Browse Prior Art Database

Frequency/Phase-Locked Detector

IP.com Disclosure Number: IPCOM000041380D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Hong, JH: AUTHOR

Abstract

A single circuit is used to measure the frequency error and phase error associated with a clock recovery phase-locked loop (PLL). Such PLLs are used as a clock recovery mechanism in a synchronous ring communication network. The acquisition time of the PLL is improved by a rotational frequency detector (FD) which is incorporated as a frequency acquisition aid. A circuit suitable for this purpose is shown in Fig. 3 in which an amplifier, a peak detector and a low-pass filter process an error signal VRF . The output of the low-pass filter is applied to a comparator which makes the decision whether the phase error or the frequency error exceeds a design specification. A rotational frequency detector is a frequency acquisition aid for narrow-band PLLs, such as the clock recovery PLL used in a ring adapter.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Frequency/Phase-Locked Detector

A single circuit is used to measure the frequency error and phase error associated with a clock recovery phase-locked loop (PLL).

Such PLLs are used as a clock recovery mechanism in a synchronous ring communication network. The acquisition time of the PLL is improved by a rotational frequency detector (FD) which is incorporated as a frequency acquisition aid. A circuit suitable for this purpose is shown in Fig. 3 in which an amplifier, a peak detector and a low-pass filter process an error signal VRF . The output of the low-pass filter is applied to a comparator which makes the decision whether the phase error or the frequency error exceeds a design specification. A rotational frequency detector is a frequency acquisition aid for narrow-band PLLs, such as the clock recovery PLL used in a ring adapter. The ring adapter attaches terminals to a ring communication network. The rotational frequency detector provides an output signal which is proportional to the frequency difference between two input signals. In order to measure the frequency drift, the output of the local crystal oscillator (Fig. 1) is connected to the reference input of the rotational FD, and the output of the PLL is connected to the other input. The output of the rotational FD is connected to an error detect circuit which measures the frequency drift. Fig. 2 shows a circuit arrangement for generating a voltage (VRF) which is proportional to the dynamic phase error and frequency error. If the VCO frequency f...