COMMUNICATION IN FLIGHT

COMMUNICATION IN FLIGHT
Introduction:
Aircraft communication is a digital data link system for transmission of short messages between aircraft and ground stations via air band radio or satellite. The protocol was designed by ARINC ( Aeronautical Radio, Incorporated) and deployed in 1978, using the Telex format.
Types of communication:
• Verbal
• Non-verbal
• Written
• Written and graphic
• Human- machine and machine-machine
Verbal communication:
It is most common communication in air craft used by cabin-crew , aircraft technicians, pilots and flight attendant to take care and communicate with passengers.
Non-verbal communication:
It is important in every situation. It has two major kinds- body language and physical appearance. There are six type of expressions in it emblems, illustrators, regulators, adapters, affect displays, postures and gestures.
Written communication:
It is one way communication sending checklists and or other information to pilot.
Written and Graphic communication:
It allows the sender to provide clear and specific message to recipient by including graphic displays in the message like flight maps.
Human- machine and machine-machine communication:
It is the communication in which the pilot communicates with machine in the form of command and that message gets transmitted to other machines.
Aviation Communication Issues:
Communication issues and errors can spring up between pilots and co-pilots, pilots and crew, pilot and ATC, and among the ground crew. Major communication issues include:

Information Overload:
The higher the amount of information being transmitted, the larger the chances of an error to occur.

Pronunciation Issues:
For non-English speakers, there is always a huge probability of passing information with unclear pronunciation.

Misunderstanding:
Most errors in aviation communication are as a result of a general misunderstanding. It could be caused from variations in the speech rate, intonation, stresses, sentence structure or pauses of the communication. Misunderstandings can be found in both native and non-English speakers.
Conclusion:
In order to ensure more efficient and saver environment the ICAO (International Civil Aviation Organization)  has adopted ENGLISH as official language of aviation. Those who are not fluent English speaker, must pass an English proficiency test at an operational level to retain or gain their professional license. The test is 1-on-1 interview with examiner where they will engage the pilot in conversations about specific aviation related occurences, as  through a dialogue between the pilot and ATC (Air Training Crops). By doing this we can minimize the issues and we can have safe journey.

Spiral Inductors

Introduction:

In contrast with digital circuits which use mainly active devices, on-chip passive components are necessary and imperative adjuncts to most RF electronics. These components, which include inductors, capacitors, varactors, and resistors, have been known as performance as well as cost limiting elements of radio frequency (RF) integrated circuits. While all of these components can be realized using MOS technology, their specific designs necessitate special consideration due to the requirement of high-quality factor Q at relatively high frequencies. Inductors in particular are critical components in oscillators and other tuned circuits. For low-frequency applications, passive devices can be connected externally, but as the frequency increases, the characteristics of the passive devices would be overwhelmed by parasitic effect. For instance, a voltage-controlled oscillator (VCO) of 10 MHz needs a tank inductance on the order of several µH, whereas at 10 GHz the inductance is around 1 nH. It’s impossible to access such a small inductance externally, since the inductance associated with the package pin and bond wire can exceed 1 nH. As a result, on-chip passive components are commonly used in RF applications.

This blog will focus on the on-chip inductors. Basically, there are three types of on-chip inductors. The most widely used type is the planar spiral inductor, and a square shaped spiral inductor. Although a circular shaped inductor may be more efficient and yield better performance, the shape of inductor is often limited to the availability of fabrication processes. Most processes restrict all spiral angles to be 90°, and a rectangular/square pattern (hereafter called square pattern) is a nature choice, but a polygon spiral inductor can serve as a compromise between the square and circular shaped inductors. Structural parameters such as the outer dimension, number of turns, the distance between the centres of lines (or pitch), and substrate property are all important factors in determining the performance of on-chip inductors.

Concepts and Modelling of Spiral Inductors:

Traditionally, spiral inductors are made in square shape due to its ease of design and support from drawing tools. From the performance point of view, however, the most optimum pattern is a circular spiral because it suffers less resistive and capacitive losses. But the circular inductor is not widely used because only a few commercial layout tools support such a pattern. Hexagonal and octagonal structures are good alternatives, as they resemble closely to the circular structure and are easier to construct and supported by most computer-aided design tools. It has been reported that the series resistance of the octagonal and circular shaped inductors is 10% smaller than that of a square shaped spiral inductor with the same inductance value.

Circuit Equivalent:

This blog will discuss the concepts and formulas for series inductance (LS), resistances (RS and RSi), capacitances (CS, CSi, and COX), and quality factor and substrate loss.

Series Inductance:

In 1946, Grover derived formulas for the inductance of various inductor structures. Greenhouse later applied the formulas to calculate the inductance of a square shaped inductor. He divided the inductor into straight-line segments, and calculated the inductance by summing the self-inductance of the individual segment and mutual inductance between any two parallel segments. The model has the form of

LS = L0 + (M+)–(M−)

where LS is the total series inductance, L0 is the sum of the self inductance of all the straight segments, M+ is the sum of the positive mutual inductances and M- is the sum of the negative mutual inductances. Self inductance L’0 of a particular segment can be expressed as

L’0 is the inductance in nH, l is the length of a segment in cm, w is the width of a segment in cm, and t is the metal thickness in cm. The mutual inductance between any two parallel wires can be calculated using

M = 2lQ'

where M is the mutual inductance in nH and Q’ is the mutual inductance parameter

GMD denotes the geometrical mean distance between the two wires. When two parallel wires are of the same width, GMD is reduced to

d is the pitch of the two wires. Note that the mutual inductance between two segments that are perpendicular to each other is neglected. As the number of segments increases, the calculation complexity is increased notably because it is proportional to (number of segments) ^2. Another drawback of the model is its limitation to only square shaped inductors. The above model could be simplified using an averaged distance for all segments rather than considering the segments individually. Based on this approach, the self and mutual inductances are calculated directly as

where µ0 is the permeability of vacuum, lT is the total inductor length, n is the number of turns, and d’ is the averaged distance of all segments.

Resistance:

Series resistance RS (see Fig. 4(c)) arises from the metal resistivity in the inductor and is closely related to the quality factor. As such, the series resistance is a key issue for inductor modelling. When the inductor operates at high frequencies, the metal line suffers from the skin and proximity effects, and RS becomes a function of frequency [19]. As a first-order approximation, the current density decays exponentially away from the metal-SiO2 interface.

Where ρ is the resistivity of the wire, and t(eff) is given by

t is the physical thickness of the wire, and δ is the skin depth which is a function of the frequency:

where µ is the permeability in H/m and f is the frequency in Hz. The most severe drawback of a frequency-dependent component, such as RS, in a model is that it cannot be directly implemented in a time domain simulator, such as Cadence Spectre. Researchers have proposed to use frequency-independent components to model frequency dependent resistance. Ooi et al replaced RS with a network of 2 R’s and 1 L, where R and L are frequency-independent components, in the inductor equivalent circuit. The total equivalent resistance R(total) of the box is

where R0 is the steady-state series resistance, ω is the radian frequency, P is the turn pitch, t is the inductor thickness, w is the inductor width, σ is the conductivity, N is the total number of turns, and M is the turn number where the field falls to zero. The substrate resistance is given by

where l is total length of all line segments, G(sub) is the conductance per unit area of the substrate.

Capacitance:

There are basically three types of capacitances in an on-chip inductor: the series capacitance CS between metal lines, the oxide capacitance COX associated with the oxide layer, and the coupling capacitance CSi associated with the Si substrate.

where n is the number of overlaps, w is the spiral line width, Csub is the capacitance of the substrate, tox is the oxide thickness underneath the metal, and toxM1-M2 is the oxide thickness between the spiral. An improved method [26], which evaluates the voltage and energy stored in each turn, leads to the equivalent capacitances of Cp and Csub, as shown in Fig. 8. Compared to the model in Fig. 4(c), Cp and Csub in this model are equivalent to CS and the combination of Cox and CSi, respectively,

where Cms represents the capacitance per unit area between the mth metal layer and the substrate, Cmm represents the capacitance per unit length between adjacent metal tracks, Ak is the track area of k th turn and lk is the length of kth turn. The model also implies that CS is a function of the index difference of each adjacent segment pair. This means that the larger the index difference between the two adjacent lines, the higher the capacitance.

Quality Factor and Substrate Loss:

The quality factor Q is an extremely important figure of merit for the inductor at high frequencies. For an inductor, only the energy stored in the magnetic field is of interest, and the quality factor is defined. Basically, it describes how good an inductor can work as an energy-storage element. In the ideal case, inductance is pure energy-storage element (Q approaches infinity), while in reality parasitic resistance and capacitance reduce Q. This is because the parasitic resistance consumes stored energy, and the parasitic capacitance reduces inductivity (the inductor can even become capacitive at high frequencies). Self-resonant frequency fSR marks the point where the inductor turns to capacitive and, obviously, the larger the parasitic capacitance, the lower the fSR.

If the inductor has one terminal grounded, as in typical applications, then the equivalent circuit of the inductor can be reduced to that shown in Fig. 9. From such a model, the quality factor Q of the inductor can be derived

where ω is the radian frequency, LS is the series inductance, RS is the series resistance, RP is the coupling resistance, and CP is the coupling capacitance.

LTE technology

What is LTE?

 In telecommunications, Long-Term Evolution (LTE) is a standard for wireless broadband communication for mobile devices and data terminals, based on the GSM/EDGE and UMTS/HSPA technologies. It increases the capacity and speed using a different radio interface together with core network improvements.LTE, sometimes known as 4G LTE, is a type of 4G technology. Short for "Long Term Evolution", it's slower than "true" 4G, but significantly faster than 3G, which originally had data rates measured in kilobits per second, rather than megabits per second.

LTE Bandwidth:

LTE supports deployment on different frequency bandwidths. The current specification outlines the following bandwidth blocks: 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz, and 20MHz. Frequency bandwidth blocks are essentially the amount of space a network operator dedicates to a network. Depending on the type of LTE being deployed, these bandwidths have slightly different meaning in terms of capacity.. An operator may choose to deploy LTE in a smaller bandwidth and grow it to a larger one as it transitions subscribers off of its legacy networks (GSM, CDMA, etc.).

How LTE works:

LTE uses two different types of air interfaces (radio links), one for downlink (from tower to device), and one for uplink (from device to tower). By using different types of interfaces for the downlink and uplink, LTE utilizes the optimal way to do wireless connections both ways, which makes a better optimized network and better battery life on LTE devices. For the downlink, LTE uses an OFDMA (orthogonal frequency division multiple access) air interface as opposed to the CDMA (code division multiple access) and TDMA (time division multiple access) air interfaces we’ve been using since 1990. What does this mean? OFDMA (unlike CDMA and TDMA) mandates that MIMO (multiple in, multiple out) is used. Having MIMO means that devices have multiple connections to a single cell, which increases the stability of the connection and reduces latency tremendously. It also increases the total throughput of a connection. We’re already seeing the real-world benefits of MIMO on WiFi N routers and network adapters. MIMO is what lets 802.11n WiFi reach speeds of up to 600Mbps, though most advertise up to 300-400Mbps. There is a significant disadvantage though. MIMO works better the further apart the individual carrier antennae are. On smaller phones, the noise caused by the antennae being so close to each other will cause LTE performance to drop. WiMAX also mandates the usage of MIMO since it uses OFDMA as well. HSPA+, which uses W-CDMA (a reworked, improved wideband version of CDMA) for its air interface, can optionally use MIMO, too. For the uplink (from device to tower), LTE uses the DFTS-OFDMA (discrete Fourier transform spread orthogonal frequency division multiple access) scheme of generating a SC-FDMA (single carrier frequency division multiple access) signal. As opposed to regular OFDMA, SC-FDMA is better for uplink because it has a better peak-to-average power ratio over OFDMA for uplink. LTE-enabled devices, in order to conserve battery life, typically don’t have a strong and powerful signal going back to the tower, so a lot of the benefits of normal OFDMA would be lost with a weak signal. Despite the name, SC-FDMA is still a MIMO system. LTE uses a SC-FDMA 1×2 configuration, which means that for every one antenna on the transmitting device, there’s two antennae on the base station for receiving.

LTE Network Architecture: 

The high-level network architecture of LTE is comprised of following three main components:

• The User Equipment (UE).

• The Evolved UMTS Terrestrial Radio Access Network (E-UTRAN).

• The Evolved Packet Core (EPC).

Future of LTE Technology: With 5G generating so much buzz, it is easy to overlook the groundbreaking services being enabled by the evolution of 4G. Between now and 2020, the year when 5G is scheduled to be commercially available, Advanced LTE networks will seed the market for exciting new applications, such as increasingly autonomous cars, real-time gaming, personal cloud services, dense sensor networks and remote health monitoring. Narrowband IoT and Long Term Evolution (LTE) Machine Type Communications, will enable operators to support the deployment of large numbers of battery-powered IoT devices in licensed spectrum. These networks technologies could enable connected devices to operate for 10 years on a 5Wh battery, reducing the need for in-field maintenance and making key IoT applications, such as smart metering, more cost-effective. Over the next four years, LTE Advanced will be a game changer for both mobile operators and their customers

Basics of gyrator

Basics of gyrator
                 A gyrator two port electrical network element proposed in 1948 by Bernard D.H.Tellegan as a hypothetical fifth linear element after resistor ,capacitor,inductor and ideal transformer. It is a non reciprocal ferrite electronic device.It is having a characteristics of passive , linear , lossless and memory less ,time invariant  two port network .A gyrator which is similar to an ideal transformer.It is typically a RF device .

Working of gyrator
It is two port device that has a relative phase shift of 180 degree in forward direction and 0(zero) degree phase shift in reverse direction Hence, it was also known as differential phase shift device .

When the signal is fed into port 1 the output at the port 2 has 180 degree phase shifted .The vice versa is not possible .When the signal is fed into port2 the signal at the port1 is 0(zero) degree phase shifted.A cascade connection of two gyrator is equivalent to an ideal transformer.
It  transform load capacitance into an inductance .At low frequency and low powers ,the behavior of the gyrator can be reproduced by a small opamp circuit .Gyrator circuits are often used in IC's  where it is not possible to include inductor because of space and size limitation .A gyrator which is an example of nonenergic system .It is constructed from the nullors and resistors are also elaborated.
 directional phase shifter, a microwave device. This device creates a half-wave phase change of electromagnetic waves propagating in opposite directions.  The operating principle of gyrators is based on the irreversible properties of magnetized ferrite; these properties cause rotations of polarization plane, phase shift, and so on. The simplest kind of gyrator consists of a circular radio waveguide that contains an appropriately dimensioned, magnetized ferrite rod (magnetized in a magnetic field of a previously determined intensity). A circular waveguide is coupled to a rectangular waveguide by matching transitions.
   When a capacitor is connected at input of gyrator it appears as almost pure inductor at output terminals.

Application of gyrator
• Primary goal is reduced size of circuit by removing inductor.
• It is used in a telephony device that is connected to POTS.
• Parametric equalizer
• Band pass filter (BPF)
• Anywhere in which one can replace inductor to reduce size of circuit
• It is used as a components in various microwave devices such as gates , modulators ,circulators and switches.