JP5197510B2 - Receiving machine - Google Patents

Description

  The present invention relates to a multimode receiver that receives signals of a plurality of communication systems in different bands.

  A conventional multimode receiver will be described with reference to FIGS. 14 to 17 (see, for example, Patent Document 1). FIG. 14 is a diagram illustrating a configuration of a conventional multimode receiver. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

  In FIG. 14, a conventional multimode receiver includes an antenna 1, a high frequency amplifier 2, three local oscillation sources 3a, 3b, and 3c according to a communication system, a frequency converting mixer 4A, and a low-pass signal. Filter (LPF) 6, variable gain amplifier (VGA) 9, AD converter (A / D) 10, band pass filters (BPF) 21a, 21b, 21c according to the communication system, and channels in the communication system Band pass filters (BPF) 22a, 22b, 22c for selection and a demodulator 11 are provided.

  Next, the operation of a conventional multimode receiver will be described with reference to the drawings.

  FIG. 15 is a diagram illustrating a spectrum of a reception signal of a conventional multimode receiver. FIG. 16 is a diagram showing the spectrum of the output signal of the mixer 4A of the conventional multimode receiver. FIG. 17 is a diagram illustrating a spectrum of noise output from the mixer 4A of the conventional multimode receiver.

  The signals of the plurality of communication systems received by the antenna 1 are amplified by the high frequency amplifier 2 and input to the mixer 4A. The mixer 4A is supplied with local oscillation waves from a plurality of local oscillation sources 3a to 3c corresponding to the communication system. FIG. 15 shows the frequency relationship between the received signal and the local oscillation wave in the mixer 4A, and FIG. 16 shows the frequency relationship between the IF signals output from the mixer 4A.

  In FIG. 15, received signals 101a, 101b, and 101c of the first, second, and third communication systems are depicted, and there are one or more channels, respectively.

  16, IF signals 101a ′ and 101b obtained by frequency-converting the received signals 101a, 101b, and 101c of the first, second, and third communication systems shown in FIG. 15 by the local oscillation waves from the local oscillation sources 3a to 3b. ', 101c' is drawn.

In FIG. 15, the reception signal 101a of the first communication system having the band BW ₁ centered on the frequency _frf1 and having three channels is output from the local oscillation source 3a corresponding to the first communication system, The frequency is converted in the mixer 4A by a local oscillation wave ( _denoted as LO1 in the figure) _having a frequency f _lo1 lower than the highest frequency in the frequency band (BW ₁ ) occupied by the first communication system by Δf ₁ . It is output as an IF signal 101a ′ corresponding to the first communication system. Here, Δf ₁ is set as a frequency slightly higher than BW ₁ .

Similarly, in FIG. 15, the reception signal 101b of the second communication system having the band BW ₂ centered on the frequency _frf2 and having three channels is output from the local oscillation source 3b corresponding to the second communication system. The frequency is converted in the mixer 4A by a local oscillation wave ( _denoted as LO2 in the figure) having a frequency f _{lo2 that} is lower by Δf ₁ + Δf ₂ than the highest frequency in the frequency band (BW ₂ ) occupied by the second communication system. Thus, an IF signal 101b ′ corresponding to the second communication system in FIG. 16 is output. Here, Δf ₂ is set as a frequency slightly higher than BW ₂ .

Similarly, in FIG. 15, the reception signal 101c of the third communication system having the band BW ₃ centered on the frequency _frf3 and having one channel is output from the local oscillation source 3c corresponding to the third communication system. In the mixer 4A, a local oscillation wave ( _denoted as _{LO3 in} the figure) _having a frequency f _lo3 lower by Δf ₁ + Δf ₂ + Δf ₃ than the highest frequency in the frequency band (BW ₃ ) occupied by the third communication system is used. It is converted and output as an IF signal 101c ′ corresponding to the third communication system in FIG. Here, Δf ₃ is set as a frequency slightly higher than BW ₃ .

  The output of the mixer 4A is filtered by the LPF 6, amplified by the VGA 9, converted into a digital signal by the AD converter 10, and is converted for each communication system by the BPFs 21a to 21c corresponding to the first to third communication systems. Further, the signals are separated for each channel by BPFs 22 a to 22 c for channel selection and demodulated by the demodulator 11. With this configuration, a receiver capable of simultaneously receiving a multimode communication system can be realized.

Japanese Patent Laid-Open No. 2004-357025

  However, the prior art has the following problems. Since the conventional multimode receiver is configured as described above, a band pass filter (BPF) is required for system selection and channel selection after frequency conversion by the mixer 4A. With respect to the ratio of the bandwidth to the center frequency of the BPF, that is, the ratio band, if the value is extremely large or small, the circuit scale may increase. In particular, when a broadband modulated wave is filtered at a low frequency such as AD conversion, the circuit scale may be increased. This is not the case when a digital filter is used after AD conversion as in a conventional receiver, but also when a system selection and channel selection are performed using an analog filter before AD conversion.

  Further, in the frequency conversion mixer and IF band circuit, the problem of 1 / f noise generally occurs. The 1 / f noise is also called flicker noise, and depends on the semiconductor constituting the device. The level of the 1 / f noise increases as the frequency approaches a low DC. FIG. 17 shows a spectrum of noise generated by the semiconductor device. The corner frequency at which the 1 / f noise is dominant in the noise and the frequency changing from the frequency domain where the thermal noise is dominant is several tens of kHz to several hundreds in the Si-based device effective for the integration of the receiver IC. When the signal output from the mixer is several MHz or less, the sensitivity deteriorates due to the influence of 1 / f noise.

  The present invention has been made to solve the above-described problems, and can realize a BPF at a low frequency with an appropriate circuit scale and avoid sensitivity deterioration due to the influence of 1 / f noise of the mixer. The object is to obtain a receiver that can be used.

  A receiver according to the present invention orthogonally intersects a reception signal of a communication system having a wide signal band among reception signals of a plurality of communication systems, based on a local oscillator that supplies a plurality of local oscillation waves and the plurality of local oscillation waves. Frequency conversion into two baseband signals, a quadrature mixer that converts the received signal of the communication system having a narrow signal band into two orthogonal IF signals and outputs the signals, and removes unnecessary signals from the two baseband signals A low-pass filter, a band-pass filter that removes unwanted signals from the two IF signals, and a 90-degree phase shifter that changes the phase of one of the two IF signals output from the band-pass filter by 90 degrees , Demodulating two baseband signals output from the low-pass filter, and respectively from the band-pass filter and the 90-degree phase shifter The force is two IF signal synthesized in which and a demodulator for demodulating.

  According to the receiver of the present invention, a wideband modulated signal is converted into a baseband signal by the direct conversion method, so that the baseband filter can be a low-pass filter (LPF). This LPF, like the BPF, changes the circuit scale depending on the steepness of the pass characteristics, but there is almost no change in the circuit scale due to the pass bandwidth, and the wide band pass characteristics can be realized relatively easily compared to the BPF. This has the effect of reducing the circuit scale of the filter at the low frequency of the machine. Also, since the received signal of a communication system using a narrow-band modulated signal is converted to a low IF signal by the low IF method, its frequency is higher than the 1 / f noise corner frequency of the mixer or IF circuit. By setting, there is an effect that sensitivity influence can be suppressed by avoiding the influence of 1 / f noise. Further, since the signal band is narrow, there is an effect that the circuit scale of the filter at a low frequency can be reduced.

It is a figure which shows the structure of the receiver which concerns on Embodiment 1 of this invention. It is a figure which shows the spectrum of the received signal of the receiver which concerns on Embodiment 1 of this invention. It is a figure which shows the spectrum of the output signal of the orthogonal mixer of the receiver which concerns on Embodiment 1 of this invention. It is a figure which shows another structure of the receiver which concerns on Embodiment 1 of this invention. It is a figure which shows another structure of the receiver which concerns on Embodiment 1 of this invention. It is a figure which shows another structure of the receiver which concerns on Embodiment 1 of this invention. It is a figure which shows another structure of the receiver which concerns on Embodiment 1 of this invention. It is a figure which shows another structure of the receiver which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the receiver which concerns on Embodiment 2 of this invention. It is a figure which shows the structure of the receiver which concerns on Embodiment 3 of this invention. It is a figure which shows the structure of the receiver which concerns on Embodiment 4 of this invention. It is a figure which shows the spectrum of the output signal of the orthogonal mixer of the receiver which concerns on Embodiment 4 of this invention. It is a figure which shows the structure of the receiver which concerns on Embodiment 5 of this invention. It is a figure which shows the structure of the conventional multimode receiver. It is a figure which shows the spectrum of the received signal of the conventional multimode receiver. It is a figure which shows the spectrum of the output signal of the mixer of the conventional multimode receiver. It is a figure which shows the spectrum of the noise output from the mixer of the conventional multimode receiver.

  Hereinafter, preferred embodiments of a receiver of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
A receiver according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a diagram showing a configuration of a receiver according to Embodiment 1 of the present invention.

  1, a receiver according to Embodiment 1 of the present invention includes an antenna 1, a high frequency amplifier 2, local oscillation sources 3a and 3b according to a communication system, an orthogonal mixer 4, a low-pass filter (LPF). ) 6a, 6b, band pass filters (BPF) 7a, 7b, IF band 90 degree phase shifter 8, variable gain amplifiers (VGA) 9a, 9b, 9c, and AD converter (A / D) 10a 10b and 10c and a demodulator 11 are provided.

  The quadrature mixer 4 is provided with unit mixers 4a and 4b and a 90-degree phase shifter 5 for local oscillation waves.

  Next, the operation of the receiver according to the first embodiment will be described with reference to the drawings.

  FIG. 2 is a diagram showing a spectrum of a reception signal of the receiver according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing the spectrum of the output signal of the orthogonal mixer of the receiver according to Embodiment 1 of the present invention.

In FIG. 2, the received signal 101a (frequency band is BW ₁ ) of the first communication system that uses a wideband modulated signal and the received signal 101b (frequency band is BW2) of the _second communication system that uses a narrowband modulated signal. ) And noise 102 in a band corresponding to the image signal in the mixers 4a and 4b when the received signal 101b of the second communication system is frequency-converted.

Each band is divided into a plurality of channels, and a signal exists in each channel. The channel bands are bw ₁ and bw ₂ respectively. The center frequency of the signal of the desired channel in the first communication system and f _rf1, if the center frequency of the signal of the desired channel in the second communication system and the f _rf2, the embodiment 1 quadrature mixer 4 in the present embodiment A signal of a desired channel of the first communication system is output from the local oscillation source 3a in FIG. 1 and a local oscillation wave ( _denoted as LO1 in the figure) having the same frequency f _lo1 as the center frequency f _rf1 is used. Then, the signal is converted into a baseband signal by the direct conversion method, and a signal of a desired channel of the second communication system is output from the local oscillation source 3b and has a frequency f _lo2 (denoted as LO2 in the figure). Thus, the frequency is converted into an IF signal having a low frequency so that AD conversion can be performed by a low IF method.

The spectrum of the output signals of the mixers 4a and 4b after the frequency conversion is shown in FIG. The signal 101a ′ of the first communication system converted into the baseband signal by the direct conversion method exists from DC to a frequency that is ½ of BW ₁ , and the desired signal is a bandwidth that is ½ of the channel bandwidth bw _1. Have a width. Further, the signal 101b ′ of the second communication system converted to the IF signal having a low frequency by the low IF method is converted to a higher frequency than the baseband signal converted by the direct conversion method. When the frequency of the signal of the second communication system is converted, the noise 102 ′ of the image signal band converted to the same frequency by the mixers 4a and 4b is shown.

Mixers 4a, the first communication system of the signal 101a output from 4b 'are, LPF6a which is set a pass band to a half of the channel bandwidth bw _1, is removed unnecessary signals by 6b, subsequent VGA9a, by 9b Amplified to an appropriate level, converted into a digital signal by the AD converters 10a and 10b, and demodulated.

On the other hand, mixers 4a, a second communication system of the signal 101b output from 4b 'are, BPF7a which is set a passband equal to the channel bandwidth bw _2, is removed unnecessary signals by 7b, only the output of BPF7a, 90 degrees After receiving a phase shift of 90 degrees by the phase shifter 8, it is synthesized with the output of the BPF 7b. Thereby, when frequency-converting the signal of the second communication system in FIG. 2, the noise 102 ′ in the image signal band subjected to frequency conversion at the same time is suppressed, and only a signal of a desired channel is obtained. Thereafter, the signal is amplified to an appropriate level by the VGA 9c, converted into a digital signal by the AD converter 10c, and demodulated.

  In the first embodiment, a wideband modulation signal is converted into a baseband signal and a low frequency IF signal by a direct conversion method, and a narrowband modulation signal is converted by a low IF method, respectively. Since the former uses LPF for filtering, it can be easily realized even when the pass band must be widened in accordance with the band of the modulation signal. Since the latter has a narrow band, the BPF specific band for filtering this is not so large, and a filter can be realized relatively easily. Thereby, the effect which makes it easy to implement | achieve the filter of a receiver can be acquired. Furthermore, since there is a wideband modulation signal in the vicinity of the DC where the 1 / f noise is at a high level in the mixer and subsequent circuits, it is less susceptible to 1 / f noise than the narrowband modulation signal. Sensitivity deterioration hardly occurs. That is, it is possible to obtain an effect of easily increasing the reception sensitivity of the receiver.

  FIG. 4 is a diagram showing another configuration of the receiver according to Embodiment 1 of the present invention.

  In the first embodiment, the 90-degree phase shifter 5 constituting the quadrature mixer 4 is shared in a plurality of communication systems. However, the first embodiment is not limited to this, and as shown in FIG. The 90-degree phase shifters 5a and 5b may be used in accordance with the frequency of the local oscillation wave output from the oscillation sources 3a and 3b. In this case, the 90-degree phase shifter 5a, 5b may be realized in accordance with the frequency of the local oscillation wave output from the local oscillation sources 3a, 3b, so that the 90-degree phase shifter can be easily realized. . Even in such a configuration, it is possible to improve the feasibility of the filter used in the baseband and IF band, and to obtain the effects of being less susceptible to the influence of 1 / f noise of the mixer and subsequent circuits and less susceptible to sensitivity deterioration. be able to.

  FIG. 5 is a diagram showing another configuration of the receiver according to Embodiment 1 of the present invention.

  In the first embodiment, the number of narrow-band communication systems that are received by the low IF method is one. However, the first embodiment is not limited to this, and simultaneous reception of three or more wireless communication systems is possible. It can also be applied to. FIG. 5 shows such an embodiment. In FIG. 5, in addition to the configuration of FIG. 1, a local oscillation source 3c, BPFs 7c and 7d, a 90-degree phase shifter 8b, a variable amplitude amplifier 9d, and an AD converter are shown. 10d.

  The added circuit is a circuit that operates in correspondence with the third communication system. The local oscillation wave supplied from the local oscillation source 3c performs frequency conversion in the mixers 4a and 4b, and the output is filtered by the BPFs 7c and 7d. The output of the BPF 7c is phase-shifted by the 90-degree phase shifter 8b, synthesized with the output of the BPF 7d, amplified by the variable amplitude amplifier 9d, and converted into a digital signal by the AD converter 10d. That is, by configuring a low-IF receiver for the third communication system, the three communication systems can be received simultaneously. Even in such a configuration, it is possible to improve the feasibility of the filter used in the baseband and IF band, and to obtain the effects of being less susceptible to the influence of 1 / f noise of the mixer and subsequent circuits and less susceptible to sensitivity deterioration. be able to.

  Of course, also in the configuration shown in FIG. 5, the same effect can be obtained even if the 90-degree phase shifter 5 constituting the quadrature mixer 4 is provided at the output of each of the local oscillation sources 3a, 3b, 3c, as in FIG. Needless to say.

  FIG. 6 is a diagram showing another configuration of the receiver according to Embodiment 1 of the present invention.

  Further, as another configuration of the first embodiment, as shown in FIG. 6, the output of the quadrature mixer 4 is converted into a digital signal by using the AD converters 10a and 10b, and then desired by the first communication system. The LPFs 6a and 6b are used for the signals, the unnecessary waves are removed using the BPFs 7a and 7b for the desired signals of the second communication system, and the signals are synthesized after the phase shift by the 90-degree phase shifter 8. Each may be demodulated by the demodulator 11 after being amplified to a desired intensity by the variable gain amplifiers 9a, 9b and 9c. In this case, since the filter is configured by a digital circuit, it is easier to change the center frequency, the pass bandwidth, and the like than when configured by an analog circuit, and another communication system different from a predetermined communication system is used. It is also easy to receive.

  In addition, by combining the configuration shown in FIG. 1 and the configuration shown in FIG. 6, the output of the quadrature mixer 4 is AD-converted only in either the direct conversion method or the low IF method, and then the desired signal is filtered. In the same manner as in the configuration shown in FIG. 1, it is also possible to perform AD filtering and then convert to a digital signal after filtering the desired signal. Even in such a configuration, it is possible to improve the feasibility of the filter used in the baseband and IF band, and to obtain the effects of being less susceptible to the influence of 1 / f noise of the mixer and subsequent circuits and less susceptible to sensitivity deterioration. be able to.

  FIG. 7 is a diagram showing another configuration of the receiver according to Embodiment 1 of the present invention.

  As another configuration of the first embodiment, it is also possible to share an AD converter in the direct conversion method and the low IF method. FIG. 7 is a diagram showing the configuration of such a receiver, in which the output of the IF variable gain amplifier 9c constituting the low IF receiver is used as the variable gain constituting the direct conversion receiver. The signal is combined with the output of the amplifier 9a and input to the AD converter 10a.

  Since the IF signal output from the variable gain amplifier 9c and the baseband signal output from the variable gain amplifier 9a have different frequencies as shown in FIG. 3, they are combined and a digital signal is output in the same AD converter 10a. Can be converted to Thereby, the effect that the number of AD converters can be reduced is obtained.

  FIG. 8 is a diagram showing another configuration of the receiver according to Embodiment 1 of the present invention.

  As another configuration of the first embodiment, it is also possible to combine two IF signals after frequency conversion in a low IF method with a 90-degree phase difference and then filter them with a band-pass filter. FIG. 8 is a diagram showing the configuration of such a receiver. In the figure, one of two IF signals output from the quadrature mixer 4 is changed in phase by 90 degrees by a 90-degree phase shifter 8, It is combined with the other IF signal and then filtered by the band pass filter 7a.

  Filters the desired channel signal by the bandpass filter 7a and combines only one of the IF signals by changing the phase by 90 degrees to suppress noise in the image band converted to the same IF frequency as the desired channel signal. You can do either first. Therefore, this configuration has an effect of reducing the number of IF band-pass filters. Note that this configuration can be realized in the same manner in other embodiments described below, regardless of the present embodiment, thereby obtaining the effect of reducing the number of IF band-pass filters.

Embodiment 2. FIG.
A receiver according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 9 is a diagram showing a configuration of a receiver according to Embodiment 2 of the present invention.

In the second embodiment, as shown in FIG. 9, a local oscillation source 3 a that outputs local oscillation waves f _lo1 and f _lo2 corresponding to a plurality of communication systems is provided, and the frequency to be output is switched and the orthogonal mixer 4 is locally Supply oscillating wave. Thereby, two communication systems can be received at different timings. Even in such a configuration, it is possible to improve the feasibility of a filter used in a low frequency band, and to obtain the effect of being less susceptible to the influence of 1 / f noise of the mixer and subsequent circuits and less susceptible to sensitivity deterioration. it can. Although FIG. 9 shows the case where the second embodiment is applied to the first embodiment, it is needless to say that the second embodiment can be applied to other embodiments.

Embodiment 3 FIG.
A receiver according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 10 is a diagram showing a configuration of a receiver according to Embodiment 3 of the present invention.

  In the third embodiment, as shown in FIG. 10, the outputs of the mixers 4a and 4b are filtered by the BPFs 7a and 7b in the low-IF receiving unit that receives the signal of the second communication system having a narrow band. Then, after further distributing the local oscillation wave from the local oscillation source 3c into two, one is changed as it is and the other is changed by 90 degrees by the phase shifter 8 and then supplied to the mixers 12a and 12b to perform frequency conversion. It may be synthesized from The local oscillation source 3c, the 90-degree phase shifter 8, and the mixers 12a and 12b constitute frequency conversion means.

  In this configuration, the 90-degree phase shifter 8 for the IF signal in the embodiments described so far is not necessary. The phase shifter for the IF signal needs to obtain a phase shift amount of 90 degrees in the entire IF signal band, and there may be a problem of a phase shift amount error at the end of the band. However, in the configuration shown in FIG. It is only necessary to obtain a phase shift amount of 90 degrees only at a fixed local oscillation frequency, which is easy to realize.

  In addition, in frequency conversion by the mixers 12a and 12b, a frequency that facilitates the configuration of the variable gain amplifier 9c and the AD converter 10c in the subsequent stage is selected as the frequency after frequency conversion, thereby facilitating the realization of the receiver. An effect is obtained.

  It is also possible to arrange the variable gain amplifier 9c before the mixers 12a and 12b. In this case, the level of the image signal converted to IF having the same frequency as the desired wave by the mixers 12a and 12b must be smaller than the level of the desired wave, and two IF variable gain amplifiers are required. In addition, it is possible to obtain an effect that sensitivity deterioration due to the influence of the noise figure of the mixers 12a and 12b can be suppressed.

Embodiment 4 FIG.
A receiver according to Embodiment 4 of the present invention will be described with reference to FIGS. FIG. 11 is a diagram showing a configuration of a receiver according to Embodiment 4 of the present invention. FIG. 12 is a diagram showing the spectrum of the output signal of the orthogonal mixer of the receiver according to Embodiment 4 of the present invention.

  In FIG. 11, variable gain amplifiers 13a and 13b for controlling the amplitude of a local oscillation wave supplied to the quadrature mixer 4 are provided.

  When the mixers 4a and 4b reduce the power of the local oscillation wave, the conversion gain decreases. Therefore, if the power of the local oscillation wave is changed according to the level of the received signal of the communication system, the power level of each communication system at the outputs of the mixers 4a and 4b can be made constant.

  This is shown in FIG. In each communication system, the conversion gains of the mixers 4a and 4b are determined in accordance with the signal having the maximum intensity, so that the intensity of the signal output from the mixers 4a and 4b is constant regardless of each communication system. Thereafter, only signals of the first communication system received by the direct conversion method are filtered by the LPFs 6a and 6b, and signals of the second communication system received by the low IF method are filtered by the BPFs 7a and 7b. . The variable gain amplifiers 9a, 9b, and 9c in the first embodiment are not necessary because the quadrature mixer 4 plays a role of variable gain, and are received by the direct conversion method that is output from the LPFs 6a and 6b. The baseband signal of the communication system and the IF signal of the second communication system received by the low-IF method output from the 90-degree phase shifter 8 can be directly input to the AD converters 10a, 10b, and 10c. After being converted into a digital signal, it is demodulated by the demodulator 11. Therefore, the IF band variable gain amplifier can be reduced.

  In the fourth embodiment, the power of the local oscillation wave is changed according to the level of the received signal of the communication system, and the power level of each communication system at the outputs of the mixers 4a and 4b is constant. The form 4 is not limited to this, and the gain of the RF band high-frequency amplifier 2 may also be varied. Thereby, the variable range of the variable gain amplifiers 13a and 13b for controlling the amplitude of the local oscillation wave supplied to the quadrature mixer 4 can be narrowed, and the manufacture thereof can be facilitated.

Embodiment 5 FIG.
A receiver according to Embodiment 5 of the present invention will be described with reference to FIG. FIG. 13 is a diagram showing a configuration of a receiver according to Embodiment 5 of the present invention.

  In FIG. 13, spread code generation circuits 14a and 14b for generating spread codes, and mixers 15a and 15b for mixing the local oscillation waves from the local oscillation sources 3a and 3c and the spread codes from the spread code generation circuits 14a and 14b, Is provided.

  In addition to the first communication system having a wideband modulation signal and the second communication system having a narrowband modulation signal, a third communication system having another wideband modulation signal is simultaneously received. As shown in FIG. 5, a low IF receiver corresponding to the third communication system may be provided. However, when the third communication system has a broadband modulation signal, the low IF method cannot be used, and the direct conversion method may have to be applied. However, when the direct conversion method is applied, it overlaps with the signal of the first communication system in the baseband, which is the output of the orthogonal mixer 4, and cannot be separated.

In the fifth embodiment, the received signal of the communication system having the first and third broadband modulated signals can be separated even if converted to a baseband signal in the orthogonal mixer 4 by applying the direct conversion method. Specifically, the local oscillation waves f _lo1 and f _lo3 supplied to the orthogonal mixer 4 are spread with a spreading code, and the received signal is converted into a baseband signal using this.

  In the fifth embodiment, the received signal of the first communication system and the received signal of the third communication system, which have a wideband modulated signal, are converted into baseband signals by different spreading codes, so that the orthogonal mixer 4 Is output to the same frequency, filtered by the LPFs 6a and 6b, amplified to an appropriate amplitude by the variable gain amplifiers 9a and 9b, converted into digital signals by the AD converters 10a and 10b, and then demodulated by the demodulator 11. By despreading, it can be separated and returned to the original two different signals. Thereby, the signals of a plurality of communication systems having a plurality of broadband modulation signals can be received simultaneously.

  1 antenna, 2 high frequency amplifier, 3a, 3b, 3c local oscillation source, 4 quadrature mixer, 4a, 4b unit mixer, 5, 5a, 5b 90 degree phase shifter, 6a, 6b LPF, 7a, 7b, 7c, 7d BPF 8, 8a, 8b 90 degree phase shifter, 9a, 9b, 9c, 9d variable gain amplifier, 10a, 10b, 10c, 10d AD converter, 11 demodulator, 12a, 12b mixer, 13a, 13b variable gain amplifier, 14a, 14b Spreading code generation circuit, 15a, 15b Mixer.

Claims (7)

A local oscillator for supplying a plurality of local oscillation waves;
Based on the plurality of local oscillation waves, among the reception signals of the plurality of communication systems, the reception signal of the communication system having a wide signal band is frequency-converted to two orthogonal baseband signals, and the reception of the communication system having a narrow signal band is received. An orthogonal mixer that converts the signal into two orthogonal IF signals and outputs the IF signal;
A low-pass filter for removing unwanted signals from the two baseband signals;
A band pass filter for removing unwanted signals from the two IF signals;
A 90-degree phase shifter that changes the phase of one of the two IF signals output from the bandpass filter by 90 degrees;
A demodulator that demodulates two baseband signals output from the low-pass filter and demodulates two IF signals respectively output and synthesized from the bandpass filter and the 90-degree phase shifter. A receiver characterized by that. Instead of the 90-degree phase shifter, based on two local oscillation waves whose phases are different by 90 degrees, frequency conversion means for frequency-converting two IF signals output from the bandpass filter, respectively,
The demodulator demodulates two baseband signals output from the low-pass filter and demodulates two IF signals output from the frequency converting means and synthesized. Receiver. The receiver according to claim 1, wherein the local oscillator simultaneously supplies a plurality of local oscillation waves corresponding to the plurality of communication systems. The receiver according to claim 1, wherein the local oscillator switches and supplies a plurality of local oscillation waves corresponding to the plurality of communication systems. The variable gain amplifier for controlling the amplitude of a local oscillation wave supplied to the quadrature mixer so that the intensity of all signals output from the quadrature mixer is constant is further provided. Item 5. The receiver according to any one of Items 4 to 4. A spreading code generation circuit for generating a spreading code;
The receiver according to any one of claims 1 to 5, further comprising a mixer that mixes a local oscillation wave and the spreading code corresponding to a communication system having a wide signal band. A local oscillation wave is input, and among the received signals of a plurality of communication systems, the received signal of the communication system with a wide signal band is frequency-converted into two orthogonal baseband signals, and the received signal of the communication system with a narrow signal band is converted. A receiver comprising a quadrature mixer for converting and outputting two orthogonal IF signals.

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