JP3931905B2 - Transmit / receive antenna device - Google Patents

Description

  The present invention relates to a transmission / reception shared antenna apparatus used for a portable terminal that performs satellite communication or ground communication.

  FIG. 4 shows a conventional transmitting / receiving antenna device for a portable terminal. In FIG. 4, reference numeral 1 denotes a four-wire winding helical antenna that operates in a circular polarization, and 2 denotes a four-wire reception helical antenna that similarly operates in a circular polarization. Reference numeral 3 denotes a distributor that feeds power to the transmitting helical antenna 1, and reference numeral 4 denotes a transmitter that includes a high-power amplifier that outputs a transmission signal. Reference numeral 5 denotes a synthesizer that synthesizes reception signals received by the reception helical antenna 2, and reference numeral 6 denotes a receiver composed of a low noise amplifier or the like.

  A transmission / reception operation in this conventional transmission / reception antenna apparatus will be described. The transmission signal of the transmission system is input to the distributor 3 after being subjected to unnecessary wave removal and high output amplification in the transmitter 4. This transmission signal is distributed into four signals having phase differences of 0 °, 90 °, 180 °, and 270 ° by the delay operation in the distributor 3 and is input to the 4-wire winding helical antenna 1. Here, the line lengths of the feeder lines from the four output terminals of the distributor 3 to the transmission helical antenna 1 are the same for all four lines, and the line lengths are the same for each antenna element of the transmission helical antenna 1. Length. If the wavelength of the transmission wave is λ1, each antenna element resonates at the transmission frequency by setting the length of each antenna element to λ1 / 4, 3λ1 / 4,... A polarization signal can be transmitted. The synthesizer 5 in the receiving system synthesizes the circularly polarized signals received by the four windings of the receiving helical antenna 2 with phase differences of 0 °, 90 °, 180 °, and 270 °. When the wavelength of the received wave is λ2, the length of each antenna element of the receiving helical antenna 2 is set to any one of λ2 / 4, 3λ2 / 4,. A circularly polarized signal can be received by combining with the above phase difference.

  Even if the transmission and reception frequencies are different, if the frequencies are close, a transmission / reception shared helical antenna having a gain in a band covering both transmission and reception bands can be configured. However, when the transmission / reception frequency is far away or when it is desired to optimize the gain in transmission / reception, two helical antennas are provided for transmission and reception respectively, and the length of the antenna element of each helical antenna is transmitted or It is necessary to set the physical dimensions to match the reception frequency.

  In recent years, various terrestrial cellular communication systems and satellite mobile phone systems using artificial satellites have been developed. Dual mode or multi-mode is used to communicate with multiple communication entities using a single mobile terminal. Mobile terminals have been developed. The frequency of the radio wave transmitted and received by the mobile terminal is individually determined by the communication system. For example, in the case of a mobile terminal communicating with two communication systems, antennas corresponding to four frequencies are required for transmitting and receiving. .

  As described above, in the conventional portable terminal antenna device, when the transmission and reception frequencies are separated or when the antenna gain is optimized, it is necessary to provide helical antennas for transmission and reception respectively. There was a problem that the terminal was enlarged. In addition, even in a portable terminal that performs transmission / reception to / from a plurality of communication systems, a plurality of helical antennas are required to transmit / receive to / from these communication systems, which similarly leads to an increase in the size of the portable terminal. There was a problem.

  The present invention has been made in order to solve the above-described problems, and provides a shared antenna device for a portable terminal configured by a helical antenna that is shared and used for a plurality of radio waves having different frequencies. is there.

  A transmission / reception shared antenna apparatus according to the present invention includes a helical antenna shared for transmission / reception, a capacitive element connected in series to a feed line to the helical antenna, and the feed line and the ground point on the helical antenna side of the capacitive element. A varactor diode connected between the varactor diode and a bias voltage switching means for switching a reverse bias voltage applied to the varactor diode between transmission and reception and switching a frequency band of a signal transmitted and received by the helical antenna. The cathode side is provided on the antenna element side of the helical antenna, and the bias voltage switching means supplies a reverse bias voltage via a resistor or coil provided on the cathode side of the varactor diode. Accordingly, the resonance frequency of the antenna can be changed by matching between the varactor diode and the helical antenna during transmission and reception, and the frequency characteristics of the antenna during transmission and reception can be improved.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a transmission / reception shared antenna apparatus according to Embodiment 1 of the present invention. 7 is a helical antenna shared in transmission and reception, and 8 is a varactor diode provided on a feed line to the helical antenna 7. The varactor diode 8 is provided for each antenna element of the helical antenna 7 and is connected in series with the antenna element side as a cathode. Reference numeral 9 denotes a first voltage input terminal, 10 denotes a second voltage input terminal, and 11 denotes a switch for switching between the voltage input terminal 9 and the voltage input terminal 10. A resistor 12 is connected to the cathode side of the varactor diode 8, and the other end of the resistor is connected to the switch 11. Reference numeral 13 denotes a resistor connected to the anode side of the varactor diode 8. Reference numeral 14 denotes a distribution synthesizer that feeds power to the helical antenna 7. Reference numeral 15 denotes a circulator. Reference numeral 16 denotes a transmitter including a high-power amplifier.

  The transmission signal is subjected to unnecessary wave removal and high output amplification by the transmitter 16 and input to the distribution synthesizer 14 via the circulator 15. The circulator 15 prevents the transmission signal from entering the receiver 17. The transmission signal is distributed by the distribution synthesizer 14 to the necessary number of power feeding signals in accordance with the number of antenna elements of the helical antenna 7 and fed to the helical antenna 7 through the power feeding line. In the case of FIG. 1, there are four distributions. On the other hand, the received signal from the helical antenna 7 is synthesized by the distribution synthesizer 14, input to the receiver 17 via the circulator 15, performs low noise amplification, etc., and is input to a signal processing unit or the like (not shown). The circulator 15 prevents the received signal from entering the transmitter 16.

  The transmission signal distributed by the distribution synthesizer 14 is fed to each antenna element of the helical antenna 7 via the varactor diode 8. A reverse bias voltage from the voltage input terminal 9 or the voltage input terminal 10 is applied between the anode and the cathode of the varactor diode 8 via the switch 11. The capacitor capacity of the varactor diode 8 changes according to the value of the reverse bias voltage. Since the resonance frequency of the helical antenna 7 is determined by the capacitor capacity of the varactor diode 8 and the electrical length of each antenna element of the helical antenna 7, the resonance frequency also changes when the capacitor capacity changes as described above. By applying different voltages from the voltage input terminal 9 and the voltage input terminal 10 and switching them by the switch 11, it is possible to configure an antenna that resonates at different frequencies in transmission and reception. For example, a reverse bias voltage is applied from the voltage input terminal 9 to the varactor diode 8 through the switch 11 at the transmission gate, and a reverse bias voltage is applied from the voltage input terminal 10 to the varactor diode 8 through the switch 11 at the reception gate. The switch 11 is switched so that At the time of this reception, similarly to the case of the above transmission, the resonance frequency received by this antenna is determined by the reverse bias voltage from the voltage input terminal 10 applied between the anode and the cathode of the varactor diode 8. The reception signal received by the helical antenna 7 is combined by the distribution synthesizer 14 and then input to the receiver 17 via the circulator 15.

  Here, the resistor 12 is provided to supply a reverse bias voltage to the varactor diode 8 and to sufficiently increase the impedance with respect to the impedance of the transmission line to reduce the signal loss. The resistor 13 is connected to the anode side in order to cause a potential difference between the anode and the cathode of the varactor diode 8 and to sufficiently increase the impedance with respect to the impedance of the transmission line to reduce the signal loss. Is provided.

  Although the resistor 12 and the resistor 13 are used in the voltage supply circuit for applying the reverse bias voltage to the varactor diode 8 in FIG. 1, these resistors may be replaced with coils. By using the coil in this manner, matching can be achieved between the voltage supply circuit and the anode ground circuit provided for bias application and each of the helical antenna elements, and the antenna radiation efficiency can be increased. The voltage supply circuit here is a circuit composed of the voltage input terminal 9, voltage input terminal 10, switch 11 and resistor 12 in FIG. 1, and the anode ground circuit is a circuit formed by the resistor 13. .

  FIG. 1 exemplifies the case where the helical antenna 7 has a four-wire winding. Even if the helical antenna 7 is a two-wire wound helical antenna, this embodiment can be similarly configured by the above circuit. . When a two-wire helical antenna is used, the number of antenna elements can be reduced, whereby the number of varactor diodes 8 connected to each antenna element can be reduced, and the antenna device can be downsized.

Embodiment 2. FIG.
FIG. 2 is a block diagram showing a configuration of a transmission / reception shared antenna apparatus according to Embodiment 2 of the present invention. In FIG. 2, reference numeral 18 denotes a distribution synthesizer having a delay circuit therein, and in the case of the figure, includes a delay circuit that generates phase differences of 0 °, 90 °, 180 °, and 270 °. In addition, the circuit which attached | subjected the same code | symbol as FIG. 1 in FIG. 2 shows the same or equivalent part of the circuit shown in FIG. 1 in Embodiment 1. FIG.

  The feature of this embodiment is that the transmission signal supplied to the helical antenna 7 is divided into four in the divider / combiner 18 as described above in order to form a circularly polarized wave, and 0 ° and 90 ° are divided into the four divided signals. , 180 °, and 270 °. Further, the received signal is characterized in that it is synthesized by the distribution synthesizer 18 via a delay circuit having a phase difference. When different frequencies are used in transmission and reception, if a circuit that gives such a phase difference is provided, for example, if a delay circuit in the distribution synthesizer 18 is provided in accordance with the frequency at the time of transmission, the frequency is different at the time of reception. The phases of the received signals are not aligned, and a phase error occurs in the received signal.

  In a helical antenna device that transmits and receives a circularly polarized signal, in order to reduce phase errors in transmission and reception on a delay circuit, a delay line that passes a transmission signal and a delay line that passes a reception signal in the distribution synthesizer 18 Can be provided separately. With this configuration, the delay circuit in the distribution synthesizer 18 becomes large, but the problem of phase error is solved.

  Further, when sharing a delay line through which a transmission / reception signal is passed so that the delay circuit in the distribution synthesizer 18 does not become large, the phase of the transmission / reception signal is made different by setting the reverse bias voltage applied to the varactor diode 8 to different values in each antenna element. The error can be reduced. The delay circuit in the distribution synthesizer 18 is shared in transmission and reception, and is constituted by a delay line whose phase difference after distribution with respect to one of the transmission and reception signals, for example, the transmission signal is 0 °, 90 °, 180 °, and 270 °. To do. Therefore, when the received signal is synthesized by this delay line, the frequency of the transmission / reception signal is different, so that the phases are not aligned. In order to correct this phase shift, the reverse bias voltages applied to the four varactor diodes 8 corresponding to the antenna elements of the helical antenna 7 are set to different values, and the capacitor capacities of the four varactor diodes 8 are respectively set. Use a different value. In the above example, since the delay circuit is provided so that the four phase differences are 0 °, 90 °, 180 °, and 270 ° during transmission, the reverse bias voltage during transmission, for example, the value of the power input terminal 9 is four. The varactor diode 8 is set to the same value. In order to correct the phase error during reception, the values of the four power input terminals 10 applied to the four varactor diodes 8 are set to different values.

  As described above, when the capacitor capacity of the varactor diode 8 is set to a different value for each antenna element of the helical antenna 8, the resonance frequency is slightly shifted. Compared to the case where a transmission signal and a reception signal having different frequencies are transmitted and received without changing the capacitor capacity of the varactor diode 8, the shift of the resonance frequency is made small.

Embodiment 3 FIG.
FIG. 3 is a block diagram showing a configuration of a transmission / reception shared antenna according to Embodiment 3 of the present invention. In FIG. 3, reference numeral 19 denotes a capacitive element connected in series with a feed line to the helical antenna 7. Reference numeral 20 denotes a varactor diode connected between the feeder line and the ground point on the helical antenna 7 side of the capacitive element 19. In addition, the circuit which attached | subjected the same code | symbol as FIG. 1 in FIG. 3 shows the same or equivalent part of the circuit shown in FIG. 1 in Embodiment 1. FIG.

  A reverse bias voltage from the voltage input terminal 9 and the voltage input terminal 10 is applied between the cathode and the anode of the varactor diode 20 via the switch 11. Due to this reverse bias voltage, the capacitor capacity of the varactor diode 20 changes, and the resonance frequency of the antenna changes due to matching between this capacitor capacity and each antenna element of the helical antenna 7, thereby changing the transmission frequency or the reception frequency. Can do.

It is a block diagram which shows the structure of the transmission / reception shared antenna apparatus which concerns on this invention (Embodiment 1). It is a block diagram which shows the structure of the transmission / reception shared antenna apparatus which concerns on this invention (Embodiment 2). It is a block diagram which shows the structure of the transmission / reception shared antenna apparatus which concerns on this invention (Embodiment 3). It is a block diagram which shows the structure of the conventional antenna apparatus.

Explanation of symbols

  7 Helical antenna, 8 Varactor diode, 9 First voltage input terminal, 10 Second voltage input terminal, 11 Switch, 12 Resistor, 13 Resistor, 14 Distribution synthesizer, 15 Circulator, 16 Transmitter, 17 Receiver , 18 Distributor / Synthesizer, 19 Capacitive element, 20 Varactor diode

Claims (1)

A helical antenna shared for transmission and reception, a distribution synthesizer that feeds power to the helical antenna, a capacitive element connected to a feed line between the distribution synthesizer and the helical antenna, and a helical antenna side of the capacitive element A varactor diode connected between the feed line and the ground point, and a reverse bias voltage applied to the varactor diode are switched during transmission and reception, and a frequency band of a signal transmitted and received by the helical antenna is switched. In the transmission / reception shared antenna apparatus comprising bias voltage switching means, the varactor diode is provided with its cathode side on the antenna element side of the helical antenna, and the bias voltage switching means is connected to the varactor diode. The reverse bias voltage is supplied through a resistor or coil provided on the cathode side. Both transmission and reception antenna device according to.

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