1. Field of the Invention
This invention relates to an ultralow-temperature low-noise amplification apparatus having a first-stage amplifier and a final-stage amplifier cooled to a very low temperature between an input connector and an output connector.
2. Description of the Related Art
The noise figure is an important factor for the evaluation of a highly sensitive amplification apparatus and is desirably as small as possible, and a HEMT (high electron mobility transistor) is, for example, used as a low-noise amplifying element for the microwave frequency range. Even if a low-noise amplifying element, such as a HEMT, may be used, however, its noise figure depends on the frequency range of the input signals to be amplified, and a problem in which no desired noise figure cannot be obtained would be raised, depending on their frequency range. On the other hand, it is known that an amplifying element generally has a smaller noise figure when used at a low temperature than at a high temperature. Therefore, there has already been proposed a cooled highly sensitive amplification apparatus in which an amplifying element is cooled to realize a noise figure suited for a highly sensitive amplification apparatus.
Although in the apparatus described above, it is only the amplifiers that are installed inside for signal processing, a highly sensitive amplification apparatus for processing high-frequency signals sometimes has a receive filter formed from a high-temperature superconductor. A high-temperature superconductor, such as an oxide superconductor, exhibits superconductivity at or below a critical temperature of about 70 K. If a receive filter formed from such a superconductor is combined with a low-temperature low-noise amplification apparatus and if all the necessary parts including the receive filter are kept at or below the critical temperature, it is possible to realize a great reduction of any loss caused by the receive filter, etc. and thereby a drastic improvement in the noise figure of the apparatus as a whole.
In the apparatus shown in
For the proper operation of the radio amplification apparatus 63 shown in
Under these circumstances, it is an object of this invention to provide an ultralow-temperature low-noise amplification apparatus of high sensitivity which realizes a small size, a light weight, a low electric power consumption and a low price.
According to one aspect of this invention, the above object is attained by an ultralow-temperature low-noise amplification apparatus having a first-stage amplifier and a final-stage amplifier which are cooled to a very low temperature between an input connector and an output connector, the apparatus further comprising an input connecting device connecting the input connector and the first-stage amplifier and so arranged as to reduce any insertion loss and an output connecting device connecting the final-stage amplifier and the output connector and so arranged as to reduce the conduction of heat.
According to another aspect of this invention, there is provided an ultralow-temperature low-noise amplification apparatus comprising a first signal transmitting device connecting an input connector and a receive filter, a second signal transmitting device connecting the receive filter and a first-stage amplifier, a third signal transmitting device connecting the first-stage amplifier and a final-stage amplifier, a fourth signal transmitting device connecting the final-stage amplifier and an output connector, a cooling holder for cooling the receive filter, second signal transmitting device, first-stage amplifier, third signal transmitting device and final-stage amplifier to a very low temperature and holding them at that temperature, and a heat-insulating container carrying the input and output connectors and a power supply connector on its outer wall and enclosing the second signal transmitting device, first-stage amplifier, third signal transmitting device, final-stage amplifier and cooling holder tightly in a vacuum state.
The first signal transmitting device is preferably of a material of low resistivity.
The receive filter, second and third signal transmitting devices, and final-stage amplifier preferably constitute a single module.
According to still another aspect of this invention, there is provided an ultralow-temperature low-noise amplification apparatus comprising a receive filter connected to an input connector, a first signal transmitting device connecting the receive filter and a first-stage amplifier, a second signal transmitting device connecting the first-stage amplifier and a final-stage amplifier, a third signal transmitting device connecting the final-stage amplifier and an output connector, a cooling holder for cooling the receive filter, first signal transmitting device, first-stage amplifier, second signal transmitting device and final-stage amplifier to a very low temperature and holding them at that temperature, and a heat-insulating container carrying the input and output connectors and a power supply connector on its outer wall and enclosing the receive filter, first signal transmitting device, first-stage amplifier, second signal transmitting device, final-stage amplifier and cooling holder tightly in a vacuum state.
The receive filter, first and second signal transmitting devices, and final-stage amplifier preferably constitute a single module.
The insertion loss caused by the first signal transmitting device positioned before the first-stage amplifier is the most responsible for any increase in the noise figure of the ultralow-temperature low-noise amplification apparatus as a whole. Therefore, the first signal transmitting device is formed from a material causing only a small insertion loss to reduce the noise figure of the whole apparatus effectively. The third signal transmitting device not substantially affecting the noise figure of the apparatus is formed from a material of low thermal conductivity, so that it may be possible to prevent any external heat from entering the heat-insulating container through the output connector, keep the interior of the heat-insulating container steadily at a low temperature and thereby maintain a low noise figure for the apparatus.
According to the present invention, the use of adequate materials for the first signal transmitting device on the input side of the apparatus and the third signal transmitting device on the output side as stated above makes it possible to provide an ultralow-temperature and low-noise amplification apparatus of high sensitivity which has an improved noise figure, does not call for any cooling device having a very high cooling capacity, but realizes a small size, a light weight, a low electric power consumption and a low price.
Description will now be made of several modes of embodying this invention with reference to the drawings.
Description will first be made of the principle on which the ultralow-temperature low-noise amplification apparatus of high sensitivity according to this invention is based. Assumed that an ultralow-temperature low-noise amplification apparatus is made with the same layout as the ultralow-temperature low-noise amplification apparatus 63 shown in
F=F1+(F2−1)/G1 (1)
The formula (1) teaches that it is only the noise figure F1 of the first-stage amplifying device M1 that greatly affects the noise figure F of the two-stage amplification apparatus, while it is hardly affected by the noise figure F2 of the final-stage amplifying device M2. In other words, it can be said that the noise figure of the amplification apparatus as a whole is greatly affected by the noise figure of the first-stage amplifying device, and is less affected by the noise figure of the final-stage amplifying device as the first-stage amplifying device has a higher gain. Accordingly, it is desirable to design the amplifier on the input side with a high gain and a low noise figure and reduce as much as possible any loss caused before the input to the first-stage amplifying device M1, while the noise figure of the final-stage amplifying device M2 on the output side exerts a less effect as there is a higher gain on the input side.
If only the gain, loss and noise figure are taken up in respect of the ultralow-temperature low-noise amplification apparatus 63 shown in
The high-frequency signals amplified by the first-stage amplifier 11 are delivered to a final-stage amplifier 2 through a high-frequency cable 43 and the high-frequency signals amplified by the final-stage amplifier 21 are sent through a high-frequency cable 42 and outputted through an output connector 41. Referring to the high-frequency cables, a cable formed from molybdenum having a low thermal conductivity is used as the high-frequency cable 42. This makes it possible to prevent any external heat from entering through the output connector 41. The high-frequency cable 43 may be a cable of any adequate material, but is preferably of a material of low resistivity. A low temperature holder 72 is cooled by a freezer 73, while it is positioned in contact with the superconducting filter 10 and the amplifiers 11 and 21.
A heat-insulating container 71 carrying the input and output connectors 31 and 41 and a power supply connector 51 on its sidewalls, etc. and minimizing the infiltration of any external heat encloses the high-frequency cables 32, 33, 43 and 42, the superconducting filter 10 and the amplifiers 11 and 21 tightly and shuts off the infiltration of any external heat. The heat-insulating container 71 has its interior kept vacuum by an evacuator not shown. Accordingly, the interior of the heat-insulating container 71 including the low temperature holder 72 cooled by the freezer 73 is steadily kept at a low temperature. The following is a comparison of characteristics between copper and molybdenum mentioned above as the materials for the high-frequency cables 32 and 33 and the high-frequency cable 42, respectively:
Although attention has been drawn only to the materials for the high-frequency cables in the foregoing description, it is possible to employ a device allowing for electrical connection, while cutting off any physical connection (a coupling condenser), since the signals to be processed are of an alternating current. It is also possible to use a long high-frequency cable on the output side of the apparatus. The same is applicable to any amplification apparatus not having any superconducting filter, though the foregoing description has been only of examples of apparatus having a superconducting filter. Moreover, it is needless to say that while those examples have all been of apparatus having two amplifiers, the same principle is applicable to any apparatus having more than two amplifiers.
Number | Date | Country | Kind |
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2003-362902 | Oct 2003 | JP | national |