JPH03254205A - Diversity receiver for automobile - Google Patents

Abstract

PURPOSE:To attain diversity reception capable of using a conventional receiver by providing two antenna conductors or over to a window glass face and a changeover switch selecting one of plural reception RF signals from the antenna conductors. CONSTITUTION:A defrost heater wire 2 is provided onto a rear window glass 1 of an automobile and 1st and 2nd FM reception antenna conductors 3, 4 comprising an inverted-T shaped element and a horizontal simple element are provided to upper and lower space areas. The 1st and 2nd antenna conductors 3, 4 are arranged in close to the heater wire 2 and used for an AM reception antenna. The power is received from the heater wire 2. The antenna conductors 3, 4 are coupled with active matching circuits 20, 21 and respective reception outputs 20S, 21S are fed to a changeover switch 23 of a diversity reception circuit 22 provided onto the window glass face. The changeover switch 23 selects an excellent signal in the signals 20S, 21S according to a control signal 24S from a switching control circuit 24 and introduces a selection output to a transmission cable 13. Thus, the constitution of the automobile reception system is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a diversity receiving device for an automobile that uses a plurality of antenna conductors provided on a window glass surface.

[Conventional technology]

In-vehicle AM by attaching an antenna conductor to the car window glass
Window glass antennas are known that supply received signals to radio receivers, FM radio receivers, television receivers, and the like. In a reception system using such a window glass antenna, in order to prevent the quality of the received radio waves supplied to the in-vehicle receiver from deteriorating when the reception condition changes as the car moves, Diversity reception methods have come into use.

This requires a detection circuit and a comparison circuit for detecting the level, distortion, etc.

Therefore, a special receiver that incorporates these diversity receiving circuits must be used.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide a diversity receiving device that requires only one transmission cable between the antenna conductor and the receiver, and therefore allows the use of a normal receiver.

[Problem to be solved by the invention]

In the diversity reception method, two or more antenna conductors are installed on the window glass surface, and the receiver compares the carrier level, distortion amount, noise level, etc. of the received signal from each antenna to find the best quality reception. Select a signal and perform demodulation. Therefore, it is necessary to wire the same number of signal transmission cables between the window glass and the receiver as there are antenna conductors provided on the window glass (generally, the rear window glass), which is one of the causes of high costs.

In addition, since the receiver includes a switching circuit for received signals and a switching control signal by discriminating good received signals, the automotive diversity receiving device of the present invention has a plurality of antenna conductors and a switching control signal. , and a diversity receiving circuit for selecting the one with the best quality among a plurality of received signals from each antenna conductor is provided on the window glass surface, and the diversity receiving circuit generates a switching control signal based on the received RF multiplied signal. and a changeover switch that selects one of the plurality of received RF signals from the antenna conductor in accordance with the changeover control signal.

[Effect]

The received signals of the plurality of antenna conductors are selected into one output on the glass surface and guided to the receiver through one transmission cable. Therefore, no special receiver is required. The diversity receiving circuit on the glass surface is
Since the outputs of the plurality of antenna conductors are switched based on the carrier level of the received RF signal, etc., the circuit configuration can be made relatively simple.

〔Example〕

FIG. 1 shows a car reception system to which the present invention is applied.

In FIG. 1, a defogging heater wire 2 is provided on a rear window glass 1 of an automobile, and first and second FMs consisting of an inverted T-shaped element and a horizontal single element are installed in the upper and lower margin areas of the defogging heater wire 2.
A receiving antenna conductor 3.4 is provided. The first and second antenna conductors 3.4 are arranged close to the heater wire 2 and receive received power from the heater wire 2. The shapes and installation locations of these two antennas are not particularly limited.

The heater wA2 is divided into two groups, upper and lower, each group has a bus bar 5.6 at one end, a common bus bar 7 at the other end, and is fed in a folded manner.

A high-frequency choke coil 1O111 that is antimagnetically coupled is inserted into a power supply line 8.9 connected to the bus bar 4.5.

These choke coils 10, 11 have high impedance in the RF band, and prevent the power received by the heater wire 2 as an antenna from escaping to the power supply side and the ground side.

The FM antenna conductor 3.4 is connected to the hybrid C12 for diversity reception provided on the glass surface, and the best receiving output of these two antenna conductors 3.4 is selected in the hybrid IC12. be done. The selected received signal is sent to the transmission cable 1 such as coaxial
3 to an FM radio receiver 14 on the driver's side of the vehicle.

The heater wire 2 is used as an AM reception antenna, and its received power is led out to the transmission cable 13 from a coupling wire 15 connected to the motherboard 15 via an impedance matching circuit in the hybrid IC 12.

The reason why the hybrid IC is arranged on the glass surface is to reduce the number of cables between the antenna conductor 3.4 on the rear window glass 1 and the receiver 14. A matching circuit is also provided within the hybrid IC 12 to reduce power loss due to impedance mismatch between the antenna conductor 3.4 and the transmission cable 13.

As shown in FIG.
, 215 are supplied to the changeover switch 23 of the diversity receiving circuit 22 via these matching circuits 20 and 21. The changeover switch 23 selects the better one of the signals 203 and 21S according to the control signal 24S from the changeover control circuit 24, and outputs the selected output to the transmission cable 13.

On the other hand, the AM reception signal of the heater wire 2 is received by the hybrid IC 1.
The signal is supplied to an impedance matching (IM) circuit 25 in 2. The output of the matching circuit 25 is the transmission cable 1
3 and transmitted to the receiver@14 together with the FM reception signal.

On the other hand, the receiver 14 has a local oscillator for tuning, and a DC control voltage is applied to a variable capacitance diode or the like that makes the oscillation frequency variable according to a tuning operation. This DC control voltage E is supplied from the antenna input terminal of the receiver 14 through a sufficiently large impedance element in terms of high frequency to the hybrid IC 12 on the window glass l via the cable 3.

The active matching circuits 20 and 21 in the IC 12 have, for example, a series or parallel LC resonant circuit, the capacitance elements of which are comprised of variable capacitance diodes, the capacitance values of which are controlled by the DC control voltage E.

Thereby, the resonant frequency of the resonant circuit is controlled to correspond to the frequency tuned in the receiver 14. At this time, regarding the received signal during tuning from antenna conductor 3.4,
The resonant circuit is capacitive or inductive, so that the active matching circuit 20.21 operates to cancel the reactance of the antenna conductor 3.4 and improve the matching with the subsequent receiving circuit.

Figure 3 shows the antenna switching control circuit 24 and the switching switch 2.
3 is a block diagram showing the configuration of the second
An exposed antenna switching signal is formed in the received signal 2O3, 213 which is the output of the active matching circuit 20.21 in the figure.

The received signals 2O3, 21S are passed through an RF variable filter 26a,
26b. These RF variable filters 26a
, 26b is a narrowband tuning circuit, which extracts only the carrier component of the broadcast wave tuned on the receiver side by the above-mentioned DC control voltage supplied from the receiver 14 via the transmission cable 13. Then, its resonant frequency is controlled.

The outputs of the RF variable filters 26a and 26b are sent to the RF amplifier 2.
The signals are applied to detection circuits 28a and 28b via 7a and 27b, and the carrier level or carrier distortion level is detected. The detected output is given to the control circuit 29, and a switching control signal 293 for selecting the better received signal is formed by comparing the levels of the two systems of signals. Based on this control signal 29S, one of the received signals 205 and 215 is selected by the changeover switch 23, and the transmission cable 13
is derived.

Figure 4 shows the antenna switching control circuit 24 and the switching switch 2.
FIG. 3 is a block diagram showing a modified example of No. 3; In this example, first, one of the received signals 20S and 215 is selected by the changeover switch 23, and based on the selected output, a detection system is activated from one system of RF variable filter 26, RF amplifier 27, detection circuit 28, and control circuit 29. A switching control signal 29S is generated. This switching control signal 29S is supplied to the switch 23, and one of the better received signals is selected. variable RF
The operations of the filter 26, RF amplifier 27, and detection circuit 28 are the same as in FIG. 3, and in this example, the DC control voltage E supplied from the receiver 14 via the transmission cable 13 is
It is applied to the variable filter 26.

The control circuit 29 includes, for example, a comparator that compares the FM carrier level with a predetermined threshold level.

〔Effect of the invention〕

As described above, the invention of claim 1 includes a plurality of antenna conductors 3.
．． 4 and a diversity receiving circuit 22 are provided on the window glass, and the best one is selected from among the received signals induced by the plurality of antenna conductors 3.4 and delivered to the receiver 14. Transmission cable 13 between machine
Only one receiver is required, which simplifies the configuration of the automotive receiving system, and since a dedicated receiver with a built-in diversity receiving circuit is not used, there is a high degree of freedom in system configuration.
It's cheap.

It also discriminates the quality of each received signal based on the RF received signal,
Since the antenna switching control signal is formed, the configuration of the diversity receiving circuit is relatively simple, and since the discrimination is performed on the glass surface, the discrimination accuracy is high and reliable antenna switching is possible.

In the invention of claim 2, since the switching control signal is formed by mutual comparison of a plurality of received RF signals, accurate switching is possible. This simplifies the circuit configuration.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an automobile receiving system to which the diversity receiving device of the present invention is applied, Fig. 2 is a block diagram of the internal circuit (diversity receiving circuit) of the hybrid IC shown in Fig. 1, and Fig. 3 is an antenna switching control diagram. FIG. 4 is a block diagram showing another example of the antenna switching control circuit. In addition, in the symbols used in the drawings, 1・-・−・・ Rear window glass 2−・−・−・
・-m----------Heater wire 3.4---m--
-・-1------Antenna conductor 10.11
Chilark coil 12 Hybrid IC 20, 21 ~---1...Active matching circuit 23
−−−−−−・−・−・・・・Switch switch 2
．． 1------1~--=----Antenna switching control circuit 25---1-----------11 Impedance matching circuit 26a, 26b --- ---
RF variable filters 27a, 27b -------RF
Amplifiers 28a, 28b ---Detection circuit 29--
−−−−−・−・・−・Control circuit.

Claims (1)

[Scope of Claims] 1. A plurality of antenna conductors and a diversity reception circuit for selecting the one with the best quality from among the plurality of reception signals from each antenna conductor are provided on a window glass surface, the diversity reception circuit as described above; includes an antenna switching control circuit that forms a switching control signal based on a received RF signal, and a plurality of received RF signals from the antenna conductor according to the switching control signal.
A diversity receiving device for an automobile, comprising a changeover switch for selecting one of the signals. 2. The vehicle according to claim 1, wherein the diversity receiving circuit includes the antenna switching control circuit that forms the switching control signal based on mutual comparison of a plurality of received RF signals from each of the antenna conductors. Diversity receiver. 3. The diversity receiving circuit includes the antenna switching control circuit that forms the switching control signal based on a comparison between one received RF signal output from the changeover switch and a preset reference value. The automobile diversity receiving device according to claim 1, characterized in that: 4. The diversity receiving device according to claim 1, wherein the antenna switching control circuit includes a variable RF filter that is tuned to the receiving frequency.