JPH0352346A - Spread spectrum communication system - Google Patents
Spread spectrum communication systemInfo
- Publication number
- JPH0352346A JPH0352346A JP1186797A JP18679789A JPH0352346A JP H0352346 A JPH0352346 A JP H0352346A JP 1186797 A JP1186797 A JP 1186797A JP 18679789 A JP18679789 A JP 18679789A JP H0352346 A JPH0352346 A JP H0352346A
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- 238000001228 spectrum Methods 0.000 title claims abstract description 13
- 230000005540 biological transmission Effects 0.000 claims abstract description 30
- 230000001360 synchronised effect Effects 0.000 claims abstract description 6
- 230000010355 oscillation Effects 0.000 description 4
- 230000008929 regeneration Effects 0.000 description 3
- 238000011069 regeneration method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
Abstract
Description
【発明の詳細な説明】 （イ）産業上の利用分野 本発明はスペクトラム拡散通信システムに関する。[Detailed description of the invention] (b) Industrial application fields The present invention relates to spread spectrum communication systems.
（ロ）従来の技術
従来、情報信号よりも充分広いスペクトラム幅をもつ例
えば２進の疑似雑音符号（Ｐｓｅｕｄｏ Ｎｏｉｓｅｃ
ｏｄｅ）で変調されたキャリアを送信し、受信側では送
信側で用いたのと同一の符号で受信信号を乗算すること
により元の情報を復調する、所謂スペクトラム拡散通信
が知られている（例えば、電子科学１９７８午１１月号
参照）。(b) Conventional technology Conventionally, for example, a binary pseudo-noise code (Pseudo Noise
So-called spread spectrum communication is known, in which a carrier modulated with ode) is transmitted, and the receiving side demodulates the original information by multiplying the received signal by the same code used on the transmitting side (for example, , see Electronic Science, November 1978 issue).
斯るスペクトラム拡散通信では、上述したように広いス
ペクトラム幅を有する符号で情報信号を変調しているた
め、情報信号を正確に復調するには受信側で生或する符
号を送信側の符号と同期させる必要がある。In such spread spectrum communication, the information signal is modulated with a code having a wide spectrum width as described above, so in order to accurately demodulate the information signal, the code generated on the receiving side must be synchronized with the code on the transmitting side. It is necessary to do so.
上記同期を取るために、通常、初期位相を合わせるだめ
の符号同期捕捉回路と位相関係を保持するための符号同
期保持回路とを設けている。In order to achieve the above synchronization, a code synchronization acquisition circuit for adjusting the initial phase and a code synchronization holding circuit for maintaining the phase relationship are usually provided.
尚、符号同期捕捉回路としては、符号位相を少しづつず
らしながら同期を判定していくスライディングサーチ同
期回路やＳＡＷ素子等による整合フィルタ同期回路があ
り、また符号同期保持回路としては、ＤＬＬやタウ・デ
ィザが知られている。As code synchronization acquisition circuits, there are sliding search synchronization circuits that determine synchronization while shifting the code phase little by little, and matched filter synchronization circuits using SAW elements, etc., and as code synchronization holding circuits, there are DLLs, tau, etc. Dithering is known.
（ハ）発明が解決しようとする課題
上述した符号同期捕捉回路及び符号同期保持回路（以下
、総称して符号同期回路と称す）は、複雑な購或を有し
ており、システムの小型化、低消費電力化等を図る上で
大きな問題となっていた。(c) Problems to be Solved by the Invention The code synchronization acquisition circuit and the code synchronization holding circuit (hereinafter collectively referred to as code synchronization circuits) described above have complicated components, and it is necessary to reduce the size of the system. This has been a major problem in efforts to reduce power consumption.
殊に、デュプレックス通信システムに適用した場き、相
方の通信機に上記符号同期回路を設けることになり、シ
ステムが高額になっていた。In particular, when applied to a duplex communication system, the code synchronization circuit must be provided in the communication device of the other party, making the system expensive.
（二）課題を解決するための手段
上記の点に鑑み、本発明は第１の符号発生回路、送信回
路及び受信回路を有し、第１の符号発生回路からの第１
の符号により送信信号の信号スペクトラムを拡散した後
、前記送信回路を介して送信すると共に前記第１の符号
発生回路からの第１の符号と所定の位相関係にある第２
の符号により前記受信回路にて受信された信号を逆拡散
する第１の通信機と、第２の符号発生回路、この第２の
符号発生回路から出力される符号の位相を受信信号に含
まれる符号の位相と同期させる符号同期回路、送信回路
及び受信回路を有し、受信信号に含まれる符号と同期し
た前記第２の符号発生回路からの第３の符号により受信
信号を逆拡散すると共に前記第２の符号発生回路からの
第３の符号と所定の位相関係にある第４の符号により送
信信号の信号スペクトラムを拡散した後、送信回路を介
して送信する第２の通信機とを具備したことを特徴とす
る。(2) Means for Solving the Problems In view of the above points, the present invention includes a first code generating circuit, a transmitting circuit, and a receiving circuit, and the first code generating circuit generates a first code from the first code generating circuit.
After spreading the signal spectrum of the transmission signal by the code, the second code is transmitted through the transmission circuit and has a predetermined phase relationship with the first code from the first code generation circuit.
a first communication device that despreads the signal received by the receiving circuit according to the code; a second code generation circuit; a phase of the code output from the second code generation circuit is included in the received signal; It has a code synchronization circuit that synchronizes with the phase of the code, a transmitting circuit, and a receiving circuit, and despreads the received signal using the third code from the second code generating circuit that is synchronized with the code included in the received signal, and and a second communication device that spreads the signal spectrum of the transmission signal by a fourth code having a predetermined phase relationship with the third code from the second code generation circuit, and then transmits the signal through the transmission circuit. It is characterized by
（ホ）作 用
本発明に依れば、第２の通信機は、第１の通信機からの
信号に含まれる符号と同期した第３の符号により受信信
号を逆拡散すると共にその同期符号と所定の位相関係に
ある第４の符号にて送信信号の信号スペクトラムを拡敢
して送信する。(e) Function According to the present invention, the second communication device despreads the received signal using a third code synchronized with the code included in the signal from the first communication device, and also synchronizes the received signal with the third code included in the signal from the first communication device. The signal spectrum of the transmission signal is expanded and transmitted using a fourth code having a predetermined phase relationship.
方、第ｌのＪ６信機は第２の通信機からの信号を第２の
符号により逆拡散する。そのとき、第１の符号発生回路
は第２の通信機からの信号に含まれる符号によって符号
同期制御を受けない。On the other hand, the l-th J6 transmitter despreads the signal from the second transmitter using the second code. At that time, the first code generation circuit is not subjected to code synchronization control by the code included in the signal from the second communication device.
（へ）実施例
第１図は本発明の一実施例を示す図である。図において
、（１）は第１の通信機で、自走的にＭ系列符号若しく
はゴールド符号を発生する第１符号発生回路（１ａ）と
、第１符号発生回路（１ａ）からの第１符号と送信デー
タとを二入力とするＥＸ−ＯＲ回路（ｌｂ）と、キャリ
ア発振器（ＩＣ）からの発振信号（キャリア信号）とＥ
Ｘ−ＯＲ回路（１ｂ）の出力とを乗算する第１乗算器（
１ｄ）と、第１乗算器（１ｄ）の出力を所定送信レベル
まで増幅する増幅器を含む送信回路（１ｅ）と、キャリ
ア発振器（１ｆ）からの発振信号と遅延回路（１ｇ）に
て遅延された第２の符号とを乗算する第２乗算器（ｌｈ
）と、この第２乗算器（１ｈ）の出力と受信回路（１１
）からの受信信号とを乗算する第３乗算Ｇ（ｌｊ）と、
第３乗算器（１ｊ）の出力端に接続され、情報或分に相
応する帯域幅そ有するバンドパスフィルタ（ＢＰＦ）（
ｌｋ）と、このＢＰＦ （ｌｋ）の出力端に接続され、
受信データを復調するデータ復調回路（ＩＬ）と、送受
信アンテナ（１ｍ）と、アンテナ（１ｍ）に接続され、
送信フィルタと受信フィルタとよりなるｒユプレクサ（
Ｉｎ）とを備えている。(F) Embodiment FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, (1) is a first communication device, which includes a first code generation circuit (1a) that autonomously generates an M-sequence code or a gold code, and a first code generated from the first code generation circuit (1a). An EX-OR circuit (lb) which has two inputs: and transmission data, an oscillation signal (carrier signal) from a carrier oscillator (IC), and an
a first multiplier (
1d), a transmission circuit (1e) including an amplifier that amplifies the output of the first multiplier (1d) to a predetermined transmission level, and an oscillation signal from the carrier oscillator (1f) and a delay circuit (1g). A second multiplier (lh
), the output of this second multiplier (1h) and the receiving circuit (11
), a third multiplication G(lj) that multiplies the received signal from
A bandpass filter (BPF) (
lk) and the output terminal of this BPF (lk),
Connected to a data demodulation circuit (IL) that demodulates received data, a transmitting/receiving antenna (1 m), and an antenna (1 m),
An r-uplexer consisting of a transmitting filter and a receiving filter (
In).
（２）は第２の通信機で、送受信アンテナ（２ａ）と、
アンテナ（２ａ）に接続されたデュプレクサ（２ｂ）と
、第２符号発生回路（２ｃ）と、第２符号発生回路（２
ｃ）からの第３の符号とキャリア発振器（２ｄ）からの
キャリア信号とを乗算する第４乗算器（２ｅ）と、この
第４乗算器（２ｅ）の出力と受信回路（２ｆ）からの受
信信号とを乗算する第５乗算器（２ｇ）と、この第５乗
算器（２ｇ）の出力端に接続され、情報戊分に相応する
帯域幅を有するＢ Ｐ Ｆ （２ｈ）と、このＢＰＦ（
２ｈ）の出力端に接続され、受信データを復調するデー
タ復調回路（２１）と、同じ＜ Ｂ Ｐ Ｆ （２ｈ）
の出力端に接続されたエンベロープ検波器（２Ｊ）と、
このエンベロープ検波器（２ｊ ）の出力に応じて第２
符号発生回路（２ｃ）から出力される符号の位相を制御
する符号同期回路（２ｋ）と、ジッタ補正回路’（ ２
Ｌ ）と、ジノタ補正回路（２Ｌ）からの符号クロン
クにより符号を再生する符号再生回路（２ｍ）と、符号
再生回路（２ｍ）からの第４符号と送信データとを二入
力とするＥＸ−ＯＲ回路（２ｎ）と、キャリア発振ｔＴ
ｈ（２ｐ）からのキャリア信号とＥＸ−ＯＲ回路（２ｎ
）の出力とを乗算する第６乗算器（２ｑ）と、第６乗算
器（２ｑ）の出力を所定送信レベルまで増幅する増幅器
を含む送信回路（２ｒ）とを備えている。(2) is a second communication device, which includes a transmitting and receiving antenna (2a),
A duplexer (2b) connected to the antenna (2a), a second code generation circuit (2c), and a second code generation circuit (2c) connected to the antenna (2a).
a fourth multiplier (2e) that multiplies the third code from c) by the carrier signal from the carrier oscillator (2d), and the output of this fourth multiplier (2e) and reception from the receiving circuit (2f). a fifth multiplier (2g) that multiplies the signal; a BPF (2h) connected to the output terminal of the fifth multiplier (2g) and having a bandwidth corresponding to the information;
Same as the data demodulation circuit (21) which is connected to the output terminal of 2h) and demodulates the received data.
An envelope detector (2J) connected to the output end of
According to the output of this envelope detector (2j), the second
A code synchronization circuit (2k) that controls the phase of the code output from the code generation circuit (2c), and a jitter correction circuit' (2
L), a code regeneration circuit (2m) that regenerates the code using the code clock from the Ginota correction circuit (2L), and an EX-OR that has two inputs: the fourth code from the code regeneration circuit (2m) and the transmission data. Circuit (2n) and carrier oscillation tT
The carrier signal from h (2p) and the EX-OR circuit (2n
), and a transmission circuit (2r) including an amplifier that amplifies the output of the sixth multiplier (2q) to a predetermined transmission level.
次に、動作について説明する。Next, the operation will be explained.
第１の通信器（１）からの送信データは、ＥＸ−ＯＲ回
路（１ｂ）で、第１符号発生回路（１ａ）からの第１符
号と排他的論理和がとられた後、第■釆算器（１ｄ）へ
供給される。第１乗算器（１ｄ）では、ＥＸ−ＯＲ回路
（１ｂ）からの出力（即ち、拡散符号）にてキャリア発
振Ｂ（ｌｃ）からの送信キャリアを２相位相変調する。The transmission data from the first communication device (1) is subjected to an exclusive OR with the first code from the first code generation circuit (1a) in the EX-OR circuit (1b), and then It is supplied to the calculator (1d). The first multiplier (1d) performs two-phase phase modulation on the transmission carrier from the carrier oscillation B (lc) using the output (ie, spreading code) from the EX-OR circuit (1b).
斯様に２相位相変調された送信キャ１アは、送信回路（
ｌｅ）で所定送信レベルまで増幅された後、アンテナ（
１ｍ）を介して放射される。The transmitting carrier subjected to binary phase modulation in this manner is transmitted to the transmitting circuit (
le) to a predetermined transmission level, then the antenna (
1 m).
この信号を受信した第２の通信機（２）は、第２符号発
生回路（２ｃ〉からの第３符号にて２相位相変調された
キャリア発振器（２ｄ）からの信号と受信信号を乗算す
ることにより逆拡散を行なう。The second communication device (2) that receives this signal multiplies the received signal by the signal from the carrier oscillator (2d) which is two-phase modulated with the third code from the second code generation circuit (2c). By doing this, despreading is performed.
斯様に逆拡散された信号は、Ｂ Ｐ Ｆ （２ｈ）で不
要信号を除去された後、データ復調回路（２１）に供給
され、復調される。また、Ｂ Ｐ Ｆ （２ｈ）の出力
は、エンベロープ検波器（２ｊ）にも供給され、相関度
を示す信号が導出される。符号同期回路（２ｋ）は、相
関度を示す信号が所定値に達するまで符号位相を変化さ
せ、そして所定値を越えた後はＤＬＬやタウ・ディザに
て同期状態を維持するよう第２符号発生回路（２ｃ）を
制御する。After unnecessary signals are removed from the thus despread signal at B P F (2h), the signal is supplied to the data demodulation circuit (21) and demodulated. Further, the output of B P F (2h) is also supplied to an envelope detector (2j), and a signal indicating the degree of correlation is derived. The code synchronization circuit (2k) changes the code phase until the signal indicating the degree of correlation reaches a predetermined value, and after it exceeds the predetermined value, generates a second code using DLL or tau dither to maintain the synchronized state. Control the circuit (2c).
一方、第２の通信機（２）からの送信データは、ＥＸ−
ＯＲ回路（２ｎ）で符号再生回路（２ｍ）からの第４符
号と排他的論理和がとられた後、第６乗算器（２ｑ）に
供給される。On the other hand, the transmission data from the second communication device (2) is
After being exclusive ORed with the fourth code from the code reproducing circuit (2m) in the OR circuit (2n), it is supplied to the sixth multiplier (2q).
ところで、第２符号発生回路（２ｃ）からの第３符号は
、符号同期回路（２ｋ）の雑音ループ帯域幅に相当する
ジッタを有している。本実施例では、このジッタを補正
するために、例えば雑音ループ帯域幅の小さいＰＬＬよ
りなるジンタ補正回路（２Ｌ）で符号クロックを補正し
、この符号クロックで第３符号を再クロツクして第４符
号を得るようにしている。By the way, the third code from the second code generation circuit (2c) has jitter corresponding to the noise loop bandwidth of the code synchronization circuit (2k). In this embodiment, in order to correct this jitter, the code clock is corrected using a jitter correction circuit (2L) consisting of a PLL with a small noise loop bandwidth, and the third code is reclocked using this code clock, and the fourth code is I'm trying to get the sign.
尚、符号発生回路（２Ｃ）のジッタが回路定数の選択等
により既に十分小さければ、ジッタ補正回路（２Ｌ）及
び符号再生回路（２ｍ）は省略することができる。Incidentally, if the jitter of the code generation circuit (2C) is already sufficiently small due to the selection of circuit constants, etc., the jitter correction circuit (2L) and the code regeneration circuit (2m) can be omitted.
サテ、第６ 乗’Ｊｉｌ−６ （２ｑ）テｉｉ、ＥＸ−
ＯＲ回路（２ｎ）からの出力（拡散符号）にてキャリア
発振器（２Ｐ）からの送信キャリアを２相位相変調する
。斯様に２相位相変調された送信キャリアは、送信回路
（２ｒ）で所定送信レベルまで増幅さ！１た後、アンテ
ナ（２ａ）介して放射される。Sate, 6th power 'Jil-6 (2q) Teii, EX-
The output (spreading code) from the OR circuit (2n) performs two-phase phase modulation on the transmission carrier from the carrier oscillator (2P). The transmission carrier subjected to binary phase modulation in this manner is amplified to a predetermined transmission level in the transmission circuit (2r)! 1 and then radiated via the antenna (2a).
この信号を受信した第１の通信機（１）は、第１符号発
生回路（１ａ）からの第１符号を遅延させた第２符号に
て２相位相変調されたキャリア発信器（１ｆ）からの信
号と受信信号を乗算することにより逆拡散を行なう。The first communication device (1) that received this signal transmits the signal from the carrier oscillator (1f), which is binary-phase modulated with a second code obtained by delaying the first code from the first code generation circuit (1a). Despreading is performed by multiplying the signal by the received signal.
斯様に逆拡散された信号は、Ｂ Ｐ Ｆ （ｌｋ）で不
要信号を除去された後、データ復調回路（ＩＬ）に供給
され、復調される。The thus despread signal has unnecessary signals removed by B P F (lk), and is then supplied to a data demodulation circuit (IL) and demodulated.
上記実施例において信号を正確に復調するには、第１符
号発生回路（１ａ）から第２の通信機（２）の乗算器（
２ｇ）へ至る信号遅延時間をｔ，、第２符号発生回路（
２Ｃ）から乗算器（２ｇ）へ至る信号遅延時間をｔ，、
第２符号発生回路（２Ｃ）から第１の通信損（１）の乗
算器（１ｊ）へ至る信号遅延時間をｔ，、第１符号発生
回路（１ａ）から乗算Ｗ（ｌｊ）へ至る信号遅延時間を
ｔ，としたとき、ｔ ，： ｔ ＋ − ｔ ，＋ ｔ
，を満足する必要がある。In the above embodiment, in order to accurately demodulate the signal, the first code generation circuit (1a) must be connected to the multiplier (2) of the second communication device (2).
2g) is the signal delay time t, and the second code generation circuit (
The signal delay time from 2C) to the multiplier (2g) is t,,
The signal delay time from the second code generation circuit (2C) to the multiplier (1j) of the first communication loss (1) is t, and the signal delay from the first code generation circuit (1a) to the multiplication W (lj). When time is t, t,: t + - t, + t
, must be satisfied.
斯る条件を満たすためには、両通信機間の符号同期がと
れた後、Ｂ Ｐ Ｆ （ｌｋ）出力が最大となるよう遅
延回路（１ｇ）の遅延時間を調整すれば良い。In order to satisfy this condition, the delay time of the delay circuit (1g) may be adjusted so that the B P F (lk) output is maximized after code synchronization between both communication devices is achieved.
尚、第１符号発生回路（ｌａ）の符号と第２符号発生回
路（２Ｃ）の符号とは、符号系列及び符号周期を同一に
する必要はなく、符号周朗が同じか又は符号周期が互い
に整数比の関係にあるものを用いることが出来る。It should be noted that the code of the first code generation circuit (la) and the code of the second code generation circuit (2C) do not need to have the same code series and code period. Those having an integer ratio relationship can be used.
（ト）発明の効果
本発明に依れば、第１の通信機における符号同期回路を
削除することが出来るので、小型化、低消費電力化並び
に低廉価を図れる。(G) Effects of the Invention According to the present invention, since the code synchronization circuit in the first communication device can be omitted, it is possible to achieve miniaturization, lower power consumption, and lower cost.
第１図は本発明の一実施例を示す図である。
（１）・・・第１の通信機、（１ａ）・・・第１符号発
生回路、（１ｅ）・・・送信回路、（１１）・・・受信
回路、（２）・・・第２の通信機、（２ｃ）・・・第２
符号発生回路、（２ｆ）・・・受信回路、（２ｋ）・・
・符号同期回路、（２ｒ）・・・送信回路。FIG. 1 is a diagram showing an embodiment of the present invention. (1)...First communication device, (1a)...First code generation circuit, (1e)...Transmission circuit, (11)...Reception circuit, (2)...Second communication device, (2c)...second
Code generation circuit, (2f)...Reception circuit, (2k)...
- Code synchronization circuit, (2r)...transmission circuit.
Claims (1)
し、第１の符号発生回路からの第１の符号により送信信
号の信号スペクトラムを拡散した後、前記送信回路を介
して送信すると共に前記第１の符号発生回路からの第１
の符号と所定の位相関係にある第２の符号により前記受
信回路にて受信された信号を逆拡散する第１の通信機と
、第２の符号発生回路、この第２の符号発生回路から出
力される符号の位相を受信信号に含まれる符号の位相と
同期させる符号同期回路、送信回路及び受信回路を有し
、受信信号に含まれる符号と同期した前記第２の符号発
生回路からの第３の符号により受信信号を逆拡散すると
共に前記第２の符号発生回路からの第３の符号と所定の
位相関係にある第４の符号により送信信号の信号スペク
トラムを拡散した後、送信回路を介して送信する第２の
通信機とを具備したことを特徴とするスペクトラム拡散
通信システム。(1) It has a first code generation circuit, a transmission circuit, and a reception circuit, and after spreading the signal spectrum of the transmission signal by the first code from the first code generation circuit, it is transmitted via the transmission circuit. and a first code from the first code generating circuit.
a first communication device that despreads the signal received by the receiving circuit using a second code having a predetermined phase relationship with the code of a code synchronization circuit, a transmitting circuit, and a receiving circuit for synchronizing the phase of the code contained in the received signal with the phase of the code contained in the received signal, and a third code generating circuit synchronized with the code contained in the received signal; The received signal is despread by the code, and the signal spectrum of the transmitted signal is spread by the fourth code having a predetermined phase relationship with the third code from the second code generating circuit, and then the signal is transmitted through the transmitting circuit. A spread spectrum communication system comprising: a second communication device for transmitting data.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1186797A JPH0352346A (en) | 1989-07-19 | 1989-07-19 | Spread spectrum communication system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1186797A JPH0352346A (en) | 1989-07-19 | 1989-07-19 | Spread spectrum communication system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0352346A true JPH0352346A (en) | 1991-03-06 |
Family
ID=16194756
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1186797A Pending JPH0352346A (en) | 1989-07-19 | 1989-07-19 | Spread spectrum communication system |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0352346A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5737329A (en) * | 1995-04-14 | 1998-04-07 | Kabushiki Kaisha Toshiba | Spread spectrum communication apparatus |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61227438A (en) * | 1985-04-01 | 1986-10-09 | Hitachi Ltd | Spread spectrum communication system |
-
1989
- 1989-07-19 JP JP1186797A patent/JPH0352346A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61227438A (en) * | 1985-04-01 | 1986-10-09 | Hitachi Ltd | Spread spectrum communication system |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5737329A (en) * | 1995-04-14 | 1998-04-07 | Kabushiki Kaisha Toshiba | Spread spectrum communication apparatus |
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