Receiver for spread spectrum communication and receiving method for the same

A receiver for use in a spread spectrum communication system comprising:

• spread signal distributing means for distributing a received spread spectrum signal into at least three signals comprising a first spread signal, a second spread signal and a third spread signal,
• pseudo noise signal generating means which generates pseudo noise signals having a code series which is substantially equal to a pseudo noise signal included in said received spread spectrum signal,
• phase shift means for receiving a pseudo noise signal generated by said pseudo noise signal generating means for outputting at least a first pseudo noise signal having a reference phase, a second pseudo noise signal having a phase which leads the reference phase of said first pseudo noise signal by an amount corresponding to a specified number of code bits and a third pseudo noise signal having a phase which lags the reference phase of said first pseudo noise signal by an amount corresponding to a specified number of code bits,
• first correlation detecting means comprising first reverse spread means for generating a first reverse spread signal by reversely spreading said first reverse spread signal with said first pseudo noise signal, first signal extracting means for extracting a signal element of said first reverse spread signal, and first detecting means for detecting by an envelope detection method an extracted signal element of said first signal extracting means,
• second correlation detecting means comprising second reverse spread means for generating a second reverse spread signal by reversely spreading said second spread signal with said second pseudo noise signal, second signal extracting means for extracting a signal element of said second reverse spread signal, and second detecting means for detecting by an envelope detecting method an extracted signal element of said second signal extracting means,
• third correlation detecting means comprising third reverse spread means for generating a third reverse spread signal by reversely spreading said third spread signal with said third pseudo noise signal, third signal extracting means for extracting a signal element of said third reverse spread signal and third detecting means for detecting by an envelope detection method an extracted signal element of said third signal extracting means,
• hybrid means for generating a signal corresponding to a difference between an output of said second correlation detecting means and an output of said third correlation detecting means,
• synchronization control means for setting a bit rate which deviates by a specified value from the bit rate of the pseudo noise signal included in said received spread spectrum signal and for executing an initial seizing control operation to adjust the bit rate to be substantially equal to the bit rate of the pseudo noise signal included in said received spread spectrum signal when an output of said first correlation detecting means becomes higher than the specified level, and for continuously executing a synchronization sustaining control operation to hold an output of said hybrid means to a reference level after the bit rate is adjusted in said initial seizing control operation by monitoring an output of said first correlation detecting means and an output of said hybrid means and adjusting the bit rates from time to time, and for suspending execution of said synchronization sustaining control operation to start a measurement of time when an output of said first correlation detecting means becomes lower than said specified level during execution of said synchronization sustaining control operation and for re-executing the synchronization sustaining control operation when an output of said first correlation detecting means becomes higher than said specified level within a specified time period, and
• activating means for activating said pseudo noise generating means on the basis of the bit rate set by said synchronization control means.

A receiver for use in spread spectrum communication system comprising:

• oscillator means for oscillating an electrical signal of a preset frequency,
• frequency mixing means for mixing the received spread spectrum signal and an electrical signal oscillated by said oscillator means to generate a spread spectrum signal of low frequency,
• spread signal distributing means for distributing the spread spectrum signal output from said frequency mixing means into at least a first spread signal, a second spread signal and a third spread signal,
• pseudo noise signal generating means for generating a pseudo noise signal having a code train which is substantially equal to a pseudo noise signal included in said received spread spectrum signal,
• phase shift means for receiving the pseudo noise signal generated from said pseudo noise signal generating means and for outputting at least a first pseudo noise signal having a reference phase, a second pseudo noise signal having a phase which leads the reference phase of said first pseudo noise signal by an amount corresponding to a specified number of code bits and a third pseudo noise signal having a phase which lags the reference phase of said first pseudo noise signal by an amount corresponding to a specified number of code bits,
• first correlation detecting means comprising first reverse spread means for generating a first reverse spread signal by reversely spreading said first spread signal with said first pseudo noise signal, first signal extracting means for extracting a signal element of said first reverse spread signal, and first detecting means for detecting an extracted signal element of said first signal extracting means by an envelope detecting method,
• second correlation detecting means comprising a second reverse spread means for generating a second reverse spread signal by reversely spreading said second spread signal with said second pseudo noise signal, a second signal extracting means for extracting a signal element of said second reverse spread signal and second detecting means for detecting an extracted signal element of said second signal extracting means by an envelope detecting method,
• third correlation detecting means comprising a third reverse spread means for generating a third reverse spread signal by reversely spreading said third spread signal with said third pseudo noise signal, third extracting means for extracting a signal element of said third reverse spread signal and third detecting means for detecting an extracted signal element of said third extracting means by an envelope detecting method,
• hybrid means for generating a signal depending on a difference between an output of said second correlation detecting means and an output of said third correlation detecting means,
• synchronization control means for setting a bit rate which deviates by a specified value from the bit rate of the pseudo noise signal included in said received spread spectrum signal, and for executing an initial seizing control operation to adjust the bit rate to be substantially equal to the bit rate of the pseudo noise signal included in said received spread spectrum signal when an output of said first correlation detecting means becomes higher than a specified level, and for continuously executing, after the bit rate is adjusted in said initial seizing control operation, a synchronization sustaining control operation to hold an output of said hybrid means to a reference level and for causing a frequency compensation control means to control an output of said correlation detecting means by adjusting the frequency of said electrical signal from time to time by monitoring an output of said first correlation detecting means and an output of said hybrid means and adjusting the bit rates from time to time,
• activating means for activating said pseudo noise generating means on the basis of the bit rate set by said synchronization control means, and
• demodulating means connected to said synchronization control means for extracting data included in said spread spectrum signal.

A receiver for use in a spread spectrum communication comprising:

• spread signal distributing mean for distributing a received spread spectrum signal into at least a first spread signal, a second spread signal and a third spread signal,
• pseudo noise signal generating means for generating a pseudo noise signal having a code series which is substantially equal to a pseudo noise signal included in said received spread spectrum signal,
• phase shift means for receiving the pseudo noise signal generated from said pseudo noise signal generating means and for outputting at least a first pseudo noise signal having a reference phase, a second pseudo noise signal having a phase which leads the reference of the first pseudo noise signal by an amount corresponding to a specified number of code bits and a third pseudo noise signal having a phase which lags the reference phase of the first pseudo noise signal by an amount corresponding to a specified number of code bits,
• first correlation detecting means comprising a first reverse spread means for generating a first reverse spread signal by reversely spreading said first spread signal with said first pseudo noise signal, first signal extracting means for extracting a signal element of said first reverse spread signal and first detecting means for detecting an extracted signal element of said first signal extracting means by an envelope detecting method,
• second correlation detecting means comprising a second reverse spread means for generating a second reverse spread signal by reversely spreading said second spread signal with said second pseudo noise signal, second signal extracting means for extracting a signal element of said second reverse spread signal, and second detecting means for detecting an extracted signal element of said second signal extracting means by an envelope detecting method,
• third correlation detecting means comprising a third reverse spread means for generating a third reverse spread signal by reversely spreading said third spread signal with said third pseudo noise signal, third signal extracting means for extracting a signal element of said third reverse spread signal and a third detecting means for detecting an extracted signal element of said third signal extracting means by an envelope detecting method,
• hybrid means for generating a signal corresponding to a difference between an output of said second correlation detecting means and an output of said third correlation detecting means,
• synchronization control means for setting a bit rate shifted by a specified value from the bit rate of a pseudo noise signal included in said received spread spectrum signal, and for executing an initial seizing control operation to adjust the bit rate to be substantially equal to the bit rate of the pseudo noise signal included in said received spread spectrum signal when an output of said first correlation detecting means becomes higher than a specified level and for continuously executing a synchronization sustaining control operation after the bit rate is adjusted in said initial seizing control operation to hold an output of said hybrid means to a reference level by monitoring an output of said first correlation detecting means and an output of said hybrid means and adjusting the bit rates from time to time,
• activating means for activating said pseudo noise generating means based on the bit rate set by said synchronization control means,
• demodulating means connected to said synchronization control means for extracting data included in said spread spectrum signal,
• Costas Loop demodulating means,
• first prelock detecting means for detecting a first prelock signal when an output of said first correlation detecting means exceeds the preset level,
• second prelock detecting means for detecting a second prelock signal when the amplitude of an output of a multiplying means of said Costas Loop demodulating means is within the preset range, and
• lock detecting means for detecting a lock condition of said Costas Loop demodulating means when said first prelock signal and second prelock signal exist.