MiniaturizedRCFilters Using Phase Locked Loop

Abstract

It is shown that an automatic phase-locked loop (APLL) can be used as a bandpass filter and FM discriminator while satisfying the circuit conditions imposed by microminiaturization techniques. It has the advantage over other methods of ease of adjustment and reduction in the number of circuit components. For this reason it is to be assumed that the APLL will be added to the few practical solutions of the f1·equency selection problem in microminiaturization available to date.In contrast to most other applications, no assumptions can be made here about the ratio of the natural undamped system f1'equency to the lock range of the loop. This is taken account of in an analysis of the APLL which enables design equoiion« and considerations to be derived. A n approximation of the so-called capture ratio, defined as the ratio of capture-to-lock range, is presented. It produces results that correspond very well with the equivalent measurements.The description of an APLL designed as RC channel filter and discriminator for a multichannel data receiver is presented. RC active circuits that are compatible with current microminiaturization techniques are employed exclusively. They are described in detail, and an analysis of the voltage-controlled oscillator used is 7ncluded 7n the Appendix.

From Printed Circuit Boards to Systems-on-a-Chip

“…One of the early, and most interesting, was to design a phase-locked loop, or PLL (see Fig. 7) such as to provide both an inductorless bandpass filter and an FSK frequency demodulator [2]. This was an elegant way of combining the two functions of channel selection and FSK demodulation by one and the same circuit.…”

Design and performance study of phase‐locked loop using fractional‐order loop filter

“…The capture range is the frequency range ± Δ ω c , centered about ω 0 , over which the loop can acquire lock . In general, the derivation of capture range of integer‐order PLL is nontrivial and only an approximate expression can be formulated as follows : where | T LF ( jΔω)| is the magnitude of loop filter at frequency Δω.…”

“…This presumes that the PLL was initially locked onto the input signal. The approximate expression for lock range of an integer‐order PLL is given by where T LF (0) is the dc gain of the integer‐order loop filter.…”