Digital measurement of amplitude and phase of a sinusoidal signal and detection of load coil based on said measurement

Claim 1

A method of measuring driving point impedances Z tr , Z tg and Z rg of a telephone subscriber's loop, where Z tr is the driving point impedance between the tip and ring of said telephone subscriber's loop, Z tg is the driving point impedance between the tip and ground, and Z rg is the driving point impedance between the ring and ground, comprising steps of: simultaneously applying to said tip and ring a sinusoidal stimulus signal of a predetermined frequency ω; measuring said sinusoidal stimulus signal which is transmitted through said tip and ring to generate a first pair of respective measured signals; digitizing said first pair of measured sinusoidal signals to generate a first pair of respective digitized sample signals s t1 (n) and s r1 (n) where n=0, 1, 2, . . . , by using the sampling period T=2π/ω s , and the sample size N=kM where ω s is the sampling frequency, k is a positive integer and M is the fundamental period of sin(2ωnT); multiplying said digitized sample signals s t1 (n) and s t1 (n) by sin(ωnT) and cos(ωnT); applying to either said tip or ring said sinusoidal stimulus signal of said predetermined frequency; measuring sinusoidal signals which are transmitted through said tip and ring to generate a second pair of respective measured signals; digitizing said second pair of measured sinusoidal signals to generate a second pair of respective digitized sample signals s t2 (n), and s r2 (n) where n=0, 1, 2, . . . , by using the sampling period T=2π/ω s , and the sample size N=kM; multiplying said digital sample signals s t2 (n), and s r2 (n) by sin(ωnT) and cos(ωnT); and processing all of said multiplied signals to derive the driving point impedances Z tr , Z tg and Z rg of said telephone subscriber's loop.

Claim 2

A method of measuring driving point impedances Z tr , Z tg and Z rg of a telephone subscriber's loop, where Z tr is the driving point impedance between the tip and ring of said telephone subscriber's loop, Z tg is the driving point impedance between the tip and ground, and Z rg is the driving point impedance between the ring and ground, comprising steps of: simultaneously applying to said tip and ring a sinusoidal stimulus signal of a predetermined frequency ω; measuring said sinusoidal stimulus signal which is transmitted through said tip and ring to generate a first pair of respective measured signals; digitizing said first pair of measured sinusoidal signals to generate a first pair of respective digitized sample signals s t1 (n) and s r1 (n) where n=0, 1, 2, . . . , by using the sampling period T=2π/ω s , and the sample size N=kM where ω s is the sampling frequency, k is a positive integer and M is the fundamental period of sin(2ωnT); multiplying said digitized sample signals s t1 (n) and s t1 (n) by sin(ωnT) and cos(ωnT); applying to either said tip or ring said sinusoidal stimulus signal of said predetermined frequency; measuring sinusoidal signals which are transmitted through said tip and ring to generate a second pair of respective measured signals; digitizing said second pair of measured sinusoidal signals to generate a second pair of respective digitized sample signals s t2 (n), and s r2 (n) where n=0, 1, 2, . . . , by using the sampling period T=2π/ω s , and the sample size N=kM; multiplying said digital sample signals s t2 (n), and s r2 (n) by sin(ωnT) and cos(ωnT); and processing all of said multiplied signals to derive the driving point impedances Z tr , Z tg and Z rg of said telephone subscriber's loop.

Claim 6

An apparatus for detecting the presence of a load coil on a telephone subscriber's loop by measuring driving point impedances thereof comprising: a sinusoidal signal generator for generating a plurality of sinusoidal stimulus signals of predetermined discrete frequencies, ω i , i=1, 2, 3 . . . , m, to be applied to the tip and ring of said telephone subscriber's loop; measuring means for measuring separately current which flows through said tip and ring to generate respective measured sinusoidal signals; digitizing means for digitizing said measured sinusoidal signals to generate respective digitized sample signals s ti (n) and s ri (n), where n=0, 1, 2, . . . and i=1, 2, 3, . . . ,m, by using the sampling period T=2π/ω s and the sample size N=kM where ω s is the sampling frequency, k is a positive integer and M is the fundamental period of sin(2ωnT); and processing means for processing said digitized sample signals s ti (n), and s ri (n) to derive the driving point impedances of said telephone subscriber's loop for each of said plurality of sinusoidal stimulus signals.

Claim 7

An apparatus for detecting the presence of a load coil on a telephone subscriber's loop by measuring driving point impedances thereof comprising: a sinusoidal signal generator for generating a plurality of sinusoidal stimulus signals of predetermined discrete frequencies, ω i , i=1, 2, 3 . . . , m, to be applied to the tip and ring of said telephone subscriber's loop; measuring means for measuring separately current which flows through said tip and ring to generate respective measured sinusoidal signals; digitizing means for digitizing said measured sinusoidal signals to generate respective digitized sample signals s ti (n) and s ri (n), where n=0, 1, 2, . . . and i=1, 2, 3, . . . ,m, by using the sampling period T=2π/ω s and the sample size N=kM where ω s is the sampling frequency, k is a positive integer and M is the fundamental period of sin(2ωnT); and processing means for processing said digitized sample signals s ti (n), and s ri (n) to derive the driving point impedances of said telephone subscriber's loop for each of said plurality of sinusoidal stimulus signals.