JPH08163016A - Diversity receiver - Google Patents

Abstract

PURPOSE: To always obtain the best reception state by continuously controlling a threshold level of antenna switching corresponding to a reception electric field strength and an antenna in use. CONSTITUTION: When a reception electric field strength is strong, the antenna switching threshold level is controlled the same and a threshold level used to switch a main antenna 11a into a sub antenna 11b is controlled higher as the reception electric field strength gets weaker, and conversely the threshold level switching the sub antenna 11b into the main antenna 11a is controlled lower. Furthermore, the switching from the sub antenna 11b to the main antenna 11a is controlled at all times to obtain a weaker reception electric field strength with respect to the reception electric field strength stopping the changeover device from the main antenna 11a to the sub antenna.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an in-vehicle television (T
V) Used for a receiver, in-vehicle AM / FM receiver, etc., switch to the other antenna when the reception condition deteriorates, and
The present invention relates to a diversity receiving apparatus that fixes to a main antenna and receives when the received electric field strength is below a certain level.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing the configuration of a conventional diversity receiver. In FIG. 3, this example is
Main and sub antennas 1a and 1b and this antenna 1
An antenna switch 2 for switching between a and 1b and a receiver 3 such as a TV receiver and an AM / FM receiver are provided. Furthermore, the reception state (noise generation state, S / N ratio) at the antenna (one of 1a and 1b) currently selected by the antenna switching device 2 from the detection output of the receiver 3 is compared with a threshold value, If it is less than the threshold value (deterioration of reception status),
The reception state detection circuit 4 that outputs the detection signal and the reception electric field strength at the antenna (one of 1a and 1b) currently selected by the antenna switching device 2 based on the detection output of the receiver 3 have a constant level (dB). When the weak electric field detection circuit 5 that outputs a detection signal in the following cases and the detection signal from the reception state detection circuit 4 are input, the currently selected antenna (1a,
The antenna switching device 2 sends a control signal for switching 1)
Switching control circuit 6 for transmitting a control signal for the antenna switching unit 2 to select the main antenna 1a when the detection signal from the weak electric field detection circuit 5 is input.
Is provided.

Regarding the conventional example constructed as described above,
The operation will be described below. FIG. 4 shows the antenna 1
It is a figure which shows the operation state of switching of a and 1b. 3 and 4, the receiver 3 operates with a received signal from the antenna (one of 1a and 1b) currently selected by the antenna switching unit 2. The receiver 3 sends a detection signal or the like resulting from this operation to the reception state detection circuit 4 and the weak electric field detection circuit 5. The reception state detection circuit 4 compares the reception state (noise generation state, S / N ratio) at the antenna (one of 1a and 1b) currently selected by the antenna switching unit 2 from the detected signal with a threshold value. Then, when the reception condition deteriorates below the threshold value, the detection signal is output to the switching control circuit 6. The weak electric field detection circuit 5 outputs the detection signal to the switching control circuit 6 when the received electric field strength at the antenna (one of 1a and 1b) currently selected by the antenna switch 2 from the detection signal is below a certain level. To do. The switching control circuit 6 receives the detection signal from the reception state detection circuit 4, that is, when the reception state deteriorates (the S / N ratio deteriorates), the antenna 1a currently selected by the antenna switching unit 2a. , 1b is sent from one of the antennas 1a and 1b to the other to reselect the antennas 1a and 1b. In addition, the switching control circuit 6 receives the detection signal from the weak electric field detection circuit 5, that is, the currently selected antenna 1a,
When the received electric field strength of one of the antennas 1b is below a certain level, a control signal for the antenna switching unit 2 to select the main antenna 1a is sent and fixed to the reception by the main antenna 1a.

As described above, in the diversity receiving apparatus of the conventional example described above, when the reception state deteriorates (the S / N ratio deteriorates), one of the currently selected antennas 1a and 1b is switched to the other and the current selection is made. Antenna 1
When the received electric field strength of one of a and 1b is below a certain level, the reception is fixed to the main antenna 1a to prevent its malfunction.

[0005]

However, in the diversity receiver of the conventional example, when the threshold value for switching the antennas 1a and 1b is set to a value (dB) having a strong electric field strength, the antennas 1a and 1b are sensitive to each other. Due to the difference, the electric field strength at the time of actual reception is weak, and the electric field strength is switched to be fixed to the main antenna 1a. When the antennas 1a and 1b are switched in the vicinity of the threshold value,
The reception condition deteriorates. Further, the reception state may be better when switched to the antenna 1b than when it is fixed to the main antenna 1a. That is, always
There is a drawback that good diversity reception cannot be performed.

The present invention solves such a conventional problem, and the threshold value for antenna switching can be continuously controlled in accordance with the received electric field strength and the antenna used, so that the best diversity reception state is always obtained. It is an object of the present invention to provide an excellent diversity receiver that can be obtained.

[0007]

In order to achieve the above object, a diversity receiver according to a first aspect of the present invention comprises a first antenna, a second antenna having a lower sensitivity than the first antenna, and a first antenna. , A switching means for switching the second antenna, an electric field strength detecting means for outputting a detection signal indicating an electric field strength based on a received signal from the switching means, and a first and a second antenna selected by the switching means. One of the first and second antennas is controlled by controlling the switching means on the basis of the reception state detection means for detecting one of the reception states, the electric field strength detection signal from the electric field strength detection means and the reception state detection signal from the reception state detection means. A control means for performing control for selecting the first antenna and a used antenna detection means for detecting the first or second antenna currently selected by the switching means, and when the detected received electric field strength is strong, the first antenna The threshold value for switching from the second antenna to the second antenna and the threshold value for switching from the second antenna to the first antenna are controlled to be the same, and as the received electric field strength weakens, the second antenna changes from the first antenna to the second antenna. Received electric field strength that controls the threshold value for switching to the antenna to be high, conversely controls the threshold value to switch from the second antenna to the first antenna to be low, and stops switching from the first antenna to the sub antenna On the other hand, the configuration is such that switching from the second antenna to the first antenna is always performed and control is performed so that the received electric field strength becomes weak.

The diversity receiver according to claim 2 is
The electric field strength detection means detects at least an intermediate frequency signal obtained by high frequency amplification and frequency conversion of the received signal from the switching means, and outputs this signal level as a detection signal indicating electric field strength, and the reception state detection means switches An intermediate frequency signal obtained by at least high-frequency amplifying and frequency-converting the received signal from the means is detected, and the signal-to-noise ratio of this signal is output as a detection signal indicating the reception state.

[0009]

With such a configuration, the diversity receiving apparatus according to claims 1 and 2 controls the threshold value for switching from the first antenna to the second antenna to be higher as the received electric field strength becomes weaker, and conversely. The threshold value for switching from the second antenna to the first antenna is controlled to be low. In addition, with respect to the received electric field strength at which the switching from the first antenna to the sub antenna is stopped,
Switching to the antenna is always performed so that the received electric field strength is weakened. Therefore, the threshold value for antenna switching is continuously controlled according to the received electric field strength and the antenna used, and the threshold value for antenna switching at each received electric field strength becomes the best and the best diversity reception state is always obtained. Like

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a diversity receiver of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the diversity receiving apparatus of the present invention. In FIG. 1, in this example, a main antenna 11a and a sub-antenna 11b which is inferior to the main antenna 11a in sensitivity are shown.
And the antenna switching device 12 for switching between the main antenna 11a and the sub antenna 11b, the TV receiver, and the AM / AM /
A receiver 13 such as an FM receiver is provided. This receiver 13 is a so-called super-heterodyne system that performs high frequency amplification, frequency conversion and intermediate frequency amplification processing.
Further, from the detection output of the receiver 13 or the like, the reception state at the main antenna 11a or the sub-antenna 11b currently selected by the antenna switching unit 12 (noise generation state, S / S
The N ratio) is compared with a threshold value, and when it is equal to or lower than the threshold value (deterioration of the reception state), the reception state detection circuit 14 that outputs the detection signal, and the detection output of the receiver 13 are used to detect the antenna switch 12 A weak electric field detection circuit 15 is provided which outputs a detection signal when the received electric field intensity at the currently selected main antenna 11a or sub-antenna 11b is below a certain level. Further, when a detection signal from the reception state detection circuit 14 is input, a control signal for switching the currently selected main antenna 11a or sub-antenna 11b is sent to the antenna switching device 12, and the weak electric field detection circuit 1
When the detection signal from 5 is input, the main antenna 1
A switching control circuit 16 which sends a control signal for the antenna switching device 12 to select and fix 1a, and the main antenna 11 which is currently being received from the used antenna detection circuit 18.
a or the main antenna 11 depending on the level of the detection signal of the sub antenna 11b and the output signal of the weak electric field detection circuit 15.
threshold control circuit 17 for controlling the threshold value for switching a or sub antenna 11b, and switching control circuit 1
A used antenna detection circuit 18 for detecting one of the main antenna 11a or the sub antenna 11b currently selected from the switching state of No. 6 is provided.

Regarding the embodiment configured as described above,
The operation will be described below. The receiver 13 uses the main antenna 11 currently selected by the antenna switching device 12.
It operates by the received signal from a or the sub antenna 11b.
The receiver 13 outputs a detection signal and the like resulting from this operation to the reception state detection circuit 14 and the weak electric field detection circuit 15. The detection signal from the used antenna detection circuit 18 indicating one of the main antenna 11a or the sub antenna 11b currently selected from the switching state of the switching control circuit 16 and the received electric field strength output from the weak electric field detection circuit 15 are constant levels. Depending on the level of the detection signal indicating the following case, the threshold control circuit 17 causes the main antenna 11a or the sub antenna 11 to operate.
Determine the threshold for switching b. Switching control circuit 16
Compares the detection signal from the reception state detection circuit 14 with the threshold value determined above, and when the reception state (S / N ratio) deteriorates, the main antenna 11a and the sub antenna 11
The switching of b is determined, and one of the main antenna 11a and the sub antenna 11b is switched through the control signal of the switching control circuit 16.

FIG. 2 is a diagram showing the relationship between the received electric field strength and the switching threshold value. In FIG. 1 and FIG. 2, when the received electric field strength received is relatively strong, the threshold for switching from the main antenna 11a to the sub antenna 11b and the threshold for switching from the sub antenna 11b to the main antenna 11a are set. The threshold value control circuit 17 performs the same setting control. As the electric field strength becomes weaker, the threshold value for switching from the main antenna 11a to the sub antenna 11b set by the threshold value control circuit 17 is increased. Conversely, from the sub antenna 11b to the main antenna 11
Lower the threshold value for switching to a. Further, the reception electric field strength point a at which the switching from the main antenna 11a to the sub antenna 11b is stopped by the control of the switching control circuit 16
For the sub-antenna 11b to the main antenna 11
The reception electric field strength point b, which is constantly switched to a, is set weak. Thus, when the received electric field strength at the main antenna 11a and the sub antenna 11b is weak, the difference in S / N ratio caused by the difference in sensitivity between the antennas can be absorbed.

As described above, in this embodiment, the threshold value for antenna switching is continuously changed as the received electric field strength becomes weaker in accordance with the antenna used, and the reception state is changed when the antenna is switched at a weak electric field strength. Can be prevented from getting worse. Also, diversity reception becomes possible even with a weaker electric field strength than in the past.

[0015]

As is apparent from the above description, according to the diversity receiving apparatus of claims 1 and 2, the threshold value for switching from the first antenna to the second antenna as the received electric field strength becomes weaker. Is controlled to be high, and conversely, the threshold for switching from the second antenna to the first antenna is controlled to be low, and the second electric field strength with respect to the received electric field strength at which switching from the first antenna to the sub antenna is stopped The antenna is always switched from the first antenna to the first antenna. Since the control is performed so that the received electric field strength is weakened, the threshold for antenna switching is continuous according to the received electric field strength and the antenna used. Controlled, and always has the best diversity reception condition.

[Brief description of drawings]

FIG. 1 is a block diagram of a diversity receiver according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a received electric field strength and a switching threshold value in the same embodiment.

FIG. 3 is a block diagram of a conventional diversity receiver.

FIG. 4 is a characteristic diagram showing a relationship between a received electric field strength and a switching threshold value in the conventional example.

[Explanation of symbols]

 11a Main antenna 11b Sub antenna 12 Antenna switching device 13 Receiver 14 Reception state detection circuit 15 Weak electric field detection circuit 16 Switching control circuit 17 Threshold control circuit 18 Used antenna detection circuit

Claims (2)

[Claims] 1. A first antenna, a second antenna having a lower sensitivity than the first antenna, a switching means for switching between the first and second antennas, and a received signal from the switching means. An electric field intensity detecting means for outputting a detection signal indicating an electric field intensity, a receiving state detecting means for detecting a receiving state of one of the first and second antennas selected by the switching means, and the electric field intensity detecting means. A control means for controlling the switching means on the basis of the electric field strength detection signal from the receiver and the reception status detection signal from the reception status detecting means to select the first and second antennas; and the switching means. A used antenna detection means for detecting the currently selected first or second antenna, and a threshold value for switching from the first antenna to the second antenna when the detected received electric field strength is strong. , While controlling the same threshold value for switching from the second antenna to the first antenna,
As the reception electric field strength becomes weaker, the threshold value for switching from the first antenna to the second antenna is controlled to be higher, and conversely, the threshold value for switching from the second antenna to the first antenna is controlled to be lower, and For the received electric field strength that stops switching from the first antenna to the sub-antenna, the second
The diversity receiving apparatus is characterized in that switching from the antenna to the first antenna is always performed, and control is performed so that the received electric field strength becomes weak. 2. The electric field strength detection means detects an intermediate frequency signal obtained by at least high frequency amplification and frequency conversion of the received signal from the switching means, and outputs the signal level as a detection signal indicating the electric field strength, and the received signal is received. The state detecting means detects an intermediate frequency signal obtained by at least high-frequency amplifying and frequency-converting the received signal from the switching means, and outputs a signal-to-noise ratio of this signal as a detection signal indicating a receiving state. Item 1. The diversity receiver according to item 1.