Method and apparatus for frequency division multiplexing

Abstract

A radio transmitter and receiver arrangement includes a transmitter and a receiver. The transmitter generates an electromagnetic carrier that varies in frequency throughout a channel interval, and modulates the carrier with an information signal during the channel interval, whereby the carrier is modulated both in frequency and in accordance with the information signal during the channel interval. The receiver receives the carrier that is modulated both in frequency and in accordance with the information signal, generates a detection signal that varies in frequency throughout the channel interval, and mixes the carrier and the detection signal to recover the information signal.

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       7 . A radio receiver comprising an antenna for receiving a carrier that varies in frequency and is modulated in accordance with an information signal during a channel interval, a first means for generating a detection signal that varies in frequency throughout a channel interval, and a detector means for mixing the carrier and the detection signal and recovering the information signal. 
   
   
       8 . A radio receiver according to  claim 7 , wherein the carrier varies in frequency during the channel interval, the first means comprises a sawtooth generator and a voltage controlled oscillator and the detector means comprises a quadrature mixer for mixing the carrier both with the detection signal and a phase shifted replica of the detection signal. 
   
   
       9 . A radio transmitter that includes a means for receiving an input data word and generating a digital sequence that reflects systematic variation of a carrier and modulation of the carrier in accordance with the data word, an amplifier for receiving the digital sequence as an input signal and generating an output signal, and an antenna for receiving and emitting the output signal. 
   
   
       10 . A radio transmitter according to  claim 9 , wherein the means for receiving the input data word comprises a symbol lookup table having a plurality of addressable locations and each location is addressable by an address having a symbol segment and a frequency segment. 
   
   
       11 . A radio transmitter according to  claim 9 , wherein the systematic variation of the carrier is frequency variation and modulation in accordance with the data word is phase modulation. 
   
   
       12 . A radio transmitter that comprises a means for receiving an input data word and generating a digital sequence that reflects systematic variation of a carrier and modulation of the carrier in accordance with the data word, and a digital-to-analog converter for converting the digital sequence to analog form at a sample conversion rate such as to generate a bandpass signal that varies both systematically and in according with the data word, an amplifier for receiving the bandpass siqnal as an input signal and qeneratinq an output siqnal, and an antenna for receiving and emittinq the output siqnal. 
   
   
       13 . (canceled) 
   
   
       14 . A radio receiver for receiving a carrier that both varies in frequency and is modulated in accordance with information content of a digital word, the radio receiver comprising a first means for generating a digital sequence that reflects variation of a detection signal in frequency, a digital-to-analog converter for converting the digital sequence to analog form and providing a detection signal, and a detector means for mixing the detection signal and the carrier and recovering the information content of the digital word. 
   
   
       15 . A radio receiver according to  claim 14 , wherein the detector means detects modulation in phase and includes a means for outputting a symbol in accordance with the phase modulation and for demapping a symbol to provide a sequence of digital bits forming the digital word. 
   
   
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       28 . A radio transmitter for transmitting digital data represented by symbols selected from a menu of symbols, wherein each symbol is characterized by at least one of phase and frequency, comprising a look-up table that stores a digital representation of each symbol, an addressing means for addressing the look-up table in accordance with a group of digital data digits, whereby the look-up table outputs a digital signal representative of a symbol selected by the group of digital data digits, a digital to analog converter for converting the digital signal to analog form, an amplifier for receiving the analog signal provided by the digital to analog converter as an input signal and generating an output signal, and an antenna for receiving and emitting the output signal. 
   
   
       29 . A radio transmitter according to  claim 28 , wherein each symbol is characterized by phase and the look-up table stores a digital representation of each symbol at a plurality of frequencies, and the addressing means addresses the look-up table in accordance with a group of digital data digits and in accordance with a preselected frequency. 
   
   
       30 . A radio transmitter according to  claim 29 , wherein the addressing means addresses the look-up table in accordance with a preselected sequence of frequencies. 
   
   
       31 . A radio transmitter according to  claim 30 , wherein the addressing means addresses the look-up table in accordance with a cyclically repeating sequence of frequencies. 
   
   
       32 . (canceled) 
   
   
       33 . A radio transmitter according to  claim 9 , wherein the modulation in accordance with the data word is phase modulation. 
   
   
       34 . A radio transmitter according to  claim 9 , comprising a symbol look-up table for receiving said input data word as an address word and for outputting at least one parallel digital data word, wherein the input data word comprises a first component and a second component, the transmitter comprises a means for converting said parallel data word to said digital sequence and a means for reconstructing an analog signal from said digital sequence, and said analog signal has a frequency that depends on said second component and a phase that depends on said first component. 
   
   
       35 . A radio transmitter according to  claim 34 , wherein said analog signal has a fixed frequency for each value of said second component. 
   
   
       36 . A radio transmitter according to  claim 34 , wherein said analog signal varies in frequency over a fixed range for each value of said second component. 
   
   
       37 . A radio transmitter according to  claim 9 , wherein the systematic variation of the carrier is periodic variation in frequency and the periodic variation in frequency has a substantially uniform period. 
   
   
       38 . A radio transmitter according to  claim 12 , wherein said digital sequence is composed of two component sequences and the digital to analog converter comprises first and second converters for converting the two component sequences respectively, a clock source for clocking the first and second converters, whereby the first and second converters generate first and second analog component signals respectively, a phase offset means for offsetting the clocking of the second converter in phase relative to the clocking of the first converter, and a summation circuit for combining said first and second analog component signals to produce said bandpass signal. 
   
   
       39 . A radio transmitter according to  claim 12 , wherein the means for receiving the input data word generates a digital sequence that reflects systematic variation of the carrier in frequency and modulation of the carrier in phase in accordance with the data word. 
   
   
       40 . A radio receiver according to  claim 7 , wherein the detection signal varies periodically in frequency and the periodic variation in frequency has a substantially uniform period. 
   
   
       41 . A method of determining whether a receiver is synchronized with a transmitter, wherein:
 the transmitter transmits a signal encoded with first and second mutually orthogonal sequences of transmitter code chips,   the receiver receives the signal, recovers a sequence of receiver code chips from the signal, extracts first and second sequences of receiver code chips from the recovered sequence of receiver code chips, and determines whether either of said first and second sequences of receiver code chips correlates to either of the sequences of transmitter code chips.