Low voltage IC for voice operated transceiver

• US 5,193,217 A
• Filed: 04/23/1990
• Issued: 03/09/1993
• Est. Priority Date: 04/23/1990
• Status: Expired due to Term

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Chan, Man, Lin, Chi M., Lunn, Gerald K.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): URBAN, EDWARD F
• Application Number:
  US07/513,453
• Time in Patent Office: 1,051 Days
• Field of Search: 459/78, 459/79, 459/82, 459/83, 459/89, 459/354, 459/355, 381/58, 381/46
• US Class Current: 455/79
• CPC Class Codes: H04B 1/46 by voice-frequency signals; by pilot signals

Abstract

A portable transceiver with a transmit/receive switch which includes an audio amplifier, level detector and comparator all direct coupled and included on a single integrated chip. The comparator includes one input that has a slow attack time and a fast decay time for differentiating between slow changing background noise and fast bursts of voice so that the transceiver is voice operated.

Claims

1. A portable transceiver comprising:

a transmitter;

a receiver; and

a transmit/receive switch coupled to the transmitter and having a microphone operatively connected thereto, the transmit/receive switch being constructed to receive input signals from the microphone and to turn on the transmitter only when the input signals include a voice signal, the transmit/receive switch including

and audio amplifier coupled to receive input signals from the microphone and including variable circuitry providing a variable gain and bandwidth,

a level detector connected to the audio amplifier for providing an output level signal corresponding to the level of input signals applied to the audio amplifier,

a level adjusting circuit coupled to the level detector and the audio amplifier and providing automatic level control and including variable circuitry providing variable level detecting attack time and variable attenuation,

a noise monitoring circuit coupled to receive the output level signal from the level detector and including variable circuitry providing a variable attack and decay time connected to produce an output signal from the noise monitoring circuit when a voice signal occurs in the input signal of the audio amplifier,

a comparator circuit having two inputs and coupled to receive the output level signal from the level detector at one input and the output signal from the noise monitoring circuit at the other input,

the comparator circuit further including a trigger level and a circuit for adjusting the trigger level, the comparator being connected to supply a switching signal to the transmitter and including variable circuitry for adjusting the trigger level of the comparator,

the audio amplifier, the level detector, the level adjusting circuit, the noise monitoring circuit, and the comparator circuit all being direct coupled circuits and all being formed as an integrated circuit which operates in a range below approximately 1.8 volts.on a single semiconductor chip, and

no more than eight external connections to the integrated circuit connecting the variable circuitry included in the audio amplifier, the variable circuitry included in the level adjusting circuit, the variable circuitry included in the noise monitoring circuit, and the variable circuitry included in the trigger level adjusting circuit external to the integrated circuit, providing the coupling between the microphone and the audio amplifier and the coupling between the audio amplifier and the transmitter and, for connecting power and reference supplies to the integrated circuit.

2. The portable transceiver as claimed in claim 1 wherein the audio amplifier, the level adjusting circuit and the noise monitoring circuit each include differentially connected transistor stages with constant current sources which operate with a V_ce below approximately 0.1 volts.

3. A low voltage operated integrated circuit for controlling transceiver transmit/receive switching, having no more that eight external connecting pads, comprising:

an audio amplifier with a first external connecting pad adapted to receive input signals from a microphone and have variable attenuation circuitry attached thereto and second and third external connecting pads adapted to supply audio to a transceiver and to have connected thereto circuitry providing a variable gain and bandwidth for the audio amplifier;

a level detector connected to the audio amplifier for providing an output level signal corresponding to the level of input signals applied to the audio amplifier;

a level adjusting circuit coupled to the level detector and the audio amplifier and providing automatic level control with a fourth external connecting pad adapted to have connected thereto circuitry providing variable level detecting attack time;

a noise monitoring circuit coupled to receive the output level signal from the level detector with a fifth external connecting pad adapted to have connected thereto circuitry providing a variable attack and decay time connected to produce an output signal from the noise monitoring circuit when a voice signal occurs in the input signal of the audio amplifier;

a comparator circuit having two inputs and coupled to receive the output level signal from the level detector at one input and the output signal from the noise monitoring circuit at the other input,

the comparator circuit further including trigger level adjusting circuitry having a sixth external connecting pad adapted to have connected thereto variable external switching level adjusting apparatus and to supply a switching signal to the transmitter;

seventh and eighth external connecting pads included in the integrated circuit and adapted to have power and reference supplies attached thereto; and

the audio amplifier, the level detector, the level adjusting circuit, the noise monitoring circuit, and the comparator circuit all being direct coupled circuits and all being formed as an integrated circuit which operates in a range below approximately 1.8 volts.on a single semiconductor chip.

4. The low voltage operated integrated circuit for controlling transceiver transmit/receive switching as claimed in claim 3 wherein the audio amplifier, the level adjusting circuit and the noise monitoring circuit each include differentially connected transistor stages with constant sources which operate with a V_ce below approximately 0.1 volts.

5. A portable transceiver comprising:

a transmitter;

a receiver; and

a transmit/receive switch coupled to the transmitter and having a microphone operatively connected thereto, the transmit/receive switch being constructed to receive input signals from the microphone and to switch on the transmitter only when the input signals include a voice signal, the transmit/receive switch including an integrated circuit with no more than eight external connections to the integrated circuit with the microphone and variable attenuation circuitry connected to a first of the external connections, circuitry providing a variable gain and bandwidth and supplying an audio output to the transceiver connected to second and third external connections, circuitry providing variable level detecting attack time connected to a fourth of the external connections, circuitry providing a variable attack and decay time connected to produce an output signal when a voice signal is applied to the microphone connected to a fifth of the external connections, a sixth external connection connected to supply a switching signal to the transmitter and having attached thereto circuitry for adjusting the switching level, and seventh and eighth external connecting pads for connecting power and reference supplies to the integrated circuit.