Patent Application
20080037590
Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. Thorough the embodiments and examples, the same reference symbols refer to the same elements and overlapped explanation will be avoided. Further, the respective figures referred to are schematic views for explaining the embodiments and facilitating its understanding. For convenience of illustration, there are some parts different from those in an actual device in their shape, size, ratio, etc. These parts can be appropriately changed with reference to the following explanation and known techniques.
As shown in
Now it is assumed that each of the delay circuits 17 to 22 includes a line with an impedance of 50Ω and with an optimum electrical length for providing a desired branching characteristic. The circuit parameter of each of the band-pass filters 2 to 5 for the corresponding channels may be optimized to provide their desired branching characteristic.
A superconductive microstrip line is formed on an MgO substrate (not shown) having a thickness of about 0.43 mm and a dielectric constant of about 10. Now, the microstrip line is made of superconductor. The superconductor may be an yttrium-based copper oxide superconductor thin film having a thickness of about 500 nm. The line width of the microstrip line is about 0.4 mm. The superconductor thin film may be formed by various methods such as laser vapor-deposition, sputtering or cooperative vapor deposition.
A signal inputted from an input portion 30 passes the band-pass filters 2, 3, 4 and 5 for the corresponding channels through the delay circuits 17, 18, 19, 20, 21 and 22 and outputted from the output portions 31, 32, 33 and 34 for the respective channels.
Each of the band-pass filters 2 to 5 for the respective channels is constituted of a pseudo-elliptic function type ten-pole filter having ten hairpin resonators and two transmission lines 41 for coupling the resonators. Namely,
The multiplexer according to the first embodiment including a first band-pass filter for a first channel, which has a first branching characteristic having a center frequency of f1 and an attenuation pole at a frequency of fa1; and
a second band-pass filter for a second channel, which is formed in a microstrip line on the dielectric substrate and has a second branching characteristic having a center frequency of f2 and an attenuation pole at a frequency of fa2. The following relationships (1) to (5) are satisfied:
f1<f2 (1);
f1<fa1 (2);
fa2<f2 (3);
f2−fa1<(f2−f1)/2 (4); and
fa2−f1<(f2−f1)/2 (5).
As a result of investigation by the inventors of this invention, it was ascertained that when the branching characteristic of the band-pass filter for the second channel at the frequency fa1 is −20 dB or less and the branching characteristic of the band-pass filter for the first channel at the frequency fa2 is −20 dB or less, the transient signal degradation can be suppressed. Namely, by locating the attenuation pole within the guard band for the first channel and second channel, the transient signal degradation can be suppressed thereby to realize a desired branching characteristic for the adjacent channels.
Now, it may be desirable that a part of the multiplexer has a superconductive characteristic. Further, the multiplexer may be formed on a single dielectric substrate. The electric lengths of the lines connected to the respective filters from the input portion of the multiplexer may be variable.
The first to fourth channels have center frequencies of 2.000 GHz, 2.005 GHz, 2.010 GHz and 2.015 GHz, respectively.
Assuming that f1=2.000 GHz and f2=2.005 GHz,
f1<f2 (1)
is satisfied.
The branching characteristic of the band-pass filter for the first-channel has an attenuation pole at fa1=2.00253 GHz and the branching characteristic of the band-pass filter for the second-channel has an attenuation pole at fa2=2.00243 GHz. Then,
f1<fa1 (2)
fa2<f2 (3)
f2−fa1<(f2−f1)/2 (4)
fa2−f1<(f2−f1)/2 (5)
are satisfied.
The branching characteristic of the band-pass filter for the second channel at fa1 is −49.97 dB not larger than −20 dB. Further, the branching characteristic of the band-pass filter for the first channel at fa2 is −46.00 dB not larger than −20 dB.
By satisfying the relationships (1) to (5), the attenuation poles can be located within the guard band for the first and second channels. Thus, the transient signal degradation can be suppressed thereby to realize the desired branching characteristic for the adjacent channel. Incidentally, the guard band is determined according to the communication system. In this example, it refers to the range of −20 dB capable of suppressing the transient signal degradation. In
Assuming that f1=2.005 GHz and f2=2.010 GHz, relationship (1) is satisfied.
The branching characteristic of the band-pass filter for the first-channel has an attenuation pole at fa1=2.00758 GHz and the branching characteristic of the band-pass filter for the second-channel has an attenuation pole has an attenuation pole at fa2=2.00742 GHz. Then, the relationships (2) to (5) are satisfied.
The branching characteristic of the band-pass filter for the second channel at fa1 is −39.68 dB not larger than −20 dB. Further, the branching characteristic of the band-pass filter for the first channel at fa2 is −40.32 dB not larger than −20 dB. Namely, by satisfying the above relationships, the attenuation poles can be located within the guard band for the first and second channels. Thus, the transient signal degradation can be suppressed thereby to realize the desired branching characteristic for the adjacent channel.
Assuming that f1=2.010 GHz and f2=2.015 GHz, relationship (1) is satisfied. Further, the branching characteristic of the band-pass filter for the first channel has an attenuation pole at fa1=2.01257 GHz and the branching characteristic of the band-pass filter for the second channel has an attenuation pole at fa2=2.01247 GHz. Then, the relationships (2) to (5) are satisfied.
Further, branching characteristic of the band-pass filter for the second channel at fa1 is −46.38 dB not larger than −20 dB. Further, the branching characteristic of the band-pass filter for the first channel at fa2 is −49.51 dB not larger than −20 dB. Namely, by satisfying the above relationships, the attenuation poles can be located within the guard band for the first and second channels. Thus, the transient signal degradation can be suppressed thereby to realize the desired branching characteristic for the adjacent channel.
Now, the electric lengths of the delay circuits 17 to 22 are 104 degree, 74 degree, 197 degree, 231 degree, 242 degree and 169 degree, respectively, which are indicated with reference to 2 GHz. These electric lengths are not the sole solution and there are also other solutions. So, the convenient solution for implementing may be selected.
In the first embodiment, equal bandwidths are allocated to all the four channels. However, the channel having a different bandwidth may be included.
The branching lines constituting the delay circuits are different from those shown in
Now, the electric lengths of the delay circuits 17 to 22 are 213 degree, 148 degree, 201 degree, 155 degree, 204 degree and 156 degree, respectively, which are indicated with reference to 2 GHz. These electric lengths are not the sole solution and there are also other solutions. So, the convenient solution for implementing may be selected.
The arrangement of the input portion and output portion may be convenient for implementing as compared with that shown in
According to the above configuration, the multiplexer is capable of branching each adjacent channel employed for communication and the wireless receiver is capable of suppressing the intermodulation distortion due to an in-band signal thereby to improve an equivalent C/N and effectively use a given communication frequency band to enable large capacity communication.
An explanation will be given of the wireless receiver according to a second embodiment.
The wireless receiver includes a multiplexer 0 for branching the received signal from an antenna. The respective output portions of the multiplexer 0 are connected to LNAs 6, 7, 8 and 9 which are connected to mixers 13, 14, 15 and 16, at their subsequent stage, respectively. These mixers are connected to baseband processor BB-IC at their subsequent stage, respectively. The antenna is employed for both signal transmission and reception. A transmit signal is transmitted from the antenna through a duplexer. The received signal is received from the antenna and supplied to the multiplexer 0 through the duplexer.
In the multiplexer 0, input signals are branched into respective signal with the corresponding channel, which are sent to the corresponding output portion. The signals with the respective channel separated by the multiplexer 0 are amplified by the LNAs 6 to 9. The signals amplified by the LNAs are frequency-converted to the baseband by the mixers 13 to 16 and supplied to the baseband processors BB-ICs.
Now, the mixers 13 to 16 are directly connected to the baseband processors at their subsequent stage, respectively. It is not necessary to frequency-convert the signals from the LNAs into the baseband at one time. The signals may be frequency-converted to the baseband after once converted in the intermediate frequencies IFs. Then, the mixers 13, 14, 15 and 16 may be connected to IF filters, amplifiers and mixers at their subsequent stage, which are connected to the baseband processors at their subsequent stage. It should be noted that the wireless receiver may include the multiplexer shown in
As shown in
In
Thus, by controlling the switches 11 and 12, the wireless receiver, as shown in
In the third embodiment, only the filter for the guard band for the channels A and B is provided. However, a filter for a guard band for any channels may be provided. Further, in the third embodiment, two channels are merged, but three or more channels may be merged.
In the third embodiment, the wireless receiver includes the multiplexer shown in
In the third embodiment, the mixers 13, 14, 15 are directly connected to the baseband processors BB-ICs at their subsequent stage, respectively. However, it is not necessary to frequency-convert the signals from the LNAs to the baseband at one time. The signals may be frequency-converted to the baseband after once converted in the intermediate frequencies IFs. Then, the mixers 13, 14, 15 and 16 may be connected to IF filters, amplifiers and mixers at their subsequent stage, which are connected to the baseband processors at their subsequent stage.
In the third embodiment, equal bandwidths are allocated to all the four channels. However, the channel having a different bandwidth may be included.
In the multiplexer 0, the electrical length of each line connected from the input portion to the respective band-pass filter may be variable. The gain of each the LNAs may be also variable. The gain of the LNA is varied by changing the current passing through the LNA by incorporating a variable attenuator in the subsequent stage of the LAN. The gain may be reduced to the case where plural channel signals are multiplexed. The electric length is varied by locating a dielectric material approximated to the above of the microstrip line.
According to the third embodiment, the wireless receiver capable of instantaneously changing the bandwidth of each channel according to the kind or quantity of communication information can be realized, thereby implementing large-capacity wireless communication using a channel with a large bandwidth.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-215446 | Aug 2006 | JP | national |
