900 MHz multipath propagation measurements in four United States cities

Describes multipath power delay profile measurements of 900 MHz mobile radio channels in four US cities. Preliminary data show that for over 98% of the measured locations, RMS delay spreads are less than 12 mu s. In very rare instances, reflections from city skylines and mountains can cause RMS delay spreads which exceed 20 mu s and excess delays which exceed 100 mu s. Such large excess delays have not been previously reported in the literature.<>     

900-MHz mobile radio propagation in the Copenhagen area

A comparative study of 900-MHz, 450-MHz, and 150-MHz mobile radio propagation characteristics performed in Copenhagen, Denmark is described. The three systems were compared with respect to usable coverage area, flutter characteristics, and transmission quality. A statistical method was used for the determination of the coverage area, the limits of which are defined by the contour line corresponding to 20-dB noise quieting at 90 percent of the locations. Flutter patterns were photographically recorded, and simultaneous recordings of voice signals received on the three systems were made on magnetic tape. Concluded is that when corrections are made for differences in transmitter power, antenna gain, receiver sensitivity, etc., and when the propagation losses are assumed to vary with frequency like the free space losses, the coverage areas obtained will be nearly identical. The increased flutter rate at 900 MHz apparently does not affect the transmission noticeably, and it must be generally concluded that the 900-MHz band will provide as good mobile radio performance as any of the lower bands.     

Behaviour of spectrum-conserving RBQPSK digital radio during multipath propagation

Studies indicate that reduced bandwidth quadrature phase-shift-keyed digital radio relay systems (RBQPSK) employing adaptive decision-feedback techniques have good spectrum utilisation efficiency coupled with robustness in the presence of distortion induced by multipath propagation. The letter discusses the practical confirmation of RBQPSK performance during multipath propagation on a 6 GHz, 51 km long test link in East Anglia.     

Measurement and modeling of propagation losses in brick and concrete walls for the 900-MHz band

The prediction of wall losses is a fundamental aspect in the planning of cellular systems. The broad variety of building materials and construction codes makes accurate attenuation prediction very difficult without the support of specific construction data or measurements. In this paper, the attenuation and equivalent electric parameters /spl epsiv/ and /spl sigma/ of brick and doubly reinforced concrete walls are estimated for the 900-MHz band by fitting simple ray tracing models to empirical transmission data. The measurement setup is described, and extensive experimental results justifying the quasioptical modeling are presented.     

Microwave propagation measurements for mobile digital radio application

Measurements over a variety of urban and terrain conditions were made using a spread-spectrum waveform centered at 1370 MHz. Chip rates of 10 and 20 MHz were used, giving high time-delay resolution. The transmitter end of the measurement link was elevated and fixed while the receiver was mobile. A detailed analysis of the multipath structure was made for various terrain conditions. This included distributions of the number and spacing of individual multi-path components as a function of amplitude threshold and also distribution of total delay. Thresholds are referenced to both average signal level and the maximum level in each pulse interval. Some instances of spatial variation of the received signal are also presented.     

A 4.5-mW 900-MHz CMOS receiver for wireless paging

An ultralow-power 900-MHz receiver implemented on a single CMOS chip is intended for use in FLEX wireless paging. The receiver uses an indirect conversion to zero intermediate frequency (IF) to suppress the flicker noise corner in the second mixer to less than 1 kHz. Various techniques for low-power design, most of them unique to CMOS, are presented, with theoretical support and experimental verifications. The receiver, fabricated in a 0.25-μm standard CMOS process, achieves 7.4-dS noise figure at 1.6 kHz with -25-dBm IIP3 on a 1.5 V supply. The voltage-controlled oscillator (VCO) has a phase noise of -98 dBc/Hz at 25 kHz offset. The nominal receiver bias current of 3 mA is higher than the expected 2 mA because of unanticipated losses in coupling capacitors     

A system plan for a 900-MHz portable radio telephone

The system concepts for a high capacity personal radio telephone system are described. Previous systems for mobile radio telephone service have been based on a rigid assignment of frequencies to specific small geographic areas within the total coverage area. This approach has led to conservative geographic frequency reuse constraints and the requirement for accurate location techniques in the system. Through the utilization of the power imbalance that exists in the proposed portable radio telephone system between base and portable unit transmitters these constraints are eliminated. It will be shown how this power imbalance allows the selection of the optimum signal for the portable unit and relaxed requirements on location and reuse of frequencies. The required signal-to-interference ratios must be obtained within a design reliability level over the coverage area. Computer simulation of the frequency reuse plan and the propagation variability over the area indicates the nominal repeat intervals necessary as a function of this reliability level. A reuse plan that obtains the required repeat intervals with a high degree of spectral efficiency, through the combined use of geographic and frequency separation, will be presented. This system called tertiary offset, achieves a significant increase in interference protection by splitting each channel into a group of three channels and utilizing each subgroup in a different pattern of reuse over the area. The improvement due to this plan will be shown.     

DC-coupled IF stage design for a 900-MHz ISM receiver

This paper presents a DC-coupled 900-MHz ISM band RF front-end for a short-range wireless receiver. The front-end, fabricated in a 0.5-/spl mu/m CMOS process, is intended as a test vehicle to verify the proposed DC-coupled topology. In this topology, a low-frequency feedback circuit suppresses the DC offset and low-frequency noise at the mixer output. The DC-coupled topology is compared with traditional AC coupling. We show that there is a tradeoff between bandwidth and midband loss in a fully integrated AC-coupled system. The proposed DC-coupling technique does not impose this tradeoff. The DC-coupled topology was verified via simulation and measurements from the test vehicle.     

A 900-MHz 1-V CMOS frequency synthesizer

A 900-MHz 1-V frequency synthesizer has been fabricated in a standard 0.35-μm CMOS technology. The frequency synthesizer consists of a divide-by-128/129 and 64/65 dual-modulus prescaler, phase-frequency detector, charge pump, and voltage-doubler circuit with an external voltage-controlled oscillator (VCO) and passive loop filter. The on-chip voltage-doubler circuit converts the 1-V supply voltage to the higher voltage which supplies the prescaler internally. In this way, the 900-MHz 1-V frequency synthesizer with an external VCO can be achieved. The measured phase noise is -112.7 dBc/Hz at a 100-kHz offset from the carrier, and the synthesizer dissipates 3.56 mW (not including VCOs) from a single 1-V supply when the switching frequency of the on-chip voltage doubler is 200 kHz and the power efficiency of the voltage doubler is 77.8%. The total chip area occupies 0.73 mm²     

M-Profile ray tracing technique for multipath propagation

A model for the modified refractivity is suggested and used in a new and simple ray tracing approach for multipath propagation. The technique is then used to study the variations in ray path parameters for different path geometries.     

A compact PIFA suitable for dual-frequency 900/1800-MHz operation

Planar inverted F antennas (PIFA) have been proposed as possible candidates for mobile telephone handsets. We describe the design of a compact PIFA suitable for operation at 900 MHz. In addition, we provide modifications to this design that allow it to operate in dual-frequency bands at 300 and 1800 MHz. Finite-difference time-domain (FDTD) and experimental results are provided     

A 900-MHz/1.8-GHz CMOS transmitter for dual-band applications

The design of a radio-frequency transmitter that can operate in two bands while employing a minimal number of external components entails many challenges at both the architecture and the circuit levels. This paper describes the design of a 900-MHz/1.8-GHz transmitter implemented in CMOS technology for dual-band applications. Configured as a two-step architecture, the circuit generates the first upconverted signal in quadrature form and subsequently performs single-sideband modulation to produce the output in two bands. Fabricated in a 0.6-μm digital CMOS technology, the transmitter exhibits unwanted spurs 40 dB below the carrier while drawing 75 mW from a 3-V supply     

An integrated silicon bipolar receiver subsystem for 900-MHz ISMband applications

A wide-band dual conversion receiver subsystem is presented which is suitable for 900-MHz portable wireless applications including cordless telephony. The circuit features 118 dB of dynamic range and is operable from 6.5 V down through 2.7 V while consuming 26 mA. The receiver utilizes the MOSAIC V radio frequency (RF) silicon bipolar process and features an LNA, two mixers, two oscillators, second LO amplifier, dual modulus prescaler, LF amplifier, RSSI, coilless demodulator, and power down control     

Potential GPRS 900/180-MHz and WCDMA 1900-MHz interference to medical devices

This study compared the potential for interference to medical devices from radio frequency (RF) fields radiated by GSM 900/1800-MHz, general packet radio service (GPRS) 900/1800-MHz, and wideband code division multiple access (WCDMA) 1900-MHz handsets. The study used a balanced half-wave dipole antenna, which was energized with a signal at the standard power level for each technology, and then brought towards the medical device while noting the distance at which interference became apparent. Additional testing was performed with signals that comply with the requirements of the international immunity standard to RF fields, IEC 61000-4-3. The testing provides a sense of the overall interference impact that GPRS and WCDMA (frequency division duplex) may have, relative to current mobile technologies, and to the internationally recognized standard for radiated RF immunity. Ten medical devices were tested: two pulse oximeters, a blood pressure monitor, a patient monitor, a humidifier, three models of cardiac defibrillator, and two models of infusion pump. Our conclusion from this and a related study on consumer devices is that WCDMA handsets are unlikely to be a significant interference threat to medical electronics at typical separation distances.     

A 2.7-V 900-MHz CMOS LNA and mixer

A CMOS low-noise amplifier (LNA) and a mixer for RF front-end applications are described. A current reuse technique is described that increases amplifier transconductance for the LNA and mixer without increasing power dissipation, compared to standard topologies. At 900 MHz, the LNA minimum noise figure (NF) is 1.9 dB, input third-order intercept point (IIP3) is -3.2 dBm and forward gain is 15.6 dB. With a 1-GHz local oscillator (LO) and a 900-MHz RF input, the mixer minimum double sideband noise figure (DSB NF) is 5.8 dB, IIP3 is -4.1 dBm, and power conversion gain is 8.8 dB. The LNA and mixer, respectively, consume 20 mW and 7 mW from a 2.7 V power supply. The active areas of the LNA and mixer are 0.7 mm×0.4 mm and 0.7 mm×0.2 mm, respectively. The prototypes were fabricated in a 0.5-μm CMOS process     

Strange attractors in multipath propagation

The estimation of the correlation dimension of multipath propagation signals in an indoor environment, indicates the presence of a strange attractor of dimension between four and five, suggesting deterministic chaos. The authors stress that although the profiles they examined show saturation in all three experimental configurations, indicating that they would be able to describe their data with a set of at most five nonlinear differential equations, investigation in other propagation situations is needed. An example of the detection of the presence of strange attractors in radar clutter is presented     

A 900-MHz fully integrated SOI power amplifier for single-chipwireless transceiver applications

This paper presents a silicon-on-insulator (SOI) fully integrated RF power amplifier for single-chip wireless transceiver applications. The integrated power amplifier (IPA) operates at 900 MHz, and is designed and fabricated using a 1.5-μm SOI LDMOS/CMOS/BJT technology. This technology is suitable for the complete integration of the front-end circuits with the baseband circuits for low-cost low-power high-volume production of single-chip transceivers. The IPA is a two-stage Class E power amplifier. It is fabricated along with the on-chip input and output matching networks. Thus, no external components are needed. At 900 MHz and with a 5-V supply, the power amplifier delivers 23-dBm output power to a 50-Ω load with 16-dB gain and 49% power-added efficiency     

Characterization of multipath parameters for line-of-sight microwave propagation

Ray equations are derived for microwave multipath propagation in a two-layer atmosphere, and the connection between the different solutions is demonstrated by numerical examples. Analytical expressions are developed to characterize the condition for multiple rays, the variation in angle-of-arrival (AOA), and the delay spread. The results suggest that more than three rays will be rare in practice and that the three-ray model (obtained from the zero-order rays defined in the paper) may provide a good representation of selective fading on microwave links.     

A 900-MHz RF front-end with integrated discrete-time filtering

Discrete-time analog filters, rather than off-chip components, have been used to perform frequency selection and down conversion in the integrated front-end for a 900-MHz RF receiver. The first stage of frequency down conversion is implemented with a subsampling switched-capacitor sample-and-hold circuit clocked at 78 MHz. Subsequent stages of discrete-time filtering are realized using switched-capacitor biquadratic filters. An experimental prototype of the front-end had been integrated in a 0.6-μm BiCMOS technology. The circuit provides a system gain of 36 dB and 32 dB suppression of interfering channels over a 40 MHz bandwidth. Referred to the system input, the third-order intercept-point is -16 dBm, and the spot input-referred noise is -82 dBm over a 30 kHz bandwidth. The experimental circuit dissipates 90 mW from a 3.3-V supply and occupies an active area of 1.9×1.9 mm²      

A 1.5-V 900-MHz monolithic CMOS fast-switching frequencysynthesizer for wireless applications

A new architecture for phase-locked loop frequency synthesizers which employs a switchable-capacitor array to tune the output frequency and a dual-path loop filter operating in the capacitance domain is proposed. It provides many advantages, including simplified analog circuitry, low supply voltage, low power consumption, small chip area, fast frequency switching, and high immunity of substrate noise. Implemented in a standard 0.5-μm CMOS process, a fully integrated fractional-N synthesizer prototype with a third-order sigma-delta modulator is designed for 1.5 V and consumes 30 mW. The total chip area is, 0.9 × 1.1 mm². The settling time is less than 100 μs and the phase noise is -118 dBc/Hz at 600-kHz offset