Brief Introduction to High Frequency Passive Circuits

Abstract

AbstractComponent used in any circuit, as per functionality, can be classified into two basic categories, passive and active components. Passive component can’t provide energy to the circuit in the form of voltage or current i.e. provides no power gain to the circuit. As well as it can’t amplify or process any signal. In low frequency (considerable up to 3 GHz, parasitic effect and radiation loss increases fatally beyond that) circuit where the component dimension is very less than operating wavelength (λ), i.e. Lumped parameter circuit, Resistor, Capacitor, Inductor or Conventional PN Junction diode can be the typical example of passive circuit components. Passive device or component characterized with monotonic I-V curve which must be within 1st or 3rd (or both) quadrant with always positive differential resistance. In high frequency where the dimension of λ is in order of the component dimension, Distributed parameter concept is applicable. Microwave device is the most suitable device to operate in this range. The frequency range can be from 3 to 100 GHz or even more. But at very high frequency dielectric and Ohmic losses became fatal and manufacturing devices for higher frequency became very demanding. Different waveguide sections like Attenuator, Terminator, Filter, Coupler and Ferrite devices are passive microwave components. Whereas, different types of Oscillators, Amplifiers, Mixers, Multipliers and detectors used in microwave frequency are the typical examples of active devices. Passive device in Microwave frequency range can be characterized based on several aspects. Transfer characteristics of a passive device must be linear, continuous wave signal must not get distorted and the S- parameter of the device have to be independent of power. For a two-port passive device or component, reflection at both port are identical, i.e. |S11|2 = |S22|2. And most of the passive components used in microwave circuit are reciprocal except Ferrite isolators and circulators [1]. In this chapter, we will discuss about different types of passive circuit components used in microwave frequency range.KeywordsPassive circuit componentsS-parametersHigh frequencyFilter