Apparatus and method for automatic mode selection in a communications receiver
First Claim
1. A receiver circuit, the circuit comprising:
- a circuit input terminal configured to receive an input data signal;
a circuit output terminal;
an input amplifier having input and output terminals, the input terminal of the input amplifier being coupled to the circuit input terminal;
a first comparator having first and second input terminals and an output terminal, the first input terminal being coupled to the output terminal of the input amplifier, the second input terminal being configured to receive a detection threshold voltage, and the output terminal of the first comparator being coupled to the circuit output terminal;
a filter;
a switch coupled in series with the filter between the first input terminal of the first comparator and a first power supply rail, the switch having a control terminal, wherein the switch is configured to switch to a first position responsive to receiving a low speed mode control signal at the control terminal of the switch, and further wherein the switch is configured to switch to a second position responsive to receiving a high speed mode control signal at the control terminal of the switch, and further wherein the switch is configured to switch to a second position responsive to receiving a high speed mode control signal at the control terminal of the switch; and
a mode selection circuit having input and output terminals, wherein the input terminal of the mode selection circuit is coupled to the output terminal of the first comparator and the output terminal of the mode selection circuit is coupled to the control terminal of the switch, and further wherein the mode selection circuit is configured to generate the low speed mode control signal responsive to a low speed data signal generated at the output of the first comparator responsive to the input data signal and generate the high speed mode control signal responsive to a low speed data signal generated at the output of the first comparator responsive to the input data signal.
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Accused Products
Abstract
A method and apparatus are shown for automatically adjusting a response bandwidth and input sensitivity of a communications receiver responsive to a frequency of a received data signal. The response bandwidth is adjusted by switching a low pass filter into a receive path of the receiver when the received data signal is a low speed data signal and switching the low pass filter out of the receive path when the received data signal is a high speed data signal. The input sensitivity is adjusted by either changing a detection threshold of a comparator in the receive path or varying a gain of an input amplifier in the receive path. The high speed data signal is discerned when the low pass filter limits the response bandwidth of the receiver by a mode selection circuit which examines the duration of multiple pulses in a pulse train in the received data signal.
42 Citations
35 Claims
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1. A receiver circuit, the circuit comprising:
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a circuit input terminal configured to receive an input data signal; a circuit output terminal; an input amplifier having input and output terminals, the input terminal of the input amplifier being coupled to the circuit input terminal; a first comparator having first and second input terminals and an output terminal, the first input terminal being coupled to the output terminal of the input amplifier, the second input terminal being configured to receive a detection threshold voltage, and the output terminal of the first comparator being coupled to the circuit output terminal; a filter; a switch coupled in series with the filter between the first input terminal of the first comparator and a first power supply rail, the switch having a control terminal, wherein the switch is configured to switch to a first position responsive to receiving a low speed mode control signal at the control terminal of the switch, and further wherein the switch is configured to switch to a second position responsive to receiving a high speed mode control signal at the control terminal of the switch, and further wherein the switch is configured to switch to a second position responsive to receiving a high speed mode control signal at the control terminal of the switch; and a mode selection circuit having input and output terminals, wherein the input terminal of the mode selection circuit is coupled to the output terminal of the first comparator and the output terminal of the mode selection circuit is coupled to the control terminal of the switch, and further wherein the mode selection circuit is configured to generate the low speed mode control signal responsive to a low speed data signal generated at the output of the first comparator responsive to the input data signal and generate the high speed mode control signal responsive to a low speed data signal generated at the output of the first comparator responsive to the input data signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A receiver circuit, the circuit comprising:
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a circuit input terminal configured to receive an input data signal; a circuit output terminal; an input amplifier having input and output terminals, the input terminal of the input amplifier being coupled to the circuit input terminal; a first comparator having first and second input terminals and an output terminal, the first input terminal being coupled to the output terminal of the input amplifier, the second input terminal being configured to receive a detection threshold voltage, and the output terminal of the first comparator being coupled to the circuit output terminal; a filter; a switch coupled in series with the filter between the output terminal of the input amplifier and a first power supply rail, the switch having a control terminal, wherein the switch is configured to switch to a first position responsive to receiving a low speed mode control signal at the control terminal of the switch, and further wherein the switch is configured to switch to a second position responsive to receiving a high speed mode control signal at the control terminal of the switch, and further wherein the switch is configured to switch to a second position responsive to receiving a high speed mode control signal at the control terminal of the switch; and a mode selection circuit having input and output terminals, wherein the input terminal of the mode selection circuit is coupled to the output terminal of the first comparator and the output terminal of the mode selection circuit is coupled to the control terminal of the switch, and further wherein the mode selection circuit is configured to generate the low speed mode control signal responsive to a low speed data signal generated at the output of the first comparator responsive to the input data signal and generate the high speed mode control signal responsive to a high speed data signal generated at the output of the first comparator responsive to the input data signal, and where the mode selection circuit further includes; a timer configured to receive the data signal generated at the output of the comparator and generate a timing signal responsive to each pulse in the data signal that corresponds to the duration of each pulse, a second comparator having first and second input terminals and an output terminal, wherein the first input terminal of the second comparator is configured to receive the timing signal generated by the timer and the second input terminal is configured to receive a first reference value, the comparator being configured to output a timer signal having a first timer value corresponding to a low speed pulse and a second timer value corresponding to a high speed pulse, a storage register configured to store the timer signal responsive to each pulse in the data signal, where the storage register is further configured to store the timer signal for three sequential pulses in the data signal, and a combinational circuit configured to receive the timer signal stored in the storage register and, responsive thereto, output the low speed mode control signal responsive to the first timer value and output the high speed mode control signal responsive to the second timer value, where the combinational circuit is further configured to output the low speed mode control signal when the timer signal stored for a first one of the three sequential pulses is the first timer value and the timer signal stored for a second one of the three sequential pulses is the second timer value, and further wherein the combinational circuit is configured to output the high speed mode control signal when the timer signal stored for the first one of the three sequential pulses is the second timer value and the timer signal stored for a third one of the three sequential pulses is the second timer value; a third comparator having first and second input terminals and an output terminal, wherein the first input terminal of the third comparator is configured to receive the timing signal generated by the timer and the second input terminal is configured to receive a second reference value, the comparator being configured to output a hold signal, wherein the second reference value is smaller in magnitude than the first reference value; a latch interposed between the circuit input terminal and the circuit output terminal wherein an output value of the latch is set when the data signal is a logical high value and the hold signal is a logical low value and wherein the output value of the latch is reset when the data signal is a logical low value; and the timer is further configured to decrease the timing value at a predetermined rate responsive to a falling edge of each pulse in the data signal. - View Dependent Claims (12, 13, 14)
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15. A method for receiving high and low speed signals in a receiver, the method comprising the steps:
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providing a receive path configured to receive an input data signal, wherein the input data signal includes one of the high speed signal and the low speed signal; comparing the input data signal to a detection threshold voltage in order to produce a demodulated data signal; setting a receive response bandwidth of the receive path to a first bandwidth level responsive to a low speed mode control signal and to a second bandwidth level responsive to a high speed mode control signal, wherein the second bandwidth level is greater than the first bandwidth level; generating the low speed mode control signal responsive to the low speed signal; and generating the high speed mode control signal responsive to the high speed signal. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A communications receiver, the receiver comprising:
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amplifier means for receiving an input data signal and amplifying the input data signal to produce an amplified data signal; demodulating means for transforming the amplified data signal into a demodulated data signal; filtering means for filtering the amplified data signal; switching means coupled in series with the filtering means for activating the filtering means responsive to a low speed mode signal and deactivating the filtering means responsive to a high speed mode signal; and mode selection means for monitoring the demodulated data signal and, responsive to a low speed pulse train in the demodulated data signal, generating the low speed mode signal and, responsive to a high speed pulse train in the demodulated data signal, generating the high speed mode signal. - View Dependent Claims (30, 31, 32, 33, 34, 35)
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Specification