U.S. patent application number 14/827146 was filed with the patent office on 2017-02-16 for synchronization of unstable signal sources for use in a phase stable instrument.
The applicant listed for this patent is Tektronix, Inc.. Invention is credited to Alexander Krauska.
Application Number | 20170045603 14/827146 |
Document ID | / |
Family ID | 57199871 |
Filed Date | 2017-02-16 |
United States Patent
Application |
20170045603 |
Kind Code |
A1 |
Krauska; Alexander |
February 16, 2017 |
SYNCHRONIZATION OF UNSTABLE SIGNAL SOURCES FOR USE IN A PHASE
STABLE INSTRUMENT
Abstract
A vector network analyzer (VNA) can include a control processor,
a plurality of receivers coupled with the control processor, the
plurality of receivers having a common signal generator source, and
a coupler/power divider network configured to distribute each of a
plurality of source reference signals to a corresponding one of the
plurality of receivers.
Inventors: |
Krauska; Alexander;
(Beaverton, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tektronix, Inc. |
Beaverton |
OR |
US |
|
|
Family ID: |
57199871 |
Appl. No.: |
14/827146 |
Filed: |
August 14, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 35/005 20130101;
G01R 27/28 20130101; H04L 7/0331 20130101 |
International
Class: |
G01R 35/00 20060101
G01R035/00; G01R 27/28 20060101 G01R027/28; H04L 7/033 20060101
H04L007/033 |
Claims
1. A vector network analyzer, comprising: a control processor; a
plurality of receivers coupled with the control processor, the
plurality of receivers having a common signal generator source from
the control processor; and a coupler/power divider network
configured to distribute each of a plurality of source reference
signals to a corresponding one of the plurality of receivers.
2. The vector network analyzer of claim 1, wherein each of the
plurality of receivers has an independent local oscillator
(LO).
3. The vector network analyzer of claim 2, wherein at least one
independent LO is configured to generate multiple LO signals.
4. The vector network analyzer of claim 1, wherein each of the
plurality of receivers is one of a group consisting of: a
superheterodyne receiver, a homodyne receiver, and a direct
conversion receiver.
5. The vector network analyzer of claim 1, wherein the common
signal generator source is a direct signal source.
6. The vector network analyzer of claim 5, wherein the direct
signal source is one of a group consisting of: a voltage controlled
oscillator (VCO) and a phase-locked loop (PLL).
7. The vector network analyzer of claim 5, wherein the direct
signal source is one of a group consisting of: a direct digital
source and a direct analog source.
8. The vector network analyzer of claim 1, wherein the common
signal generator source is an indirect signal source.
9. The vector network analyzer of claim 8, wherein the indirect
signal source is one of a group consisting of: a single LO with a
baseband signal and multiple LOs with a baseband signal.
10. A vector network analyzer, comprising: a control processor; a
receiver coupled with the control processor; switching circuitry
coupled with the receiver; a radio frequency (RF) bridge coupled
with the switching circuitry; a transmission line coupled with the
RF bridge, wherein the transmission line is configured to be
coupled with a load; and a signal generator coupled with the RF
bridge.
11. The vector network analyzer of claim 10, wherein the RF bridge
is configured to provide a plurality of reference signals to the
switching circuitry.
12. The vector network analyzer of claim 10, wherein the signal
generator is configured to provide a source signal to the RF
bridge.
13. The vector network analyzer of claim 10, further comprising a
local oscillator (LO) coupled with the receiver.
14. The vector network analyzer of claim 10, further comprising a
local oscillator (LO) coupled with the signal generator.
15. The vector network analyzer of claim 14, further comprising a
switch coupled with the signal generator and configured to switch
between the RF bridge and the receiver.
16. The vector network analyzer of claim 14, wherein the control
processor is configured to phase lock the signal generator to a
common reference.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to electronic test
and measurement devices, such as Vector Network Analyzers (VNAs),
Vector Signal Analyzers, Spectrum Analyzers, Vector Signal
Generators, and signal generators.
BACKGROUND
[0002] In prior instruments, such as a tracking generator or vector
network analyzer (VNA), a plurality of phase-stable measurements of
a device under test (DUT) reflection and/or transmission must be
made. Single or multiple generators and receivers share a common
local oscillator (LO) to assure phase stability. Calibration of the
system is performed using external reflection standards, which rely
on coherent phase between the calibration moment and the
measurement moment. For reasons of cost reduction and
simplification of the hardware, it would be desirable to use
phase-incoherent but frequency-stable LO sources for the receiver
and generator rather than sharing a common synthesizer
architecture. The common VNA has a reflection bridge or coupler
arrangement of various types on the generator port. A signal
reference coupled from the generator is routed to the receiver but
has a phase error that is proportionate to the reflection
coefficient of the (arcsin(V.sub.ref/V.sub.norm)), making the
reference generator phase relative to the receiver difficult to
obtain from this port alone without relying on the phase coherence
of a common LO system between the generator and receiver.
[0003] FIG. 1 is a block diagram illustrating an example of a prior
vector network analyzer (VNA) or tracking generator 100 having
multiple receivers 110 and 112 and a shared signal 125 (e.g., from
a control processor 120 by way of an LO 116). In the example, a
common source 102 provides an injection signal to a radio frequency
(RF) bridge 106 (e.g., via a transmission line 104), as well as
reference signals 107a and 107b to multiple receivers 110 and 112,
respectively.
[0004] It should be noted that, while two receivers 110 and 112 are
shown to measure two signals (e.g., Reference and Reflection ports
of a bridge), any number of multiple receivers can be used to
measure a high number of signals from more complex multi-channel
bridges, couplers, or similar networks. Multiple receivers can be
eliminated with a single receiver if a phase-stable switch can be
connected in such a way that the bridge loading is not disturbed
when the paths are switched.
[0005] FIG. 2 is a block diagram illustrating an example of a prior
VNA or tracking generator 200 having a single receiver 210 and a
shared signal 225 (e.g., from a control processor 220 by way of an
LO 216). Similar to the VNA or tracking generator 100 illustrated
by FIG. 1, a common source 202 provides an injection signal to a
radio frequency (RF) bridge 206 (e.g., via a transmission line
204), as well as reference signals 207a and 207b to switching
circuitry 209 that is coupled with the receiver 210. In general,
the shared signal may be the bridge stimulus itself or an LO
created in a phase stable way within the signal source.
SUMMARY
[0006] Implementations of the disclosed technology generally
include systems or devices that use an additional signal path in
order to allow for a relative phase measurement between a generator
and a receiver, insensitive to external load conditions. Such
embodiments may advantageously allow a receiver and generator
having relatively unstable independent local oscillators (LOs) to
be used in a phase-stable measurement of network response. This may
advantageously allow a single receiver and generator to establish
their relative phase or, in embodiments involving multiple
receivers and multiple generators, to establish their relative
phase.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a block diagram illustrating an example of a prior
vector network analyzer (VNA) or tracking generator having multiple
receivers and a shared signal.
[0008] FIG. 2 is a block diagram illustrating an example of a prior
VNA or tracking generator having a single receiver and a shared
signal.
[0009] FIG. 3 is a block diagram illustrating an example of a VNA
or tracking generator having a calibration path in accordance with
certain implementations of the disclosed technology.
[0010] FIG. 4 is a block diagram illustrating an example of a VNA
or tracking generator having a common generator source in
accordance with certain implementations of the disclosed
technology.
[0011] FIG. 5 is a block diagram illustrating a first example of a
VNA or tracking generator having multiple receivers that are
synchronized by a common reference signal in accordance with
certain implementations of the disclosed technology.
[0012] FIG. 6 is a block diagram illustrating a second example of a
VNA or tracking generator having multiple receivers that are
synchronized by a common reference signal in accordance with
certain implementations of the disclosed technology.
[0013] FIG. 7 is a block diagram illustrating an example of a VNA
or tracking generator having multiple signal sources that are
synchronized by a single receiver in accordance with certain
implementations of the disclosed technology.
DETAILED DESCRIPTION
[0014] Implementations of the disclosed technology generally
include electronic test and measurement devices, such as vector
network analyzers (VNAs) having a calibration path. Such
embodiments may advantageously include separate signal sources in
the receiver(s) and signal source to allow for higher stability and
accuracy in the bridge measurement. Also, variable static phase
offsets in either the receive synthesizer or source synthesizer may
be sensed and removed as an error term in the measurement. Further,
costs may be reduced due to the availability of single integrated
circuit (IC) integrated synthesizers that cover wide bandwidths at
low cost.
[0015] FIG. 3 is a block diagram illustrating a first example of a
VNA or tracking generator 300 having a load 302, a transmission
line 304, a radio frequency (RF) bridge 306 provide reference
signals 307a and 307b to switching circuitry 309, and a calibration
path in accordance with certain implementations of the disclosed
technology. In the example, a separate signal source 325 (e.g., by
way of a generator 321, an LO 317, and a switch 314) and receive
reference 326 are shown with a phase shift 315 shown in series with
the signal source to represent the random phase offset to the
receive channel. Each of the signal sources is phase locked to a
common reference and controlled by a common control processor 320,
and the signal source may have an unknown phase. While a single
receiver 310 is shown, it should be noted that multiple receivers
may be synchronized using similar implementations.
[0016] In the example, the signal channel generator 321 has a
single channel receiver for sensing the magnitude and phase of a
single reflection bridge/coupler 306, e.g., used in a one-port VNA.
The generator 321 and receiver 310 may use either continuous wave
or modulated data. The receiver(s) may be constructed each having
an independent local oscillator, e.g., with independent phase. The
phase offset 315 from the source may be determined by sampling the
"source Reference path." Here, Si may either refer to a switch or a
coupling or power dividing network. In embodiments where a single
receiver is used to sample a single port or multiple bridge ports,
the switch may be designed to provide a consistent load to the
bridge in all switch positions. This may be accomplished using
signal path attenuation, impedance matching, buffering by
amplification, and terminated switch networks, for example.
[0017] FIG. 4 is a block diagram illustrating an example of a VNA
or tracking generator 400 having a common generator source (e.g.,
from a control processor 420 by way of an LO 317) in accordance
with certain implementations of the disclosed technology. In the
example, multiple receivers 410, 411, and 412 having independent
LOs 410a, 411a, and 412a, respectively, and multiple phase offsets
may be synchronized to a common reference. In this view, the
multiple source reference signals are distributed by way of a
coupler/power divider network 445. In alternate embodiments, a
switch may be implemented instead of the coupler/power divider
network 445.
[0018] In the example, the receivers 410-412 and generators can be
phase synchronized by tuning each to the same frequency, switching
to the "Source Reference" signal, and measuring the relative phase.
Frequency offsets between the source and receivers may be
accommodated if these signals are within the processing bandwidth
of the receivers 410-412. It should be noted that the receivers
410-4112 are generally analog or digital receivers with
superheterodyne, homodyne, direct conversion, or similar receiver
techniques. Single or multiple LO signals may be generated by each
receiver. For example LO 1 (410a) may be actually three LO signals
(e.g., LO1a, LO2b, and LO1c for a three-stage superheterodyne
converter). The generator may either be a direct signal source
(e.g., a VCO and PLL, direct digital source, or direct analog
source) or an indirect signal source (e.g., with a local oscillator
and baseband signal, or multiple location oscillators and a
baseband signal), with either a modulated or continuous wave
baseband signal.
[0019] FIG. 5 is a block diagram illustrating a first example of a
VNA or tracking generator 500 having multiple receivers that are
synchronized by a common reference signal in accordance with
certain implementations of the disclosed technology. In the
example, a single control processor 520 may control multiple
receivers 510, 511, and 512 having independent LOs 510a, 511a, and
512a, respectively with random phase offsets. N Source reference
signals are routed from a single generator. While simplified signal
source is shown in the figure, this signal source may be an
indirect signal source (e.g., with a local oscillator and baseband
signal, or with multiple LOs and a baseband signal) with either a
modulated or continuous wave baseband signal or a direct signal
source such as a VCO and PLL, direct digital source, or direct
analog source. The phase offset represents random phase offset that
may be present between each receiver and the generator.
[0020] FIG. 6 is a block diagram illustrating a second example of a
VNA or tracking generator 600 having multiple receivers that are
synchronized by a common reference signal in accordance with
certain implementations of the disclosed technology. In the
example, synchronizer circuitry 601 consists of a signal source
(Gen1), a common reference clock (e.g., which produces 10 MHz 1 . .
. 10 MHz N outputs to synchronize n external spectrum analyzers
610, 611, and 612), a 10 MHz or other suitable signal to
synchronize the reference generator "Gen 1", signal routing and
switching circuitry 610a, 611a, and 612a, respectively, to each
spectrum analyzer RF input, and N-RF inputs. Signal 1 to Signal n
inputs to the control processor 620 may include several USB data
signals or any other common data bus, such as USB/PXI/VXI etc.
[0021] FIG. 7 is a block diagram illustrating an example of a VNA
or tracking generator 700 having multiple signal sources that are
synchronized by a single receiver in accordance with certain
implementations of the disclosed technology. In the example,
generator channel SPDT switches may be of internal-terminated form
when the path is open. The stability of bridge response during
switching may be improved using buffors, amplification,
attenuation, or other suitable mechanisms. Signal 1 may be
modulated or a continuous wave signal. The signal source may be a
direct source of heterodyne source. The phase offset of each
generator may be sensed relative to the others by way of a common
receiver, for example.
[0022] Having described and illustrated the principles of the
invention with reference to illustrated embodiments, it will be
recognized that the illustrated embodiments may be modified in
arrangement and detail without departing from such principles, and
may be combined in any desired manner. And although the foregoing
discussion has focused on particular embodiments, other
configurations are contemplated.
[0023] In particular, even though expressions such as "according to
an embodiment of the invention" or the like are used herein, these
phrases are meant to generally reference embodiment possibilities,
and are not intended to limit the invention to particular
embodiment configurations. As used herein, these terms may
reference the same or different embodiments that are combinable
into other embodiments.
[0024] Consequently, in view of the wide variety of permutations to
the embodiments that are described herein, this detailed
description and accompanying material is intended to be
illustrative only, and should not be taken as limiting the scope of
the invention. What is claimed as the invention, therefore, is all
such modifications as may come within the scope and spirit of the
following claims and equivalents thereto.
* * * * *