IF amplifiers and filters

This chapter discusses IF amplifiers and filters as there are a number of IF filters used in radio receivers. In addition to the L-C filters, there are various types of crystal filter, monolithic ceramic filters, and mechanical filters to consider. This chapter discusses various types of IF filters, their characteristics and their applications. The shape factor of the filter is defined as the ratio of the –60 dB bandwidth to the –6 dB bandwidth. This is an indication of how well the filter rejects out of band interference. The IF amplifier may or may not use two (or more) filters, depending upon the type of design. In cases where only one filter is used, then the filter is usually placed at the input of the amplifier in order to eliminate the mixer products that can affect the IF amplifier performance. The noise produced by the IF amplifier can be significant, which means that an output IF filter is indicated in order to eliminate that noise..