EP0364383A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Half-duplex speakerphone
Assignee: Siemens Business Communication Systems Inc
•
Filing: 1989-09-12
•
Granted: —
•
Expires: 2009-09-12
Abstract
Abstract A half-duplex digital speakerphone (10) includes a control state machine which controls the selection of either a transmit or a receive audio path based upon a present state of the speakerphone and the magnitudes of three signal related variables associated with each path. The three variables for each path includes a signal power variable, a noise power variable and a worst-case echo variable. A change of state of the state machine results in the value of a variable gain within each of the paths being adjusted to optimize the transition time from the receive to the transmit state or from the transmit to the receive state. Also optimized is a change of state from an idle state to a transmit or receive state or from a transmit or receive state to the idle state. A change of state is accomplished in accordance with a smoothly varying, substantially Gaussian switching waveform which is selected to optimize the transition time between states while simultaneously minimizing audible side effects.
Inventors
- 👤 Ygal Arbel
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 23:52
CPC Classifications
H; H04; H04M; H04M9/00; H04M9/08; H04M9/085; H04B; H04B3/00; H04B3/02; H04B3/20; H04M9/10
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
153 words
A speakerphone including a transmit audio path for conveying a transmit signal including speech signals and a receive audio path for conveying a receive signal including speech signals, the speakerphone comprising: control means having a plurality of input signals and a plurality of output signals, a value of said output signals being a function of a value of said input signals, said output signals including at least a signal expressive of, when asserted, a transmit state, a signal expressive of, when assert ed, a receive state and a signal expressive of, when asserted, an idle state, said input signals including a first input signal having a value which is a function of: a transmit signal power estimate, a transmit audio path noise signal estimate and a transmit audio path echo signal estimate; and a receive signal power estimate, a receive audio path noise signal estimate and a receive audio path echo signal estimate.
Claim 2
Dependent Claim
153 words
A speakerphone including a transmit audio path for conveying a transmit signal including speech signals and a receive audio path for conveying a receive signal including speech signals, the speakerphone comprising: control means having a plurality of input signals and a plurality of output signals, a value of said output signals being a function of a value of said input signals, said output signals including at least a signal expressive of, when asserted, a transmit state, a signal expressive of, when assert ed, a receive state and a signal expressive of, when asserted, an idle state, said input signals including a first input signal having a value which is a function of: a transmit signal power estimate, a transmit audio path noise signal estimate and a transmit audio path echo signal estimate; and a receive signal power estimate, a receive audio path noise signal estimate and a receive audio path echo signal estimate.
Claim 3
Dependent Claim
107 words
A speakerphone as set forth in Claim 1 wherein said input signals further include: a second input signal having a value which is a function of the estimate of the power of the transmit signal and the estimate of the noise signal for the transmit audio path, the second signal indicating if the transmit audio path is conveying speech signals; and a third input signal having a value which is a function of the estimate of the power of the receive signal and the estimate of the noise signal for the receive audio path, the third signal indicating if the receive audio path is conveying speech signals.
Claim 4
Dependent Claim
30 words
A speakerphone as set forth in Claim 2 wherein said input signals further include: a fourth input signal which is expressive of whether said speakerphone is in a mute condition.
Claim 5
Dependent Claim
88 words
A speakerphone as set forth in Claim 2 wherein said second input signal is generated by means comprising: means for multiplying said transmit signal power estimate by a first multiplication factor to obtain a scaled transmit signal power estimate signal; means for subtracting from said scaled transmit signal power estimate signal said transmit audio path noise signal; and means for subtracting from said transmit signal power estimate signal a first subtracting means signal having a value which is related to a desired transmit signal signal to noise ratio.
Claim 6
Dependent Claim
88 words
A speakerphone as set forth in Claim 4 wherein said third input signal is generated by means comprising: means for multiplying said receive signal power estimate by a second multiplication factor to obtain a scaled receive signal power estimate signal; means for subtracting from said scaled receive signal power estimate signal said receive audio path noise signal; and means for subtracting from said receive signal power estimate signal a second subtracting means signal having a value which is related to a desired receive signal signal to noise ratio.
Claim 7
Dependent Claim
39 words
A speakerphone as set forth in Claim 5 wherein said first and said second multiplication factor are each equal to approximately 0.75 and wherein said first and said second subtracting means signals each have a value of approximately 0.00305.
Claim 8
Dependent Claim
42 words
A speakerphone as set forth in Claims anyone of 1-6 wherein said transmit signal power estimate signal and said receive signal power estimate signal are each generated by an envelope detection means having an associated rise time and an associated fall time.
Claim 9
Dependent Claim
25 words
A speakerphone as set forth in Claim 7 wherein said rise time is approximately one millisecond and wherein said fall time is approximately 28 milliseconds.
Claim 10
Dependent Claim
42 words
A speakerphone as set forth in Claim 1 wherein said transmit audio path echo estimate signal and said receive audio path echo estimate signal are each generated by an envelope detection means having an associated rise time and an associated fall time.
Claim 11
Dependent Claim
25 words
A speakerphone as set forth in Claim 9 wherein said rise time is approximately 0.25 millisecond and wherein said fall time is approximately 100 milliseconds.
Claim 12
Dependent Claim
84 words
A speakerphone as set forth in Claim 1 wherein said control means output signals further comprise a transmit audio path gain defining signal and a receive audio path gain defining signal and wherein said gain defining signals vary the gain of each of said transmit and said receive audio paths within a range of approximately 0 dB to less than approximately -50 dB when either said signal expressive of a transmit state is asserted or said signal expressive of a receive state is asserted.
Claim 13
Dependent Claim
51 words
A speakerphone as set forth in Claim 11 wherein said gain defining signals define the gain of said transmit audio path to be approximately -10 dB and the gain of said receive audio path to be less than approximately -40 dB when said signal expressive of an idle state is asserted.
Claim 14
Dependent Claim
32 words
A speakerphone as set forth in Claim 12 wherein said control means comprises means for generating said gain defining signals such that said gain defining signals each have a substantially Gaussian waveshape.
Claim 15
Independent Claim
310 words
A method of operating a half-duplex speakerphone which includes a transmit audio path for conveying a transmit signal including speech signals and a receive audio path for conveying a receive signal including speech signals, the method comprising the steps of: (a) generating a transmit signal power estimate, a transmit audio path noise signal estimate and a transmit audio path echo signal estimate; (b) generating a receive signal power estimate, a receive audio path noise signal estimate and a receive audio path echo signal estimate; (c) comparing the estimate of the power of the transmit signal against the estimate of the noise signal for the transmit audio path for generating a first signal for indicating if the transmit audio path is conveying speech signals; (d) comparing the estimate of the power of the receive signal against the estimate of the noise signal for the receive audio path for generating a second signal for indicating if the receive audio path is conveying speech signals; (e) comparing the generated transmit signal power estimate, the transmit audio path noise signal estimate and the transmit audio path echo signal estimate against the generated receive signal power estimate, the receive audio path noise signal estimate and the receive audio path echo signal estimate for generating a third signal for indicating if the speakerphone is in a transmit or a receive state; and (f) determining a next state of the speakerphone to be a transmit state wherein the transmit audio path is conveying speech signals, a receive state wherein the receive audio path is conveying speech signals, an idle state wherein neither the transmit audio path or the receive audio path is conveying speech signals or a present state, the determined next state being a function at least of the present state of the speakerphone and the values of the first, the second and the third signals.
Claim 16
Independent Claim
310 words
A method of operating a half-duplex speakerphone which includes a transmit audio path for conveying a transmit signal including speech signals and a receive audio path for conveying a receive signal including speech signals, the method comprising the steps of: (a) generating a transmit signal power estimate, a transmit audio path noise signal estimate and a transmit audio path echo signal estimate; (b) generating a receive signal power estimate, a receive audio path noise signal estimate and a receive audio path echo signal estimate; (c) comparing the estimate of the power of the transmit signal against the estimate of the noise signal for the transmit audio path for generating a first signal for indicating if the transmit audio path is conveying speech signals; (d) comparing the estimate of the power of the receive signal against the estimate of the noise signal for the receive audio path for generating a second signal for indicating if the receive audio path is conveying speech signals; (e) comparing the generated transmit signal power estimate, the transmit audio path noise signal estimate and the transmit audio path echo signal estimate against the generated receive signal power estimate, the receive audio path noise signal estimate and the receive audio path echo signal estimate for generating a third signal for indicating if the speakerphone is in a transmit or a receive state; and (f) determining a next state of the speakerphone to be a transmit state wherein the transmit audio path is conveying speech signals, a receive state wherein the receive audio path is conveying speech signals, an idle state wherein neither the transmit audio path or the receive audio path is conveying speech signals or a present state, the determined next state being a function at least of the present state of the speakerphone and the values of the first, the second and the third signals.
Claim 17
Dependent Claim
62 words
A method as set forth in Claim 14 wherein if the next state of the speakerphone is determined to be other than the present state further includes a step of varying a receive audio path gain signal and a transmit audio path gain signal such that a total loop gain of the transmit and the receive audio paths remains less than unity.
Claim 18
Dependent Claim
63 words
A method as set forth in Claim 15 wherein if the next state of the speakerphone is determined to be transmit and the present state is receive or idle the gain of the transmit audio path is varied until it equals approximately zero dB and the gain of the receive audio path is simultaneously varied until it equals less than approximately -50 dB.
Claim 19
Dependent Claim
63 words
A method as set forth in Claim 16 wherein if the next state of the speakerphone is determined to be receive and the present state is transmit or idle the gain of the receive audio path is varied until it equals approximately zero dB and the gain of the transmit audio path is simultaneously varied until it equals less than approximately -50 dB.
Claim 20
Dependent Claim
63 words
A method as set forth in Claim 15 wherein if the next state of the speakerphone is determined to be idle and the present state is transmit or receive the gain of the receive audio path is varied until it equals less than approximately -40 dB and the gain of the transmit audio path is simultaneously varied until it equals approximately -10 dB.
Claim 21
Dependent Claim
30 words
A method as set forth in Claim 17 wherein the gains of the transmit and receive audio paths are varied over an interval of time equal to approximately 20 milliseconds.
Claim 22
Dependent Claim
30 words
A method as set forth in Claim 18 wherein the gains of the transmit and receive audio paths are varied over an interval of time equal to approximately 2 seconds.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.