KR20010010630A - Apparatus for recieving intermediate frequency in a mobile communication cell site of code division multi access - Google Patents

Abstract

PURPOSE: An apparatus for receiving an intermediate frequency(IF) in a mobile communication base station device having a code division multiple access(CDMA) system is provided to perform the first down-converting for an IF signal received from a radio frequency(RF) device and to perform the second down-converting for the firstly down-converted IF signal into an in-phase(I) channel signal and a quadrature(Q) channel signal,and thereby carrying out a quadrature phase-shift keying(QPSP) demodulation. CONSTITUTION: The first filter(30) removes other signal components except bands from intermediate frequency(IF) signals, received from a radio frequency(RF) unit. A frequency mixer(31) mixes the filtered IF signals with an optional local frequency. The second filter(32) eliminates other signal components except the bands from the mixed signals. The first amplifier(33) amplifies signals outputted from the second filter(32) with regular levels. A gain controller(32) controls an amplification gain, to make signals outputted from the first amplifier(33) maintain regular power according to a gain control signal. The second amplifier(35) amplifies signals outputted from the gain controller(34) with regular levels. A demodulator(36) separates optional frequencies of baseband signals into in-phase(I) channels and quadrature(Q) channels, from signals outputted from the second amplifier(35), and extracts the separated base band signals.

Description

Apparatus for recieving intermediate frequency in a mobile communication cell site of code division multi access}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an intermediate frequency receiver in a mobile communication base station apparatus of Code Division Multi Access (CDMA) scheme, and more particularly, to an RF (Radio Frequency) unit in a mobile communication base station apparatus of a broadband CDMA scheme. The present invention relates to an IF receiver in a CDMA mobile communication base station apparatus which demodulates an intermediate frequency (IF) signal received therefrom in two steps and then demodulates it.

A general CDMA mobile communication base station is composed of a switching system and cell equipment. This includes many of the unit functional units that make up the system, and these units are implemented with various types of equipment.

The core of such a mobile communication base station apparatus is a digital shelf carrying a channel card, a sector interface card, an analog common card, and an end card. The transceiver self converts an intermediate frequency signal (hereinafter referred to as IF) output from the digital self into UHF and down-converts the received UHF into IF.

In addition, the transceiver itself includes a sector access card that combines baseband forward signals received from the channel card and converts them up to IF signals. These sector access cards receive combined baseband transmit signals from analog common cards and combine and amplify them. The combined signal passes through a low pass filter (LPF) and combines the IF signal, a 4.95 Mhz IF signal filtered through a band pass filter (BPF) with a combined 0 ° and 90 ° local frequency of 4.95 MHz. Rack). Therefore, the RF rack is to convert the 4.95Mhz IF signal received for signal transmission through the antenna to UHF signal.

On the contrary, when the UHF signal received through the antenna in the RF rack is converted to 4.95MHz IF signal and transmitted, the I-channel signal and Q-channel signal are extracted by band-filtering the converted 4.95MHz IF signal, respectively. IF signal of is combined with 0 ° and 90 ° delay signal of 4.95MHz respectively and filtered through low pass filter (BPF), and I channel data is converted into digital signal by filtering filtered I channel IF signal and Q channel IF signal, respectively. And Q channel data are respectively demodulated.

Hereinafter, an IF receiver in a general CDMA mobile communication base station apparatus will be described with reference to the accompanying drawings.

1 is a block diagram of an IF receiver in a general CDMA mobile communication base station apparatus. Referring to FIG. 1, a band filter 10, a voltage adjusting amplifier 11, and a frequency mixer (FIG. 12, 12a), first and second low pass filters 13 and 13a, amplifiers 14 and 14a, first and second phase equalizers 15 and 15a, and first and second A / D converters 16 and 16a. , A gain control ROM 17, a D / A converter 18, and an integrator 19.

The band pass filter 10 is a filter having a center frequency of 4.95 MHz, and after removing other signal components out of band from the 4.95 MHz IF signal input from the RF processor (not shown), the voltage adjusting amplifier 11 )

The voltage adjusting amplifier 11 controls the amplification degree according to the voltage adjusting signal provided from the integrator 19, so that the voltage adjustment amplifier 11 can maintain a certain voltage even if the input level changes.

The frequency mixers 12 and 12a mix the 0 ° and 90 ° delay signals of 4.95 MHz with the IF signals input from the voltage adjusting amplifier 11, respectively, so that the first low pass filter 13 and the second low pass filter 13a are respectively mixed. Enter each as

The first and second low pass filters 13 and 13a remove out-of-band signal components from the signals output from the frequency mixers 12 and 12a, and then output them to the amplifiers 14 and 14a, respectively.

The amplifiers 14 and 14a pass through the frequency mixers 12 and 12a and the first and second low pass filters 13 and 13a to compensate for the lowered power. The output signal is amplified by a predetermined level and then output to the first and second phase equalizers 15 and 15a, respectively.

The first and second phase equalizers 15 and 15a artificially compensate the nonlinearized signal with the linearized signal by converting the phase of the signal output from the amplifiers 14 and 14a, and then the first and second A / D. Output to converters 16 and 16a, respectively.

The A / D converters 16 and 16a convert the linearized IF signals input from the first and second phase equalizers 15 and 15a into digital data of 16-bit I and Q channels, respectively, and then separate them. After demodulating the I channel and Q channel data through a dedicated demodulation device.

In addition, the I channel data and the Q channel data output from the A / D converters 16 and 16a are respectively input to the automatic gain control ROM 17 as address signals. At this time, the automatic gain control ROM 17 stores a voltage adjustment data table for controlling the voltage amplification of the voltage adjusting amplifier 11, and is input from the first and second A / D converters 16 and 16a. Reads voltage adjustment data corresponding to the address signal of < RTI ID = 0.0 >, < / RTI > and outputs it to the D / A converter 18. The D / A converter 18 converts the voltage adjustment data output from the automatic gain control ROM 17 into an analog signal. After conversion, the signal is output to the integrator 19. Therefore, the integrator 19 integrates the input voltage adjustment analog signal and then provides the voltage adjustment signal to the voltage adjustment amplifier 11.

Such an IF receiver for a CDMA mobile communication base station apparatus has a problem in that I / Q demodulation cannot be stably performed at a low frequency because demodulation is performed without downconverting the 4.95MHz IF input to one stage.

In addition, since the IF signal is low at 4.95 MHz, the baseband of a wide band cannot be accommodated, and when the IF signal band becomes large, that is, when the amount of data increases, there is a problem in that it cannot accommodate data for a larger band. .

Accordingly, the present invention has been made to solve the above-mentioned problems according to the prior art, an object of the present invention is to first down-convert the 70 MHz IF signal received from the RF device to 21.4 MHz, and then down-convert to the first order. IF in CDMA type mobile communication base station apparatus which can perform quadrature phase-shift keying (QPSP) demodulation by second-converting the converted 21.4MHz IF signal back to 3.6864MHz I channel signal and Q channel signal signal In providing a receiving apparatus.

A feature of the IF receiving apparatus in the CDMA mobile communication base station apparatus according to the present invention for achieving the above object is a CDMS mobile communication base station apparatus having an RF processing apparatus and a demodulation processing apparatus. First frequency downconverting means for downconverting the frequency signal by using an arbitrary local frequency from the IF signal input from the apparatus; Second frequency downconverting means for downconverting the frequency signal downconverted from the first frequency downconverting means into baseband signals of I and Q channels using another local frequency; A / D conversion means for converting the I-channel signal and the Q-channel signal down-converted from the second frequency down-converting means into I-channel digital data and Q-channel digital data, respectively, and outputting them to the demodulation processing apparatus.

1 is a block diagram of an intermediate frequency receiver in a general mobile communication base station apparatus;

2 is a block diagram of an intermediate frequency receiver in a mobile communication base station apparatus of a code division multiple access method according to the present invention;

<Explanation of symbols for main parts of drawing>

30, 32, 37, 37a, 42: filtering unit 31: frequency mixing unit

33, 35, 38, 38a: amplifying section 34: gain control section

36: demodulation part 39, 39a: A / D conversion part

40: storage unit 41: D / A conversion unit

Hereinafter, a preferred embodiment of an IF receiver in a CDMA mobile communication base station apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram of an IF receiver in a CDMA mobile communication base station apparatus according to the present invention. Referring to FIG. 2, the configuration of the present invention is received from an RF unit (not shown). A first mixing unit 30 for removing other out-of-band signal components from the IF signal, a frequency mixing unit 31 mixing an IF signal filtered by the first filtering unit 30 with an arbitrary local frequency, and The second filtering unit 32 for removing other signal components out of band from the mixed signal output through the frequency mixing unit 31, and the first amplification for a predetermined level amplification of the signal output from the second filtering unit 32 It consists of a part 33. Here, the first filtering unit 30 is a band pass filter having a center frequency of 70 MHz to remove the spurious signal from the 70 MHz IF signal input from the RF, and the frequency mixing unit. The signal output from the 31 is a signal having both a total frequency band and a subtracted frequency band signal mixed with a 70 MHz signal output from the first filtering unit 30 and a local frequency of 48.6 MHz, and the second filtering unit 32. ) Is a band pass filter having a center frequency of 21.4 MHz for extracting only the signals of the subtracted frequency band among the total frequency band and the subtracted frequency band signals output from the frequency mixing unit 31.

In addition, the gain control unit 34 for controlling the amplification gain so as to maintain a predetermined power according to the gain adjustment signal provided from the first amplifying unit 33, and the gain control unit 34 is output A second amplifier 35 for amplifying the signal to a predetermined level, and a demodulator 36 for separating and extracting a baseband signal of an arbitrary frequency into an I channel and a Q channel from the signal output from the second amplifier 35. It consists of. Here, the demodulator 36 includes a frequency mixer which separates and extracts a 3.6864 MHz baseband signal into I and Q channels from a signal input from the second amplifier 35 using a local frequency of 21.4 MHz.

In addition, the present invention is a third, fourth filtering unit (37, 37a) to remove the out-of-band signal components from the baseband signal extracted separately in the I channel and Q channel in the demodulator 36, and the third, fourth Third and fourth amplifiers 38 and 38a for compensating for lost power by amplifying a predetermined level of the signal filtered by the filtering units 37 and 37a, and signals amplified by the third and fourth amplifiers 38 and 38a. First and second A / D converters 39 and 39a for converting the digital signals into digital signals and outputting the I and Q channel data, respectively, and gain adjustment data tables. A storage unit 40 for outputting gain adjustment data stored at a address corresponding to the address signal using the I channel data and the Q channel data output from the converters 39 and 39a as an address signal, and from the storage unit 40. D / A converter 41 for converting the output gain adjustment data into an analog signal and analog output from the D / A converter 41 After the out-of-band signal components are removed from the signal, the fifth filtering unit 42 provides the removed signal to the gain control unit 34 as a gain adjustment signal. Here, the storage unit 40 is a dual port ram, and the fifth filtering unit 42 is a low pass filter.

The operation of the IF receiving apparatus in the CDMA mobile communication base station apparatus having the above configuration will be described.

First, the 70 MHz IF signal transmitted from the RF unit of the mobile communication base station system is received by the first filtering unit 30, that is, a band pass filter having a center frequency of 70 MHz, and then a spurious signal from the received 70 MHz IF signal. Is removed. As such, the signal output through the first filtering unit 30 is a mixture of the 70 MHz IF signal and the 48,6 MHz signal that are outputted to the frequency mixing unit 31 having the 48.6 MHz clock as the local clock input. .

Since the signal passing through the frequency mixing unit 31 is a mixture of the total frequency band (118.6 MHz) and the subtraction frequency band (21.4 MHz), the subtraction frequency of 21.4 MHz is used as the center frequency to extract only the signal of the subtraction frequency band. The branch passes through the second filtering unit 32. Therefore, after passing through a bandpass filter having a center frequency of 21.4 MHz, that is, the first filtering unit 32, only a signal having a carrier frequency of 21.4 MHz is output.

The signal having a carrier frequency of 21.4 MHz passing through the second filtering unit 32 is input to the first amplifier 33, amplified by a predetermined level, and then output to the gain control unit 34. Here, the first amplifier 33 amplifies a predetermined level to compensate for the lowered power while passing through the frequency mixer 31, the second filtering unit 32, and the like from the input of the RF unit.

The gain control unit 34 controls the degree of amplification according to the gain adjustment signal provided from the fifth filtering unit 42, and thus it is possible to continuously maintain a certain amount of power even when the level of the input signal is changed. .

The signal output through the gain control unit 34 is amplified by a predetermined level through the second amplifier 35, and then input to the demodulator 36 to demodulate. That is, the demodulator 36 has a frequency mixer internally. The baseband signal of 3.6864 MHz is output from the signal input from the second amplifier 35 using the local frequency 21.4 MHz provided with the I channel and the Q. After separating and extracting the channel, the 3.6864MHZ baseband signal for the I channel is input to the third filtering unit 37, and the 3.6864MHz baseband signal for the Q channel is input to the fourth filtering unit 37a.

The third and fourth filtering units 37 and 37a low-pass filter the 3.6864 MHz baseband signal input from the demodulation unit 36 to output the third and fourth amplifiers 38 and 38a, respectively. do. That is, the 3.6864 MHz baseband signal extracted from the demodulator 36 is filtered through the low pass filters 37 and 37a having the cut off frequency of 5 MHz, and then the third and fourth baseband signals, respectively. It is output to the amplifiers 38 and 38a.

The third and fourth amplifiers 38 and 38a compensate for the lost power by amplifying the signals output by the third and fourth filtering units 37 and 37a by a predetermined level, and then, respectively, the first and second A / Ds. Output to converters 39 and 39a. Accordingly, the first and second A / D converters 39 and 39a convert analog signals input from the third and fourth amplifiers 38 into I channel digital data and Q channel digital data, respectively, and then separately. It outputs to the installed demodulation exclusive device (not shown). Therefore, the I-channel data and the Q-channel data are added later through the demodulation dedicated device installed separately, and the demodulation of the data is finally completed. At this time, the I channel data and the Q channel data output from the first and second A / D converters 39 and 39a are output to the demodulation-only device and input to the storage unit 40 as address signals. I and Q channel data consists of 6 bits. Accordingly, the storage unit 40 reads the gain adjustment data values previously stored at the corresponding addresses according to the address signals inputted from the first and second A / D converters 39 and 39a, respectively, and the D / A converter 41 Will be printed.

The D / A converter 41 converts the gain adjustment data output through the storage unit 40 into an analog signal, inputs it to the fifth filtering unit 42, and the fifth filtering unit 2 is input. After low pass filtering the gain adjustment signal, the filtered signal is provided to the gain control unit 34 as a gain adjustment signal.

Briefly summarizing the operation of the IF receiving apparatus in the CDMA mobile communication base station apparatus according to the present invention, the 70MHz IF input signal is passed through the frequency mixing section 31 having a local frequency of 48.6MHz A signal exists in the subtraction frequency band to pass through a band pass filter 32 for extracting only a signal in a 21.4 MHz band, and the signal thus passed compensates for power lost through the amplifying unit 33. Only the signals in the band remain.

Subsequently, when the amplifier 35 is passed through the gain control unit 34 and the signal is input to the demodulator 36 based on the local frequency of 21.4 MHz, the I channel signal and the Q channel signal are extracted. Then, the extracted I channel signal and the Q channel signal are converted into digital signals, respectively, and then the converted I channel data and Q channel data are demodulated through a separate demodulation dedicated device.

As described above, the IF receiving apparatus of the CDMA mobile communication base station apparatus converts a 70 MHz IF input signal into a signal of 21.4 MHz band using a mixer having a local frequency of 48.6 MHz, and then again 21.4. After extracting the I-channel signal and the Q-channel signal for the baseband signal of 3.6864 MHz by using the MHz local frequency, that is, performing a two-step frequency downconversion process, QPSK demodulation is performed. Therefore, the IF band can be increased to 70 MHz, which can accommodate baseband signals of a wider band than conventional IF receivers, resulting in more data and a larger band than conventional mobile communication systems. There is an effect to accommodate the demand.

In addition, despite the IF signal of 70MHz, there is another effect that can perform the demodulation function stably in the low range, so that the IF receiver of the CDMA mobile communication base station according to the present invention can be used as a wireless terminal in land and satellite environments. It can be effectively applied to the base station of next-generation communication service (IMT-2000) of wired and wireless integration that provides multimedia services such as data and video and global roaming.

Claims (11)

In the CDMS mobile communication base station apparatus having an RF processor and a demodulation processor, First frequency downconverting means for downconverting the IF signal input from the RF processor using an arbitrary local frequency; Second frequency downconverting means for downconverting the frequency signal downconverted from the first frequency downconverting means into baseband signals of I and Q channels using another local frequency; And A / D conversion means for converting the I channel signal and the Q channel signal down-converted from the second frequency down conversion means into I channel digital data and Q channel digital data, respectively, and outputting them to the demodulation processing apparatus. IF receiver in a CDMA mobile communication base station apparatus. 2. The apparatus of claim 1, wherein the first frequency downconverting means comprises: a first filtering unit for removing other out-of-band signal components from an IF signal received from the RF processing apparatus; A frequency mixing unit for mixing the IF signal filtered by the first filtering unit with an arbitrary local frequency provided to output a mixed signal of a sum frequency signal and a subtraction frequency signal; IF receiving apparatus in the CDMA mobile communication base station apparatus, characterized in that the second filtering unit for removing the signal components other than the subtraction frequency band to extract only the subtraction frequency signal from the mixed signal output through the frequency mixing unit . The method of claim 1 or 2, wherein the IF signal received from the RF processor is 70MHz, and the local frequency provided to the frequency mixer of the first frequency downconverting means is 48.6MHz. IF receiver in communication base station apparatus. The IF receiver of claim 2, wherein the first filtering unit is a band pass filter having a center frequency of 70 MHz. 3. The IF receiver of claim 2, wherein the second filtering unit is a band pass filter having a center frequency of 21.4 MHz equal to the subtraction frequency. 3. The apparatus of claim 1 or 2, further comprising: a first amplifier for compensating for lost power by amplifying the signal extracted by the second filtering unit of the first frequency down-converting means at a predetermined level; A gain control circuit section for controlling amplification gain of the signal output from the first amplifier section in accordance with the gain adjustment signal provided; And a second amplifier for amplifying the signal output from the gain control circuit unit to a predetermined level and outputting the signal to the second frequency downconverting means. 7. The apparatus of claim 6, wherein the gain control circuit comprises: a storage unit for storing a gain adjustment data table, and outputting gain adjustment data stored at a corresponding address according to an address designation signal provided; A D / A converter converting the gain adjustment data output from the storage into an analog signal; And an out of band signal component from the analog signal output from the D / A converter, and a filtering unit providing the removed signal as a gain adjustment signal. 10. The IF receiving apparatus of claim 7, wherein the addressing signal provided to the storage unit is I channel data and Q channel data. 2. The apparatus of claim 1, wherein the second frequency downconverting means comprises: a demodulator for separating and extracting a baseband signal of an arbitrary frequency into an I channel and a Q channel from a signal output from the first frequency downconverting means; A filtering unit which removes out-of-band signal components from the baseband signal extracted separately from the demodulation unit into the I channel and the Q channel, respectively; IF receiver in the CDMA type mobile communication base station apparatus, characterized in that the amplification section for outputting to the A / D conversion means to compensate for the lost power by a predetermined level amplification of each of the I and Q channel signals filtered by the filtering unit Device. 10. The apparatus of claim 9, wherein the demodulator comprises a frequency mixer for separating and extracting a 3.6864 MHz baseband signal into I and Q channels from a signal input from the amplifier using a local frequency of 21.4 MHz. IF receiver in CDMA mobile communication base station apparatus. 10. The IF receiver of claim 9, wherein the filtering unit is a low pass filter having a cutoff frequency of 5 MHz.