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Table of Contents

Application Note

LMX2820 RF Synthesizer Phase Noise Improvement With
Alternative Topologies

Russell Hoppenstein

Systems Engineering and Marketing
ABSTRACTThe LMX2820 is a low phase noise RF synthesizer. The device offers additional features for cases where
improved phase noise performance is needed. This note characterizes the inherent phase noise performanceof the LMX2820 with varying PFD frequencies and reference sources. This analysis is used as a baseline tocompare against the improvement topologies. The first option uses an external VCO instead of the internal one.
This facilitates a higher-Q, lower phase noise VCO at the expense of tuning range. The second option uses anexternal mixer to bypass the internal N-divider. This eliminates the PLL phase noise degradation that the internal
divider introduces. Combining both techniques with a superior reference yields the ultimate realizable phasenoise performance.

Table of Contents
1 Introduction.............................................................................................................................................................................3
2 Reference Frequency............................................................................................................................................................. 3
3 Standard LMX2820 Phase Noise Performance.................................................................................................................... 5
4 Pre-multiplier Stage Performance ........................................................................................................................................7
4.1 External VCO Loop Filter Design....................................................................................................................................... 8
4.2 Active Loop Filter Implementation....................................................................................................................................10
4.3 External VCO Performance Results................................................................................................................................. 11
5 External PFD Topology.........................................................................................................................................................12
5.1 External PFD Loop Filter Modification..............................................................................................................................12
5.2 External PFD Measurement Results................................................................................................................................14
6 Putting it Together in the Real World..................................................................................................................................15
6.1 Real-World Performance Results.....................................................................................................................................15
6.2 Why use the Dual Approach?.......................................................................................................................................... 16
7 Conclusion............................................................................................................................................................................ 17
8 Revision History................................................................................................................................................................... 18

List of Figures
Figure 2-1. Phase Noise Comparison of Reference Sources......................................................................................................3
Figure 3-1. LMX2820 Phase Noise Performance Over PFD Frequency at 6-GHz Output..........................................................5
Figure 3-2. LMX2820 Phase Noise Performance Over PFD Frequency at 9-GHz Output..........................................................6
Figure 4-1. 3x Pre-multiplier Stage .......................................................................................................................................... 7
Figure 4-2. Phase Noise Comparison of 1474.56 MHz Signal ............................................................................................... 7
Figure 4-3. External VCO PLLatinum™ Simulation GUI Loop Filter............................................................................................ 9
Figure 4-4. Block Diagram of the External VCO Configuration..................................................................................................10
Figure 4-5. External VCO Phase Noise Compared to LMX2820 Internal VCO......................................................................... 11
Figure 5-1. Block Diagram of the External Mixer, PFD Topology...............................................................................................12
Figure 5-2. PLLatinum™ Simulation for External PFD............................................................................................................... 13
Figure 5-3. LMX2820 External PFD Phase Noise Performance................................................................................................14
Figure 6-1. Dual LMX2820 Approach for a Real-World Solution............................................................................................... 15
Figure 6-2. Dual LMX2820 Real-World Phase Noise Results................................................................................................... 15
Figure 6-3. External PFD Over PFD Divider..............................................................................................................................16
Figure 6-4. Phase Noise Over Output Divider Settings............................................................................................................. 17

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List of Tables
Table 2-1. RMS Jitter Comparison of Reference Sources (1 kHz–40 MHz)................................................................................ 4
Table 3-1. LMX2820 Integrated RMS Jitter (10 kHz–40 MHz) Over PFD Frequency..................................................................6
Table 4-1. Open Loop Phase Noise Parameters for the Z-Comm DRO9000A............................................................................8
Table 4-2. Active Loop Filter Component Values......................................................................................................................... 9
Table 4-3. Key OPA211 Op-Amp Specifications........................................................................................................................ 10
Table 4-4. External VCO RMS Jitter Performance Comparison.................................................................................................11
Table 5-1. External PFD Loop Filter Values............................................................................................................................... 13
Table 6-1. Integrated RMS Jitter Performance Comparison With External PFD....................................................................... 16
Table 6-2. External PFD Over PFD Divider............................................................................................................................... 17
Table 6-3. Integrated Phase Noise Over Output Divider Settings..............................................................................................17

Trademarks
PLLatinum™ is a trademark of Texas Instruments.
R&S® is a registered trademark of Rohde & Schwarz GmbH & Co.
All trademarks are the property of their respective owners.

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Introduction

1 Introduction
The LMX2820 RF synthesizer inherently provides excellent phase noise performance and operates up to 22
GHz; however, there are cases that need improved phase noise performance. The LMX2820 offers a couple ofdifferent topologies to improve synthesizer phase noise. One technique bypasses the internal voltage-controlled
oscillator (VCO) and uses an external one. This introduces a superior low phase noise VCO while maintaining
the programming features of the PLL device. The second technique uses an external mixer to down-convert the
RF frequency to the PFD (Phase Frequency Detector) frequency. This bypasses the internal feedback dividers
which are one of the sources for degraded PLL phase noise.

2 Reference Frequency
The foundation of any RF synthesizer is the reference frequency. Achieving the best synthesizer phase noise
starts with a high-quality reference source. Not all sources or generators are equivalent. Some show good low
offset performance while sacrificing high offset noise floor. Depending on the application, one source can prove
more beneficial than another based on the phase noise profile. The following signal generator sources arecompared to find the best reference source for the subsequent measurement analysis.
•
•
•
•
•

Rohde & Schwarz (R&S®) SMA100B
Wenzel oscillator
Agilent PSG (with UNR enhanced phase noise option)
R&S SMA100A
Agilent ESG

Figure 2-1 shows the phase noise comparison between the sources operating at 307.2 MHz. Table 2-1 outlines
the RMS jitter integrated from 1 kHz to 40 MHz. The source output power is over 10 dBm and the phase noise
measurement were conducted with the Holzworth phase noise analyzer.

Figure 2-1. Phase Noise Comparison of Reference Sources

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Table 2-1. RMS Jitter Comparison of Reference Sources (1 kHz–40 MHz)
Instrument

JitterR&S SMA100B

19.5 fs

Wenzel Oscillator

10.4 fs

Agilent PSG

113.4 fs

R&S SMA100A

70.8 fs

Agilent ESG

150.0 fs

The Wenzel oscillator is the premier standard. The oscillator provides excellent close-in and far-out phase noise
performance and is ideal for the reference, but it is limited to just one frequency. The Rohde and Schwarz
SMA100B rivals the Wenzel. The close-in phase noise is almost as good (or in some offset cases slightly better)
than the Wenzel. Only at very high frequency offsets past 3 MHz does the SMA100B significantly deviate fromthe Wenzel.
The Agilent PSG has good very low frequency offset performance that is close to the Wenzel out to about 300
Hz. After that, there is a significant deviation from the standard. The Rohde SMA100A and the Agilent ESG havenoticeable degradation at low-frequency offsets.
Overall, the SMA100B is a good substitute for the Wenzel oscillator for use as a reference to provide flexibility inselecting the reference frequency for the synthesizer.

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Standard LMX2820 Phase Noise Performance

3 Standard LMX2820 Phase Noise Performance
To understand the performance improvement with alternative topologies, first characterize the inherent
LMX2820 performance using the internal VCO. The TIDA-010230 reference design incorporates two LMX2820
synthesizers and includes options for operating in standard or alternative topologies. It is an ideal platform forcomparing relative phase noise performance across different settings. Using the TIDA-010230 reference design,
the LMX2820 is characterized with different PFD frequencies. Note, the LMX2820 PFD frequency is limited
to 400 MHz maximum. It is expected that higher PFD frequencies that translate to lower N-divider values will
provide better results.
The phase noise response and integrated jitter is dependent on the reference source. The reference source forthe phase noise measurements is the SMA100B which is extremely good; however, it is conceivable that aneven better reference source provides slightly improved results. The RMS jitter calculations start at 10 kHz todecouple a bit from the very low frequency offsets that are dominated by the reference performance.
Figure 3-1 shows the phase noise performance of the LMX2820 with various PFD frequencies at 6-GHz output.
RMS jitter is integrated from 10 kHz to 40 MHz. Similarly, Figure 3-2 shows the phase noise performance at
9 GHz measured after an RF amplifier to amplify the signal to around 10 dBm. The Agilent E5052 measured
performance at frequencies below 7 GHz; the Rohde and Schwarz FSWP measured performance at the higher
frequencies.

Figure 3-1. LMX2820 Phase Noise Performance Over PFD Frequency at 6-GHz Output

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Figure 3-2. LMX2820 Phase Noise Performance Over PFD Frequency at 9-GHz Output
Table 3-1 shows the integrated RMS jitter for 6-GHz output and 9-GHz output. In all cases, the loop filter remains
constant; there is some improvement possible with a lower PFD frequency if the loop filter is optimized for therequired N-divider setting.
Table 3-1. LMX2820 Integrated RMS Jitter (10 kHz–40 MHz) Over PFD Frequency
6 GHz

9 GHz

PFD

N-Divider

Integrated Phase Noise

N-Divider

Integrated Phase Noise

100 MHz60

62.4 fs

90

61.5 fs

200 MHz30

43.9 fs

36

46.0 fs

300 MHz20

38.1 fs30

40.5 fs

375 MHz16

36.4 fs

24

37.9 fs

As expected, a higher PFD frequency corresponding to a lower N-divider value yields the best results. The
optimum value is at 375 MHz which is convenient for locking to a 6-GHz or a 9-GHz VCO.
The area of the curve that shows the difference is the middle section from around 1k-Hz offset to 1-MHz
offset. This area is heavily influenced by the PLL performance and correspondingly the N-divider setting. The
reference source dominates the performance at very low-frequency offsets. The VCO performance dominates at
high-frequency offsets. These areas do not change significantly with PFD changes.
For the subsequent measurements, the reference will be set at 375 MHz and the synthesizer set to 9-GHz
output. A 9-GHz clock is convenient for clocking RF sampling data converters like the AFE7950 operating in
S-band or X-band.

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Pre-multiplier Stage Performance

4 Pre-multiplier Stage Performanceshows a block diagram of the 3x pre-multiplier stage using the TRF37C75 amplifier. Figure 2-3 compares thephase noise performance of the pre-multiplier stage with that of the signal generator. Table 2-2 reports theintegrated jitter performance for each configuration.
VCC = 3.6 V
BPF

XO
491.52 MHz

1 dB
TRF37C75

1474.56 MHz

Figure 4-1. 3x Pre-multiplier Stage

Figure 4-2. Phase Noise Comparison of 1474.56 MHz Signal
As expected, the SMA100B provides the best output at 1474.56 MHz. The 3x multiplied Wenzel oscillator
performance is also quite good. Its sweep is nearly identical to the ideal response when the input performance isdegraded by 20 * log (n), where n = 3 as the multiplication factor. As before, the multiplied-up Wenzel approach
is significantly better than the Agilent PSG.
Table 2-2: Integrated RMS Jitter at 1474.56 MHz
Frequency

SourceRMS Jitter

1474.56 MHz

R&S SMA100B

8.1 fsWenzel Osc - 3x

22.2 fs

Agilent PSG

35.4 fs

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4.1 External VCO Loop Filter Design
The gain (kV) of the external VCO is significantly different than the internal VCO of the LMX2820. As such, theloop filter must be modified to achieve optimum performance. Use TI’s PLLatinum™ Simulation Software toolversion 1.6.0 or later to optimize the loop filter for the external VCO.
Within the PLLatinum simulation GUI, select the LMX2820 from the Select Device menu. This will pre-load thestandard configuration for the device. Adjust the following parameters to reflect the set-up configuration andexternal VCO parameters:
•
•
•
•
•

Fosc, Fpfd: 375 MHz highest PFD frequency yields best phase noise
Fout, FVCO: 9000 MHz set the VCO frequency to 9 GHz
KVCO: 0.6 MHz/V VCO gain extracted from its data sheet
Change Filter Designer > 3rd-order filter
Select Active B topology

Also toggle the Advanced radial button under Feature Level. Within the Phase Noise tab, load a user-specified
phase noise file reflecting the reference frequency of the system. This analysis uses a file derived from themeasured performance of the SMA100B signal generator operating at 375 MHz. Next, load a file for the open
loop phase noise of the external VCO (either from measurement or from the device data sheet). Table 4-1 shows
the values used in this analysis.
Table 4-1. Open Loop Phase Noise Parameters for the Z-Comm DRO9000A
Frequency Offset (Hz)Phase Noise (dBc/Hz)

Notes

1000

-77.8

From data sheet

10000-106.2

From data sheet

100000-126.5

From data sheet

10000000-146

Measured

20000000-150

Measured

40000000-154

Measured

100000000-154

MeasuredIn the Integrated Noise section, change the limits of integration as desired. For this analysis, the limits are 10
kHz to 40 MHz. Pushing the start frequency out to 10 kHz focuses more importance on the PLL and VCO
performance and less on the reference frequency performance. For convenience, on the Filter Design tab in theFilter Optimizer section, select “Jitter (fs)” from the pull-down menu. This displays the simulated integrated jitter
performance on the tab without having to switch to the Phase Noise tab to see the results.
The active loop filter uses a 3rd-order topology corresponding to the Active B topology. The simulation toolgraphs the composite phase noise performance along with the individual contributor components of the VCO
and PLL. The default loop filter component values in the simulator will yield a peaky phase noise response
once the previously-mentioned parameters are changed. This is primarily due to the very low VCO gain of theexternal VCO. Use the simulator to adjust loop filter values for the optimum response. The general strategy is todecrease the loop bandwidth of the filter to take advantage of the low VCO noise performance.
There are no absolute right values for the loop filter. There are a variety of combinations that will yield goodresults. The Calculate Loop Filter tool in the PLLatinum simulation tool assists with getting close to the goal.
Adjust specific components to maintain minimum values or realizable values. From there, additional trial-anderror tweaks achieve optimal jitter performance.
For this analysis, the loop filter bandwidth is around 41 kHz. Figure 4-3 shows the simulation results. Disregard
the warning related to the PFD frequency; anything less than 400 MHz is acceptable. Also disregard the warningon the capacitor value C1; keeping the value above 1.5 nF is preferable. Table 4-2 lists the loop filter component
values for one optimized solution. The simulated RMS jitter from 10 kHz to 40 MHz is just under 14 fs.

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Pre-multiplier Stage Performance

Figure 4-3. External VCO PLLatinum™ Simulation GUI Loop Filter
Table 4-2. Active Loop Filter Component Values
Simulation Reference Designator

Value

C1

6.8 pF

C2

47 nF

R2

680 Ω

C3

2.2 nF

R3

18 Ω

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4.2 Active Loop Filter Implementation
Figure 4-4 shows the block diagram for the external VCO and the active loop filter. There are a few key elements
to highlight with the topology. When using the external VCO, there is no internal feedback mechanism to feed
the PFD circuit. Use an external splitter to split the VCO output to the LMX2820 RF input and to the ultimate
synthesizer output. If needed, use an external RF amplifier to boost the synthesizer output and compensate forthe splitter loss.
The op amp is a critical component. Select a device that is low noise and supports rail-to-rail outputs. If
the output cannot get down to 0 V, then utilizing the entire tuning range is not possible. For a single supply
operation, bias the positive terminal at a suitable common-mode voltage. This voltage is roughly half of the
maximum charge pump voltage from the device. For this design, a voltage divider operating on a 10-V rail sets
the Vcm to 1.2 V.
The op amp is the OPA211. This device has a very low output noise voltage with suitable bandwidth andrail-to-rail output capability. Table 4-3 shows the key specs of the OPA211A.
Table 4-3. Key OPA211 Op-Amp Specifications
Parameter

Specification

Low Voltage Noise (1 kHz)

1.1 nV/√Hz)

Gain BW Product (G = 100)80 MHzSlew rate

27 V/μs

Figure 4-4. Block Diagram of the External VCO Configuration

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Pre-multiplier Stage Performance

4.3 External VCO Performance Results
Figure 4-5 shows the external VCO phase noise plot compared to the LMX2820 operating with internal VCO.
The SMA100B signal generator provides the reference signal. Reference signal power from the generator isset to 14 dBm to compensate for board trace losses and to ensure a large signal swing (and hence high slewrate) at the reference pin input of the LMX2820. The performance includes active loop filter with the OP211A
op amp and the Qorvo NBB-312-T1 output power amplifier. Table 4-4 lists the RMS jitter performance at 9 GHz
integrated from 10 kHz to 40 MHz. The phase noise plot shows equivalent performance between the internal
VCO and the external VCO out to around a 10-kHz offset. Performance less than 10-kHz offset is still dominatedby PLL and reference frequency performance. After which, the superior performance of the external VCO itself
dominates. As an example, the spot noise improvement at 1-MHz offset between the external VCO and internal
VCO is over 20 dB. Overall, the external VCO with active loop filter yields over a 20-fs improvement in RMS
jitter.

Figure 4-5. External VCO Phase Noise Compared to LMX2820 Internal VCO
Table 4-4. External VCO RMS Jitter Performance Comparison
PFD

N-Divider

RF OutInternal VCO

External VCO

375 MHz24

9000 MHz37.9 fs

13.2 fs

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5 External PFD Topology
One of the main noise contributors in the PLL is the N-divider. For high-frequency applications, the N-divider
must be fairly large to divide down to a more reasonable low-reference frequency. The external PFD approach
uses an external mixer to bypass the internal N-divider. The RF mixer down-converts the VCO frequency to the
PFD frequency directly. Of course, for there to be an improvement, the mixing operation must be inherently lower
noise compared to the internal dividers. This requires the mixer LO to be low noise in itself. It may seem a bit
contradictory to use the LMX2820 for generating a frequency tone that requires another frequency tone for an
LO source. This is addressed in the subsequent section.
The TIDA-010230 reference design also provides an option to run with external PFD. Reference the block
diagram in Figure 5-1. The output of the internal VCO is amplified and fed into the RF input of the mixer. Properly
select the LO frequency to mix the VCO output down to the PFD frequency. The LMX2820 provides an external
PFD divider to further reduce the frequency down to the reference if needed. Best performance is when this
divider is bypassed (that is, kept at 1).

Figure 5-1. Block Diagram of the External Mixer, PFD Topology
Although this topology requires external circuitry and an additional LO source, it still uses the internal VCO. This
allows the full range of the VCO to generate frequencies up to 22 GHz.

5.1 External PFD Loop Filter Modification
When using the external PFD feature, the effective N-divider is 1 and the loop filter must be modified to maintain
optimum results. The general strategy is to increase the loop bandwidth to take advantage of the low PLL noise
as much as possible.
Use the PLLatinum simulation tool to provide a guide to optimize performance. To begin, start with the default
values of the LMX2820 setup. As before, load the specific reference phase noise performance file. Keep thedefault VCO configuration as the internal VCO is still operational. Adjust the limits of integration to 10 kHz to 40
MHz as before. Change the charge pump current to 7 mA; this is the maximum value when operating in external
PFD mode. Modify the loop filter to a 2nd-order passive topology; a simplified configuration is sufficient for theminimum divider case.
The tool does not specifically have a mode for external PFD operation. To simulate the external PFD
configuration, set the Fosc and Fpd to the same value as the VCO output. This tricks the tool into setting
the N-divider to 1. Disregard the red error highlights. With the default loop filter values and the N-divider set toone, the initial phase noise response shows a peaking response around 10 MHz.

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External PFD Topology

Adjust the loop filter values to increase the bandwidth to compensate. Initially target a loop bandwidth around2000 kHz. The automatic Calculate Loop Filter brings the values close to what is needed; afterwards, manually
adjust loop filter values to hone in on an optimized and realizable filter. As before, there is no one absolute loop
filter solution; Figure 5-2 shows the PLLatinum simulation set-up for the external PFD configuration used in thisanalysis and Table 5-1 shows the modified loop filter values.

Figure 5-2. PLLatinum™ Simulation for External PFD
Table 5-1. External PFD Loop Filter Values
Simulation Reference Designator

Value

C1

470 pFC2

150 nF

R2

12 Ω

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5.2 External PFD Measurement Results
For the baseline measurements, the Rohde SMA100B supplies the LO signal to the mixer. It is critical that theLO signal be low phase noise with very good low frequency offset performance. Poor phase noise performancein the LO translates directly to the synthesizer output. With the external PFD configuration, the phase noiseof the reference is less critical; for these experiments the Agilent PSG signal generator supplies the reference
signal.
The LMX2820 output frequency is 9375 MHz. The N-divider is 25. For internal VCO calibration purposes, theinternal N-divider must still be set up properly. Switch to the external PFD mode and toggle the frequency
calibration bit. The device must first calibrate the internal VCO with the internal dividers before switching to theexternal PFD input. The LO frequency is 9000 MHz. This sets the PFD frequency to 375 MHz. Figure 5-3 shows
the phase noise results with the external PFD compared to the external VCO response. Notice the improved
intermediate frequency offset performance due to the effective low N-divider setting and the normal internal VCO
performance at the high frequency offsets.

Figure 5-3. LMX2820 External PFD Phase Noise Performance

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Putting it Together in the Real World

6 Putting it Together in the Real World
The performance of the LMX2820 with an external PFD using the Rohde SMA100B as the LO source yields
excellent phase noise performance. The performance is very attractive, but not practical in a real application. A
realistic option is to use an additional LMX2820 as the mixer LO. Using the standard LMX2820 configuration withinternal VCO as the LO yields worse performance than just using the device directly. That is expected given the
LO source is not improved compared to the source. Alternatively, use a second LMX2820 configured with theexternal VCO as the LO source. Figure 6-1 shows the block diagram approach for using two LMX2820 devices.
The external VCO is followed by cascaded amplifiers to increase the LO drive signal to 16 dBm (or higher). The
mixer needs a high LO drive level to ensure best dynamic range and linearity required for best phase noise
performance.

Figure 6-1. Dual LMX2820 Approach for a Real-World Solution

6.1 Real-World Performance Results
Figure 6-2 shows the phase noise performance of the dual LMX2820 approach compared with the stand-alone
external PFD (using SMA100B as the LO), the stand-alone external VCO, and the internal VCO. Table 6-1
shows the comparison of integrated jitter between the different configurations.

Figure 6-2. Dual LMX2820 Real-World Phase Noise Results

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Table 6-1. Integrated RMS Jitter Performance Comparison With External PFD
RF Out Freq

SourceIntegrated Phase Noise

9000 MHzInternal VCO

37.9 fs

9000 MHz

External VCO

13.2 fs

9375 MHz

External PFD (LO = SMA100B)

13.9 fs

9375 MHz

External PFD (LO = LMX2820 with Ext VCO)

18.5 fs

The dual LMX2820 approach yields an integrated phase noise performance under 20 fs. Though not quite as
good as the stand-alone external VCO or external PFD with SMA100B as the LO, it is a significant improvement
to the internal VCO and provides a response that is comparable to many high-end signal generators. It is areal-world topology that supports the most stringent communication and defense applications.

6.2 Why use the Dual Approach?
Why use the dual LMX2820 approach when something like the external VCO yields better integrated
performance? The external PFD topology is still using the internal VCO and thus has the flexibility to tune
the frequency over a large range as well as use the internal output dividers. This provides additional flexibility toadjust the synthesizer frequency output that the external VCO approach cannot accomplish.
One option is to use the external PFD divider to adjust the frequency. In essence, this is equivalent to theN-divider adjustment used to change the frequency in the same way. The benefit in the external PFD topology
is that the starting point is at the minimum divider value possible (that is, 1). Figure 6-3 shows the external PFD
performance response as external PFD divider is adjusted from 1 to 6. This is measured as a relative reference
using the SMA100B as the LO source. Of course, the dividers can be further increased to keep moving theoutput frequency up as desired. Table 6-2 reports the integrated phase noise performance over PFD divider
settings.

Figure 6-3. External PFD Over PFD Divider

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Conclusion

Table 6-2. External PFD Over PFD Divider
PFD Divider

RF Out Freq

Integrated Phase Noise

19375 MHz13.2 fs2

9750 MHz13.7 fs

3

10,125 MHz

17.8 fs

4

10,500 MHz

20.3 fs

5

10,875 MHz

21.6 fs

6

11,250 MHz

23.9 fs

The topology also provides the option to use the output dividers to extend the frequency range further. Figure 6-4
shows the phase noise performance across output divider settings from 2 to 16. Table 6-3 reports the integrated
phase noise performance across the output divider settings.

Figure 6-4. Phase Noise Over Output Divider Settings
Table 6-3. Integrated Phase Noise Over Output Divider Settings
Output Divider

RF Out Freq

Integrated Phase Noise19000 MHz

13.0 fs

24500 MHz

14.0 fs

42250 MHz

20.5 fs

81125 MHz17.3 fs

16

562.5 MHz22.3 fs

7 Conclusion
The LMX2820 is a good low-noise RF synthesizer device. Two alternative topologies provide improved
performance that rival high-end test equipment: external VCO and external PFD. Combining these two
approaches yields a real-world topology that provides extremely good phase noise performance while also
providing flexibility to adjust the frequency output.
The improved synthesizer performance provides realizable clock and LO solutions for stringent spot noise
applications in high-interference systems like wireless infrastructure transceivers and software defined radios.
The excellent integrated RMS jitter performance is suitable for clock solutions in high-resolution radar systems
and high-QAM rate communication systems.

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LMX2820 RF Synthesizer Phase Noise Improvement With Alternative
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Copyright © 2023 Texas Instruments Incorporated

17

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8 Revision History
Changes from Revision * (April 2022) to Revision A (May 2023)
Page• Updated the numbering format for tables, figures, and cross-references throughout the document ................ 1• Changed 3 GHz to 3 MHz ................................................................................................................................. 3• Changed 300 kHz to 300 Hz ............................................................................................................................. 318

LMX2820 RF Synthesizer Phase Noise Improvement With Alternative
Topologies
Copyright © 2023 Texas Instruments Incorporated

SNAA361A – APRIL 2022 – REVISED MAY 2023
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