KR20040022983A - Device for generating cdma signal - Google Patents

Abstract

PURPOSE: An apparatus for generating a CDMA(Code Division Multiple Access) signal is provided to generate the CDMA signal using a Zener diode and a SAW(Surface Acoustic Wave) filter. CONSTITUTION: An AWGN(Additive White Gaussian Noise) signal generating unit(100) has a Zener diode and an impedance matching unit. The Zener diode generates an AWGN. The impedance matching unit matches the impedance of the Zener diode. The first narrow band amplifying unit(200) amplifies the signal outputted from the impedance matching unit. A BPF(Band Pass Filter) unit(300) passes only a signal with a specific frequency band from the signal outputted from the first narrow band amplifying unit(200). The second narrow band amplifying unit(400) amplifies the signal outputted from the BPF unit(300). A SAW filter unit(500) filters the signal outputted from the second narrow band amplifying unit(400), and outputs the CDMA signal.

Description

CD AM signal generator {DEVICE FOR GENERATING CDMA SIGNAL}

The present invention relates to a signal generator, and more particularly, to a device for generating a CDMA signal using a zener diode and a SAW filter.

The CDMA signal source is one of the equipment that must be provided as a measurement device when developing or testing the characteristics of devices used in mobile communication. The CDMA signal generator generates an I, Q digital signal and then generates a CDMA signal through an IQ modulator. Using the generated CDMA signal, mobile communication device developers can measure various characteristics of the mobile communication device.

However, when developing a device (HPA, LPA, LNA, repeater, etc.) used for mobile communication or measuring its characteristics, the measurement equipment (Spectrum Analyzer, Power Meter, etc.) is 100% foreign equipment and domestic equipment is not developed. The reality is that In particular, for CDMA signal generators, handset manufacturers pay huge royalties to Qualcomm in the United States and are almost subordinate to Agilent in the US for all their measurement equipment. In addition, although general signal generators such as CW, FM, AM, etc. have been developed and produced in Korea, their number is only a small number, and in particular, CDMA signal generators are not produced at all.

FIG. 1A is a block diagram schematically showing a conventional CDMA signal generating apparatus, and FIG. 1B is a diagram showing a waveform of a generated CDMA signal.

The conventional CDMA signal generator is composed of an I FIR filter 10 for filtering I data, a Q FIR filter 11 for filtering Q data, and an IQ demodulator 12 for demodulating the filtered I data and Q data. I data (or channel) or Q data (or channel) is a digital signal with a data rate of 1.2288 Mcps, which is the product of two PN code pairs multiplied by the user's speech data multiplied by Walsh code after convolutional coding and symbol modulation. .

However, as shown in FIG. 1, in order to generate a CDMA signal, an apparatus for generating I data and Q data is required, but there is a problem in that it cannot be produced by domestic technology.

In addition to the above-described problems, the reason why the CDMA signal generator cannot be developed in Korea is as follows.

Using other components that are currently commercialized, there is a problem in that the characteristics as a measurement instrument with high accuracy enough to measure CDMA-related equipments cannot be realized. In addition, foreign equipment companies, which are reluctant to leak the core technology, do not sell specific parts related to CDMA signal generators, and thus, I data and Q data generating parts cannot be obtained.

Accordingly, an object of the present invention is to provide a CDMA signal generating apparatus capable of generating the CDMA signal shown in Fig. 1B without using I data and Q data.

Another object of the present invention is to provide a CDMA signal generating apparatus capable of generating the CDMA signal shown in FIG. 1B without performing IQ modulation.

1A is a block diagram schematically showing a conventional CDMA signal generator.

1B shows waveforms of the generated CDMA signal.

2 is a block diagram of a CDMA signal generating apparatus according to a preferred embodiment of the present invention.

3A-3E show output signals from each block of FIG.

4 is a circuit diagram of a CDMA signal generator according to a preferred embodiment of the present invention.

5 is a flowchart illustrating a CDMA signal generation method according to a preferred embodiment of the present invention.

According to a preferred embodiment of the present invention, a device for generating a CDMA signal, comprising: a zener diode for generating AWGN, an impedance matching unit for matching impedance between the zener diode and the CDMA signal generator; A first narrowband amplifier for amplifying the signal output from the impedance matching unit, a bandpass filter for passing only a signal of a specific frequency band among the signals output from the first amplifier, and an output from the bandpass filter Provided is a CDMA signal generating apparatus including a second narrowband amplifier for amplifying a signal and a SAW filter unit for filtering a signal output from the second narrowband amplifier and outputting a CDMA signal.

Here, the first amplifying unit and the second amplifying unit amplify the 30 MHz 70MHz band of the input signal, the band pass filter is an LC filter having a S21 characteristic of up to 5dB to pass only the 70MHz band of the input signal.

In addition, the SAW filter unit may include an SAW filter, an input impedance matching circuit coupled to an input terminal of the SAW filter, and an output impedance matching circuit coupled to an output terminal of the SAW filter.

According to the present invention, the AWGN generated by the control diode is used in place of the I data and the Q data, and the SAW filter is used in place of the FIR filter, thereby generating the same signal through the analog processing as the CDMA signal generated through the conventional digital processing. It relates to an apparatus and a method. Generally, a base station consists of a front-end unit, an up-down converter, an intermediate frequency (IF) processing unit, and a channel card. Only a dual channel card processes the input signal digitally, and the rest of the equipment is analog type. Processes the input signal.

When the CDMA signal in which the I data and the Q data are modulated on an arbitrary carrier is analogized, it can theoretically be regarded as noise collected in a specific band. In other words, a lot of noise can be interpreted as having a band of 1.23MHz. Thus, I data and Q data may be replaced with AWGN. Here, the additive white gaussian noise (AWGN) refers to the existing noise over all frequency bands.

However, since natural AWGN is very small (-128dBm @ 30KHz RBW), it is difficult to use it as a substitute for I data and Q data. Therefore, another AWGN generator is needed, and the zener diode is used in the present invention.

When a breakdown voltage is applied across the zener diode, a sudden increase in the carrier causes collision of the carrier and free electrons so that each free electron is out of orbit and an arbitrary frequency having a frequency fx is generated. That is, AWGN is generated. The AWGN thus generated has an amount of -70 dBm @ 30 KHz RBW available after sufficient amplification as an alternative signal for I data and Q data in the present invention.

The AWGN generated by the Zener diode is selectively amplified and filtered only in the CDMA frequency band and then adjusted to the CDMA signal waveform defined by IS 95 * through the SAW filter.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram of a CDMA signal generating apparatus according to a preferred embodiment of the present invention, and FIGS. 3A to 3E are diagrams showing signals output from respective components of FIG.

Referring to FIG. 2, the CDMA signal generator according to the present invention includes an AWGN signal generator 20, a narrow band amplifier 30, a band pass filter 40, a narrow band amplifier 50, and a SAW filter unit 60. It consists of.

The AWGN signal generator 20 is composed of a zener diode and an impedance matching circuit. When a voltage equal to or higher than the breakdown voltage is applied to both ends of the zener diode, free electrons in the orbit are emitted, and an electric signal having an arbitrary frequency fx is generated. Here, the arbitrary frequency fx is AWGN existing over the entire frequency band, as shown in FIG. 3A, signals of minute power over the entire frequency band. The AWGN generated by the zener diode has a size of -70dBm @ 30KHz RBW. The impedance matching circuit matches the impedance between the zener diode and other parts of the CDMA signal generator so that the AWGN generated by the zener diode is input to the narrowband amplifier 30 without loss. Here, the impedance matching circuit is composed of at least one capacitor and at least one inductor, and may be implemented in any form of a passive impedance matching circuit or an active impedance matching circuit.

The narrowband amplifier 30 has an input coupled to the output of the AWGN signal generator 20 and amplifies the AWGN of the 70 MHz band input from the AWGN signal generator 20. Here, the gain of the narrowband amplifier 30 is preferably 30 dB. As shown in FIG. 3B, it can be seen that the signal output from the narrowband amplifier 30 is a signal amplified by about 30 dB from the signal of FIG. 3A.

The band pass filter 40 has an input terminal coupled to an output terminal of the narrow band amplifier 30, and receives a signal output from the narrow band amplifier 30 and passes only signals in the 70 MHz band. Here, the band pass filter 40 has a characteristic of S21: Max 5dB. As shown in FIG. 3C, the signal output from the band pass filter 40 passes only signals in the 70 MHz band, and signals in other frequency bands are blocked.

In another preferred embodiment, a plurality of band pass filters 40 may be applied to the CDMA signal generator according to the present invention, and narrow band amplifiers may be additionally connected between the plurality of band pass filters, thereby increasing frequency selectivity.

The narrowband amplifier 50 has an input coupled to the output of the bandpass filter 40 and amplifies a signal in the 70 MHz band by receiving an output signal attenuated by the bandpass filter 40. Here, the gain of the narrowband amplifier 50 is preferably 30dB. As shown in FIG. 3D, it can be seen that the output signal of the narrowband amplifier 50 has been amplified by about 30 dB over the output signal of FIG. 3C.

The SAW filter unit 60 includes an input stage impedance matching circuit with a narrowband amplifier 50 located at an input stage, an SAW filter coupled to an input stage impedance matching circuit, and an output stage impedance matching circuit coupled to an output stage of the SAW filter. The SAW filter unit 60 is a component corresponding to the FIR filter of the conventional CDMA signal generator, and performs a filtering function for converting the output signal of the narrowband amplifier 50 into a signal conforming to the IS 95 * standard. The waveform of the output signal of the SAW filter unit 60 is shown in FIG. 3E. The ISDMA * CDMA signal specifications are shown in the table below.

Table 1

Item standard Bandwidth 1.23 MHz fc ± 750 KHz -29dBc @ 30KHz RBW fc ± 1.98 MHz -44dBc @ 30KHz RBW fc ± 2.23 MHz -44dBc @ 30KHz RBW

In another preferred embodiment, a plurality of SAW filter units 60 may be applied to the CDMA signal generator according to the present invention.

4 is a circuit diagram of a CDMA signal generator according to a preferred embodiment of the present invention.

Referring to FIG. 4, the CDMA signal generator includes an AWGN signal generator 100, a narrow band amplifier 150, a band pass filter 200, a narrow band amplifier 250, and a band in which respective input / output terminals are coupled in series. The pass filter 300, the narrow band amplifier 350, the SAW filter unit 400, the narrow band amplifier 450, and the SAW filter unit 500 are configured.

The AWGN signal generator 100 includes a zener dial 110 and an impedance matching circuit, and one terminal is coupled to a driving power supply, and the other terminal is grounded between the bypass capacitor 101 and the driving power supply and the ground. Between the bias resistor 102, the harmonic current blocking inductor 103 and the zener diode 110 connected in series to the contact point of the inductor 103 and the zener diode 110, and the other side of the inductor 105 having one side grounded. And a capacitor 104 coupled to it. Here, in the Zener diode 110, the P terminal is coupled to the contact of the inductor 103 and the capacitor 104, and the N terminal is grounded.

The narrowband amplifier 150 includes a coupling capacitor 152 for blocking DC current coupled between the input terminal of the narrowband amplifier 150 and the RF amplifier 154, an inductor 151 coupled between the input terminal ground, A bypass capacitor 152 coupled to the input of the RF amplifier 154, the RF amplifier 154, a resistor 155 and an inductor 156 coupled in series between the drive power source and the output of the RF amplifier 154. And a bypass capacitor 157 coupled between the contact of the resistor 155 and the inductor 156 and ground, and a bypass capacitor 158 and a coupling capacitor 159 coupled to the output terminal of the RF amplifier 154. It includes. Since the structures of the narrowband amplifiers 250, 350, and 450 are the same as those of the narrowband amplifier 150 described above, description thereof will be omitted.

The input ends of the band pass filters 200 and 300 are respectively coupled to the output ends of the narrow band amplifiers 150 and 250, and the output signals are applied to the input ends of the narrow band amplifiers 250 and 350. The band pass filter 200 has a characteristic of S21: Max 5dB, passes only the 70MHz band, and blocks the remaining bands.

The input terminal of the SAW filter unit 400 is coupled to the output terminal of the narrowband amplifier 350, an input impedance matching circuit matching an impedance between the SAW filter and all SAW filters, a SAW filter having an input coupled to the input impedance matching circuit, and It consists of an output impedance matching circuit that matches the impedance between the SAW filter and the circuit after the SAW filter. The SAW filter unit 400 includes an impedance matching inductor 402 coupled between the input terminal of the SAW filter unit 400 and the SAW filter 403, and the impedance matching coupled between the input terminal of the SAW filter unit 400 and ground. For the capacitor 401, the SAW filter 403, the output terminal of the SAW filter unit 400 and the impedance matching inductor 404 coupled between the output terminal of the SAW filter 403 and the output terminal of the SAW filter unit 400. And an impedance matching capacitor 405 coupled between ground and ground. Since the structure of the SAW filter unit 500 is the same as that of the SAW filter unit 400 described above, description thereof will be omitted.

5 is a flowchart illustrating a CDMA signal generating method according to a preferred embodiment of the present invention.

In step S100, a voltage equal to or higher than the breakdown voltage is applied to both ends of the zener diode to generate an AWGN of -70dBm @ 30KHz RBW. The generated AWGN is applied to the narrowband amplifier via an impedance matching circuit.

In step S110, the narrowband amplifier narrow-band amplifies the generated AWGN. Here, the narrowband amplifier amplifies only the signal of the 70MHz band by 30dB. The amplified AWGN is applied to the band pass filter.

In step S120, the band pass filter passes only the 70 MHz band of the narrow band amplified AWGN and blocks the remaining bands. The bandpassed AWGN is applied to the narrowband amplifier.

In step S130, the narrowband amplifier narrow-band amplifies the bandpassed AWGN. Here, the narrowband amplifier amplifies only the signal of the 70MHz band by 30dB. The bandpassed AWGN is applied to the SAW filter portion. Here, the AWGN may be extracted by gradually adjusting the amplification band and the pass band and repeatedly performing steps S120 to S130.

In step S140, the SAW filter unit receives the amplified AWGN and adjusts the waveform to the CDMA signal according to the IS 95 * standard. Here, by repeatedly executing step S140 using the plurality of SAW filter units, a CDMA signal conforming to the IS 95 * standard may be generated.

As described above, in the present specification, instead of I data and Q data, AWGN, which is noise existing over the entire frequency band, is generated by using a Zener diode, and instead of the FIR filter to analogize the entire process of CDMA signal generation. An apparatus and method for generating a CDMA signal conforming to the IS 95 * standard by using the SAW filter have been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention. In addition, the scope of the present invention can be interpreted only by the claims described below.

As described above, the present invention provides an apparatus and method capable of generating a CDMA signal using a commercially available zener diode instead of separate apparatus for generating I data and Q data.

Therefore, it is possible to implement the characteristics of the measuring equipment that can not be obtained with commercially available components, thereby replacing the expensive foreign measuring equipment.

In addition, the present invention by analogizing the entire process of CDMA signal generation using the SAW filter, it is possible to generate the same CDMA signal without using the FIR filter which is an essential component of the conventional CDMA signal generator.

Claims (4)

In a device for generating a CDMA signal, Zener diodes generating AWGN; An impedance matching unit matching an impedance between the zener diode and the CDMA signal generator; A first narrowband amplifier for amplifying the signal output from the impedance matching unit; A band pass filter configured to pass only a signal of a specific frequency band among the signals output from the first amplifier; A second narrowband amplifier for amplifying the signal output from the band pass filter; And And a SAW filter unit for outputting a CDMA signal by filtering the signal output from the second narrowband amplifier. The method of claim 1, And the first amplifying unit and the second amplifying unit are narrowband amplifying units for amplifying a 70 MHz band of the input signal by 30 dB. The method of claim 1, And the band pass filter part is an LC filter having an S21 characteristic of a maximum of 5 dB passing only a 70 MHz band of an input signal. The method of claim 1, The SAW filter unit, SAW filter; An input impedance matching circuit coupled to the input of the SAW filter; And And an output impedance matching circuit coupled to the output end of the SAW filter.