Method and apparatus for reducing phase cancellation in a simulcast paging system
First Claim
1. A radio frequency transmitter for use in a simulcast environment, said transmitter comprising:
- an input terminal coupled to receive an input signal;
a modulator having an input lead and an output lead, said input lead of said modulator coupled to said input terminal, said modulator being configured to perform a modulation process on a carrier signal using a signal received at said input lead of said modulator, wherein said modulator is configurable to introduce a first frequency offset, a second frequency offset and a third frequency offset to said carrier signal, said first and third frequency offsets being different from each other;
a power amplifier having an input lead coupled to said output lead of said modulator, said power amplifier configured to output an amplified signal dependent on a signal received at said input lead of said power amplifier; and
a controller coupled to said modulator, said controller being configured to selectively configure said modulator to introduce said first frequency offset or said third frequency offset to said carrier signal when said transmitter is transmitting signals according to a first protocol, and wherein said controller is confirmed to selectively configure said modulator to introduce said second frequency offset when said transmitter is transmitting signals according to a second protocol, said first frequency offset being predetermined and optimized to minimize the phase cancellation data reception errors for signals transmitted according to said first protocol, and said second frequency offset being predetermined and optimized to minimize the phase cancellation data reception errors for signals transmitted according to said second protocol.
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Accused Products
Abstract
A transmitter includes a modulator, a power amplifier and a controller to reduce the effects of phase cancellation in a simulcast paging system. The modulator is digitally configurable to modulate according to at least two protocols. The controller configures the modulator for a first protocol and provides to the modulator a signal to be broadcast. The modulator then modulates this signal according to the first protocol and causes the modulator to introduce a random frequency offset within a frequency range predetermined to optimally reduce phase cancellation for the first protocol. When the controller provides a signal to be broadcast according to a second protocol, the controller reconfigures the modulator for the second protocol. In addition the controller causes the modulator to introduce a random frequency offset within a predetermined range to optimally reduce phase cancellation for the second protocol. Because the controller can change the frequency offset on a protocol basis, phase cancellation errors can be optimally reduced for both protocols. In addition, the transmitter can easily be reconfigured to support new protocols as they are developed without changing the existing transmitter hardware. Still further, the randomly changing offsets dispense with the need to maintain records of the offsets for each transmitter in the simulcast paging system.
76 Citations
41 Claims
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1. A radio frequency transmitter for use in a simulcast environment, said transmitter comprising:
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an input terminal coupled to receive an input signal; a modulator having an input lead and an output lead, said input lead of said modulator coupled to said input terminal, said modulator being configured to perform a modulation process on a carrier signal using a signal received at said input lead of said modulator, wherein said modulator is configurable to introduce a first frequency offset, a second frequency offset and a third frequency offset to said carrier signal, said first and third frequency offsets being different from each other; a power amplifier having an input lead coupled to said output lead of said modulator, said power amplifier configured to output an amplified signal dependent on a signal received at said input lead of said power amplifier; and a controller coupled to said modulator, said controller being configured to selectively configure said modulator to introduce said first frequency offset or said third frequency offset to said carrier signal when said transmitter is transmitting signals according to a first protocol, and wherein said controller is confirmed to selectively configure said modulator to introduce said second frequency offset when said transmitter is transmitting signals according to a second protocol, said first frequency offset being predetermined and optimized to minimize the phase cancellation data reception errors for signals transmitted according to said first protocol, and said second frequency offset being predetermined and optimized to minimize the phase cancellation data reception errors for signals transmitted according to said second protocol. - View Dependent Claims (2, 3, 4, 5)
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6. A radio frequency transmitter for use in a simulcast environment, said transmitter comprising:
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an input terminal coupled to receive an input signal; a modulator having an input lead and an output lead, said input lead of said modulator coupled to said input terminal, said modulator being configured to perform a modulation process on a carrier signal using a signal received at said input lead of said modulator, wherein said modulator is configurable to introduce a first frequency offset, a second frequency offset, and a third frequency offset to said carrier signal; a power amplifier having an input lead coupled to said output lead of said modulator, said power amplifier configured to output an amplified signal dependent on a signal received at said input lead of said power amplifier; and a controller coupled to said modulator, said controller being configured to selectively configure said modulator to introduce said first frequency offset or said third frequency offset to said carrier signal when said transmitter is transmitting signals according to said first protocol, and wherein said controller is configured to selectively configure said modulator to introduce said second frequency offset when said transmitter is transmitting according to said second protocol, said first frequency offset and said third frequency offset being predetermined and optimized to minimize phase cancellation data reception errors for signals transmitted according to said first transmission protocol, said third frequency offset being different from said first frequency offset, said second frequency offset being predetermined and optimized to minimize phase cancellation data reception errors for signals being transmitted according to said second protocol. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 21, 22, 23)
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17. A method of reducing phase cancellation in a simulcast paging system, said method comprising;
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providing a first frequency offset within a first predetermined range of frequency, said first predetermined range of frequency being predetermined and optimize to minimize phase cancellation data reception errors for signals being transmitted according to a first protocol; modulating a carrier signal according to said first protocol and combining said first frequency offset with said carrier signal to form a first output signal; transmitting said first output signal using a transmitter; providing a third frequency offset from a center frequency within said first predetermined range of frequency, said first and third frequency offsets being different from each other; modulating said carrier signal according to said first protocol and combining said third frequency offset with said carrier signal to form a third output signal;
transmitting said third output signal using said transmitter;providing a second frequency offset within a second predetermined range of frequency said second predetermined range of frequency being different from said first predetermined range of frequency and being predetermined and optimized to minimize phase cancellation data reception errors for signals being transmitted according to a second protocol; modulating said carrier signal according to said second protocol and combining said second frequency offset with said carrier signal to form a second output signal; and transmitting said second output signal using said transmitter. - View Dependent Claims (19, 20, 24, 25, 26, 27)
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28. A radio frequency transmitter comprising:
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an input terminal coupled to receive an input signal; an output terminal; a modulator having an input lead and an output lead, said input lead of said modulator coupled to said input terminal, wherein said modulator is configurable to selectively introduce a first frequency offset or a third frequency offset to a first carrier signal and a second frequency offset to a second carrier signal, said first and third frequency offsets being different from each other; a power amplifier having an input lead coupled to said output lead of said modulator, said power amplifier configured to provide at said output terminal an amplified signal dependent on a signal received at said input lead of said power amplifier; and a controller coupled to said modulator, said controller being configured to selectively configure said modulator to introduce said first frequency offset or said third frequency offset to said first carrier signal when said transmitter is transmitting signals according to a first protocol and to introduce said second frequency offset to said second carrier signal when said transmitter is transmitting signals according to a second protocol, said first frequency offset being predetermined and optimized to minimize phase cancellation data reception errors for signals transmitted according to said first protocol and said second frequency offset being predetermined and optimized to minimize phase cancellation data reception errors for signals transmitted according to said second protocol. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A radio frequency transmitter for use in a simulcast environment, said transmitter comprising;
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an input terminal coupled to receive an input signal; a modulator having an input lead and an output lead, said input lead of said modulator coupled to said input terminal said modulator being configured to perform a modulation process on a carrier signal using a signal received at said input lead of said modulator; a power amplifier having an input lead coupled to said output lead of said modulator, said power amplifier configured to output an amplified signal dependent on a signal received at said input lead of said power amplifier; and a controller coupled to said modulator, wherein said controller is configured to selectively cause said modulator to introduce one of a plurality of frequency offsets to said carrier signal in a hop sequence when said transmitter is transmitting signals according to a first protocol, said plurality of frequency offsets being predetermined and optimized to minimize phase cancellation data reception errors for signals transmitted according to said first protocol, and said controller being further configured, when said transmitter is transmitting signal according to a second protocol, to selectively cause said modulator to introduce a frequency offset predetermined and optimized to minimize phase cancellation data reception errors for signals transmitted according to said second protocol. - View Dependent Claims (40, 41)
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Specification