U.S. patent application number 10/910414 was filed with the patent office on 2006-02-09 for millimeter wave switch.
Invention is credited to Lon A. Dearden, Adam E. Robertson.
Application Number | 20060028293 10/910414 |
Document ID | / |
Family ID | 35756845 |
Filed Date | 2006-02-09 |
United States Patent
Application |
20060028293 |
Kind Code |
A1 |
Robertson; Adam E. ; et
al. |
February 9, 2006 |
MILLIMETER WAVE SWITCH
Abstract
A switch selectively provides one of a first input signal at a
first frequency and a second input signal at a second frequency to
an output terminal with low insertion loss and high isolation
between the first and second input signals. The first input signal
is received at a first input terminal and the second input signal
is received at a second input terminal. A switching element
electrically connects the first input terminal and the output
terminal to provide the first input signal to the output terminal
in a first state and isolates the first input terminal from the
output terminal in a second state. A bias line is electrically
connected to provide a control signal to the switching element to
select between the first state and the second state. An AC coupled
transmission line is electrically connected to the second input
terminal and electrically connected between the switching element
and the output terminal. The control signal is provided through the
AC coupled transmission line when the switching element is in the
first state to isolate the second input terminal from the output
terminal and provide the first input signal to the output terminal.
The second input signal is provided DC coupled to the output
terminal through the AC coupled transmission line when the
switching element is in the second state.
Inventors: |
Robertson; Adam E.; (Santa
Rosa, CA) ; Dearden; Lon A.; (Santa Rosa,
CA) |
Correspondence
Address: |
AGILENT TECHNOLOGIES, INC.;Legal Department, DL 429
Intellectual Property Administration
P.O. Box 7599
Loveland
CO
80537-0599
US
|
Family ID: |
35756845 |
Appl. No.: |
10/910414 |
Filed: |
August 3, 2004 |
Current U.S.
Class: |
333/104 ;
333/262 |
Current CPC
Class: |
H01P 1/15 20130101; H03K
17/76 20130101 |
Class at
Publication: |
333/104 ;
333/262 |
International
Class: |
H01P 1/15 20060101
H01P001/15 |
Claims
1. A switch for selectively providing an input signal to an output
terminal, comprising: a first input terminal receiving a first
input signal at a first frequency; a second input terminal
receiving a second input signal at a second frequency; a switching
element coupling said first input terminal and said output terminal
to provide said first input signal to said output terminal in a
first state and isolating said first input terminal from said
output terminal in a second state; a bias line providing a control
signal to said switching element to select between said first state
and said second state; and an AC coupled transmission line coupled
to said second input terminal and coupled between said switching
element and said output terminal, said control signal being
provided through said AC coupled transmission line when said
switching element is in said first state to isolate said second
input terminal from said output terminal and provide said first
input signal to said output terminal, said second input signal
being provided DC coupled to said output terminal through said AC
coupled transmission line when said switching element is in said
second state.
2. The switch of claim 1, wherein said switching element is a
series switching element.
3. The switch of claim 2, further comprising: a shunt switching
element couple to said AC coupled transmission line, said control
signal being provided to said shunt switching element through said
AC coupled transmission line when said series switching element is
in said first state, said control signal biasing said shunt
switching element to isolate said second input terminal from said
output terminal and provide said first input signal to said output
terminal through said AC coupled transmission line.
4. The switch of claim 3, wherein said shunt switching element and
said AC coupled transmission line are separated by a distance less
than or equal to 70 .mu.m.
5. The switch of claim 3, wherein said AC coupled transmission line
is formed above a thin film attached to a ground plane and said
shunt diode is formed adjacent said AC coupled transmission line
and above said ground plane in an area having said thin film
removed.
6. The switch of claim 3, wherein said AC coupled transmission line
is formed above a semiconductor substrate and said shunt switching
element is formed adjacent said AC coupled transmission line in
said semiconductor substrate.
7. The switch of claim 3, wherein said shunt switching element
comprises a first shunt switching element coupled to a first
portion of said AC coupled transmission line coupled between said
series switching element and ground through said first shunt
switching element and a second shunt switching element coupled to a
second portion of said AC coupled transmission line coupled between
said output terminal and said second input terminal.
8. The switch of claim 7, wherein said series switching element,
said first shunt switching element and said second shunt switching
element are PIN diodes.
9. The switch of claim 7, wherein said series switching element,
said first shunt switching element and said second shunt switching
element are transistors.
10. The switch of claim 1, further comprising: a capacitive element
coupled between said first input terminal and said switching
element.
11. The switch of claim 10, wherein said capacitive element is a DC
blocking capacitor.
12. The switch of claim 1, wherein said AC coupled transmission
line is a capacitive element comprising a first plate and a second
plate separated by a dielectric.
13. The switch of claim 12, wherein said first plate is comprised
of a first metal layer and said second plate is comprised of a
second metal layer.
14. The switch of claim 1, wherein said AC coupled transmission
line is a quarter wavelength transmission line.
15. The switch of claim 1, wherein said bias line is a quarter
wavelength bias line.
16. The switch of claim 1, further comprising a filter coupled
between said second input terminal and said AC coupled transmission
line.
17. A method for providing an input signal to an output terminal of
a switch comprising a switching element and an AC coupled
transmission line, said method comprising: receiving a first input
signal at a first input terminal, said first input signal being at
a first frequency; receiving a second input signal at a second
input terminal, said second input signal being at a second
frequency; providing said first input signal to said output
terminal by biasing said switching element with a control signal,
said control signal being provided through said switching element
and said AC coupled transmission line to isolate said second input
terminal from said output terminal; and providing said second input
signal through said AC coupled transmission line to said output
terminal when said control signal is not provided to said switching
element.
18. The method of claim 17, wherein said providing said first input
signal to said output terminal further comprises: biasing said
switching element with said control signal to couple said first
input terminal with said output terminal; and biasing a shunt
switching element through said AC coupled transmission line to
isolate said second input terminal from said output terminal.
19. The method of claim 18, wherein said providing said first input
terminal to said output terminal further comprises: using a quarter
wavelength transmission line as said AC coupled transmission line
to make said shunt switching element appear as an open circuit to
said first input signal and a short circuit to said second input
signal.
20. A switching method, comprising: providing a first input
terminal for receiving a first signal at a first frequency;
providing a second input terminal for receiving a second signal at
a second frequency; providing an output terminal for selectively
transmitting said first signal and said second signal; providing a
series switching element coupling said first input terminal and
said output terminal to provide said first input signal to said
output terminal in a first state and isolating said first input
terminal from said output terminal in a second state; providing an
AC coupled transmission line coupled to said second input terminal
and coupled between said series switching element and said output
terminal; providing a shunt switching element coupling said second
input terminal to said output terminal via said AC coupled
transmission line in said second state and isolating said second
input terminal from said output terminal in said first state; and
providing a bias line to provide a control signal to said series
switching element and said shunt switching element through said AC
coupled transmission line to select between said first state and
said second state.
21. The method of claim 20, wherein said providing said shunt
switching element further comprises: separating said shunt
switching element and said AC coupled transmission line by a
distance less than or equal to 70 .mu.m.
22. The method of claim 20, wherein said providing said AC coupled
transmission line includes forming said AC coupled transmission
line above a thin film attached to a ground plane, and wherein said
providing said shunt switching element includes forming said shunt
switching element adjacent said AC coupled transmission line and
above said ground plane in an area having said thin film
removed.
23. The method of claim 20, wherein said providing said AC coupled
transmission line includes forming said AC coupled transmission
line above a semiconductor substrate, and wherein said providing
said shunt switching element includes forming said shunt diode
adjacent said AC coupled transmission line in said semiconductor
substrate.
24. The method of claim 20, wherein said providing said shunt
switching element includes providing a first shunt switching
element coupled to a first portion of said AC coupled transmission
line coupled between said series switching element and ground
through said first shunt switching element and providing a second
shunt switching element coupled to a second portion of said AC
coupled transmission line coupled between said output terminal and
said second input terminal.
25. The method of claim 20, further comprising: providing a
DC-blocking capacitive element coupled between said first input
terminal and said switching element.
26. The method of claim 20, wherein said providing said AC coupled
transmission line includes providing a first plate and a second
plate separated by a dielectric.
27. The method of claim 26, wherein said providing said AC coupled
transmission line includes forming a first metal layer, forming a
dielectric above said first metal layer and forming a second metal
layer above said dielectric.
28. The method of claim 20, wherein said providing said AC coupled
transmission line includes providing a quarter wavelength
transmission line.
29. The method of claim 20, wherein said providing said bias line
includes providing a quarter wavelength bias line.
30. The method of claim 20, further comprising providing a filter
coupled between said second input terminal and said AC coupled
transmission line.
Description
BACKGROUND OF THE INVENTION
[0001] Switches have long been used in electrical circuit designs
to isolate a portion of an electrical circuit. In its simplest
form, a switch operates to allow a signal to pass from an input
terminal to an output terminal in a "closed" position and to
prevent the signal from passing from the input terminal to the
output terminal in an "open" position.
[0002] In the microwave and mm-wave frequency range, switches are
used in instrumentation, communications, radar, fiber optic and
many other systems that require high-frequency switching. For
example, a switch can be used for pulse modulation, port isolation,
transfer switching, high-speed switching, replacement of mechanical
parts and other switch applications.
[0003] There a number of commercially available high-frequency
switches on the market today. However, these switches have all
failed to simultaneously obtain high switch isolation greater than
15 dBm, high power handling above 24 dBm and low insertion loss of
a fraction of a dB from DC to mm-wave frequencies. For example,
high-frequency switches employing field-effect transistors (FETs)
typically are unable to handle high frequencies in the mm-wave
range and/or high power above 24 dBm. In the alternative, FET-based
solutions may have high insertion loss. In addition,
waveguide-based switches are difficult to integrate and lack the
required bandwidth coverage to DC. Furthermore, coupling-based
diplexers typically have poor isolation and high insertion loss at
the cross-over frequency.
[0004] Therefore, what is needed is a switch capable of achieving
high switch isolation, high power handling and low insertion loss
from DC to mm-wave frequencies.
SUMMARY OF THE INVENTION
[0005] Embodiments of the present invention provide a switch for
selectively providing one of a first input signal at a first
frequency and a second input signal at a second frequency to an
output terminal. The first input signal is received at a first
input terminal and the second input signal is received at a second
input terminal. A switching element electrically connects the first
input terminal and the output terminal to provide the first input
signal to the output terminal in a first state and isolates the
first input terminal from the output terminal in a second state. A
bias line is electrically connected to provide a control signal to
the switching element to select between the first state and the
second state. An AC coupled transmission line is electrically
connected to the second input terminal and electrically connected
between the switching element and the output terminal. The control
signal is provided through the AC coupled transmission line when
the switching element is in the first state to isolate the second
input terminal from the output terminal and provide the first input
signal to the output terminal. The second input signal is provided
DC coupled to the output terminal through the AC coupled
transmission line when the switching element is in the second
state.
[0006] In one embodiment, the switching element is a series
switching element and a shunt switching element is connected to the
AC coupled transmission line. The control signal is provided to the
shunt switching element through the AC coupled transmission line
when the series switching element is in the first state to isolate
the second input terminal from the output terminal and provide the
first input signal to the output terminal through the AC coupled
transmission line. The shunt switching element is separated from
the AC coupled transmission line by a distance less than or equal
to 70 .mu.m. However, it should be understood that in other
embodiments, the separation distance is designed to maintain
sufficient isolation. In a further embodiment, the shunt switching
element includes two shunt switching elements. A first shunt
switching element is connected to a first portion of the AC coupled
transmission line connected between the series switching element
and ground through the first shunt switching element and a second
shunt switching element is connected to a second portion of the AC
coupled transmission line connected between the output terminal and
the second input terminal.
[0007] In another embodiment, the AC coupled transmission line is a
capacitive element having a first plate and a second plate
separated by a dielectric. The first plate is formed of a first
metal layer and the second metal plate is formed of a second metal
layer. In a further embodiment, the AC coupled transmission line is
a quarter wavelength transmission line to make the shunt switching
element appear as an open circuit to the first input signal and a
short circuit to the second input signal. In still a further
embodiment, the first input signal is at a first frequency greater
than or equal to 20 GHz and the second input signal is at a second
frequency between DC and 20 GHz.
[0008] Advantageously, embodiments of the present invention uses a
simplistic biasing scheme by using a single bias line for all
switching elements and biasing the shunt switching elements through
the second metal layer of the AC coupled transmission line. In
addition, the power handling of the switch is improved to at least
33 dBm when using PIN diodes. Moreover, low insertion loss and high
isolation is achieved by placing the shunt switching elements as
close as possible to the AC coupled transmission line. Likewise,
improved isolation is achieved by using two shunt switching
elements on either side of the AC coupled transmission line.
Furthermore, the invention provides embodiments with other features
and advantages in addition to or in lieu of those discussed above.
Many of these features and advantages are apparent from the
description below with reference to the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The disclosed invention will be described with reference to
the accompanying drawings, which show exemplary embodiments of the
invention and which are incorporated in the specification hereof by
reference, wherein:
[0010] FIG. 1 is a block diagram of an exemplary DC to mm-wave
frequency switch, in accordance with embodiments of the present
invention;
[0011] FIG. 2 is a schematic diagram of an exemplary DC to mm-wave
frequency switch, in accordance with embodiments of the present
invention;
[0012] FIG. 3A is a schematic diagram of a circuit model for the
switch in a forward bias condition;
[0013] FIG. 3B is a schematic diagram of a circuit model for the
switch in a zero bias or reverse bias condition;
[0014] FIG. 4 is a circuit layout of the switch, in accordance with
embodiments of the present invention;
[0015] FIG. 5 is a cross-sectional view of the switch of FIG. 4, in
accordance with one embodiment of the present invention;
[0016] FIG. 6 is a cross-sectional view of the switch fabricated
using an integrated circuit design;
[0017] FIG. 7 is a flow chart illustrating an exemplary process for
fabricating the switch, in accordance with embodiments of the
present invention; and
[0018] FIG. 8 is a flow chart illustrating an exemplary process for
operating the switch, in accordance with embodiments of the present
invention.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0019] FIG. 1 is a block diagram of an exemplary DC to mm-wave
frequency switch 100, in accordance with embodiments of the present
invention. The switch 100 is a part of a switching system 10. For
example, in one embodiment, switching system 10 can be an output
switch of a 44 GHz up-converter. System 10 includes two signal
sources 20 and 30. A first signal source 20 supplies a first signal
at a first frequency to a first input terminal 110 of switch 100. A
second signal source 30 supplies a second signal at a second
frequency to a second input terminal 120 of switch 100. Switch 100
selectively provides the first signal or the second signal to an
output terminal 130 of switch 100. In one embodiment, the first
frequency is a high frequency greater than or equal 20 GHz and the
second frequency is a low frequency between DC and 20 GHz. However,
it should be understood that in other embodiments, the first and
second frequencies can be any two frequencies from which switch 100
selects.
[0020] FIG. 2 is a schematic diagram of an exemplary DC to mm-wave
frequency switch 100, in accordance with embodiments of the present
invention. Switch 100 includes input terminals 110 and 120 and
output terminal 130. A series switching element 240 is connected to
first input terminal 110. Series switching element 240 is shown as
a single PIN diode. However, it should be understood that in other
embodiments, additional PIN diodes can be added to form series
switching element 240. In addition, it should be understood that
other circuit elements can be used as series switching element 240.
For example, series switching element 240 can include one or more
P-N diodes, Schottky diodes, field-effect transistors (FETs), PNP
transistors, NPN transistors or any other type of circuit
element.
[0021] In FIG. 2, the anode of diode 240 is electrically connected
to first input terminal 110 via a capacitor 220. The anode of diode
240 is further connected to a bias line 230. Bias line 230 is
connected to the end of bias choke 232, which in turn is connected
to a bias controller (Vc) 236 that provides a control signal to
bias diode 240. In one embodiment, bias line 230 includes a quarter
wavelength transmission line segment. Capacitors 220 and 234 serve
to block DC potentials that are applied via bias line 230 to bias
diode 240 into its conducting or non-conducting states in a manner
well-known in the art. Capacitor 234 further provides an AC short
circuit to ground at radio frequencies.
[0022] The cathode of diode 240 is electrically connected to output
terminal 130 via an AC coupled transmission line 250. AC coupled
transmission line 250 is a capacitive element formed of two
capacitive plates 255 and 258, each having a length of a quarter
wavelength. Plate 255 is connected between series switching element
(series diode) 240 and two shunt switching elements (shunt diodes)
260 and 270. It should be understood that as discussed above in
connection with series switching element 240, other circuit
elements can be used as shunt switching elements 260 and 270. In
addition, in other embodiments, a single shunt diode 260 or 270 can
be used instead of two shunt diodes 260 and 270. Plate 258 is
connected between second input terminal 120 and output terminal
130. In one embodiment, as described in more detail below in
connection with FIGS. 5 and 6, AC coupled transmission line 250 is
formed of two metal layers (capacitive plates 255 and 258)
separated by a dielectric to prevent DC frequencies from passing
between capacitive plates 255 and 258, while allowing high
frequencies (e.g., radio and microwave frequencies) to pass
therebetween.
[0023] When bias controller 236 provides a positive bias potential,
capacitors 220 and 234 block direct current, which enables a
forward bias voltage to be applied to series diode 240 and shunt
diodes 260 and 270 through AC coupled transmission line 250. As a
result of the forward bias voltage, series diode 240 and shunt
diodes 260 and 270 switch to a conducting or "ON" state. Therefore,
a signal entering from first input terminal 110 passes through
capacitor 220, diode 240 and AC coupled transmission line 250 to
output terminal 130.
[0024] When bias controller 236 provides a negative bias potential
or zero bias potential, a reverse bias voltage or zero voltage is
applied to series diode 240, which in turn causes zero voltage to
be applied to shunt diodes 260 and 270. As a result of the reverse
bias voltage and/or zero voltage, series diode 240 and shunt diodes
260 and 270 switch to a non-conducting or "OFF" state. Therefore, a
signal entering from second input terminal 120 passes through AC
coupled transmission line 250 to output terminal 130.
[0025] The operation of switch 100 is explained in more detail with
reference to FIGS. 3A and 3B. FIG. 3A is a schematic diagram of a
circuit model for switch 100 in a forward bias condition. In the
forward bias condition, the circuit equivalent of series diode 240
is a transmission line 300 and the circuit equivalent of shunt
diodes 260 and 270 are grounds 310 and 320. A first input signal
entering switch 100 from first input terminal 110 travels through
capacitor 220 and series diode 240 (transmission line 300) to AC
coupled transmission line 250. Thereafter, the first input signal
travels through AC coupled transmission line 250 to output terminal
130.
[0026] At high frequencies (e.g., radio and microwave frequencies),
with a quarter wavelength length for the AC coupled transmission
line 250, shunt switching elements 260 and 270 appear as open
circuits (not specifically illustrated) to the first input signal
and short circuits to grounds 310 and 320 to a second input signal
entering switch 100 from second input terminal 120. Thus, at high
frequencies, any portion of the first input signal traveling down
either plate 255 or 258 of AC coupled transmission line 250 will be
reflected back up AC coupled transmission line 250 to output
terminal 130, and the second signal will be provided to grounds 310
and 320. Thus, when shunt diodes 260 and 270 are forward biased,
second input terminal 120 is isolated from output terminal 130 at
high frequencies to prevent the second input signal from traveling
up the second plate 258 of AC coupled transmission line 250 to
output terminal 130. However, at DC, there is no isolation between
second input terminal 120 and output terminal 130.
[0027] FIG. 3B is a schematic diagram of a circuit model for switch
100 in a zero bias or reverse bias condition. In the reverse bias
or zero bias condition, the circuits equivalent of series diode 240
and shunt diodes 260 and 270 are open circuits 330, 340 and 350,
respectively. A first input signal entering switch 100 from first
input terminal 110 travels through capacitor 220 and is blocked by
open circuit 330 created by series diode 240. Thus, when series
diode 240 is reverse-biased or zero-biased, first input terminal
110 is isolated from output terminal 130 to prevent the first input
signal from reaching output terminal 130.
[0028] A second input signal entering switch 100 from second input
terminal 120 travels up second plate 258 of AC coupled switching
element 250 to output terminal 130. Since series switching element
240 and shunt switching elements 260 and 270 appear as open
circuits 330, 340 and 350, respectively, to the second input
signal, at high frequencies, any portion of the second input signal
passing from second plate 258 to first plate 255 of AC coupled
transmission line 250 will be reflected back to second plate 258 of
AC coupled transmission line 250 to output terminal 130. It should
be understood that at DC, the second input signal travels through
second plate 258 of AC coupled transmission line 250 to output
terminal 130 as DC frequencies are not able to pass from second
plate 258 to first plate 255.
[0029] FIG. 4 is a thin film circuit layout 400 of switch 100, in
accordance with embodiments of the present invention. A first input
signal entering switch 100 at first input terminal 110 travels
through capacitor 220 and microstrip conductors, shown generally at
405, to series diode 240. When series diode 240 is forward biased,
the first input signal travels through AC coupled transmission line
250 and microstrip conductors, shown generally at 425, to output
terminal 130. A second input signal entering switch 100 at second
input terminal 120 travels through microstrip conductors, shown
generally at 415, and low pass filter 460 to AC coupled
transmission line 250. Low pass filter 460 is a filter that passes
20 GHz and provides greater isolation. When shunt diodes 260 and
270 are forward biased, at high frequencies, the second input
signal is prevented from traveling through AC coupled transmission
line 250. When shunt diodes 260 and 270 are reverse biased or zero
biased, the second input signal travels through AC coupled
transmission line 250 and microstrip conductors 425 to output
terminal 130.
[0030] Diodes 260 and 270 are formed in thin film cutouts 410 and
420, respectively, where the thin film is removed. In one
embodiment, to make diodes 260 and 270 quasi-planar with the
surface of the thin film, diodes 260 and 270 are placed above shims
430 and 440, respectively. Thin film cutouts 410 and 420 can be
formed, for example, using a laser. However, lasers have a finite
width, and as a result, can damage the surface of other materials,
such as AC coupled transmission line 250. Therefore, each cutout
410 and 420 is separated from AC coupled transmission line 250 by a
minimum distance 450. In one embodiment distance 450 is
approximately 70 .mu.m. However, in other embodiments, distance 450
can be less than 70 .mu.m. Since the insertion loss and isolation
of switch 100 are proportional to distance 450, it is desirable to
have distance 450 as small as possible.
[0031] FIG. 5 is a cross-sectional view of the switch of FIG. 4, in
accordance with one embodiment of the present invention. FIG. 5
illustrates a die-attach assembly technique for switch 100. A
conductive adhesive 510, such as epoxy or solder, is formed above
an electrically conductive surface 500. The electrically conductive
surface 500 forms a DC and RF ground plane for switch 100. For
example, in one embodiment, surface 500 is formed of copper or
other conductive metal. A thin film 520 is formed above conductive
adhesive 510, and cutouts 410 and 420 are made in thin film 520
where diodes 260 and 270 are attached. Metal shims 430 and 440 are
placed above conductive adhesive 510 in cutouts 410 and 420,
respectively, and diodes 260 and 270 are attached to metal shims
430 and 440, respectively.
[0032] A first metal layer 530 made of a metallic material is
formed above or attached to thin film 520 between diodes 260 and
270. First metal layer 530 forms second plate 258 (shown in FIG. 2)
of AC coupled transmission line 250. A dielectric layer 540 made of
a dielectric material is formed above first metal layer 530, and a
second metal layer 550 is formed above dielectric layer 540. Second
metal layer 550 forms first plate 255 (shown in FIG. 2) of AC
coupled transmission line 250. Second metal layer 550 is further
formed between AC coupled transmission line 250 and diodes 260 and
270 to connect diodes 260 and 270 to first plate 255 of AC coupled
transmission line 250. Dielectric layer 540 serves to prevent DC
frequencies from passing from first metal layer 530 to second metal
layer 550.
[0033] FIG. 6 is a cross-sectional view of switch 100 fabricating
using a semiconductor substrate 600. Diodes 260 and 270 are formed
in semiconductor substrate 600, as is well-known in the art. A
first metal layer 610 made of a metallic material is formed above
substrate 600 between diodes 260 and 270. First metal layer 610
forms second plate 258 (shown in FIG. 2) of AC coupled transmission
line 250. A dielectric layer 620 made of a dielectric material is
formed above first metal layer 610, and a second metal layer 630 is
formed above dielectric layer 620. Second metal layer 630 forms
first plate 255 (shown in FIG. 2) of AC coupled transmission line
250. Second metal layer 630 is further formed between AC coupled
transmission line 250 and diodes 260 and 270 to connect diodes 260
and 270 to first plate 255 of AC coupled transmission line 250.
Dielectric layer 620 prevents DC frequencies from passing from
first metal layer 610 to second metal layer 630.
[0034] FIG. 7 is a flow chart illustrating an exemplary process 700
for fabricating the switch, in accordance with embodiments of the
present invention. The process begins at step 705. At step 710, a
first input terminal is provided for receiving a first input signal
at a first frequency. For example, in one embodiment, the first
frequency is a high frequency greater than or equal to 20 GHz. At
step 715, a second input terminal is provided for receiving a
second input signal at a second frequency. For example, in one
embodiment, the second frequency is a low frequency between DC and
20 GHz. At step 720, an output terminal is provided for selectively
transmitting the high or low frequencies.
[0035] At step 725, a series switching element is provided to
electrically connect the first input terminal with the output
terminal to provide the first input signal to the output terminal
in a first state and isolate the first input terminal from the
output terminal in a second state. At step 730, an AC coupled
transmission line is electrically connected to the second input
terminal and electrically connected between the series switching
element and the output terminal.
[0036] At step 735, a shunt switching element is provided to
electrically connect the second input terminal to the output
terminal via the AC coupled transmission line in the second state
and isolate the second input terminal from the output terminal in
the first state. At step 740, a bias line is electrically connected
to provide a control signal to the series switching element and the
shunt switching element through the AC coupled transmission line to
select between the first state and the second state. The process
ends at step 745.
[0037] FIG. 8 is a flow chart illustrating an exemplary process 800
for operating the switch, in accordance with embodiments of the
present invention. The process begins at step 810. At step 820, a
first input signal at a first frequency is received at a first
input terminal. At step 830, a second input signal at a second
frequency is received at a second input terminal. If the switching
element(s) are forward biased at step 840, the first input signal
is provided to the output terminal at step 850, and the second
input terminal is isolated from the output terminal at step 860.
However, if the switching element(s) are reverse biased or zero
biased at step 840, the second input signal is provided to the
output terminal at step 870, and the first input terminal is
isolated from the output terminal at step 880. The process ends at
step 890.
[0038] As will be recognized by those skilled in the art, the
innovative concepts described in the present application can be
modified and varied over a wide rage of applications. Accordingly,
the scope of patents subject matter should not be limited to any of
the specific exemplary teachings discussed, but is instead defined
by the following claims.
* * * * *