AM Broadcast Research Articles

Tagcaster: Activating Wireless Voice of Electronic Toll Collection Systems With Zero Start-Up Cost

This work enhances the machine-to-human communication between electronic toll collection (ETC) systems and drivers by providing an AM broadcast service to deployed ETC systems. This study is the first to show that ultra-high radio frequency identification signals can be received by an AM radio receiver due to the presence of the nonlinearity effect in the AM receiver. Such a phenomenon allows the development of a previously infeasible cross-technology and cross-frequency communication, called Tagcaster, which converts an ETC reader to an AM station for broadcasting short messages (e.g., charged-fees and traffic forecast) to drivers at tollbooths. The key innovation in this work is the engineering of Tagcaster over off-the-shelf ETC systems using shadow carrier and baseband whitening without the need for hardware nor firmware changes. This feature allows zero-cost rapid deployment in the existing ETC infrastructure. Two prototypes of Tagcaster are designed, implemented, and evaluated over four general and five vehicle-mounted AM receivers (e.g., Toyota, Audi, and Jetta). Experiments reveal that Tagcaster can provide good-quality (PESQ>2) and stable AM broadcasting service with a 30 m coverage range. Tagcaster remarkably improves user experience at ETC stations, and two-thirds of volunteer drivers rate it with a score of 4+ out of 5.

Medium and Short Wave RF Energy Harvester for Powering Wireless Sensor Networks.

Internet of Things (IoT) is an emerging platform in which every day physical objects provided with unique identifiers are connected to the Internet without requiring human interaction. The possibilities of such a connected world enables new forms of automation to make our lives easier and safer. Evidently, in order to keep billions of these communicating devices powered long-term, a self-sustainable operation is a key point for realization of such a complex network. In this sense, energy-harvesting technologies combined with low power consumption ICs eliminate the need for batteries, removing an obstacle to the success of the IoT. In this work, a Radio Frequency (RF) energy harvester tuned at AM broadcast has been developed for low consumption power devices. The AM signals from ambient are detected via a high-performance antenna-free LC circuit with an efficiency of 3.2%. To maximize energy scavenging, the RF-DC conversion stage is based on a full-wave Cockcroft–Walton voltage multiplier (CWVM) with efficiency up to 90%. System performance is evaluated by rating the maximum power delivered into the load via its output impedance, which is around 62 μW, although power level seems to be low, it is able to power up low consumption devices such as Leds, portable calculators and weather monitoring stations.

The Growing Visual Impact of Wireless Antennas in the Urban Landscape: Strategies for Coexistence

A few decades ago, antennas were almost unnoticed in the urban and suburban landscape, except for home television receive antennas. At that time, such areas had a few AM, FM, and television broadcast antennas that were sometimes collocated (although less so in the United States) and served wide areas. The low-capacity land mobile radio systems that existed then also used antennas sited on relatively few high towers or building sites, covering large areas but with little total capacity compared to today’s cellular systems.

SDR-WBFM Receiver as an alternative to replace equipment in FM extended

A presidential decree in Brazil authorizing the migration of AM broadcast to FM. To accommodate these stations, the FM band will receive the frequencies of the channels 5 and 6 of analog TV, which became known as “FM extended”. One of the barriers found in migration is the acquisition of equipment by the users, as the current equipment does not have the expected range in FM extended. To mitigate this problem, the implementation of an FM receiver using the Software Defined Radio (SDR) for its flexibility is proposed. The receiver was developed in GNU Radio environment, with a simple programming was possible to create a low-cost receiver and can serve as an alternative to users for receiving the new band.

MPPSK/AM复合调制系统优化方案

本文给出一种兼容AM广播的MPPSK/AM复合调制系统，为了提升数字信号的解调性能，需要增加MPPSK调制中的K值。而这同时也增加了数字信号与音频信号的频谱混叠，所以本文通过在发送端添加双带阻滤波器，使数字信号不占用音频信号的频段从而提升音频信号解调性能。并且根据贝叶斯公式得出的概率信息表格作为信道解码的软信息进行软判决译码进一步提升数字信号解调性能。 This paper presents a MPPSK/AM Hybrid Modulation System which is compatible with the existing AM broadcast. While it causes the aliasing of digital signal and audio signal spectrum to increase the K value of MPPSK for the improvement of digital signal demodulation performance, thus double band-stop filter is added in the sender, making the digital signal not take up the audio signal frequency band to increase the audio signal demodulation performance. And soft decision decoding based on information table from Bayesian probability formula is obtained as soft information for channel decoder to further enhance the digital signal demodulation performance.

Ionospheric electron density profile estimation using commercial AM broadcast signals

A new method for estimating the bottom electron density profile by using commercial AM broadcast signals as non-cooperative signals is presented in this paper. Without requiring any dedicated transmitters, the required input data are the measured elevation angles of signals transmitted from the known locations of broadcast stations. The input data are inverted for the QPS model parameters depicting the electron density profile of the signal’s reflection area by using a probabilistic inversion technique. This method has been validated on synthesized data and used with the real data provided by an HF direction-finding system situated near the city of Wuhan. The estimated parameters obtained by the proposed method have been compared with vertical ionosonde data and have been used to locate the Shijiazhuang broadcast station. The simulation and experimental results indicate that the proposed ionospheric sounding method is feasible for obtaining useful electron density profiles.

Detection of traveling ionospheric disturbances by medium‐frequency Doppler sounding using AM radio transmissions

AbstractNighttime traveling ionosphere disturbances (TIDs) propagating in the lower F region of the ionosphere have been detected by measuring time variations in the Doppler shifts of commercial AM radio broadcast signals. Three receivers, components of the Intercepted Signals for Ionospheric Science (ISIS) Array software radio instrumentation network in the northeastern United States, recorded signals from two radio stations during 11 nights in March–April, 2012. By combining these measurements, TIDs were detected as approximately 40min periodic variations in the frequencies of the received signals resulting from Doppler shifts produced by the ionosphere. The variations had amplitudes of up to a few tenths of a hertz and were correlated across the array. For one study interval, 0000–0400 UT on 13 April 2012, simultaneous GPS total electron content, Digisonde®, and Super Dual‐Auroral Radar Network coherent backscatter radar measurements confirmed the detection of TIDs with the same characteristics. Besides TIDs, the receiver network often detected large (nearly 1 Hz) upward (downward) Doppler shifts of the AM broadcast signals at the dawn (dusk) terminator. These results demonstrate that AM radio signals can be used for detection and monitoring of nighttime TIDs and related effects.

Modeling and Performance prediction of Eureka-147 OFDM based DAB system

The new digital radio system DAB (Digital Audio Broadcasting), developed within the Eureka 147 project is a very innovative and universal multimedia broadcast system that has the potential to replace existing AM and FM audio broadcast services in many parts of the world in the near future. DAB employs coded OFDM technology that enables it for mobile reception and makes receivers highly robust against channel multipath fading effect. In this paper, we have analyzed the bit error rate (BER) performance of DAB system conforming to the parameters established by the ETSI (EN 300 401) using frequency interleaving and Forward Error Correction (FEC) in different transmission channels. The results shows DAB to be suitable radio broadcasting technology for high performance in mobile environment.

Practical papers, articles and application notes: Interaction of an AM broadcast transmitter with a large crane posing health hazards: A real-world event analysis

During the construction phase of a wind power plant in Turkey, an electromagnetic interaction was observed with a large crane and an AM broadcast transmitter. The interaction resulted in large current levels which posed health hazards to the workers. Initial grounding measures were not sufficient. In order to quantify the current levels, to assess the degree of the hazard and to find a practical remedy to the problem, the phenomenon is modeled and different cases with different worker configurations are analyzed. The analysis results emphasize the importance of the insulation and local grounding.

Estimation of Uncertainties in Electric Field Exposure From Medium-Frequency AM Broadcast Transmitters

International guidelines for limiting exposure to electromagnetic fields set out basic restrictions and reference levels to protect human health. To ensure compliance with these guidelines, standard measurement procedures must be used, and assessments of the uncertainties in the measurements must be reported. Nevertheless, neither the exposure restrictions nor the technical assessment standards specify how the measurement and computation of the uncertainties should be considered. This paper analyzes the following two sources of uncertainties that are not often considered in the assessment of exposure to electromagnetic fields: 1) repeatability and 2) spatial interpolation. For this purpose, electric field measurements were made in an area in which three medium-wave radio broadcasting transmitters are located. Systematic random sampling was performed with a spectrum analyzer and a monopole-type antenna, and geostatistical techniques were used to construct contour maps of the electromagnetic radiation and its associated uncertainties. The results suggest that, in handling uncertainties in assessments of human exposure to electromagnetic fields based on spatial interpolation from point measurements, based on medium-frequency amplitude modulation broadcast transmitters, the additive approach (i.e., the uncertainty is added to the results of the assessment before the exposure level is compared to the relevant limit) is the most appropriate.

Harvest the Ambient AM Broadcast Radio Energy for Wireless Sensors

A wireless sensor system powered by AM broadcast energy harvesting is presented. A 10 meter length horizontal antenna and a resonant circuit were combined to harvest the electromagnetic energy, in the frequency range from 531 kHz to 1602 kHz. In a typical urban environment, an output voltage up to 14 V and a power of 82 μ W were obtained by a single stage doubler rectifier. A seven-day measurement is implemented to verify the stability of the energy. The output characteristics, multi stage doubler rectifier and implementation of sensor prototype are also discussed. The results indicate that the energy carried by AM radio is sufficient to drive a basic wireless sensor operating in sleep/wakeup mode. The stability and continuity of the harvested energy is superior to solar energy.

Radio Frequency Burns in the Power System Workplace

Power system workers may be simultaneously in contact with a metallic object and exposed to power frequency electromagnetic fields or radio-frequency (RF) electromagnetic field from nearby sources such as AM broadcast antennas. Under these conditions, the person may experience either a shock or an intense heating of the tissue near the point of contact (i.e., an RF burn). Here, 50/60 Hz shocks and RF burns are compared and models developed to predict RF current at the point of contact with a metallic object and the resulting heating (and burning) of the tissue. Electric field levels at which RF burns can occur are often significantly less than the maximum permissible exposure in the most widely used RF safety standards. The conditions for which these burns occur are common and are discussed in detail.

A Precision, Low-Cost GPS-Based Transmitter Synchronization Scheme for Improved AM Reception

This paper describes a highly accurate carrier-frequency synchronization scheme for actively, automatically locking multiple, remotely located AM broadcast transmitters to a common frequency/timing reference source such as GPS. The extremely tight frequency lock (to ~1 part in 109 or better) permits the effective elimination of audible and even sub-audible beats between the local (desired) station's carrier signal and the distant stations' carriers, usually received via skywave propagation during the evening and nighttime hours. These carrier-beat components cause annoying modulations of the desired station's audio at the receiver and concurrent distortion of the audio modulation from the distant station(s) and often cause listeners to ldquotune outrdquo due to the low reception quality. Significant reduction or elimination of the beats and related effects will greatly enlarge the effective (interference-limited) listening area of the desired station (from 4 to 10 times as indicated in our tests) and simultaneously reduce the corresponding interference of the local transmitter to the distant stations as well. In addition, AM stereo (CQUAM) reception will be particularly improved by minimizing the phase shifts induced by co-channel interfering signals; hybrid digital (HD) signals will also benefit via reduction in beats from analog signals. The automatic frequency-control hardware described is inexpensive ($1000-$2000), requires no periodic recalibration, has essentially zero long-term drift, and could employ alternate wide-area frequency references of suitable accuracy, including broadcasts from WWVB, LORAN-C, and equivalent sources. The basic configuration of the GPS-disciplined oscillator which solves this problem is extremely simple. The main oscillator is a conventional high-stability quartz-crystal type. To counter long- term drifts, the oscillator is slightly adjusted to track a high-precision source of standard frequency obtained from a specialized GPS receiver (or other source), usually at 10.000 MHz. This very stable local reference frequency is then used as a clock for a standard digitally implemented frequency synthesizer, which is programmed to generate the specific carrier frequency desired. The stability of the disciplining source, typically ~1 part in 109 to 1011, is thus transferred to the final AM transmitter carrier output frequency.

Data Transmission on AM Broadcast with Acoustic OFDM

Data transmission via audio link on AM radio system is shown to be achievable by using Acoustic OFDM. We employ Acoustic OFDM to embed data onto audio contents that are then broadcast as AM radio signals. We tuned the parameters, and performed experiments. Text data as URL can be delivered to mobile phone through existing MF AM radio system and radios.

Software Reception of AM & FM Broadcast Using Frequency Domain Samples

Digital signal processing (DSP) has been widely used because it can realize variety of functions by change of software. Now, it is possible to handle practical analog or digital signal by DSP. This paper proposes a new method for reception of AM & FM broadcast signal using FFT/IFFT. Also, demultiplexing of demodulated FM signal is included. First, input signal is sampled and truncated. Then, truncated samples are transferred to frequency domain samples by FFT. Demodulation and demultiplexing are performed using both frequency domain and time domain samples. In order to process continuous signal by truncated samples, use of overlap and save method is assumed. Matlab Simulink diagram of demodulation and demultiplexing by the proposed method is also presented.

Book of the Month: Malingering and Illness Deception

Book of the Month: Malingering and Illness Deception

Malingering and Illness Deception

Malingering and Illness Deception

Acoustics of a broadcast center

A broadcast system in Mexico City had to change facilities in order to concentrate in a single site all related broadcast stations and production studios in order to facilitate its normal operation. This led to a design which included the acoustic noise isolation and the interior acoustics of every studio and control room, together with the audio interconection, the electricity layout, the air conditioning system, the office building, etc. This paper presents the acoustics profile of the center, including final results of the construction as they were measured on completion of the installation. The complex has seven AM and FM broadcast stations, plus seven production studios for news, commercials and radio-novels plus an audio master control room, and everything was completed within four months.

Class-D amplification combined with switched-mode power conditioning-the route to long battery life

Class-D amplification is the acknowledged means by which amplifier power demand can be reduced in battery-powered audio products. However, it is also well known that the switching action of the class-D amplifier is a potential source of electromagnetic interference and therefore designers of audio consumer products are naturally concerned that the adoption of this form of amplification will jeopardise the ability of their product to comply with EMC regulations. We show that when properly screened, class-D amplifiers can be used within a few inches of a sensitive AM broadcast receiver. Furthermore, the cost of the screening can be defrayed by including switched-mode power management circuits within the screened environment. This reduces the power consumption, allows the use of a single cell as a power source, and reduces the total ownership cost and the size and the weight of the product.

Evaluation of the Potential for Power Line Noise to Degrade Real Time Differential GPS Messages Broadcast at 283.5-325 kHz

The new nationwide differential global positioning system network uses the 283.5-325 kHz hand to broadcast differential GPS (DOPS) correction messages. Concem has been expressed that power line corona and gap discharge noise could degrade the performance of DGPS receivers using this band. Previous work on power lines and the AM broadcast band identified corona and gap discharges as broadband noise sources in the LFIMF bands. The potential to locally degrade performance of DGPS receivers relatively close to some power facilities appears possible for certain situations. The extent of any DGPS interference problem will depend on receiver/antenna design and placement, signal strength, power line design, weather conditions, and characteristics of the noise source. Also affecting DGPS receiver performance can be the presence of any nearby non-power line RF noise sources such as electronic devices or equipment internal to the user's vehicle.