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A process and circuit for down-converting a spread spectrum signal by first and second local oscillating signals, amplifying the down-converted signal, separating the amplified signal into intermediate base band signals of I and Q channels, and demodulating the intermediate base band signals in a re

A process and circuit for down-converting a spread spectrum signal by first and second local oscillating signals, amplifying the down-converted signal, separating the amplified signal into intermediate base band signals of I and Q channels, and demodulating the intermediate base band signals in a receiver of a code division multiple access/direct sequence system. The amplified signal is squared to provide an intermediate frequency signal of 2fIF, which is then band pass filtered. The filtered signal is limiting-amplified to be maintained at a given level. A deviation under 1 dB of an input level is automatically adjusted in order to supplement an input dynamic range of the limiting-amplified signal, and the adjusted signal is divided to produce and intermediate frequency signal having a frequency of fIF. Moreover, a clock signal is recovered by the limiting-amplification of an oscillation signal generated in response to a phase difference obtained by comparing the intermediate frequency signal with a feedback signal of a recovery clock. The feedback signal is derived from the clock signal by dividing the clock signal after amplification. The clock signal is further divided and supplied as a stable carrier signal to a phase shifter via a band pass filter and amplifier. The two phase shifted carrier signals are mixed with the amplified signal in order to separate the amplified signal into the intermediate base band signals of the I and Q channels.

대표청구항 ▼

A process for down-converting a spread spectrum signal with first and second local oscillating signals, generating an amplified signal by amplifying the down-converted signal, separating the amplified signal into intermediate base band signals for I and Q channels, and demodulating the separated sig

A process for down-converting a spread spectrum signal with first and second local oscillating signals, generating an amplified signal by amplifying the down-converted signal, separating the amplified signal into intermediate base band signals for I and Q channels, and demodulating the separated signals in a code division multiple access/direct sequence receiver, wherein said step of separating the amplified signal into intermediate base band signals for I and Q channels comprises the steps of: squaring said amplified signal to provide a square wave signal, producing a filtered signal by filtering said square wave signal, said filtered signal being a spread spectrum signal of N times an intermediate frequency, and limit-amplifying the filtered signal to provide a limited signal maintained at a given amplitude; generating an adjusted signal by automatically adjusting an input amplitude of said limited signal to exhibit a deviation of less than one decibel; dividing a frequency of said automatically adjusted signal by N to produce an intermediate frequency signal; recovering a clock signal by making a comparison of said intermediate frequency signal with a feedback signal, producing an oscillation signal in response to a phase difference obtained by said comparison, and limit-amplifying said oscillation signal to recover said clock signal; maintaining said oscillating signal at a constant amplitude; dividing a frequency of said oscillation signal by N to produce said feedback signal; and dividing said frequency of said oscillation signal to produce a stable carrier signal, phase shifting said stable carrier signal, in quadrature, to produce first and second carrier signals and separately mixing said amplified signal with the first and second carrier signals to provide said intermediate base band signals for said I and Q channels.