Threshold Technology, Inc.

Gene Grunza

Marvin B Herscher

An apparatus is disclosed for receiving and processing transmitted electromagnetic waves, for example transmitted radio signals which contain audio information including recognizable speech information. In accordance with the invention, there are provided first and second spaced antennas. Switching means are provided for coupling either the first or the second antenna to a common channel. Signal processing means are provided for processing the signals on the common channel. Means are provided for comparing the signal on the common channel with a predetermined threshold condition and for generating a control signal in response to the comparison. Finally, means are provided for applying the control signal to the switching means to control selection of the first or second antenna. In one preferred embodiment of the invention, the comparator means comprises means for comparing the energy level of the signal at the common channel with a predetermined energy threshold. During operation, the antenna which is active at a particular time will remain active (i.e. coupled to the common channel) so long as the received radio frequency energy, at the characteristic transmission frequency, remains above the predetermined threshold level. If the level of received energy at this characteristic frequency falls below the predetermined threshold level (for example, by virtue of the antenna momentarily being in a multipath 'dead' spot), the comparator means will sense this condition and operate the switch such that the other antenna is coupled to the common channel and becomes active. In another form of the invention the signal processing means includes means for generating an automatic gain control (AGC) signal which depends upon the instantaneous level of the signal on the common channel. A signal derived from the AGC signal is compared with a threshold signal that depends upon a predetermined reference, and a control signal is generated when the signal derived from the AGC signal exceeds the threshold signal.

Receiving apparatus having a plurality of antennas

An apparatus for recognizing the occurrence of a command word within continuous speech, features an improved sequential processing of feature signals derived from the input speech: feature subsets are compared with previously stored subset signals to determine the time interval or boundary of command word candidates. The occurrence decision and indication of the command word is made from a comparison of a feature signal matrix versus a previously stored training matrix.

Apparatus for recognizing words from among continuous speech

An apparatus for signal-in-noise enhancement by useful-channel selection, includes automatic channel switching if words of a predetermined speech vocabulary are not detected within a predetermined interval. In accordance with the invention there are provided first and second parallel channels to which audio signals are applied. A channel selector, such as a voltage controlled switch, is responsive to a control signal for selecting the first or the second channel. A speech word recognition subsystem is provided and is responsive to the audio signals transmitted over the selected channel. The speech recognition subsystem determines the presence of speech-like sounds and generates a speech-indicative signal as a function thereof. Portions of the audio signals which occur during the speech-indicative signal are compared with the predetermined vocabulary to determine the probable occurrence of a word from among the predetermined vocabulary, and an occurrence indication signal is generated when a vocabulary word is detected. A control signal is generated in response to the output of the speech word recognition subsystem, the control signal being a function of the speech-indicative signal and the occurrence indication signal. In operation, the control signal is operative, in response to the presence of extraneous signals on a channel being utilized, to effect switching to the other channel. In the preferred embodiment, the speech recognition subsystem generates reject signals when the speech-indicative signal persists for a prescribed time without an occurrence indication occurring, and the control signal is generated in response to the reject signals.

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Blackwood, NJ, United States of America

Gene Grunza