KR20030058414A - Multi-frequency band transceiver by way of variable band pass filter - Google Patents

Abstract

PURPOSE: A multi-frequency band transceiver using a variable band pass filter is provided to adjust a frequency band according to a service frequency band. CONSTITUTION: Control units(312,332) generate control signals for adjusting central frequencies according to service frequency bands. Variable band pass filters(313,333) decide central frequencies according to the control signals received from the control units(312,332). Each of the control units(312,332) has a control signal generator for generating a digital control signal, and a digital to analog converter for converting the digital control signal into an analog control signal and providing the analog control signal to the variable band pass filter(313,333).

Description

MULTI-FREQUENCY BAND TRANSCEIVER BY WAY OF VARIABLE BAND PASS FILTER}

The present invention relates to a transceiver of a mobile communication system, and more particularly to a transceiver having a band pass filter.

The number of mobile subscribers in Korea is increasing year by year, and accordingly, the mobile communication service market is growing rapidly. In addition, as the replacement of equipment of mobile communication systems is expected to be accelerated by the introduction of high-speed data packet transmission service, wireless application protocol (WAP), and Bluetooth, the parts market for components of mobile communication systems is also growing every year.

In addition, with the development of such mobile communication systems, communication service providers are facing frequency resource problems. This is true not only for the frequency between domestic service providers, but also for the service of the mobile communication system between countries. Currently in Korea, cellular (Cellular), 900S, PCS (personal communication service) 1.8GHz, IMT-2000 (International Mobile Telecommunications-2000) uses a frequency band of 2GHz to provide a communication service to mobile subscribers. As such, as the service frequency band becomes higher and higher, research on a transceiver is important as a part that plays an important role in lowering or increasing a frequency as a signal required for digital modulation.

1 is a block diagram of a transmitter and receiver commonly used. As shown, the transceiver 100 is a device for transmitting / receiving in which a receiver (PART OF TRANSMITTER) 110 and a transmitter (PART OFRECEIVER: 130) are combined into one package.

The receiver 110 includes a low noise amplifier 111, a band pass filter 113, a frequency mixer 115, an intermediate frequency amplifier 117, and a SAW BPF (119: SURFACE ACOUSTIC WAVE BAND PASS FILTER).

In the receiver 110, a radio frequency (RF) signal input from an antenna is amplified by the low noise amplifier 111. The band pass filter 113 filters the amplified signal in a frequency band determined at a specific center frequency. The filtered signal in the frequency mixer 115 is an intermediate frequency through a multiplication in the time domain and a convolution in the frequency domain with the signal generated by the local generator 120. Is converted to IF) signal. The intermediate frequency signal is amplified to a signal of a desired level while passing through the intermediate frequency amplifier 117. The intermediate frequency signal amplified by the SAW BPF 119 restores the original signal and channelizes the attenuated signal. As a result, the receiving end 110 finishes receiving the signal.

The transmitter 130 includes a high output amplifier 131, a band pass filter 133, a frequency mixer 135, an intermediate frequency amplifier 137, and a SAW BPF (139: SURFACE ACOUSTIC WAVE BAND PASS FILTER).

The transmitter 130 filters the input intermediate frequency signal by the SAW BPF 139 and amplifies the intermediate frequency signal into a signal of a desired level by the intermediate frequency amplifier 137. The amplified intermediate frequency signal is converted into a radio frequency signal by mixing the signal generated by the local oscillator 120 and the frequency mixer 135. The band pass filter 133 filters the radio frequency signal in a frequency band determined by a specific center frequency and transmits the radio frequency signal to the high output amplifier 131. The high output amplifier 131 transmits power through an antenna by amplifying the input signal.

FIG. 2 is a state diagram showing the configuration (a) and equivalent circuit (b) of the band pass filters 113 and 133 shown in FIG.

Referring to FIG. 2, (a) shows band pass filters 113 and 133 composed of a plurality of dielectric resonators 200. The plurality of dielectric resonators 200 selects only a specific center frequency from radio waves received from the antenna. Accordingly, the band pass filters 113 and 133 composed of the plurality of dielectric resonators 200 filter only signals of a frequency band determined by a specific center frequency. The plurality of dielectric resonators 200 are often referred to as tuning circuits. (b) shows an equivalent circuit of the plurality of dielectric resonators 200 constituting the band pass filter. The plurality of dielectric resonators 200 includes a plurality of coils and a plurality of capacitors.

As described above, the band pass filters 113 and 133 composed of the plurality of dielectric resonators 200 may filter only signals of a frequency band according to a specific center frequency because the value of the capacitor is determined.

However, in the design of a transceiver, a band pass filter used to suppress inflow of unnecessary frequency band bands or unnecessary center frequencies in a mobile communication system is designed because the frequency band is fixed to fit a specific center frequency. There was a problem in that it cannot accommodate the service frequency band provided by the service provider. That is, since the transceiver is installed once, the center frequency is fixed, there is a problem that the transceiver must be replaced in order to use it in another service frequency band.

Accordingly, it is an object of the present invention to solve the problems of the prior art operating as described above, to provide a transceiver for adjusting the frequency band according to the service frequency band.

Another object of the present invention is to provide a variable band pass filter for varying a center frequency according to a control signal and filtering an input signal in a frequency band determined by the varying center frequency.

In order to achieve the above object, an embodiment of the present invention provides a transceiver for a mobile communication system operating in a predetermined service frequency band.

A control unit for generating a control signal for adjusting a center frequency according to a service frequency band and providing the control signal to a variable band pass filter;

And a reversible band pass filter configured to filter the input signal by determining a center frequency according to the control signal received from the controller.

1 is a block diagram of a transceiver generally used.

Fig. 2 is a state diagram showing the configuration (a) and equivalent circuit (b) of the band pass filter shown in Fig. 1.

Figure 3 is a block diagram showing a transceiver using a variable band pass filter in accordance with the present invention.

4 is a state diagram showing a configuration (a) and an equivalent circuit (b) of the variable band pass filter shown in FIG.

5 is a simplified equivalent circuit diagram of the variable capacitance diode 420 mentioned in FIG.

6 is a detailed block diagram illustrating a control unit for controlling a variable band pass filter.

7 is a center frequency change graph of a transceiver for constructing multiple frequency bands according to the present invention;

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. Like reference numerals are used to designate like elements even though they are shown in different drawings, and detailed descriptions of related well-known functions or configurations are not required to describe the present invention. If it is determined that it can be blurred, the detailed description thereof will be omitted. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

3 is a block diagram illustrating a transmission and reception apparatus using a variable band pass filter according to the present invention. As shown, the transceiver 300 is a device for transmitting / receiving in which a receiver (PART OF TRANSMITTER) 310 and a transmitter (PART OF RECEIVER: 330) are combined into one package.

The receiver 310 includes a low noise amplifier 311, a variable band pass filter 313, a frequency mixer 315, an intermediate frequency amplifier 317, and a SAW BPF 319 (SURFACE ACOUSTIC WAVE BAND PASS FILTER) and the variable band. The control unit 312 sends a control signal to the pass filter 313.

In the receiver 310, the low noise amplifier 311 determines a noise index of a radio frequency signal (RF) signal input from an antenna and amplifies it while minimizing noise power generated when amplifying the radio frequency signal. . The variable band pass filter 313 including a plurality of dielectric resonators and a variable capacitor diode filters the amplified radio frequency signal in a frequency band determined according to a specific center frequency. The signal filtered by the variable band pass filter 333 is not a fixed center frequency but an input signal in a frequency band determined by the center frequency by adjusting the center frequency by a control signal of a control signal generator of the controller 312. It is a device for filtering.

The filtered signals are converted into an intermediate frequency signal through a local oscillation signal generated by the local oscillator 320 in the frequency mixer 315 and a multiplication in the time domain, and a convolution in the frequency domain. Is converted. Here, the LOCAL OSCILLATOR 320 is a device that generates a local oscillation signal that is a pure cosine wave (COSINE WAVE) that is not modulated, and is generally a PLL (PHASE LOCKED LOOP) by a digital control signal (DATA, CLOCK, ENABLE). ) To generate a frequency that is smaller or larger than the antenna input frequency signal by the desired intermediate frequency. The intermediate frequency signal is amplified by the intermediate frequency amplifier 317 into a signal of a desired level. The amplified intermediate frequency signal is sent to a SAW BPF (SURFACE ACOUSTIC WAVE BPF 319) which is a filter for restoring and channelizing the original signal. The SAW BPF 319 is mainly made of crystal, lithium niobate, or lithium tantalate, and is designed using surface acoustic wave characteristics of the materials, so that the adjacent band elimination characteristic of the filter is very good.

Meanwhile, the transmitter 330 filters the input intermediate frequency signal by the SAW BPF 339 and amplifies the intermediate frequency signal to a signal of a desired level by the intermediate frequency amplifier 337. The frequency mixer 335 converts the amplified intermediate frequency signal and the signal generated by the local oscillator 320 into a signal of a radio frequency band through multiplication in the time domain and convolution in the frequency domain. The radio frequency signal is sent to the variable band pass filter 333. Here, the center frequency of the pass band of the variable band pass filter 333 is changed by the control signal of the control signal generator in the controller 332. Therefore, the pass frequency band determined according to the center frequency is also varied by the center frequency. The high power amplifier 131 power amplifies the filtered signal and transmits the signal through an antenna.

The variable band pass filters 313 and 333 mentioned above will be described in more detail.

FIG. 4 is a state diagram showing the configuration (a) and equivalent circuit (b) of the variable band pass filters 313 and 333 shown in FIG.

Referring to FIG. 4, (a) illustrates a variable band pass filter configured by connecting a plurality of dielectric resonators and a variable capacitor diode 420 whose capacitance is changed by an electrical voltage signal. (b) shows an equivalent circuit of the variable capacitance diode 420 constituting the variable band pass filter and the plurality of dielectric resonators. The plurality of dielectric resonators includes a plurality of coils and a plurality of capacitors.

The variable band pass filter configured as described above refers to a filter for varying a frequency band determined according to a center frequency by using a property varying according to a capacitance value of the variable capacitance diode 420. The variable center frequency by the value of the capacitance is adjusted by the control signal from the control signal generator. That is, the value of the capacitance of the variable capacitance diode 420 of the variable band pass filter is adjusted by the center voltage by the frequency voltage control signal from the control signal generator, so that the variable band pass filter is dependent on the center frequency. The frequency band can be varied to multiple frequency bands.

5 is a simplified equivalent circuit diagram of the variable capacitance diode 420 mentioned in FIG.

Referring to FIG. 5, a variable capacitance diode is a diode in which the thickness of the depletion layer changes depending on the magnitude of the voltage when a reverse voltage is applied to the diode to change the capacitance of the capacitor (Cv). . The variable capacitance diode is also referred to as a varactor or a varicap, and is widely used in an automatic frequency control circuit (AFC) or a frequency modulation circuit (Frequency Modulation (FM)).

6 illustrates a connection configuration of a control unit for controlling a variable band pass filter according to the present invention.

Referring to FIG. 6, the control unit 640 includes a control signal generator 600 and a digital to analog converter (DAC) 620. When a predetermined bit of digital control signal is generated by the electric voltage applied from the control signal generator 600, the digital control signal is converted into an analog control signal through the digital-to-analog converter 620. The analog control signal adjusts the center frequency of the variable band pass filter 660.

That is, the control signal is provided to the variable capacitor diode. As described above, in the variable capacitance diode, the thickness of the depletion layer is changed according to the voltage level of the control signal, thereby adjusting capacitance Cv (capacitor capacitance). Since the capacitance value determines the center frequency of the variable band pass filter, the center frequency of the variable band pass filter is adjusted according to the control signal, and the pass frequency band determined according to the center frequency is variable. As such, the control signal adjusts a pass frequency band of the variable band pass filter.

7 is a graph showing a change in the center frequency of the transceiver supporting multiple frequency bands according to the present invention.

Referring to FIG. 7, the center frequency of the variable band pass filter is changed according to the voltage of the control signal. That is, the receiving frequency band of the receiving end is not fixed to a specific center frequency but is changed to fr1, fr2, and fr3, and the transmitting end can be configured in multiple frequency bands according to the change of the center frequency. In addition, the center frequency of the transmission band of the transmitter is also changed to ft1, ft2, ft3, it is possible to configure the receiver in the multi-frequency band according to the change of the center frequency.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention implements a variable band pass filter using a variable capacitance diode in a transceiver. That is, by varying the center frequencies of different frequency bands according to electrical voltages, there is an effect of supporting various service bands without replacing a transceiver in a mobile communication system.

Claims (4)

In the transceiver of a mobile communication system, A control unit for generating a control signal for adjusting the center frequency according to the service frequency band; And a variable band pass filter configured to filter an input signal by determining a center frequency according to a control signal received from the controller. The method of claim 1, wherein the control unit, A control signal generator for generating a digital control signal, And a digital analog converter converting the digital control signal into an analog control signal and providing the digital control signal to the variable pass band filter. The method of claim 1, wherein the variable band pass filter, And a variable capacitance diode configured to adjust a capacitance value according to the control signal to determine the center frequency. The method of claim 1, A local generator for generating a local oscillation signal, A frequency mixer for converting an output signal of the variable band pass filter into an intermediate frequency signal using a local oscillation signal generated by the local generator; An intermediate frequency amplifier for amplifying the intermediate frequency signal; And a SAW band pass filter for filtering the amplified intermediate frequency signal in an intermediate frequency band.