MICROWAVE BANDPASS FILTER :IDLE lumped filter

IDLE lumped filter:-When we are discussing lumped elements, their are two broad categories of inductors and capacitors. The first is surface mount parts, which are suitable for use on a microwave printed circuit board. The second category is thin-film lumped elements, which are used on microwave integrated circuits (MICs) on alumina or other "hard" substrates, as well as in MMIC implementations. Surface mount capacitors can be useful up to Ku-band, while the inductors generally have self-resonances below X-band. Thin-film capacitors are used routinely up to 100 GHz in MMICs. Lumped inductors on thin-films (and MMICs) take the shape of spiral inductors, and are limited to frequencies Ku-band and lower. Inductors are the problem stepchild of lumped element filters and other microwave circuits!!

The terms "tee" and "pi" are used to describe lumped element filters, as well as attenuators and other networks. A tee element starts with a series element, while a pi network starts with a shunt element as shown below. The "tee" resembles a letter T while the "pi" resembles a Greek.Used in band-pass filters, lumped elements can really help your designs. Not only are the resulting filters compact, but they have no "natural" reentrant modes that you will encounter with other filter technologies such as planar resonator structures.

IDLE Distributed: Transmission line filters use distributed theory to translate lumped LC filters to lumped filters composed of distributed stubs. Inductors and parallel LC resonators may be replaced with shorted distributed stubs, Capacitors and series LC resonators may be replaced with open distributed stubs. Replacing LC resonators with a single stub is more efficient, but results in significantly more aliasing.  Inductors may be replaced with 90 deg distributed segments.  Series resonators may be replaced by 180 deg distributed segments.  Checking the "Combine Stubs" box in Filter Solutions will cause filters to be synthesized with single stub resonators.  Checking the "Use Segments" box will cause filters to be synthesized using distributed segments instead of cascade stubs.

WAVEGUIDEFILTER: In many microwave radio systems, waveguide filters are used as preselectors and diplexers. With highchannelcapacity systems, the filters must have a broad passband, high selectivity, low-insertion loss and a small differential or group

delay. The former two requirements dictate that the filter have a large number of circuit elements. However, with conventional waveguide band-pass filters, this tends to degrade both the passband insertion loss and the group delay.

STEPPED IMPEDEANCE: A dual-band band pass filter equipped with stepped-impedance resonators for filtering a signal, comprising: a circuit board; an input end located on the circuit board for receiving the signal; an output end located on the circuit board to transmit the filtered signal; and at least two resonators located on the circuit board, each of the resonators including a connecting section and two coupling sections; the connecting section connecting two coupling sections; one coupling section of the first resonator being coupled with one coupling section of the second resonator and the other coupling section of the first resonator being coupled with the input end or the output end.

relatively smaller size than the BPF having parallel coupled lines.

HAIRPIN FILTER: The hairpin bandpass filter(BPF) has been extensively investigated and widely used many microwave and millimeter-wave systems in order to achieve high performance,small size and low cost and comply with strictly required transmission specifications. Thereare many types of bandpass filter design techniques to meet the above requirements,such as the use of high permittivity materials,variation of resonators structures,and use of multiple resonant modes strip line BPF having Hairpin resonator structure, and use of multiple resonant modes. Controlling the center frequency and improving the characteristics of the purposed BPF have been addressed. The use of DGS cells shows a good effect on the stopband. The second order filters with quasi elliptic reponse were presented. Controlling the center frequencies and achieving a good matching at the passband can be simply realized.

COMBLINE FILTER: The resonators in this type of filter consist of quasi transverse electromagnetic(TEM)-mode transmission lines that are short-circuited at one end and have a lumped capacitance C○ between the other end of each resonator line element and ground.

Coupling between resonators is achieved in this type of filter by way of fringing fields between the resonator lines. If the resonator sections are long at the primary passband(f○), then thesecond passband will be centered on 4f○. If the resonator line elements are made to be less at the primary passband, the second passband will be even further removed from the primary passband.