Method of and apparatus for controlling modulation of digital signals in frequency-modulated transmissions
First Claim
1. A method of controlling data flow between a digital data device and an analog communication device which includes a voltage controlled oscillator circuit, said method including receiving digital data messages, generating an analog signal modulated with said digital data messages and applying said modulated analog signal to the oscillator circuit of the analog communication device, said method further comprising:
- storing a digitally coded value equivalent of a quiescent bias signal level which when applied to the oscillator circuit will cause the oscillator circuit to operate at a channel frequency;
generating a high and a low modulation analog signal level with respect to said stored digitally coded value equivalent of said quiescent bias signal level; and
applying to the oscillator circuit said analog signal modulated with said high and low modulated analog signal levels in accordance respectively with high and low data signals of said received digital data messages.
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Accused Products
Abstract
An interface device interacts between a digital data terminal and a frequency modulated analog transceiver module to control data flow between the digital data terminal and the transceiver module and to adapt the transceiver module to transmit digital data signals and to communicate messages containing digital signals to the digital data terminal. The interface circuit includes a digitally implemented signal shaping circuit which samples an analog quiescent state bias signal level of a voltage controlled oscillator circuit of the transceiver module. The signal shaping circuit samples and converts the sampled quiescent bias signal level to an equivalent digital data value. The digital equivalent value is increased by and decreased by a predetermined deviation value, thereby generating equivalent values of high and low modulation bias voltage levels. The interface device includes a programmable memory for storing a number of reference values which allow the interface device to be configured to normalize data signals and control sequences in accordance with operating characteristics of any one of a number of available transceiver modules. The stored reference values control timing sequences for initiating and shutting down a transmit cycle, for storing predetermined maximum deviation values for the modulation bias signal of transmitted data messages, and for demodulating received signals.
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Citations
27 Claims
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1. A method of controlling data flow between a digital data device and an analog communication device which includes a voltage controlled oscillator circuit, said method including receiving digital data messages, generating an analog signal modulated with said digital data messages and applying said modulated analog signal to the oscillator circuit of the analog communication device, said method further comprising:
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storing a digitally coded value equivalent of a quiescent bias signal level which when applied to the oscillator circuit will cause the oscillator circuit to operate at a channel frequency; generating a high and a low modulation analog signal level with respect to said stored digitally coded value equivalent of said quiescent bias signal level; and applying to the oscillator circuit said analog signal modulated with said high and low modulated analog signal levels in accordance respectively with high and low data signals of said received digital data messages. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of controlling data flow between a digital data device and an analog communication device which includes a voltage controlled oscillator circuit, said method including receiving digital data messages, generating an analog signal modulated with said digital data messages and applying said modulated analog signal to the oscillator circuit of the analog communication device, said method further comprising;
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storing a value equivalent of a quiescent bias signal level which when applied to the oscillator circuit will cause the oscillator to operate at a channel frequency; adding a deviation value to said stored quiescent bias signal level value to obtain a high modulation value; subtracting said deviation value from said stored quiescent bias signal level value to obtain a low modulation value; generating high and low modulation analog signal levels which correspond to said high and low modulation values, respectively; and applying to the oscillator circuit said analog signal modulated with said high and low modulation signal levels in accordance with high and low digital data signals of said received digital messages.
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12. An interface device for controlling data flow between a digital data device which includes a message source for providing data messages in digital format and an analog communication device which includes a voltage controlled oscillator circuit, said interface device including means for receiving said digital data messages and for generating and applying an analog signal modulated with said digital data messages to the oscillator circuit of the analog communication device, said interface device comprising;
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means for storing a digitally coded quiescent bias value corresponding to a quiescent bias signal level which when applied to the oscillator circuit will cause the oscillator circuit to operate at a channel frequency; means for generating a high and a low modulation analog signal level with respect to said stored digitally coded quiescent bias signal value; and means for applying to the oscillator circuit said analog signal modulated with said high and low modulation analog signal levels in accordance respectively with high and low digital data signals of said received digital data messages. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An interface device for controlling bidirectional data transfer between a digital data device and a frequency modulated transceiver module having a voltage controlled crystal oscillator circuit operable at a predetermined channel frequency in response to a quiescent voltage level applied to the oscillator circuit, said interface device comprising;
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timing control means for controlling an initiation, a duration, and a shut down of a transmit cycle of the transceiver module in response to an external control signal indicative of the digital data device being ready to transmit data via the transceiver module; means for storing a plurality of reference values including reference values representing digital equivalent values of timed signals for controlling said initiation, said duration and said shut down of said transmit cycle of the transceiver module; and means for decoding selected ones of said stored reference values as timing reference values, for generating timed signals and for applying timed signals to said timing control means in accordance with said stored reference values to control a timing sequence responsive to ramp up and ramp down characteristics of the transceiver module. - View Dependent Claims (23)
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24. Apparatus for generating a radio frequency modulated signal of a predetermined center frequency in accordance with binary data having a first data signal level and a second data signal level, said apparatus including a modulator with a node for establishing a quiescent bias voltage at the node for maintaining the accuracy of said predetermined center frequency in accordance with the amplitude of said quiescent bias voltage, said apparatus comprising:
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(a) means coupled to the modulator for providing a path to the node to obtain a quiescent level signal whose amplitude is a measure of the amplitude of said quiescent bias voltage; (b) means for generating a first modulator signal of an amplitude set less than that of said quiescent level signal by a predetermined amount to represent said first data signal level; (c) means for generating a second modulator signal of an amplitude set greater than that of said quiescent level signal by said predetermined amount to represent said second data signal level; and (d) means for applying said first modulator signal to the modulator when said binary data is at said first data signal level to cause a first frequency deviation of predetermined frequency shift in one direction from said center frequency and for applying said second modulator level signal to the modulator when said binary data is at said second data signal level to cause a second frequency deviation of said predetermined frequency shift in the other direction from said center frequency. - View Dependent Claims (25)
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26. A method of operating a transmitter to generate a frequency modulated signal of a predetermined center frequency in accordance with binary data having first and second data signal levels, the transmitter providing at a node a quiescent bias voltage and having a modulator that is responsive to the quiescent bias voltage to maintain the accuracy of said predetermined center frequency, said method comprising the steps of:
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(a) establishing a path to the node to obtain a quiescent level signal whose amplitude is a measure of the quiescent bias voltage; (b) generating a first modulator level signal of an amplitude that is less than that of said quiescent level signal by a predetermined amount to represent said first data signal level; (c) generating a second modulator level signal of an amplitude that is greater than that of said quiescent level signal by said predetermined amount to represent said second data signal level; (d) applying said first modulator level signal to the modulator when said binary data is at said first data signal level to cause a first frequency deviation of predetermined frequency shift in one direction from said center frequency; and (e) applying said second modulator level signal to the modulator when said binary data is at said second data signal level to cause a second frequency deviation of said predetermined frequency shift in the other direction from said center frequency. - View Dependent Claims (27)
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Specification