A radio altimeter antenna for a planetary probe

The design of a 400 MHz directional antenna for a space vehicle is presented. The design utilizes the spacecraft itself as an integral part of the antenna. The antenna has a gain of 4 dB over a dipole, a front to back ratio of 8 dB, and a - 6 dB beam angle of34deg. Design equations and experimental data are presented.     

The monopole slot as a two-port diversity antenna for UHF land-mobile radio systems

Urban land-mobile communication systems designed to operate over the upper portion of the UHF band are very susceptible to frequent wide signal variations. Deep fades arise due to the presence of many obstructions in the propagation path between the transmitter and receiver. One way to combat the effects of Rayleigh fading due to multipath propagation is to provide a diversity combiner in the mobile receiving system with two signals, each containing the same information, which fade independently of one another. Such a system can virtually eliminate deep fades from the receiver output. Described herein is a method of obtaining two diversity branches, with independent signals if so desired, from a single two-port antenna which is both well matched to the transponder and efficient over the land-mobile frequency band from 820- 890 MHz. A directive pattern is associated with each port. When operating with a direct wave, signal gain over an omnidirectional antenna is therefore possible.     

Optimum antenna separation for space diversity in l.o.s. radio links over flat ground

In line-of-sight radio links over flat terrain or water, a general formula to calculate the antenna separation for space diversity is not appropriate because of the risk of simultaneous fading. A method for determining such a separation is shown and its implementation is described exactly and approximately.     

PARAN antenna for use where horizontal and vertical space islimited

A PARAN (perimeter current antenna) antenna which was constructed, tested, and licensed at radio station KAPS in Mount Vernon, Washington, USA, is described. A PARAN antenna is intended for the broadcaster whose site is severely limited in height and ground area. Both current distribution versus height measurements and full field proof-of-performance measurements were made to prove the antenna's efficiency. The results show that a PARAN antenna can produce a radiation field better than 282 mV/m/1 kw at 1 km (175 mV/m/1 kw at 1 mi). Bandwidth evaluation measurements and radiation hazard measurements are discussed     

Cochannel interference rejection in a mobile radio space diversity system

Diversity is often used in radio systems to alleviate the problem of fading. It is shown here that the use of diversity in a mobile radio system also will result in better utilization of the frequency spectrum. In a system which reuses channels in physically separated areas, probability distributions of signal-to-cochannel interference ratios in 1-, 2-, and 4-branch diversity systems are developed by Monte Carlo methods. We consider two cases: first, we assume signal strength to be Rayleigh distributed, which is a valid model for reception within a small localized area; second, we take shadow losses into account by assuming a more realistic long-term fading model. The effect of using diversity in a mobile radio system is considerable with either model. Assuming a hexagonal cell pattern of frequency reuse, it is shown that frequencies may be reassigned more often in a diversity system than in a system which does not use diversity. The conclusion, therefore, is that a diversity system utilizes the frequency spectrum more efficiently than an equivalent nondiversity system.     

A circular patch antenna for radio LAN's

A TM₀₂-mode circular patch antenna for the application of radio LANs is reported. An experimental prototype operating at 5.2 GHz is designed and tested. The antenna pattern is omnidirectional in azimuth and has a notch in the normal direction. A 3.3% bandwidth of VSWR ⩽2 and 4.2-dB antenna gain were measured. Experimental results agree well with theoretical predictions     

On-glass automotive diversity antenna and LNA design for S-band satellite digital radio

Selection combining diversity system with antennas mounted on windshield and backlite of a vehicle is proposed for satellite digital audio radio applications. Standalone exterior mount antennas on metallic vehicles perform well for satellite digital audio radio applications, but for composite body vehicles or interior mount antennas, antenna performance becomes a real issue. Proposed on-glass two-antenna diversity is one solution for such applications. The antenna correlation is calculated using the S-parameters of the antennas and found to be very low due to many wavelengths separation between the antennas. Design of low noise amplifier, which has sub 1 dB noise figure and good P1dB due to strong cellular signals, is also detailed. A diversity receiver is described and ride tests are performed to assess the performance of the diversity system in real-time, under weak satellite signal environment which is regarded as the most challenging reception condition.     

Compact wideband omnidirectional UHF antenna for TV white space cognitive radio application

This paper presents design and analysis of a compact wideband omnidirectional antenna for application in TV white space cognitive radio. The proposed antenna mainly consists of a monopole, a pair of parasitic elements, and a brief impedance matching network, all etched on an FR4 substrate. To obtain physical insight, an equivalent circuit is modelled and analysed to reveal the contribution of each part of the antenna to its bandwidth enhancement. Performance of the antenna is evaluated by simulations, and then further validated by experiments. Experimental results show that the antenna has an impedance bandwidth (voltage standing wave ratio less than 2) ranging from 460 MHz to 870 MHz, as well as omnidirectional radiation patterns in H-plane through the whole band.     

Performance comparison of space diversity and equalizationtechniques for indoor radio systems

By means of analytical and numerical methods, we derive the bit error rate (BER) of π/4-DQPSK systems in frequency-selective fading channels. For a theoretical analysis of the system, a simplified two-ray channel model has been used. However, both Rayleigh and lognormal distributions for the ray envelope have been considered. The system performance in the presence of antenna diversity and in combination with a new nonlinear equalizer has been evaluated. In particular, it is seen that in flat fading environments, space diversity may improve the performance by more than 10 dB at a BER=10^-3. However, for channels with a large delay spread, nonlinear intersymbol interference (ISI) is the predominant disturbance, and the performance can only be enhanced by the nonlinear equalizer     

Joint detection with coherent receiver antenna diversity in CDMAmobile radio systems

In code division multiple access (CDMA) mobile radio systems, both intersymbol interference and multiple access interference arise which can be combated by using either elaborate optimum or favorable suboptimum joint detection (JD) techniques. Furthermore, the time variation of the radio channels leads to degradations of the receiver performance. These degradations can be reduced by applying diversity techniques. Using coherent receiver antenna diversity (CRAD) is especially attractive because only the signal processing at the receiver must be modified. In the present paper, the application of CRAD to the more critical uplink of CDMA mobile radio systems with suboptimum JD techniques is investigated for maximal-ratio combining. The authors study six different suboptimum JD techniques based on decorrelating matched filtering, Gauss-Markov estimation, and minimum mean square error estimation with and without decision feedback. These six suboptimum JD techniques which are well-known for single antenna receivers are extended for the application to CRAD. A main concern of the paper is the determining of the SNR performance of the presented JD techniques for CRAD and the achievable average uncoded bit error probabilities for the transmission over rural area, typical urban and bad urban mobile radio channels are determined     

A mobile radio antenna system having a self-diplexing function

A coupled N-element antenna system on a mobile unit for simultaneous transmission and reception is discussed. A diplexer is required when an antenna for transmission and that for reception are installed with mutual coupling between them. An attempt is made to reduce coupling between the transmitting point and the receiving point by a lossless network and coupled antennas. The network is connected between the antenna and the input and output ports. The decoupled antenna is analyzed and theoretical and experimental results, which show the feasibility of the antenna system, are described.     

Experiments on coherent adaptive antenna array diversity forwideband DS-CDMA mobile radio

In wideband direct sequence code division multiple access (W-CDMA), employing an adaptive antenna array is a very promising technique to reduce severe multiple access interference (MAI) from high rate users. A four-antenna pilot symbol-assisted coherent adaptive antenna array diversity (PSA-CAAAD) receiver comprising an adaptive antenna array based on a minimum mean squared error (MMSE) criterion and a RAKE combiner is implemented in preliminary laboratory and field experiments. There are two important design concepts of the PSA-CAAAD receiver. The first is that the adaptive antenna array forms an antenna beam for each resolved propagation path and tracks only slow changes in the directions of arrival (DOAs) and average powers of the desired and interfering user signals. The second is that the RAKE combiner tracks the instantaneous changes in channel conditions and coherently combines the signals of the desired user propagating along the resolved paths to maximize the instantaneous signal-to-interference plus background noise power ratio (SINR). This paper presents, both by laboratory and field experiments, the effectiveness of PSA-CAAAD receiver as a powerful means to reduce severe MAI from high rate users, and that it is more effective than using a space diversity receiver with the same number of antennas in the W-CDMA reverse link     

Performance comparison of antenna diversity and slow frequencyhopping for the TDMA portable radio channel

The authors compare the performance of a TDMA (time-division multiple-access) system plan using two-branch antenna diversity to other TDMA system plans using channel and time slot interleaving and slow frequency hopping/burst error correction (SFH/BC). Results indicate that the system designer can trade off spectral efficiency by using a double-error-correction code with channel interleaving and SFH to make the SFH/BC system perform as well as a system using two-branch antenna diversity. For a system with interleaving and SFH, the number of hopping frequencies required depends on the code used and on the design of the demodulator (i.e. hard versus soft decisions). As long as the code is chosen such that the system can handle the complete failure of one of the hopping frequencies, it can achieve about the same outage probability or speech block dropping rate as a system using antenna diversity. However, this equality is exacted at the price of spectral efficiency. In this instance, the decrease in required signal-to-interference ratio (S/I) is not enough to offset the decrease in the number of available channel sets caused by the wider bandwidth required to transmit the lower rate code. Other coding plans must be evaluated for relative spectral efficiency     

A study of the antenna array configuration of an M-branch diversity combining mobile radio receiver

The theoretical analysis in this paper is based on the assumption that the angles of signal arrival on the mobile receiver are uniformly distributed. From the analysis and experimental studies, we find that if the antenna spacing between two adjacent antennas in a space diversity array is greater than 0.5λ the array configuration does not affect the cumulative distribution curves nor the shapes of the level-crossing-rate (LCR) curves, and only slightly affects the signal level at which the maximum LCR occurs. Hence a three-element array with a triangular shape or a four-element array with a rectangular shape can be considered a good arrangement, provided each side (antenna spacing) is greater than 0.5λ. Two slightly better arrangements than those we just mentioned for improving the signal fading are also proposed for three-branch and four-branch diversity signals, respectively.     

Design of a 74-MHz antenna for radio astronomy

Describes the design and construction of an 8000 m² 74-MHz phased array dedicated to measurement of the solar-wind velocity using the interplanetary scintillation (IPS) technique, and a simple and novel autocalibration system that measures and connects phase and amplitude errors to a level of 1° and 0.2 dB rms. In the IPS technique, intensity fluctuations of compact radio sources caused by plasma turbulence in the solar wind are observed with multiple antennas. The time lag between the antennas is estimated using a cross-correlation analysis. The primary requirement of such a system is sensitivity so that one may observe a large number of compact sources. A secondary requirement is high beam efficiency so that one may observe near the Sun. The scan angle was limited to allow the largest possible array element and thus the simplest feed system. The feed was designed to have independent phase and amplitude control of each element. Although this is not strictly necessary it permits the use of the feed as a phase switched interferometer with which any element can be correlated against any other group of elements. This provides a simple and accurate calibration of the entire array. The antenna was completely prefabricated, the site preparation was minimal, and the installation was quick and accurate. The system is remotely operated. The control information, system diagnostics, and data are transmitted over a leased telephone line. The entire system is powered by storage batteries charged by solar cells. In addition to IFS it has been used extensively for pulsar observations which have similar requirements     

Results on turbo-codes for speech transmission in a joint detectionCDMA mobile radio system with coherent receiver antenna diversity

Turbo-codes which are applicable to speech transmission in digital mobile radio systems are treated. Three turbo-codes of different complexity are presented. The proposed turbo-codes are suitable for the application to speech transmission in the joint detection code-division multiple access (JD-CDMA) mobile radio system with coherent receiver antenna diversity (CRAD) which are described concisely. The performance of the designed turbo-codes in terms of bit and frame error rates are shown in the case of additive white Gaussian noise (AWGN) channels, flat Rayleigh fading channels, and in the uplink of the aforementioned JD-CDMA mobile radio system     

用于认知无线电的自适应可重构天线研究

针对未来无线电系统如软件无线电、认知无线电给天线设计特别是可重构天线设计提出的新挑战,提出了一种基于全波/网络混合的可重构天线仿真分析方法.该方法将可重构天线看作多载天线,采用全波仿真分析无加载的天线阵列,将网络分析法与遗传算法相结合分析任意加载可重构天线的网络特性和辐射方向图,并利用该方法对一种矩形环形可重构天线的频率和方向图可重构能力进行了仿真分析.仿真结果表明,矩形环形可重构天线具有频率可重构和方向图可重构的功能,该特性可以使其应用于未来的认知无线电、智能天线等系统中.     

A notch-wire composite antenna for polarization diversity reception

This paper presents a notch-wire composite antenna for polarization diversity reception in an indoor base-station system. A three-notched disk antenna and a wire antenna are proposed as component antennas for the horizontal and the vertical polarization, respectively. These component antennas are unified as a single composite diversity antenna by mounting the wire antenna on the notched disk. Antenna characteristics are calculated using the method of moments (MoM), with wire grid models and examined in terms of component arrangement, and terminal isolation. It is found that maximum isolation is obtained when the current path of the wire antenna is where the current exciting the H-pol element is cancelled. Consequently, both component antennas may work independently even in the composite form. The quasi-monopole pattern is also confirmed for each polarization     

A planar diversity antenna for handheld PCS devices

A polarization diversity antenna (PDA) is described, and its performance is compared to that of a monopole antenna at frequencies near 900 MHz. Numerical modeling of each antenna, using the finite-difference time-domain (FDTD) technique, incorporates a cellular telephone handset in the vertical orientation, the user's head and hand, and the mobile communications environment. Results indicate that the two modes of the PDA are sufficiently uncorrelated for diversity operation and that, overall, the values of the mean effective gain (MEG), efficiency, and averaged specific absorption rate (SAR) in the head are better for the PDA than for the monopole antenna. However, in terms of the MEG, the PDA is more sensitive than the monopole antenna to the presence of the user's body. For the PDA, most of the power absorbed in the user's body is deposited in the hand, whereas for the monopole antenna, most of the absorbed power is deposited in the head. For both antennas, the MEG depends on the environment (urban or suburban)     

A switched diversity receiving system for mobile radio

A low cost switched diversity receiving system has been developed for use in UHF-FM mobile radio. The input of a single receiver is switched back and forth between two antennas upon command from a signal level sensing logic circuit. The system has been measured on simulated Rayleigh fading channels and has been found to give a significant improvement to both voice and data signals.