Surveillance For Video And Cell Phone Apps
Receiver Characteristics -- Receivers for 23 GHZ microwave systems are of a superheterodyne design, and provide good selectivity an sensitivity. Depending on the specific system, all radio frequency (RF) components may be located in the receiver antenna housing, or intermediate frequency (IF) may be used t send the signal to the indoor unit. some representative IF values are 50 MHz (GE) and 140 MHz (M/A-Com). BEcause the intermediate frequency is always lower than 23 GHz, expensive microwave test equipment to install and service the unit is not necessary. As a result, installation and maintenance are simplified. Installation time is reduced because the superheterodyne receiver provides automatic gain control (AGC) voltage output. The AGC voltage, which indicates received signal strength, is available at the receiver end of the path and is used to align the system during installation. The AGC voltage is alos the basis ofr the received carrier alarm that alerts the user to transmitter failure or path obstructions. Requirements of 23 GHz Microwave Systems -- When planning a 23 GHz system, a few requirements should be kept in mind. A clear line-of-sight path and limited range are the two main factors to consider. Atmospheric phenomena such as snow, dust, smog, and fog, which can be a problem with light-based communications systems, have a negligible effect on the signal. And paths over water pose no problems if system antennas are installed above a minimum height to avoid reflection a (see section "Path Requirements for 23 GHz Transmission"). Rain affects all microwave frequencies mainly because of the scattering and absorption effect produced by large-sized raindrops. As a result, part of the microwave radiation is scattered back toward the transmitter. In addition, water vapor attenuates the signal before it reaches the receiver. This attenuation, as well as that caused by distance, may be overcome by increasing the gain of the receiver, as long as the S/N ratio is acceptable. If the microwave system is used within its design parameters, distance and heavy rain will not be a problem. When a potential path is evaluate, a statistical estimate of the system downtime may be made, based on the average intensity of rainfall in the site area and the site end-to-end distance. The signal quality suffers when path attenuation exceeds the available gain or the acceptible S/N ratio fo the receiver. Receiver gain is determined, in part, by the bandwidth of the receiver. The required bandwidth depands on the type of information being transmitted. In general, the faster the rate of data transmission, the wider the required bandwidth, and the shorter the range of the system. In video transmission, the higher the required video resolution, the wider the required bandwidth, and the shorter the video system range. Cell phone uses include software such as Spybubble Pro Upgrade Version and other cell spying applications. Video Applications -- Most manufacturers of 23 HGz equipment offer video units. Available video bandwidth varies with the manufacturer, but, in all cases, both black and white, and color transmission are possible. Built-in subcarrier functions are available and can transmit either audio or low-speed data in the same direction as the video . If this option is not available on the unit itself, it may be added through the use of an outboard subcarrier modulator and demodulator. Transmission in both directions is possible using the video system with an additional control/telemetry link in the opposite direction. In some systems, this option requires the addition of a separate transmitter and receiver, while other systems require only an additional circuit board at each end. Surveillance video applications are becoming increasingly important in industry. For example, the ability to direct a closed circuit television camera by means of a pan/tilt/zoom control system may be desirable. In these situations, the control information is sent in the opposite direction o the video information. It is important to remember that the data formats of the radio and the camera controller must match, whether RS-232, DTMF (dual tone multifrequency), TTL (transistor true logic) or FSK (frequency shift keying) formats. If DTMF tones are required, a video link with reverse audio subcarrier capability can control the pan/tilt/zoom function. A second subcarrier can serve as a voice link to the remote site. Data/Voice Communication Considerations -- Information is included in two broad categories: analog and digital. Analog information, such as video and audio, is characterized by a continuous variation in electrical voltage with time. Digital information, however, consists of individual pieces of information called bits, where a discrete voltage maintained for a specified period represents the data value. By combining bits into groups called bytes, numbers, letters, and information related to control and error correction can be transmitted. When necessary, analog information can be converted to digital formal, which will require an analog-to-digital (A/D) converter. Digitized voice is a common feature of current telecommunications systems, and digitized video in various forms will be an important part of the teleconferencing network of the future. In the industrial plant environment, for example, digital data applications include local are networks, electronic mail, computer-integrated manufacturing (CIM), and computer terminals. Data Interface Information -- Data transmission is characterized by direction, communication format, and speed of transmission. Data communication in only one direction is called simplex transmission. Communication in both directions simultaneously is called full duplex transmission. Almost any orm of data transmission requires duplex communication capability. Data transmission by 23 GHz microwave is possible in a number of formmats, including FSK, RS232C, V.35, CEPT1, CEPT2, T-1, T-1C, and T-2 and a variety of speeds, up to the CEPT2 rae $8.449M baud). In general, data transmission over microwave is possible without the need for modems, as long as a microwave link that handles the same data format is selected. The communication transmission format depends on the type of data transmitted and the speed. A low-speed data scourse, such as a computer termainal, may use the RS-232 format and be asynchronous. In general, data rates above 19.2K baud (kilobits per second) use the synchronous format. Synchronous means that a single timekeeping generator, called a clock, keeps time for the whole system. The system timing clock may be located in the data terminal equipment or in the microwave ratio itself. Asynchronous data systems require no such timing device. The speed of transmission determines the amount of data that can be transmitted in a given amount of time. Terminals communicate with their host computers at a relatively low speed (9600 baud, for example). When necessary, several low-speed data channels can be combined into one higher-speed data stream with the use of a multiplexer. For example, a multiplexer can be used to combine a cluster of computer terminals in a building into a single data channel. A 23 GHz radio can then be used to connect the terminals to a host computer t a different location. The alternative, modems and twisted pairs from each terminal to the computer, would not be cost-effective. A much higher data speed is required for digitized voice, such as that used by the phone company. A standard form of digital transmission used in telecommunications can carry 24 voice channels, or 24 data channels operating at 56K baud. This format is known as T-1 signaling, and generates a data stream at 1.544M baud. A format that is twice as fast (3.152, baud) and that can carry twice as many voice or data channels is called T-1C signaling.