Hedley J. Hansen

Wireless RF communication in biomedical applications

This paper focuses on wireless transcutaneous RF communication in biomedical applications. It discusses current technology, restrictions and applications and also illustrates possible future developments. It focuses on the application in biotelemetry where the system consists of a transmitter and a receiver with a transmission link in between. The transmitted information can either be a biopotential or a nonelectric value like arterial pressure, respiration, body temperature or pH value. In this paper the use of radio-frequency (RF) communication and identification for those applications is described. Basically, radio-frequency identification or RFID is a technology that is analogous to the working principle of magnetic barcode systems. Unlike magnetic barcodes, passive RFID can be used in extreme climatic conditions—also the tags do not need to be within close proximity of the reader. Our proposed solution is to exploit an exciting new development in making circuits on polymers without the need for battery power. This solution exploits the principle of a surface acoustic wave (SAW) device on a polymer substrate. The SAW device is a set of interdigitated conducting fingers on the polymer substrate. If an appropriate RF signal is sent to the device, the fingers act as microantennas that pick up the signal, and this energy is then converted into acoustic waves that travel across the surface of the polymer substrate. Being a flexible polymer, the acoustic waves cause stresses that can either contract or stretch the material. In our case we mainly focus on an RF controllable microvalve that could ultimately be used for fertility control.

Rotman lens for mm-wavelengths

The 77 GHz band has been reserved for intelligent cruise control in luxury cars and some public transport services in America and the United Kingdom. The Rotman lens offers a cheap and compact means to extend the single beam systems generally used, to fully functional beam staring arrangements. Rotman lenses have been built for microwave frequencies with limited success. The flexibility of microstrip transmission lines and the advent of fast accurate simulation packages allow practical Rotman lenses to be designed at mm-wavelengths. This paper discusses the limitations of the conventional design approach and predicts the performance of a new Rotman lens designed at 77 GHz.

Analysis of millimetre-wave polarization diverse multiple-input multiple-output capacity

Millimetre-waves offer the possibility of wide bandwidth and consequently high data rate for wireless communications. For both uni- and dual-polarized systems, signals sent over a link may suffer severe degradation due to antenna misalignment. Orientation robustness may be enhanced by the use of mutual orthogonality in three dimensions. Multiple-input multiple-output polarization diversity offers a way of improving signal reception without the limitations associated with spatial diversity. Scattering effects often assist propagation through multipath. However, high path loss at millimetre-wave frequencies may limit any reception enhancement through scattering. We show that the inclusion of a third orthogonal dipole provides orientation robustness in this setting, as well as in a rich scattering environment, by means of a Rician fading channel model covering all orientations for a millimetre-wave, tri-orthogonal, half-wave dipole transmitter and receiver employing polarization diversity. Our simulation extends the analysis into three dimensions, fully exploiting individual sub-channel paths. In both the presence and absence of multipath effects, capacity is observed to be higher than that of a dual-polarized system over the majority of a field of view.

Trade-Offs for Wireless Transcutaneous RF Communication in Biotelemetric Applications

The application of biotelemetry in the case of a RF controllable microvalve is discussed. Biotelemetry implies the contactless measurement of different electrical and nonelectrical parameters measured on human or animal subjects. A biotelemetry system consists of a transmitter and a receiver with a transmission link in-between. Transmitted information can be a biopotential or a nonelectric value like arterial pressure, respiration, body temperature or pH value. Transducers convert nonelectrical values into electrical signals. Radio frequency (RF) telemetry allows a patient greater mobility. Above all, the application of wireless communication becomes more and more popular in microinvasive surgery. Battery powered implants are most commonly used, but batteries must be changed after a period of time. To avoid this, wireless transcutaneous radio frequency (RF) communication is proposed for the powering and control of medical implants.

Microstrip-based Rotman lens for millimeter-wave sensing operations

Rotman lenses offer a compact, rugged and reliable means of forming multi-beam staring array sensing arrangements. The successful implementation of Rotman devices, that operate at mm-wave frequencies, is important to a wide range of applications ranging from covert military operations and collision avoidance in cars and boats in poor weather, to landing aids for aircraft. This paper discusses the development of a Ka-band microstrip-based Rotman lens that is to be used in collision avoidance and other military related roles.

Tri‐orthogonal polarization diversity for 5G networks

Millimetre-waves offer the possibility of wide bandwidth and consequently high-data rate for wireless communications. For both uni-polarised and dual-polarised systems, signals sent over a link may suffer severe degradation because of antenna misalignment. Orientation robustness may be enhanced by the use of mutual orthogonality in three dimensions. Multiple-input multiple-output polarisation diversity offers a way of improving signal reception without the limitations associated with spatial diversity. Scattering effects often assist propagation through multipath. However, high-path loss is often considered to limit millimetre-wave propagation, thereby reducing any reception enhancement through scattering. We show that the inclusion of a third orthogonal dipole at a frequency of commercial interest provides antenna orientation robustness in this setting, as well as improved performance in a rich scattering environment, by means of a Ricean fading channel model. Copyright

Remote Gas Detection Using Millimeter-Wave Spectroscopy for Counter Bio-Terrorism

The mm-wave (10-110 GHz) frequency band contains the fundamental rotational resonance frequencies of many molecular gases composed of carbon, nitrogen, oxygen and sulfur. The high specificity of the rotational spectra to organic molecules affords mm-wave spectroscopy having potential use in remotely sensing atmospheric pollutants and the detection of airborne chemicals is gaining importance for arms control treaty verification, intelligence collection and environmental monitoring. This paper considers RF receiver systems for remote chemical detection measurements based on mm-wave spectral line emissions. It discusses the design, performance and operation of specific receiving systems for detecting the presence of ammonia in laboratory based transmit-and-receive experiments.

Monolithic fabrication of Rotman lenses

Rotman lenses have the potential to solve many problems associated with high frequency antenna arrays. Offering compact, rugged and reliable means of forming muli-beam, staring array sensing arrangements, these lenses may prove very useful if robust solutions to some important problems are to be found. This paper presents the performance of a Rotman lens design and discusses the challenges associated with the design of these lenses.

Surface refractivity gradient data for radio system design

Reliable information about the cumulative distribution of surface refractivity gradient is often required in the design of radio systems. Strong negative gradients, or super-refraction, may lead to interference between terrestrial stations, both terrestrial links and satellite earth stations. Predicted positive or sub-refractive gradients are taken into account in determining the minimum antenna heights, to ensure terrestrial links achieve their required availability. This paper reviews sources of refractivity gradient data, and considers how refractivity gradient at a point may relate to an effective value over a terrestrial path.

Frequency-scanned mm-wave sensors for imaging applications

Frequency-scanned slotted-waveguide and microstrip travelling-wave arrays, for detecting mm-wave (10-110GHz)thermal emissions via acousto-optic Bragg cell processors, are being considered in defence and civilian security-related remote sensing applications. The optical processing of RF signals is significant because it promises affordable RF operating staring multi-beam arrangements. Optical processing circumvents the need to assemble expensive miniaturised RF receiver elements in phased array configurations by allowing RF information to be processed using optical-video and CCD techniques. This paper considers the design and fabrication of microstrip travelling-wave based sensors for Ka (~35 GHz) -band operation.