ZigBee Network Topologies and Routing & Super-Heterodyne Receiver - Research Paper Example

Electronic Communication Technology Part A –Analogue communication Explanation of the Principles of the Super-Heterodyne Receiver The principle under which the Super-Heterodyne Receiver operates is the frequency mixing. The amalgamation of the frequencies allows for the translation of a received signal to a fixed midway frequency. The intermediate frequency is more expediently processed than the initial radio carrier frequency. The Super-Heterodyne Receiver is applied in all modern receivers due to its efficiency in reception and integration of signals (Nassar, p. 339). In the Super-Heterodyne Receiver, the arriving signal is mixed with an interior oscillator to generate sum and difference frequency constituents. The intermediate frequency (IF), constitutes the lower frequency difference component. The fixed tuned amplifier stages forms a distinct barrier that distinguishes the intermediate frequency from other components on the printed board. The local oscillator’s tuning is mechanically ganged to tuning of the radio frequency (RF). The mechanical ganging of the signal circuit allows for the equity of the difference midway frequency and the fixed value. Circuit Description In the case of AM broadband radios, a suitable antenna is fundamental for effective reception of signals. A varicap diode or a variable resistor can be utilized in the tuning circuit. The tuning of the circuits in the RF stage has to trail the local oscillator tuning. The tuned circuit at this level bars the frequencies that are far eliminated from the targeted response frequency (Nassar, p. 328). Mixer stage The local oscillator (LO) produces a sine wave into the circuit that mixes with the signals. The mixer output is provided by; y(t) = r(t) cos 2πfit = Ac( 1+ms(t)) cos 2πfct cos 2πfit = Ac/2(1+ ms(t)) [cos 2π(fc + f1)t +(f1 – fc)t] The super – heterodyne receiver uses High- Side Injection (HIS) of the oscillator that is provided by ft = fc + fIF for Low Side Injection (LSI) and fI = fc - fIF . When the receiver is tuned to the frequency of a different incoming signal, the frequency of the local oscillator (LO) is also changed automatically in order to satisfy the equation fI = fc - fIF in the High- Side Injection. Therefore, the output of the mixer is given by; y(t) = Ac/2(1+ ms(t)) [cos 2πfIFt + cos 2π (2f2 + fIF)t] Image Response The other signal at fim = fc + 2fIF referred bto as the image response, can be down converted to the IF in case the RF bandpass filter does not attain good image response. The output of the RF amplifier can be expressed as z(t) = AcI (1+ m1s1(t)) cos 2πfct + Ac2 (1+ m2s2(t)) cos 2π (fc + 2f IF)t IF amplifier The amplifier provides most of the needed gain and selectivity. The amplifier has a bandwidth equivalent to B with an output filter signal of Ac/2(1+ ms(t)) cos2π f IFt The Demodulator The required signal z(t) is centered at f IF, at the output of the IF filter. The output of the modulator is u(t) = Ac/2(1+ ms(t)). It should be noted that if the demodulator is an envelope detector, the amount of ripples is not negligible and if necessary, can be eliminated through low-pass filtering (Nassar, p. 330). The need for automatic gain control in AM receivers and Automatic frequency control in FM receivers, how are these ‘control’ voltages produced and used? The Need for Automatic Gain Control in AM Receiver In AM receivers, the control voltage is produced in the AM detector diode, which generates DC voltage equivalent to the strength of signals. The resultant voltage can be fed back to the initial stages to lower the gain in the receiver, through a variable reactance component with a varying output capacitance. Hence, the bias is varied and the capacitance is modulated (Nassar, p. 300). The Automatic Gain Control (AGC) helps in maintaining a uniform strength of signal flowing into the receiver. The AGC allows for automatic changes ion gain of a radio receiver with respect to the changing strength of the signals to ensure that the remittance of the signals to the radio receiver is constant. In AM receivers, the Automatic gain control operates by preventing the linear relationship existing between signal amplitude and the sound waveform (Nassar, p. 368). The sound amplitude concerns the degree of change in the oscillating variants within the swinging system, is linked with loudness and can act as a regulation point of loudness. The signal amplitude is equivalent to the signal amplitude since the data contained in the signal is performed by the alterations of amplitude of the carrier. The carrier wave is altered by the input signal to allow effective conveyance of information to the system. The modification of the signal cannot be recuperated with a sensible fidelity if the circuit is not relatively linear. Nonetheless, the strength of the perceived signal would vary extensively. The variation depends on factors such as the power of signals and the space linking the transmitter and the receiver. The continual loss in the strength of signals from the generation point to the reception also affects the variation. Automatic Frequency Control (AFC) in FM Receivers The AFC is a hypersensitive device to frequencies and generates a DC voltage with amplitude and polarity that are proportional to the error frequency of the oscillator. When the receiver is almost tuned to the wanted frequency, the Automatic Frequency Control circuit in the receiver experiences an error voltage that is comparative to the degree to which the operator mistunes the receiver. The error voltage is therefore conveyed to the turning circuit in a mode that lowers the tuning error. The level of reduction of the voltage error determines the accuracy of the frequency desired and the clarity of the broadcast reception by the receiver (Nassar, p. 336). The voltage crearated in the receiver regulates the frequency and the degree of reception by regulating the sensitivity, selectivity and fidelity of the receiver. Fidelity of signals depends on the receiver’s ability to generate identical output signal from the original quality transmitted. The error voltage integration to precision by the AFC dictates the quality of the signal received by the receiver and the quality of the output signal (Nassar, p. 288). Sensitivity determines the receiver’s ability to distinguish one broadcasting station from another. The AFC regulates the receiver’s sensitivity through appropriate amplification of the voltages to attain appropriate levels of sound perceivable. Selectivity allows the receiver to receive the required signals only. Stations have different frequencies on which each is heard clearly and attaining appropriate voltage and feeding of appropriate signals to the receiver leads to proper selectivity. Summary on the Lab Activity An AM demodulator operates by obtaining the original data-containing signal from a modulated carrier. The signals are processed to a form that is detectable by the human senses. The demodulator operates to produce sound signals through the circuit from the extracted signals (Nassar, p. 325). The bandwidth and the range of frequencies affect the output sound of the receiver. The range of frequency in a receiver refers to the total frequency between the least limit of the initial frequency to the highest point of frequency in the tuner. Therefore, the addition of the IF and the final limit in the Local Oscillator frequency is right to determine the range of frequency. 1500 kHz + 470 kHz = 1970 kHz The demodulation process involves the identification of the novel signals from the modulated carrier signal. Demodulation influences the quality of sound through the signals frequency harmonization. If the bandwidth is doubled, the result would be same in output for noise. The noise results from the entrance of the oscillator to a nonlinear phase. This can be avoided by the demodulation of the signals to cause linearity. The carrier contains an in-phase component (I) and a quadrature phase component (Q). The Q- component is used to provide tracking signal. The I component is used in attaining the intended definite data. The I-component reference signal is rcj = √2cos[θcj]. the mechanical sparking machinery creates the noise in AM receiver, therefore the noise limiter would reduce the vibrations of the sparks and the possible that would enhance the path through which the signals flow (Nassar, p. 342). Technical Report on ZigBee Zigbee refers to a requirement for a suit of high profile communication protocols utilizing little, low-power digital radios. The function of the radios is based on IEEE 802 standard for personal area networks (PAN). The IEEE 802 refers to the standard that determines the least layer in the open system interconnection (OSI) model (Gislason, p. 3). ZigBee works on the basis of wireless connections. This means that ZigBee deals with the linking of systems that are not in contact. Nonetheless, ZigBee is distinct in its operation since it can link systems or objects separated by longer distances. ZigBee operates in layers where there are several layers beginning with layer 1 that extends extensively below and above one another to provide wireless connections in wider areas. ZigBee is highly reliable in its operation since the waves cannot be obstructed easily by any interference. The ZigBee specifications addresse physical and non-physical barriers and configures the application in a comprehensive model that bypasses the barriers. ZigBee operates in a varying speed of between 20 and 900 kilobits per second (kbps). ZigBee employs a wireless mesh network (WMN) in its operation. The mesh network in this scenario refers to a communication network consisting of a radio node arranged in a mesh topology. The mesh topology refers to the outline design of interconnections of diverse elements such as links and nodes of a computer network. The network topology assumes different shapes such as tree, bus, mesh and line. ZigBee operates upon the medium entrée control and the physical layer. The arrangement totals the IEEE 802 standard and incorporates other elements such as ZigBee Device Objects, which enable modification and support overall assimilation (Gislason, 5). ZigBee is targeted to edge with smart metering in addition to smart appliance. Smart meter is a complex electrical meter that notes the usage of electrical energy in hourly intervals and conveys the data to the utility for later evaluations. Smart appliance regards digital devices that connects communications between home devices via the internet. ZigBee was developed by many engineers and completed in 1998. The development resulted from the feeling that Bluetooth and WiFi applications would come to extinction since they cannot support several functionalities. In May 2003, IEEE 802 was completed and this enabled for a wider application of ZigBee. Nthe final version of ZigBee was created in 2007 that comprised the ZigBee feature set and ZigBee PRO feature set. The two modes of the applications interoperate within a single network if a standard security mold is incorporated (Gislason, p. 45). ZigBee Feature Set utilizes the ad-hoc self forming networks with the shapes such as the mesh and tree. It also uses the unicast, broadgcast and groupcasts. The loghical device types entail coordinator, router and the end device. The application services upheld by the feature set include device and service discovery, optional fragmentation. The application can also provide library services and explain the words used in the messages. The ZigBee Feature Set demands authentication -end network encryption at different levels of the application. There are optional network application keys and symmetric keys. The set qualifies and conforms to the certification of the platform (Gislason, p. 33). The ZigBee PRO Feature Set utilizes ad-hoc and the mesh only in its application. There is a variation in source routing enhancements. The applicable network layer is multicast. Has little dissimilarity with the ZigBee Feature Set and perform similar logical device types and similar applications. ZigBee PRO Feature Set has two security modes , high and standard security. It requires certification from the manufacturer and public profile. The provision also involves regular stipulated interoperability events. Generally, Mesh networking is a bandwidth and RAM efficient routing method. Both ZigBee and ZigBee Pro feature networks hold up mesh. Mesh Networking Illustration ZigBee Network Topologies and Routing The mesh network routing allows path creation from every source device to any destination device through a path created by routing packets via neighbors. The mesh network possesses no restrictions in its path of connection and exchange of information from any of the linked devices. Through this connection, a device can receive data and also send through a different path simultaneously. The cluster tree network routing channels packets up and downward the tree configuration formed through network provision until they reach the eventual destination. The cluster tree is only applicable in ZigBee feature set. The transmission can fail if the parent link is not operational over a period and a net mask type tree routing must also be utilized in the connection (Gislason, p. 102). Many to one and cause routing characteristics concentrate on the demerits in the mesh networks where the demands of the table size routing are higher in certain information transfer situations. Many to one permits any device connected to the net to route information to a well defined concentrator via one routing table in every device. Many concentrators can also be linked to a single network. Source routing permits a concentrator to supply feedback to every device within the network. The end devices are low power in both ZigBee feature and ZigBee PRO feature set as they do not participate in routing, but only link through their parent coordinators at application specified instances. The devices are configured according to the application objects. Application object connect through swap over of clusters. Every profile object can consist of single or many clusters and attributes. The bidding criterion ensures interoperable swap of attributes (Gislason, 204). The application profiles incorporate agreement on messages describing an application space such as smart energy. The endpoints incorporate a logical addition to a single ZigBee radio that allows support for numerous applications. The overall security prompts of the ZigBee involve security at each layer, two security modes and the final implementation of security. There is a network layer security and application layer security. The security for network command includes route request, reply and error. The two security models have double network keys and the capacity to alternate the keys. The security implementation associates with the trust center. The center functions by formulating and dispensing the network keys to the main system for use (Gislason, 308). International Telecommunication Union (ITU) The Union ensures compatibility among different states of the world by targeting uniformity of the system and regulation of communication among the members to achieve coherence (ITU p. 4). The union ascertains that all the current radio systems meet required federal standard and obtain authorization before commencement. The permission acts as a proof that the registering station has met the conventional standards. The union manages the National Oceanic and Atmospheric Administration (NOAA) satellite systems to confirm that all systems have matching features. The satellite systems have space net to attain compatible function. The union associates with other organizations in the private sector to avert interferences and avail resolutions (ITU p. 11). The International Telecommunication Union has also engage different governments and other worldwide entities to guarantee prospective spectrum availability and alleviate interferences. Compatibility among the radio stations is essential because of the ease in management. Communication systems experiencing problems would be solved easily since the problem can be fixed at a common point. The compatibility is also essential since there are no clashes of frequencies among different states. There is an explicit allocation of frequencies to different countries and stations and use a common system. Compatible radio systems provide ease in regulations since a common constitution can apply to all the stations irrespective of the country. There is also easy assessment of the radio stations and their systems through the server. The well suited of the radio systems foster uniformity in the provision of networks since the network with given specifications can serve network systems with common requirements. The benefit of this facet is that it reduces the maintenance and operation costs (ITU p. 16). Works Cited Gislason, D. ZigBee Wireless Networking. New York: Newnwss, 2008 Nassar C. Telecommunications Demystified: A Streamlined Course in Digital Communications (And Some Analog) for Ee Students and Practicing Engineers. New York: Newnes, 2001 International Telecommunication Union (ITU). The International Telecommunication Union: Building the Information Society. Geneva: International Telecommunication Union, 2007 (1-24) Read More