US3887775A
Expired / Lapsed
US
⏱️ 0.0 years remaining
System for measuring group delay in signal transmission
Assignee: Italtel SpA
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Filing: 1973-10-31
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Granted: 1975-06-03
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Expires: 1993-10-31
Abstract
Abstract To measure the phase shift experienced by a selected carrier frequency (measuring frequency fM) relative to a standard carrier frequency (reference frequency fR) on passing through a test object such as a four-terminal network, the two carriers are alternately transmitted through that test object under the control of a switching signal (commutation frequency fc) while being amplitude-modulated by a common modulating frequency fm. At the receiving end, the detected carrier envelope of the incoming test wave is fed in parallel to an attenuation detector MA with an input filter F2 selecting the commutation frequency fc, a phase discriminator MR with an input filter F3 selecting the modulating frequency fm, and a synchronizing circuit SR with an input filter F4 suppressing the modulating frequency fm in cascade with another filter F9 passing a higher characteristic frequency fr which is supermodulated upon the reference frequency in the final cycle of modulating frequency fm just before the switchover. The phase discriminator MR comprises a zero-crossing detector ZCD delivering a measuring square wave x of mean frequency fm to a phase comparator RF which is part of a phaselocking loop including a voltage-responsive local oscillator VCX; the latter, through a frequency divider, supplies the comparator with a reference square wave of like frequency. The phase difference of the two square waves is measured by the amplitude of a sine wave of frequency fm derived from two pulse trains a, r in the comparator output. The rectified but undemodulated carrier frequencies of the test wave are delivered to an analog frequency indicator PX and to a digital frequency discriminator MF.
Inventors
- 👤 Nicola Montefusco
- 👤 Alfredo Barlucchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 18:39
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/46; H04B3/462
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
237 words
A system for measuring the relative phase shift between a selected carrier frequency fM and a standard carrier frequency fR on passing through a test object, said carrier frequencies being amplitude-modulated by a common modulating frequency fm and being alternately transmitted through said test object under the control of a switching signal with a commutation frequency fc, comprising: a receiver for said carrier frequencies provided with an amplitude demodulator for detecting a carrier envelope with a frequency component of said modulating frequency fm undergoing two opposite phase shifts during a switching cycle 1/fc; a phase discriminator connected to the output of said amplitude demodulator and including zero-crossing detector for deriving from said envelope a measuring square wave in phase with said frequency component thereof; a phase-locking loop in said phase discriminator including a tunable oscillation generator, wave-shaping means for deriving a reference square wave of frequency fm from the output of said oscillation generator, and a phase comparator receiving said measuring and reference square waves for producing a control signal proportional to the mean phase difference between said square waves to tune said oscillation generator with stabilization of the phase of said reference square wave at the mean phase of said measuring square wave; and output means in said phase discriminator for deriving from said phase comparator a voltage proportional to the absolute phase difference between said square waves as a measure of said relative phase shift.
Claim 2
Independent Claim
237 words
A system for measuring the relative phase shift between a selected carrier frequency fM and a standard carrier frequency fR on passing through a test object, said carrier frequencies being amplitude-modulated by a common modulating frequency fm and being alternately transmitted through said test object under the control of a switching signal with a commutation frequency fc, comprising: a receiver for said carrier frequencies provided with an amplitude demodulator for detecting a carrier envelope with a frequency component of said modulating frequency fm undergoing two opposite phase shifts during a switching cycle 1/fc; a phase discriminator connected to the output of said amplitude demodulator and including zero-crossing detector for deriving from said envelope a measuring square wave in phase with said frequency component thereof; a phase-locking loop in said phase discriminator including a tunable oscillation generator, wave-shaping means for deriving a reference square wave of frequency fm from the output of said oscillation generator, and a phase comparator receiving said measuring and reference square waves for producing a control signal proportional to the mean phase difference between said square waves to tune said oscillation generator with stabilization of the phase of said reference square wave at the mean phase of said measuring square wave; and output means in said phase discriminator for deriving from said phase comparator a voltage proportional to the absolute phase difference between said square waves as a measure of said relative phase shift.
Claim 3
Independent Claim
237 words
A system for measuring the relative phase shift between a selected carrier frequency fM and a standard carrier frequency fR on passing through a test object, said carrier frequencies being amplitude-modulated by a common modulating frequency fm and being alternately transmitted through said test object under the control of a switching signal with a commutation frequency fc, comprising: a receiver for said carrier frequencies provided with an amplitude demodulator for detecting a carrier envelope with a frequency component of said modulating frequency fm undergoing two opposite phase shifts during a switching cycle 1/fc; a phase discriminator connected to the output of said amplitude demodulator and including zero-crossing detector for deriving from said envelope a measuring square wave in phase with said frequency component thereof; a phase-locking loop in said phase discriminator including a tunable oscillation generator, wave-shaping means for deriving a reference square wave of frequency fm from the output of said oscillation generator, and a phase comparator receiving said measuring and reference square waves for producing a control signal proportional to the mean phase difference between said square waves to tune said oscillation generator with stabilization of the phase of said reference square wave at the mean phase of said measuring square wave; and output means in said phase discriminator for deriving from said phase comparator a voltage proportional to the absolute phase difference between said square waves as a measure of said relative phase shift.
Claim 4
Independent Claim
237 words
A system for measuring the relative phase shift between a selected carrier frequency fM and a standard carrier frequency fR on passing through a test object, said carrier frequencies being amplitude-modulated by a common modulating frequency fm and being alternately transmitted through said test object under the control of a switching signal with a commutation frequency fc, comprising: a receiver for said carrier frequencies provided with an amplitude demodulator for detecting a carrier envelope with a frequency component of said modulating frequency fm undergoing two opposite phase shifts during a switching cycle 1/fc; a phase discriminator connected to the output of said amplitude demodulator and including zero-crossing detector for deriving from said envelope a measuring square wave in phase with said frequency component thereof; a phase-locking loop in said phase discriminator including a tunable oscillation generator, wave-shaping means for deriving a reference square wave of frequency fm from the output of said oscillation generator, and a phase comparator receiving said measuring and reference square waves for producing a control signal proportional to the mean phase difference between said square waves to tune said oscillation generator with stabilization of the phase of said reference square wave at the mean phase of said measuring square wave; and output means in said phase discriminator for deriving from said phase comparator a voltage proportional to the absolute phase difference between said square waves as a measure of said relative phase shift.
Claim 5
Dependent Claim
33 words
A system as defined in claim 1 wherein said oscillation generator has an operating frequency equal to a multiple of said modulating frequency Fm, said wave-shaping means including a multistage binary frequency divider.
Claim 6
Dependent Claim
36 words
A system as defined in claim 2 wherein said oscillation generator comprises a voltage-controlled local oscillator, a source of constant frequency and mixer means connected to receive the outputs of said local oscillator and said source.
Claim 7
Dependent Claim
33 words
A system as defined in claim 2 wherein said output means includes a normally blocked read-out circuit, further comprising a gating-pulse generator for said read-out circuit with input connections to said frequency divider.
Claim 8
Dependent Claim
52 words
A system as defined in claim 1 wherein said phase comparator comprises a logic network with a first output energized by said measuring square wave in the absence of said reference square wave and with a second output energized by said reference square wave in the absence of said measuring square wave.
Claim 9
Independent Claim
276 words
A system for measuring the relative phase shift between a selected carrier frequency fM and a standard carrier frequency fR on passing through a test object, said carrier frequencies being amplitude-modulated by a common modulating frequency fm and being alternately transmitted through said test object under the control of a switching signal with a commutation frequency fc, comprising: a receiver for said carrier frequencies provided with an amplitude demodulator for detecting a carrier envelope with a frequency component of said modulating frequency fm undergoing two opposite phase shifts during a switching cycle 1/fc; a phase discriminator connected to the output of said amplitude demodulator and including conversion means for deriving from said envelope a measuring square wave in phase with said frequency component thereof; a phase-locking loop in said phase discriminator including a tunable oscillation generator with an operating frequency equal to a multiple of said modulating frequency fm, wave-shaping means including a multistage binary frequency divider for deriving a reference square wave of frequency fm from the output of said oscillation generator, and a phase comparator receiving said measuring and reference square waves for producing a control signal proportional to the mean phase difference between said square waves to tune said oscillation generator with stabilization of the phase of said reference square wave at the mean phase of said measuring square wave; output means including a normally blocked read-out circuit in said phase discriminator for deriving from said phase comparator a voltage proportional to the absolute phase difference between said square waves as a measure of said relative phase shift; and a gating-pulse generator for said read-out circuit with input connections to said frequency divider.
Claim 10
Independent Claim
276 words
A system for measuring the relative phase shift between a selected carrier frequency fM and a standard carrier frequency fR on passing through a test object, said carrier frequencies being amplitude-modulated by a common modulating frequency fm and being alternately transmitted through said test object under the control of a switching signal with a commutation frequency fc, comprising: a receiver for said carrier frequencies provided with an amplitude demodulator for detecting a carrier envelope with a frequency component of said modulating frequency fm undergoing two opposite phase shifts during a switching cycle 1/fc; a phase discriminator connected to the output of said amplitude demodulator and including conversion means for deriving from said envelope a measuring square wave in phase with said frequency component thereof; a phase-locking loop in said phase discriminator including a tunable oscillation generator with an operating frequency equal to a multiple of said modulating frequency fm, wave-shaping means including a multistage binary frequency divider for deriving a reference square wave of frequency fm from the output of said oscillation generator, and a phase comparator receiving said measuring and reference square waves for producing a control signal proportional to the mean phase difference between said square waves to tune said oscillation generator with stabilization of the phase of said reference square wave at the mean phase of said measuring square wave; output means including a normally blocked read-out circuit in said phase discriminator for deriving from said phase comparator a voltage proportional to the absolute phase difference between said square waves as a measure of said relative phase shift; and a gating-pulse generator for said read-out circuit with input connections to said frequency divider.
Claim 11
Dependent Claim
83 words
A system as defined in claim 6 wherein said input connections include a first connection from a final stage output of said divider and a second connection from a preceding stage output of said divider, said gating-pulse generator comprising first coincidence means tied to said input connections, second coincidence means with two inputs connected via respective branch leads to the output of said first coincidence means, and delay means in one of said branch leads for establishing the length of a gating pulse.
Claim 12
Dependent Claim
54 words
A system as defined in claim 6, further comprising an attenuation detector connected in parallel with said phase discriminator to the output of said amplitude demodulator, said attenuation detector including filter means selectively passing said commutation frequency fc and another read-out circuit in the output of said filter means connected to said gating-pulse generator.
Claim 13
Dependent Claim
20 words
A system as defined in claim 8 wherein said receiver includes logarithmic amplitude-compression means in cascade with said demodulating means.
Claim 14
Dependent Claim
46 words
A system as defined in claim 6 wherein said amplitude demodulator includes a low-pass filter cutting off said carrier frequencies, further comprising an anAlog-frequency indicator connected to said receiver upstream of said low-pass filter, said indicator including an additional read-out circuit connected to said gating-pulse generator.
Claim 15
Dependent Claim
53 words
A system as defined in claim 10 wherein said indicator includes squaring and pulse-shaping means for deriving from said carrier frequencies a train of constant-width pulses with cadences alternating between fR and fM, and filter means for converting said train into a sine wave of frequency fc delivered to said additional read-out circuit.
Claim 16
Dependent Claim
20 words
A system as defined in claim 11, further comprising phase-registration means connected to the outputs of both said read-out circuits.
Claim 17
Independent Claim
281 words
A system for measuring the relative phase shift between a selected carrier frequency fM and a standard carrier frequency fR on passing through a test object, said carrier frequencies being amplitude-modulated by a common modulating frequency fm and being alternately transmitted through said test object under the control of a switching signal with a commutation frequency fc, comprising: a receiver for said carrier frequencies provided with an amplitude demodulator for detecting a carrier envelope with a frequency component of said modulating frequency fm undergoing two opposite phase shifts during a switch cycle 1/fc; a phase discriminator connected to the output of said amplitude demodulator and including conversion means for deriving from said envelope a measuring square wave in phase with said frequency component thereof; a phase-locking loop in said phase discriminator including a tunable oscillation generator, wave-shaping means for deriving a reference square wave of frequency fm from the output of said oscillation generator, and a phase comparator receiving said measuring and reference square waves for producing a control signal proportional to the mean phase difference between said square waves to tune said oscillation generator with stabilization of the phase of said reference square wave at the mean phase of said measuring square wave, said phase comparator comprising a logic network with a first output energized by said measuring square wave in the absence of said reference square wave and with a second output energized by said reference square wave in the absence of said measuring square wave; and output means in said phase discriminator for deriving from said phase comparator a voltage proportional to the absolute phase difference between said square waves as a measure of said relative phase shift.
Claim 18
Independent Claim
281 words
A system for measuring the relative phase shift between a selected carrier frequency fM and a standard carrier frequency fR on passing through a test object, said carrier frequencies being amplitude-modulated by a common modulating frequency fm and being alternately transmitted through said test object under the control of a switching signal with a commutation frequency fc, comprising: a receiver for said carrier frequencies provided with an amplitude demodulator for detecting a carrier envelope with a frequency component of said modulating frequency fm undergoing two opposite phase shifts during a switch cycle 1/fc; a phase discriminator connected to the output of said amplitude demodulator and including conversion means for deriving from said envelope a measuring square wave in phase with said frequency component thereof; a phase-locking loop in said phase discriminator including a tunable oscillation generator, wave-shaping means for deriving a reference square wave of frequency fm from the output of said oscillation generator, and a phase comparator receiving said measuring and reference square waves for producing a control signal proportional to the mean phase difference between said square waves to tune said oscillation generator with stabilization of the phase of said reference square wave at the mean phase of said measuring square wave, said phase comparator comprising a logic network with a first output energized by said measuring square wave in the absence of said reference square wave and with a second output energized by said reference square wave in the absence of said measuring square wave; and output means in said phase discriminator for deriving from said phase comparator a voltage proportional to the absolute phase difference between said square waves as a measure of said relative phase shift.
Claim 19
Dependent Claim
139 words
A system as defined in claim 13 wherein said output means includes a pulse counter connected to said wave-shaping means for stepping by said reference square wave, said pulse counter generating two timing pulses during respective halves of a switching cycle, gating means connected to said logic network for passing a first phasing pulse of one polarity for every energization of said first output in the presence of one of said timing pulses and for passing a second phasing pulse of opposite polarity for every energization of said second output in the presence of the other of said timing pulses, and integrating means for converting said phasing pulses into a sinusoidal oscillation of frequency fc, the width of said phasing pulses and consequently the amplitude of said sinusoidal oscillation being proportional to the phase difference between said square waves.
Claim 20
Dependent Claim
102 words
A system as defined in claim 14 wherein said standard carrier frequency fR is additionally modulated with a characteristic frequency fr >> fm in a predetermined period of its modulation by said frequency fm, further comprising synchronizing means connected in parallel with said phase discriminator to the output of said demodulating means, said synchronizing means including a recovery circuit for said characteristic frequency fr and a logic circuit in tHe output of said recovery circuit for deriving one resetting pulse per switching cycle from said characteristic frequency, said pulse counter being connected to said logic circuit for receiving said resetting pulse therefrom.
Claim 21
Dependent Claim
62 words
A system as defined in claim 15 wherein said synchronizing means further comprises a band-stop filter upstream of said recovery circuit for eliminating said modulating frequency fm, said recovery circuit including a band-pass filter transmitting said frequency fr and harmonics-suppressor means upstream of said band-pass filter for blocking harmonics of said commutation frequency fc in the pass band of said band-pass filter.
Claim 22
Dependent Claim
72 words
A system as defined in claim 16 wherein said harmonics-suppressor means comprises a differentiation circuit in the output of said band-stop filter, a saturable amplifier overdriven by the output of said differentiation circuit at the instants of switchover between said carrier frequencies, and a clipping circuit between said amplifier and said band-stop filter, said characteristic frequency fr having a wave shape sufficiently unaffected by said differentiation circuit to clear said clipping circuit.
Claim 23
Dependent Claim
65 words
A system as defined in claim 15 wherein said logic circuit comprises a source of counting pulses with a repetition frequency substantially higher than said characteristic frequency fr, counting means for said counting pulses, and bistable means settable upon attainment of a predetermined count by said counting means in response to the arrival of said characteristic frequency and resettable by an immediately following counting pulse.
Claim 24
Dependent Claim
111 words
A system as defined in claim 15 wherein said amplitude demodulator includes a low-pass filter cutting off said carrier frequencies, further comprising a digital frequency discriminator connected to said receiver upstream of said low-pass filter, said frequency discriminator including time-base means responsive to said resetting pulse for measuring two identical time intervals during respective halves of a switching cycle, a first and a second gating circuit alternately unblocked during said time interval for respectively passing a succession of cycles of said carrier frequencies fM and fR, first and second counting means for the cycles of the carrier frequencies so passed, and storage means for the counts of the passed carrier cycles.
Claim 25
Dependent Claim
50 words
A system as defined in claim 19 wherein said time-base means comprises a chain of binary frequency-divider stages, a source of stepping pulses for said divider stages, a pair of flip-flops, and logic means connecting certain of said divider stages to said flip-flops for periodically changing their state of conductivity.
Claim 26
Dependent Claim
34 words
A system as defined in claim 14 wherein said output means further includes voltage-responsive oscillator means controlled by the amplitude of said sinusoidal oscillation to generate an output frequency varying with said phase difference.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-02 | 1978-12-02 | 1979-06-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-02 | 1982-12-02 | 1983-06-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-02 | 1986-12-02 | 1987-06-03 | $7700.00 | Window Closed / Lapsed |