The Quest for Extraterrestrial Intelligence

The constant depictions of contact with extraterrestrial life and their constant basic presence in science fiction shows the deep human desire for connection and transcendence with other life forms. In reality, continuous efforts on the search for aliens are being made by renown not-for-profit research organization such as the Search for Extraterrestrial Intelligence (SETI) since 1984. Over the years, plenty of detected signals were dismissed as noise from transmitters on Earth or orbiting satellites but one – the “Wow!” signal. However, artificial signals from extraterrestrial sources could be the key to detecting extraterrestrial intelligence. Apart from passively searching, some are doing active SETI, or known as METI (Messaging Extraterrestrial Intelligence), where humans create and transmit interstellar messages to aliens instead of waiting for theirs. Substantial effort in many areas – awareness, time, technological advancement, techniques – would be necessary to increase the probability of locating outer space intelligence.

Basic Electromagnetic Theory

Electromagnetic theory covers the basic principles of electromagnetism. This chapter explores relationships between electric and magnetic fields. The chapter describes the behaviour of electromagnetic wave. The four sets of Maxwell's equations which underpin the principles of electromagnetism are briefly explained. An illustration on wave polarization and propagation is presented. The author describes the classification of waves according to their wavelengths (i.e. the electromagnetic spectrum).

Active Galactic Nuclei and Pulsars

With the discovery of radio emission of extraterrestrial origin, it had opened a new and broader window in the electromagnetic spectrum to observe the sky. Two of the common sources of radio emissions are active galactic nuclei (AGN) and pulsars. AGN are very luminous at radio wavelength and are powered by the accretion disk surrounding supermassive black holes at the center. AGN are useful as an alternative standard ruler to determine cosmological parameters. Pulsars, on the other hand, is a type of neutron star that is highly magnetized and rotates at enormous speed. This cosmic lighthouse produces a very precise pulsation period that can be used as cosmic clock.

Microstrip Patch Antenna

This chapter elaborates in detail on the microstrip patch antenna, which is widely utilized in the receivers of radio telescopes, as well as in the wireless communication industry today. Several models have been developed to analyze and design the patch antennas. The three most common ones are the transmission line model, the cavity model, and the Method of Moments model. Apart from this, the important parameters used in characterizing the patch antenna are also covered, which are its gain, efficiency, directivity, radiation pattern, return loss, bandwidth, and polarization. This is followed by the introduction of the radiation regions, which are basically classified as the Fresnel region and the Fraunhofer region. Finally, the dual-frequency microstrip patch antenna is introduced. Three popular approaches adopted for the design are orthogonal-mode polarization, multi-layer patching, and reactive loading.

Electromagnetic Wave Propagation

Electromagnetic wave propagation is an invisible phenomenon that cannot be detected by the human senses. To understand wave propagation, one must first learn what wave propagation is and the basic principles that affect wave propagation. This chapter introduces the atmospheric windows which allow electromagnetic radiation from bands to penetrate Earth. Helmholtz equations, i.e. the equations which govern wave propagation, and the properties of waves (such as propagation constant and characteristic impedance) are then briefly explained. When waves encounter different media during its propagation, they may be reflected, refracted, or diffracted. These phenomena are also covered. The last part of this chapter concisely explains the terminologies commonly used to describe electromagnetic radiation.

Introduction to Radio Astronomy and Radio Telescopes

Radio astronomy studies the physics and chemistry of cosmic sources and cosmic phenomena at the radio wave spectrum. Radio telescopes are built to detect radiation within this spectrum. This chapter provides a historical walkthrough on the development of radio astronomy and radio telescopes. Significant discoveries and works pioneered by scientists in radio astronomy are highlighted. Nobel laureates who have led to groundbreaking contributions in this field are listed.

Practice of Meteor Burst Communication

A lot of research and experiments on meteor burst communication described in the previous chapter have been done by research institutions, educational institutions, and amateur radio operators. The contents of research and experiments are roughly classified into two categories. One is to investigate the frequency and duration of meteor bursts themselves, and the other is to study data transmission using meteor bursts. This chapter introduces some experiments on meteor burst communications conducted in Japan and the method of QSO by meteor scatter communications conducted by amateur radio operators.

Physical Optics

Physical optics (PO) is one of the fundamental and powerful high-frequency theories for electromagnetic scattering and radiation. The total field of a source (antenna) which radiates in the presence of a perfectly conducting surface may be expressed as a superposition of the incident and the scattered fields. The current fields which exist everywhere are chosen in PO to denote the electric and magnetic fields of the source, i.e., they exist as if the scatterer was “absent”; this is unlike the geometrical optics (GO) incident field, which exists in the presence of the surface of the scatterer. The scattered fields in this case can be expressed in terms of the radiation integrals over the actual currents induced on the surface of the scatterer. These currents also radiate the scattered fields in the absence of the scatterer. This chapter shows the fundamental PO formulation and calculated results, and some topics which improve the conventional PO to the extended PO such as “physical theory of diffraction (PTD)” and “PO with transition current (PTD-TC)”.

Fundamentals of Meteor Burst Communication

When space dust rushes into the atmosphere, oxygen and nitrogen are ionized by frictional heat. Along the dust flight path, a very long cylindrical plasma tube, 10 meters in diameter and several kilometers long is formed. The long plasma tube is called “meteor burst” and is a good reflector for radio waves in the VHF band. Non-line-of-sight communication performed using this reflector is called “meteor burst communication”. In this chapter, the basics of meteor burst communication and its applications are outlined.

Active Integrated Antenna

This chapter discusses the active integrated antenna (AIA), which is the integration of an antenna with an active circuitry that acts as a radiating element as well as to perform additional functions simultaneously. The designs of AIA can be generalized into three different classifications, the amplifier type, the oscillator type, and the frequency conversion type. An AIA is classified as the amplifier type when its active device functions as an amplifier. Correspondingly, an AIA is classified as the oscillator type when its active device offers the function of an oscillator while the frequency conversion type of AIA integrates an active device with a passive antenna element for the purpose of frequency translation.