JP2004357025A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver which can simplify an arrangement of an analog circuit, realize downsizing of the receiver and low power consumption, and optionally change a receiving communication system. <P>SOLUTION: A receiver is provided with a low noise amplifier 2 which amplifies signals of a plurality of communication systems received by an antenna 1, local oscillation sources 3a-3c which output local oscillation waves, a mixer 4 which generates a mixing wave of the signals of the communication systems and the local oscillation waves to be outputted as an IF signal, a low-pass filter 5 which removes unnecessary waves, a variable gain amplifier 6 which amplifies the IF signal to a predetermined level, an AD converter 7 which converts a signal into a digital signal, band-pass filters 8a-8c which filter signals of a predetermined communication system, band-pass filters 9a-9c which filter a desired signal within the communication system, and a decoding and controlling circuit 10 which decodes the desired signal, where a frequency of the local oscillation waves is set so that the mixing wave may be arranged adjacent on a frequency axis. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a receiver for receiving a plurality of bands simultaneously or a single band.
[0002]
[Prior art]
In order to realize a multi-mode compatible wireless device using the heterodyne method, in some cases, the number of wireless devices must be equal to the number of target systems (or modes) (for example, see Non-Patent Document 1). .
[0003]
[Non-patent document 1]
Editing: Takami Aizawa, "Basics and Application of Software Defined Radio", Publisher: Knowledge Service Business Division, Cypec Co., Ltd., published October 31, 2002, pp. 71-77 [0004]
[Problems to be solved by the invention]
In the conventional receiver, it is necessary to provide mixers, bandpass filters, variable gain amplifiers, and A / D converters by the number of communication systems to be received, and there is a problem that it is difficult to realize a reduction in size and power consumption. .
[0005]
Further, the center frequency and the pass band width of the band-pass filter are determined in advance according to the communication system, and when it is desired to receive a signal of a different communication system, it is necessary to prepare a band-pass filter in advance. However, there is a problem that the method cannot be applied to a software defined radio terminal or the like that arbitrarily changes the communication system to perform.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. It is an object of the present invention to simplify a configuration of an analog circuit to realize a small-sized receiver and a low power consumption. It is possible to obtain a receiver capable of arbitrarily changing a communication system to perform.
[0007]
[Means for Solving the Problems]
A receiver according to the present invention includes: an antenna for receiving signals of a plurality of communication systems; a low-noise amplifier for amplifying signals of the plurality of communication systems received by the antenna; and a setting corresponding to each of the plurality of communication systems. A plurality of local oscillation sources each outputting a local oscillation wave having a set frequency, a plurality of mixed waves from a plurality of communication system signals from the low noise amplifier and a plurality of local oscillation waves from the plurality of local oscillation sources. , And a single mixer for outputting the IF signal as an IF signal, a filter for removing unnecessary waves output from the mixer, and a variable gain amplifier for amplifying the output of the filter to a predetermined level. An AD converter for converting an output of the variable gain amplifier into a digital signal; a plurality of first bandpass filters for filtering a signal of a desired communication system from an output of the AD converter; A plurality of second band-pass filters for respectively filtering a desired signal in the desired communication system from an output of the first band-pass filter; and a demodulation for demodulating a desired signal from the plurality of second band-pass filters. And a circuit, wherein the frequencies of the plurality of local oscillation waves are set such that the plurality of mixed waves are arranged adjacent to each other on a frequency axis.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
A receiver according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a receiver according to Embodiment 1 of the present invention. In the drawings, the same reference numerals indicate the same or corresponding parts.
[0009]
In FIG. 1, the receiver includes an antenna 1 for receiving signals of a plurality of communication systems, a low-noise amplifier 2 for amplifying signals of the plurality of communication systems received by the antenna 1, and a plurality of communication systems. A local oscillation source 3a, 3b, 3c for outputting a local oscillation wave having a frequency set respectively, a mixer 4 for generating a mixed wave of signals of a plurality of communication systems and a local oscillation wave and outputting it as an IF signal; Low-pass filter (LPF) 5 for removing waves, variable gain amplifier 6 for amplifying the output of low-pass filter 5 to a predetermined level, and AD conversion for converting the output of variable gain amplifier 6 to a digital signal (A / D) 7, a band-pass filter (BPF) (first band-pass filter) 8a, 8b, 8c for filtering a desired communication system; Comprising bandpass filter for filtering the desired signal (the second band-pass filter) 9a, 9b, and 9c, the demodulation and control circuitry (demodulator) 10 for such demodulating a desired signal, and an output terminal 11.
[0010]
Next, the operation of the receiver according to the first embodiment will be described with reference to the drawings.
[0011]
FIG. 2 is a diagram showing a relationship between a signal of the communication system received by the receiver according to Embodiment 1 of the present invention and a frequency of a local oscillation wave supplied to the mixer.
[0012]
FIG. 3 is a diagram showing a relationship between output signals (a plurality of mixed waves) of the mixer of the receiver according to Embodiment 1 of the present invention. FIG. 4 is a diagram showing a frequency relationship between the IF signal of the receiver according to Embodiment 1 of the present invention and a band-pass filter for filtering a desired communication system. FIG. 5 is a diagram showing a frequency relationship between the IF signal of the communication system received by the receiver according to Embodiment 1 of the present invention and a band-pass filter for filtering a desired signal.
[0013]
Signals of a plurality of communication systems received by the antenna 1 are amplified by the low-noise amplifier 2 and then input to the mixer 4. The mixer 4 has an RF signal input terminal, an IF signal output terminal, and a plurality of local oscillation wave input terminals.
[0014]
FIG. 2 shows the relationship between the received signal of the communication system and the frequency of the local oscillation (LO) wave supplied to the mixer 4. Frequency f _lo1 the LO wave supplied from the local oscillator source 3a is set slightly lower frequency than the lower limit frequency of the frequency bandwidth BW ₁ occupied by the communication system 12a.
[0015]
And an upper frequency limit of the frequency band occupied by the communication system 12a, and the frequency interval of the frequency _{f lo1} the LO wave is Delta] f _1, the frequency _{f lo2} the LO wave supplied from the local oscillator source 3b, the frequency occupied by the communication system 12b slightly set from a low frequency to a lower frequency by a frequency interval Delta] f ₁ than the lower limit frequency of the bandwidth BW _2.
[0016]
Further, an upper limit frequency of the frequency band BW ₂ occupied by the communication system 12b, and the frequency interval of the frequency _{f lo2} the LO wave is Delta] f _2, the frequency _{f lo3} the LO wave supplied from the local oscillator source 3c is a communication system 12c set to a frequency lower by a frequency interval Δf 1 ₊ Δf ₂ from a slightly lower frequency than the lower limit frequency of the frequency bandwidth BW ₃ occupied. Here, the communication systems 12a, 12b, and 12c indicate systems having different frequencies and modulation schemes, such as PDC, PHS, and W-CDMA.
[0017]
The mixer 4 generates a mixed wave of the communication system 12a and the LO wave frequency f _lo1 , the communication system 12b and the LO wave frequency f _lo2 , and the communication system 12c and the LO wave frequency f _lo3. Is output as
[0018]
FIG. 3 shows the spectrum of the IF band. In FIG. 3, reference numerals 12a ', 12b', and 12c 'denote _differences between the communication system 12a and the LO wave frequency f _lo1 , the communication system 12b and the LO wave frequency f _lo2 , and the communication system 12c and the LO wave frequency f _lo3 , respectively. It is a frequency signal (mixed wave).
[0019]
These signals are filtered by a low-pass filter 5 to remove unnecessary waves such as mixed-wave components having a higher frequency, and are amplified to an appropriate level by a variable gain amplifier 6, and then converted to digital signals by an AD converter 7.
[0020]
Further, the bandpass filters 8a, 8b, 8c filter the difference frequency signals 12a ', 12b', 12c 'of the communication systems 12a, 12b, 12c. Reference numeral 13 in FIG. 4 indicates a pass characteristic of the band-pass filter 8b that filters the difference frequency signal 12b 'of the communication system 12b, thereby removing the difference frequency signals 12a' and 12c 'of the communication systems 12a and 12c. I do.
[0021]
Further, the desired signal in the desired communication system is filtered by the band-pass filters 9a, 9b, 9c. Reference numeral 14 in FIG. 5 indicates a pass characteristic of the band-pass filter 9b that filters a desired wave in the communication system 12b, and other signals in the communication system 12b are removed. In this way, only the desired wave in each communication system is demodulated in the demodulation and control circuit 10, and only the desired signal in any one of the communication systems is output from the output terminal 11.
[0022]
That is, the receiver according to the first embodiment simultaneously receives the received signals of the plurality of communication systems and the plurality of local oscillation waves, and receives a plurality of signals from the plurality of communication systems and the plurality of local oscillation waves. A mixer 4 for outputting a wave, and as shown in FIG. 3, the frequencies of the plurality of local oscillation waves are set such that the plurality of mixed waves are arranged adjacently on a frequency axis. .
[0023]
As described above, in the receiver according to the first embodiment, since a single mixer 4 converts received signals of a plurality of communication systems into IF signals, the number of mixers and bandwidths is equal to the number of communication systems to be received. It is not necessary to provide an analog circuit such as a pass filter and a variable gain amplifier or an AD converter, and it is possible to reduce the size and power consumption of the receiver. The band-pass filters 8a to 8c and 9a to 9c are all constituted by digital circuits, and the center frequency and the pass bandwidth can be easily changed by changing the coefficients of the transfer function. Therefore, the present invention can be applied to a software defined radio terminal or the like that arbitrarily changes a receiving communication system. If a plurality of output terminals 11 are provided to output demodulated signals of received waves of different communication systems, simultaneous reception of a plurality of communication systems is possible.
[0024]
Embodiment 2 FIG.
Embodiment 2 A receiver according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 6 is a diagram showing a configuration of a receiver according to Embodiment 2 of the present invention.
[0025]
6, the receiver includes an antenna 1, a low-noise amplifier 2, local oscillation sources 3a, 3b, 3c, a mixer 4, a low-pass filter (LPF) 5, and an AD converter (A / D ) 7, a band-pass filter (BPF) (first band-pass filter) 8a, 8b, 8c for filtering a desired communication system, and a band-pass filter (BPF) (BPF) for filtering a desired signal in the communication system. A second band pass filter) 9a, 9b, 9c, a demodulation and control circuit (demodulation circuit) 10, an output terminal 11, and variable gain amplifiers 15a, 15b, 15c.
[0026]
Next, the operation of the receiver according to the second embodiment will be described with reference to the drawings.
[0027]
FIG. 7 is a diagram illustrating a relationship between output signals (a plurality of mixed waves) of a mixer of a receiver according to Embodiment 2 of the present invention.
[0028]
As in the first embodiment, signals of a plurality of communication systems received by the antenna 1 are amplified by the low noise amplifier 2 and converted to IF signals by the mixer 4. The frequency relationship between the received signal input to mixer 4 and the LO wave is represented in FIG. 2 as in the first embodiment, but in the second embodiment, the outputs of local oscillation sources 3a, 3b, and 3c are connected to variable gain amplifier 15a. , 15b, and 15c, and changes the level, and inputs to the mixer 4.
[0029]
Normally, the conversion gain of the mixer 4 decreases when the LO power is reduced. Therefore, when the LO power is changed according to the level of the received signal of the communication system, the power level of each communication system at the output of the mixer 4 becomes constant. This is shown in FIG. Thereafter, another mixed wave generated in the mixer 4 is removed by a low-pass filter (LPF) 5 and converted into a digital signal by an AD converter 7.
[0030]
Thereafter, the desired communication system is filtered by band-pass filters 8a, 8b, 8c corresponding to the bandwidth of each communication system, and further, band-pass filters 9a, 9b, 9c filters the desired signal. In this way, only the desired signal in each communication system is demodulated in the demodulation and control circuit 10, and only the desired signal in any one of the communication systems is output from the output terminal 11.
[0031]
That is, the receiver according to the second embodiment receives the received signals of the plurality of communication systems and the plurality of local oscillation waves, and receives a plurality of mixed waves from the signals of the plurality of communication systems and the plurality of local oscillation waves. , And the power of the plurality of local oscillation waves is changed according to the signal strength of the communication system input to the mixer 4, and as shown in FIG. The corresponding mixed waves have the same signal strength.
[0032]
As described above, in the receiver according to the second embodiment, since a single mixer 4 converts received signals of a plurality of communication systems into IF signals, the number of mixers and bandwidths is equal to the number of communication systems to be received. It is not necessary to provide an analog circuit such as a pass filter and a variable gain amplifier or an AD converter, and it is possible to realize a downsized receiver and low power consumption. The band-pass filters 8a to 8c and 9a to 9c are all constituted by digital circuits, and the center frequency and the pass bandwidth can be easily changed by changing the coefficients of the transfer function. Therefore, the present invention can be applied to a software defined radio terminal or the like that arbitrarily changes a receiving communication system. If a plurality of output terminals 11 are provided to output demodulated signals of received waves of different communication systems, simultaneous reception of a plurality of communication systems is possible.
[0033]
Further, since the level of each communication system input to the AD converter 7 by controlling the LO power is made the same, the number of bits of the AD converter 7 can be effectively used in all communication systems, and the same system can be used. It is possible to accurately demodulate a weak signal in the signal.
[0034]
Embodiment 3 FIG.
Embodiment 3 A receiver according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 8 is a diagram showing a configuration of a receiver according to Embodiment 3 of the present invention.
[0035]
8, the receiver includes an antenna 1, a low-noise amplifier 2, local oscillation sources 3a, 3b, 3c, a mixer 4, a low-pass filter (LPF) 5, a variable gain amplifier 6, an AD A converter (A / D) 7, a band pass filter (BPF) (first band pass filter) 8a, 8b, 8c for filtering a desired communication system, and a band for filtering a desired signal in the communication system. It includes a pass filter (BPF) (second band pass filter) 9a, 9b, 9c, a demodulation and control circuit (demodulation circuit) 10, and an output terminal 11.
[0036]
Next, the operation of the receiver according to the third embodiment will be described with reference to the drawings.
[0037]
FIG. 9 is a diagram showing a relationship between a signal of a communication system received by a receiver according to Embodiment 3 of the present invention and a frequency of a local oscillation wave supplied to a mixer.
[0038]
FIG. 10 is a diagram illustrating a relationship between output signals (a plurality of mixed waves) of the mixer of the receiver according to Embodiment 3 of the present invention. FIG. 11 is a diagram showing a frequency relationship between an IF signal of a receiver and a band-pass filter for filtering a desired communication system according to Embodiment 3 of the present invention.
[0039]
Signals of a plurality of communication systems received by the antenna 1 are amplified by the low-noise amplifier 2 and then input to the mixer 4. The mixer 4 has an RF signal input terminal, an IF signal output terminal, and a plurality of local oscillation wave input terminals.
[0040]
FIG. 9 shows the relationship between the received signal of the communication system and the frequency of the local oscillation (LO) wave supplied to the mixer 4. Frequency _{f lo1} the LO wave supplied from the local oscillator source 3a is somewhat lower limit frequency of the frequency bandwidth BW ₁ occupied by the communication system 12a, is set to a low frequency.
[0041]
And an upper frequency limit of the frequency band occupied by the communication system 12a, and the frequency interval of the frequency _{f lo1} the LO wave is Delta] f _1, the frequency _{f lo2} the LO wave supplied from the local oscillator source 3b, the frequency occupied by the communication system 12b somewhat lower limit frequency bandwidth BW _2, set to a lower frequency by a frequency interval Delta] f ₁ from a low frequency.
[0042]
Further, an upper limit frequency of the frequency band BW ₂ occupied by the communication system 12b, and the frequency interval of the frequency _{f lo2} the LO wave is Delta] f _2, the frequency _{f lo3} the LO wave supplied from the local oscillator source 3c is a communication system 12c somewhat lower limit frequency of the frequency bandwidth BW ₃ occupied by the set to a low frequency from a low frequency by a frequency interval Δf 1 ₊ Δf _2.
[0043]
The mixer 4 generates a mixed wave of the communication system 12a and the LO wave frequency f _lo1 , the communication system 12b and the LO wave frequency f _lo2 , and the communication system 12c and the LO wave frequency f _lo3. Is output as
[0044]
FIG. 10 shows the spectrum of the IF band. In FIG. 10, reference numerals 12a ', 12b', and 12c 'denote _differences between the communication system 12a and the LO wave frequency f _lo1 , the communication system 12b and the LO wave frequency f _lo2 , and the communication system 12c and the LO wave frequency f _lo3 , respectively. It is a frequency signal (mixed wave).
[0045]
These signals are filtered by a low-pass filter 5 to remove unnecessary waves, amplified by a variable gain amplifier 6 to an appropriate level, and then converted into digital signals by an AD converter 7.
[0046]
Then, the signals of the communication systems 12a, 12b, 12c are filtered by the band-pass filters 8a, 8b, 8c. FIG. 11 shows the spectrum of the IF band and the frequency characteristics of the band-pass filter 8b. Reference numeral 13 in FIG. 11 indicates a pass characteristic of the band-pass filter 8b.
[0047]
Further, the desired signals in the corresponding communication system are filtered by the band-pass filters 9a, 9b, 9c. For example, the bandpass filter 9b filters only one signal in the communication system 12b and removes other signals. In this way, only the desired wave in each communication system is demodulated in the demodulation and control circuit 10, and only the desired signal in any one of the communication systems is output from the output terminal 11.
[0048]
That is, the receiver according to the third embodiment simultaneously receives the received signals of the plurality of communication systems and the plurality of local oscillation waves, and performs multiple mixing of the signals of the plurality of communication systems and the plurality of local oscillation waves. A mixer 4 for outputting a wave is provided, and as shown in FIG. 10, the frequencies of the plurality of local oscillation waves are set such that the plurality of mixed waves are arranged at predetermined intervals on a frequency axis. It was done.
[0049]
As described above, in the receiver according to the third embodiment, since a single mixer 4 converts received signals of a plurality of communication systems into IF signals, the number of mixers and bandwidths is equal to the number of receiving communication systems. It is not necessary to provide an analog circuit such as a pass filter and a variable gain amplifier or an AD converter, and it is possible to reduce the size and power consumption of the receiver. The band-pass filters 8a to 8c and 9a to 9c are all constituted by digital circuits, and the center frequency and the pass bandwidth can be easily changed by changing the coefficients of the transfer function. Therefore, the present invention can be applied to a software defined radio terminal or the like that arbitrarily changes a receiving communication system. If a plurality of output terminals 11 are provided to output demodulated signals of received waves of different communication systems, simultaneous reception of a plurality of communication systems is possible.
[0050]
Further, when comparing the spectrum of the IF band shown in FIG. 10 with the spectrum of the IF band in the receiver according to Embodiment 1 shown in FIG. 3, the frequency difference between the communication systems is large. Therefore, the pass characteristic 13 of the band-pass filter 8b in FIG. 11 does not need to be steeper than that of the receiver according to the first embodiment. That is, since the frequency interval between the communication systems is wide in the IF band, the characteristics of the digital filter for separating the signals of the communication systems are alleviated, and the characteristics can be easily realized.
[0051]
Embodiment 4 FIG.
Embodiment 4 A receiver according to Embodiment 4 of the present invention will be described with reference to the drawings. FIG. 12 is a diagram showing a configuration of a receiver according to Embodiment 4 of the present invention.
[0052]
In FIG. 12, the receiver includes an antenna 1, a low-noise amplifier 2, a local oscillation source 3, a mixer 4, a low-pass filter (LPF) 5, an AD converter (A / D) 7, The communication system includes a band-pass filter (BPF) 9 for filtering a desired signal in the communication system, a demodulation and control circuit (demodulation circuit) 10, an output terminal 11, and a variable gain amplifier 15.
[0053]
Next, the operation of the receiver according to Embodiment 4 will be described with reference to the drawings.
[0054]
The signal of the single communication system received by the antenna 1 is amplified by the low noise amplifier 2 and converted into an IF signal by the mixer 4. At this time, the conversion gain of the mixer 4 is changed by controlling the LO power supplied to the mixer 4 by the variable gain amplifier 15 so that the level of the IF signal output from the mixer 4 is constant.
[0055]
Then, an unnecessary wave output from the mixer 4 is removed by a low-pass filter (LPF) 5, converted into a digital signal by an AD converter 7, and an unnecessary signal is removed by a band-pass filter (BPF) 9. The demodulation and control circuit 10 demodulates the signal and outputs a desired signal from the output terminal 11.
[0056]
That is, the receiver according to the fourth embodiment uses the mixer 4 that inputs a signal of a single communication system and a local oscillation wave and outputs a mixed wave of the signal of the communication system and the local oscillation wave, Further, the power of the local oscillation wave is changed according to the signal strength of a desired signal in the communication system so that the IF signal output from the mixer 4 is always at a constant level.
[0057]
The receiver according to the fourth embodiment realizes AGC for a signal by controlling LO power, and thus does not require a variable gain amplifier for an RF signal or an IF signal. In the case of a variable gain amplifier for an RF signal or an IF signal, if there is a gain deviation in the signal band, the passing signal is distorted. On the other hand, in the present receiver, since the level of the LO wave which is a sine wave may be controlled, there is no need to consider a gain deviation in a signal band, and there is an advantage that the receiver can be easily realized.
[0058]
In the fourth embodiment, the configuration in which unnecessary waves are removed by the band-pass filter 9 after AD conversion has been described. However, the present invention is not limited to this. It is also applicable to machines.
[0059]
In addition, the present invention is not limited to the mixer for heterodyne, but is also applicable to a quadrature mixer for converting a modulated signal into I and Q baseband signals. In particular, a direct conversion receiver requires an AGC amplifier having a very wide variable gain range in baseband, but the present invention can eliminate this. Further, by combining the conversion gain control of the quadrature mixer by varying the LO power and the gain control by the baseband AGC amplifier and the RF band AGC amplifier, it is possible to relatively easily realize a very wide variable gain range. Become.
[0060]
【The invention's effect】
As described above, the receiver according to the present invention does not need to include mixers, filters, AD converters, and the like in accordance with the number of communication systems desired to be received, and has the effect of being compact.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a receiver according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing a relationship between a signal of the communication system received by the receiver according to Embodiment 1 of the present invention and a frequency of an LO wave supplied to a mixer.
FIG. 3 is a diagram showing a relationship between output signals of a mixer of the receiver according to Embodiment 1 of the present invention.
FIG. 4 is a diagram illustrating a frequency relationship between an IF signal of the receiver and a band-pass filter for filtering a desired communication system according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a frequency relationship between an IF signal of the communication system received by the receiver according to the first embodiment of the present invention and a band-pass filter for filtering a desired signal.
FIG. 6 is a diagram showing a configuration of a receiver according to Embodiment 2 of the present invention.
FIG. 7 is a diagram showing a relationship between output signals of a mixer of a receiver according to Embodiment 2 of the present invention.
FIG. 8 is a diagram showing a configuration of a receiver according to Embodiment 3 of the present invention.
FIG. 9 is a diagram showing a relationship between a signal of a communication system received by a receiver according to Embodiment 3 of the present invention and a frequency of an LO wave supplied to a mixer.
FIG. 10 is a diagram showing a relationship between output signals of a mixer of a receiver according to Embodiment 3 of the present invention.
FIG. 11 is a diagram showing a frequency relationship between an IF signal of a receiver and a band-pass filter for filtering a desired communication system according to Embodiment 3 of the present invention.
FIG. 12 is a diagram showing a configuration of a receiver according to Embodiment 4 of the present invention.
[Explanation of symbols]
Reference Signs List 1 antenna, 2 low noise amplifier, 3 3a, 3b, 3c local oscillation source, 4 mixer, 5 low-pass filter (LPF), 6 variable gain amplifier, 7 AD converter (A / D), 8a, 8b, 8c band pass filter (BPF), 9, 9a, 9b, 9c band pass filter (BPF), 10 demodulation and control circuit, 11 output terminals, 15, 15a, 15b, 15c variable gain amplifier.

Claims (4)

An antenna for receiving signals of a plurality of communication systems;
A low noise amplifier that amplifies signals of the plurality of communication systems received by the antenna,
A plurality of local oscillation sources each outputting a local oscillation wave having a frequency set according to the plurality of communication systems,
A single mixer that generates a plurality of mixed waves from a plurality of local oscillation waves from the plurality of communication signals from the plurality of communication systems from the low noise amplifier and a plurality of local oscillation waves from the plurality of local oscillation sources, and outputs as an IF signal;
A filter for removing unnecessary waves output from the mixer,
A variable gain amplifier for amplifying the output of the filter to a predetermined level;
An AD converter that converts an output of the variable gain amplifier into a digital signal;
A plurality of first band-pass filters each filtering a signal of a desired communication system from an output of the AD converter;
A plurality of second bandpass filters each filtering a desired signal in the desired communication system from outputs of the plurality of first bandpass filters;
A demodulation circuit for demodulating a desired signal from the plurality of second band-pass filters,
A receiver characterized in that the frequencies of the plurality of local oscillation waves are set such that the plurality of mixed waves are arranged adjacently on a frequency axis. An antenna for receiving signals of a plurality of communication systems;
A low noise amplifier that amplifies signals of the plurality of communication systems received by the antenna,
A plurality of local oscillation sources each outputting a local oscillation wave having a frequency set according to the plurality of communication systems,
A plurality of variable gain amplifiers that respectively change the power of the plurality of local oscillation waves according to the signal strengths of the plurality of communication systems,
A single mixer that generates a plurality of mixed waves from a plurality of local oscillation waves from the plurality of communication systems signals from the low noise amplifier and a plurality of local oscillation waves from the plurality of variable gain amplifiers, and outputs as an IF signal;
A filter for removing unnecessary waves output from the mixer,
An AD converter for converting the output of the filter into a digital signal;
A plurality of first band-pass filters each filtering a signal of a desired communication system from an output of the AD converter;
A plurality of second bandpass filters each filtering a desired signal in the desired communication system from outputs of the plurality of first bandpass filters;
A demodulation circuit for demodulating a desired signal from the plurality of second band-pass filters,
A receiver characterized in that a plurality of mixed waves corresponding to the plurality of communication systems have the same signal strength. An antenna for receiving signals of a plurality of communication systems;
A low noise amplifier that amplifies signals of the plurality of communication systems received by the antenna,
A plurality of local oscillation sources each outputting a local oscillation wave having a frequency set according to the plurality of communication systems,
A single mixer that generates a plurality of mixed waves from a plurality of local oscillation waves from the plurality of communication signals from the plurality of communication systems from the low noise amplifier and a plurality of local oscillation waves from the plurality of local oscillation sources, and outputs as an IF signal;
A filter for removing unnecessary waves output from the mixer,
A variable gain amplifier for amplifying the output of the filter to a predetermined level;
An AD converter that converts an output of the variable gain amplifier into a digital signal;
A plurality of first band-pass filters each filtering a signal of a desired communication system from an output of the AD converter;
A plurality of second bandpass filters each filtering a desired signal in the desired communication system from outputs of the plurality of first bandpass filters;
A demodulation circuit for demodulating a desired signal from the plurality of second band-pass filters,
A receiver, wherein the frequencies of the plurality of local oscillation waves are set such that the plurality of mixed waves are arranged at predetermined intervals on a frequency axis. An antenna for receiving a signal of a single communication system;
A low noise amplifier that amplifies a single communication system signal received by the antenna;
A local oscillation source that outputs a local oscillation wave having a frequency set according to the communication system,
A variable gain amplifier that changes the power of the local oscillation wave according to the signal strength of a desired signal of the communication system,
A mixer that generates a mixed wave of a signal of a single communication system from the low noise amplifier and a local oscillation wave from the variable gain amplifier and outputs the signal as an IF signal;
A filter for removing unnecessary waves output from the mixer,
An AD converter for converting the output of the filter into a digital signal;
A band-pass filter for filtering a desired signal in the communication system from an output of the AD converter;
A demodulation circuit for demodulating a desired signal from the band-pass filter,
A receiver wherein the IF signal output from the mixer is always at a constant level.

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