JPH0568018A - Wireless transmission system - Google Patents
Wireless transmission systemInfo
- Publication number
- JPH0568018A JPH0568018A JP22187991A JP22187991A JPH0568018A JP H0568018 A JPH0568018 A JP H0568018A JP 22187991 A JP22187991 A JP 22187991A JP 22187991 A JP22187991 A JP 22187991A JP H0568018 A JPH0568018 A JP H0568018A
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- signal
- transmission
- reference signal
- terminal equipment
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Mobile Radio Communication Systems (AREA)
- Radio Transmission System (AREA)
- Transceivers (AREA)
- Small-Scale Networks (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、複数の端末器間でデー
タや音声などの信号をワイヤレスで送受信するワイヤレ
ス伝送方式に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless transmission system for wirelessly transmitting and receiving signals such as data and voice between a plurality of terminals.
【０００２】[0002]
【従来の技術】従来のワイヤレス伝送方式に用いる送信
回路と受信回路の構成を図５と図６にそれぞれ示す。ま
ず、送信回路１では、中間周波信号を周波数変換回路１
１に入力し、局部発振器１２からの局部発振周波信号と
混合して高周波の送受信周波信号に変換し、必要な周波
数の信号を増幅回路１３により増幅して、出力回路１４
を介してアンテナ１５から送信する。次に、受信回路２
では、アンテナ２５から入力回路２４を介して受信した
受信信号のうち、必要な周波数の信号を増幅回路２３に
より増幅し、局部発振器２２からの局部発振信号と混合
して、周波数変換回路２１により中間周波信号に変換し
て出力する。なお、出力回路１４および入力回路２４で
は、インピーダンスの整合や平衡／不平衡の変換などを
行うものである。2. Description of the Related Art Configurations of a transmission circuit and a reception circuit used in a conventional wireless transmission system are shown in FIGS. 5 and 6, respectively. First, in the transmission circuit 1, the intermediate frequency signal is converted into the frequency conversion circuit 1
1 and mixes it with the local oscillation frequency signal from the local oscillator 12 to convert it into a high frequency transmission / reception frequency signal, amplifies the signal of the required frequency by the amplifier circuit 13,
It transmits from the antenna 15 via. Next, the receiving circuit 2
Then, of the reception signals received from the antenna 25 via the input circuit 24, a signal of a necessary frequency is amplified by the amplification circuit 23, mixed with the local oscillation signal from the local oscillator 22, and then intermediated by the frequency conversion circuit 21. Converted to a frequency signal and output. The output circuit 14 and the input circuit 24 perform impedance matching and balanced / unbalanced conversion.
【０００３】[0003]
【発明が解決しようとする課題】上述のように、従来の
ワイヤレス伝送方式では、データや音声などの信号をワ
イヤレスで送受信する複数の端末器の各々が送信回路１
と受信回路２を備え、これらが局部発振器１２及び２２
を備えているために、局部発振周波数が高くなると、局
部発振器１２，２２が高価になり、各端末器に接続する
送受信回路のコストが上昇するという問題があった。As described above, in the conventional wireless transmission system, each of the plurality of terminals for wirelessly transmitting and receiving signals such as data and voice has the transmitting circuit 1.
And a receiving circuit 2, which are local oscillators 12 and 22.
Therefore, when the local oscillation frequency becomes high, the local oscillators 12 and 22 become expensive, and the cost of the transmission / reception circuit connected to each terminal increases.
【０００４】本発明は、このような点に鑑みてなされた
ものであり、その目的とするところは、局部発振周波数
が高い場合でも端末器の送受信回路を安価に構成できる
ようなワイヤレス伝送方式を提供することにある。The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wireless transmission system capable of inexpensively constructing a transmission / reception circuit of a terminal even when a local oscillation frequency is high. To provide.
【０００５】[0005]
【課題を解決するための手段】本発明のワイヤレス伝送
方式にあっては、上記の課題を解決するために、複数の
端末器間で信号をワイヤレスで送受信する系において、
図１（又は図３）に示すように、局部発振周波数の基準
信号にスクランブル（又は変調）をかけて、このスクラ
ンブル（又は変調）された基準信号を送出する送信回路
を特定の端末器に備え、他の端末器は、図２に示すよう
に、前記基準信号を受信し、受信した基準信号に基づい
て、送受信周波信号と中間周波信号との周波数変換用の
局部発振周波信号を作成する送受信回路を備えることを
特徴とするものである。According to the wireless transmission system of the present invention, in order to solve the above-mentioned problems, in a system for wirelessly transmitting and receiving a signal between a plurality of terminals,
As shown in FIG. 1 (or FIG. 3), a specific terminal is provided with a transmission circuit that scrambles (or modulates) a reference signal of a local oscillation frequency and sends out the scrambled (or modulated) reference signal. As shown in FIG. 2, another terminal receives and transmits the reference signal, and creates a local oscillation frequency signal for frequency conversion between the transmission and reception frequency signal and the intermediate frequency signal based on the received reference signal. It is characterized by including a circuit.
【０００６】[0006]
【作用】本発明のワイヤレス伝送方式では、複数の端末
器間でデータや音声などの信号をワイヤレスで送受信す
る系において、その中の特定の端末器の送信回路のみが
局部発振器を備えていれば良いので、その他の端末器の
送受信回路の局部発振器は不要となり、送受信回路が安
価に構成できる。また、基準信号にスクランブルや変調
をかけることによって、セキュリティを高めることがで
きる。In the wireless transmission system of the present invention, in a system for wirelessly transmitting and receiving signals such as data and voice between a plurality of terminals, if only the transmission circuit of a specific terminal among them has a local oscillator. Since it is good, the local oscillator of the transmission / reception circuit of the other terminals is unnecessary, and the transmission / reception circuit can be constructed at low cost. Moreover, security can be enhanced by scrambling or modulating the reference signal.
【０００７】[0007]
【実施例】以下、本発明の一実施例を図面を用いて説明
する。図１は本発明の一実施例によるワイヤレス伝送方
式に用いる特定の端末器の送信回路のブロック図であ
り、図２は他の端末器における受信回路のブロック図で
ある。特定の端末器の送信回路１では、中間周波信号を
周波数変換回路１１に入力し、スクランブル回路１８に
よってスクランブルをかけられた局部発振器１２からの
局部発振信号と混合して送受信周波信号に変換する。ま
た、スクランブル回路１８によってスクランブルをかけ
られた局部発振周波数の基準信号を増幅回路１６により
増幅し、混合回路１７により送受信周波信号と混合し
て、出力回路１４を経て、アンテナ１５から同時に送信
する。一方、他の端末器の受信回路２では、アンテナ２
５から受信した信号を、入力回路２４を経て、第１のフ
ィルタ２６と第２のフィルタ２７によりスクランブルを
かけられた基準信号と受信信号とに分離し、スクランブ
ルをかけられた基準信号を増幅回路２８により増幅して
局部発振周波信号を作成し、増幅回路２３により増幅し
た受信信号と共に周波数変換回路２１に入力し、両信号
を混合して中間周波信号に変換し、出力する。また、他
の端末器の送信回路でも図２に示した受信回路２と同様
に、特定の端末器の送信回路１からスクランブルをかけ
て送出された基準信号から局部発振周波信号を作成し、
これを中間周波信号と混合して送信周波信号に変換して
送信するものである。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a transmission circuit of a specific terminal used in a wireless transmission system according to an embodiment of the present invention, and FIG. 2 is a block diagram of a reception circuit of another terminal. In the transmission circuit 1 of a specific terminal, the intermediate frequency signal is input to the frequency conversion circuit 11, mixed with the local oscillation signal from the local oscillator 12 scrambled by the scramble circuit 18, and converted into a transmission / reception frequency signal. Further, the reference signal of the local oscillation frequency scrambled by the scramble circuit 18 is amplified by the amplifier circuit 16, mixed with the transmission / reception frequency signal by the mixing circuit 17, and simultaneously transmitted from the antenna 15 via the output circuit 14. On the other hand, in the receiving circuit 2 of another terminal device, the antenna 2
The signal received from signal No. 5 is separated into the reference signal scrambled by the first filter 26 and the second filter 27 and the received signal through the input circuit 24, and the scrambled reference signal is amplified. A local oscillating frequency signal is amplified by 28 and input to the frequency conversion circuit 21 together with the reception signal amplified by the amplification circuit 23. The both signals are mixed and converted into an intermediate frequency signal and output. Also, in the transmission circuits of other terminals, similarly to the reception circuit 2 shown in FIG. 2, a local oscillation frequency signal is created from the reference signal sent by scrambling from the transmission circuit 1 of a specific terminal,
This is mixed with an intermediate frequency signal and converted into a transmission frequency signal for transmission.
【０００８】図３は本発明の他の実施例によるワイヤレ
ス伝送方式に用いる特定の端末器の送信回路のブロック
図である。本実施例では、図１に示した実施例における
スクランブル回路１８に代えて変調回路１９を設けたも
のである。この場合には、変調をかけられた局部発振周
波数の基準信号が特定の端末器の送信回路１から送出さ
れることになる。他の端末器の送受信回路では、図１に
示した実施例と同様に、特定の端末器の送信回路１から
変調をかけて送出された基準信号から局部発振周波信号
を作成し、これを中間周波信号と混合して送信周波信号
に変換して送信したり、あるいは作成された局部発振周
波信号を受信信号と混合して中間周波信号に変換したり
するものである。変調回路１９による変調方式には、Ａ
Ｍ方式、ＦＭ方式、ＰＭ方式等の任意の方式を用いるこ
とができる。なお、白色雑音等のランダムな変調信号を
用いて基準信号に変調をかけた場合は、変調回路１９は
実質的にスクランブル回路１８と同様の機能を有するこ
とになる。FIG. 3 is a block diagram of a transmission circuit of a specific terminal used in a wireless transmission system according to another embodiment of the present invention. In this embodiment, a modulation circuit 19 is provided instead of the scramble circuit 18 in the embodiment shown in FIG. In this case, the modulated reference signal of the local oscillation frequency is transmitted from the transmission circuit 1 of the specific terminal. In the transmission / reception circuit of another terminal device, similarly to the embodiment shown in FIG. 1, a local oscillation frequency signal is created from the reference signal transmitted by being modulated by the transmission circuit 1 of a specific terminal device, and the local oscillation frequency signal is generated as an intermediate signal. It mixes with a frequency signal and converts into a transmission frequency signal for transmission, or mixes a created local oscillation frequency signal with a reception signal and converts into an intermediate frequency signal. The modulation method by the modulation circuit 19 is A
Any method such as M method, FM method and PM method can be used. When the reference signal is modulated using a random modulation signal such as white noise, the modulation circuit 19 has substantially the same function as the scramble circuit 18.
【０００９】図４は本発明の別の実施例の概略構成図で
ある。このシステムは、マイクロ波を利用してワイヤレ
スで信号伝送を行うＬＡＮ（ローカル・エリア・ネット
ワーク）である。コントロールルームＲに設置されたコ
ントロールユニットＵからの伝送信号は、マイクロ波を
用いて導波管Ｇを介して送信されている。導波管Ｇは、
複数のターミナルＴが分散して配置されたワーキングエ
リアＡの床Ｆや壁Ｗ、天井Ｃに沿って設置されている。
各ターミナルＴには、それぞれ送受信機Ｓが接続されて
いる。導波管Ｇには開口部又はスリットが設けられてお
り、ここから漏洩するマイクロ波が空間中をワイヤレス
で伝播して送受信機Ｓで受信される。逆に、送受信機Ｓ
からの伝送信号は、マイクロ波を用いて空間中をワイヤ
レスで伝播して、導波管Ｇの開口部又はスリットに達
し、この導波管Ｇを介してコントロールユニットＵまで
導かれるものである。FIG. 4 is a schematic configuration diagram of another embodiment of the present invention. This system is a LAN (Local Area Network) that wirelessly transmits signals using microwaves. A transmission signal from the control unit U installed in the control room R is transmitted via the waveguide G using microwaves. The waveguide G is
A plurality of terminals T are installed along a floor F, a wall W, and a ceiling C of a working area A in which they are arranged in a distributed manner.
A transceiver S is connected to each terminal T. The waveguide G is provided with an opening or a slit, and a microwave leaking from the waveguide G propagates wirelessly in space and is received by the transceiver S. Conversely, the transceiver S
The signal transmitted from (1) propagates wirelessly in space using microwaves, reaches the opening or slit of the waveguide G, and is guided to the control unit U via the waveguide G.
【００１０】この図４に示すシステムでは、伝送信号と
してマイクロ波を使用しているので、局部発振器が高価
になる。そこで、コントロールユニットＵにのみ局部発
振器を搭載し、他の送受信機Ｓは、コントロールユニッ
トＵの局部発振器から基準信号として伝送される局部発
振周波信号を利用して、送信及び受信を行うものであ
る。また、伝送信号は空間中に漏洩するものであるか
ら、局部発振周波信号にスクランブル又は変調をかける
ことにより、第三者による伝送信号の傍受を困難とし、
セキュリティを高めているものである。In the system shown in FIG. 4, since the microwave is used as the transmission signal, the local oscillator becomes expensive. Therefore, the local oscillator is mounted only in the control unit U, and the other transceiver S performs transmission and reception by using the local oscillation frequency signal transmitted as the reference signal from the local oscillator of the control unit U. . Further, since the transmission signal leaks into space, by scrambling or modulating the local oscillation frequency signal, it becomes difficult for a third party to intercept the transmission signal,
It enhances security.
【００１１】[0011]
【発明の効果】請求項１又は２記載の発明によれば、上
述のように、特定の端末器の送信回路から送出された基
準信号を用いて一般の端末器の送受信回路の局部発振周
波信号を作成するので、一般の端末器の送受信回路に局
部発振器が不要になり、送受信回路を安価に構成できる
という効果がある。また、従来のように各端末器の送受
信回路がそれぞれ独立した局部発振器を備える場合に
は、各局部発振器の周波数変動が問題となるのに対し
て、本発明では、局部発振周波数を全ての端末器の送受
信回路で共用することによって、中間周波数及び送受信
周波数が安定し、且つ同期も採り易くなるという効果が
ある。さらに、本発明では、局部発振周波数の基準信号
にスクランブル又は変調をかけることにより、ワイヤレ
ス伝送される信号が第三者によって傍受される可能性を
少なくすることができ、セキュリティを高めることがで
きるという効果がある。According to the invention of claim 1 or 2, as described above, the local oscillation frequency signal of the transmission / reception circuit of a general terminal is used by using the reference signal sent from the transmission circuit of a specific terminal. Since there is no need for a local oscillator in the transmission / reception circuit of a general terminal device, there is an effect that the transmission / reception circuit can be constructed at low cost. Further, in the case where the transmitter / receiver circuit of each terminal device is provided with an independent local oscillator as in the conventional case, the frequency fluctuation of each local oscillator becomes a problem, whereas in the present invention, the local oscillation frequency is set in all terminals. By sharing the same between the transmitter / receiver circuit of the device, the intermediate frequency and the transmitter / receiver frequency can be stabilized, and synchronization can be easily obtained. Furthermore, according to the present invention, by scrambling or modulating the reference signal of the local oscillation frequency, it is possible to reduce the possibility that a wirelessly transmitted signal will be intercepted by a third party, and it is possible to improve security. effective.
【図１】本発明の一実施例に用いる送信回路のブロック
図である。FIG. 1 is a block diagram of a transmission circuit used in an embodiment of the present invention.
【図２】本発明の一実施例に用いる受信回路のブロック
図である。FIG. 2 is a block diagram of a receiver circuit used in an embodiment of the present invention.
【図３】本発明の他の実施例に用いる送信回路のブロッ
ク図である。FIG. 3 is a block diagram of a transmission circuit used in another embodiment of the present invention.
【図４】本発明の別の実施例の概略構成図である。FIG. 4 is a schematic configuration diagram of another embodiment of the present invention.
【図５】従来例に用いる送信回路のブロック図である。FIG. 5 is a block diagram of a transmission circuit used in a conventional example.
【図６】従来例に用いる受信回路のブロック図である。FIG. 6 is a block diagram of a receiving circuit used in a conventional example.
１ 送信回路 ２ 受信回路 １１ 周波数変換回路 １２ 局部発振器 １３ 増幅回路 １４ 出力回路 １５ アンテナ １６ 増幅回路 １７ 混合回路 １８ スクランブル回路 １９ 変調回路 ２１ 周波数変換回路 ２３ 増幅回路 ２４ 入力回路 ２５ アンテナ ２６ フィルタ ２７ フィルタ ２８ 増幅回路 1 transmitter circuit 2 receiver circuit 11 frequency converter circuit 12 local oscillator 13 amplifier circuit 14 output circuit 15 antenna 16 amplifier circuit 17 mixing circuit 18 scramble circuit 19 modulator circuit 21 frequency converter circuit 23 amplifier circuit 24 input circuit 25 antenna 26 filter 27 filter 28 Amplifier circuit
─────────────────────────────────────────────────────
─────────────────────────────────────────────────── ───
【手続補正書】[Procedure amendment]
【提出日】平成４年１２月１日[Submission date] December 1, 1992
【手続補正１】[Procedure Amendment 1]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】０００８[Correction target item name] 0008
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【０００８】図３は本発明の他の実施例によるワイヤレ
ス伝送方式に用いる特定の端末器の送信回路のブロック
図である。本実施例では、図１に示した実施例における
スクランブル回路１８に代えて変調回路１９を設けたも
のである。この場合には、変調をかけられた局部発振周
波数の基準信号が特定の端末器の送信回路１から送出さ
れることになる。他の端末器の送受信回路では、図１に
示した実施例と同様に、特定の端末器の送信回路１から
変調をかけて送出された基準信号から局部発振周波信号
を作成し、これを中間周波信号と混合して送信周波信号
に変換して送信したり、あるいは作成された局部発振周
波信号を受信信号と混合して中間周波信号に変換したり
するものである。変調回路１９による変調方式には、Ａ
Ｍ方式、ＦＭ方式、ＰＭ方式等の任意の方式を用いるこ
とができる。なお、擬似雑音等のランダム性の変調信号
を用いて基準信号に変調をかけた場合は、変調回路１９
は実質的にスクランブル回路１８と同様の機能を有する
ことになる。FIG. 3 is a block diagram of a transmission circuit of a specific terminal used in a wireless transmission system according to another embodiment of the present invention. In this embodiment, a modulation circuit 19 is provided instead of the scramble circuit 18 in the embodiment shown in FIG. In this case, the modulated reference signal of the local oscillation frequency is transmitted from the transmission circuit 1 of the specific terminal. In the transmission / reception circuit of another terminal device, similarly to the embodiment shown in FIG. 1, a local oscillation frequency signal is created from the reference signal transmitted by being modulated by the transmission circuit 1 of a specific terminal device, and the local oscillation frequency signal is generated as an intermediate signal. It mixes with a frequency signal and converts into a transmission frequency signal for transmission, or mixes a created local oscillation frequency signal with a reception signal and converts into an intermediate frequency signal. The modulation method by the modulation circuit 19 is A
Any method such as M method, FM method and PM method can be used. When the reference signal is modulated using a random modulation signal such as pseudo noise, the modulation circuit 19
Has substantially the same function as the scramble circuit 18.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 盛野 信治 大阪府門真市大字門真1048番地 松下電工 株式会社内 (72)発明者 兵主 春彦 大阪府門真市大字門真1048番地 松下電工 株式会社内 (72)発明者 小川 温雄 大阪府門真市大字門真1048番地 松下電工 株式会社内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinji Morino 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Haruhiko Hyoho, 1048, Kadoma, Kadoma, Osaka Prefecture 72) Inventor Atsushi Ogawa 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd.
Claims (2)
送受信する系において、局部発振周波数の基準信号にス
クランブルをかけて、このスクランブルされた基準信号
を送出する送信回路を特定の端末器に備え、他の端末器
は、前記基準信号を受信し、受信した基準信号に基づい
て、送受信周波信号と中間周波信号との周波数変換用の
局部発振周波信号を作成する送受信回路を備えることを
特徴とするワイヤレス伝送方式。1. In a system for wirelessly transmitting and receiving a signal between a plurality of terminals, a specific terminal is provided with a transmission circuit for scrambling a reference signal of a local oscillation frequency and transmitting the scrambled reference signal. The other terminal device is provided with a transceiver circuit that receives the reference signal and creates a local oscillation frequency signal for frequency conversion between the transmission / reception frequency signal and the intermediate frequency signal based on the received reference signal. Wireless transmission method.
送受信する系において、局部発振周波数の基準信号に変
調をかけて、この変調された基準信号を送出する送信回
路を特定の端末器に備え、他の端末器は、前記基準信号
を受信し、受信した基準信号に基づいて、送受信周波信
号と中間周波信号との周波数変換用の局部発振周波信号
を作成する送受信回路を備えることを特徴とするワイヤ
レス伝送方式。2. In a system for wirelessly transmitting and receiving a signal between a plurality of terminals, a specific terminal is provided with a transmission circuit for modulating a reference signal of a local oscillation frequency and transmitting the modulated reference signal. The other terminal device is provided with a transceiver circuit that receives the reference signal and creates a local oscillation frequency signal for frequency conversion between the transmission / reception frequency signal and the intermediate frequency signal based on the received reference signal. Wireless transmission method.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22187991A JP2582968B2 (en) | 1991-09-02 | 1991-09-02 | Wireless transmission method |
| US07/920,874 US5355523A (en) | 1991-08-09 | 1992-07-28 | Wireless transmission/reception system including transmitting terminal producing multiple frequency local oscillation signals and receiving terminal storing a local oscillation signal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22187991A JP2582968B2 (en) | 1991-09-02 | 1991-09-02 | Wireless transmission method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0568018A true JPH0568018A (en) | 1993-03-19 |
| JP2582968B2 JP2582968B2 (en) | 1997-02-19 |
Family
ID=16773617
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP22187991A Expired - Lifetime JP2582968B2 (en) | 1991-08-09 | 1991-09-02 | Wireless transmission method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2582968B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003069792A1 (en) * | 2002-02-18 | 2003-08-21 | Communications Research Laboratory, Independent Administrative Institution | Radio communication method and system for performing communication among a plurality of radio communication terminals |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61163742A (en) * | 1985-01-12 | 1986-07-24 | Nec Corp | Privacy telephone set |
| JPS63131631A (en) * | 1986-11-20 | 1988-06-03 | Matsushita Electric Ind Co Ltd | Transmission equipment |
| JPH034142A (en) * | 1989-06-01 | 1991-01-10 | Nippon Chem Ind Co Ltd | Blaine air permeability type powder fineness measuring instrument |
-
1991
- 1991-09-02 JP JP22187991A patent/JP2582968B2/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61163742A (en) * | 1985-01-12 | 1986-07-24 | Nec Corp | Privacy telephone set |
| JPS63131631A (en) * | 1986-11-20 | 1988-06-03 | Matsushita Electric Ind Co Ltd | Transmission equipment |
| JPH034142A (en) * | 1989-06-01 | 1991-01-10 | Nippon Chem Ind Co Ltd | Blaine air permeability type powder fineness measuring instrument |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003069792A1 (en) * | 2002-02-18 | 2003-08-21 | Communications Research Laboratory, Independent Administrative Institution | Radio communication method and system for performing communication among a plurality of radio communication terminals |
| US7302236B2 (en) | 2002-02-18 | 2007-11-27 | National Institute Of Information And Communications Technology | Radio communication method and system for performing communication among a plurality of radio communication terminals |
| CN100392991C (en) * | 2002-02-18 | 2008-06-04 | 独立行政法人情报通信研究机构 | Radio communication method and system for communication between a plurality of radio communication terminals |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2582968B2 (en) | 1997-02-19 |
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