KR20010091693A - Direct conversion receiver minimizing local oscillator leakage and method thereof - Google Patents

Abstract

PURPOSE: A direct conversion receiver for minimizing a local oscillator leakage and a method for processing signals thereby are provided to remove a leakage state of a local oscillator. CONSTITUTION: An antenna(12) receives a radio signal transmitted from a transmitter and emitted in the air. A BPF(Band Pass Filter)(15) executes band pass filtering for the signal received through the antenna(12). An LNA(Low Noise Amplifier)(16) amplifies the filtered signal at a low noise. The BPF(15) and the LNA(16) are operated as a radio frequency signal processing part that processes the signal received through the antenna(12) at an RF(Radio Frequency) band and outputs an RF receive signal having the first frequency. The output of the LNA(16) is supplied to both the first frequency converter(11) and the second frequency converter(11'). A PLL(Phase-Locked Loop)(20), containing a local oscillator generating an oscillation signal having the second frequency, generates a phase-locked signal having the first frequency. A phase shifter(19) shifts the phase-locked signal and outputs the phase-locked signal and a phase-shifted signal. The phase-locked signal is supplied to the first frequency converter(11), and the phase-shifted signal to the second frequency converter(11').

Description

Direct conversion receiver and signal processing method to minimize leakage of local oscillator {DIRECT CONVERSION RECEIVER MINIMIZING LOCAL OSCILLATOR LEAKAGE AND METHOD THEREOF}

The present invention relates to a receiver for use in a wireless communication terminal, and more particularly, to a receiver based on a direct conversion principle such as a homodyne receiver and a signal processing method thereof.

Receivers used in wireless communication terminals such as cellular phones and wireless telephones, such as cellular phones, personal communication services (PCS) phones, are typically heterodyne type receivers. However, a heterodyne receiver may include a frequency converter for converting a radio frequency into an intermediate frequency signal, a frequency converter for converting an intermediate frequency into a baseband signal, and a signal of each frequency band. Because bandpass filters are required for processing, they are not suitable for wireless communication terminals, especially mobile phones, which are gradually being miniaturized. In addition, such a heterodyne receiver has a disadvantage in that the production cost is high because of the large number of required parts. In addition, mobile telephones are evolving to provide not only voice calls but also multimedia services. In order to meet these trends, miniaturization of components and simplification of circuits need to be preceded.

In order to solve the shortcomings of the heterodyne receiver, many researches have been made on the wireless communication terminal, and the receivers based on the results of the research are based on the direct conversion principle. A representative example of a receiver based on the direct conversion principle (hereinafter referred to as a "direct conversion receiver") is a homodyne receiver. The direct conversion receiver is a receiver that causes the local oscillator to operate at the same frequency as the high frequency signal received through the antenna, and converts the high frequency signal into a baseband signal without converting the high frequency signal into an intermediate frequency signal. In other words, the direct conversion receiver is suitable for mobile phones that are miniaturized and simplified because they do not include components for processing intermediate frequency signals.

On the other hand, a problem in the direct conversion receiver is spurious emission. The main cause of spurious radiation is local oscillator leakage. The leakage of the local oscillator means a phenomenon in which a signal oscillated by the local oscillator affects a desired signal, as is well known to those skilled in the art. Specifically, the signal received through the antenna must be frequency converted as a desired baseband signal by a frequency mixer, but at this time the baseband signal is affected by an oscillation signal by a local oscillator applied to the frequency mixer. This can be a signal in the non-band region, which is called leakage of a local oscillator. In fact, a typical super heterodyne receiver comprising components that first convert a high frequency signal into an intermediate frequency signal and secondly convert the intermediate frequency signal into a baseband signal performs a filtering operation over two orders of magnitude. Since the leakage phenomenon of the local oscillator as described above is eliminated.

However, in the direct conversion receiver, since the local oscillation frequency is in the passband of the bandpass filter, there has been a need to solve the problem of leakage of the local oscillator. One solution to this problem is disclosed in detail under US Patent No. 5,530,929, entitled "HOMODYNE RECEIVER MINIMIZING OSCILLATOR LEAKAGE", filed June 25, 1996. The homodyne receiver according to the prior art disclosed in the above-mentioned US patent is configured as shown in FIG.

Referring to FIG. 1, a homodyne receiver according to the related art includes a first processor 13 multiplying a signal oscillated by a local oscillator (LO) by M times and a signal processed by the first processor 13 by N times. And a second processing unit 14 for dispensing. That is, in order to eliminate the leakage of the local oscillator, the homodyne receiver according to the prior art additionally inserts a first processor 13 as a multiplier and a second processor 14 as a divider between a phase shifter 19 and a local oscillator. have. There is also a further need for signals to control the multiplier and divider. These components are provided separately from the phase locked loop (PLL) 20 included in all receivers.

FIG. 2 is a diagram illustrating a configuration of a direct conversion receiver to which the principle shown in FIG. 1 is applied. As shown in the drawing, a multiplier 13 for multiplying the signal oscillated by the local oscillator and a divider 14 for dividing the signal multiplied by the multiplier 13 are provided between the local oscillator and the frequency converter 11. An additional signal processor 10 is included. There is also a further need for signals to control the multiplier and divider. These components are provided separately from the PLL 20 included in all receivers.

As shown in FIG. 1 and FIG. 2, the prior art adopts a method of eliminating the leakage phenomenon of the local oscillator by additionally inserting components such as a multiplier and a divider. However, the addition of these components increases the number of components required for the wireless communication terminal, which increases the manufacturing cost and also has the disadvantage of increasing the hardware size of the wireless communication terminal. Accordingly, the conventional method of eliminating the leakage phenomenon of the local oscillator may not be suitable for a wireless communication terminal which is gradually miniaturized as described above. In other words, a solution for eliminating the local oscillator leakage caused by the wireless communication terminal used in the direct conversion principle and at the same time minimizing the trend is required.

Accordingly, an object of the present invention is to provide a direct conversion receiver and a signal processing method therefor that eliminate the leakage phenomenon of the local oscillator.

Another object of the present invention is to provide a direct conversion receiver and a signal processing method therefor for miniaturizing a wireless communication terminal.

It is still another object of the present invention to provide a homodyne receiver and a signal processing method thereof, which reduce the number of components required for the wireless communication terminal and manufacturing cost, and eliminate leakage of the local oscillator.

According to a first aspect of the present invention for achieving these objects, a high frequency signal processor for outputting a high frequency signal having a first frequency (f _RF ) by processing a signal received through the antenna in a high frequency band; The direct conversion receiver includes a phase locked loop and a frequency converter. The phase-locked loop includes a local oscillator for generating an oscillation signal having a second frequency f _LO , and phase-synchronizes the oscillation signal to generate a phase-locked signal having the first frequency in the same manner as the high-frequency received signal. do. The frequency converter converts the high frequency reception signal according to the phase synchronization signal and outputs the signal for baseband processing.

According to a second aspect of the present invention, a homodyne receiver including a high frequency signal processor for processing a signal received through an antenna in a high frequency band and outputting a high frequency received signal having a first frequency f _RF . And a phase shifter and first and second frequency converters. The phase-locked loop includes a local oscillator for generating an oscillation signal having a second frequency f _LO , and phase-synchronizes the oscillation signal to generate a phase-locked signal having the first frequency in the same manner as the high-frequency received signal. do. The phase shifter shifts the phase synchronization signal by a predetermined phase and outputs a synchronization signal phase shifted with the phase synchronization signal. The first frequency converter converts the high frequency reception signal according to the phase synchronization signal and outputs the first signal for baseband processing. The second frequency converter converts the high frequency reception signal according to the phase shifted synchronization signal and outputs the second signal for baseband processing.

1 is a view showing the configuration of a homodyne receiver according to the prior art.

2 is a view showing the configuration of a direct conversion receiver according to the prior art.

3 is a diagram showing the configuration of a direct conversion receiver according to the present invention;

4 is a view showing the configuration of a homodyne receiver according to the present invention.

FIG. 5 is a diagram illustrating a configuration of an embodiment of a phase locked loop (PLL) shown in FIGS. 3 and 4.

6 is a diagram illustrating a configuration according to another embodiment of the PLL shown in FIGS. 3 and 4.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that reference numerals and like elements among the drawings are denoted by the same reference numerals and symbols as much as possible even though they are shown in different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

3 is a view showing the configuration of a direct conversion receiver according to the present invention, an antenna 12, a band pass filter (BPF) 15, a low noise amplifier (LNA) 16, a phase locked loop (PLL) Locked Loop) 20, Frequency Mixer 11, Low Pass Filter (LPF) 17 and Amplifier (AMP) 18.

Referring to FIG. 3, the antenna 12 receives a radio signal transmitted from a transmitter (not shown) and radiated in the air. The bandpass filter 15 bandpass filters the signal received through the antenna 12. The low noise amplifier 16 is to improve the sensitivity of the receiver, and low noise amplifies the bandpass filtered signal by the bandpass filter 15. The band pass filter 15 and the low noise amplifier 16 operate as a high frequency signal processor for processing a signal received through the antenna 12 in a high frequency band and outputting a radio frequency (RF) received signal having a first frequency (f _RF ). do.

The phase synchronization loop 20 includes a local oscillator for generating an oscillation signal having a second frequency f _LO therein, and phase-synchronizes the oscillation signal to have the first frequency equal to the high frequency received signal. Generate a signal. The configuration and operation of this phase locked loop 20 will be described with reference to FIGS. 5 and 6 to be described later.

The frequency converter 11 converts the high frequency reception signal according to the phase synchronization signal and outputs the signal for baseband processing. At this time, since the output signal of the low noise amplifier 16, which is one input signal of the frequency converter 11, and the output signal of the phase synchronization loop 20, which are the other input signals, are frequency signals of the same band, leakage of the local oscillator is eliminated. The low pass filter 17 low pass filters the output of the frequency converter 11. Amplifier 18 amplifies the output of lowpass filter 17 and outputs it as a baseband signal for subsequent demodulation operation.

Such a direct conversion receiver according to the present invention does not require a multiplier and a divider provided separately from the phase synchronization loop, unlike the direct conversion receiver according to the prior art illustrated in FIG. 2, and only the phase synchronization loop 20 is a frequency converter 11. It can be seen that it is connected to one input terminal of. The phase-locked loop 20 is basically a required component when configuring the radio transmitter and the receiver as described above. Therefore, since the direct conversion receiver according to the present invention does not require a multiplier and a divider separately, an increase in the number of parts can be prevented and the hardware size can be reduced.

4 is a diagram illustrating a configuration of a homodyne receiver according to the present invention. An antenna 12, a band pass filter (BPF) 15, a low noise amplifier (LNA) 16, a phase locked loop (PLL) 20, a phase shifter 19 Frequency mixers 11, 11 ', low pass filters (LPFs) 17, 17' and amplifiers (AMP) 18, 18 '.

Referring to FIG. 4, the antenna 12 receives a radio signal transmitted from a transmitter (not shown) and radiated in the air. The bandpass filter 15 bandpass filters the signal received through the antenna 12. The low noise amplifier 16 is to improve the sensitivity of the receiver, and low noise amplifies the bandpass filtered signal by the bandpass filter 15. The band pass filter 15 and the low noise amplifier 16 operate as a high frequency signal processor for processing a signal received through the antenna 12 in a high frequency band and outputting a radio frequency (RF) received signal having a first frequency (f _RF ). do. The output of the low noise amplifier 16 is applied to frequency converter 11 and also to frequency converter 11 '.

The phase synchronization loop 20 includes a local oscillator for generating an oscillation signal having a second frequency f _LO therein, and phase-synchronizes the oscillation signal to have the first frequency equal to the high frequency received signal. Generate a signal. The configuration and operation of this phase locked loop 20 will be described with reference to FIGS. 5 and 6 to be described later.

The phase shifter 19 shifts the phase synchronization signal by a predetermined amount (0 ° and 90 °), respectively, and outputs the phase synchronization signal (0 ° shifted signal) and the phase shifted signal (90 ° shifted signal). The phase locked signal is applied to a first frequency converter 11 and the phase shifted signal is applied to a second frequency converter 11 '.

The first frequency converter 11 converts the high frequency reception signal according to the phase synchronization signal and outputs the first signal (I channel signal) for baseband processing. At this time, since the output signal of the low noise amplifier 16, which is one input signal of the frequency converter 11, and the phase synchronization signal from the phase shifter 19, which is another input signal, are frequency signals of the same band, the leakage phenomenon of the local oscillator is eliminated. The low pass filter 17 low pass filters the output of the first frequency converter 11. Amplifier 18 amplifies the output of lowpass filter 17 and outputs it as a first baseband signal for subsequent demodulation operation.

The second frequency converter 11 'converts the high frequency received signal according to the phase shifted signal and outputs it as a second signal (Q channel signal) for baseband processing. In this case, since the output signal of the low noise amplifier 16, which is one input signal of the second frequency converter 11 ', and the phase shifted signal from the phase shifter 19, which is another input signal, are frequency signals of the same band, leakage of the local oscillator is eliminated. do. The low pass filter 17 'low-pass filters the output of the second frequency converter 11'. Amplifier 18 'amplifies the output of lowpass filter 17' and outputs it as a second baseband signal for subsequent demodulation operation.

Such a direct conversion receiver according to the present invention does not require a multiplier and a divider provided separately from the phase synchronization loop, unlike the homodyne receiver according to the related art shown in FIG. 1, and only the phase synchronization loop 20 is a phase shifter 19. It can be seen that through the input terminals of the frequency converters 11 and 11 ', respectively. As described above, the phase locked loop 20 is basically a required component when configuring the radio transmitter and the receiver. Therefore, since the homodyne receiver according to the present invention does not require a multiplier and a divider separately, an increase in the number of parts can be prevented and hardware size can be reduced.

FIG. 5 is a diagram illustrating a configuration of a phase locked loop (PLL) 20 illustrated in FIGS. 3 and 4. This phase locked loop 20 is a typical type of phase locked loop.

Referring to FIG. 5, a phase detector 21 compares and detects a phase of an oscillation signal generated by a local oscillator LO and a frequency signal prescaled by a prescaler 27 and according to the comparison result. Occurs. The loop filter 23 filters the phase difference signal generated by the phase detector 21 and outputs a DC control voltage. The voltage controlled oscillator (VCO) 25 outputs a signal corresponding to the DC control voltage as a phase locked signal. The pre-scaler 27 prescales the frequency of the phase-synchronized signal output from the voltage controlled oscillator 25 at a preset ratio to provide it to the phase detector 21.

The signal oscillated by the local oscillator is phase-locked by the phase detector 21, the loop filter 23, the voltage controlled oscillator 25 and the prescaler 27, and the phase-synchronized signal is output from the voltage controlled oscillator 25 and 4 is applied to the phase shifter 19 of FIG. At this time, the phase synchronization signal output from the voltage controlled oscillator 25 is a signal for removing the leakage of the local oscillator, which is output from the low noise amplifier 16 of FIGS. 3 and 4 and then applied to the frequency converter 11 and the frequency converters 11 and 11 '. It is a signal having the same frequency as the high frequency reception signal.

FIG. 6 is a diagram illustrating a configuration of another PLL 20 shown in FIGS. 3 and 4.

Referring to FIG. 6, the first frequency divider 22 divides the signal oscillated by the local oscillator LO at a first predetermined ratio. The phase detector 21 detects and compares the phase of the frequency-divided signal at the second ratio preset by the output of the first frequency divider 22 and the second frequency divider 27 and generates a phase difference signal according to the comparison result. The loop filter 23 filters the phase difference signal and outputs a DC control voltage. The voltage controlled oscillator 25 outputs a frequency signal corresponding to the DC control voltage. The frequency multiplier 26 frequency-multiplies the output of the voltage controlled oscillator 25 at a third predetermined ratio and outputs the phase-synchronized signal. The second frequency divider 27 divides the output of the voltage controlled oscillator 25 at the second ratio.

The signal frequency-divided by the first frequency divider 22 after being oscillated by the local oscillator is phase-locked by the phase detector 21, the loop filter 23, the voltage controlled oscillator 25 and the second frequency divider 27, and the voltage controlled oscillator 25 The phase-synchronized signal outputted from is applied to the frequency converter 11 of FIG. 3 and the phase shifter 19 of FIG. At this time, the phase synchronization signal output from the frequency multiplier 26 is a signal for removing the leakage of the local oscillator, and is output from the low noise amplifier 16 of FIGS. 3 and 4 and then applied to the frequency converter 11 and the frequency converters 11 and 11 '. This signal has the same frequency as the received signal.

For example, assuming that the local oscillator oscillates a signal of 10 MHz and the high frequency received signal applied to the frequency converter 11 of FIG. 3 and the frequency converters 11 and 11 'of FIG. 4 is 2 GHz, the first frequency divider 22 is “10. It is designed to have a division ratio of ", the second frequency divider 27 may be designed to have a division ratio of" 50 ", and the frequency multiplier 26 may be designed to have a multiplication ratio of" 2 ". That is, the first frequency divider 22 divides the 10 MHz signal generated by the local oscillator into "10" and outputs a 1 MHz signal. The second frequency divider 27 divides the 50 MHz signal output from the voltage controlled oscillator 25 into "50" in response to the phase difference signal of 1 MHz to output a 1 MHz signal. In this case, the phase detector 21 outputs a phase difference signal of "0", the voltage controlled oscillator 25 outputs a signal of 1 GHz, and the frequency multiplier 26 outputs a signal of 2 GHz. The 2 GHz signal output from the frequency multiplier 26 is a signal having the same frequency as the high frequency received signal applied to the frequency converter 11 of FIG. 3 and the frequency converters 11, 11 ′ of FIG. 4.

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 determined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

As described above, the present invention eliminates the leakage phenomenon of the local oscillator without using a separate multiplier and a divider using only a phase-locked loop basically included in a general wireless transmitter and receiver. The present invention not only eliminates the leakage phenomenon of the local oscillator, but also eliminates the need for a separate multiplier and divider, thereby reducing the number of components required by the receiver, and as a result, it is possible to reduce the size of the wireless communication terminal. have.

Claims (11)

A direct conversion receiver comprising a high frequency signal processing unit for processing a signal received through an antenna in a high frequency band and outputting a high frequency received signal having a first frequency f _RF : A phase oscillation loop including a local oscillator for generating an oscillation signal having a second frequency f _LO , and synchronizing the oscillation signal to generate a phase synchronization signal having the first frequency in the same manner as the high frequency reception signal; ; And a frequency converter converting the high frequency reception signal according to the phase synchronization signal and outputting the signal as a signal for baseband processing. The method of claim 1, wherein the phase locked loop; A phase detector for comparing and detecting a phase of the oscillation signal and a prescaled frequency signal and generating a phase difference signal according to the comparison result; A loop filter for filtering the phase difference signal and outputting a DC control voltage; A voltage controlled oscillator for outputting a signal corresponding to the DC control voltage as the phase synchronization signal; And a prescaler for prescaling the frequency of the phase-locked signal at a preset ratio and providing it to the phase detector. The method of claim 1, wherein the phase locked loop; A first divider for frequency dividing the oscillation signal at a preset first ratio; A phase detector for detecting and comparing the phase of the frequency-divided signal with the output of the first frequency divider at a second predetermined ratio and generating a phase difference signal according to the comparison result; A loop filter for filtering the phase difference signal and outputting a DC control voltage; A voltage controlled oscillator for outputting a frequency signal corresponding to the DC control voltage; A multiplier for frequency multiplying the output of the voltage controlled oscillator at a third predetermined ratio and outputting the phase synchronized signal; And a second divider for frequency dividing the output of the voltage controlled oscillator at the second ratio. The method of claim 1, A low pass filter for low pass filtering the output of the frequency converter; And amplifying an output of the low pass filter and outputting the output signal as a baseband signal. A homodyne receiver comprising a high frequency signal processor for processing a signal received through an antenna in a high frequency band and outputting a high frequency received signal having a first frequency f _RF : A phase oscillation loop including a local oscillator for generating an oscillation signal having a second frequency f _LO , and synchronizing the oscillation signal to generate a phase synchronization signal having the first frequency in the same manner as the high frequency reception signal; ; A phase shifter for shifting the phase synchronization signal by a predetermined phase and outputting a synchronization signal phase shifted with the phase synchronization signal; A first frequency converter converting the high frequency received signal according to the phase synchronization signal and outputting the first high frequency signal as a first signal for baseband processing; And a second frequency converter converting the high frequency received signal according to the phase shifted synchronization signal and outputting the second high frequency signal as a second signal for baseband processing. The method of claim 5, wherein the phase locked loop; A phase detector for comparing and detecting a phase of the oscillation signal and a prescaled frequency signal and generating a phase difference signal according to the comparison result; A loop filter for filtering the phase difference signal and outputting a DC control voltage; A voltage controlled oscillator for outputting a signal corresponding to the DC control voltage as the phase synchronization signal; And a prescaler for prescaling the frequency of the phase-locked signal at a preset ratio and providing it to the phase detector. The method of claim 5, wherein the phase locked loop; A first divider for frequency dividing the oscillation signal at a preset first ratio; A phase detector for detecting and comparing the phase of the frequency-divided signal with the output of the first frequency divider at a second predetermined ratio and generating a phase difference signal according to the comparison result; A loop filter for filtering the phase difference signal and outputting a DC control voltage; A voltage controlled oscillator for outputting a frequency signal corresponding to the DC control voltage; A multiplier for frequency multiplying the output of the voltage controlled oscillator at a third predetermined ratio and outputting the phase synchronized signal; And a second divider for frequency dividing the output of the voltage controlled oscillator at the second ratio. The method of claim 5, First and second low pass filters for low pass filtering the first signal and the second signal, respectively; And a first amplifier and a second amplifier for amplifying the outputs of the low pass filters and outputting the first and second baseband signals as first and second baseband signals, respectively. A high frequency signal processor for processing a signal received through an antenna in a high frequency band and outputting a high frequency received signal having a first frequency f _RF ; A phase oscillation loop having a local oscillator for generating an oscillation signal having a second frequency f _LO , and synchronizing the oscillation signal to generate a phase synchronization signal having the first frequency in the same manner as the high frequency reception signal; In a signal processing method of a direct conversion receiver comprising: (A) converting the high frequency received signal into a signal for baseband processing by frequency converting the received high frequency signal; And (b) outputting a baseband signal by low-pass filtering and amplifying the frequency-converted signal in step (a). A high frequency signal processor for processing a signal received through an antenna in a high frequency band and outputting a high frequency received signal having a first frequency f _RF ; A phase oscillation loop having a local oscillator for generating an oscillation signal having a second frequency f _LO , and synchronizing the oscillation signal to generate a phase synchronization signal having the first frequency in the same manner as the high frequency reception signal; In a signal processing method of a homodyne receiver comprising: (A) shifting the phase synchronization signal by a predetermined phase and outputting a synchronization signal phase shifted with the phase synchronization signal; (B) converting the high frequency received signal according to the phase synchronization signal and outputting the first high frequency signal as a first signal for baseband processing; And converting the high frequency received signal according to the phase shifted synchronization signal and outputting the second high frequency signal as a second signal for baseband processing. The method of claim 8, Low pass filtering each of the first signal and the second signal; And amplifying each of the low pass filtering signals and outputting the first and second baseband signals as a first baseband signal and a second baseband signal.