Transceivers

The smart shirt Sensatex, a New York-based company, is developing a shirt that is used to monitor patients vital signs. The shirt is made of an electro-optical fabric that transfers data from the wearer to the garment. A transceiver on the shirt records the data and sends it to a wireless gateway, from which it can be transmitted to the doctor. 

Figure 2.2.9 shows a typical portable MRI console. The MRI console consists of a digital system (PC), MRI transceiver, 3 channel gradient driver and rf transmitter. 

Figure 2.2.11 shows a typical block diagram of the MRI transceiver used for the compact MRI system. The waveform generator can be replaced by the DA converter on the DSP board described in the previous section. Because the typical input/ output power level for the transmitter and from the preamplifier is about 1 mW, a commercially available transmitter and preamplifier are directly connected. 

A wide range of conttol systems is used in household appliances. A standard conttol loop consists of sensors, control units and actuators. The appliances become more powerful and efficient, as the technology is developed and integrated into microsystems. Matchbox-sized sensors can be equipped with wireless radio transceivers and their own miniature operating system to tiansmit continuous data to the facility manager. 

A small weather station is illustrated in Figure 3.181. Such stations are usually available in both the cabled and the wireless forms to provide all the information that is needed to control and optimize the various alternative energy processes. These units are usually preprogrammed to provide simple meteorological data, and to perform the complex calculation of ETo (evapo-transpiration). The microprocessor-based systems automatically measure the variables and store the data before transmitting it to a user-supplied remote PC over distances of up to about 10 mi. The units are usually provided with a rechargeable battery pack and a spread spectrum radio transceiver. 

The wideband holographic imaging technique is very sensitive because of the active, coherent, heterodyne detection that is employed in typical systems [15-17], Therefore, the primary limitation on image acquisition is the time required to mechanically scan the transceiver. Two-dimensional raster scans are often used for laboratory experiments, and these typically require scan times on the order of 1-30 min. Practical systems employing linear switched antenna arrays and mechanical scanning reduce this time to 1-10 seconds [15-17],... 

The imaging system transceiver is shown in a simplified schematic form in Fig. 2. This transceiver consists of two oscillators. The transmit, or RF, oscillator is swept across the millimeter-wave frequency band of interest, and the LO is offset from this frequency by a fixed IF. The received signal is mixed with the LO to frequency down-convert the data to the IF. Once down-converted, this signal can be easily amplified and filtered, resulting in a high SNR. The received IF signal is then mixed with in-phase (nonphase shifted) and quadrature (90° phase shifted) reference IF signals. The outputs of this final... 

Fig. 2. Heterodyne millimeter-wave transceiver — simplified schematic (drawing from [17] IEEE).

Fig. 4. Millimeter-wave holographic concealed weapon detection system (left) and close-up of the 128-element, 27-33 GHz linear array and transceiver system (right) (images from [17] IEEE).

A cylindrical prototype was developed at PNNL that operates from 27-33 GHz using a vertically oriented linear array, as shown in Fig. 9. This system uses switching and transceiver technology similar to the prototype shown in Fig. 4. However, this system is composed of 384 antenna elements versus 128 for the previous system. This system collects a 360° scan in 6-10s. Image reconstruction is then performed using a conventional PC coupled to an array of high-speed co-processors. Example cylindrical images collected with a laboratory transceiver and scanner are shown in the lower half... 

Transceiver emits radio signals that excite the hydrogen atoms while measuring the signal released by their return to equilibrium. This signal can be used to determine specifics about the tissue. 

NMR coupling to CE or CEC does not require major modification to the existing CE or CEC instrumentation because the transceiver coil is either wrapped... 

The car truck is also equipped with a power supply soince, an observation system, control equipment including power automatic machinery and a transceiver (another option is also possible of electric-power transmission using trolley or a rail with pulse-code modulation of steering commands). 

---