Browse Prior Art Database

Frequency Measurement Logic

IP.com Disclosure Number: IPCOM000111346D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 79K

Publishing Venue

IBM

Related People

Hanna, CA: AUTHOR

Abstract

Disclosed is a device for determining the frequency of a pulsed or continuous-wave RF signal digitally by counting the transitions of that signal and the positive and negative transitions of a high-speed reference clock within a measurement time interval. This device introduces several improvements to the Frequency Measurement Logic (FML) device previously disclosed [*], including doubling of the operating frequency, reduced metastability errors, and built-in divider.

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Frequency Measurement Logic

      Disclosed is a device for determining the frequency of a pulsed
or continuous-wave RF signal digitally by counting the transitions of
that signal and the positive and negative transitions of a high-speed
reference clock within a measurement time interval.  This device
introduces several improvements to the Frequency Measurement Logic
(FML) device previously disclosed [*], including doubling of the
operating frequency, reduced metastability errors, and built-in
divider.

      A typical embodiment of the FML is shown in Fig. 1.  Input is
SIGNAL RF, a REFERENCE RF, a TRIGGER CLOCK, and a digital INTERVAL
word.  Output is a digital FREQUENCY word and a DATA VALID indicator.
Counter 2 counts positive transitions of the SIGNAL RF input,
producing the signal count Ns.  Counter 3 counts positive transitions
of the REFERENCE RF input, producing the reference count Nr.  Timing
logic 1 and compare 6 control the counters to generate counts during
the desired time interval as determined by inputs TRIGGER CLOCK,
MODE, and INTERVAL.  This logic also controls the operation of the
registers and divider, and produces the DATA VALID indicator.
Registers 4 and 5 buffer the counts so that the divider 7 has one
complete counting cycle to operate.  Correcter 8 adjusts the
reference count Nr by adding or subtracting either 0 or 1/2 count, so
that the signal count Ns by the corrected reference count Nr produces
the frequency output.

      Fig....