U.S. patent application number 15/895648 was filed with the patent office on 2019-08-15 for adjustable dynamic range signal detection circuit.
The applicant listed for this patent is TEXAS INSTRUMENTS INCORPORATED. Invention is credited to Jikai Chen, Yanli Fan, Yuan Rao.
Application Number | 20190253091 15/895648 |
Document ID | / |
Family ID | 67477674 |
Filed Date | 2019-08-15 |
United States Patent
Application |
20190253091 |
Kind Code |
A1 |
Chen; Jikai ; et
al. |
August 15, 2019 |
ADJUSTABLE DYNAMIC RANGE SIGNAL DETECTION CIRCUIT
Abstract
A circuit includes a sensor configured to receive an input
signal and to provide a sensor output signal in response to the
received input signal. A plurality of mirror circuits are
configured to receive the sensor output signal from the sensor and
to generate mirror circuit output signals. The plurality of mirror
circuits includes a first mirror circuit and at least a second
mirror circuit. The first mirror circuit increases its respective
mirror circuit output signal until its saturation value is reached.
The second mirror circuit increases its respective mirror output
signal if the sensor output signal is above a threshold value and
until its saturation value is reached.
Inventors: |
Chen; Jikai; (Allen, TX)
; Rao; Yuan; (Allen, TX) ; Fan; Yanli;
(Allen, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TEXAS INSTRUMENTS INCORPORATED |
Dallas |
TX |
US |
|
|
Family ID: |
67477674 |
Appl. No.: |
15/895648 |
Filed: |
February 13, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05F 3/26 20130101; H04B
1/16 20130101; H03K 5/153 20130101; G05F 3/30 20130101 |
International
Class: |
H04B 1/16 20060101
H04B001/16; H03K 5/153 20060101 H03K005/153; G05F 3/26 20060101
G05F003/26; G05F 3/30 20060101 G05F003/30 |
Claims
1-6. (canceled)
7. A circuit, comprising: a sensor configured to receive an input
signal and to provide a sensor output signal in response to the
received input signal; and a plurality of mirror circuits
configured to receive the sensor output signal from the sensor and
to generate mirror circuit output signals, the plurality of mirror
circuits include a first mirror circuit and at least a second
mirror circuit, wherein the first mirror circuit increases its
respective mirror circuit output signal until its saturation value
is reached and the second mirror circuit increases its respective
mirror output signal if the sensor output signal is above a
threshold value and until its saturation value is reached; wherein
each of the plurality of mirror circuits include a pair of
transistor switch devices coupled via a common gate connection, the
pair of the transistor switch devices include a length parameter
that defines a current capability of the transistor switch devices;
wherein one of pair of transistor switch devices for one of the
plurality of mirror circuits is configured with a length parameter
that is greater than the length parameter of another pair of
transistor switch devices for at least one other of the plurality
of mirror circuits.
8-16. (canceled)
17. A circuit, comprising: a sensor configured to receive an input
signal and to provide a sensor output signal in response to the
received input signal; a mirror circuit configured to receive the
sensor output signal from the sensor and to generate a mirror
circuit output signal, the mirror circuit increases a magnitude of
the mirror circuit output signal based on increases of the sensor
output signal and before the mirror circuit reaches a saturation
value; at least one other mirror circuit configured to receive the
sensor output signal from the sensor and to generate at least one
other mirror circuit output signal, the at least one other mirror
circuit output signal is generated in response to the sensor output
signal and if the sensor output signal is above a threshold value,
the mirror circuit output signal and the at least one other mirror
circuit output signal are combined to generate a detection signal
to indicate a signal strength of the sensor output signal; wherein
each of the mirror circuit and the at least one other mirror
circuit includes a pair of transistor switch devices coupled via a
common gate connection, the pair of the transistor switch devices
include a length parameter that defines a current capability of the
transistor switch devices; wherein one of pair of transistor switch
devices for the mirror circuit is configured with a length
parameter that is greater than the length parameter of another pair
of transistor switch devices for the at least one other mirror
circuit.
18. (canceled)
19. A method, comprising: providing a sensor output signal in
response to a received input signal; generating separate mirror
circuit output signals from separate mirror circuits in response to
signal variances of the sensor output signal, wherein each of the
separate mirror circuit output signals are generated in response to
different signal levels of the sensor output signal; and generating
a signal strength indication for the input signal based on
monitoring of the separate mirror circuit output signals.
20. The method of claim 19, further comprising generating the
separate mirror circuit output signals if the sensor output signal
exceeds a threshold value.
Description
TECHNICAL FIELD
[0001] This disclosure relates to electrical circuits, and more
particularly to a signal detection circuit that dynamically changes
its sensitivity level based on detected input conditions.
BACKGROUND
[0002] Received signal strength detectors in some wireless, wired,
or optical receivers have to provide low offset current (e.g., 1
microampere) when small input signals are present, while providing
wide (e.g., >1000X) dynamic range for signal detection (e.g.,
signals detected below 1 microampere to a few milliamperes).
Existing circuits employ a single current mirror to replicate the
received signal current at the detector output. Increasing the
channel length (L) of the current mirror to meet the low offset
current requirement results in prohibitively large area for the
respective transistor devices of the single current mirror.
Reducing the channel length helps the current mirror at higher
current values however the low signal response of the detector
suffers. Trimming the offset current adds cost to the circuit and
is not available in many manufacturing processes.
SUMMARY
[0003] This disclosure relates to a signal detection circuit that
dynamically changes its sensitivity level based on detected input
conditions. In one example, a circuit includes a sensor configured
to receive a wireless input signal and to provide a sensor output
signal in response to the received wireless input signal. A
plurality of mirror circuits are configured to receive the sensor
output signal from the sensor and to generate mirror circuit output
signals. The plurality of mirror circuits includes a first mirror
circuit and at least a second mirror circuit. The first mirror
circuit increases its respective mirror circuit output signal until
its saturation value is reached. The second mirror circuit
increases its respective mirror output signal if the sensor output
signal is above a threshold value and until its saturation value is
reached.
[0004] In another example, a circuit includes a sensor configured
to receive an input signal and to provide a sensor output signal in
response to the received input signal. The circuit includes a
mirror circuit configured to receive the sensor output signal from
the sensor and to generate a mirror circuit output signal. The
mirror circuit increases a magnitude of the mirror circuit output
signal based on increases of the sensor output signal and before
the mirror circuit reaches a saturation value. At least one other
mirror circuit is configured to receive the sensor output signal
from the sensor and to generate at least one other mirror circuit
output signal. The other mirror circuit output signal is generated
in response to the sensor output signal and if the sensor output
signal is above a threshold value. The mirror circuit output signal
and the other mirror circuit output signal are combined to generate
a detection signal to indicate a signal strength of the sensor
output signal.
[0005] In yet another example, a method includes providing a sensor
output signal in response to a received input signal. The method
includes generating separate mirror circuit output signals from
separate mirror circuits in response to signal variances of the
sensor output signal. Each of the separate mirror circuit output
signals are generated in response to different signal levels of the
sensor output signal. The method includes generating a signal
strength indication for the input signal based on monitoring of the
separate mirror circuit output signals.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 illustrates an example block diagram of a signal
detection circuit that employs multiple mirror circuits for
detecting input signals.
[0007] FIG. 2 illustrates an example block diagram of a signal
detection circuit that employs two mirror circuits for detecting
input signals.
[0008] FIG. 3 illustrates an example block diagram of a signal
detection circuit that employs three mirror circuits for detecting
input signals.
[0009] FIG. 4 illustrates a circuit example of a signal detection
circuit that employs multiple mirror circuits for detecting input
signals.
[0010] FIG. 5 illustrates an example signal diagram that
illustrates the current output from the mirror circuits of FIG.
4.
[0011] FIG. 6 illustrates an example method for detecting input
signals.
DETAILED DESCRIPTION
[0012] This disclosure relates to a signal detection circuit that
dynamically changes its sensitivity level based on detected input
conditions. The signal detection circuit includes a sensor
configured to receive an input signal (e.g., wireless or wired) and
to provide a sensor output signal in response to the received input
signal. The sensor can be substantially any type of sensor for
receiving signals such as an optical sensor, for example, used in
an optical receiver. Other type sensors may also be employed. A
plurality of mirror circuits are configured to receive the sensor
output signal from the sensor. Each of the mirror circuits
generates mirror circuit output signals in response to the sensor
output signal. The plurality of mirror circuits include a first
mirror circuit and at least a second mirror circuit. The first
mirror circuit increases its respective mirror circuit output
signal until its saturation value is reached. The second mirror
circuit generates a respective mirror output signal if the sensor
output signal is above a threshold value. The mirror output signals
in the subsequent stages increases until their respective
saturation values are reached.
[0013] Each mirror circuit includes a pair of transistor switch
devices that are configured with a length parameter (L) that
defines the current capability of the devices. Two (or more) mirror
circuits with different length parameters L can operate in parallel
to process the sensor output signal from the sensor and over a
large dynamic operating range of the sensor. When the input current
is low (e.g., below a detected threshold value), the mirror circuit
with the largest L parameter is on, and thus presents a low offset
value for the detector at low detected signal levels. When the
input current is high from the sensor (e.g., signal level above
threshold value), the mirror circuit with a smaller L value is
switched on and thus presents high dynamic range to accommodate the
larger input current value. Gradual analog range control and
switching provides continuous operation over the input range,
mitigating possible service interruption by avoiding abrupt digital
range switching.
[0014] As used herein, the term "circuit" can include a collection
of active and/or passive elements that perform a circuit function,
such as an analog circuit or control circuit. Additionally or
alternatively, for example, the term "circuit" can include an
integrated circuit (IC) where all or some of the circuit elements
are fabricated on a common substrate (e.g., semiconductor
substrate, such as a die or chip).
[0015] FIG. 1 illustrates an example of a signal detection circuit
100 that employs multiple mirror circuits for detecting input
signals. The circuit 100 includes a sensor 110 configured to
receive an input signal 120 (e.g., wired or wireless input signal)
and to provide a sensor output signal 124 in response to the
received wireless input signal. A plurality of mirror circuits
shown as mirror circuit 1 though N, with N being a positive
integer, are configured to receive the sensor output signal 124
from the sensor 110 and to generate mirror circuit output signals
130, 134, and 136 from each of the mirror circuits 1 through N. As
used herein, the term mirror circuit refers to a circuit that
employs a pair of transistor switch devices (e.g., metallic oxide
semiconductor device) sharing a common gate connection. One of the
pair of transistors receive an input at their respective source
connection and the other of the pair of switch devices mirrors the
input at an output connection provided by the source connection of
the other device. Another term for the mirror circuit is a current
mirror.
[0016] Each of the plurality of mirror circuits 1-N are configured
to generate the respective mirror circuit output signals 134-136 at
different signal strengths of the sensor output signal. In one
example, the plurality of mirror circuits include the first mirror
circuit shown as mirror circuit 1 and at least a second mirror
circuit shown as mirror circuit 2. The first mirror circuit
increases its respective mirror circuit output signal 130 until its
saturation value is reached. The second mirror circuit generates a
respective mirror output signal 134 if the sensor output signal is
above a threshold value and until its saturation value is reached.
As shown, mirror circuit 2 and mirror circuit N may also include
threshold sensing and switch circuits 140 and 144, respectively.
These circuits 140 and 144 enable mirror circuit 2 and/or mirror
circuit N to turn on if the input signal exceeds a threshold. The
mirror circuit 1 turns on at low current values and continues to
conduct up to a saturation point where the circuit saturates on its
own and thus does not employ its own threshold and switching
circuit. Large dynamic range is provided by the circuit 100 since
mirror circuit 1 is configured with a large length parameter (L) to
support low current values and low offsets since the transistor
pair of the mirror circuit can be tightly matched by having a
higher configured L value. At higher current values of the input
signal 120, the subsequent mirror stages 2 though N can be
activated via their respective threshold and switching circuits 140
and 144 based on the detected current level of the input. These
mirror circuits 2-N can be dynamically switched on based on input
current conditions and configured with lower L values to support
higher currents.
[0017] The mirror circuit output signals 130-136 can be generated
by the plurality of mirror circuits 1-N if the sensor output signal
124 exceeds a threshold value (e.g., threshold set for 10
microamperes). As will be shown and described below with respect to
FIG. 4, the circuit 100 can include a constant current source that
includes a current source output configured to set the threshold
value. Each of the plurality of mirror circuits 1-N includes a pair
of transistor switch devices coupled via a common gate connection.
The pair of the transistor switch devices in each mirror circuit
1-N include a length parameter (L) that defines a current
capability of the transistor switch devices. One of pair of
transistor switch devices for one of the plurality of mirror
circuits such as mirror circuit 1 can be configured with a length
parameter that is greater than the length parameter of another pair
of transistor switch devices for at least one other of the mirror
circuits 2-N.
[0018] The sensor 110 can be an optical sensor, a current sensor,
or a voltage sensor to receive the input signal 120 and to provide
the sensor output signal 124 in response to the received input
signal. An amplifier circuit (see e.g., FIG. 4) can be provided to
set a bias voltage for the sensor 110 based on a reference voltage.
A detection circuit 150 (e.g., resistor or network to convert
output current from mirror circuits to voltage which can be
digitized and/or compared for signal strength value) can be
configured to receive the mirror circuit output signals 130-136
from each of the mirror circuits 1-N and combine them to determine
the signal strength of the input signal 120. The detection circuit
1-N generates a detection circuit output signal 154 that indicates
the signal strength of the wireless input signal 120. In one
example, the circuit 100 can be employed as a received signal
strength indicator for an optical receiver where the detection
circuit indicates a signal strength value for the input signal 120
which indicates received optical signal strength. In other
examples, the circuit 100 can be employed as a wireless or wired
signal detector where signals of varying signal strengths are
detected and reported via the detection circuit 150.
[0019] FIG. 2 illustrates an example of a signal detection circuit
200 that employs two mirror circuits 210 and 220 for detecting
input signals. The mirror circuit 210 includes transistor switch
devices 230 and 234 which share a common gate connection. The
mirror circuit 220 includes transistor switch devices 240 and 244
which share a common gate connection. Each of the mirror circuits
210 and 220 receive a wireless signal output at transistor switch
devices 230 and 240 from a sensor 250 (e.g., optical sensor) and
provide an output via switch devices 234 and 244, respectively, to
a detection circuit 254. As shown, the switch devices of mirror
circuit 210 have a length parameter (L) that is configured greater
than the length parameter of the mirror circuit 220. A threshold
and switching circuit 260 is provided to turn on the mirror circuit
220 at higher current values of the sensor output signal. An
amplifier 264 receives a reference voltage 270 and is provided to
set a desired bias voltage for the sensor 250.
[0020] FIG. 3 illustrates an example signal detection circuit 300
that employs three mirror circuits 310, 314, and 320 for detecting
input signals. Similar to FIG. 2, the mirror circuits 310, 314, and
320 include transistor switch devices which share a common gate
connection. Each of the mirror circuits 310-314 receive a wireless
signal from a wireless sensor 350 (e.g., optical sensor) and
provide an output via to a detection circuit 354. The switch
devices of mirror circuit 310 have a length parameter (L) that is
configured greater than the length parameter of the mirror circuit
314 and 320, whereas the length parameter L for the transistor
switch devices mirror circuit 314 can be set greater than the
length parameter of the transistor switch devices of the mirror
circuit 320. A threshold and switching circuit 360 and 362 is
provided to turn on the mirror circuits 314 and 320 respectively at
higher current values of the sensor output signal. An amplifier 364
receives a reference voltage 370 and is provided to set a desired
bias voltage for the sensor 250. Although 2 and 3 mirror circuit
stages are shown in the examples of FIGS. 2 and 3, N such mirror
circuit stages can be provided as previously described with respect
to FIG. 1.
[0021] FIG. 4 illustrates a circuit example of a signal detection
circuit 400 that employs multiple mirror circuits for detecting
input signals. A sensor 404 is configured to receive an input
signal (e.g., optical signal) and to provide a sensor output signal
406 in response to the received input signal. A mirror circuit 410
(including transistors M7 and M8) is configured to receive the
sensor output signal 406 from the sensor 404 and to generate a
mirror output signal 414 to a detection circuit 416. The mirror
circuit 410 increases a magnitude of the mirror circuit output
signal 414 based on increases of the sensor output signal 406 and
before the mirror circuit reaches a saturation value. At least one
other mirror circuit shown as mirror circuit 420 (including
transistors M9 and M10) in this example is configured to receive
the sensor output signal from the sensor 404 and to generate at
least one other mirror circuit output signal 424 to the detection
circuit 416. The other mirror circuit output signal 424 is
generated in response to the sensor output signal 406 and if the
sensor output signal is above a threshold value. The mirror circuit
output signal 414 and other mirror circuit output signal 424 are
combined at the detection circuit 416 and to generate a detection
signal to indicate a signal strength of the sensor output signal
406.
[0022] A constant current source 430 includes a current source
output configured to set the threshold value. A threshold detector
mirror circuit 434 consisting of transistor switch devices M1, M2,
and M3 is configured to compare the sensor output signal 406 to the
current source output. The threshold detector mirror circuit 434 is
configured to generate control signals 440 and 444 to activate the
mirror circuit 420 if the sensor output signal 406 exceeds the
threshold value set by the current source 430. A switching circuit
450 includes transistor switch devices M4, M5, and M6 that
activates the mirror circuit 420 in response to the control signals
440 and 444 if the sensor output signal exceeds the threshold value
set by the current source 430. The switching circuit 450 includes a
sense resistor RO and a switching circuit current mirror composed
of M5 and M6 configured to control switching of the switching
circuit. The sense resistor RO is coupled between the mirror
circuit 410 and the mirror circuit 420 and provides switching
control of the switching circuit current mirror M5 and M6 in
response to the control signals 440 and 444 from the threshold
detector mirror circuit 434.
[0023] As shown, the mirror circuit 410 includes transistor switch
devices M7 and M8 whereas the mirror circuit 420 includes
transistor switch devices M9 and M10. The pair of the transistor
switch devices in each mirror circuit 410 and 420 includes a length
parameter that defines a current capability of the transistor
switch devices. One of the pair of transistor switch devices for
the mirror circuit 410 is configured with a length parameter that
is greater than the length parameter of the transistor switch
devices for the mirror circuit 420. An amplifier 460 receives a
reference voltage 464 and is provided to set a bias current for the
sensor 404.
[0024] FIG. 5 illustrates an example signal diagram 400 that
illustrates the current output from the mirror circuits of FIG. 4.
Combined current output in micro amperes from the respective mirror
circuits is shown on the vertical axis and time in milliseconds is
shown on the horizontal axis. As shown, at current levels below 11
micro amperes, signal output 510 is generated to the detection
circuit by the first mirror circuit. After about 12 milliseconds
the input signal current exceeds a threshold, the signal 510 goes
into saturation yet the signal output is now provided by the second
current mirror at 520. The combined signal current provided to the
detection circuit from the mirror circuits is shown at 530. As
shown, switching between the current mirror outputs is
substantially seamless and smooth which is facilitated by the
threshold and switching circuits described herein.
[0025] In view of the foregoing structural and functional features
described above, an example method will be better appreciated with
reference to FIG. 6. While, for purposes of simplicity of
explanation, the method is shown and described as executing
serially, it is to be understood and appreciated that the method is
not limited by the illustrated order, as parts of the method could
occur in different orders and/or concurrently from that shown and
described herein. Such method can be executed by various hardware
circuits and components configured to execute machine readable
instructions stored in memory and executable by an integrated
circuit or a processor, for example.
[0026] FIG. 6 illustrates an example method for detecting input
signals. At 6100, the method 600 includes providing a sensor output
signal in response to a received input signal. At 620, the method
600 includes generating separate mirror circuit output signals from
separate mirror circuits in response to signal variances of the
sensor output signal. Each of the separate mirror circuit output
signals are generated in response to different signal levels of the
sensor output signal. At 630, the method 600 includes generating a
signal strength indication for the input signal based on monitoring
of the separate mirror circuit output signals. Although not shown,
the method can also include generating the separate mirror circuit
output signals if the sensor output signal exceeds a threshold
value.
[0027] What have been described above are examples. It is, of
course, not possible to describe every conceivable combination of
components or methodologies, but one of ordinary skill in the art
will recognize that many further combinations and permutations are
possible. Accordingly, the disclosure is intended to embrace all
such alterations, modifications, and variations that fall within
the scope of this application, including the appended claims. As
used herein, the term "includes" means includes but not limited to,
the term "including" means including but not limited to. The term
"based on" means based at least in part on. Additionally, where the
disclosure or claims recite "a," "an," "a first," or "another"
element, or the equivalent thereof, it should be interpreted to
include one or more than one such element, neither requiring nor
excluding two or more such elements.
* * * * *