KR19980039203A - Frequency Down Conversion Circuit of Mobile Communication System Base Station by Code Division Multiple Access - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to provide a baseband signal transmission circuit of a base station of a mobile communication system capable of downconverting a radio frequency signal into a baseband signal over two orders and adjusting an integration time of a received signal strength.

The frequency downconversion circuit of the mobile communication system base station includes an eleventh amplifier 102, an eleventh voltage control attenuator 3, a twelfth amplifier 104, an eleventh bandpass filter 105, and an eleventh mixer ( 106 and a first order frequency downconverting unit (101) comprising an eleventh low pass filter (107); The thirteenth amplifier 112, the twelfth bandpass filter 113, the fourteenth amplifier 114, the twelfth voltage controlled attenuator 115, the fifteenth amplifier 116, and the thirteenth bandpass filter ( A first intermediate frequency signal processor 111 including 117); A power divider / automatic system comprising a power divider 122, a twenty-first amplifier 123, a received signal strength (RSSI) detector 124, an AGCFIR filter 125, and a first digital-to-analog converter 126. A gain adjusting unit 121; Fourteenth bandpass filter 132, thirteenth voltage controlled attenuator 133, two thirteenth mixers 134 and 135, twelfth lowpass filters 136 and l37, and two seventeenth amplifiers 138 and 139. A baseband frequency downconversion unit 131 including two analog / digital converters (140/141); an automatic gain control controller (162), and a second digital / analog converter (D / A converter); 163 and an automatic gain control unit 161 including an integrator 164.

Description

Frequency Down Conversion Circuit of Mobile Communication System Base Station by Code Division Multiple Access

The present invention relates to a mobile communication system using a code division multiple access method (CDMA), and more particularly, frequency down conversion of a base station of a mobile communication system for converting a radio frequency signal received from an antenna into a baseband signal. It is about a circuit.

1 is a frequency down conversion circuit diagram of a conventional mobile communication system base station.

Referring to FIG. 1, a frequency downconversion circuit of a base station of a mobile communication system includes a first amplifier (AMP) 2 for amplifying the power of a received signal of an antenna, and a first amplifier 2 connected to the first amplifier 2. A first voltage controlled attenuator (VTA) 3 for attenuating the output of the first voltage controlled attenuator 3 and amplifying the output of the first voltage controlled attenuator 3; 4), a first band pass filter (BPF) 5 connected to the second amplifier 4 to pass only a signal of a predetermined band among the outputs of the second amplifier 4, and the first band pass filter 5 ) Is a first mixer (MIXER: 6) for first down-converting the radio frequency signal to a 70 MHz intermediate frequency signal, and a first low pass filter (LPF) for blocking high frequency components by connecting to the first mixer (6). A first frequency down-conversion unit 1 comprising: 7); A third amplifier 12 connected to a first low pass filter 7 of the first frequency downconverter 1 to amplify the output of the first low pass filter 7, and the third amplifier l 2 A second band pass filter 13 for passing a signal of a code division multiple access channel band and a second band pass filter 13 to amplify the output of the second band pass filter 13 A second voltage controlled attenuator 15 connected to the fourth amplifier 14, attenuated so that the output of the fourth amplifier 14 is kept constant, and the second voltage controlled attenuator A fifth amplifier 16 connected to 15 to amplify the output of the second voltage controlled attenuator 15; and a fifth amplifier 16 connected to the fifth amplifier 16 to pass signals in a code division multiple access channel band. A first intermediate frequency signal processor (11) including a three band pass filter (17); A second mixer 22 connected to the third band pass filter 17 of the first intermediate frequency signal processor 11 and performing a second down conversion to an intermediate frequency signal of 4.95 MHz, and the second mixer 22; A second intermediate frequency downconverter (21) comprising a sixth amplifier (23) connected to and connected to amplify the output of the second mixer (22); Received Signal Strength Indicator (RSSI) detecting unit 54 connected to the second mixer 22 of the second intermediate frequency down-converter 21 to detect the output of the second mixer 22 as an analog voltage. ), An integrator 52 connected to the received signal strength detection unit 54 to obtain an average value thereof, and an average value of the received signal strength integrator 52 connected to the integrator 52 to convert into a predetermined amount of power. A first automatic gain control unit (51) including an automatic gain control driver (AGC Driver) 53 which is supplied to the second voltage control attenuator 15 of the first intermediate frequency signal processor 11; A fourth band pass filter 32 connected to the sixth amplifier 23 of the second intermediate frequency downconverter 21 and passing a signal of a predetermined band among the outputs of the sixth amplifier 23; A third voltage controlled attenuator 33 and a third voltage controlled attenuator 33 connected to the four band pass filter 32 to attenuate the output of the fourth band pass filter 32 to be kept constant. Two third mixers 34 and 35 and a third mixer 34 and 35 for converting a 4.95 MHz intermediate frequency band signal to a base band In-Phase and Quadrature-Phase (IQ) signal. Second low pass filters 36 and 37 for removing high frequency components from baseband IQ signals, respectively; and second low pass filters 36 and 37, respectively. Two seventh amplifiers 38.39, which amplify the output of the < RTI ID = 0.0 > 37, < / RTI > Baseband frequency downconverter (31) comprising two analog / digital converters (40, 41) for converting the inverse IQ signal into four-bit digital samples and outputting them to the digital sample muxing section. )Wow; An automatic gain control controller 62 which is connected in common to the output terminals of the analog / digital converters 40 and 41 of the baseband frequency down-converter 31 to obtain the instantaneous power of the digital sample, and the automatic gain control controller 62 Digital / analog converter (D / A Converter) 63 for digital / analog conversion of the output of the automatic gain control controller 62, and the digital / analog converter 63 for the digital / analog converter 63. It is composed of a second automatic gain control unit 61 including an integrator (64) for obtaining the average power of the ()) and outputs it to the third voltage control attenuator (33) of the baseband frequency down-conversion section (31).

In general, a surface acoustic wave BPF is used as the second bandpass filter 2 and the third bandpass filter 13, and Gilbert Cell Mixer is an active mixer as the mixers 6,22,34,35. Use

The operation of the frequency downconversion circuit of the mobile communication system base station of the conventional mobile communication system base station will be described.

The first frequency down converter 1 converts the radio frequency signal of 800 MHz into an intermediate frequency signal of 70 MHz.

The first intermediate frequency signal processing 11 amplifies the 70 MHz intermediate frequency signal converted first, removes unnecessary frequency components of the intermediate frequency of 70 MHz, and according to the output voltage of the first automatic gain control unit 51. Maintain a constant signal level. At this time, the received signal strength integrator 52 implemented using the operational amplifier averages the received signal strength of the second mixer 22 for a predetermined time.

The second frequency down converter 21 converts a radio frequency signal of 70 MHz into an intermediate frequency signal of 4.95 MHz and amplifies the converted signal.

The baseband frequency downconversion unit 31 converts a radio frequency signal of 4.95MHz into a baseband signal, removes the high frequency component of the converted signal, converts the digital signal into a digital signal, and transmits the digital signal to the digital sample muxing unit. At this time, the second automatic gain control unit 61 inputs a baseband digital signal transmitted to the digital sample muxing unit to maintain a constant signal level input to the third mixer 34.

According to a conventional frequency downconversion circuit of a base station of a mobile communication system, a baseband digital signal is generated by downconverting a radio frequency signal received at a reception antenna over three orders, and thus a circuit is complicated and noise is inserted in the downconversion step. There is a concern that the first automatic gain adjustment circuit integrator has a problem in that the integration time of the received signal intensity is determined so that the second voltage control attenuator cannot be efficiently controlled, and it is implemented in analog to degrade assembly and mass production.

An object of the present invention is to provide a baseband signal transmission circuit of a mobile communication system base station capable of down-converting a radio frequency signal into a baseband signal over two orders and adjusting an integration time of received signal strength.

1 is a frequency downconversion circuit diagram of a conventional mobile communication system base station;

2 is a frequency downconversion circuit diagram of a mobile communication system base station;

* Explanation of symbols for main parts of the drawings

AMP: Amplifier VTA: Voltage Controlled Attenuator

BPF: Bandpass Filter LPF: Lowpass Filter

Power Splitter: Power Splitter A / DC: Analog / Digital Converter

D / AC: Digital / Analog Converter MIX: Mixer

AGCD: Automatic Gain Control Driver INT: Integrator

AGCC: Automatic Gain Control Controller RSSI: Received Signal Strength Detector

2 is a frequency downconversion circuit diagram of a mobile communication system base station according to the present invention.

Referring to FIG. 2, the frequency downconversion circuit of the base station of the mobile communication system is connected to the eleventh amplifier 102 for amplifying the power of the received signal of the antenna and the output of the eleventh amplifier 102 by being connected to the eleventh amplifier 102. An eleventh voltage controlled attenuator (3) for attenuating the signal according to the control voltage, a twelfth amplifier (104) connected to the eleventh voltage controlled attenuator (I03), and amplifying the output of the eleventh voltage controlled attenuator (l03); An eleventh band pass filter 105 connected to the twelfth amplifier 104 for passing only signals of a predetermined band among the outputs of the twelfth amplifier 104, and an eleventh band pass filter 105 connected to the eleventh band pass filter 105 A first order comprising an eleventh mixer 106 for first downconverting the signal to a 70 MHz intermediate frequency signal and an eleventh low pass filter 107 connected to the eleventh mixer 106 to block radio frequency components; A frequency down converter 101; A thirteenth amplifier 112 connected to an eleventh low pass filter 107 of the first frequency downconverter 101 to amplify the output of the eleventh low pass filter 107, and the thirteenth amplifier 112 A 12th bandpass filter 113 for passing a signal of a code division multiple access channel band and a 12th bandpass filter 113 to amplify the output of the 12th bandpass filter 113 A fourteenth amplifier 114, a twelfth voltage controlled attenuator 115 connected to the fourteenth amplifier 114, and attenuated to maintain a constant output of the fourteenth amplifier 114; and the twelfth voltage controlled attenuator A fifteenth amplifier 116 connected to a 115 to amplify the output of the twelfth voltage controlled attenuator 115; a fifteenth amplifier 116 connected to the fifteenth amplifier 116 to pass a signal of a code division multiple access channel band; First Intermediate Frequency Signal Including 13-Band Filter 117 A processing unit 111; A power splitter 122 connected to a thirteenth band pass filter 117 of the first intermediate frequency signal processor 111 to distribute an output of the thirteenth band pass filter 117, and the power divider A twenty-first amplifier 123 for amplifying the intermediate frequency signal distributed by the power divider 122 and a received signal of the intermediate frequency signal distributed by the power divider 122 by being connected to the power divider 122. AGCFIR (Finite Impulse Response), which is connected to the reception signal strength (RSSI) detection unit 124 for detecting the intensity at the voltage level and the reception signal strength detection unit 124 and averaging the received signal intensity in the voltage level and outputs it as a digital value. A power distribution / auto gain adjusting unit 121 comprising a filter 125 and a first digital / analog converter 126 connected to the AGC FIR filter l25 and digitally converting the output of the AGC FIR filter 125. )Wow; A fourteenth bandpass filter 132 connected to the twenty-first amplifier 123 of the power distribution / auto gain adjusting unit 121 and passing a signal of a predetermined band, and a fourteenth bandpass filter 132 connected to the fourteenth bandpass filter 132 A baseband IQ is connected to a thirteenth voltage controlled attenuator 133 and a thirteenth voltage controlled attenuator 133 to attenuate the output of the fourteen bandpass filter 132 so that the output of the bandpass filter 132 remains constant. Two twelfth mixers 134 and 135 for converting into signals, twelfth low pass filters 136 and 137 connected to the thirteenth mixers 134 and 135, respectively, to remove high frequency components from the baseband IQ signal, and the twelfth low band. Two seventeenth amplifiers 138 and 139 which are respectively connected to the pass filters 136 and 137 to amplify the output of the twelfth low pass filter 136 and 137, and which are connected to the seventeenth amplifiers 138 and 139, respectively, to receive baseband IQ signals. 4-bit digital Flow converted to digital samples Muxing two analog / digital converter to the output portion (Muxing): base band frequency down-conversion unit 131 including the (A / D Converter 140,141) and; To the automatic gain control controller 162 and the automatic gain control controller 162 which are connected in common to the output terminals of the analog / digital converters 140 and 141 of the baseband frequency downconverter 131 to obtain the instantaneous power of the digital samples. A second digital / analog converter (163) which connects the output of the automatic gain control controller 162 to digital / analog conversion, and a second digital / analog converter 163 that is connected to the second digital / analog converter (163). The automatic gain control unit 161 includes an integrator 164 that obtains an average value of the output of the analog converter 163 and outputs the result to the thirteenth voltage controlled attenuator 133 of the baseband frequency downconverter 131.

AGC FIR filter 125 is implemented with one FPGA (Field Programmable Gate Array), which can adjust the average time of received signal intensity indicated by voltage level by using external processor. Reference text (Book title: Digital Signal Processing, Author) : Impulse Response, detailed in Hwang Won-won, Lee Ju-shin, Publisher: Ohmsa, p.

It is preferable to design the delay stage N = 64 and the Hamming coefficient a = 0.54 at w (nT) = a + (1-a) cos (2πn / (N-1)).

An operation of the frequency downconversion circuit of the base station of the mobile communication system according to the present invention will be described.

The operations of the first frequency down-converter 101 and the first intermediate frequency signal processor 111 are the same as in the conventional case.

The power divider 122 of the power divider / auto gain controller 121 distributes the output of the thirteenth bandpass filter 117 to the received signal strength detector 124 and the twenty-first amplifier 123, and receives the received signal strength detector ( 124 detects the received signal strength of the intermediate frequency signal distributed by the power divider 122 at a voltage level, and the AGC FIR filter 125 averages the received signal strength and outputs it as a digital value.

The digital output of the AGC FIR filter 125 is converted into an analog signal and input to the twelfth voltage control attenuator 115 of the first intermediate frequency signal processor 111.

The baseband frequency down converter 131 converts the 70 MHz intermediate frequency signal into a baseband signal, removes the high frequency component of the converted signal, converts the digital signal into a digital signal, and transmits the digital signal to the digital sample muxing unit. At this time, the second automatic gain control unit 161 inputs the baseband digital signal transmitted to the digital sample muxing unit and maintains the signal level input to the thirteenth mixers 134 and 135 constant.

As described above, according to the frequency downconversion circuit of the base station of the mobile communication system according to the present invention, since the baseband digital signal is generated by downconverting the radio frequency signal received at the receiving antenna over two steps, the circuit becomes simpler. Less noise is inserted in the down-conversion step, and the integration time of the received signal sensitivity can be set appropriately from the outside to efficiently control the voltage-controlled attenuator of the first intermediate frequency signal processor, and it is also implemented as a digital circuit. And mass productivity can be raised.

Claims (1)

An eleventh amplifier 102 that amplifies the power of the received signal of the antenna, and an eleventh voltage control attenuator 3 connected to the eleventh amplifier 102 to attenuate the output of the eleventh amplifier 102 according to a control voltage. A twelfth amplifier 104 connected to the eleventh voltage controlled attenuator 1o3 to amplify the output of the eleventh voltage controlled attenuator 103, and a twelfth amplifier 104 connected to the twelfth amplifier 104; And an eleventh band pass filter 105 for passing a signal band of a predetermined band and an eleventh down conversion of a radio frequency signal to a 70 MHz intermediate frequency signal by being connected to the eleventh band pass filter 105. A first frequency downconverting unit (101) comprising a mixer (106) and an eleventh low pass filter (107) connected to the eleventh mixer (106) to block radio frequency components; A thirteenth amplifier 112 connected to the eleventh low pass filter 107 of the first frequency downconverter 101 to amplify the output of the eleventh low pass filter 107, and the thirteenth amplifier 112 A 12th bandpass filter 113 for passing a signal of a code division multiple access channel band and a 12th bandpass filter 113 to amplify the output of the 12th bandpass filter 113. A fourteenth amplifier 114, a twelfth voltage controlled attenuator 115 connected to the fourteenth amplifier 114, and attenuated to maintain a constant output of the fourteenth amplifier 114; and the twelfth voltage controlled attenuator A fifteenth amplifier 116 connected to a 115 to amplify the output of the twelfth voltage controlled attenuator 115; a fifteenth amplifier 116 connected to a fifteenth code channel to pass a signal of a code division multiple access channel band; Primary intermediate frequency scene including 13 bandpass filter 117 Processor 111 and; A power splitter 122 connected to a thirteenth band pass filter 117 of the first intermediate frequency signal processor 111 and distributing an output of the thirteenth band pass filter 117; A twenty-first amplifier 123 for amplifying the intermediate frequency signal distributed by the power divider 122 and a received signal of the intermediate frequency signal distributed by the power divider 122 by being connected to the power divider 122. AGC FIR (Finite Impulse), which is connected to the reception signal strength (RSSI) detection unit 124 for detecting the intensity at a voltage level and the reception signal strength indicated by the voltage level, is output in a digital value. Response) A power distribution / auto gain adjusting unit comprising a filter 125 and a first digital / analog converter 126 connected to the AGC FIR filter 125 and digitally converting the output of the AGC FIR filter 125 ( l2l); A fourteenth bandpass filter 132 which is connected to the twenty first amplifier 123 of the power distribution / auto gain adjusting unit l21 and passes a signal of a predetermined band, and is connected to the fourteenth bandpass filter 132 to A baseband IQ is connected to a thirteenth voltage controlled attenuator 133 and a thirteenth voltage controlled attenuator 133 to attenuate the output of the fourteen bandpass filter 132 so that the output of the bandpass filter 132 remains constant. Two twelfth mixers 134 and 135 for converting into signals, twelfth low pass filters 136 and 137 connected to the thirteenth mixers 134 and 135, respectively, to remove high frequency components from baseband IQ signals, and the twelfth low band. Two seventeenth amplifiers 138 and 139 connected to the pass filters 136 and 137 to amplify the output of the twelfth low pass filter 136 and 137, and baseband IQ signals connected to the seventeenth amplifiers l38 and 139, respectively. Digit of 4 bits each Converting the digital samples in sample Muxing (Muxing) 2 analog / digital converter to output to: base band frequency down conversion portion (13l) containing the (A / D Converter 140,141) and; An automatic gain control controller 162 for obtaining instantaneous power of a digital sample by commonly connecting to the output terminals of the analog / digital converters 140 and l41 of the baseband frequency down-converter 131, and the automatic gain control controller 162. Second digital / analog converter 163 for digital / analog converting the output of the automatic gain control controller 162, and the second digital / analog converter 163 for a second digital / analog converter 163. And an automatic gain control unit 161 including an integrator 164 that obtains an average value of the output of the digital / analog converter 163 and outputs the average value to the thirteenth voltage controlled attenuator 133 of the baseband frequency downconversion unit 131. A baseband signal transmission circuit of a base station of a mobile communication system, characterized in that.