JP2940573B2 - Wireless receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiving apparatus, and more particularly, to a direct low-band conversion type radio receiving apparatus having no intermediate frequency stage.

[0002]

2. Description of the Related Art FIG. 4 (Proceedings of The IRE 1956 Dec.)
The method shown in FIG. 5 (see P.1703) and FIG. 5 (see Japanese Patent Publication No. 64-12128) are known.

The radio receiving apparatus shown in FIG. 4 converts the frequency of an input received signal between a local oscillator 4 and a mixer 5, and further shifts the phase of the local oscillator 4 and the local oscillation output by π / 2. And the mixer 2 perform frequency conversion. The outputs of the mixers 2 and 5 are respectively supplied to low-pass filters 6 and 7 to remove image frequency components, and output signals from the low-pass filter 7 are output. Is frequency-converted by a local oscillator 17 and a mixer 18, and frequency-converted by a local oscillator 17 and a phase shifter 16 and a mixer 15 for transferring the output signal thereof by π / 2.
And the output signal of the mixer 18 are added or subtracted, and the added output or the subtracted output is demodulated by the demodulator 20.

The radio receiving apparatus shown in FIG. 5 converts the frequency of an input received signal by a local oscillator 4 and a mixer 5, and further shifts the phase of the local oscillator 4 and the local oscillation output by π / 2. The frequency conversion output is supplied to low-pass filters 6 and 7, respectively, to remove image frequency components. The output signals from low-pass filters 6 and 7 are sampled. The sample hold is performed by the hold circuits 11 and 23, respectively, and the sample hold output is set to A.
The digital signal is converted by the / D converter 24, the digital converted output is demodulated by digital signal processing in the digital signal processing circuit 13, and then converted to an analog signal to obtain a demodulated output.

[0005]

However, in the case of the above-mentioned conventional radio receiving apparatus, four sets of frequency conversion means are required as shown in FIG. 4, and two sets of frequency conversion means are required as shown in FIG. Means and two A / D conversion means are required, and in any case, there is a problem that a circuit size is large in order to realize a radio receiving apparatus. In the case of digital processing, processing for two channels is required. In addition, there is a problem that high speed processing is required in addition to the above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-frequency direct conversion type radio receiving apparatus that requires a small circuit scale and requires a small amount of processing even when performing digital processing.

[0007]

SUMMARY OF THE INVENTION A radio receiving apparatus according to the present invention comprises a frequency converting means for converting a received signal into a low-frequency signal orthogonal to each other, and an output from each of the frequency converting means. A filter for removing the interference, an operation means for inputting the output from the filter to add or subtract, an A / D converter for inputting the output of the operation means, and an output for the A / D converter. Digital signal processing means for digital demodulation.

[0008] Further, an amplifier for separately inputting the outputs of the filters and outputting the outputs to the arithmetic means, regardless of whether a multiplier for multiplying the output of the filter is provided or an output terminal for independently outputting the output of the filter is provided. May be provided. A calculating means for adding or subtracting the output from the amplifier; a multiplying means for inputting and multiplying the output from the amplifier; and an output of each amplifier, an output of the calculating means, and an output of the multiplying means.
A selector may be provided for selecting and outputting the output of the A / D converter, and the output from the selector may be input to the A / D converter.

The filter may be an AC coupling, a low-pass filter, a band-pass filter, a filter for channel selection, or a digital filter in the digital signal processing means may be a filter for channel selection. .
A D / A converter having a digital demodulated output of the digital signal processing means as an input may be provided.

[0010]

According to the radio receiving apparatus of the present invention, the input received signals are converted into mutually orthogonal low-frequency signals by the frequency conversion means, and the low-frequency signals output from the frequency conversion means are each subjected to image interference by the filter. The output from the filter is removed or added or subtracted by the arithmetic means, the arithmetic output is converted into digital data by the A / D converter, and digitally demodulated by the digital signal processing means.

When a multiplier for multiplying the output of the filter is provided, it is possible to obtain a multiplied output and adjust the orthogonality of the output from the frequency conversion means by adjusting the multiplied output to zero. it can. When the output of the filter is output independently, the filter output is obtained independently,
The level of the low-frequency signal can be adjusted based on the output of the filter.

When an amplifier for amplifying the output of the filter is provided, the output of the filter is amplified, and the level of the low-frequency signal is adjusted by adjusting the gain of the amplifier in accordance with the output of the filter. Can be. When selector means is provided, the level of the low-frequency signal can be adjusted by selecting the output of the amplifier by the selector, and the orthogonality of the output from the frequency conversion means can be adjusted by selecting the output of the multiplication means. Can be.

When the filter is constituted by an AC coupling, a DC component is removed, so that the influence of a DC offset in a preceding stage of the filter can be eliminated. If the filter is a filter for channel selection, the filtering is performed by the filter. If the channel is selected by the digital filter in the digital signal processing unit, the channel is selected by the digital filter in the digital signal processing unit. be able to.

When a D / A converter is provided, the demodulated output by the digital signal processing means can be converted into an analog signal by the D / A converter, and the subsequent processing can be performed in analog.

[0015]

The present invention will be described below with reference to examples. FIG.
FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. The input received signal is amplified by the amplifier 1, and the amplified input received signal is mixed with the output of the local oscillator 4 by the mixer 5 for frequency conversion. Further, the transmission output of the local oscillator 4 is supplied to the phase shifter 3 to be phase-shifted by π / 2, and the phase-shifted local transmission output and the amplified input reception signal are mixed by the mixer 2 to perform frequency conversion. Then, a frequency-converted output having a phase different from the frequency-converted output of the mixer 5 by π / 2 is obtained.

The frequency-converted output signal output from the mixer 5 is supplied to a low-pass filter 7 to remove image frequency components, and the frequency-converted output signal output from the mixer 2 is applied to a low-pass filter 6. To remove the image frequency component. The output signals from the low-pass filters 6 and 7 are respectively supplied to amplifiers 8 and 9 to be separately amplified and level-adjusted.

The output signals from the amplifiers 8 and 9 are added or subtracted by an arithmetic unit 10 comprising an adder or a subtractor, and the arithmetic output is sample-holded by a sample-hold circuit 11, and is sample-holded. A / D converter 1
2 for digital conversion, and the digitally converted data
The data is supplied to a digital signal processing circuit 13 for demodulation, and the demodulated output is supplied to a D / A converter 14 to be converted into an analog signal and output.

The operation of the embodiment constructed as described above will be described with reference to the spectrum of each part shown in FIG. The desired signal to be received is defined as n (carrier frequency fc, bandwidth B), and on the frequency axis above and below, n-2, n-1, ..., n, n +
An input received signal including an interference signal such as 1, n + 2,... Is amplified by the amplifier 1 and then input to the next frequency conversion stage. The spectrum at the input point of the amplifier 1 is as shown in FIG. The frequency conversion stage converts the output of the local oscillator 4 and the output of the amplifier 1 whose phases are shifted by π / 2 from each other into low-frequency signals whose phase is shifted by π / 2 at the center frequency f ₀ .

These low-frequency signals are represented by g ₁ (t),
Assuming that g ₂ (t), the complex signal Z _± (t) = g ₁ (t) ±
The spectrum of jg ₂ (t) is as shown in FIG. In FIG. 2, the sign of the imaginary part of the complex signal Z _± (t) ±
The spectrum becomes a solid line or a broken line in FIG. The spectrum of the complex signal Z ₊ (t) or Z ₋ (t) is a non-overlapping spectrum.

The impulse responses of the low-pass filters 6 and 7 are h ₁ and h ₂ , respectively, and the complex filter h = h ₁ +
Assuming that the frequency characteristic of jh _{2 has} a pass characteristic only in a positive frequency region including the desired reception signal n as shown in FIG. 2C, the output a of the complex filter h is a = [g ₁ (t ) ± jg ₂ (t)] * _{[h 1 (t) + jh 2} (t) ] _{= g 1 (t) * h} 1 (t) ± _{[-g 2 (t) * h 2} (t) ] + j [ g becomes _{1 (t) * h 2 (} t) ± g 2 (t) * h 1 (t) ]. Here, the symbol * indicates a convolution operation.

Taking the real part, Re (a) = g ₁ (t) * h ₁ (t) ± [−g ₂ (t) * h ₂ (t)]. Accordingly, the real part h ₁ of the complex filter h of characteristics as in FIG. 2 (c), both outputs through a filter 6 having the characteristics of the imaginary part h ₂ are respectively amplified by the amplifiers 8 and 9, an amplifier 8 The sum or difference of the two outputs 9 and 9 is taken by the arithmetic unit 10, and the realized signal a ₁ (t) including the desired reception signal n is obtained from the arithmetic unit 10 as shown in FIG. . Tuning is performed by a pair of filters 6 and 7 in this case.

The output from the arithmetic unit 10 is sample-holded by a sample-hold circuit 11, converted into a digital signal by an A / D converter 12, and processed by a digital signal processing circuit 13.
Demodulated by digital processing, and the demodulated output is D
The signal is converted back to an analog signal by the / A converter 14.

In the above-described embodiment, a band-pass filter may be used instead of the low-pass filters 6 and 7. Further, the low-pass filters 6 and 7 may be AC-coupled low-pass filters. When the low-pass filters 6 and 7 are AC-coupled low-pass filters, the DC component in the input signal of the arithmetic unit 10 can be removed, and the mixers 2 and 5, the local oscillator 4,
The effects of the DC offset of the frequency conversion stage including the phase shifter 3 and the DC offset of the amplifiers 8 and 9 can be eliminated. Further, a band-pass filter may be used instead of the low-pass filters 6 and 7.

In the above-described embodiment, the amplifiers 8 and 9 may be variable gain amplifiers, and AGC for controlling the gain based on the output of the arithmetic unit 10 may be performed. The output level of the arithmetic unit 10 is controlled by performing the AGC. be able to. Further, AGC may be performed based on the output of the D / A converter 14.

The low-pass filters 6 and 7 may be made to have a relatively wide band, and a channel may be selected by a digital filter in the digital signal processing circuit 13 instead of the channel selection by the low-pass filters 6 and 7. Further, the characteristics of the digital filter in the digital signal processing circuit 13 may be variable, and the flexibility improves by making the characteristic variable.

A multiplier for multiplying the output of the low-pass filter 6 and the output of the low-pass filter 7 or a multiplier for multiplying the output of the amplifier 8 and the output of the amplifier 9 is separately provided.
If the phase shift angle of the phase shifter 3 is controlled so that the output of the multiplier becomes zero, the adjustment of the phase shift angle of the phase shifter 3 becomes easy.

Next, a modification of the embodiment of the present invention will be described. FIG. 3 is a block diagram showing a configuration of a main part of a modification of the embodiment of the present invention. In this modification, the outputs of the amplifiers 8 and 9 are supplied to an arithmetic unit 10 for addition or subtraction, and are also supplied to a multiplier 25 for multiplication. The output of the arithmetic unit 10, the output of the amplifier 8, and the output of the amplifier 9 are provided. , The output of the multiplier 25 is selected by the selector 26 and supplied to the sample hold circuit 11 for sample hold.
It is configured to supply to the / D converter 12.

When the output of the arithmetic unit 10 is selected by the selector 26, it is the case of the above-described embodiment. When the output of the multiplier 25 is selected by the selector 26, the phase shift by the phase shifter 3 can be adjusted to π / 2 using the output of the multiplier 25. That is, since the output of the multiplier 25 becomes zero when the phase shift by the phase shifter 3 is correctly π / 2, the phase shift is made such that the phase difference between the outputs of the amplifiers 8 and 9 becomes zero. What is necessary is just to adjust the container 3. Further, it is also possible to use the phase shifter 3 as a variable phase shifter so as to automatically adjust the output of the multiplier 25 to be zero.

Further, by selecting the output of the amplifier 8 by the selector 26, the gain of the amplifier 8 can be adjusted by the output of the amplifier 8, and the level of the low-frequency signal on one side can be adjusted. Become. Similarly, when the output of the amplifier 9 is selected, the gain of the amplifier 9 can be adjusted, and the level of the low-frequency signal on the other side can be adjusted.

[0030]

As described above, according to the radio receiving apparatus of the present invention, one low-frequency signal and the other low-frequency signal, which has been phase-shifted by π / 2, are subjected to addition or subtraction operations. Since the arithmetic output is sample-holded, in the case of digital processing, only one line is required after the sample-hold circuit, and the A / D converter requires only one channel, which has the effect of reducing the circuit scale. In addition, digital processing
Channels can be miniaturized. Further, there is an effect that high-speed processing required for digital processing is eased compared to the case of two channels. In addition, there is an effect that the apparatus can be configured at low cost.

When the AGC for controlling the gain of the amplifier for amplifying the low-frequency signal based on the operation output is performed, the operation output level can be controlled. Further, AGC may be performed based on the output of the D / A converter 14.

Assuming that the low-pass filter has a relatively wide band,
Instead of using a low-pass filter to select a channel, a digital filter in a digital signal processing circuit may be used to select a channel. By making the characteristics of the digital filter variable, the flexibility is improved.

The output of an arithmetic unit for adding or subtracting one or the other low-frequency signal, the output of a multiplier for multiplying the low-frequency signal on one side and the other, the low-frequency signal on one side, and the low-frequency signal on the other side When a selector for selecting any one of the above is provided, the phase shift by the phase shifter can be adjusted to π / 2 by using the output of the multiplier in accordance with the selection of the output by the selector. The level of the low-frequency signal on one side can be adjusted using the low-frequency signal output on the side, and the level of the low-frequency signal on the other side can be adjusted using the low-frequency signal output on the other side. There is an effect that can be done.

When the filter is an AC-coupled filter, the DC component can be removed, and the effect of the DC offset in the components preceding the filter can be eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a spectrum for explaining the operation of an embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a main part of a modification of the embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional example.

FIG. 5 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 2 and 5 mixer 3 phase shifter 4 local oscillator 6 and 7 low-pass filter 10 arithmetic unit 11 sample hold circuit 12 A / D converter 13 digital signal processing circuit 14 D / A converter

Claims (11)

(57) [Claims] 1. A frequency conversion means for converting a received signal into a low-frequency signal orthogonal to each other, a filter for separately inputting outputs from the frequency conversion means to remove image interference, Arithmetic means for inputting and adding or subtracting an output, and A / D for inputting the output of the arithmetic means
A radio receiving apparatus comprising: a converter; and a digital signal processing unit that receives an output of the A / D converter and performs digital demodulation. 2. The radio receiving apparatus according to claim 1, further comprising multiplication means for multiplying the output of the filter. 3. The radio receiving apparatus according to claim 1, further comprising an output terminal for independently outputting an output of the filter. 4. The radio receiving apparatus according to claim 1, further comprising an amplifier for separately inputting the outputs of the filters and outputting the input to the calculating means. 5. A frequency conversion means for converting a received signal into a low-frequency signal orthogonal to each other, a filter for separately receiving outputs from the frequency conversion means to remove image interference, Amplifiers for individually inputting outputs, arithmetic means for adding or subtracting outputs from the amplifiers, multiplying means for inputting and multiplying the outputs from the amplifiers, outputs of the respective amplifiers, outputs of the arithmetic means, and multiplying means Selector means for selecting and outputting one output from among the outputs of the A / D converter, an A / D converter for receiving the output from the selector means, and a digital signal processing means for receiving the output of the A / D converter and performing digital demodulation. A wireless receiving device comprising: 6. The wireless receiving apparatus according to claim 1, wherein the filter is an AC-coupled filter. 7. The radio receiving apparatus according to claim 1, wherein the filter is a low-pass filter. 8. The radio receiving apparatus according to claim 1, wherein the filter is a band-pass filter. 9. The radio receiving apparatus according to claim 1, further comprising a D / A converter to which a digital demodulated output of the digital signal processing means is input. 10. The radio receiving apparatus according to claim 1, wherein the filter is a filter for channel selection. 11. The radio receiving apparatus according to claim 1, wherein the digital filter in the digital signal processing means is a filter for channel selection.