文档介绍：Designing Edge-coupled Microstrip Band-Pass Filters Using in Microwave
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The design of printed filters, which perform close to their modelled specifications, can
be a difficult and time consuming process using traditional methods. This application
note shows a straightforward and largely non-mathematical method of tackling this
problem using Microwave Office (MWO) assuming little or no knowledge of filter
design. A basic familiarity with the operation of MWO is assumed. Microstrip filters are
the examples shown, but the same principles can be applied to other types of filter
(stripline, suspended substrate etc) using any of the excellent models that are
available in the MWO element catalogue.
Introduction
Band-pass filters require precise transmission characteristics to allow a desired band of
signals to pass with minimum loss through a two-work and reject unwanted signals at
both higher and lower frequencies. They are generally characterised by such terms as
bandwidth, centre frequency, insertion loss, selectivity or rejection, ripple and return loss. For
instance a particular filter may have a centre frequency of 1000 MHz and bandwidth of 100
MHz or 950 –1050 MHz. The insertion loss may be required to be less than 1dB in this band.
The rejection at 1100 MHz may be specified as 40 dB or greater. It is usually desirable to
have a high return loss in band. Return loss and in-band ripple are directly and inversely
related. For instance an in-band ripple specification of corresponds to a return loss of
, and a ripple of corresponds to a return loss of . Chebyschev
polynomials are often used to describe the mathematical relationship between these