Introduction to Microservice Architecture Using SpringBoot - Part 1

1] Capacity of flat and frequency selective channels

Capacity of frequency-selective fading channels obtained by breaking up wideband channel into sub bands (similar to multicarrier).This section we focus on a frequency-selective channel with multiple inputs and multiple outputs (MIMO), i.e., the transmitter and the receiver have multiple antennas.

2] MONOPOLE ANTENNA

A monopole antenna is a type of dipole antenna formed by replacing one half of the dipole antenna with the ground plane at a right angle to the remaining half. If the ground plane is large enough, the monopole behaves exactly like a dipole because its reflection in the ground plane forms the missing half of the dipole.

Compact size printed monopole antennas are important for the wireless applications due to its advantages of easy fabrication, omnidirectional radiation and wide operation bandwidth.

3] Planar Inverted-F Antenna (PIFA)

A planar inverted F-type antenna (PIFA is a uniquely engineered antenna design that includes a built-in ground plane and resists detuning when placed near surfaces, such as metal.
PIFA is mostly designed for dual band frequencies as it is capable of covering wide range of wireless services .The antenna is resonant at a quarter-wavelength (thus reducing the required space needed on the phone)

4] What are base station antennas?

A base station antenna is a fundamental component in a wireless communication network. These antennas are base station mounted on towers to provide cellular connectivity to users. These antennas are used to cover a single frequency band or multiple frequency bands.

5] What is an array of antennas used for?

An antenna array is used to increase overall gain, provide diversity reception, cancel out interference, maneuver the array in a particular direction, gage the direction of arrival of incoming signals, and to maximize the Signal to Interference plus Noise Ratio (SINR).

6] What are the types of array antennas?

The three types of phased array antennas are 

1) linear array

 2) planar array,

 3) frequency scanning array.

 7. What is frequency selective channel?

Frequency selective channels are characterized by time varying nature of the channel. For simulating a frequency selective channel, it is mandatory to have N > 1. In contrast, if N-1, it simulates a zero-mean fading channel where all the multipath signals arrive at the receiver at the same time. When we receive radio signal, the different spectral components fluctuates in unequal manner then this type of fading of signal occurs in case of frequency selective channel.

8. What is the difference between frequency selective channel and frequency flat fading channel?

Frequency Selective Channel: When we receive radio signal, the different spectral components fluctuate in unequal manner then this type of fading of signal occurs in case of frequency selective channel.

Frequency Flat Fading Channel:

When we receive radio signals in which all spectral components fluctuate in the same proportions simultaneously. This type of fading of signal occurs in case of frequency flat fading channel.

9. What are mobile terminal antennas?

The antenna element works mainly as a coupling element and matching circuit, whereas the mobile terminal chassis is the main antenna!! At 1800 MHz, the power radiated by the antenna element is larger, about 50%. The relative bandwidth of a mobile terminal antenna is strongly dependent on the chassis dimensions. The mobile terminal antenna comprises an antenna body and a feed point, wherein the antenna body is arranged inside a rear shell body of a mobile terminal through injection moulding, and the feed point is arranged on the inner surface of the rear shell body. By the adoption of the technical scheme that the antenna body is arranged inside the rear shell body of the mobile terminal through injection moulding, the utility model can enlarge the effective space of antenna designing, thereby remarkably improving the radiation performance of the antenna.

10. What is meant by monopole antenna?

A monopole antenna is half of a dipole antenna on top of a conducting ground plane. The most common type is a quarter-wave monopole where the antenna is approximately 1/4 of wavelength of radio waves. The radiation pattern is limited to above the ground plane of the antenna. The monopole is often used as a resonant antenna; the rod functions as an open resonator for radio waves, oscillating with standing waves of voltage and current along its length. Therefore the length of the antenna is determined by the wavelength of the radio waves it is used with.

11. What is PIFA in antenna?

Planar inverted F antenna (PIFA) is mainly fit for mobile devices. PIFA is mostly designed for dual band frequencies as it is capable of covering wide range of wireless services. This in turn helps in making it acceptable for designing mobile devices. The PIFA is commonly used in mobile communications since it has low manufacturing cost, smaller than the patch antenna size, and a relatively simple structure. In addition it also has reduced backward radiation towards user's head. However, the patch antenna has better polarization purity. The Planar Inverted-F antenna (PIFA) is increasingly used in the mobile phone market.

The antenna is resonant at a quarter-wavelength (thus reducing the required space needed on the phone), and also typically has good SAR properties. This antenna resembles an inverted F, which explains the PIFA name. The Planar Inverted-F Antenna is popular because it has a low profile and an omnidirectional pattern. The PIFA is resonant at a quarter-wavelength due to the shorting pin at the end.

 12. What is the difference between a monopole and dipole antenna?

In essence, the difference between a monopole and dipole antenna, is that a dipole antenna uses an additionally radiator to generate a synthetic ground plane between the symmetric radiator elements, where a monopole antenna requires a physical ground plane. For a dipole antenna, the radiator elements are connected 180 degrees out-of-phase to each other, such as with the inner and outer conductor of a coaxial cable. For a monopole antenna, the reference plane of the transmission line connection, outer conductor of a coaxial cable, is the ground plane of the monopole. Both monopole and dipole antennas exhibit similar radiation patterns and performance, except that monopole antennas are not symmetric vertically. Dipoles tend to be more common. The size and design constraints of requiring a ground plane for monopole antennas is often restrictive and the radiation pattern of the monopole depends on the orientation of the ground plane. Dipole antennas, however, have a vertically symmetric radiation pattern, and can relatively easily be oriented in the direction of optimum reception/transmission.

13. What are base station antennas. What are array antennas used for?

A base station antenna is a fundamental component in a wireless communication network. These antennas are base station mounted on towers to provide cellular connectivity to users. These antennas are used to cover a single frequency band or multiple frequency bands. Multi-band base station antennas often have multiple antennas inside a single redone - in this case each antenna has a separate port, which can be connected to different base stations or to different sections of a single base station.

Base stations are typically mounted above the ground with the height varying according to the surrounding. They are the main communication point for one or more wireless mobile client devices. A Base station can consist of one or more RF antennas that transmit and/or receive radio signals. These antennas are used to cover a single frequency band or multiple frequency bands.

Applications of array antennas include satellite communications, wireless communications, radar communications, and in the astronomical study. Arrays can be described by their radiation patterns and the types of elements in the system.

14. What are the application of PIFA in antenna?

Inverted-F antennae are widely used in compact hand- held wireless devices where space is at a premium. This includes mobile phones and tablet computers using wireless transmissions such as GSM, Bluetooth, and Wi- Fi. The planar inverted-F antenna is the most frequently used internal antenna in mobile phone designs.

These antennae are also of use for vehicle telematics. Vehicle manufacturers like to use antennae that follow the contours of the vehicle for style and aerodynamic reasons. Multiband PIFAS can be used to combine the antennae feeds for mobile phone, satellite navigation, and car radio.These antennas have been used for telemetry applications at military test ranges, including those supporting Inter-Range Instrumentation Group standards.

An R-shaped dual-band PIFA has been proposed for use on military vehicles. The bands to be covered are 225 MHz and 450 MHz. These frequencies are in the same ratio as the mobile phone GSM bands at 900 MHz and 1.8 GHz so the design could be used for this application as well if the dimensions were scaled down to suit.

 15. How do signals propagate?

In wireless media, signals propagate using three principles, which are reflection, scattering, and diffraction.

1. Reflection occurs when the signal encounters a large solid surface, whose size is much larger than the wavelength of the signal, e.g., a solid wall.

2. Diffraction occurs when the signal encounters an edge or a corner, whose size is larger than the wavelength of the signal, e.g., an edge of a wall.

3. Scattering occurs when the signal encounters small objects of size smaller than the wavelength of the signal.

One consequence of multipath propagation is that multiple copies of a signal propagation along multiple different paths, arrive at any point at different times. So the signal received at a point is not only affected by the inherent noise, distortion, attenuation, and dispersion in the channel but also the interaction of signals propagated along multiple paths.