JPH01221022A - Ssb receiver - Google Patents

Abstract

PURPOSE:To eliminate phase distortion caused in a reception signal due to fading and to obtain a demodulation signal with high quality by using a random FM noise rejection circuit or a selection amplifier circuit to a reception system. CONSTITUTION:A signal coming to an antenna 1 is subject to high frequency amplification and frequency conversion by a reception circuit 3 into an intermediate frequency signal and subject to selection amplification by an intermediate frequency circuit 5. The receiver is provided with a random FM noise rejection circuit 12 with the reception signal passing therethrough and the selection amplifier circuit 12 and its output signal is sent to a terminal 14. The random FM noise rejection circuit 12 obtains a carrier synchronously with the reception signal from which the effect of propagation distortion is eliminated with stable amplitude, gives a delay to an SSB signal mixed with the carrier and the phase with the carrier is matched and the local oscillation frequency is fluctuated to eliminate random FM noise in a high degree.

Description

[Detailed description of the invention] [Industrial application field] The present invention is suitable for use in mobile radio communications.

The present invention provides SSB (
(single sideband modulation) receiving device.

[Conventional technology]

In car telephone systems and other mobile radio communication systems that can be connected to public communication networks, in order to increase frequency usage efficiency,
The use of the SSB method is being considered. In mobile radio communication systems, complex reflections occur in radio waves, resulting in diverse propagation paths and phase distortion in received signals. Conventionally, automatic gain control (AGC) circuits or automatic frequency control (AFC) circuits have been used to improve the quality of received demodulated signals against fading (for example, Japanese Patent Laid-Open No. 172413/1983) ) can be removed to some extent with this method, but it is caused by signals that have passed through many propagation paths caused by reflections and are received as a result of being synthesized. This is not sufficient to remove phase distortion that fluctuates (hereinafter referred to as "random FM noise").

In order to improve this, the inventor of the present invention proposed an SSB receiver equipped with a random FM noise removal circuit as a prior invention (Japanese Patent Application No. 62-99907).

[Problem that the invention seeks to solve]

Referring to FIG. 3, this random FM noise removal circuit includes a frequency mixing circuit 23 that mixes a local oscillation signal with a received signal (which is suitably an intermediate frequency signal), and an output signal of this frequency mixing circuit. A bandpass filter 25 for extracting a carrier component, an amplitude limiting circuit 26 for limiting the amplitude of the output signal of the bandpass filter, and a frequency mixing circuit 27 for mixing the received signal with the output of the amplitude limiting circuit. This is a circuit that includes It has also been found that the received signal mixed by the frequency mixing circuit 27 is preferably a signal delayed via the delay circuit 22.

When the inventors conducted tests using this circuit, they found that random FM noise remained that could not be removed.

It has been found that the reason for this is that by improving the delay circuit described above, it is possible to perform SSB demodulation with even better quality.

In other words, the purpose of the present invention is to eliminate phase distortion (random FM noise) that occurs due to the synthesis and reception of signals that have passed through multiple propagation paths caused by reflection, and whose value fluctuates over time. It is an object of the present invention to provide a device capable of demodulating a high-quality SSB signal by sufficiently removing the SSB signals.

[Means for solving problems]

The device of the present invention is characterized in that it includes a random FM noise removal circuit through which the received signal passes. Similarly, a selective amplification circuit through which the received signal passes can be provided. These two circuits are connected in a cascade, and either one may be the previous stage.

This random FM noise removal circuit includes a frequency mixing circuit that mixes a local oscillation signal with the received signal, a bandpass filter that extracts a carrier component from the output signal of this frequency mixing circuit, and an output signal of this bandpass filter. This circuit includes an amplitude limiting circuit that limits the amplitude of the received signal, a delay circuit that delays the received signal, and a frequency mixing circuit that mixes the output of this delay circuit and the output of the amplitude limiting circuit.

The selection amplification circuit also includes a bandpass filter that extracts a carrier component, an amplifier that amplifies the output signal of the bandpass filter, a delay circuit that delays the output of the random FM noise removal circuit, and a delay circuit that delays the output of the random FM noise removal circuit. This circuit includes a circuit output and a synthesis circuit that synthesizes the output of the amplifier.

Here, the delay circuit of the random FM noise removal circuit or the delay circuit of the selective amplification circuit includes a frequency variable local oscillation circuit, a frequency mixing circuit that converts the frequency of an input signal by the output of the local oscillation circuit, and a frequency mixing circuit that converts the frequency of the input signal by the output of the local oscillation circuit. A bandpass filter that selects a desired frequency from the output of the mixing circuit, a delay element that delays the output of the bandpass filter, and a frequency mixing circuit that converts the frequency using the output of the delay element and the output of the local oscillator circuit. and a bandpass filter that selects a frequency equal to the input signal from the output of the frequency mixing circuit.

Part or all of the above bandpass filter can be configured by a digital filter.

The present invention can be applied to a diversity receiving device. That is, in a diversity receiving device that receives one SSB signal using multiple antennas and multiple receiving systems and combines the received outputs, the random FM noise removal circuit or selective amplification circuit of the present invention can be used in each receiving system. Can be done.

[Effect]

The random FM noise removal circuit extracts the carrier wave component and limits its amplitude to obtain a carrier wave whose frequency and phase are equal to that of the carrier wave of the received signal, and whose amplitude is stable with the influence of propagation distortion removed.

This carrier wave is used as a carrier wave for demodulating the SSB signal.

This allows random FM noise to be removed to a considerable extent. Furthermore, in the present invention, apart from extracting the carrier wave, a delay is given to the SSB signal mixed with the carrier wave to match the phase with the carrier wave, and this delay circuit is equipped with a heterodyne conversion type delay circuit as described above. In addition, the local oscillation frequency for this heterodyne conversion is varied to adaptively change the phase of the signal passing through the delay circuit, thereby achieving a high degree of random FM noise removal.

This principle is similarly applied to selective amplification circuits.

That is, extracting the carrier included in the SSB received signal,
By separately amplifying this carrier wave and combining it with the received signal, it is possible to demodulate the SSB signal using a stable carrier wave. In this case, a delay is given to the SSB signal to be synthesized to match the phase with the carrier wave, and a hetero gain conversion type delay circuit as described above is used for this delay circuit.
Furthermore, by varying the local oscillation frequency for this heterodyne conversion and adaptively changing the phase of the signal that has passed through the delay circuit, the phase matching with the carrier wave can be further improved.

When the present invention is used in a diversity receiving device, the output signal phase of each diversity receiving system can be adjusted equally, so that the quality of the combined output is extremely high. In practical terms, the click noise that occurs when the reception level drops is reduced, and the quality of the reception signal is dramatically improved.

The circuit of the present invention extracts a carrier wave contained in a received signal and performs stable feed processing. By mixing the delay caused by the bandpass filter for extracting the carrier wave and delaying the signal by the delay circuit, equalization matching is achieved and random FM noise is sufficiently removed.

In a selective amplification circuit that selectively amplifies a carrier wave, the SSB signal satisfies a real zero condition, thereby making it possible to use an amplitude limiting circuit. In this circuit as well, the signal for combining the delays of the band-pass filters for extracting carrier waves is delayed by a delay circuit to achieve equalization matching and prevent deterioration from occurring due to the combination.

〔Example〕

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. This device receives the transmitted SSB signal with an added carrier wave. The signal arriving at the antenna 1 is high-frequency amplified and frequency-converted by the receiving circuit 3 to become an intermediate frequency signal.
It is selectively amplified by the intermediate frequency circuit 5. This device includes a random FM noise removal circuit 12 and a selective amplification circuit 13 through which the received signal passes, and an output signal thereof is sent to a terminal 14.

FIG. 3 is a block diagram of this random FM noise removal circuit 13. This circuit includes a frequency mixing circuit 23 that mixes a local oscillation signal with an input received signal, a bandpass filter 25 that extracts a carrier component from the output signal of this frequency mixing circuit, and an amplitude of the output signal of this bandpass filter. The configuration includes an amplitude limiting circuit 26 that limits the amplitude, a delay circuit 22 that delays the received signal, and a frequency mixing circuit 27 that mixes the output of the delay circuit 22 and the output of the amplitude limiting circuit 26.

FIG. 4 is a block diagram of the selective amplification circuit 13. This selective amplification circuit 13 includes a bandpass filter 34 that extracts a carrier component from an input signal at a terminal 30, an amplifier 35 that amplifies the output signal of this bandpass filter 34, and a terminal 30.
The configuration includes a delay circuit 32 which branches and delays an input signal of 1 by a branch circuit 31, and a synthesis circuit 33 which synthesizes the output of this delay circuit 32 and the output of the amplifier 35.

Here, the delay circuit 22 of the random FM noise removal circuit 12 and the delay circuit 32 of the selective amplification circuit 13 have the configuration shown in FIG. That is, this delay circuit includes a frequency variable local oscillation circuit 45, a frequency mixing circuit 41 that converts the frequency of a terminal 400 Å power signal by the output of this local oscillation circuit 45, and a desired frequency (here) from the output of this frequency mixing circuit 41. A bandpass filter 42 that selects the SSB signal), a delay element 43 that delays the output of this bandpass filter 42, and a frequency mixer that converts the frequency by the output of this delay element 43 and the output of the local oscillator circuit 45. It includes a circuit 44 and a bandpass filter 47 for selecting a frequency equal to the input signal of the terminal 40 from the output of the frequency mixing circuit 45. Reference numeral 46 is local oscillator circuit 4
This is a branch circuit that branches one output.

In FIG. 3, in the random FM noise removal circuit 12,
A carrier wave component is extracted by a bandpass filter 25, and the amplitude of this carrier wave is limited by an amplitude limiting circuit 26, thereby creating a carrier wave whose phase is synchronized with the received signal and whose amplitude is stable and which eliminates the influence of propagation distortion. can be obtained.

This carrier wave is SSB.

The mixing circuit 27 mixes the signal as a carrier wave for signal demodulation.

When unnecessary wave components are removed by the bandpass filter 28, the resulting output signal becomes a signal that does not contain random FM noise. Furthermore, in the present invention, apart from such carrier wave extraction, a delay circuit 22 applies a delay to the SSB signal to be mixed with the carrier wave to match the phase with the carrier wave, and the delay circuit 22 is provided with a hetero gain as described above. Random FM noise is highly removed by using a conversion type delay circuit and by varying the local oscillation frequency for this heterodyne conversion to adaptively change the phase of the signal passing through the delay circuit 22.

In addition, in FIG. 4, the bandpass filter 34
By extracting the carrier wave included in the received signal, amplifying this carrier wave with the amplifier 35, and combining it with the received signal, it is possible to demodulate the SSB signal using a stable carrier wave. In this case, the SSB signal to be synthesized is delayed by the delay circuit 32 to match the phase with the carrier wave, and the delay circuit 32 is a heterodyne conversion type delay circuit as described above. By varying the local oscillation frequency for adaptively changing the phase of the signal that has passed through the delay circuit, it is possible to further improve the phase matching with the carrier wave.

Next, the operation of the random FM noise removal circuit 12 will be explained in more detail.

In FIG. 3, the SSB signal added with the carrier wave arriving at the input terminal 11 is expressed as 5t(t)=A+(t)cos(ωat-1(t)+φ
(t)). Here, A1(t) is an amplitude component contaminated by fading, ω. is the carrier angular frequency, ! (t
) is the angular frequency component of the information signal, φ(1) is the random FM
Each represents a noise component. The oscillation angular frequency of the local oscillation circuit 24 is ω. shall be. Signal 3 input from input terminal 11
1(t) is divided by a distributor 21, one is frequency-mixed with the output of the local oscillator circuit 24 by a frequency mixing circuit 23, and a band-pass filter for carrier wave extraction with a center angular frequency of (ω.-) is used. 25, the carrier component (ω.

-ω. ) is extracted and added to the amplitude limiting circuit 26, the output of the fundamental wave component is cos((ω0-ωG)(t-τI)+φ(-τ1)
). Here, r represents the delay time of the bandpass filter 25 for extracting the carrier wave. The other signal divided by the divider 21 is delayed by the delay circuit 22 by a time corresponding to the delay time τ1 of the bandpass filter 25 for extracting the carrier wave.
It is S, (t − r,) = A, (t − r,) cos (ω
e(t - rυ - sao ( -τ, ) + φ ( -τυ) This signal and the output of the amplitude limiting circuit 26 are frequency-mixed in the frequency mixing circuit 27 and passed through the band-pass filter 28 for unnecessary wave removal. When the spurious component is removed, A, (t-τ,)cos(ωo(t-τ1)-P(j-
τυ). As is clear from this, the signal appearing at the output terminal 29 has a random FM signal noise component φ(−τ
It can be seen that I) has been removed.

Next, the operation of the selective amplifier circuit will be explained.

SSB with carrier wave added at input terminal 30 in Figure 4
Since the random FM signal noise component of the signal has been removed by the random FM noise removal circuit 12 shown in FIG. 1, 32(t)=A2(t)CO3(ω.t−ψ(t))+
It can be expressed as Ao(t)cosωct. Here, A2(t)cos(ωct-1(t)) represents the SSB signal.

Ao(t)cosωct represents a carrier component. Further, A2(t) and Aa(t) represent respective amplitude components contaminated by fading. A carrier wave component is extracted from one signal obtained by dividing the terminal 300 input signal by a divider 31 by a band pass filter 34 for carrier wave extraction, and is amplified by an amplifier 35 with an amplification gain of G, and the output is Ao(t − r2) A signal Gcosωc(t−r2) is obtained. Here, τ2 represents the delay time of the bandpass filter 34 for extracting the carrier wave. When the other signal divided by the distributor 31 is delayed by the delay time τ2 in the delay circuit 32, it becomes A2(−τ2) cos(ωc(−τ2)−v(
−τ2))+AO(t−τ2) cosωc(−τ
2). When this is in-phase synthesized by the synthesizer 33, it becomes A2(t - r,)cos(a+c(t-r2)-!'
(t-r2))+Ao(t-r,)(1+G)cosω
c(t-r2). Here, always IA2(−τ2) l < l Ao(−τ2)(
1+G)! , this signal is a real zero point (Real
Zero) condition is satisfied. By accurately matching the delay time of the band-pass filter for extracting the carrier wave using the delay circuit 32, it is possible to prevent waveform deterioration during selective amplification.

Next, the operation of the delay circuit will be explained with reference to FIG.

A divider 46 divides the microwave band signal of angular frequency ω1±Δω input from the input terminal 40 and the output of the local oscillator circuit 45 of the oscillation angular frequency ω2, and one of the signals is divided into two and guided to the frequency mixing circuit 41. , frequency is converted and unnecessary waves are removed by bandpass filter 42, (ω, -ω2)
The signal becomes ±Δω. The oscillation angular frequency of the oscillation circuit 45 is selected so that the frequency is converted into the operating range of the delay element 43. The passband of the bandpass filter 42 for removing unnecessary waves is determined so that a signal of (ω1-ω2)±Δω can pass through. The signal delayed by the delay element 43 and the other output of the divider 46 are led to the frequency mixing circuit 44 for frequency conversion, and the output thereof is...

When unnecessary waves are removed by a bandpass filter 47, a delayed frequency is obtained.

ω1±Δω A signal is obtained at the signal output terminal 48.

In this embodiment, as the delay element 43, FI R (Fin
A digital filter was used.

When a FIR digital filter is used as a delay element, arbitrary amplitude and delay characteristics can be provided by changing the coefficients. This characteristic is useful for equalizing the delay characteristics of a bandpass filter for carrier extraction, which is a circuit component of a random FM noise removal circuit or a selective amplifier circuit.

Furthermore, a CCD (Charge Co., Ltd.) is used as a delay element.
upledDev 1ce), B B D (Bucke
A transfer device such as a t Burigage Device) can be used.

It is also possible to use a digital delay element in which an input signal is once A/D converted into a digital signal, this is stored in a semiconductor memory, and data read out from the memory again after a certain amplitude has elapsed is D/A converted. This circuit converts the frequency of the microwave band signal into the range where the delay element operates, delays it, and then converts the frequency back to the original frequency range using the output from the same oscillation circuit, so the frequency fluctuation of the oscillation circuit during frequency conversion is , they are canceled out during the frequency up and down process and are not affected at all.

By changing the output frequency of the oscillation circuit for frequency conversion, the phase of the output signal from the signal output terminal 48 can be changed. Since the phase rotation generated in the delay element 43 is determined by (ωy−ω2)τ2, it can be seen that the phase can be changed by changing the frequency ω2.

FIG. 6 shows a band-pass wave filter 25 for carrier extraction used in the random FM noise removal circuit 12 and the selective amplification circuit 13.
．． 34 is a block configuration diagram. The angular frequency ω input manually from the input terminal 50. One signal, which is divided into two by a divider 56 that distributes the carrier wave and the output of the local oscillation circuit 55 having the oscillation angular frequency ω3, is guided to the frequency mixing circuit 51 and frequency-converted. When the unnecessary waves are removed by the bandpass filter 52, (
The signal becomes ω0−ω, ). The oscillation frequency of the oscillation circuit 55 was selected so as to be frequency-converted to the operating range of the band-pass filter 53 for extracting the carrier wave. This bandpass filter 53 was composed of a dicicle filter. The passband of the bandpass filter 52 is determined so that a signal (ω.-ω3) can pass therethrough. The signal extracted by the bandpass filter 53 and the other output of the distributor 56 are guided to a frequency mixing circuit 54 for frequency conversion, and unnecessary waves are removed from the output by a bandpass filter 57. Its output has an angular frequency ω. A carrier wave of is obtained at the output terminal 58.

In this embodiment, an FIR digital filter is used as the bandpass filter 53 for carrier extraction.

When an FIR digital filter is used, its delay characteristics are flat within the passband, and sharp frequency selection characteristics can be obtained. In this circuit as well, the frequency of the microwave band signal is converted into the region in which the delay element operates and is delayed, and then the frequency is converted back to the original frequency region by the output from the same oscillation circuit, so the frequency fluctuation of the oscillation circuit during frequency conversion is , as in the case of a delay circuit, it is canceled out by the frequency up and down processes and is not affected at all.

FIG. 2 is a block diagram of main parts of an apparatus according to a second embodiment of the present invention. This device is a diversity receiving circuit with multiple receiving systems, and the SSB signals inputted from input terminals 11 to 11 are subjected to random FM noise removal using the output obtained by dividing the output of a common local oscillation circuit 24 by a divider 20. Due to phase distortion due to fading in circuits 12'a to 12n,
After some random FM noise is removed, a synthesis circuit 7 performs in-phase synthesis. In order to perform in-phase synthesis, it is necessary to adjust the phase of the signals from each branch, but the phase adjustment is achieved by adjusting the oscillation frequency of the local oscillator circuit 45, which is a component of the delay circuit 22 shown in FIG. It can be carried out. The carrier wave component of the in-phase combined signal is selectively amplified by the selective amplification circuit 13 so as to satisfy the real zero condition. In this way, the amplitude limiting circuit can be used even for SSB signals having amplitude information components.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain a high-quality demodulated signal from which random FM noise has been removed. Furthermore, the equal-gain combining diversity receiver configuration with multiple branches enables in-phase combining to sufficiently remove random noise, and the quality of the demodulated signal from the combined signal can sufficiently reduce click noise.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an SSB receiver according to a first embodiment of the present invention. FIG. 2 is a block diagram of main parts of a diversity reception SSB reception device using a plurality of reception systems according to a second embodiment of the present invention. FIG. 3 is a block diagram of a random FM noise removal circuit. FIG. 4 is a block diagram of the selective amplifier circuit. FIG. 5 is a block diagram of the delay circuit. FIG. 6 is a block diagram of a band-pass filter for extracting a carrier wave. 11... Input terminal, 12... Random FM noise removal circuit, 13... Selection amplifier circuit, 14... Output terminal,
20... Distributor, 21... Distributor, 22... Delay circuit, 23... Frequency mixing circuit, 24... Local oscillation circuit, 25... Band pass filter for carrier wave extraction, 26
... Amplitude limiting circuit, 27... Frequency mixing circuit, 28
...bandpass filter for unnecessary wave removal, 29...output terminal, 30...input terminal, 31...distributor, 32...
...Delay circuit, 33...Synthesizing circuit, 34...Band filter for carrier wave extraction, 35...Amplifier, 36...Output terminal, 40...Input terminal, 41...Frequency mixing Circuit, 42...Band pass filter for unnecessary wave removal, 43.
...Delay element, 44...Frequency mixing circuit, 45...
Local oscillator circuit, 46...Distributor, 47...Band pass filter for removing unnecessary waves, 48...Output terminal, 50...
- Input terminal, 51... Frequency mixing circuit, 52... Band pass filter for unnecessary wave removal, 53... Band pass filter for droplet transmission extraction, 54... Frequency mixing circuit, 55・
...Local oscillation circuit, 56...Distributor, 57...Band pass filter for removing unnecessary waves, 58...Output terminal. Patent Applicant Nippon Telegraph and Telephone Corporation Agent Patent Attorney Nao Takashi Ide - Case Box Example Reception Table 1 Figure 2 Mei 47L Example Part 2 Lancombe FM Company Removal Round Tower M 3 Mouth, Danji F 1m 'tl D % Fan 4 Figure i! L Enguchi bribery history 5 times, 1st job, 1st time, 1st time, 6th figure

Claims (1)

[Claims] 1. A receiving circuit (3) that receives an SSB signal to which a carrier wave is added, and a random FM noise removal circuit (12) through which a received signal obtained as an output of this receiving circuit passes. In the SSB receiver, the random FM noise removal circuit includes a frequency mixing circuit (23) that mixes a local oscillation signal with the received signal, and a bandpass filter (25) that extracts a carrier component from the output signal of the frequency mixing circuit. ), an amplitude limiting circuit (26) that limits the amplitude of the output signal of this bandpass filter, a delay circuit (22) that delays the received signal, an output of this delay circuit, and an output of the amplitude limiting circuit. The delay circuit (22) of the random FM noise removal circuit includes a frequency mixing circuit (27) for mixing
A variable frequency local oscillation circuit (45), a frequency mixing circuit (41) that converts the frequency of an input signal using the output of this local oscillation circuit, and a bandpass filter (41) that selects a desired frequency from the output of this frequency mixing circuit. 42), a delay element (43) that delays the output of this bandpass filter, a frequency mixing circuit (44) that converts the frequency by the output of this delay element and the output of the local oscillator circuit, and An SSB receiver comprising: a bandpass filter (47) for selecting a frequency equal to the input signal from the output. 2. The SSB receiver according to claim 1, comprising a selective amplification circuit (13) connected in cascade with the random FM noise removal circuit and through which the output signal passes, the selective amplification circuit comprising:
A bandpass filter (34) that extracts a carrier component from the output of the received signal, an amplifier (35) that amplifies the output signal of the bandpass filter, and a delay circuit that delays the output of the random FM noise removal circuit. (32), a synthesis circuit (33) that synthesizes this delay circuit output and the above amplifier output.
).