A new lock indicator circuit for microwave and millimeter-wave phase locked loops

• Published in: IEEE transactions on microwave theory and techniques 1988-09, Vol.36 (9), p.1362-1365
• Main Author: Sau, J.B.I.
• Format: Article
• Language: English
• Subjects: Applied sciences; Circuit properties; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Frequency conversion; Logic; Microwave circuits; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwave oscillators; Millimeter wave circuits; Phase detection; Phase frequency detector; Phase locked loops; Voltage control; Voltage-controlled oscillators
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/22.3684

A circuit useful as a lock detector in microwave phase-locked loop (PLL) systems has been developed. This circuit avoids the quadrature phase detector or coherent amplitude detector commonly used as a lock indicator in PLLS, thereby reducing the microwave circuitry and components. It is based on the properties of the phase-error signal coming from the phase detector; a frequency-voltage conversion is performed on it in a low-frequency (secondary) PLL, the input to which is the output of the phase detector in the main (microwave) PLL. The secondary voltage-controlled oscillator (VCO) control signal gives, after a comparison, a logic level related to the lock condition in the main (microwave) PLL. This circuit has been used with success in microwave phase-locked oscillators (PLOs) in which the phase detection was made at 290 MHz, 2.55 GHz, 27 GHz and 29.7 GHz.< >