures, conversion loss and other such details not addressed by the ideal
components used in the initial simulations. However, working with these components
proved to be difficult and results obtained weren’t satisfactory. After several
communication with Elanix representatives and other system view users, there was a
general consensus that the passive mixer token has numerous flaws and is not ideal for
high frequency simulations. Presented below are the results obtained for the 915 MHz
design using real components.
915 MHz Simulation Results – Real Components
Power Spectrum of Tx Signal
29
Tri Band Transceiver
As seen in the results, the Signal is being transmitted at the required frequency, but the
input and output signal of the I and Q channels do not match up. We plotted the signal at
each stage of the transceiver and it was noted that the signal was being badly distorted
after the mixer stage.
After consulting with Elanix, we decided to use the ideal mixer and add an attenuator to
simulate the power loss of the mixer. The resulting simulations were much more accurate
and the input and output data matched up. The setup for these simulations are as follows:
30
Tri Band Transceiver
I/O Setup
Tx and Rx End
31
Tri Band Transceiver
Mixer Setup
Simulation Results
900 MHz simulation
32
Tri Band Transceiver
6. Testing
Initial testing of the design was done using the Agilent signal generators and spectrum
analyzers present in the wireless research lab. One of the generator was used to generate a
5MHz sine wave which was used as an input into the I channel of the modulator. The
spectrum analyzer was used to monitor the signal at various stages in the transmission
and reception process. The resulting signal at the I channel of the demodulator in the
receiver end was observed using a Cathode Ray Oscilloscope.
915 MHz Test Results
Input Signal
Signal Modulated at 70 MHz
Transmitted Signal at 900 MHz
Down-converted Signal at Receiver Side
33
Tri Band Transceiver
Filtered 70 MHz signal before Demodulation
Output Signal at I channel
2.4 GHz Test Results
Input Signal
Signal Modulated at 70 MHz
Up-converted Signal to 2.4 GHz
Transmitted Signal
34
Tri Band Transceiver
Down-converted Signal to 70MHz by Rx
Filtered and Amplified signal before Demod
Output Signal
Power Reading Summary from 2.4 GHz Testing
Tx End
Input Signal:
Power = -20 dBm
Frequency = 5 MHz
After Modulation:
Power = -29.8 dBm
After Filter:
Power = -30.2 dBm
Up converted Signal:
Power = -53.4 dBm
Amplified Signal:
Power = -21.0 dBm
Transmitted Signal:
Power = -35.7 dBm
35
Tri Band Transceiver
Rx End
Amplified Signal:
Power = -14.5 dBm
Down-converted Signal:
Power = -33.6 dBm
Amplified Signal:
Power = +4 dBm
Working Range of Design
To determine the working range of our design, we used the Agilent Signal generator to
generate a signal of frequency 916MHz. This was used as the transmitted signal. The
receiver down converts the signal and demodulates it to form a 1 MHz sine wave which
was displayed using the CRO. The power of the transmitted signal was varied and the
woking range was determined as the power range of transmitted signal for which the
signal on the CRO would be displayed. The results of the testing was as follows:
915 MHz Receiver:
-32 dBm to -80 dBm
2.4 GHz Receiver:
-50 dBm to -90 dBm
5.7 GHz Receiver:
36
Tri Band Transceiver
7. Improved Alternate Design
Based on our test results and simulation results, we designed an improved transceiver
system, still operating at the three desired frequencies. The major changes in this design
were the use of a doubler for the 2.4 GHz portion of the design and using a LO to provide
the 5.63 GHz required by the 5.7 GHz mixers. Also, all the lowpass filters in the front
end of the receiver were replaced with band pass filters. This is mainly aimed to reduce
the LO leakage observed during testing. Since the double we are using is passive, our
design also includes an amplifer after the doubler to counter the loss. On the receiver end
we have added an extra amplifier to better improve the dynamic range of the system.
37
Tri Band Transceiver
Component List
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
22
Part Description
Low Pass Filter
Modulator
Band Pass Filter
Mixer
Mixer
Amplifier
Amplifier
Demodulator
Splitter
Splitter
Splitter
900MHz
Bandpass Filter
2.4GHz
Bandpass Filter
5.7GHz
Bandpass Filter
NovaSource M2
NovaSource G6
NovaSource G6
Doubler
Internal Chassis
Board
Tel
1 800 654 7949
1 800 654 7949
1 800 654 7949
1 800 654 7949
1 800 654 7949
1 800 654 7949
1 800 654 7949
1 800 654 7949
1 800 654 7949
1 800 654 7949
1 800 654 7949
Delivery
Time
2 Weeks
2 Weeks
2 Weeks
2 Weeks
2 Weeks
2 Weeks
2 Weeks
2 Weeks
2 Weeks
2 Weeks
2 Weeks
$
$
$
$
$
$
$
$
$
$
$
Total Price
139.80
89.95
37.90
79.90
79.90
749.75
299.90
89.95
34.95
49.90
39.95
1 800 642 2587
3 Weeks
$
350.00
1 800 642 2587
3 Weeks
$
350.00
1
1
1
1
1
Company
Minicircuits
Minicircuits
Minicircuits
Minicircuits
Minicircuits
Minicircuits
Minicircuits
Minicircuits
Minicircuits
Minicircuits
Minicircuits
Microwave
Circuits
Microwave
Circuits
Microwave
Circuits
Nova Enginnering
Nova Enginnering
Nova Enginnering
Pasternack Entp
1 800 642 2587
1 800 341 6682
1 800 341 6682
1 800 341 6682
949 261 7451
3 Weeks
4 Weeks
4 Weeks
4 Weeks
2 Weeks
$
$
$
$
$
350.00
750.00
750.00
750.00
369.95
1
Staffol Brothers
201 653 6479
2 Days
$
35.00
Part Number
SLP 15
ZF MIQ 70ML
SBP 70
ZX05-25MH
ZX05-C60
ZKL-2R5
ZKL-1R5
ZF MIQ 70D
ZX10-2-25
ZX10-2-12
ZX10-2-98
Price
$ 34.95
$ 89.95
$ 18.95
$ 39.95
$ 39.95
$ 149.95
$ 149.95
$ 89.95
$ 34.95
$ 24.95
$ 39.95
Qty
4
1
2
2
2
5
2
1
1
2
1
B0809253
$ 350.00
1
B1523751
$ 350.00
1
B1855001
NS2-0065503
NS3-0800102
NS3-5470102
PE8600
$
$
$
$
$
350.00
750.00
750.00
750.00
369.95
$
35.00
$ 5,396.80
38
Tri Band Transceiver
References
[1]
The Basics of RF System Design, Mark Hunter, Paper presented at the IEE
Training Event - How to Design RF Circuits", 5th April2000.
[2]
Noise Figure Measurement, Thomas H. Lee, rev. February 7, 2003;
[3]
Introduction to Communication System, Stremler, 3rd Edition, Addison Wesley,
1992
[4]
http://www.minicircuits.com/appnote/mixer1-4.pdf
39