JPH11215020A - Base station device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base station device capable of increasing the number of speech channels, without deteriorating the receiving characteristic. SOLUTION: An low-noise amplifier(LNA) 3 is placed at the preceding stage of an antenna shared unit 9, and the radio frequency signal received via the LNA 3 is branched into two signals by the unit 9. These branched frequency signals are led to receivers BA and BB, which contain the inter-receiving stage band-pass filters(BPF) 4, the 1st Mix(mixing) circuits 5 and the 1st intermediate frequency(IF) filters 6 respectively. Furthermore, the gain is given to the LNA 3 to satisfactorily compensate the branching loss of the unit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile / mobile phone system and a simple mobile phone system (PHS).
and a base station device in a mobile communication system such as an andyphone system.

[0002]

2. Description of the Related Art In recent years, with the increase in needs for mobile communication and the development of communication technology, the installation and expansion of mobile communication systems are rapidly progressing. This type of system includes a plurality of base stations forming a wireless zone called a cell, and a plurality of mobile stations connected to the base station via a wireless line in the wireless zone. Can accommodate mobile stations within the range of traffic respectively set for each wireless zone.

[0003] For example, P which is one form of mobile communication system
In the case of HS, the radio access scheme between each base station and each mobile station includes four-channel multiplex multi-carrier TDMA (TiDMA).
me Division Multiple Access)-TDD (Time Divis
ion Duplex) method. This type of access method includes, for example, a plurality of radio frequencies f1 as shown in FIG.
To fm, four transmission time slots T1 to T4 for a forward link used for communication from a base station (denoted as CS) to each mobile station (denoted as PS), From the base station CS to each mobile station P
4 time slots R for reverse link towards S
The wireless communication is performed by using pairs of the time slots T1 to T4 for the forward link and the time slots R1 to R4 for the reverse link as channels.

[0004] That is, four channels are provided for each radio frequency. In the PHS, one of the channels is used as a control channel, and the remaining three channels are used as communication channels. Note that the radio frequency for each channel is dynamically switched for each channel as needed when establishing a line between the base station CS and the mobile station PS.

The base station CS is roughly divided into a radio section for transmitting and receiving radio frequency signals, a modem section for modulating and demodulating digital signals, and multiplexing of digital data according to TDMA-TDD time slots. And a TDMA section for performing separation and separation, an interface section for interfacing with a communication line (I 'line), and a control section for controlling these radio sections, a modem section, a TDMA section, and an interface section.

[0006] FIG. 7 shows a configuration of a receiving section related to the reception of a radio frequency signal in the radio section. The reception unit shown in FIG. 7 converts a reception signal output from the reception antenna input terminal 1 into a reception high-frequency band-pass filter (reception high-frequency BPF) 2.
And the signal is amplified by a low noise amplifier (LNA) 3. The amplified signal is further reduced in noise by a band-pass filter between receiving stages (BPF between receiving stages) 4 and mixed with a local signal from a frequency synthesizer (not shown) by a first mixing circuit (1st Mix) 5 for reception. The received intermediate frequency is output from a first intermediate frequency output terminal (1st IF output terminal) 7 via a first intermediate frequency filter (1st IF filter) 6. After the first IF output terminal 7, a second mixing circuit (not shown), an intermediate frequency amplifier, and a detector are connected in order.

[0007] With the recent increase in communication demand,
The number of users who own PHS terminals as mobile stations PS is increasing day by day. For this reason, for example, in a downtown area where many people are concentrated, even if an attempt is made to make a call from a PHS terminal, the communication channel of the base station CS has no free space.
Frequently outgoing calls can occur. The situation is the same when an incoming call is made to a PHS terminal, and a situation can often occur in which an incoming call cannot be received despite the fact that the power of the incoming PHS terminal is ON and that it is present in the cell.

[0008] This is because, as described above, one base station CS can provide only a maximum of three communication channels. In order to eliminate such inconvenience, the number of communication channels in one wireless zone may be increased.

Therefore, recently, two sets of a radio unit, a modem unit, a TDMA unit, and an interface unit are provided in one base station CS, and a control unit shared by each system is provided. It is considered to increase the number of channels by operating these in parallel based on control. That is, four channels provided by each system are combined into eight channels, one of which is used as a control channel and the remaining seven channels are used as communication channels.

In this case, compared to a case where two base stations CS are simply installed in one radio zone (in this case, each base station CS has one control channel, Channels are totaled 6 channels), and one more channel can be used as a communication channel. That is, since up to seven people can talk at the same time in one wireless zone, the effect of eliminating congestion is greater.

The base station CS of this type and the mobile station P
The wireless access method between the S and the S will be described with reference to FIG. In FIG. 9, columns of upper and lower time slots correspond to respective systems in the base station CS. Here, the system in the base station CS corresponding to the upper time slot sequence is A system, and the base station C corresponding to the lower time slot sequence is
The system in S will be described as a B system.

From the A system, four channels are provided at different frequencies f1, f3, f6, f2. On the other hand, from the B system, four channels are provided at different frequencies f4, f5, f2, and f7. At this time,
By using different frequencies for each system in the same time slot, the number of channels can be doubled while preventing interference. If the time slots are different, the same frequency (f2 in FIG. 9) can be used in the A system and the B system.

FIG. 8 shows the configuration of a part related to the reception of a radio frequency signal in the radio part of the base station CS that enables such a system. The configuration of FIG. 8 includes a receiving unit A1 and a receiving unit A2 each having the configuration of FIG.
Is split into two by the antenna sharing device 9 and guided to the receiving antenna input terminal 1 of each of the receiving unit A1 and the receiving unit A2.

The received signal input to each receiving antenna input terminal 1 is output from the first IF output terminal 7 of each of the receiving sections A1 and A2 through the same process as described above. It is led to the mixing circuit.

According to the above configuration, the configuration of the receiving unit in the current 4-channel type base station apparatus is used as it is,
This is convenient because the receiving unit of the base station CS that provides one communication channel can be simply configured.

However, one problem to be solved has occurred here. That is, in the base station CS having the above configuration,
The distribution loss inevitably generated in the antenna duplexer 9 (about -3
Noise figure (NF) for dB)
Is deteriorated, and the receiving sensitivity is deteriorated. Note that the noise figure NF is a value obtained by dividing the noise power at the output end of the device by the product of the noise power at the input end and the gain of the device in decibels. The characteristics will be good.

For example, as shown in FIGS. 10A and 10B, in the case of a 4-channel type base station that does not use an antenna duplexer, even if the reception NF viewed from the LNA 3 at the subsequent stage is 3 dB, the reception NF at the preceding stage is Assuming that the loss of the provided reception high-frequency BPF 2 is, for example, 1 dB, the reception NF value viewed from the reception antenna input terminal 1 is 4 dB. That is, the reception characteristics are degraded due to the reception high frequency BPF2.

On the other hand, as shown in FIGS. 11A and 11B, the received NF value is further increased by 3 dB due to the antenna duplexer 9 provided before the receiving high-frequency BPF 2.
As a result, the reception NF value viewed from the antenna terminal 8 is 7 dB. That is, the provision of the antenna duplexer 9 further deteriorates the reception characteristics.

To summarize the above description, the conventional base station apparatus has a problem that the number of communication channels cannot be increased without sacrificing an increase in the received NF value. An increase in the reception NF value is not preferable because it not only causes a decrease in reception sensitivity but also becomes a root cause of various problems such as a narrow service area.

[0020]

As described above, the conventional base station apparatus has a configuration in which a high frequency signal received by an antenna is branched by an antenna duplexer and then guided to a plurality of receiving sections. In this case, the distribution loss directly affects the reception characteristics of each system, which causes a problem that the service area is narrowed.

The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a base station apparatus capable of increasing the number of communication channels without deteriorating reception characteristics.

[0022]

To achieve the above object, the present invention provides a mobile station having a base station apparatus and a plurality of mobile stations communicating with the base station apparatus via a radio line. In the base station device used in the communication system, one antenna, from a radio frequency signal received by this antenna, a signal of a frequency band used in the mobile communication system is selected by, for example, a band filter and the like. High-frequency receiving means for adjusting and outputting the gain of the selected signal by, for example, a low-noise amplifier, branching means for branching the output of the high-frequency receiving means into a plurality of outputs, and output of the high-frequency receiving means branched by the branching means A frequency converter that is provided corresponding to each of the signals and that performs frequency conversion by mixing the signal input from the branching unit with, for example, an oscillation output of a frequency synthesizer in a mixer circuit. Characterized by comprising at least comprises a plurality of receiving means stages.

In this case, the plurality of receiving means include:
The signal branched on the high frequency receiving means is given. That is, instead of amplifying the signal degraded by the branching loss in the branching unit by the low noise amplifier of each receiving unit, the radio frequency signal is amplified in advance by the low noise amplifier of the high frequency receiving unit, and then branched. It will be a way to guide you.

For this reason, compared with the case where the signal degraded by the branching unit is amplified by each receiving unit, an increase in the received NF value due to the branching loss at the branching unit can be further suppressed.

Further, the present invention is characterized in that the high-frequency receiving means has an amplification gain sufficient to at least compensate for a branch loss of the branching means. In this way, the radio frequency signal received by the antenna is amplified beforehand by an amount for compensating for the branch loss generated in the branching unit, and then supplied to the branching unit. That is, from the receiving means side, a signal of the same quality as that without the branching means can be given.

Therefore, even if the number of communication channels is increased by adopting a multiplex configuration, it is possible to prevent the reception characteristics from deteriorating. Further, conventionally, provided in each of the multiplexed receiving units, the receiving high-frequency band-pass filter as a bandpass filter and the low-noise amplifier can be shared by a plurality of receiving units in the above configuration, Effects such as reduction in the number of parts and space saving can also be obtained.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit block diagram showing a configuration of a base station apparatus according to an embodiment of the present invention.

A radio frequency signal arriving from a mobile station (not shown) is received by an antenna 60 having four antenna elements such as rod antennas, and then received by SD (Space).
Diversity) are combined by the combiner 70 and guided to the reception high-frequency band-pass filter (reception high-frequency BPF) 2 via the high-frequency switch (SW) 101 of the radio unit 10. Here, the band-limited received signal is converted to a low noise amplifier (LNA).
After being amplified by 3, the signal is branched into two by the antenna duplexer 9 and guided to the receiving units BA and BB, respectively.

Here, the gain of the low noise amplifier (LNA) 3 is set to a level that is at least sufficient to compensate for the branch loss in the antenna duplexer 9. That is, it differs from the gain setting in the receiving units A1 and A2 in the conventional configuration.

In each of the receiving units BA and BB, the input radio frequency signal is
A local signal generated by frequency synthesizers 102BA and 102BB provided corresponding to A and the receiving section BB is mixed and frequency-converted to a received intermediate frequency signal. The frequency synthesizer 102
The oscillation frequency of the local signal generated in BA and 102BB is instructed from control unit 50 according to the radio channel frequency.

The radio section 10 is provided with reception field strength detection sections (RSSI) 103BA and 103BB corresponding to the reception sections BA and BB, respectively. RSSI 103BA and 103BB respectively
Then, the received electric field strength of the radio frequency signal arriving from each mobile station is detected, and the detected value is notified to the control unit 50 for an empty channel search or the like.

The received intermediate frequency signals output from the receiving units BA and BB are transmitted to the demodulating unit 201BA of the modem unit 20.
And 201BB. Demodulation unit 201
In BA and 201BB, the received intermediate frequency signal is digitally demodulated, thereby reproducing a digital communication signal. TDMA decoding section 3 of TDMA section 30
In 01BA and 301BB, the digital communication signal is decomposed for each time slot of the radio channel according to the instruction of the control unit 50, and the decomposed digital communication signal is input to the interface unit 40.

The interface unit 40 includes an adaptive difference PC
M transcoder (ADPCM-TRANSCODE)
R) 401BA, 401BB, and a line interface unit 402 are provided. TDMA decoding section 301
The digital communication signals output from BA and 301BB are applied to adaptive difference PCM transcoder 401, respectively.
After being decoded by BA and 401BB, it is transmitted from the line interface unit 402 to the public communication network (not shown) via the I 'line IL.

On the other hand, the I 'line IL
Are input to the adaptive difference PCM transcoders 401BA and 401BB via the line interface unit 402, and are encoded here, and then encoded by the TDMA encoding unit 302B.
A, 302BB. In the TDMA encoding units 302BA and 302BB, the adaptive difference P
Output signals from the CM transcoders 401BA and 401BB are inserted into predetermined time slots and multiplexed, and the multiplexed digital signal is
2BA and 202BB are respectively input.

In the modulators 202BA and 202BB, the carrier signal is digitally modulated by the digital signal, and the modulated carrier signal is transmitted to the transmitters 104BA and 104BA.
04BB respectively. Transmitting unit 104BA, 1
In 04BB, the modulated carrier signal is frequency-converted to a radio channel frequency specified by the control unit 50 by mixing with the local signal generated by the frequency synthesizers 102BA and 102BB, and furthermore, a predetermined transmission power is set. Amplified to the level. Then, the radio frequency signals output from the transmission units 104BA and 104BB are combined by the combiner 105, and then transmitted from the high frequency switch 101 to the mobile stations (not shown) from the antenna 60 via the SD combiner 70. .

FIG. 2 is a circuit block diagram showing a configuration of a receiving section in the base station apparatus according to the embodiment of the present invention. The receiving unit according to the present embodiment (each code is B
A and BB) are bandpass filters between receiving stages (between receiving stages B and B) in the configuration of the conventional receiving unit A1 and receiving unit A2.
PF) 4 and first mixing circuit (1st Mix) 5
And a first intermediate frequency filter (1st IF filter) 6. Then, a reception high-frequency band-pass filter (reception high-frequency BPF) 2 and a low-noise amplifier (LNA) 3 are provided outside the respective reception units BA and BB, and a radio-frequency signal received at the antenna terminal 8 is received by the reception high-frequency BPF 2. After the band is limited and amplified by the LNA 3, the signal is branched into two by the antenna duplexer 9 and guided to the receiving unit BA and the receiving unit BB, respectively.

With the above configuration, the radio frequency signal arriving at the antenna 60 is amplified by the LNA 3 and then input to the antenna duplexer 9. LNA
3 is set so as to compensate for the branch loss of the antenna duplexer 9, so from the viewpoint of the receiving units BA and BB,
It looks as if a radio frequency signal not passing through the antenna duplexer 9 is input.

As shown in FIG. 3 (a), the amplification gain of the LNA 3 is set to, for example, 3d when the reception NF looking at the subsequent stage from the LNA 3 is 3d.
B (that is, it differs from the gain setting in the conventional configuration by the amount of the antenna duplexer 9). By doing so, even if a loss of 1 dB occurs in the reception high-frequency BPF 2 connected in front of the LNA 3, the reception NF value viewed from the antenna terminal 8 can be suppressed to 4 dB as shown in FIG. . That is, it is possible to obtain reception characteristics equivalent to those of a four-channel base station that does not use the antenna duplexer 9.

Next, a change in the NF value when the gain of the LNA 3 is the same as that of the 4-channel type base station will be described with reference to FIGS. That is, in the present embodiment, the LNA 3 is provided in a stage preceding the duplexer 9 and
Although the gain setting of the NA3 is changed from the conventional one, the change of the NF value when the gain setting of the LNA3 in the above configuration is the same as the conventional one will be described.

First, the BPF between the receiving stages is provided after the LNA3.
4, NF value (NF) viewed from LNA 3 when connected to 1st Mix 5, 1st IF filter 6 (referred to as configuration 1).
An example of calculation of 0) will be shown. FIG. 4 shows an LNA together with the above configuration.
3 are G1 and NF1, respectively, and the gain and NF value of the inter-receiving stage BPF4 are G2 and NF, respectively.
The gain and NF value of 2, 1st Mix5 are G
3, NF3, the gain of the first IF filter 6 and the NF value are G4 and NF4, respectively, G1 to G4, NF1
The figure showing the numerical example of -NF4 is shown. NF with the above configuration
0 is calculated as follows.

[0041]

(Equation 1)

That is, NF0 in Configuration 1 is 3.25d
B. Next, after the LNA 3, the antenna duplexer 9
, BPF4 between receiving stages, 1st Mix5, 1st
LN when connected to IF filter 6 (referred to as configuration 2)
A calculation example of the NF value (NF0) viewed from A3 is shown. FIG.
In addition to the above configuration, the gain and the NF value of the LNA 3 are respectively set to G1, NF1, the antenna duplexer 9, and the BP between the receiving stages.
The gain of the stage combined with F4 and the NF value are G
2 is a diagram showing numerical examples of G1 to G4 and NF1 to NF4, where the gain and NF value of NF2 and 1st Mix5 are G3 and the gain and NF value of NF3 and 1stIF filter 6 are G4 and NF4, respectively. FIG.
The values of G2 and NF2 are different. Now, NF0 in the above configuration is calculated as follows.

[0043]

(Equation 2)

That is, NF0 in the configuration 2 is 4.62d
B. Comparing the two calculation results, it can be seen that the NF value of Configuration 2 is 1.37 dB worse than that of Configuration 1. However, this deterioration amount is smaller than the 3 dB deterioration that occurs when the antenna duplexer 9 is disposed before the LNA 3. In other words, by merely arranging the antenna duplexer 9 after the LNA 3 without changing the gain setting of the LNA 3, it is possible to suppress the deterioration of the NF value smaller than in the case where the reception signal via the antenna duplexer 9 is provided to the LNA 3. Is possible.

Incidentally, for reference, in the configuration 2, the LNA
3 is 13 dB (NF of the element alone is 1.
NF value (NF at 5 dB) viewed from LNA3
The calculation example of 0) is shown below.

[0046]

(Equation 3)

That is, in the configuration 2, the gain of the LNA 3 is set to 13
Assuming dB, NF0 is 3.32 dB, which is almost the same value as NF0 of Configuration 1. Thus, in the present embodiment, the LNA 3 is arranged before the duplexer 9 and the LN
The radio frequency signal transmitted through A3 is divided into two by the antenna sharing device 9, and the divided radio frequency signal is transmitted to the BPF between the receiving stages.
4, 1st Mix5, and 1stIF filter 6, respectively. At this time, the antenna sharing device 9 is connected to the LNA 3.
The gain is sufficient to compensate for the branch loss.

Therefore, when viewed from each of the receivers BA and BB, it appears as if a radio frequency signal not passing through the antenna duplexer 9 is input. Deterioration of reception characteristics can be prevented.

In this embodiment, the reception high-frequency BPF
2 and the LNA 3 are shared by the receiving unit BA and the receiving unit BB, so that the number of parts can be reduced and the effect is large in terms of space saving and the like.

The present invention is not limited to the above embodiment. For example, in the configuration of FIG.
While properly setting the gain of the receiving high frequency BPF2 and LN
The connection order of A3 may be reversed, or a new element may be inserted between the LNA 3 and the antenna duplexer 9. In short, before the radio frequency signal from the antenna terminal 8 is input to the antenna duplexer 9, the radio frequency signal is amplified in advance, so that the antenna duplexer 9 appears as if viewed from the receiver BA and the receiver BB. The object of the present invention is achieved by inputting a radio frequency signal that is not passed through.

In the above embodiment, the antenna 60
Is provided with four antenna elements such as a rod antenna, but the number of antenna elements can be any number as necessary, and the shape is also a dipole antenna or a Yagi having directivity, for example. It can be arbitrarily modified as an antenna or the like.

In the above embodiment, the present invention is applied to the PHS system. However, the present invention is not limited to this. For example, the present invention can be applied to other mobile communication systems such as a mobile phone system. It is possible. In addition, various modifications can be made without departing from the spirit of the present invention.

[0053]

As described above in detail, according to the present invention, the high-frequency receiving means is provided before the branching means, and the high-frequency receiving means is provided with a gain higher than the compensation for the branch loss of the branching means. In addition, it is possible to provide a base station apparatus capable of increasing the number of communication channels without deteriorating reception characteristics.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of a base station apparatus according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a receiving unit in the base station apparatus according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating reception N of a reception unit according to the embodiment of the present invention.
The figure which shows a mode that an F value changes.

FIG. 4 shows a BPF4 between reception stages and a first stage after an LNA3.
Mix5, the configuration when connected to the first IF filter 6, the LNA 3, the BPF4 between receiving stages, the first Mix5,
FIG. 6 is a diagram illustrating a numerical example of each gain and NF value of the stIF filter 6.

FIG. 5 shows a configuration in which the LNA 3 is connected to the inter-reception-stage BPF 4, the 1st Mix 5, and the 1st IF filter 6 via the antenna sharing device 9, and the LNA 3, the antenna sharing device 9 and the inter-reception stage BPF 4 are combined. Dan, 1stM
FIG. 9 is a diagram illustrating a numerical example of each gain and NF value of the ix5 and the first IF filter 6;

FIG. 6 shows a four-channel multiplex multicarrier TDMA-T.
The figure which shows the frame structure of DD system.

FIG. 7 is a circuit block diagram showing a configuration of a standard receiving circuit used for a conventional base station.

FIG. 8 is a circuit block diagram showing a configuration of a part related to reception of a radio frequency signal in a radio part of a conventional eight-channel base station.

FIG. 9 is a diagram used to explain a wireless access scheme between an 8-channel type base station and a mobile station.

FIG. 10 is a diagram showing how a received NF value of a conventional four-channel base station changes.

FIG. 11 is a diagram showing how a received NF value of a conventional 8-channel base station changes.

[Explanation of symbols]

1: reception antenna input terminal 2: reception high-frequency band-pass filter (reception high-frequency BP)
F) 3 Low noise amplifier (LNA) 4 Bandpass filter between receiving stages (BPF between receiving stages) 5 First mixing circuit (1st Mix) 6 First intermediate frequency filter (1stIF filter) 7 First intermediate frequency Output terminal (1st IF output terminal) 8: Antenna terminal 9: Antenna duplexer A1, A2: Receiving unit in conventional base station device BA, BB: Receiving unit in base station device according to embodiment of the present invention 10: Radio unit 101: High frequency switch (SW) 102BA, 102BB: Frequency synthesizer 103BA, 103BB: Received electric field strength detection unit (RSS)
I) 104BA, 104BB ... transmitting section 105 ... combiner 20 ... modem section 201BA, 201BB ... demodulation section 202BA, 202BB ... modulation section 30 ... TDMA section 301BA, 301BB ... TDMA decoding section 302BA, 302BB ... TDMA encoding section 40 ... interface section 401BA, 401BB ... Adaptive difference PCM transcoder (ADPCM-TRANSCODER) 402 ... Line interface section IL ... I 'line 60 ... Antenna 70 ... SD (Space Diversity) combiner

Claims (2)

[Claims] 1. A base station apparatus used in a mobile communication system including a base station apparatus and a plurality of mobile stations communicating with the base station apparatus via a radio channel, wherein one antenna is provided. A high-frequency receiving means for selecting a signal in a frequency band used in the mobile communication system from a radio frequency signal received by the antenna, adjusting a gain of the selected signal, and outputting the selected signal; Branching means for branching the output signal into a plurality of signals; and frequency converting means provided corresponding to each of the output signals of the high-frequency receiving means branched by the branching means and frequency-converting the signal input from the branching means. And a plurality of receiving means comprising at least: 2. The base station apparatus according to claim 1, wherein said high-frequency receiving means has an amplification gain sufficient to at least compensate for a branch loss of said branching means.