JPS5868323A - Antenna amplifier of receiver for motorcar - Google Patents

Abstract

PURPOSE:To prevent unnecessary power consumption by deciding on whether the electric field intensity of a tuning frequency received signal is greater than that of the reception band of an antenna or not through an antenna amplifier, and controlling the passing band of a filter. CONSTITUTION:The hot wire 2 in the rear windshield glass 1 of a motor car is used as an antenna 8 and a radio wave received by it is inputted to the filter 14, narrow-band BPF16, and electric field intensity detecting circuit 18 of an antenna loop 24. When a radio receiver 12 selects a frequency f0, the center frequency of the BPF16 is set to the frequency f0 by a signal (a), and a comparison 19 of electric field intensity between the entire reception bands detected by an electric field intensity detecting circuit 17 for the frequency f0 and the circuit 18 is made. If the electric field intensity at the f0 is small, the filter 14 is set to a narrow band centering the f0 as its center frequency by the signal (a) through a switch 21, and its output is amplified by an amplifier 15 and inputted to the receiver 12. When the electric field intensity of the BPF16 is high and found to be greater than a prescribed value 23 through comparison 22, a signal (b) is outputted to perform control so that the output of the filter 14 is inputted to the amplifier 15 as it is. Therefore, when the electric field intensity at f0 is large, the amplifier 15 is not in operation, thereby reducing the power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna amplifier for an automobile receiver.

Conventionally, some car receiver antennas have been modified to receive radio broadcast waves by using hot wires installed in the rear window glass to remove the fog (Japanese Patent Publication No. 56-244). When using such an antenna, the in-vehicle radio receiver is usually installed in the instrument panel at the front of a single room and is far away from the antenna, and antennas that also serve as hot wires have poor reception sensitivity. Because of this, the signal from the antenna is first amplified by an antenna amplifier and then sent to the receiver.

However, with conventional antenna amplifiers, the entire receiving band of the antenna is amplified, so the electric field strength of the radio waves of the selected broadcasting station is smaller than the electric field strength of the entire receiving band of the antenna, especially the field strength of adjacent frequencies. In this case, there is a problem that the difference in electric field strength between the selected frequency and the adjacent frequency increases further, causing interference and making it difficult to hear.

In order to solve this problem, it is conceivable to pass the signal from the antenna through a narrowband filter and then input it to an amplifier to amplify only the received signal of the selected frequency, but this is different from the above. On the other hand, if the electric field strength of the selected frequency is greater than that of the adjacent frequency, a narrow band filter is not needed as much. Therefore, if the filter is always activated, output loss and wasteful power consumption will be avoided. This is not desirable.

This invention was made in view of the above-mentioned problems, and uses a discriminating circuit to determine whether or not the electric field strength of the received signal at the tuned frequency is smaller than the electric field strength of the receiving band of the receiving antenna. By setting the passband of the filter as a narrow band to amplify only the received signal at the tuned frequency, and otherwise setting the passband of the filter to be the entire receiving band and sending all the received signals as they are to the receiver, the receiving sensitivity is improved. The purpose of the present invention is to provide an antenna amplifier for an automobile receiver that eliminates wasteful power consumption.

FIG. 1 shows an antenna amplifier for an automobile receiver according to an embodiment of the present invention. In the figure, 1 is a rear window glass of an automobile, 2 is a plurality of hot wires fixed to the rear windshield 1 in parallel with each other and used to remove fog from the shell glass 1, 3 is an electrode of the hot wire 2, and 4 is the above-mentioned An antenna 5 for receiving AM broadcasting, which is composed of a plurality of hot wires 2 and electrodes 3.
6 is an antenna for receiving FM broadcasting which is fixed above the antenna 4 on the rear window glass 1; 7 is an antenna for receiving antenna 6; A stub for preventing the received signal from escaping to the ground IC via the antenna 4, 8 a receiving antenna consisting of both antennas 4 and 6, 9 a terminal for extracting the signal of the receiving antenna 8, 103 a capacitor, 10b a A battery 10C is a switch for energizing the hot wire 2.

Further, 12 is a radio receiver attached to an instrument panel (not shown) at the front of the vehicle, 13 is a speaker thereof, and 14 is a filter connected to the terminal 9 of the receiving antenna 8. The passband becomes a narrow band centered on the tuning frequency of the radio receiver 12 when a tuning signal is input from the radio receiver 12, and becomes the entire receiving band of the receiving antenna 8 when no tuning signal is input. 1
5 is the filter 1 when inputting a gain control signal, which will be described later.
This amplifier amplifies the signal from the filter 14 and outputs it to the radio receiver 12, and outputs the signal from the filter 14 as it is when no gain control signal is input.

Furthermore, 16 is connected to the terminal 9 of the receiving antenna 8,
A narrow band pass filter whose passband center frequency is the tuning frequency of the radio receiver 12; 17 is a first electric field strength that detects the electric field strength of the received signal at the tuning frequency, that is, the magnitude of the output of the narrow band pass filter 16; a detection circuit; 18, a second electric field strength detection circuit for detecting the electric field strength of the entire receiving band of the receiving antenna 8; 19, both electric field strength detection circuits 17;
A first comparator that compares the outputs of 18, 20 is the above-mentioned 16-
19, a discrimination circuit for discriminating whether the electric field strength of the received signal of the tuning frequency is smaller than the electric field strength of the entire reception band; and 21, a tuning signal input to the filter 14 according to the output of the discrimination circuit 20; 22 is a second comparator that compares the output of the first field strength detection circuit 17 with a reference voltage 23 and outputs the gain control signal. The antenna amplifier 24 is composed of the above-mentioned numbers 14 to 23.

Next, the operation will be explained using FIGS. 2 to 4.

The second case) shows a case where the electric field strength of the received signal at the tuning frequency fo of the radio receiver 12 is smaller than the electric field strength at the adjacent frequencies fl and f2, and is less than the set level of 100 dB. In this case, first the radio receiver 12
When tuned to frequency to, this receiver 12 generates a tuning signal n. Then, the beam 16 passes only the frequency fO of the received signal from the reception antenna 8, and the first electric field strength detection circuit 17 detects the electric field strength of the signal of the frequency fO. On the other hand, the second electric field strength detection circuit 18 detects the electric field strength of the entire receiving band of the receiving antenna 8, and therefore, in this case, the frequency f
The electric field strength of the strongest frequency 11 among o, fl, and fg is detected, and now the electric field strength of the signal of the tuning frequency fO is smaller than that of the signal of the frequency ft, so the output of the first comparator 19 is The analog switch 21 applies the tuning signal - to the filter 14, and the center frequency of the passband of the filter 14 is the tuning frequency f.

This results in a narrow band. Also, since the electric field strength of the signal at the tuning frequency fo is less than the set level of 100 dB, the output of the second comparator 22 becomes 1...I', and the gain control signal is outputted, and the amplifier 15 outputs the gain control signal to the filter 14. In order to amplify the output signal of the antenna amplifier 24 as shown in FIG.
As shown in FIG. 2, only the signal at the tuning frequency fO is amplified and output to the radio receiver 12.

In addition, FIG. 3 (al indicates the case where the electric field strength of the signal at the tuning frequency fO is greater than the electric field strength of the signals at the adjacent frequencies fl and fz and is 100 dB or less. In this case, the reception band of the reception antenna 8 is Even if the signals in the entire area are amplified and sent to the radio receiver 12, no interference will occur, so in this antenna amplifier 24, the first comparator 19 has 10 outputs, and the analog switch
blocks the input of the tuning signal 1 to the filter 14, the pass band of the filter 14 becomes the entire reception band, and the antenna amplifier 24 changes the frequency fo, fl as shown in FIG.
, f2 are amplified and output.

In addition, Fig. 4 (ml indicates the case where the electric field strength of the signal at the tuning frequency to is greater than the electric field strength of the signal at the adjacent frequency f2 and is above 100 dBJ2. In this case, the receiving band of the receiving antenna 8 is The filter 14 may be configured so that the signals in the entire area are sent as they are to the radio receiver 12.
The passband of the antenna amplifier 24 is the entire reception band as described above, and the output of the second comparator 22 is 10G, and the amplifier 15 outputs the signal of the filter 14 as it is without amplifying it. As shown in Figure (b), the signals of the entire receiving band of the receiving antenna 8 are output as they are.

In the antenna amplifier of this embodiment as shown above, the passband of the filter is switched according to the electric field strength of the received signal at the tuning frequency of the radio receiver, thereby preventing the occurrence of radio receiver interference. Filter 1
It is possible to prevent output loss and wasteful power consumption caused by 41. Furthermore, since the gain of the amplifier is switched according to the electric field strength of the received signal at the tuning frequency, distortion does not occur in the characteristics of the amplifier, and this also improves the receiving sensitivity of the radio receiver.

In the above embodiment, the gain of the amplifier is changed depending on the electric field strength of the received signal at the tuning frequency, but the gain of the amplifier may be constant.

Furthermore, in the above embodiment, the receiving antenna uses the hot wire of the rear window glass, but this receiving antenna may be used only for receiving radio waves, or may be provided on the front side. .

As described above, according to the antenna amplifier for an automobile receiver according to the present invention, when the electric field strength of the received signal at the tuned frequency of the receiver is smaller than the electric field strength of the entire receiving band of the receiving antenna, it is determined and filtered. Let the passband of be narrow band,
Since only the tuned frequency signal is amplified and sent to the receiver, interference at the receiver can be prevented and reception sensitivity can be improved.
Moreover, it has the effect of preventing output loss and wasteful power consumption due to the filter.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of an antenna amplifier of an automobile receiver according to an embodiment of the present invention, and Figs. 2 to 4 show the electric field strength of the receiving band in each case and the output of the antenna amplifier at that time. FIG. 8... Reception antenna 12... Radio receiver (vehicle receiver) ゛ 14... Filter 15... Amplifier 20... Discrimination circuit 21... Analog switch (characteristic switching circuit) Patent applicant Toyo Kogyo Co., Ltd. Agent Patent Attorney Haya **- Figure 2 Figure 3! '1 Wave Book - Figure 4 1/V) Shuwo Shokan -

Claims (1)

[Claims] (1) In a receiving antenna amplifier installed in a car, when a tuning signal from an on-vehicle receiver is input, its passband becomes a narrow band centered around the tuning frequency of the on-vehicle receiver, and when no tuning signal is input. a filter whose passband covers the entire receiving band of the receiving antenna; an amplifier that amplifies the signal from the Mukuro filter and outputs it to the on-vehicle receiver; a determination circuit that determines whether the electric field strength of the received signal of the tuned frequency is smaller than the electric field strength of the entire reception band of the receiving antenna; and a determination circuit that disconnects or disconnects the tuning signal input to the filter according to the output of the determination circuit. An antenna amplifier for an automobile receiver, characterized by comprising a characteristic switching circuit.