KR20000014542U - Transceiver with amplitude distortion compensation function of surface acoustic wave filter - Google Patents

Abstract

The present invention is designed to compensate for the amplitude distortion of the surface acoustic wave filter and to compensate the amplitude distortion of the surface acoustic wave filter for more stable transmission and reception by constructing a baseband equalization filter having a pass characteristic opposite to that of the surface acoustic wave filter. In order to provide a transceiver provided with a modulated baseband I, Q signal in the QPSK modulator after extracting only the signal needed through the first surface acoustic wave filter, converts into a radio frequency signal and transmits it, A transceiver for converting a received radio frequency signal into an intermediate frequency, extracting only a necessary signal through a second surface acoustic wave filter, demodulating in a QPSK demodulator, and converting the signal into a baseband signal. The first surface acoustic wave filter so as to have a passage characteristic opposite to that of the first surface acoustic wave filter. First and second baseband equalization filters for passing the I and Q signals in the baseband and at the output end of the demodulator and having a pass characteristic opposite to that of the second surface acoustic wave filter. And third and fourth baseband equalization filters for passing the I and Q signals.

Description

Transceiver with amplitude distortion compensation function of surface acoustic wave filter

The present invention relates to a transceiver having a function of compensating amplitude distortion of a surface acoustic wave filter, and more particularly, to a transceiver having a baseband equalization filter to compensate for amplitude distortion in a passband of a surface acoustic wave filter in a transmission and reception circuit.

Hereinafter, a transmission and reception apparatus according to the prior art will be described with reference to the accompanying drawings.

1 is a block diagram of a transmission and reception apparatus according to the prior art, wherein the transmission circuit 11 inputs and modulates an in-phase signal (I signal), an orthogonal signal (Q signal), and a local oscillation signal (11a). A first amplifier 11b for amplifying the modulated signal, a first surface acoustic wave filter 11c for removing unnecessary signals from the amplified signal, and amplifying an output signal of the first surface acoustic wave filter 11c again; A first frequency mixing section for mixing the second amplifier 11d and the frequency output from the local oscillator (not shown) to frequency convert the output signal of the second amplifier 11d into a radio signal RF. It consists of 11e.

Here, the in-phase signal (I signal) and the quadrature signal (Q signal) input to the QPSK modulator 11a pass through low pass filters 11f and 11g, respectively.

The receiving circuit includes a second frequency mixer 12a for mixing the received radio signal RF and a frequency output from the local oscillator, and a third amplifier for amplifying the output signal of the second frequency mixer 12a. 12b, a second surface acoustic wave filter 12c for removing unnecessary signals from the output signal of the third amplifier 12b, and a fourth amplifier for amplifying the output signal of the second surface acoustic wave filter 12c. 12d, and a QPSK demodulation section 12e for mixing the amplified signal and the local oscillation signal to convert an in-phase signal (I signal) and an orthogonal signal (Q signal).

Here, the in-phase signal (I signal) and quadrature signal (Q signal) output from the QPSK demodulator 12e are output through low pass filters (LPF) 12f and 12g, respectively.

Referring to the operation of the conventional transceiver configured as described above is as follows.

First, the I signal and the Q signal are input to the QPSK modulator 11a through the low pass filters 11f and 11g, respectively. The QPSK modulator 11a inputs the I signal, the Q signal, and the local oscillation signal. Modulate with a frequency signal.

The modulated signal passes through the first surface acoustic wave filter 11c via the first amplifier 11b, thereby eliminating unnecessary signals.

The signal passing through the first surface acoustic wave filter 11c is amplified by the second amplifier 11d, and then mixed with a frequency output from the local oscillator (not shown) by the first frequency mixer 11e to wirelessly. The signal is converted and transmitted through the antenna.

In the receiving circuit 12, the radio signal received through the antenna is mixed with the frequency output from the local oscillator and converted into an intermediate frequency signal, and then through the third amplifier 12b, the second surface acoustic wave filter 12c. Pass through.

Therefore, unnecessary signals are removed by the second surface acoustic wave filter 12c, and amplified by the fourth amplifier 12d again.

The output signal of the fourth amplifier 12d is converted into a baseband signal, an in-phase signal (I signal) and an orthogonal signal (Q signal) by the QPSK demodulator 12e and output through the low pass filters 12f and 12g. do.

As described above, the conventional transmission / reception apparatus converts a baseband signal into an intermediate frequency at the time of transmission, and then converts the signal into a radio signal again. Done.

However, in the conventional transceiver as described above, although amplitude distortion (see FIG. 2) is caused in the pass band of the surface acoustic wave filter which removes unnecessary band signals from signals converted to intermediate frequencies or signals converted to radio frequencies, This amplitude distortion could not be compensated for.

The present invention has been made to solve the above problems of the prior art, and to compensate for the amplitude distortion of the surface acoustic wave filter, a baseband equalization filter having a pass characteristic opposite to the bandpass characteristic of the surface acoustic wave filter It is an object of the present invention to provide a transceiver having an amplitude distortion compensation function of a surface acoustic wave filter capable of more stable transmission and reception.

Transceiver with amplitude distortion compensation function of the surface acoustic wave filter of the present invention for achieving the above object is a signal required through the first surface acoustic wave filter after modulating the baseband I, Q signal in the QPSK modulator Extract only the radio frequency signal by converting it into a radio frequency signal, convert the received radio frequency signal into an intermediate frequency, extract only the necessary signal through the second surface acoustic wave filter, and demodulate it in the QPSK demodulator to obtain a baseband signal. A transceiving device for converting, comprising: first and second basebands configured at an input of said modulator and having a pass characteristic opposite to a pass characteristic of said first surface acoustic wave filter; An equalization filter and an output terminal of the demodulator and having a passage characteristic opposite to that of the second surface acoustic wave filter. It characterized by further comprising a third and fourth baseband equalization filter for passing the I and Q signals in the baseband.

1 is a block diagram of a transceiver having a surface acoustic wave filter according to the prior art

FIG. 2 is a view showing a passage characteristic of the surface acoustic wave filter of FIG.

3 is a block diagram of a transceiver having an amplitude distortion compensation function of a surface acoustic wave filter of the present invention

4 is a diagram showing the passing characteristics of the baseband equalization filter according to the present invention.

5 is a view showing the frequency characteristics after passing the surface acoustic wave filter according to the present invention

6 is a diagram of a receiver baseband signal passing through a baseband equalization filter;

Explanation of symbols for main parts of the drawings

31: transmitting circuit 32: receiving circuit

31a, 31b: first and second baseband equalization filters 31c: QPSK modulator

31d and 31f: first and second amplifiers 31e and 32c: first and second surface acoustic wave filters

31g, 32a: first and second frequency mixing sections 32b, 32d: third and fourth amplifier sections

32e: QPSK demodulator 32f, 32g: 3rd and 4th baseband equalization filter

Hereinafter, a transceiver having an amplitude distortion compensation function of a surface acoustic wave filter according to the present invention will be described with reference to the accompanying drawings.

3 is a block diagram of a transceiver having an amplitude distortion compensation function of a surface acoustic wave filter according to the present invention.

As shown in Fig. 3, the transmission circuit first passes the baseband in-phase signal (I signal) and quadrature-phase signal (Q signal) through opposite characteristics to those of the first surface acoustic wave filter located at the rear end, respectively. A second baseband equalization filter (31a, 31b), an in-phase signal (I signal), a quadrature signal (Q signal), and a local output from the first and second baseband equalization filters (31a, 31b). A QPSK modulator 31c for inputting and modulating a local oscillation signal output from an oscillator (not shown), a first amplifier 31d for amplifying an output signal of the QPSK modulator 31c, and the first A first surface acoustic wave filter 31e for removing an unnecessary band signal from the output signal of the amplifier 31d, a second amplifier 31f for amplifying the output signal of the first surface acoustic wave filter 31e, The output signal of the second amplifier 31f and a local oscillator (not shown). Mixed with the local oscillation signal to consist of a first frequency mixing section (31g) for outputting a radio frequency signal (RF).

The receiving circuit 32 includes a second frequency mixing section 32a for mixing the radio frequency signal RF and the local oscillating signal output from the local oscillator (not shown) to convert it into an intermediate frequency, and the second frequency mixing. A third amplifier 32b for amplifying the output signal of the unit 32a, a second surface acoustic wave filter 32c for removing an unnecessary band signal from the output signal of the third amplifier 32b, and the second amplifier. The fourth amplifier 32d amplifies the output signal of the two surface acoustic wave filters 32c, the output signal of the fourth amplifier 32d and a local oscillation signal output from a local oscillator (not shown). A QPSK demodulator 32e for converting a phase signal (I signal) and a quadrature phase signal (Q) signal, and the same pass characteristic as the second surface acoustic wave filter 32c, and are orthogonal to the in-phase signal (I signal). Third, fourth baseband, etc. for passing a phase signal (Q signal), respectively It consists of a filter (32f, 32g).

According to the configuration of the present invention, before the baseband signal is converted to the intermediate frequency, the baseband equalization filter 31a, 31b having a pass characteristic opposite to that of the first surface acoustic wave filter 31e is passed. On the contrary, immediately after the intermediate frequency signal is converted into the baseband signal, the baseband equalizers 32f and 32g having pass characteristics opposite to those of the second surface acoustic wave filter 32c are passed.

The baseband equalization filter having a pass characteristic opposite to that of the surface acoustic wave filter is configured to compensate for the amplitude distortion generated by passing the surface acoustic wave filter.

Referring to the operation of the transceiver having the amplitude distortion compensation function of the surface acoustic wave filter of the present invention configured as described above are as follows.

FIG. 4 shows the pass characteristics of the baseband equalization filter, and it can be seen that the pass characteristics are opposite to those of the surface acoustic wave filter of FIG. 2. As a result, as shown in FIG. The frequency characteristic after passing through the filter can be obtained.

This will be described in more detail.

First, in the case of the transmission circuit, the baseband in-phase signal (I signal) is inputted to the QPSK modulator 31c through the first baseband equalization filter 31a, and the quadrature signal (Q signal) is also added. 2 is passed through the baseband equalization filter 31b and input to the QPSK modulator 31c.

Accordingly, the QPSK modulator 31c mixes the local oscillation signal output from the local oscillator with the in-phase signal and the quadrature signal to produce an intermediate frequency.

Thereafter, the intermediate frequency signal is amplified by the first amplifier 31d and input to the first surface acoustic wave filter 31e.

The first surface acoustic wave filter 31e removes an unnecessary band signal from an intermediate frequency signal, and then outputs only a necessary signal. In this process, amplitude distortion may occur, but the first surface acoustic wave filter ( As it passes through the first and second baseband equalization filters 31a and 31b having a pass characteristic opposite to that of 31e), it is output in a linear form without distortion of amplitude.

Thereafter, the output signal of the first surface acoustic wave filter 31e whose amplitude distortion is canceled by the first and second baseband equalization filters 31a and 31b is amplified by the second amplifier 31f, and then the first signal is amplified. It is input to the frequency mixing part 31g.

The first frequency mixer 31g mixes the local oscillation signal output from the local oscillator and converts the radio frequency signal RF into an output.

On the other hand, in the case of the reception circuit, the radio frequency signal RF received from the antenna and the local oscillation signal are mixed in the second frequency mixer 32a and converted into an intermediate frequency.

Thereafter, the output signal of the second frequency mixer 32a is amplified by the third amplifier 32b and then input to the second surface acoustic wave filter 32c.

The second surface acoustic wave filter 32c removes an unnecessary band signal and outputs only a necessary signal. In this case, the signal passing through the second surface acoustic wave filter 32c generates amplitude distortion.

Thereafter, the output signal of the second surface acoustic wave filter 32c is amplified by the fourth amplifier 32d, and is then quadrature-phased with the baseband in-phase signal (I signal) by the QPSK demodulator 32e. Is converted to (Q signal).

The in-phase signal (I signal) passes through a third baseband equalization filter 32f having a pass characteristic opposite to that of the second surface acoustic wave filter 32c, and a quadrature signal (Q signal) is also passed. Amplitude distortion generated during the passage of the second surface acoustic wave filter 32c as it passes through the fourth baseband equalization filter 32g having a pass characteristic opposite to that of the second surface acoustic wave filter 32c Removed.

Thus, as shown in Fig. 6, it is possible to obtain a baseband signal without amplitude distortion. 6 illustrates a signal of the baseband of the receiving side passing through the baseband equalization filter.

As described above, the transceiver having the amplitude distortion compensation function of the surface acoustic wave filter of the present invention has the following effects.

More stable transmission by compensating amplitude distortion in advance by constructing an equalizing filter having a pass characteristic opposite to the pass characteristic of the surface acoustic wave filter in the baseband by amplitude distortion generated by passing the surface acoustic wave filter for transmission. You can get a signal.

In the same manner, a stable reception signal can be obtained by compensating for the distortion of amplitude caused by passing the surface acoustic wave filter using the baseband equalization filter.

Claims (2)

After modulating the baseband I and Q signals by the QPSK modulator, only the necessary signals are extracted through the first surface acoustic wave filter, converted into radio frequency signals, and transmitted, and the received radio frequency signals are converted into intermediate frequencies. In the transmitting and receiving device for extracting only the signal needed through the second surface acoustic wave filter, demodulated by the QPSK demodulator and converted into a baseband signal, First and second baseband equalization filters configured to be input to the modulator and have pass characteristics opposite to those of the first surface acoustic wave filter so as to pass the I and Q signals of the baseband; And a third and fourth baseband equalization filters configured to pass through the I and Q signals of the baseband to pass through characteristics opposite to those of the second surface acoustic wave filter. A transceiver having an amplitude distortion compensation function of a surface acoustic wave filter. The method of claim 1, wherein the amplitude distortion by the first surface acoustic wave filter is compensated by the first and second baseband equalization filters, and the amplitude distortion by the second surface acoustic wave filter is the third and fourth basis. A transmitting and receiving device having an amplitude distortion compensation function of a surface acoustic wave filter, characterized by being compensated by a band equalizing filter.