JPS5869139A - Receiver provided with diversity antenna - Google Patents

Abstract

PURPOSE:To obtain a reception state which is always stable without lowering the level of an IF signal, by synthesizing the phases of the IF signals corresponding to a plurality of antennas so that the phases can be matched. CONSTITUTION:An output voltage of a phase comparison circuit 34 is changed in accordance with the phase shift of signals from an amplifier circuit 32 with respect to signals from an amplifier circuit 33. As the phase shift becomes positive, the output voltage is lowered. The capacitance of a varactor diode 19 is increased as a voltage given from a line 20 is lowered to decrease the local oscillating frequency of a local oscillation circuit 12. The capacitance is changed so that IF signals on a line 5 are coincident with IF signals on a line 6 and the IF signals having the same phase and the same frequency can be synthesized at a synthesis circuit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiver equipped with a diversity antenna.

Such a receiver is used, for example, in a car, and even if the level of the input signal from one of the multiple antennas decreases, the other antennas can still receive the input signal at a sufficient level. This enables stable reception even in locations where the electric field strength of wireless signals is variable. In the prior art, signals from multiple antennas are combined and received. Therefore, if the input signals from each antenna have the same phase, it is possible to receive an input signal of sufficient level, but if the phases are reversed, the level of the combined input signal will drop. Became.

An object of the present invention is to provide a receiver equipped with a diversity antenna that allows stable reception at all times.

FIG. 1 is a block diagram of one embodiment of the present invention. This receiver is mounted on a car, and the car is equipped with a plurality of antennas 1.2 (Vi2 in this embodiment). Input signals from the antennas 1 and 2 are sent from the front end circuits 3 and 4 via lines 5.6 to a combination circuit 9 consisting of resistors 7 and 8, where they are combined. A front end circuit 3Iri, a tuning circuit 10 that receives and tunes an input signal from an antenna l, a mixing circuit 11 that receives a signal from the tuning circuit 10, and a buffer 2 in this mixing circuit 11.
Local oscillator circuit 1 which provides a local oscillator frequency signal via 5
2. In the local oscillation circuit 12, a capacitor 14 and a voltage-controlled variable capacitance diode 1 are connected in parallel to the coil 13.
A series circuit consisting of 5 and 5 is connected. A voltage is applied to the variable field diode 15 from a line 17 via a resistor 16. A parallel resonant circuit consisting of a coil 13, a capacitor 14, and a variable diode 15 includes a capacitor 18 and a voltage-controlled variable capacitance diode 1 in parallel.
A series circuit consisting of 9 is connected. A voltage is applied to the variable capacitance diode 19 from a line 20 via a resistor 21 . Capacity of capacitor 18'f! Therefore, the resonant frequency of the coil 13 and the parallel resonant circuit housed in the coil 13 can be changed by, for example, about ±lKH2. Buffer 25Vi, mixing circuit 11 is local oscillation circuit 12
This is used to prevent distortion from occurring at the local oscillation frequency No. 45.

The front end circuit 4 also includes a tuning circuit 22 that receives and tunes the input signal from the antenna 2, and a mixing circuit 23.
A local oscillator circuit 24 consisting of a phase-locked loop frequency synthesizer is provided. Tuned circuit 10.22V
It may have a high frequency amplification circuit, for example, 100 M
It is possible to receive and tune to frequency-modulated radio signals on the order of around H2. Local oscillation circuit 24 includes a voltage-controlled oscillation circuit 26 , a frequency division circuit 27 , a reference frequency oscillation circuit 28 , a phase comparison circuit 29 , and a low-pass filter 30 . The phase comparator circuit 29 derives a voltage proportional to the phase difference between the signals from the frequency divider circuit 27 and the reference frequency oscillation circuit 28, and thereby the voltage controlled oscillation circuit 26Vi.
, the oscillation frequency is changed so that the frequency of the output from the frequency dividing circuit 27 becomes the same frequency as that of the reference frequency oscillation circuit 28. The output from the low pass filter 30 is also provided to the tuned circuit 10.22 via line 17. The output signal of the voltage controlled oscillation circuit 26 is given to the mixing circuit 23 as a local oscillation frequency signal.

The intermediate frequency signal synthesized in the synthesis circuit 9 is subjected to intermediate frequency amplification and detection in an intermediate frequency amplification and detection circuit 41,
The audible frequency signal is amplified in the amplifier circuit 42 and audible sound is heard through the speaker 31. In this way, reception is performed in a superheterodyne manner.

The intermediate frequency times 5jt/i from line 5.6 are also amplified by amplifier circuits 32 and 33, respectively, and provided to phase comparator circuit . The phase comparison circuit 34 is the amplifier circuit 32
．． 33, a voltage proportional to the phase difference is derived, and is passed through the low-pass filter 35 to the line 2.
Derived into o. In this way, the capacitance of the variable capacitance diode 19 is changed so that the phase difference between the intermediate frequency signals on lines 5 and 6 becomes zero and they are in the same phase.

Referring to FIG. 2, a graph illustrating the operation of the phase comparison circuit 34 is shown. The output voltage of the phase comparator circuit 34 changes according to the fourth order shift of the signal from the amplifier circuit 32 with respect to the signal from the amplifier circuit 33 . As this phase shift becomes positive, the output voltage decreases. As the voltage applied from the variable capacitance diode 19t↓ and the line 20 decreases, its capacitance increases, and therefore the local oscillation frequency of the local oscillation circuit 120 changes to become lower. In this way, the intermediate frequency signal on line 5 changes to match the intermediate frequency signal on line 6, and in the synthesis circuit 9, intermediate frequency signals having the same phase and the same frequency are synthesized.

The present invention is applicable not only to superhetero gain type receivers but also to
It can also be implemented in a double superheterodyne type receiver.

As described above, according to the present invention, intermediate frequency signals corresponding to a plurality of antennas are synthesized so that their phases match, so that the level of the intermediate frequency signals is reduced.
Therefore, stable reception conditions can be obtained at all times.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a graph showing the characteristics of the phase comparison circuit 34. 1.2...Antenna, 3,4...Front end circuit, 9...Composition circuit, 10.22...Tuning is path, 1
1゜23...Mixing circuit, 12.24...Local oscillation circuit, 31...Speaker, 32.33...Amplification circuit,
34...Phase comparison circuit, 35...-Low pass filter, 41...Intermediate frequency amplification and detection circuit, 42...Amplification circuit agent Patent attorney Kei Nishi

Claims (1)

[Claims] '41 number of antennas, a tuning circuit for each antenna, a mixing circuit that receives signals from each tuning circuit, a local oscillation circuit that provides a local oscillation frequency signal to each mixing circuit, and a local oscillation circuit that provides a local oscillation frequency signal to each mixing circuit. A circuit that synthesizes and amplifies and detects intermediate frequency signals to derive an audio frequency signal, a phase comparison circuit that detects the phase difference between the intermediate frequency signals from each mixing circuit, and a local oscillation circuit that responds to the output from the phase comparison circuit. 1. A receiver equipped with a diversity antenna, comprising means for changing the local oscillation frequency of at least one of the circuits to bring intermediate frequency signals from a plurality of mixing circuits into the same phase.