JPS62250729A - Diversity receiver - Google Patents

Abstract

PURPOSE:To secure the high quality communications and to substantially improve reliability by operating a switching means based on a control signal and transmitting a delay output from a delay circuit by blocking a signal from an A/D converting circuit. CONSTITUTION:If fading occurs in a time t1, a control circuit 5 discriminates a drop in gains in a signal reproduction part, and transmits the control signal to an antenna switching circuit 2 and the switching means 7. Due to the control signal the antenna switching circuit 2 is immediately switched to the side of an antenna 1B, and connects an output terminal from the antenna 1B to the signal reproduction part. On the other hand, when the switching means 7 inputs the control signal, it is switched to the side of the delay circuit 9 after a delay time tau3 elapses, blocks a signal input from the A/D converting circuit 6, and simultaneously transmits delay information from the delay circuit 9 to a D/A converting circuit 8. The switching means 7 maintains such a state for a time taub, then is restored and switched to the side of the A/D converting circuit 6. Thus a drop in gains, which arises at the time of switching the antenna, can be prevented.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention selectively switches and receives high frequency signals from a plurality of antenna elements to reduce the effects of fading.
The present invention relates to a diversity receiving device that ensures highly reliable communication.

(Prior Art) In wireless communications, various diversity receiving devices have been developed because fading impedes good quality communications. Among these, the so-called space diversity reception method, in which two or more antennas are installed and selectively switched for reception, is often used because of its simple circuit configuration. As a diversity receiving apparatus that employs such a space diversity receiving method, the one shown in FIG. 4 is known. In FIG. 4, IA and IB are antennas that receive the same radio wave, and are installed at a predetermined interval, for example, at a wavelength of the incoming radio wave. Also, antenna IAs
LB is connected to the antenna switching circuit 2. Here, as shown in FIG. 4, the antenna switching circuit 2 is switched to the antenna switching side, and only the received signal from the antenna IA is given to the signal regeneration section consisting of the RF/IF circuit 3 and the detection circuit 4, and the low Regenerated into a frequency signal. When fading occurs and the electric field strength of the antenna IA decreases, the control circuit 5
detects a decrease in the output from the RF/IF circuit 3, sends a control signal to the antenna switching circuit 2, switches the antenna switching circuit 2 to the antenna switching side, and supplies the signal received by the antenna LB to the signal regeneration unit to prevent fading. We are trying to reduce the impact of

(Problem to be solved by the invention) However, the electric field strength of the antenna that receives high-frequency signals is extremely low, and since the antenna output itself at such a low level is directly switched, the received signal may be instantaneous when switching the antenna. This causes noise in the demodulated output. Furthermore, the higher the frequency of antenna switching, the greater the influence of switching noise associated with antenna switching.

Furthermore, if the received field strength of all antennas IAflB as a diversity branch decreases below the set value,
There is a problem in that a so-called hunting phenomenon occurs in which the antenna switching circuit 2 continuously switches, making it impossible to ensure a high-quality communication state.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and is intended to prevent a decrease in receiving sensitivity due to noise generated when switching antennas,
It is an object of the present invention to provide a diversity receiving device that can ensure highly reliable communication.

(Means for Solving the Problems) In order to solve the above-mentioned problems and achieve the above objects, the present invention selectively receives high-frequency signals from a plurality of antenna elements using an antenna switching circuit, and converts the high-frequency signals into A diversity receiving device that regenerates a low frequency signal in a signal regenerator includes a control circuit that determines an antenna reception M state based on an output from the signal regenerator and outputs a control signal according to the determination result, and a signal regenerator. an A/D conversion circuit that converts a reproduced signal from the A/D conversion circuit into a digital signal; and a delay circuit that delays the analog signal by a predetermined delay time 1d, and operates the switching means based on the control signal from the control circuit, so that the A/
The delay output from the delay circuit is sent to the D/input conversion circuit while blocking the signal from the D conversion circuit.

(Example) Embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram illustrating an embodiment of the present invention using a receiving apparatus for FM reception as an example. First, the configuration will be described. IA and IB are antennas, and the antennas IA and IB are installed at a predetermined interval, for example, at an interval of the wavelength of the incoming radio wave. The output end of each antenna LA, IB is connected to an antenna switching circuit 2, and the high frequency signal received by the antenna IA*IB is selected by a switching operation of the antenna switching circuit 2 based on a command from a control circuit, which will be explained later. The high frequency signal selected in this way is sent to the signal reproducing section, the RF
- It is given to the IP' circuit 3 and the detection circuit 4, and is regenerated into a low frequency signal. To explain the configuration of the signal reproducing section in detail, first, the RF/engineering circuit 3 has a built-in high frequency amplification circuit that amplifies the high frequency signal from the antenna and a local oscillator that oscillates at a predetermined frequency. The amplified signal high-frequency amplified by the circuit and the local oscillation signal from the local oscillator are heterodyne detected, and the difference frequency is used as a beat to form an intermediate frequency signal. In addition, the detection circuit 4
- Contains an amplitude limiter and a discriminator that adjust the amplitude of the intermediate frequency signal from the IF circuit 3 to a constant amplitude, and outputs a signal proportional to the frequency deviation from a preset center frequency. The low frequency signal is extracted from the intermediate frequency signal. Reference numeral 5 denotes a control circuit for determining the antenna reception state, in which a predetermined threshold value is set in advance, and when the output from the RF/IF circuit 3, for example, the limiter current value, falls below the threshold value, a control signal is transmitted to the antenna switching circuit. 2 and switching means 7.

6 is a signal reproducing unit, that is, an A/D conversion circuit that converts the reproduced signal from the detection circuit 4 into a digital signal;
A signal from the D conversion circuit 6 is applied to a D/A conversion circuit 8 and a delay circuit 9 via a switching means 7. Here, the switching means 7 is normally set to A as shown in FIG.
/ It is connected to the D conversion circuit 6 side, and when the control signal from the control circuit 5 is input, the RF/I
After the signal delay time τ due to the F circuit 3, the detection circuit 4, and the A/D conversion circuit 6 has elapsed, the signal is switched to the delay circuit 9 side, and after a predetermined time τb has elapsed, it is restored. The value of the time τb held on the side of the delay circuit 9 is set to be greater than or equal to the maximum duration rn of the noise generated due to the switching operation of the antenna switching circuit 201 times. Further, the value of the delay time τd by the delay circuit 9 is set to be greater than the time τb. D from D/A conversion circuit 8
/A converted analog information is sent to another device, such as a sounder.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIG. Assuming that fading occurs at time t as shown in FIG.
and sends it to the switching means 7. The antenna switching circuit 2 is immediately activated by a control signal from the control circuit 5, switches to the antenna element side, and connects the output end from the antenna IB to the signal reproducing section. On the other hand, when the switching means 7 receives the control signal from the control circuit 5, it switches to the delay circuit 9 side after the delay time τ has elapsed, and the A/D conversion circuit 6 switches to the delay circuit 9 side.
At the same time, the delay information from the delay circuit 9, that is, the past information from the antenna IA, is cut off from the signal input from the antenna IA.
The signal is sent to the A conversion circuit 8. The switching means 7 maintains this state for a time τb, and after a time τ5 has elapsed, it recovers and switches to the A/D conversion circuit 6 side again. Therefore, as shown in FIG. 2, the D/A conversion circuit 8 receives past information from the antenna IA from time t2 to time t, and receives current information from the antenna IB after time t.
Send to.

In the embodiment shown in FIG. 1, the control circuit 5 is an RF-IF
Although the antenna reception state is determined based on the signal output from the circuit 3, the reception state may be determined based on the signal output from an appropriate signal reproducing section, for example, the detection circuit 4. Good too.

FIG. 3 is a block diagram showing another embodiment of the present invention using a receiving apparatus for AM reception as an example. In the embodiment shown in FIG. 3, an automatic gain adjustment circuit incorporated in the detection circuit 4,
The present invention is characterized in that an AGC voltage from a so-called AGC circuit is applied to the control circuit 5, and the antenna reception state is determined based on the AGC voltage from the detection circuit 4.

In the embodiments shown in FIGS. 1 and 3, two antenna elements are used as the diversity branch. However, the present invention is not limited to this, and the present invention is not limited to this. This also applies when using an appropriate number of antenna elements.

(Effects of the Invention) As explained above, according to the present invention, high frequency signals from a plurality of antenna elements are selectively received by an antenna switching circuit, and this high frequency signal is regenerated into a low frequency signal by a signal reproducing section. The receiving device includes a control circuit that determines the antenna reception state based on the output from the signal reproducing section and outputs a control signal according to the determination result, and an A/D that performs A/D conversion of the reproduced signal from the signal reproducing section. A conversion circuit, a D/A conversion circuit that inputs a signal from this A/D conversion circuit via a switching means and converts the signal into D/A, and a delay circuit that delays a predetermined delay time τd, and controls The switching means is activated based on a control signal from the circuit, and the delayed output from the delay circuit is transferred to the D/A converter circuit while blocking the signal from the A/D converter circuit for a time r1:l shorter than the time 7d. This has the effect of preventing the reception gain from decreasing due to noise generated when switching antennas, ensuring high quality communication, and greatly improving the reliability of the diversity receiver. It will be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a timing chart showing the operation of FIG. 1, FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG. The figure is a block diagram showing a conventional example. LAslB...Antenna, 2...Antenna switching circuit, 3...RF/IF circuit, 4...Detection circuit, 5...
- Control circuit, 6... A/D conversion circuit, 7... Switching means, 8... D/A conversion circuit, 9... Delay circuit. Patent Applicant Toyo Tsushinki Co., Ltd. Agent Patent Attorney Shinsuke Honjo Figure 1: *Information about the clause; 1, 13 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] A diversity receiving device in which high frequency signals from a plurality of antenna elements are selectively received by an antenna switching circuit, and the high frequency signals are regenerated into low frequency signals by a signal reproducing section, comprising the steps of: a control circuit that determines the antenna reception state based on the output and outputs a switching control signal for the switching circuit according to the determination result; and an A/D conversion circuit that converts the reproduced signal from the signal reproducing section into a digital signal. , said A/
a D/A conversion circuit that inputs a signal from the D conversion circuit via a switching means and converts the signal into an analog signal;
a delay circuit that delays the digital signal by a predetermined delay time ^τd, the switching means operates based on the control signal from the control circuit, and the switching means is operated based on the control signal from the control circuit to delay the digital signal by a predetermined delay time ^τd.
1. A diversity receiving device characterized in that the signal from the A/D conversion circuit is cut off only during the period b, and a delayed output from the delay circuit is sent to the D/A conversion circuit.