Compact monolithic low-pass filters using a bridged-tee architecture

Pass-band insertion loss in low-pass filters implemented in monolithic technologies is mainly limited by the Q of the inductor coils. Furthermore, the size and cost are dominated by the coils. For these reasons, most circuits used in filters of this type are of low order with a minimum number of coils. This paper describes a low pass filter using a bridged-tee architecture to implement a 5^th order low pass filter with two attenuation poles at finite frequencies. The circuit is especially well-suited for use in harmonic suppression filters with low pass-band insertion loss. The filter is compared experimentally with a conventional ladder network using two coils. The bridged-tee circuit shows equivalent performance but only requires about 60% of the area of the ladder circuit.