Waveguide switch having four ports and three connecting states

A four-port waveguide switch is described which allows any two pairs of ports to be connected together. A separate waveguide independently connects each port with each of the remaining ports. In each of the six separate waveguides there is provided at least one resonant cavity having a passband that includes the frequencies of the incident microwave signals to be switched. A disrupting structure is provided for each resonant cavity. Each disrupting structure may be switched between a first state wherein the respective cavity is not detuned and a second state wherein the respective cavity is detuned such that it reflects the incident microwave signals. By switching the appropriate disrupting structures to their second state, any of the three possible connecting states of a four port switch of the present invention can be obtained.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to waveguide switches and 
particularly to a waveguide switch having four ports and three connecting 
states. 
2. Description of the Prior Art 
In order to improve the reliability of communication systems, it has been 
the practice to provide redundant elements in the system which are 
switched in to replace system elements which have failed. For example, it 
is common to provide in a communication system standby units, such as 
receivers and transmitters, which are appropriately switched to replace 
main units that have failed. 
The switching apparatus needed in such redundancy systems proved easy to 
provide when systems operated at low frequencies or at low transmitter 
power levels. But with the move to higher frequencies and power levels, 
existing switching apparatus has proved to be inadequate. The deficiency 
is particularly acute in the communication satellite area where the high 
cost of an orbited satellite requires the maximum possible switchable 
combinations of system elements, but also requires a very light and small 
switch. 
As disclosed in pending application Ser. No. 670,290, filed Mar. 25, 1976 
to Assal et al, now U.S. Pat. No. 4,070,637, the switch needed for higher 
order satellite system redundancy configurations is one having four ports 
and three connecting states, referred to as a R switch, as shown in FIG. 
1. The R switch must provide minimal attenuation in the conducting paths 
and maximum isolation in the non-conducting paths. 
Since satellite communication systems operate at very high frequencies, the 
R switch must be able to operate efficiently at these frequencies. As is 
well known in the microwave art, waveguide switches have the best 
electrical characteristics at these high frequencies. However, the known 
waveguide switch which provides the three connecting states is not 
suitable in satellite communication systems because of several 
deficiencies including excessive size, weight and cost. 
A known non-waveguide switch which provides the three connecting states of 
the present invention is the microwave matrix switch of Lee Laboratories, 
Lexington, Massachusetts. This microwave matrix switch uses connectors 
instead of waveguide ports and, therefore, is unsuitable for satellite 
communication systems where low loss and high power capability are 
required. 
A known waveguide switch called a B switch, as illustrated in FIG. 2, can 
provide only the first and second connecting states shown in FIG. 1. One 
such B switch is available from Sivers Labs in Stockholm, Sweden and is 
designated PM 7306J. As shown in FIG. 2, the B switch can provide the 
first connecting state with port 1 connected to port 2 and port 3 
connected to port 4. The B switch can also provide the second connecting 
state with port 1 connected to port 3, and port 2 connected to port 4. The 
B switch cannot provide the third connecting state, since port 1 cannot be 
connected to port 4 simultaneously with port 2 being connected to port 3. 
A known waveguide switch called the modified B switch provides the three 
connecting states of the present invention. As is apparent below, however, 
the modified B switch has several major deficiencies with respect to 
satellite communication systems including excessive size, weight, and 
cost. 
A modified B switch, as shown in FIGS. 3 and 4, includes an unmodified B 
switch which is now described. The B switch is housed in a square 
structure designated generally by reference numeral 30. Ports 20, 22, 24 
and 26 are provided in successive 90.degree. intervals around structure 
30. For purposes of description and with reference to FIG. 2, port 20 
corresponds to port 1, port 22 corresponds to port 2, port 24 corresponds 
to port 4, and port 26 corresponds to port 3. A structure 28, mounted for 
rotation on a drive shaft 10, is provided in structure 30. A waveguide 12 
is mounted to structure 28 and has a length such that it can electrically 
couple port 22 to port 26, or port 20 to port 24 depending on the angle of 
rotation of shaft 10. A curved waveguide 16 is mounted to structure 28 and 
has a curve and length such that it can electrically couple port 20 to 
port 22, port 22 to port 24, port 24 to port 26, or port 26 to port 20 
depending on the angle of rotation of shaft 10. Similarly, a curved 
waveguide 14 is mounted to structure 28 and has a curve and length such 
that it can electrically couple port 24 to port 26, port 26 to port 20, 
port 20 to port 22, or port 22 to port 24 depending on the angle of 
rotation of shaft 10. Obviously, with this unmodified B switch, it is 
impossible to provide the third connecting state of the present invention, 
since port 20 cannot be connected to port 24 simultaneously with the 
connection of port 22 to port 26. 
In order to provide the third connecting state of the present invention, 
the B switch can be modified in the following fashion. Specifically, a 
waveguide 18 having four 90.degree. bends can be mounted to structure 28 
perpendicular to and below waveguide 12; waveguide 18 has a length such 
that it can electrically couple port 20 to port 24, or port 22 to port 26 
depending on the angle of rotation of shaft 10. 
While the modified B switch provides the three connecting states, it has 
several major deficiencies. First, in order to provide waveguide 18, the 
height of structure 30 has to be at least doubled, and the length and 
width of structure 30 has to be increased to accommodate the four required 
90.degree. bends in waveguide 18. In a satellite, size is extremely 
critical. Second, the addition of waveguide 18 requires a larger diameter 
shaft 10 and a larger source to drive shaft 10. In a satellite, weight is 
extremely critical. Third, both a modified and an unmodified B switch 
require close tolerance components due to rotation required to perform the 
switching function, and these critical dimensions resulted in added 
manufacturing costs. 
Furthermore, there are several known waveguide switches that do not provide 
the three connecting states of the present invention. Specifically, a 
waveguide switch is disclosed in U.S. Pat. No. 2,164,792 which provides 
only a single-pole single-throw connecting state. A waveguide switch is 
disclosed in U.S. Pat. No. 3,546,633 which also provides only a 
single-pole single-throw connecting state. A waveguide switch is disclosed 
in U.S. Pat. No. 3,953,853 which provides only a single-pole double-throw 
connecting state. Finally, a waveguide switch is disclosed in U.S. Pat. 
No. 3,768,041 which also provides only a single-pole double-throw 
connecting state. 
SUMMARY OF THE INVENTION 
Therefore, it is an object of the present invention to provide a waveguide 
switch having four ports and three connecting states. 
It is an additional object of the present invention to provide a waveguide 
switch that is small in size, light in weight and economical to 
manufacture. 
It is a further object of the present invention to provide a waveguide 
switch not requiring the rotation of a shaft to achieve the switching 
function. 
Other objects and advantages of the invention will become apparent in the 
following description. 
According to the present invention, there is provided between each pair of 
ports a connecting waveguide. Since there are four ports in the present 
invention, six connecting waveguides are provided. The connecting 
waveguides are dimensioned to allow propagation of the incident 
electromagnetic energy with minimal attenuation. Each connecting waveguide 
is provided with at least one cavity, each cavity having a passband that 
includes the frequency of the incident electromagnetic energy. When one 
cavity is provided in a connecting waveguide, a structure for disrupting 
the passband of the cavity is provided. The disrupting structure is 
switchable between two states. In the first state, the disrupting 
structure does not detune the cavity and thus the incident electromagnetic 
energy is allowed to propagate therethrough. In the second state, the 
disrupting structure detunes the cavity sufficiently such that the 
incident electromagnetic energy is prevented from propagating 
therethrough. When more than one cavity is provided in a connecting 
waveguide, a disrupting structure is provided for only two cavities, the 
two cavities being those most electrically adjacent to their respective 
port. The three connecting states between the four ports of the waveguide 
switch of the present invention are achieved by the appropriate switching 
of all of the disrupting structures. 
The features and advantages of the present invention are better understood 
from the following detailed description of preferred embodiments of the 
present invention when taken in conjunction with the accompanying drawings 
.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The three connecting states of the four-port waveguide switch of the 
present invention are functionally illustrated in FIG. 1. In the first 
connecting state, port 1 is connected to port 2, and port 3 is connected 
to port 4. In the second connecting state, port 1 is connected to port 3, 
and port 2 is connected to port 4. In the third connecting state, port 1 
is connected to port 4, and port 3 is connected to port 2. It is apparent 
in the following description that the switch of the present invention is 
symmetrical in each of the three connecting states; this allows the 
incident electromagnetic energy to be applied to either port of a 
connected pair of ports. 
The waveguide switch of the present invention, which is now described, 
overcomes all of the deficiencies of a B switch, modified or unmodified. 
The electrical analog of the waveguide switch of the present invention is 
shown in FIG. 5. A waveguide which electrically couples port 1 to port 3 
is designated generally by the reference numeral 40. A waveguide which 
electrically couples port 1 to port 2 is designated generally by the 
reference numeral 42. A waveguide which electrically couples port 2 to 
port 4 is designated generally by the reference numeral 44. A waveguide 
which electrically couples port 3 to port 4 is designated generally by the 
reference numeral 46. A waveguide which electrically couples port 2 to 
port 3 is designated generally by the reference numeral 48. A waveguide 
which electrically couples port 1 to port 4 is designated generally by the 
reference numeral 50. 
Each waveguide 40, 42, 44, 46, 48, and 50 may be of any shape or length as 
long as it can propagate the incident electromagnetic energy with minimal 
attenuation and can accommodate at least one resonant cavity, discussed 
below. As is well known to those in the microwave art, the best materials 
for construction of waveguide walls with respect to minimal attenuation 
are solid silver, silver-plated copper, and aluminum. 
Each waveguide 40, 42, 44, 46, 48, and 50 has at least one resonant cavity. 
Each resonant cavity is constructed such that its bandwidth is sufficient 
to pass the incident electromagnetic energy with minimal attenuation. 
Turning now to FIGS. 6, 7 and 8, the preferred embodiments of the switch of 
the present invention are shown. Like numerals refer to like elements. 
Each waveguide 40, 42, 44, 46, 48 and 50 is represented as being 
rectangular and having two resonant cavities, but this is done only for 
purposes of description and in no way is meant to limit the scope of the 
invention. 
Waveguide 40 is sidewall coupled to port 1 by an iris provided in a wall 
52, and is sidewall coupled to port 3 by an iris provided in a wall 56. A 
wall 54 having an iris is provided in waveguide 40 between walls 52, 56. 
The spacing of walls 52, 54, 56, and the size of the respective irises is 
such that each of the two resonant cavities formed thereby in waveguide 40 
has a bandwidth sufficient to pass the incident electromagnetic energy 
with minimal attenuation. It is obvious to those skilled in the microwave 
art that any sort of tuning device (not shown), for example, a tuning 
screw, may be provided for each of the above cavities or for the cavities 
described below in order to provide a means for fine tuning the center 
frequency of the respective cavity. 
Waveguide 42 is sidewall coupled to port 1 by means of an iris provided in 
a wall 74, and is sidewall coupled to port 2 by an iris provided in a wall 
70. A wall 72 having an iris is provided in waveguide 42 between walls 70, 
74. The spacing of walls 70, 72, 74, and the size of the respective irises 
is such that each of the two resonant cavities formed thereby in waveguide 
42 has a bandwidth sufficient to pass the incident electromagnetic energy 
with minimal attenuation. 
Waveguide 44 is sidewall coupled to port 3 by an iris provided in a wall 
58, and is sidewall coupled to port 4 by an iris provded in a wall 62. A 
wall 60 having an iris is provided in waveguide 44 between walls 58, 62. 
The spacing of walls 58, 60, 62 and the size of the respective irises is 
such that each of the two resonant cavities formed thereby in waveguide 44 
has a bandwidth sufficient to pass the incident electromagnetic energy 
with minimal attenuation. 
Waveguide 46 is sidewall coupled to port 4 by an iris provided in a wall 
64, and is sidewall coupled to port 2 by an iris provided in a wall 68. A 
wall 66 having an iris is provided in waveguide 46 between walls 64, 68. 
The spacing of walls 64, 66, 68 and the size of the respective irises in 
such that each of the two resonant cavities formed thereby in waveguide 46 
has a bandwidth sufficient to pass the incident electromagnetic energy 
with minimal attenuation. 
Waveguide 48 is broadwall coupled to port 2 by an iris provided in a wall 
84, and is broadwall coupled to port 3 by an iris provided in a wall 82. 
An end wall 92 and an end wall 94, together with a wall 90 define 
waveguide 48 in the section thereof that is disposed below waveguide 50. A 
wall 86 having an iris is provided between end walls 92, 94. The spacing 
of walls 82, 84, 86, 90, and endwalls 92, 94 and the size of the 
respective irises is such that each of the two resonant cavities formed 
thereby in waveguide 48 has a bandwidth sufficient to pass the incident 
electromagnetic energy with minimal attenuation. 
Waveguide 50 is coupled to port 1 by an iris provided in a wall 76, and is 
coupled to port 4 by an iris provided in a wall 80. A wall 78 having an 
iris is provided in waveguide 50 between walls 76, 80. The spacing of 
walls 76, 78, 80 and the size of the respective irises is such that each 
of the two resonant cavities formed thereby in waveguide 50 has a 
bandwidth sufficient to pass the incident electromagnetic energy with 
minimal attenuation. 
A disrupting structure is provided for each of the resonant cavities shown 
in FIGS. 6, 7 and 8, the purpose of which is described below. It should be 
noted that when more than two resonant cavities are provided in a 
waveguide connecting two ports, a disrupting structure is provided only 
for the two resonant cavities that are electrically adjacent to the 
respective ports. The purpose of the disrupting structure is to disrupt 
the passband of the resonant cavity such that the resonant cavity reflects 
the incident electromagnetic energy and thus prevent its passage 
therethrough. As is apparent to anyone skilled in the microwave art, when 
there are two resonant cavities connecting two ports, and each resonant 
cavity is provided with a disrupting structure, the amount the incident 
electromagnetic energy is attenuated is approximately equal to the sum of 
the dB attenuation caused by each detuned resonant cavity. 
A first embodiment of a disrupting structure, as illustrated in FIG. 9, has 
a plunger 91 that can be mechanically inserted into a resonant cavity to 
detune the cavity. Plunger 91 is preferably made of a metal, such as 
silver, silver-plated copper, or aluminum, but may be made of any material 
that conducts electricity. Plunger 91 is mounted for lateral movement in 
an insulating sleeve 106. Insulating sleeve 106 is disposed in the 
resonant cavity to be detuned. Insulating sleeve 106 is preferably made of 
Teflon, but may be made of any material that does not conduct electricity. 
Plunger 91 has a washer 95 mounted on the region of plunger 91 that is not 
inserted into insulating sleeve 106. Washer 95 is disposed between a first 
solenoid winding 100 and a second solenoid winding 104. First solenoid 
winding 100 has an insert 98, preferably made of iron, that is disposed 
around plunger 91. Second solenoid winding 104 has an insert 102, 
preferably made of iron, that is disposed around plunger 91. Plunger 91 is 
normally urged towards first solenoid winding 100 by a spring 93 wrapped 
around plunger 91 and disposed between second solenoid winding 104 and 
washer 95. Plunger 91 is normally urged towards second solenoid winding 
104 by a spring 96 wrapped around plunger 91 and disposed between first 
solenoid winding 100 and washer 95. Because of the urging of springs 93, 
96, washer 95 is normally disposed at the midpoint between first solenoid 
winding 100 and second solenoid winding 104. Thus, plunger 91 is normally 
inserted half-way into insulating sleeve 106 which is designated as the 
third position. 
The operation of plunger 91 is now described. When first solenoid winding 
100 is energized by a source of electric energy and second solenoid 
winding 104 is not energized, washer 95 is translated to the position 
adjacent insert 98, as shown in FIG. 9, which results in plunger 91 being 
outside the resonant cavity. This is designated the first position. When 
second solenoid winding 104 is energized by a source of electric energy 
and first solenoid winding 100 is not so energized, washer 95 is 
translated to the position adjacent insert 102, which results in plunger 
91 being inserted the maximum amount into insulating sleeve 106. This is 
designated the second position. In this second position, plunger 91 
detunes the resonant cavity such that the resonant cavity reflects the 
incident electromagnetic energy and, thus, does not let it propagate 
therethrough. Thus, when plunger 91 is in the first position, the 
waveguide cavity propagates the incident electromagnetic energy; when 
plunger 91 is in the second position, the waveguide cavity reflects the 
incident electromagnetic energy. 
A second embodiment of a disrupting structure, as illustrated in FIG. 10, 
has a two-state solid-state device 112, preferably a diode, disposed in a 
resonant cavity. A first lead of device 112 is electrically connected to a 
first metal post 110 which passes through the wall of the resonant cavity. 
First metal post 110 is electrically insulated from the wall of the 
resonant cavity by an insulating washer 118. A second lead of device 112 
is electrically connected to a second metal post 114 which passes through 
the wall of the resonant cavity. Second metal post 114 is electrically 
insulated from the wall of the resonant cavity by an insulating washer 
116. 
Device 112 is electrically switchable between two states. The first state, 
or OFF state, is when device 112 is reverse biased into the non-conduction 
state by an electric power supply (not shown) connected between leads 110, 
114. In the first state, device 112 does not detune the resonant cavity 
and the incident electromagnetic energy is allowed to propagate 
therethrough. The second state, or ON state, is when device 112 is forward 
biased into the conduction state by an electric power supply (not shown) 
connected between leads 110, 114. In the second state, device 112 detunes 
the resonant cavity and the incident electromagnetic energy is reflected. 
A third embodiment of a disrupting structure, as illustrated in FIG. 11, 
has a two-state gaseous discharge device disposed in a resonant cavity. A 
first lead of device 126 is electrically connected to a first metal post 
120 which passes through the wall of the resonant cavity. First metal post 
120 is electrically insulated from the wall of the resonant cavity by an 
insulating washer 124. A second lead of device 126 is electrically 
connected to a second metal post 128 which passes through the wall of the 
resonant cavity. Second metal post 128 is electrically insulated from the 
wall of the resonant cavity by an insulating washer 130. 
Device 126 is electrically switchable between two states. The first state, 
or OFF state, is when the gas of device 126 is not ionized by an electric 
power supply (not shown) connected between leads 120, 128. In the first 
state, device 126 does not detune the resonant cavity and the incident 
electromagnetic energy is allowed to propagate therethrough. The second 
state, or ON state, is when the gas of device 126 is ionized by an 
electric power supply (not shown) connected between leads 120, 128. In the 
second state, device 126 detunes the resonant cavity and the incident 
electromagnetic energy is reflected. 
The operation of the waveguide switch of the present invention is as 
follows. Referring to FIG. 12, connecting state 1 results when the 
disrupting structures associated with waveguides 40, 44, 48, 50 detune 
those waveguides. Connecting state 2 results when the disrupting 
structures associated with waveguides 42, 46, 48, 50 detune those 
waveguides. Connecting state 3 results when the disrupting structures 
associated with waveguides 40, 42, 44, 46 detune those waveguides. 
Although a number of specific embodiments of the disrupting structure have 
been described, it will be obvious to those having ordinary skill in the 
microwave art that the invention is not limited thereto since other such 
disrupting structures may be used without departing from the scope and 
spirit of the invention.