## Fundamental waveguide characteristics

The principles and parameters discussed in previous sections are applicable to waveguides and microwave devices. However, generally waveguides are used over short distances and losses are minimized. If a dielectric waveguide is used then primary and secondary coefficients such as R, G and a have to be considered. In this text air-filled rectangular waveguides will be discussed. The part of the electromagnetic spectrum referred to as the microwave region loosely includes the range 1-300 GHz for...

## Wave reflection and the reflection coefficient

It has already been mentioned that for a lossless line equation (7.8) applies. If the line is increased in length the inductance increases, and the capacitance increases because the capacitance area is greater. So overall the L C ratio remains the same. When the load and generator impedances are both equal to the characteristic impedance of the line, maximum energy is absorbed by the load. However, when a line is not terminated in its own impedance the load absorbs only a portion of the energy,...

## Further problems

A phase-shift oscillator has to provide a frequency of 15 kHz. Design a suitable circuit similar to Fig. 1.5. Select C 12 nF. Answer Rt 361, a range of gain setting resistors 2. Design a Wien bridge oscillator capable of giving a constant frequency of 2.5 kHz. Select C 0.01 F. Answer R 6.369 kQ select Rt and R2 for Av 3 3. A Wien bridge oscillator has to operate at 75 kHz using Fig. 1.9. To ensure stability a zener diode network is used to keep the gain between 2.7 and 3.2. Calculate all the...

## E

Vce VC - VE Also, using Kirchhoff's voltage law, Note that when drawing a d.c. load line the saturation current will no longer be given by The cut-off point will remain the same when drawing the d.c. load line. This will be shown in the next section, which deals with small signal amplifiers. The biasing of a transistor is purely a d.c. operation, as has been shown in the previous sections. Also it has been seen that the purpose of biasing is to obtain a Q-point about which an input a.c. signal...

## Applications Information

Double sideband suppressed carrier modulation is the basic application of the MC1496. The suggested circuit for this application is shown on the front page of this data sheet. In some applications, it may be necessary to operate the MC1496 with a single dc supply voltage instead of dual supplies. Figure 26 shows a balanced modulator designed for operation with a single 12 Vdc supply. Performance of this circuit is similar to that of the dual supply modulator. The circuit shown in Figure 27 may...

## Standing wave ratio

Standing waves have already been mentioned, together with their formation due to load termination. Figure 7.4 shows the result of producing standing waves on a transmission line. Remember that standing waves are produced when two waves having the same frequency and amplitude and travelling in opposite directions are superimposed. The figure shows that standing waves produce points of minimum and maximum disturbance called nodes and antinodes, and this applies to voltage or current waves....

## The Bode plot

It is convenient and generally accepted in practice to plot the logarithmic value of frequency response rather than the raw frequency itself. This is because a greater range of frequencies can then be plotted on suitable graph paper without losing the resolution of the response curve. Log-linear or log-log graph paper may be conveniently used. Figure 6.8 uses loglinear or semilog paper, with the frequency plotted horizontally and the gain dB plotted vertically. Log-linear graph paper is also...

## Power amplifiers

Figure 5.1 shows two applications where a power amplifier may be used. In Fig. 5.1 a two RF power amplifiers are used to feed power into the antenna of a transmitter. The booster amplifier raises the power level to the value required in order to drive the final RF amplifier which is responsible for feeding large power levels into the antenna via the antenna matching unit. Note that matching stages are required in order to match the output of one stage to the input impedance of the next stage...

## The basic structure and requirements of an oscillator

Any oscillator consists of three sections, as shown in Fig. 1.4. Any oscillator consists of three sections, as shown in Fig. 1.4. The frequency-determining network is the core of the oscillator and deals with the generation of the specified frequency. The desired frequency may be generated by using an inductance-capacitance LC circuit, a resistance-capacitance RC circuit or a piezoelectric crystal. Each of these networks produces a particular frequency depending on the values of the components...

## Waveguide junctions

Waveguide junctions are required to reroute power in a similar way to junction devices in optical fibre work. They are also used to mix power from multiple sources. However, anything that alters the geometry of a waveguide will have an effect on the electric and magnetic fields and may change the characteristic impedance of the guide. If the guide normally works in the TE10 mode with E-field and H-field patterns, as shown in Fig. 7.11, then bend couplings, similar to those in Fig. 7.14, should...

## Mug Telecommunication

FIGURE 18. 100MHz NOISE FIGURE vs COLLECTOR SUPPLY VOLTAGE DIFFERENTIAL AMPLIFIER CONFIGURATION FIGURE 19. 100MHz NOISE FIGURE AND POWER GAIN vs BASE-TO-EMITTER BIAS VOLTAGE TERMINAL 7 FIGURE 18. 100MHz NOISE FIGURE vs COLLECTOR SUPPLY VOLTAGE DIFFERENTIAL AMPLIFIER CONFIGURATION

## The twinT oscillator

This oscillator is shown in Fig. 1.10 a and is, strictly speaking, a notch filter. It is used in problems where a narrow band of noise frequencies of a single-frequency component has to be attenuated. It consists of a low-pass and high-pass filter, both of which have a sharp cut-off at the rejected frequency or narrow band of frequencies. This response is shown in Fig. 1.10 b . The notch frequency fo is attenuated sharply as shown. Frequencies immediately on either side of the notch are also...