KR950007090B1 - The spectral spectrum code division multiple access receiver - Google Patents

Abstract

an integrator for integrating two received signals of I channel and Q channel, respectively; a comparator for comparing the two integrated signals; and a multiplexor for selectively generating the larger signal of the two integrated signals of the I and the Q channels.

Description

Spread Spectrum Code Division Multiple Access Receiver

1 is a block diagram of a conventional spread spectrum code division multiple access receiver.

2 is a block diagram of a spread spectrum code division multiple access receiver according to the present invention.

3 is a phase diagram showing signal levels of I and Q channels according to phases.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a communication apparatus operating in a spread spectrum code division multiple access (CDMA) scheme, and more particularly, integrates two received signals of in-phase and quadrature channels, and integrates the amplitude of the integrated signal. The present invention relates to a spread spectrum code division multiple access receiver for easily despreading demodulation by selecting a signal of the larger channel.

The spread spectrum communication device transmits digital data. In general spread spectrum modulation, a signal having a relatively high frequency and a pseudo-noise code (PN) are formed by using an exclusive OR gate. Intra-building communications to remove or reduce CW and jamming signals by using a mixer or by forming and transmitting spread signals with very high bandwidth and low spectral density. The low spectral density is useful for reducing the interference of various radio waves.

In order to receive spread signals formed and transmitted by the above method and to achieve stable demodulation, the CW and Jamming signals may be removed by using a frequency shifting method without an automatic gain control (AGC) device. This reduces the short delay multi-path problem of in-building communications, broadens the dynamic range of the variable range of the frequency and operating characteristics of the tuning circuit, and reduces the acquisition time. A CDMA / DS spread spectrum receiver has been recently introduced as a "Spread Spectrum Comunication System."

The spread spectrum receiver introduced in the U.S. Patent Publication discloses a method for down converting a spread signal received using a local oscillator output frequency (f _L01 .f _S02 ). First and second signal mixing means 11 and 12, first RF amplifying means 13 for amplifying the frequency-converted signal, reference frequency oscillator 14 for forming a coherence clock, the reference frequency Frequency shifting means 24 for shifting the phase by 90 ° (π / 2), first and second low pass filters 15 and 16 for removing two spreading signal components of the I and Q channels, the filtered signal Second and third RF amplifying means 17 and 18 for amplifying the first and second A / D converting means 19 and 20 for converting the amplified signal into a digital signal, and the A / D converted I And absolute value detecting means 21 for taking the absolute values of the two signals of the Q channel, detecting the peak value of the absolute value. Peak detection means 22, and despreading demodulation means 23 for despreading the selected signal to demodulate the original signal.

The conventional spread spectrum receiver according to the above configuration obtains a spread signal value by taking a peak of an absolute value of two signal values of the I and Q channels, and adds the spread signal value. The first RF signal is received and down-converted by the first and second signal mixing means 11 and 12 using an output frequency f _L01 .f _S02 of a local oscillator. The amplification means 13 amplifies and mixes the coherent signal f _corh again to form a spreading signal of the I channel and the coherence signal f _corh supplied from the reference frequency transmitter 14 and the A spreading signal of the Q channel is formed by mixing a signal {f _(corh-90) } shifted by 90 ° by the frequency shifting means 24 and a spreading signal amplified and supplied from the first RF amplifying means 13. . The two signals of the I and Q channels formed by the method are filtered through the first and second low pass filters 15 and 16 to remove the spread signal components and the second and third amplification means 17, 18), the absolute value of the signal of the I and Q channels, which are amplified using the first and second A / D conversion means 19 and 20 and then converted into digital values, is obtained from the means 21 and the peak In the detecting means 22, a signal is obtained by detecting and adding the absolute peak value.

Another method of processing a conventional spreading signal is a Costa Loop method, which extracts a difference component between two signals of the I and Q channels obtained by the method, and then uses a coherent signal (PLL). It is a method of obtaining a spread signal value from one of channels I and Q by supplying an error voltage to the VCO forming f _corh ).

In the method of obtaining a spread signal value by taking a peak of the absolute value and adding the peak, the signal is processed by taking an absolute value of two signal values of the I and Q channels, taking a peak thereof, and then adding the peak value to obtain a signal value. As a result, the circuit becomes complicated, and in the process of adding two signals of the I and Q channels, there is a problem that an abnormal state appears in the added output when the state of one channel is not good. When the loop is abnormal or the channel is not good due to the output, the output is completely dependent on the abnormal state. In particular, when the phase is delayed, the output level does not occur at all.

In order to solve the above problems, the spread spectrum code division multiple access receiver according to the present invention integrates spread signals and compares two pre-divided signals to despread and demodulate the received spread signals. The purpose is to improve the demodulation function by selecting and despreading demodulation.

In order to achieve the above object, the spread spectrum code division multiple access receiver according to the present invention is a spread spectrum method, comprising: integrating means 40 for integrating two received signals of I and Q channels, respectively; Comparing means 37 for comparing two signals integrated by the integrating means 40, and a multiplexer 38 for selectively outputting a large signal among two received signals of the I and Q channels according to the comparison result of the comparing means. And despreading demodulation by selecting a channel having an integral value of the spread signal among the two channels.

Hereinafter, a spread spectrum communication apparatus of the present invention will be described in detail with reference to the accompanying drawings.

The spread spectrum code division multiple access receiver according to the present invention shown in FIG. 2 is a first and second method for down converting a received spread signal by using an output frequency (f _L01 .f _S02 ) of a local oscillator. 2 signal mixing means 25 and 26, a first RF amplification means 27 for amplifying the frequency-converted signal, a reference frequency oscillator 28 for forming a coherence clock, and a phase of the reference frequency 90 °. a frequency shifting means 41 for shifting by (π / 2), first and second low pass filters 29 and 30 for removing the spread signal components of the two channels, and a second for amplifying the filtered signal Third RF amplification means 31 and 32, second and second A / D conversion means 33 and 34 for converting the amplified signal into a digital signal, and conversion by the first A / D conversion means 33. Q channel changed by the first integrating means 35 and the second A / D converting means 34 for integrating the signal of the divided I channel. A second integrating means 36 for integrating the signal, a comparing means 37 for comparing two signals integrated in the first and second integrating means 35 and 36, and a larger signal of the two compared signals. A multiplexer 38 for selectively outputting, and a despreading demodulation circuit 39 for demodulating the original signal by despreading the selected signal.

3 is a phase diagram showing signal levels of I and Q channels according to phases.

The signal level of the channel according to the phase θ of the I and Q channels shown in FIG. 3 is V _SQ when the I channel is V _SI . Therefore, the I and Q signal levels are V _SI and V _SQ at any ωt (θ) because the phase relationship where the spread signal is mixed by the coherence clock in the I and Q channels is shifted by 90 ° (π / 2). Has a constant relationship with the phase.

However, the coherent phase of the balancing clock, θ (ωt) component is the less variable or by the basic circuit delay (I) and up to that of the Q channel both V _SI V _SQ is the minimum that is, becomes "0" anti-up of V _SQ At this point, since V _SI is minimized, it is problematic to demodulate (despread) the signal depending on one channel. In other words, it is difficult to demodulate the received signal when the signal value appears at a point where the phase θ is close to zero due to the phase change of the coherence clock or the phase change of the spread reception signal.

Therefore, the spread spectrum receiver of the present invention according to the above configuration is for facilitating despreading demodulation by selecting a channel having a larger integrated signal size for a predetermined time of I and Q channels, and being spread from the transmitter. Receiving the transmitted signal and down-converting the received spread signal using the output frequency (f _L01 .f _S02 ) of a local oscillator in the first and second signal mixing means 25 and 26 after the signal is amplified by the first 1RF amplifying means 27 and re-coherent signal (f _corh) and forms a signal of I channel in a manner to mix it said coherent signal (f _corh) with 90 ° shift (f _(corh-90) ) and the spread signal received from the reference frequency transmitter 28 by the coherent signal f _corh and the phase shifting means 41, the phase of the reference frequency is 90 ° (π / 2) signal shifted by {f _(corh-90) } And a spreading signal amplified by the first RF amplification means 27 to form a Q channel signal.

The two signals of the I and Q channels formed by the method pass through the first and second low pass filters 29 and 30 to filter and remove the spread signal components, and the second and third amplifying means 31 After amplification at 32, the first and second A / D conversion means 33 and 34 convert the digital values. The two signal values of the I and Q channels obtained by the method are integrated for a time equal to N times (where N is an integer) of the PN period T _P1 in the first and second integrating means 35 and 36. The integrated signal is compared by the comparing means 37. As a result of the comparison, the multiplexer 38 selects the signal value of the I channel if the integrated signal of the I channel is larger than the integrated signal value of the Q channel. If it is small, the A / D converted signal output value of the Q channel is selected to always output a signal of a channel having a large amplitude. At this time, the signal value of the selected and output channel is demodulated by the despreading demodulation circuit 39 by multiplexing the PN code and obtaining the original signal based on the result.

Accordingly, the spread spectrum code division multiple access receiver of the present invention selects a signal having a large amplitude among two signals by using a constant output difference always present between I and Q channels, thereby despreading and demodulating demodulation, thereby always maintaining a good channel. Possible and despreading circuitry has the significant effect of making demodulation processing simpler.

Claims (2)

1. A spread spectrum code division multiple access receiver comprising: integrating means for integrating two received signals of I and Q channels, respectively; Comparison means for comparing two signals integrated in the integration means; And a demultiplexer for selectively outputting a large signal among two received signals of the I and Q channels according to a comparison result of the comparing means, and selecting a channel having a large integral value of the spread signal among the two channels to despread and demodulate it. A spread spectrum code division multiple access receiver. The spread spectrum code division multiplexing method according to claim 1, wherein each of the integrating means integrates the received signal for a time equal to N times the PN (Pseudo-Noise) period T _P1 (where N is an integer). Connection receiver.