EP1020042A1 - Utilisation de plusieurs antennes pour limiter la reflexion speculaire - Google Patents

Utilisation de plusieurs antennes pour limiter la reflexion speculaire

Info

Publication number
EP1020042A1
EP1020042A1 EP98954928A EP98954928A EP1020042A1 EP 1020042 A1 EP1020042 A1 EP 1020042A1 EP 98954928 A EP98954928 A EP 98954928A EP 98954928 A EP98954928 A EP 98954928A EP 1020042 A1 EP1020042 A1 EP 1020042A1
Authority
EP
European Patent Office
Prior art keywords
signal
antenna
receiver
specular
combining
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.)
Withdrawn
Application number
EP98954928A
Other languages
German (de)
English (en)
Inventor
James H. Thompson
William R. Panton
Mohammad Ali Tassoudji
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Qualcomm Inc
Original Assignee
Qualcomm Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Qualcomm Inc filed Critical Qualcomm Inc
Publication of EP1020042A1 publication Critical patent/EP1020042A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0891—Space-time diversity
    • H04B7/0894—Space-time diversity using different delays between antennas
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/0842—Weighted combining
    • H04B7/0865—Independent weighting, i.e. weights based on own antenna reception parameters

Definitions

  • the present invention relates generally to diversity processing in spread-spectrum satellite communication systems. More specifically, the present invention relates to using multiple antennas to mitigate the effects of specular reflection on signal reception.
  • a typical satellite-based communication system comprises at least one terrestrial base station, central station, or hub (hereinafter referred to as a gateway); at least one user terminal, remote station, or mobile station (for example, a mobile telephone); and at least one satellite for relaying communications signals between the gateway and the user terminal.
  • the gateway provides links from one or more user terminals to other user terminals or linked communication systems, such as a terrestrial telephone system.
  • TDMA time division multiple access
  • FDMA frequency division multiple access
  • CDMA code division multiple access
  • Communication satellites form beams which illuminate a "spot" produced by projecting satellite communication signals onto the Earth's surface.
  • a typical satellite beam pattern for a spot comprises a number of beams arranged in a predetermined coverage pattern.
  • each beam comprises a number of CDMA channels or so-called sub-beams, covering a common geographic area, each occupying a different frequency band.
  • PN spreading a method of spread-spectrum transmission that is well known in the art, produces a signal for transmission that has a bandwidth much greater than that of the underlying data signal.
  • PN spreading codes or binary sequences are used to discriminate between signals transmitted by a gateway over different beams, and their timing is used to discriminate between multipath signals.
  • PN codes are shared by all communication signals within a given beam, and typically consist of 2 to 2 code chips with preselected chip periods or chipping rates on the order of 1.22 Mhz, although other code lengths and rates are well known.
  • channelizing codes are used to discriminate between signals intended for particular user terminals or wireless receivers transmitted within a beam or CDMA channel on the forward link. That is, a unique orthogonal channel is provided for each user terminal on the forward link by using a unique "channelizing" orthogonal code.
  • Walsh functions are generally used to implement the channelizing codes, with a typical length being on the order of 64 code chips for terrestrial systems and 128 code chips for satellite systems. However, other types of orthogonal functions can be employed as desired.
  • Typical CDMA spread-spectrum communication systems contemplate the use of coherent modulation and demodulation for forward link user terminal communications.
  • a "pilot" carrier signal (hereinafter referred to as a "pilot signal”) is used as a coherent phase reference for forward links. That is, a pilot signal, which contains no data modulation, is transmitted by a gateway throughout a region of coverage.
  • a single pilot signal is typically transmitted by each gateway for each beam used for each frequency used, that is, CDMA channel.
  • Pilot signals are used by user terminals to obtain initial system synchronization and timing, frequency, and phase tracking of other signals transmitted by the gateway. Phase information obtained from tracking a pilot signal carrier is used as a carrier phase reference for coherent demodulation of other system signals or traffic signals. Many traffic signals can share a common pilot signal as a phase reference, providing for a less costly and more efficient phase tracking mechanism.
  • the gateway can convey information to that particular user terminal using a signal known as a paging signal. For example, when a call has been placed to a particular mobile phone, the gateway alerts the mobile phone by means of a paging signal.
  • Paging signals are also used to distribute traffic channel assignments, access channel assignments, and certain system overhead information.
  • Satellite signals tend to arrive at sufficiently steep angles so as to avoid many obstructions, mostly buildings, that create multipath signals in terrestrial cellular systems.
  • the user terminals are susceptible to a problem or variety of multipath signals known as specular reflection.
  • Specular reflection occurs when a component of a received signal is scattered from a surface, such as the ground, at an angle equal to the incident angle of the received signal.
  • the characteristics of the reflected component are a function of the incident angle and the electrical properties, roughness, and homogeneity of the impinging surface. Specular reflection occurs a significant amount of the time for many satellite systems.
  • the scattered signals are directed into receivers or receive antennas positioned just above ground level.
  • the specular component can add with the direct signal component to cause significant degradation in the signal level. Due to phase variations between the direct and specular signal components, they can destructively or constructively interfere with each other. This can result in a large oscillation in the signal level or energy, as a user terminal moves or as the satellite changes elevation angle relative to the receiver antenna (as in low earth orbiting satellite systems). In addition, the signal level may also fall below a required level for adequate reception or modulation. In the case of pilot signals, they may not function properly as phase references, also preventing proper signal reception or demodulation. In the case of paging signals, necessary information may not be imparted to allow a user terminal to detect incoming calls or to select proper access channels.
  • a typical satellite signal receive antenna exhibits gain which decreases or "rolls off in value as the elevation angle for received signals approaches zero and goes negative, or below the local horizon for the antenna. Specular radiation is reflected by the ground, or other smooth surface, and enters or is intercepted by the antenna at negative elevation, and, therefore, lower gain being applied.
  • the direct signal strength dominates and little or no degradation is observed. This is generally the situation for direct signals received at higher elevation angles. They are arriving in a higher gain region for the antenna while the specular component arrives in the negative gain region. However, antenna gain typically decreases slowly with lower elevation. Therefore, direct and specular signals received at a lower elevation experience similar gain. In this situation, the specular radiation is closer to the direct signal in strength and causes greater interference and signal degradation. That is, interference from specular radiation tends to be more significant for lower elevation angles. What is needed is a way to mitigate the effects of specular reflection, and maintain or improve communication signal reception, especially for satellite communication systems.
  • the present invention is a system and method for using multiple antennas in a satellite communication system receiver to mitigate the effects of specular reflection.
  • the system includes a first antenna for receiving a satellite communication signal along first direct and specular propagation paths; a second antenna, displaced from the first antenna by a predetermined distance, for receiving the satellite communication signal along second direct and specular propagation paths; and combiner or means for combining the signals received by the first and second antennas so as to maximize the signal-to- noise ratio of the resultant combined signal.
  • the means for combining can be a digital maximal ratio combiner that weights each signal based on its individual signal-to-noise ratio prior to combining with the other signal.
  • the present invention can be extended to use more than two receive antennas, as would be apparent to one skilled in the relevant art.
  • the received signals are reduced to digital baseband signals prior to combining.
  • the received signals are first combined at either RF or IF frequency.
  • a time delay is introduced into one of the signals prior to this initial combining.
  • a rake receiver is used to distinguish the signals received by the first and second antennas at baseband, based on the time delay imposed.
  • the baseband digital signals are then combined so as to maximize the signal-to-noise ratio.
  • One advantage of the present invention is that it permits the signal- to-noise ratio of a received signal to be increased, in the absence of multipath signals.
  • Another advantage of the present invention is that it permits mitigation of path blockages and multipath fading for vehicle-mounted receivers.
  • FIG. 1 depicts a typical satellite communication system
  • FIGS. 2a and 2b depicts the general geometric relationship between the direct and specular components of a forward link satellite communication signal
  • FIG. 3 depicts a plot for normalized signal-to-noise ratio (SNR), measured in dB, versus elevation angle ⁇ , measured in degrees, for a receiver using a single antenna;
  • FIG. 4a and 4b depicts the geometric relationships of FIGS. 2a and 2b for a two-antenna assembly;
  • FIG. 5 depicts a circuit block diagram of a user terminal receiver suitable for implementing one embodiment of the present invention
  • FIG. 6 presents a plot of normalized SNR versus elevation angle for the embodiment of FIG. 5;
  • FIG. 7 depicts a circuit block diagram of a receiver suitable for implementing an alternative embodiment of the present invention
  • FIG. 8 presents a plot of normalized SNR versus elevation angle for an alternative embodiment of the present invention
  • FIG. 9 depicts a circuit block diagram of a receiver suitable for implementing another alternative embodiment of the present invention.
  • the present invention is an apparatus and method for using multiple antennas in a satellite communication system receiver to mitigate the effects of specular reflection.
  • the preferred embodiment of the invention is discussed in detail below. While specific steps, configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other steps, configurations and arrangements can be used without departing from the spirit and scope of the present invention.
  • the present invention will be described in five parts. First, a typical satellite communication system is described. Second, the characteristics of specular reflection are explained. Third, a digital combining solution is presented. Fourth, an analog combining solution is presented. Finally, other applications of the present invention are described.
  • FIG. 1 An exemplary wireless communication system 100 using satellites and gateways or base stations is depicted in FIG. 1.
  • communication system 100 is a CDMA spread spectrum satellite communication system, but this is not required by the present invention.
  • Communication system 100 comprises one or more gateways 102 (102A, 102B), satellites 104 (104A, 104B), and user terminals 106 (106A, 106B, 106C).
  • User terminals 106 each have or comprise a wireless communication device such as, but not limited to, a wireless telephone, although data transfer devices (e.g., portable computers, personal data assistants, modems) are also contemplated.
  • User terminals 106 are generally of three types: portable user terminals 106A, which are typically hand-held; mobile user terminals 106B, which are typically mounted in vehicles; and fixed user terminals 106C which are typically mounted in or on permanent structures.
  • User terminals are also sometimes referred to as subscriber units, mobile stations, or simply "users” or “subscribers” in some communication systems, depending on preference.
  • Gateways 102 communicate with user terminals 106 through satellites 104 (104A and/or 104B).
  • satellites 104 104A and/or 104B
  • multiple satellites are employed traversing different orbital planes such as in, but not limited to, Low Earth Orbit (LEO) or Medium Earth Orbit (MEO).
  • LEO Low Earth Orbit
  • MEO Medium Earth Orbit
  • Terrestrial base stations 108 also referred to as cell-sites or -stations
  • Terrestrial base stations 108 could be used in some systems to communicate directly with user terminals 106.
  • base stations (108) and satellites /gateways are components of separate communication systems, referred to as being terrestrial and satellite based, although this is not necessary.
  • the total number of base stations, gateways, and satellites in such systems depend on desired system capacity and other factors well understood in the art.
  • Gateways and base stations may also be connected to one or more system controllers which provide them with system-wide control or information, and can be connected to a public switched telephone network (PSTN).
  • PSTN public switched telephone network
  • the forward link (that is, the communication link originating at satellite 104 and terminating at a user terminal 106) typically experiences fading that is characterized as Rician.
  • the received signal consists of a direct component summed with a multiply-reflected component having Rayleigh fading characteristics.
  • the power ratio between the direct and reflected components is typically on the order of 6 to 10 dB, depending upon the characteristics of the user terminal antennae and the environment surrounding the user terminal.
  • Significant degradation in the received signals and a resulting decrease in a user terminal receiver performance is caused by destructive interference between such multipath signals.
  • specular reflection is a multipath component reflected from the ground.
  • the general geometric relationship between the direct and specular components of a forward link satellite communication signal are depicted in FIG. 2 (2a and 2b). The relative angles of incidence and reflection are exaggerated in size within FIG. 2 for purposes of illustrating the nature of signal interaction and the problem being addressed.
  • a portable user terminal 106A is equipped with an antenna 220
  • a mobile user terminal 106B is equipped with antenna 220.
  • Antenna 220 both 2a and 2b receives a direct signal component 202A along a direct propagation path from satellite 104A.
  • Antenna 220 also receives a specular signal component 202B reflected from a large, relatively smooth (at the frequencies of interest), planar object 204 such as the surface of the Earth, location or area 206.
  • Satellite 104A is at an elevation angle ⁇ . Because signals being received by user terminals in such a system originate at such great distances from the antenna, direct signal component 202A and a direct component 202C to reflection spot 206 are nearly parallel. That is the two direct components are separated by an extremely small offset or angle. The resulting incident and reflected angles for component 202C and specular component 202B are both approximately ⁇ . That is, the direct and specular signal components are nearly parallel.
  • Interference between direct and specular components of the communication signal can cause significant degradation.
  • degradation can exceed a signal loss value of 6 dB.
  • signal loss value 6 dB.
  • FIG. 3 depicts such a plot for normalized signal-to-noise ratio (SNR), measured in dB, versus elevation angle ⁇ , measured in degrees.
  • the plot depicts two curves: E_direct and E_total.
  • the E_direct curve depicted as a solid line, represents the magnitude of the electric field of the direct component 202A of the forward link communication signal at antenna 220.
  • the E_total curve depicted as a dash-dot line, represents the magnitude of the total electric field, including direct and specular components, at antenna 220.
  • the SNR degradation caused by the specular component at low elevation angles is significant.
  • FIGS. 4a and 4b depict the geometric relationships of FIGS. 2a and 2b, respectively, but using a two-element antenna assembly or system.
  • the single antennas 220 of user terminals 106A and 106B have been replaced by an antennas having two elements, 420A and 420B.
  • Element 420 A is at a height h' above the ground 204
  • antenna 420B is at a height h above the ground 204.
  • Antenna 420A receives a direct signal component 402A and specular component 402B of the forward link communication signal originating at satellite 104A as signal 402C, which relfects at spot 206'.
  • Antenna 420B receives a direct component 202A and a specular component 202B of the forward link communication signal originating at satellite 104A.
  • the incident and reflected angles of specular components 202B and 402B (which are substantially parallel) arriving from satellite 104A are approximately ⁇ .
  • antennas 420A and 420B are shown as two elements within the same antenna structure, other configurations are possible without departing from the spirit and scope of the present invention.
  • the antennas can be mounted on two spaced apart separate supports or masts, as long as the desired vertical height relationship is maintained.
  • the specular components can be characterized using horizontal and vertical components with different reflection coefficients.
  • the incident electric vector E is perpendicular to the plane of incidence and the reflection coefficient h is defined as the ratio of reflected to incident electric fields, or:
  • phase factor in the specular term causes E_total to vary as a function of ⁇ . Because this variation has the shape of cos(Wzsin ⁇ ), the number of oscillations in E_total decreases as the elevation angle increases.
  • the total received electric field can be expressed as:
  • the predetermined elevation angle ⁇ c is selected according to various factors known in the relevant arts. In a preferred embodiment, the predetermined elevation angle ⁇ c is approximately 15°. IV. Digital Combining Solution
  • the signal received by each antenna is converted to a digital baseband signal before combining.
  • a circuit block diagram of a user terminal receiver 500 suitable for implementing this embodiment of the invention is depicted in FIG. 5.
  • receiver 500 includes two antennas 420A and 420B for receiving communication signals from one or more satellites 104 (104A, 104B), and preferably uses a separate receiver chain for each antenna.
  • Receiver system 500 can include more than two antennas and receiver chains, as would be apparent to one skilled in the relevant art.
  • Receiver 500 also includes a digital maximal ratio combiner 520 for combining the digital signals produced by each receiver chain to produce a combined output signal 530.
  • Output signal 530 is a digital data signal, which can be transferred to vocoders and other known circuits or devices for further processing, as would be apparent to one skilled in the relevant art.
  • Digital maximal ratio combiner 520 weights each digital signal based on its SNR, prior to combining signals so as to maximize the SNR of output signal 530.
  • Each receiver chain includes a low noise amplifier (LNA) 504, a mixer
  • Mixer 506 combines the amplified signal produced by LNA 504 with a local oscillator signal to downconvert the received signal from RF to IF frequencies.
  • Analog receiver 508 includes a downconverter to reduce the frequency of the IF signal to baseband.
  • Analog receiver 508 also includes an analog-to-digital converter to convert the analog baseband signal to a digital signal.
  • Digital receiver 510 despreads and demodulates the digital signal, as necessary, and provides error correction and other known signal processing operations.
  • the output of digital receiver 510 is a digital data signal.
  • the digital data signals produced by digital receivers 510 are then coherently combined by digital maximal ratio combiner 520 so as to maximize the signal-to-noise ratio of composite output signal 530.
  • the E_single curve represented by the dotted line in FIG. 6, represents the magnitude of the total received electric field for a single-antenna case, and corresponds to the E_total curve of FIG. 3.
  • the E_combined curve represented by a solid line in FIG. 6, represents the magnitude of the electric field for the digitally combined solution.
  • the digital combining solution results in a significant SNR gain, not only at the predetermined elevation angle of 15°, but also over the entire range of elevation angles.
  • the signals received by antennas 420 are initially combined prior to do wncon verting, so only one receiver chain is needed.
  • a time delay is imposed on one of the received signals prior to initial combining so that the received signals can be distinguished by a rake receiver.
  • the two digital data signals produced by the rake receiver are then combined by a digital maximal ratio combiner, as in the digital combining solution.
  • FIG. 7 depicts a circuit block diagram of a receiver 700 suitable for implementing this embodiment.
  • Receiver 700 includes a delay unit 712, a combiner 714, a searcher receiver 716, digital receivers 510 and a digital maximal ratio combiner 520.
  • Searcher receiver 716 and digital receivers 510 form a rake receiver, such as that disclosed in commonly owned U.S. Patent No. 5,109,390 entitled “Diversity Receiver In A CDMA Cellular Telephone System,” issued April 28, 1992, the disclosure of which is incorporated herein by reference.
  • Delay unit 712 imposes a time delay on the signal received by antenna 420B so that the signals received by antennas 420A and 420B can be distinguished by the rake receiver.
  • the magnitude of the time delay is greater than one chip time.
  • Combiner 714 combines the two received signals, in a manner that would be apparent to one skilled in the relevant art.
  • Mixer 506 downconverts the combined signal, as described above.
  • Analog receiver 508 downconverts the IF signal to a digital baseband signal, also as described above.
  • Searcher receiver 716 distinguishes the signals received by the two antennas based on the time delay and passes each signal to a different digital receiver 510.
  • Digital receivers 510 despread and demodulate the received signals, and the like, as described above.
  • the digital data signals produced by digital receivers 510 are then coherently combined by digital maximal ratio combiner 520 so as to maximize the signal-to-noise ratio of composite output signal 530.
  • E_single represents the magnitude of the total received electric field for a single-antenna case, and corresponds to the E_total curve of FIG. 3.
  • the E_combined curve represented by a solid line in FIG. 6, represents the magnitude of the electric field for the analog combining solution of the present invention. As is apparent from the plot, the analog combining solution also results in SNR gains.
  • the received signals can be delayed and combined after downconverting, as shown in FIG. 9.
  • other implementations are possible without departing from the spirit and scope of the present invention.
  • the present invention is not limited to mitigation of the effects of specular reflection. Embodiments of the present invention are also well suited to at least two alternative applications, which are described below.
  • the present invention is used to mitigate path blockages and multipath fading for vehicle-mounted user terminals, such as mobile user terminal 106B. Portable and mobile user terminals sometimes encounter path blockage due to structures and foliage nearby. These blockages become time-varying when the user terminal is in motion. Similarly, there may be situations in which multipath signals are generated from structures or foliage.
  • receive antennas are positioned on the vehicle such that the shadowed area due to small or thin obstructions does not encompass all antennas simultaneously. Similarly, the likelihood of destructive multipath interference at all of the antennas simultaneously is less than the likelihood of destructive multipath interference at a single antenna.
  • the digital combining solution of the present invention is used to improve signal-to-noise ratios (SNR) for non- multipath signals in an environment without multipath interference. Even in the absence of multipath signals, receiver performance can be improved using multiple antennas and digital combining. Referring again to FIG. 5, if the signals received by antennas 420 A and 420B are the same signal, the SNR of output signal 530 is twice that of the single-antenna case. This principle can be extended to larger numbers of antenna elements, as would be apparent to one skilled in the relevant arts.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Radio Relay Systems (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)

Abstract

On décrit un appareil et un procédé permettant d'utiliser plusieurs antennes réceptrices (420A, 420B) dans un récepteur (500, 600) d'un système (100) de communication par satellite pour atténuer les effets de la réflexion spéculaire (202B, 402B) d'un signal reçu (202A, 402A). Le système comprend des première et deuxième antennes (420A, 420B) destinées à recevoir un signal de communication par satellite le long de première et deuxième voies de propagation directe (202A, 402A) et de voies de propagation spéculaire (202B, 402B) respectivement et un combineur (520) de rapport maximal numérique qui combine les signaux reçus par les première et deuxième antennes (202A, 202B, 402A, 402B) de manière à augmenter au maximum le rapport signal-sur-bruit du signal combiné résultant.
EP98954928A 1997-09-29 1998-09-25 Utilisation de plusieurs antennes pour limiter la reflexion speculaire Withdrawn EP1020042A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US939325 1986-12-08
US93932597A 1997-09-29 1997-09-29
PCT/US1998/020076 WO1999017466A1 (fr) 1997-09-29 1998-09-25 Utilisation de plusieurs antennes pour limiter la reflexion speculaire

Publications (1)

Publication Number Publication Date
EP1020042A1 true EP1020042A1 (fr) 2000-07-19

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EP (1) EP1020042A1 (fr)
JP (1) JP2001518736A (fr)
KR (1) KR20010030790A (fr)
CN (1) CN1115800C (fr)
AU (1) AU1185299A (fr)
CA (1) CA2303540A1 (fr)
WO (1) WO1999017466A1 (fr)

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Publication number Priority date Publication date Assignee Title
JP2001024555A (ja) 1999-07-02 2001-01-26 Nec Mobile Commun Ltd Ｃｄｍａ通信装置および送信電力制御方法
GR1006628B (el) * 2009-01-28 2009-12-11 Αριστοτελειο Πανεπιστημιο Θεσσαλονικης-Ειδικος Λογαριασμος Αξιοποιησης Κονδυλιων Ερευνας Μεθοδος και συστημα συνδυασμου σηματων με απουσια εκτιμησης κερδους καναλιων, για εφαρμογη σε δεκτες ασυρματων τηλεπικοινωνιακων συστηματων

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GB2050118A (en) * 1979-04-30 1980-12-31 Post Office Improvements in or relating to space diversity receiving systems
JPS57159138A (en) * 1981-03-27 1982-10-01 Kokusai Denshin Denwa Co Ltd <Kdd> Electromagnetic wave reception system
IT1197781B (it) * 1986-07-18 1988-12-06 Gte Telecom Spa Sistema irradiante a diversita' angolare per radiocollegamenti a diffusione troposferica
JP2663478B2 (ja) * 1988-02-09 1997-10-15 日本電気株式会社 スペースダイバーシテイ受信方式
US5109390A (en) * 1989-11-07 1992-04-28 Qualcomm Incorporated Diversity receiver in a cdma cellular telephone system
JP2652264B2 (ja) * 1990-07-19 1997-09-10 国際電信電話株式会社 妨害波除去方式及び送受信装置
JPH09505715A (ja) * 1994-09-09 1997-06-03 モトローラ・インコーポレーテッド 無線機のアンテナ構成
KR19990076867A (ko) * 1995-12-28 1999-10-25 밀러 럿셀 비 휴대형 무선전화기에 안테나 다이버시티를 제공하는 장치 및방법
JPH10247869A (ja) * 1997-03-04 1998-09-14 Nec Corp ダイバーシティ回路

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WO1999017466A9 (fr) 1999-06-24
JP2001518736A (ja) 2001-10-16
CN1281603A (zh) 2001-01-24
WO1999017466A1 (fr) 1999-04-08
AU1185299A (en) 1999-04-23
KR20010030790A (ko) 2001-04-16
CA2303540A1 (fr) 1999-04-08
CN1115800C (zh) 2003-07-23

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