RF System Architecture and Budget Analysis · PDF fileRF System Architecture and Budget...
Transcript of RF System Architecture and Budget Analysis · PDF fileRF System Architecture and Budget...
RF System Architecture and
Budget Analysis
Anurag Bhargava
Application Consultant
Agilent EEsof EDA
Agilent Technologies
Email: [email protected]
You Tube: www.youtube.com/user/BhargavaAnurag
Blog: http://abhargava.wordpress.com
Spectral Domain Techniques
Page 2
RF Architecture Design
During RF architecture design engineers determine how many,
what type, parameters, and the order of stages required to meet
system specifications
Coupler
IL=2 dB
CPL=20 dB
DIR=30 dB
Z0=50 ohm
1
3
2
? or
Spectral Domain Techniques
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The Architecture is Critical
• Architecture is the system foundation
• Poor architecture causes poor performance
• Poor architecture causes more design turns
• Poor architecture causes increased cost
• Poor architecture causes increased time to market
Spectral Domain Techniques
Page 4
Traditional Method Limitations
• SPICE, linear, and harmonic balance simulators are designed
for components, not for complex system realization
• Programming spreadsheets is extremely difficult when image
noise, intermod filtering, mismatch effects and multiple paths
are considered
• Summary: traditional tools are ill-suited for analyzing RF
architectures
Spectral Domain Techniques
Page 5
What is Required for RF Architecture Analysis?
Spur identification and resolution
• Identifying root causes is critical in systems with hundreds of leakage,
harmonic and intermod tones.
Noise analysis that considers the channel bandwidth
In-channel and out-of-channel intermodulation analysis
Accuracy: mismatch, phase, images, measured vs. ideal
models, etc.
Typical RF System
Copyright © 2012 Agilent Technologies
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Antenna
TX Filter
Switch or Duplexer
RX Filter
LNA
TX Power Amplifer
Synthesizer or PLL Buffer Amp
Buffer Amp
Attenuator Mixer
Mixer
IF Filter IF Amp
Demodulator
IF Filter Modulator
Typical RF System
Copyright © 2012 Agilent Technologies
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How do you determine what types of
stages to use, the order to place
them, and the parameters for each
block?
How would you respond to the following questions?
1. How do you currently determine what and where spurious and intermod products are being generated in the RF portions of you design?
2. How do you identify possible leakage paths in your design?
3. Does your current method of designing wideband systems include the effects of frequency dependencies of complex load impedance?
4. How do you access the impact of phase noise on noise figure?
5. How do you do budget analysis in the presence of modulated signals?
6. How do you compute noise figure of a path while other paths are actively connected to this path?
Copyright © 2012 Agilent Technologies
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Why was Spectrasys Developed?
Copyright © 2012 Agilent Technologies
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• RF Architecture (or Systems design) are the titles used during
the design stage where engineers determine what types of
stages (filters, amplifiers, mixers, etc), the ordering of these
stages in the design, and their parameters.
• Cascaded equations are used during this phase.
G1
nf1
OP1dB1
OIP31
G2
nf2
OP1dB2
OIP32
G3
nf3
OP1dB3
OIP33
𝐺 = 𝐺1 × 𝐺2 × 𝐺3
1
𝑂𝐼𝑃3𝑡𝑜𝑡𝑎𝑙=
1
𝑂𝐼𝑃31 × 𝐺2 × 𝐺3+
1
𝑂𝐼𝑃32 × 𝐺3+
1
𝑂𝐼𝑃33
1
𝑂𝑃1𝑑𝐵𝑡𝑜𝑡𝑎𝑙=
1
𝑂𝑃1𝑑𝐵1 × 𝐺2 × 𝐺3+
1
𝑂𝑃1𝑑𝐵2 × 𝐺3+
1
𝑂𝑃1𝑑𝐵3
𝑛𝑓𝑡𝑜𝑡𝑎𝑙 = 𝑛𝑓1 +𝑛𝑓2 − 1
𝐺1+
𝑛𝑓3 − 1
𝐺1 × 𝐺2
Why was Spectrasys Developed?: Continued
Copyright © 2012 Agilent Technologies
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How do you use
cascaded equations on
this?
Why was Spectrasys Developed?: Continued
Copyright © 2012 Agilent Technologies
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It would be nice if every
design was two port AND just
contained behavioral models.
But its not!
Spectral Domain Techniques
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SPARCA
These needs led to the development of the SPARCA method,
an acronym for Signal Propagation And Root Cause Analysis.
• New method developed in 2002
• Based in the frequency domain
• Bilateral signal flow of all paths
• Magnitude and phase modeling (vector)
• Channel concepts integrated into the method
Spectral Domain Techniques
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How SPARCA Works
Signal generation and propagation:
• All signal sources and noise sources propagate through all paths to all nodes
• Harmonic and intermod products are generated by non-linear models and
propagate to all nodes
Measurements:
• Power and noise are each is integrated across the channel bandwidth
• In-channel and adjacent channel measurements are calculated from the spectrums
at each node
Imperfections modeled:
• Devices are bilateral
• The true filtered and non-flat transfer function including phase is modeled
• Mismatch, reflections, and reverse propagation are accurately modeled
Spectral Domain Techniques
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SPARCA Method
SPARCA does not replace other analysis methods (except
perhaps spreadsheets), it complements them. It is optimized for
RF architecture design.
Advantages • Identifies root causes
• Handles multiple paths
• More accurate than ideal model and scalar
methods
• Handles more signals & tones than other methods
• Handles channel concepts
• Integrates well with other software and lab tools
Spectral Domain Techniques
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Example: Aviation Band Downconverter
The analyzer uses a tunable 1st LO to convert 500 KHz segments
of the aviation band to 0.95 to 1.45 MHz for baseband processing.
(1)
RF BPF
FLO=105 MHz
FHI=139 MHz
N=4
R=0.1 dB
RFAMP
G=?9 dB
NF=2 dB
OP1DB=15 dBm
R IL
RF Mixer
CL=8 dB
LO=7 dBm
LO ATTN
L=6 dB
(2)
IFAMP1
G=9 dB
NF=3 dB
OP1DB=25 dBm
IF BPF
FLO=21.45 MHz
FHI=22.45 MHz
IL=2 dB
IFAMP2
G=20 dB
NF=3 dB
OP1DB=30 dBm
R IL
Detector
CL=8 dB
LO=23 dBm
(3)
BASEBAND AMP
G=46 dB
NF=6 dB
OP1DB=36 dBm
(4)
RF: 108 to 136 MHz
LO: 86.3 to 114.3 MHz
BFO: 20.75 MHz
BASEBAND:
0.95 to 1.45 MHz
1 5 6
13
2
16 9 10 17
3
7 4
Spectral Domain Techniques
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Simple Cascade Noise Figure
In this equation block, noise figure cascade
formula have been entered much like could
be programmed into a spreadsheet. This is
being done to illustrate the errors introduced
by spreadsheet system analysis.
Spectral Domain Techniques
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Results of the Cascade Calculation
(1)
RF BPF
FLO=105 MHz
FHI=139 MHz
N=4
R=0.1 dB
RFAMP
G=?9 dB
NF=2 dB
OP1DB=15 dBm
R IL
RF Mixer
CL=8 dB
LO=7 dBm
LO ATTN
L=6 dB
(2)
IFAMP1
G=9 dB
NF=3 dB
OP1DB=25 dBm
IF BPF
FLO=21.45 MHz
FHI=22.45 MHz
IL=2 dB
IFAMP2
G=20 dB
NF=3 dB
OP1DB=30 dBm
R IL
Detector
CL=8 dB
LO=23 dBm
(3)
BASEBAND AMP
G=46 dB
NF=6 dB
OP1DB=36 dBm
(4)
RF: 108 to 136 MHz
LO: 86.3 to 114.3 MHz
BFO: 20.75 MHz
BASEBAND:
0.95 to 1.45 MHz
1 5 6
13
2
16 9 10 17
3
7 4
Here the block diagram of the downconverter
is repeated along with the resulting cascade
noise figure after each stage in the
downconverter. The resulting noise figure at
the baseband output is 5.28 dB.
Spectral Domain Techniques
Page 18
Results by Spectral Propagation
Shown at the left is a level diagram in SPECTRASYS. This
level diagram depicts the cascade noise figure in red, the
stage noise figure in blue and the percentage noise figure in
green. Numeric cascade noise figure data after each stage is
also given in the final column in the table at the lower right.
Notice that the noise figure after the final amplifier computed
using SPARCA is 7.83 dB, rather than the 5.28 dB computed
using classical cascade NF equations. The popular and
classical formula is in error by 2.55 dB!
Spectral Domain Techniques
Page 19
Source of Noise Figure Error
What is the source of this error?
• Mixer noise figure assumes noise only exists in the desired signal channel. In reality, noise exists in both the desired and image channel. Therefore, the true noise figure of a mixer is 3.01 dB higher than the specified noise figure.
Why not just specify the mixer noise figure 3 dB higher than is normally done?
• Because in a system with gain and an image filter preceding the mixer, the effective noise figure of the mixer approaches the specified value. In that case, using the higher noise figure would give the wrong result.
The fact of the matter is, accurate assessment of system noise figure requires noise propagation analysis. If the position of the input filter and the preamp are changed and the loss of the input filter was set to zero. Simple cascade analysis would predict the same noise figure for both systems. In reality, the difference with a 30 dB preamp with 8 dB noise figure is 2.7 dB. Approaching 3 dB. But look what happens when the noise figure of the preamp is reduced to 2 dB. The difference is then 1.4 dB. Again, accurate noise analysis requires noise propagation techniques.
In a similar way, spreadsheet analysis of intermodulation and dynamic range are also flawed.
Spectral Domain Techniques
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Measurements
Different applications require different forms of output data. In
the next few slides, brief definitions and examples of
SPECTRASYS output data are provided.
There are over 85 built-in measurements.
Spectral Domain Techniques
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Measurements: Gain & Signals in the Channel
Cascaded Gain
Cascaded Gain (All Signals)
Channel Frequency
Channel Power
Channel Power (Desired)
Gain
Gain (All Signals)
Total Node Power
Spectral Domain Techniques
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Example: Gain & Signal Level Diagram C
F (M
Hz), D
BM
[CP
], DB
M[D
CP
]
-50
-20
10
40
70
100
130
DB
[GA
IN],
DB
[CG
AIN
]
-10
0
10
20
30
40
50
Node
1 5 6 16 9 10 17 7 8 4
Gain & Signal
R IL
R IL
DB[GAIN]
DB[CGAIN]
CF (MHz)
DBM[CP]
DBM[DCP]
Spectral Domain Techniques
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Measurements: Noise
Added Noise
Carrier to Noise Ratio
Cascaded NF
Channel Noise Power
Image Channel Noise Power
Image Noise Rejection Ratio
Minimum Detectable Signal
Percent Noise Figure
Stage NF
Spectral Domain Techniques
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Example: Noise
Short Video
Removed due to size of
the Video……
Spectral Domain Techniques
Page 26
Intermodulation
Cascaded intermod equations are NOT used by SPECTRASYS. Just as with
noise, cascade intermod equations are flawed because they:
• Assume interfering signals are not filtered and maintain the same gain as the
desired signal through all cascaded stages
• Assume all stages are perfectly matched
• Assume two equal tones
• Assume infinite reverse isolation
Signal propagation generates intermod signals as they appear in real
systems. Signals are not limited to two tones. All intermods are propagated
through the system using the system transfer function. Consequently,
intermod measurements are accurate for filtered and non-ideal systems.
Spectral Domain Techniques
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Measurements: Intermodulation & Compression
Cascaded Gain (3rd IM)
Channel Frequency (Tone)
Channel Power (Desired 3rd IM)
Channel Power (Tone)
Gain (3rd IM)
Gain (All Signals)
Percent 3rd IM
Stage Output 1 dB Compression
Stage Output 2nd IM
Stage Output 3rd IM
Stage Output Saturation Power
3rd Order Intercept (Input)
3rd Order Intercept (Output)
3rd IM Power (Propagated)
3rd IM Power (Generated)
3rd IM Power (Total)
Spectral Domain Techniques
Page 28
Example: Intermodulation & Compression D
BM
[GIM
3P
], DB
[SD
R]
-200
-160
-120
-80
-40
0
40
80
120
160
200
DB
M[II
P3
], P
RIM
3
-30
-24
-18
-12
-6
0
6
12
18
24
30
Node
1 5 6 16 9 10 17 7 8 4
Intermodulation & Compression
R IL
R IL
DBM[IIP3]
DBM[GIM3P]
DB[SDR]
PRIM3
Spectral Domain Techniques
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Measurements: Dynamic Range
Spurious Free Dynamic Range
Stage Dynamic Range
Spectral Domain Techniques
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Example: Dynamic Range D
BM
[MD
S]
-150
-144
-138
-132
-126
-120
DB
[SF
DR
], D
BM
[IIP
3]
-30
0
30
60
90
120
Node
1 5 6 16 9 10 17 7 8 4
Dynamic Range
R IL
R IL
DB[SFDR]
DBM[IIP3]
DBM[MDS]
Spectral Domain Techniques
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Measurements: Out of Channel
Adjacent Channel Power
Adjacent Channel Frequency
Channel Frequency (Offset)
Channel Power (Offset)
Image Frequency
Image Channel Noise Power
Image Noise Rejection Ratio
Mixer Image Channel Power
Mixer Image Rejection Ratio
Spectral Domain Techniques
Page 32
Phase & Complex Models
The SPECTRASYS SPARCA simulator propagates signals using complex
multi-port transfer functions for the system.
• Phase data is retained and utilized
• Circuit models and schematics may be mixed with system models in the schematic
• The effects of mismatch are simulated
• Bilateral signal flow is simulated
(1)
COUPLER1_1
IL=1 dB
CPL=10 dB
[DIR=30 dB]
ATTN_VAR_1
IL=1 dB
L=?0.25 dB
RF_DELAY_1
T=0.27 ns
[Z0=50 Ω]
RF_PHASE_1
A=?10°
[Z0=50 Ω]
RFAMP_1
G=17 dB
NF=8 dB
OPSAT=50 dBm
COUPLER1_2
IL=0.5 dB
CPL=24 dB
[DIR=30 dB]
SPLIT2_1
[IL=3.1 dB]
ISO=100 dB
PH3=0°
RF_DELAY_2
T=0.53 ns
[Z0=50 Ω]
RF_PHASE_2
A=?10°
[Z0=50 Ω]
ATTN_VAR_2
IL=1 dB
L=?0.5 dB
RFAMP_2
G=38 dB
NF=8 dB
OPSAT=43 dBm
COUPLER1_3
IL=0.5 dB
CPL=10 dB
DIR=30 dB
(2)1
15
4
15
5
14
11 6
7
7
14
8 8
9
10
13 12
10
3
3
2
Spectral Domain Techniques
Page 33
X-Parameter Models are Supported
Spectral Domain Techniques
Page 34
The Link to ADS
Schematics can be exported to ADS for further simulation.
Digital / DSP & RF System Cosimulation
Modulation and Spectrasys (SystemVue)
Copyright © 2012 Agilent Technologies
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The RF Link part is used in a
data flow schematic to point
to a Spectrasys schematic.
How RF Impairments affect Modulation Quality
Copyright © 2012 Agilent Technologies
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Tunable Impairment List:
Gain Imbalance
Phase Imbalance
LO to RF Isolation
Noise Figure
Phase Noise
ADC (# of bits, clock, ref voltage)
Gain Imbalance effects on Constellation
Copyright © 2012 Agilent Technologies
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Blue – Balanced Gain (Square)
Red – Imbalanced Gain
Phase Imbalance effects on Constellation
Copyright © 2012 Agilent Technologies
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Blue – Balanced Phase (Square)
Red – Imbalanced Phase
LO to RF Isolation (DC Offset) effects on
Constellation
Copyright © 2012 Agilent Technologies
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Blue – High Isolation (Square)
Red – Lower Isolation
The LO leaks into the RF and
appears as another RF input
signal
LO to RF Isolation (DC Offset) effects on
Constellation
Copyright © 2012 Agilent Technologies
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Blue – High Isolation (Square)
Red – Lower Isolation
The RF can also leak into the
LO and this is used as another
LO signal
Noise effects on Constellation
Copyright © 2012 Agilent Technologies
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Blue – No Noise (Square)
Red – Thermal and Phase Noise
Modulation Analysis Software (works with
Hardware)
Copyright © 2012 Agilent Technologies
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Spectral Domain Techniques
Page 44
Summary
A new system simulation technique referred to as Spectral
Propagation and Root Cause Analysis (SPARCA) offers a new
set of tools for the optimization of system architectures
• Improved accuracy over conventional cascade analysis
• Rapid root cause discovery using spectral component display at any node
• Wide set of built-in as well as user specified measurements
• Complex, bilateral and mismatch analysis
• Integration of other spectral domain simulation and synthesis tools
SPARCA is optimized for system architecture development and
saves multiple architecture and component design turns.
Looking Ahead..!!
Kindly send your requests on what we can cover in our future webinars to:
India:
Mukul Pareek
Marketing Engineer
Agilent Technologies India Pvt. Ltd
Email: [email protected]
Elsewhere:
Please contact your local Agilent representative.
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Q & A