JP2001119316A - Direct conversion receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a DC offset and to improve the dynamic range and the reception sensitivity of a receiver. SOLUTION: A signal whose frequency is similar to a reception signal is inputted from a local oscillator 21 o a phase shifter 22. Two output signals which are mutually orthogonal are outputted. The output signals are multiplied by the reception signals in mixers 23 and 25 respectively, orthogonal detection is executed and signals I and Q are generated. The reception signals and signals obtained by controlling the size and the phase of the output signal of the local oscillator 21 through variable amplifiers 31 and 34 and phase adjusters 32 and 35 are mixed through mixers 33 and 36 and they are inputted to the mixers. An adjusting means adjusting DC offset values generated in the signals I and Q is installed. The amplification degree of the variable amplifier and the phase value of the phase adjusting unit, which make the DC offset value to be minimum, are obtained with respect to the reception signal of a frequency that is previously desired. The values are set as the amplification degree of the variable amplifier and the phase value of the phase adjusting unit from an antenna 11 through the adjusting means at the time of receiving the signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct conversion receiver used for mobile radio communication and the like, and more particularly to a direct conversion receiver capable of removing a signal generated from the receiver and mixed into a desired received signal and enabling self-diagnosis. It is.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a configuration example of a conventional intermediate frequency conversion type receiver having a self-diagnosis function. As shown in the figure, a conventional intermediate frequency conversion type receiver having a self-diagnosis function includes an antenna 11, a filter 12, a low-noise amplifier 1
3, mixer 14, filter 15, variable amplifier 16, first
Local oscillator 17, signal distributor 20, oscillator 21, phase shifter 22, mixer 23, filter 24, mixer 25, filter 26, A / D converter 27, signal processor 28, changeover switch 40, transmission power amplifier 41, Mixer 42, modulator 4
3, changeover switch 44, frequency multiplier 45, oscillator 4
6, a configuration including a control unit 50 and the like.

The received signal input from the antenna 11 is
Unnecessary signals are removed by the filter 12 through the changeover switch 40, amplified by the low noise amplifier 13, and then multiplied by the mixer 14 with the output signal of the first local oscillator 17 supplied through the changeover switch 44. It is converted to an intermediate frequency signal. An unnecessary signal is removed from the converted intermediate frequency signal by the filter 15, amplified by the variable amplifier 16, and input to the signal distributor 20.

The output signal of the oscillator 21 is input to a phase shifter 22, and is output from the phase shifter 22 as two output signals orthogonal to each other (signals whose phases are shifted by 90 °). One output signal output from the signal distributor 20 is a phase shifter 22
Is multiplied by the mixer 23 to generate an I signal,
Unnecessary frequencies are removed by the filter 24 and input to the A / D converter 27. Similarly, the other output signal output from the signal distributor 20 is mixed with the other signal of the phase shifter 22 by a mixer 25 to generate a Q signal, an unnecessary frequency is removed by a filter 26, and A / The data is input to the D conversion unit 27.
The I signal and the Q signal are A / D converted by the A / D converter 27 and demodulated by the signal processor 28 by digital signal processing according to the respective communication systems.

At the time of self-diagnosis, the own transmission output signal output from the modulator 43 is frequency-converted by the mixer 42, and the signal amplified by the transmission power amplifier 41 is returned to the receiving circuit via the changeover switch 40, so that the signal can be received normally. Make a self-diagnosis as to whether you can. In this case, since the transmission frequency is different from the reception frequency, an oscillator 46 and a frequency multiplier 45 are required to obtain a predetermined intermediate frequency signal. The control unit 50 is connected to each control device such as each changeover switch and each variable amplifier, and switches each changeover switch to a receiving circuit at the time of reception, and controls the amplification degree of each variable amplifier according to the level of a received signal. ing.

In order to reduce the circuit scale of a receiver for digital mobile communication or the like, quadrature detection is performed using the same local oscillation frequency as the reception frequency, and the reception signal is directly converted to a baseband signal. A direct conversion receiver is used. However, in the direct conversion method, since the frequency of the local oscillation signal is the same as the reception frequency, the local oscillation signal may be mixed with the desired signal. In addition, a DC offset occurs in the I signal and the Q signal due to a DC offset of a mixer and an amplifier constituting a quadrature detector, and the DC offset reduces a dynamic range and deteriorates a receiving sensitivity of a receiver. there were.

A direct conversion receiver disclosed in Japanese Patent Application Laid-Open No. Hei 10-22860 is known as a receiver that eliminates such a problem. FIG. 5 is a diagram showing a configuration example of the direct conversion receiver disclosed in the above-mentioned document. As shown in the figure, this direct conversion receiver is obtained by removing the intermediate frequency circuit from the receiving circuit. In order to prevent the above-mentioned DC offset from occurring, the frequency shifted from the frequency f _{0 of the} received signal is set to the (local) oscillator 2.
1 and the phase shifter 22, the mixer 23 and the mixer 25
Performs quadrature detection. At this time, the component of the adjacent wave that has fallen into the desired signal band is included in the digital signal, but the A / D conversion unit 27 and the signal processing unit 28 remove the component to prevent reception interference.

[0008]

However, the above-described conventional intermediate frequency conversion type receiver requires an intermediate frequency signal circuit, so that the circuit scale becomes large and is not suitable for portable use. Further, in a communication device having only a receiving unit without a transmitting unit, self-diagnosis cannot be performed by the method shown in FIG.

In the direct conversion receiver disclosed in Japanese Patent Application Laid-Open No. 10-22860, no DC offset is generated, but the means and adjustment for removing adjacent wave components falling into a desired signal band are complicated. Further, the adjacent wave may vary depending on the use environment and the situation, and it is difficult to always completely remove the adjacent wave. Further, since the frequency of the oscillator 21 is shifted from the frequency f _{0 of the} received signal, there is a problem that the oscillator 21 cannot be used as an input signal for self-diagnosis.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a direct conversion receiver which has improved the dynamic range and reception sensitivity of a receiver by eliminating the above problems and preventing the occurrence of a DC offset. The purpose is to provide.

[0011]

According to a first aspect of the present invention, there is provided a local oscillator, a phase shifter, and a mixer, wherein a signal having the same frequency as a received signal is transmitted from the local oscillator to a phase shifter. A direct conversion receiver that outputs two output signals that are orthogonal to each other, multiplies each output signal by a mixer with a received signal, performs quadrature detection, and generates an I signal and a Q signal. , And an output signal of a local oscillator are mixed via a variable amplifier and a phase adjuster with a signal whose magnitude and phase are controlled via a mixer, respectively, and input terminals of respective mixers for generating an I signal and a Q signal. Input means, an adjusting means for adjusting a DC offset value generated in the I signal and the Q signal output from each mixer is provided. The amplification degree of the variable amplifier and the phase value of the phase adjuster that minimize the set value are obtained in advance, and the amplification degree of the variable amplifier and the phase value of the phase adjuster are obtained through the adjustment means when receiving a signal from the antenna. It is characterized in that it is set to a value.

The invention described in claim 2 is the first invention.
In the direct conversion receiver described in the above, by providing a changeover switch for switching between the signal received from the antenna and the signal distributed from the local oscillator, by receiving the signal distributed from the local oscillator, the receiving circuit A self-diagnosis function for performing a self-diagnosis is provided.

According to a third aspect of the present invention, there is provided a local oscillator, a phase shifter, and a mixer, wherein a signal having the same frequency as a received signal is input from the local oscillator to the phase shifter, and two signals orthogonal to each other are provided. In a direct conversion receiver that outputs an output signal, multiplies each of the output signals by a received signal and a mixer to perform quadrature detection, and generates an I signal and a Q signal, the received signal from the antenna and the local oscillator are distributed. And a self-diagnosis function of performing self-diagnosis of the receiving circuit by receiving a signal distributed from the local oscillator.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiments of the present invention will be described below in detail with reference to the drawings. FIG.
FIG. 1 is a diagram illustrating a configuration example of a direct conversion receiver according to the present invention. As shown in the figure, the direct conversion receiver includes a variable amplifier 3 connected to an input terminal of a mixer 23 of a quadrature detection circuit of a conventional direct conversion receiver.
1, the phase adjuster 32 and the mixer 33 are connected, and the mixer 25
Amplifier 34, phase adjuster 35, mixer 3
6 to remove the DC offset generated in each of the mixers 23 and 25. In the same figure, the portions denoted by the same reference numerals as those of the conventional example have the same functions as those of the conventional example.

One output signal output from the signal distributor 20 is supplied from an oscillator 21 to a variable amplifier 31 and a phase adjuster 3.
2 is mixed with a signal output from the phase shifter 22 by a mixer 33, and further multiplied by one signal of a phase shifter
A signal is generated, an unnecessary frequency is removed by the filter 24, and the signal is input to the A / D converter 27. Similarly, the other output signal output from the signal distributor 20 is mixed with the signal output from the oscillator 21 via the variable amplifier 34 and the phase adjuster 35 by the mixer 36, and further mixed by the mixer 25. The signal is multiplied by one of the signals from the converter 22 to generate a Q signal, and unnecessary frequencies are removed by a filter 26, and an A / D converter 27
Is input to The I signal and the Q signal are A / D converted by the A / D converter 27 and demodulated by the signal processor 28 by digital signal processing according to the respective communication systems.

Next, a method of adjusting the variable amplifier 31, the phase adjuster 32, the variable amplifier 34, and the phase adjuster 35 will be described. First, in a state where no reception signal is input to the antenna 11, the oscillator 21 is operated at a predetermined frequency,
3 is adjusted so that the absolute value of the output signal of the variable amplifier 3 becomes slightly larger than the absolute value (known value) of the DC offset, and then the phase adjuster 32 is changed by 2π radians or more, and the mixer 23 Is set to minimize the absolute value of the output signal of Next, the amplification degree of the variable amplifier 31 is set so that the output signal of the mixer 23 is minimized. The variable amplifier 34 and the phase adjuster 35 are set similarly.

At this time, the control unit 50 stores the adjusted set values of the variable amplifier 31, the phase adjuster 32, the variable amplifier 34, and the phase adjuster 35, and performs each variable amplifier before performing a normal reception operation. The control is performed so that the amplification degree of 31, 31 and the phase of each phase adjuster 32, 35 are set to the stored set values. Therefore, the antenna 11 can be used in a normal receiving operation.
When a desired reception signal is input, the amplification degree of each of the variable amplifiers 31 and 34 and the phase of each of the phase adjusters 32 and 35 are set to predetermined values, and the DC offset generated at the output of the mixer 23 is the minimum value. To be reduced.

As described above, the first embodiment of the present invention
According to this, a variable amplifier 31, a phase adjuster 32, a variable amplifier 34, and a phase adjuster 35 are provided to adjust the magnitude and phase of the output signal of the oscillator 21 so that the DC offset value of the signal of a predetermined frequency is minimized in advance. , And the set values are stored, and the gain and the phase adjusters 32 and 35 of the variable amplifiers 31 and 34 are stored during the reception operation.
Is set to the stored set value, the DC offset is minimized, and the dynamic range and the receiving sensitivity can be improved. Further, this adjustment does not require a measuring device other than the receiver, and can be adjusted when communication is not being performed. Therefore, it is easy to always adjust the DC offset value of the receiver to the minimum state.

[Embodiment 2] FIG. 2 is a diagram showing an example of the configuration of a direct conversion receiver according to the present invention. As shown, the direct conversion receiver of the present invention is provided with a changeover switch 40 in the antenna circuit,
The self-diagnosis is enabled by taking out the output signal of No. 1 through the distributor 37 and inputting it to the receiving circuit through the changeover switch 40. In this figure, the portions denoted by the same reference numerals as those in FIG. 1 have the same functions as those in FIG.

As described above, in the direct conversion receiver having the self-diagnosis function, the oscillator 21
Since the frequency of the output signal is the same as the frequency of the received signal,
By inputting the output signal of the oscillator 21 via the changeover switch 40, self-diagnosis can be easily performed.

[Embodiment 3] FIG. 3 is a diagram showing a configuration example of a direct conversion receiver according to the present invention. This direct conversion receiver, as shown in the figure,
In the conventional direct conversion receiver shown in FIG. 5, a switch 40 is provided at the output of the antenna 11,
The self-diagnosis is enabled by inputting the output signal of the oscillator 21 to the receiving circuit via the changeover switch 40.

As described above, by inputting the output signal of the oscillator 21 to the receiving circuit via the changeover switch 40, a self-diagnosis function can be easily provided even if the conventional DC offset prevention function is not provided. (However, in this case, the dynamic range and the reception sensitivity are not improved).

[0023]

As described above, according to the invention described in each claim, the following excellent effects can be expected.

According to the first aspect of the present invention, each of the received signal and the signal whose magnitude and phase are controlled by the output signal of the local oscillator via the variable amplifier and the phase adjuster are mixed via the respective mixers. Then, an adjusting means for adjusting a DC offset value generated in the I signal and the Q signal output from each mixer by providing the input signal to the input terminal of each mixer for generating the I signal and the Q signal is provided. The gain of the variable amplifier and the phase value of the phase adjuster for minimizing the DC offset value with respect to the received signal are obtained in advance, and the gain of the variable amplifier and the phase adjuster of the variable amplifier are adjusted via the adjusting means when receiving a signal from the antenna. Since the phase value is set to the obtained value, the DC offset during reception is minimized, and the dynamic range and the reception sensitivity can be improved. Also,
This adjustment does not require a measuring device other than the receiver, and can be adjusted when communication is not being performed. It is easy to always adjust the DC offset value of the receiver to the minimum state.

According to the second aspect of the present invention, a changeover switch for switching between a signal received from an antenna and a signal distributed from a local oscillator is provided, and a signal distributed from the local oscillator is received. Accordingly, since the self-diagnosis function for performing self-diagnosis of the receiving circuit is provided, the self-diagnosis of the receiving circuit can be easily performed by switching the changeover switch in addition to the effect of the first aspect of the present invention.

According to the third aspect of the present invention, there is provided a local oscillator, a phase shifter, and a mixer. A signal having the same frequency as a received signal is input from the local oscillator to the phase shifter, and is orthogonal to each other. Outputting two output signals, multiplying each of the output signals by a received signal and a mixer to perform quadrature detection,
A direct conversion receiver that generates an I signal and a Q signal is provided with a switch for switching between a signal received from an antenna and a signal distributed from a local oscillator, and receives a signal distributed from the local oscillator. Since the self-diagnosis function for performing self-diagnosis of the receiving circuit is provided, the receiving circuit can be easily self-diagnosed by switching the changeover switch.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a direct conversion receiver according to the present invention.

FIG. 2 is a diagram illustrating a configuration example of a direct conversion receiver according to the present invention.

FIG. 3 is a diagram illustrating a configuration example of a direct conversion receiver according to the present invention.

FIG. 4 is a diagram showing a configuration example of a conventional intermediate frequency conversion type receiver having a self-diagnosis function.

FIG. 5 is a diagram illustrating a configuration example of a conventional direct conversion receiver.

[Explanation of symbols]

 Reference Signs List 11 antenna 12 filter 13 low noise amplifier 14 mixer 15 filter 16 variable amplifier 17 first local oscillator 20 signal distributor 21 oscillator 22 phase shifter 23 mixer 24 filter 25 mixer 26 filter 27 A / D conversion unit 28 signal processing unit 31 variable Amplifier 32 Phase adjuster 33 Mixer 34 Variable amplifier 35 Phase adjuster 36 Mixer 37 Distributor 40 Changeover switch 41 Transmission power amplifier 42 Mixer 43 Modulator 44 Changeover switch 45 Frequency multiplier 46 Oscillator 50 Control unit

Claims (3)

[Claims] A local oscillator, a phase shifter, and a mixer;
A signal having the same frequency as the received signal is input from the local oscillator to the phase shifter, and two output signals orthogonal to each other are output. Each of the output signals is multiplied by the received signal and the mixer to perform quadrature detection. , A direct conversion receiver for generating an I signal and a Q signal, wherein each of the received signal and a signal obtained by controlling the magnitude and phase of the output signal of the local oscillator via a variable amplifier and a phase adjuster are mixed. And the above I
Signal and a Q signal are input to input terminals of the respective mixers, thereby providing an adjusting means for adjusting a DC offset value generated in an I signal and a Q signal which are outputs of the respective mixers. The gain of the variable amplifier and the phase value of the phase adjuster for minimizing the DC offset value are determined in advance, and the gain and the phase adjuster of the variable amplifier are received via the adjusting means when a signal is received from an antenna. A direct conversion receiver characterized in that the phase value of is set to the determined value. 2. The direct conversion receiver according to claim 1, further comprising a changeover switch for switching between a signal received from the antenna and a signal distributed from the local oscillator,
A direct conversion receiver having a self-diagnosis function of performing self-diagnosis of a receiving circuit by receiving a signal distributed from the local oscillator. 3. It has a local oscillator, a phase shifter and a mixer,
A signal having the same frequency as the received signal is input from the local oscillator to the phase shifter, and two output signals orthogonal to each other are output. Each of the output signals is multiplied by the received signal and the mixer to perform quadrature detection. A direct conversion receiver for generating an I signal and a Q signal, wherein a switch for switching between a signal received from the antenna and a signal distributed from the local oscillator is provided;
A direct conversion receiver comprising a self-diagnosis function of performing self-diagnosis of a receiving circuit by receiving a signal distributed from the local oscillator.