JP3188398B2 - Antenna with phase synthesizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna with a phase synthesizer having a plurality of antennas to obtain an optimum reception state in order to avoid the effects of fading. More specifically, it can be miniaturization suitable such vehicle-mounted, and relates to a phase synthesizer with an antenna capable of obtaining a large optimum reception state of sensitivity by combining signals received by a plurality of antennas.

[0002]

2. Description of the Related Art In a long-distance wireless transmission path, a large change in reception level generally occurs due to fading.
In particular, in the case of an on-vehicle antenna, the reflection of radio waves differs depending on the position of the vehicle and the like, and the influence is great. For this reason, the diversity of the reception level is prevented by using the diversity technique.

As shown in FIG. 5, a conventional in-vehicle TV antenna has a configuration in which several antennas are connected and switched to an antenna in an optimum receiving state. In FIG. 5, ANT1 to ANT4 are separate antennas respectively, 101 is an antenna switching unit, and an antenna switching signal 10
2 switches to the most suitable antenna. 103 is R
The RF signal received by the F signal amplifier is amplified and output from the antenna output terminal 104. Antenna switching signal 102
Is generated by noise detection of a video signal circuit or the like, and a switching signal to an optimum antenna is output according to noise of an actually received signal.

[0004] On the other hand, there is also known a diversity method of adjusting the phase between two antennas so as to reduce noise by combining received signals from the two antennas. However, the conventional diversity method of combining the received signals of two antennas combines the signals received by the antennas by directly performing signal processing such as phase modulation, and requires a large-scale apparatus for signal processing. Become. For this reason, it is good to use it for high frequency such as microwaves or for equipment fixed on the ground. However, it is suitable for antennas such as in-vehicle TV antennas whose frequency is as low as about 90 to 770 MHz and which is required to be small and inexpensive. Is not practical. In other words, the lower the frequency, the longer the wavelength, and the larger the quarter wavelength line normally used for phase adjustment. Therefore, it is not suitable for loading on a vehicle.

[0005]

As described above, in an on-vehicle antenna, the state of radio wave reflection changes greatly depending on the traveling place, and the antenna is particularly susceptible to fading.
For miniaturization required for automotive, as described above, in advance to provide a plurality of antennas with a quarter wavelength to 1/2-wavelength intervals of about digitally to the antenna optimum reception state Only the method of switching to can be adopted. However, in such a method in which individual antennas are digitally switched and used, an optimum reception state cannot be continuously obtained due to discontinuity at the time of switching. In addition, always 1
Because it can only receive the signal of the book antenna,
There is a problem that the received signal cannot be increased.

[0006] The present invention has been made in view of such circumstances, the frequency is relatively low and also in-vehicle TV antenna is required <br/> small-type, such as for automotive,
It is an object of the present invention to provide an antenna with a phase synthesizer capable of continuously receiving a signal received from an antenna in an optimal state and combining received signals from a plurality of antennas into a large received signal. Aim.

[0007]

SUMMARY OF THE INVENTION An antenna with a phase synthesizer according to the present invention includes a plurality of antennas, and combines signals received by the plurality of antennas to obtain a received signal in an optimum state. an apparatus with an antenna, each of the signals received by the plurality of antennas, the
Frequency higher than the frequency of the signal received by the antenna
In and mixed with the local signal for adjusting the phase
And a phase synthesizing device that adjusts the phases of the mixed outputs by up-conversion and synthesizes a signal with the adjusted phases. This upcon
Quarter-wavelength line to adjust phase by bart
Can be shortened, and phase shifters, etc. can be miniaturized.
Can be.

[0008] The phase synthesizing device may include a local oscillator, and a phase shifter configured to convert an output of the local oscillator into a plurality of local signals having a phase difference for eliminating a phase difference between signals received by the plurality of antennas. Mixers for mixing the respective local signals whose phases have been adjusted by the phase shifter and the signals received by the respective antennas, and respective outputs which have been mixed by the mixer and have the same phase with each other. And a synthesizer for synthesizing.

[0009]

When the antenna is a vehicle-mounted TV antenna, the phase shifter adjusts the phase of the local oscillator by a phase difference control signal generated based on noise detected from a video signal of a tuner section. Thus, the phase can be easily adjusted.

[0011]

Next, an antenna with a phase synthesizer according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a main part of an embodiment of an antenna with a phase synthesizer according to the present invention, and FIG.
And FIG. 3 is a block diagram of the tuner unit shown in FIG. 1.

The example shown in FIG. 1 shows an example in which the antennas are ANT1 and ANT2, and the interval is about 1/4 to 1/2 wavelength, that is, about 50 to 200 cm. Signals received by each of the antennas ANT1 and ANT2 are, for example, 90 to 77 in a VHF band or a UHF band.
A channel signal of a television in the range of 0 MHz,
As shown in A1 and A2, the waveforms have different phases and amplitudes due to differences in reflection conditions during propagation of radio waves (the amplitudes are written the same in FIG. 2). Antenna ANT
1 and ANT2 respectively receive signals from the first amplifying units 11 and 1 including low-noise amplifiers and filters.
2 are input to the first mixers 21 and 22, respectively. Although the first amplifying units 11 and 12 are shown in a simplified manner, they are amplified by a low noise amplifier to an appropriate amplitude by an auto gain control (AGC) from a not-shown control unit, and then the signal from the not-shown control unit is used. It is composed of an amplifier controlled by the control unit and several stages of amplifying units that amplify the signal through the filter, and amplifies only the necessary received signal. It has become. As shown in B1 and B2 of FIG. 2, the waveform of the amplified received signal has an increased amplitude, and the phase difference between the two remains as it is.

In the first mixers 21 and 22, the antenna A
By inputting and mixing a local signal of, for example, 2 GHz in addition to the signals received by NT1 and ANT2, the received signal is up-converted to 1.23 to 1.91 GHz, which is a difference signal from the local signal. The local signal has, for example, phases Φ1 and Φ2 in which the output of the first local oscillator 5 oscillated at a frequency of about 2 GHz cancels the phase difference between the signals received by the respective antennas ANT1 and ANT2 by the phase shifter 4. As a result, as shown in C1 and C2 in FIG. 2, a local signal whose phase is shifted to the opposite side to the received signal at a higher frequency than the received signal is obtained (in the example shown in FIG. 2, the phase of C1 is changed). Is the same as the phase of B1, and the phase of C2 is shifted to the opposite side of B2 so as to match the phase of B1.) The frequency of the first oscillator 5 is locked by a first PLL (not shown) in response to a command from a control unit (not shown). In the first mixers 21 and 22, the signals received and amplified by the antennas ANT1 and ANT2 and the phase-adjusted local signals are mixed, respectively, as shown in D1 and D2 in FIG. Thus, the frequency is lower than the frequency of the local oscillator 5, but is up-converted to a higher frequency than the received signal, and the respective signals have the same phase.

In this example, one phase of the phase-adjusted local signal is made coincident with one phase of the signal received by the antenna, and the phase of the other local signal is shifted by the phase difference of the received signal, so that both of them are shifted. Although the phases are matched, each phase after mixing matches the phase of the middle part of the phase difference of the signal received by each antenna, for example, half of the phase difference is shifted by both local oscillators The phases of the local oscillators may be adjusted as described above. In practice, the phases of both local signals are adjusted by the phase shifter 4 so that the noise of the video signal is reduced.

In the present invention, the phases of the signals received by the two antennas are matched by changing and mixing the phases of the local signals as described above. Therefore, the phase of the local signal may be adjusted to adjust the phase. . This phase adjustment is performed, for example, by changing, for example, the capacity of a hybrid ring formed in a pattern of １ ／ wavelength formed on a printed circuit board. Therefore, by increasing the frequency of the local signal, 1 /
4 wavelength line can be reduced, the phase shifter 4 can be greatly <br/> small-type. Further, by up-converting the received signal in this way, the fractional band (frequency band of the signal / frequency of the signal) is reduced, and noise is reduced. The range in which the frequency is increased is preferably in the range of about 1 to 2 GHz.

The phase-adjusted and frequency-converted received signal is mixed with the local signal to obtain a second signal.
Are amplified and filtered by the amplifying units 31 and 32, respectively, and become signals of only the converted frequency of 1.23 to 1.91 GHz. The second amplifying units 31 and 32 are also configured by a combination of several stages of amplifiers, like the first amplifying units 11 and 12 described above. The amplified signals are combined by the combiner 6. At this time, since the phases of the two signals are matched, the amplitude is increased as it is and the signals are combined to form a waveform as shown by E in FIG.

After that, the signal is again mixed with the signal of the local oscillator 5 by the second mixer 7 and returned to the original frequency in the received state. The waveform at that time returns from the frequency whose frequency has been up-converted to the original frequency as shown by F in FIG. That is, a composite wave of the signals received by the two antennas is output as a signal of the same frequency,
It is sent to the TV tuner section 8. With the configuration shown in FIG.
The components from the first amplifying units 11 and 12 to the second mixer 7 constitute the phase synthesizing device 1, and the phase synthesizing device 1 shown in FIG.
Are given the same reference numerals such as A1 and A2.

The TV tuner section 8 has, for example, a configuration as shown in FIG. That is, the tuner 81
And the second local oscillator 8
2 is mixed with the second local signal to generate an intermediate frequency signal, which is converted into an intermediate frequency signal of about 58 MHz, input to a video / audio separation circuit 83, processed, and outputs an AGC signal. Video (video) and audio (audio) signals are output. The frequency of the second local oscillator 82 is locked by the second PLL according to a command from a control unit (not shown) according to the frequency of the selected channel. In FIG. 3, the superimposer 84 is for displaying the level of a channel or volume on a television.

Further, based on the video signal of the video / audio separation circuit 83, noise of a synthesized wave due to a phase shift of each received signal is detected, and based on the detected noise, a phase shifter is passed through a control unit (not shown). The phase shifter 4 sends a phase difference control signal to the phase shifter 4 so as to eliminate noise. That is, as shown in an example of a circuit for detecting noise by synthesis in FIG. 4, a video signal is input to a noise detector 93 via a video buffer 91 and a video amplifier 92, and is detected based on the amplitude level of a detection signal of a noise level. The noise is switched by the switch 94 and held, and the microprocessor 97 passes through the peak hold 95 and the buffer 96 to generate a phase difference control signal together with the video signal through the video buffer 90 and the sync separator 99 for sync separation. The video signal is used as a video output via a video buffer 98.

In the above-described example, the number of antennas is two. However, three or more antennas may be used. In this case, the phase shifter 4 is configured so that the phase can be adjusted according to the number of antennas. By mixing the signal received by the antenna with the local signal, performing frequency conversion, and then combining the signals, a more reliable received signal can be obtained.

[0022]

According to the present invention, in the phase synthesizing apparatus, the phase is adjusted by mixing with the local signal, and the frequency is converted before being synthesized. Therefore, the phase adjustment of each received signal to be synthesized is performed. Can be performed by using a local signal, and the signals can be easily combined with matching phases.

Furthermore, by a frequency higher than the signal for receiving the local signal, for enabling the higher frequency phase adjustment, it can be further small-type phase shifter,
It can be synthesized signals received by the plurality of antennas even when downsizing, such as for vehicle is required. Further, the fractional band is reduced, and noise can be reduced. As a result, in-vehicle antenna with phase synthesizer,
The received signals of each antenna can be combined and received,
It is possible to perform high-sensitivity, low-noise, stable reception without causing discontinuity due to switching or large variations in sensitivity.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an antenna with a phase combining device according to the present invention.

FIG. 2 is a diagram showing a waveform of a received signal in each unit in FIG.

FIG. 3 is a diagram illustrating a configuration example of a tuner unit in FIG. 1;

FIG. 4 is a diagram illustrating a circuit example for detecting noise due to synthesis;

FIG. 5 is a diagram illustrating a configuration example of a conventional antenna with a phase synthesizer for mounting on a vehicle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Phase synthesizer 4 Phase shifter 5 Local oscillator 6 Synthesizer 8 Tuner part 11, 12 First amplifying part 21, 22 First mixer

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-17932 (JP, A) JP-A-63-136477 (JP, A) JP-A-2-159133 (JP, A) JP-A 8- 186527 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/00 H04B ⁷ /02-7/12 H04L 1/02-1/06

Claims (3)

(57) [Claims] 1. An antenna with a phase synthesizer comprising a plurality of antennas and combining signals received by the plurality of antennas to obtain an optimally received signal. Each signal obtained
At a frequency higher than the frequency of the signal received by the antenna,
In addition, it mixes with the local signal to adjust the phase and
An antenna with a phase synthesizer, comprising: a phase synthesizer that up- converts the mixed output to adjust the phases of the mixed outputs and synthesizes a signal with the adjusted phase. 2. A phase synthesizer comprising: a local oscillator; and a plurality of local signals having a phase difference for eliminating a phase difference between signals received by the plurality of antennas. A phase shifter, a mixer for mixing the local signal whose phase has been adjusted by the phase shifter and a signal received by each of the antennas, and a mixer which is mixed by the mixer and has the same phase as each other. 2. An antenna with a phase synthesizer according to claim 1, further comprising a synthesizer for synthesizing the output of the phase synthesizer. 3. The vehicle-mounted TV antenna according to claim 1, wherein
Claim 2 Symbol placement phase synthesizer with an antenna phase shifter adjusts the phase of the local oscillator by the phase difference control signal generated based on the noise detected from the video signal of the tuner section.