JP3592562B2 - High sensitivity radio - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a base station radio for use in, for example, a mobile communication system, and more particularly to a high-sensitivity radio in which the reception sensitivity is improved by cooling a high-frequency receiver.
[0002]
[Prior art]
FIG. 5 shows a basic configuration of a conventional high-sensitivity wireless device. This conventional high-sensitivity radio receiver includes an antenna terminal 1, a signal in a desired reception band selected from signals input to the antenna terminal 1 and passed therethrough, and a first reception band filter 2 made of a non-superconducting material. A second reception band filter 3 made of a superconducting material for selecting and passing a signal in a desired reception band from an output of the first reception band filter 2 and removing an input outside the band; A reception low-noise amplifier 4 for amplifying the output of the filter 3 to a desired level with low noise, and a reception output terminal 5 for outputting an output signal from the reception low-noise amplifier 4 are provided. The transmission signal input terminal 6 includes a transmission band filter 7 that selects a signal in a transmission band from signals input to the transmission signal input terminal 6 and passes the signal. One end of each of the first reception band filter 2 and the transmission band filter 7 is coupled to the antenna side by a coupling circuit 8, and a duplexer 9 is configured by the first reception band filter 2, the transmission band filter 7, and the coupling circuit 8. . The second reception bandpass filter 3 and the reception low-noise amplifier 4 are sealed in a heat shielding box 10 and are insulated from the outside, and are cooled by a cooling means 11 via a cooling member 11a. Further, a first power supply terminal 12 for supplying power to the reception low noise amplifier 4 and a second power supply terminal 13 for supplying power to the cooling means 11 are provided.
[0003]
The second reception band-pass filter 3 and the reception low-noise amplifier 4 are sealed in a heat shield box 10 for blocking heat intrusion from the outside by, for example, vacuum insulation, and the cooling means 11 stabilizes an extremely low temperature of, for example, several tens of K for a long time. It is composed of cryogenic refrigerators that can be maintained as such, and these can use commercially available products.
As described above, the second reception band-pass filter 3 and the reception low-noise amplifier 4 are stably cooled to a very low temperature for a long time, so that the thermal noise generated in the second reception band-pass filter 3 and the reception low-noise amplifier 4 is extremely limited. And the insertion loss of the second reception bandpass filter 3 can be reduced. As a result, the noise figure of the receiver shown in FIG. 5 is greatly improved, and the receiving sensitivity is greatly improved. Therefore, by using the high-sensitivity radio shown in FIG. 5, it is possible to obtain, for example, a specified C / N (carrier power / noise power) reception output even for a low-level reception signal. Thus, it is possible to obtain the effect that the transmission power on the transmission side required to obtain the reception output of the C / N is small.
[0004]
Also, by forming the second reception bandpass filter 3 of a superconducting material and setting the superconducting state by the cooling means 11, a very steep attenuation characteristic can be obtained. As a result, the selectivity of the receiver shown in FIG. 5 can be increased, and radio interference from an adjacent band can be significantly reduced. Therefore, by using the high-sensitivity radio shown in FIG. 5, even if the frequency interval (guard band) between the own band signal and the adjacent band signal is narrowed, the radio wave interference can be kept low, and the frequency use efficiency is greatly increased. The effect is obtained.
[0005]
As the second reception bandpass filter 3, a microstrip line type filter, a cavity resonator type filter, a dielectric resonator type filter, a semi-coaxial type filter, or the like can be used, and all of the electrodes are made of a superconducting material. The above effects can be obtained.
By the way, the superconducting material constituting the second reception bandpass filter 3 loses superconductivity when a current higher than the critical current flows, so that when the power applied to the second reception bandpass filter 3 increases, the characteristics of the filter deteriorate. Therefore, when the second reception band filter 3 is directly coupled to the coupling circuit 8, a strong input outside the reception band received by the antenna or a signal passed through the transmission band filter is added to the second reception band filter 3. In addition, the characteristics of the second reception band-pass filter 3 may be deteriorated. Therefore, in the high-sensitivity radio of FIG. 5, the first reception bandpass filter 2 is provided outside the heat shield box 10 on the input side of the second reception bandpass filter 3, and a high power signal outside the reception band is passed through the second reception bandpass filter. The filter 3 is attenuated to a level at which the characteristics do not deteriorate. As the first reception bandpass filter 2, a microstrip line type filter, a cavity resonator type filter, a dielectric resonator type filter, a semi-coaxial type filter or the like is used, and these electrodes are made of metal such as gold. .
[0006]
Here, an example of the transmission characteristics of each filter is shown in FIG. In the first reception band-pass filter 2, signals outside the reception band need only be attenuated to such an extent that the characteristics of the second reception band-pass filter 3 are not deteriorated. Insertion loss can be kept low. Since the second reception bandpass filter 3 made of a superconducting material has a steep attenuation characteristic, a steep attenuation characteristic can be obtained as a whole receiver.
[0007]
[Problems to be solved by the invention]
In the conventional high-sensitivity radio, the first reception band-pass filter 2 is provided outside the heat shielding box 10, so that the insertion loss of the first reception band-pass filter 2 greatly affects the reception sensitivity. When the power of the signal outside the reception band or the transmission signal received by the antenna is relatively low, the attenuation of the transmission band by the first reception band filter 2 may be small, and thus the attenuation characteristic of the first reception band filter 2 is moderate. , The insertion loss can be kept low. However, when the power of the transmission signal is high, for example, several tens of W to 100 W, or when there is a possibility that a high-level out-of-band signal is input from the antenna such as in an urban area, the attenuation of the transmission band by the first reception band filter 2. Must be increased, resulting in a problem that the insertion loss increases in order to obtain a desired attenuation characteristic.
[0008]
An object of the present invention is to provide a high-sensitivity radio capable of performing high-sensitivity reception even when the first reception band filter 2 is used to prevent an excessive input to the second reception band filter 3.
[0009]
[Means for Solving the Problems]
The present invention relates to a first reception band filter to which a reception signal from an antenna is input, a transmission band filter through which a transmission signal output to the antenna passes, and an antenna side of the transmission band filter and the first reception band filter A second receiving bandpass filter connected to the output side of the first receiving bandpass filter, and a receiving low noise amplifier connected to the output side of the second receiving bandpass filter. The second reception bandpass filter and the reception low noise amplifier are sealed in a heat shield box and cooled by cooling means, and the second reception bandpass filter is made of a superconducting material, and is brought into a superconducting state by the cooling means. It is assumed that a high-sensitivity wireless device is used.
[0010]
In the invention of claim 1, said first receiving band-pass filter is constituted by a non-superconductive material, the part enclosed in the heat shield box making, cooled by the cooling means.
In the invention of claim 2, the first reception band filter has a portion having an attenuation pole at a transmission band frequency.
According to the third aspect of the present invention, the portion to be cooled of the first reception bandpass filter is constituted by a microstrip line using a metal thin film, and the second reception bandpass filter is constituted by a microstrip line using a superconducting thin film. The cooled portion of the first reception bandpass filter and the second reception bandpass filter are formed on the same substrate.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows one proposal example, and the same reference numerals are given to portions corresponding to FIG. This proposed example is different from FIG. 5 in that the first reception bandpass filter 2 is sealed in a heat shielding box 10 and cooled by a cooling means 11 via a cooling member 11a. By cooling the first reception bandpass filter 2 in this way, thermal noise generated there can be reduced to the utmost, and high reception sensitivity can be obtained even when the first reception bandpass filter 2 is used.
[0012]
FIG. 2 shows an embodiment of the first aspect of the present invention. In this embodiment, the first receiving bandpass filter 2 is divided into a normal temperature portion 2a and a cooled portion 2b, and the cooled portion 2b is sealed in a heat shielding box 10 and cooled by a cooling means 11 via a cooling member 11a. I have. When the power input to the first reception band-pass filter 2 is very large, when the entire first reception band-pass filter 2 is cooled as shown in FIG. The cable connecting to the first reception bandpass filter 2 must also be thick enough to withstand high power, and the amount of heat that enters the heat shield box 10 through the cable increases. Therefore, the cooling capacity of the cooling means 11 needs to be increased, and the size of the entire apparatus must be increased. In such a case, the first receiving bandpass filter 2 is divided into the first few stages (normal temperature portion 2a) and the remaining portion (cooled portion 2b) of which insertion loss is negligible, and only the cooled portion 2b is divided. By cooling, the same effect as that shown in FIG. 1 can be obtained without increasing the load on the cooling means 11. The room temperature portion 2a and the cooled portion 2b may be formed of different types of filters such as a dielectric resonator type filter on one side and a microstrip line type filter on the other side.
[0013]
The cooled portion 2b (the first reception band filter 2 in FIG. 1) has an attenuation pole at the transmission band frequency. 3A and 3B show examples of transmission characteristics of the cooled portion 2b. When one antenna is used for both transmission and reception, the first reception band-pass filter 2 particularly needs to greatly attenuate signals in the transmission band. Therefore, as shown in FIG. 3A, by forming the cooled portion 2b with an attenuation pole at the transmission band frequency, a desired attenuation characteristic can be obtained with a small number of stages, and as a result, the insertion loss can be suppressed low. In FIG. 3A, the cooled portion 2b has bandpass characteristics and pole attenuation characteristics, but as shown in FIG. 3B, the room temperature portion 2a has bandpass characteristics and the cooled portion 2b has pole attenuation characteristics. It may be. Further, the normal temperature portion 2a may be provided with an attenuation pole at the transmission band frequency instead of the cooled portion 2b.
[0014]
According to the second aspect of the present invention, the cooled portion 2b and the second reception bandpass filter 3 are particularly constituted by a microstrip line type filter, and the circuit using the metal material constituting the cooled portion 2b and the second reception bandpass filter 3 are formed. The circuit using the superconducting material is formed on the same substrate.
FIG. 4 shows an example of a circuit manufacturing method, and the procedure will be described below. (A) First, a superconducting thin film is formed on both surfaces of a substrate by sputtering or the like. (B) Next, a desired circuit pattern of the second reception bandpass filter 3 is formed by photolithography. (C) Subsequently, the circuit of the produced superconducting thin film is protected with a photoresist or the like, and a metal material such as gold for forming the cooled portion 2b is formed by vacuum evaporation or the like. (D) A desired circuit pattern of the portion to be cooled 2b is formed by photolithography. (E) Remove unnecessary photoresist.
[0015]
By forming the cooled portion 2b and the second reception bandpass filter 3 made of a metal material on the same substrate in this way, it is possible to reduce the size of the circuit, and the cooled portion 2b and the second reception bandpass filter are formed. 3 can be reduced as much as possible.
[0016]
【The invention's effect】
As described above, according to the present invention, in order to prevent an excessive input to the second reception bandpass filter in which the electrodes are made of a superconducting material, the first reception band in which the electrodes are made of a metal material before the second reception bandpass filter. Even when a bandpass filter is provided, high reception sensitivity can be maintained by cooling part or all of the first reception bandpass filter together with the second reception bandpass filter. Also, by providing an attenuation pole at the transmission band frequency in the portion to be cooled or the room temperature portion of the first reception band filter, the number of filters required in the first reception band filter can be reduced, and higher sensitivity can be achieved. . Furthermore, the circuit can be miniaturized by forming both the cooled portion of the first reception bandpass filter and the second reception bandpass filter on the same substrate by a microstrip line.
[Brief description of the drawings]
FIG. 1 is a block diagram showing one proposed example.
FIG. 2 is a block diagram showing an embodiment of the invention of claim 1;
FIG. 3 is a diagram showing an example of a transmission characteristic of a filter according to the invention of claim 1 ;
FIG. 4 is a diagram showing an example of a circuit manufacturing method according to the embodiment of the second invention.
FIG. 5 is a block diagram showing a configuration of a conventional high-sensitivity wireless device.
FIG. 6 is a diagram illustrating an example of transmission characteristics of a first reception bandpass filter and a second reception bandpass filter.

Claims (2)

A first reception band filter to which a reception signal from the antenna is input, a transmission band filter through which a transmission signal output to the antenna is passed, and one end of each of the transmission band filter and the first reception band filter on the antenna side A coupling circuit for coupling, a second reception bandpass filter connected to an output side of the first reception bandpass filter, and a reception low-noise amplifier connected to an output side of the second reception bandpass filter; The second reception bandpass filter and the reception low-noise amplifier are sealed in a heat shielding box and cooled by cooling means, and the second reception bandpass filter is made of a superconducting material, and is in a superconducting state by the cooling means. In the radio,
It said first receiving band-pass filter consists of a room temperature portion having a bandpass characteristic, a band pass characteristic and the transmission band frequency and a cooling portion having a damping characteristic due to pole, and is composed of a non-superconductive material, said cooling section is above A high-sensitivity wireless device sealed in a heat shielding box and cooled by the cooling means. In high sensitivity radio of claim 1 Symbol placement,
The portion to be cooled of the first reception bandpass filter is constituted by a microstrip line using a metal thin film, and the second reception bandpass filter is constituted by a microstrip line using a superconducting thin film. A high-sensitivity radio, wherein the cooling part and the second reception bandpass filter are formed on the same substrate.

Images