JPS5919444A - Space diversity receiver - Google Patents

Abstract

PURPOSE:To decrease noise, by switching a set level of a discriminating circuit with the electric field strength for providing a chance to switch an antenna even if a radio wave itself goes to weak and noise is increased. CONSTITUTION:A signal from an intermediate amplifier 6 is applied to a low pass filter 16 and a filter 18 eliminating components of <=19kHz. Further, a signal converted into a DC at a detector 19 is applied to a discriminating circuit 20 and a trigger signal is generated when the level is at a set level or over. On the other hand, an AM component is generated at a sensitive switching circuit 21 because of noise of itself when the radio wave goes to weak. Then the discriminating level of the circuit 20 is increased and malfunction is prevented. A sample hold circuit 12 is operated by the trigger signal, an output signal level of a lower side detector 17 is held, then an output of the circuit 12 is compared with an output of the detector 17 having a level after antenna switching, and if the output of the detector 17 is larger, the antenna in use is held as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a space diversity receiving device that switches between two antennas and selectively receives the one with a better reception condition, and more specifically, a one-selection determination method for determining which one has a better reception condition. Regarding circuits.

A conventional space diversity receiver is shown in FIG.

Conventionally, the electric field of the radio wave induced in the antenna 1 is detected by a level detector 11, and the detected signal is sampled and held by a sample and hold circuit 12 that samples the detected signal at the clock timing from a clock pulse generation circuit 15. The state of the radio wave induced in the antenna 2 is detected in the same manner as described above by switching in a well-known manner, and the level of the detected signal and the sample-hold signal are compared, so that the antenna with a better reception state receives the signal.

However, in the conventional method, the antenna is switched even if the current receiving antenna is in good condition, so the receiving condition of the antenna is judged, so if the receiving condition of the other antenna is poor, noise is generated periodically. There is. Furthermore, in the past, since the reception states of the antennas 1 and 2 were compared only instantaneously, malfunctions were likely to occur due to transient states of antenna switching.

It has its drawbacks. In addition, conventionally, the antenna switching timing signal was generated at the same setting level, but in a weak electric field, the first field strength signal level is low and the absolute amount of the eyebrow component is also small, so it is necessary to avoid the reception condition becoming extremely bad. No pulse occurred.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a space diversity receiving apparatus which improves antenna switching sensitivity and reduces noise.

An embodiment of the present invention will be described below with reference to FIG. In the figure, 1 and 2 indicate antennas, and the signals induced in the antennas are selectively switched at an antenna switching circuit @5,
The selection switching signal is selectively amplified by a high frequency amplifier 4, then converted to an intermediate frequency by a mixer 5, and then sent to an intermediate frequency amplifier 6. FM filter 7. The signal is guided to a speaker 9 via a low frequency amplifier 8. Reference numeral 11 indicates a level detector for detecting a part of the signal from the intermediate amplifier 6, and the level of the signal detected by the detector changes in proportion to the strength of the radio wave. 1
6 is a low-pass filter that obtains the average value of the changes; 17
is the lower detector. This lower detector 17 has a quick response when the signal decreases, but a slow response when the signal increases, so it can cut the noise when the electric field temporarily increases due to noise when switching antennas. The output signal of this detector 17 is guided to a comparator 15.

Reference numeral 18 denotes a filter that removes components below 19H2 of the output of the level detector 11 and passes the others.

The signal that has passed through the filter enters the detector 19 and becomes a direct current at the +i detector. If the filter 1B is disturbed by multipaths such as reflection while the radio wave is transmitted from the broadcasting station to the antenna, the strength of the radio wave will change as is well known, and an AM component will be generated in the output of the level detector 11. In addition, since the modulation degree of the pilot signal of this At1 (19KH2 pilot part of the component is constant according to the regulations), a good correlation with multipath distortion can be obtained.This has been confirmed by actual measurements, so 19
This filter is centered on KHz, and this level is proportional to the amount of multipath. This signal is detected by the detector 19
The DC signal is converted into a DC current and supplied to a determination circuit 20, which generates a trigger signal when the DC level is equal to or higher than a set level set by the determination circuit 20. Reference numeral 21 denotes a sensitivity switching circuit, which, when the radio waves become weak, generates a voice component due to the self-noise of the radio and malfunctions. Therefore, in a weak electric field, the determination level of the determination circuit 200 is raised to prevent malfunction. When a trigger signal is generated from the determination circuit 20, the sample hold circuit 12 operates and holds the level of the output signal of the lower detector 17. Thereafter, antenna switching is performed as described below. The antenna switches and its state is applied to comparator 15 as before. The transient state at this time is caused by the lower detection circuit 17 (actually, a PNP transistor).

(consisting of an emitter follower detection circuit). Sample ho in this way.

The comparator 15 compares the output of the field circuit 12 and the output of the lower detection circuit 17, which is the level after switching. If the output of the lower detection circuit 17 is large, the antenna is held as it is, and then Also, until the judgment circuit 20 receives the trigger signal,
If the sample and hold circuit 15 is larger, a signal is generated from the comparator 15 to the hold circuit 14 to cause the switching circuit 5 to operate so as to return the antenna to the original antenna 1. This operation is maintained until the determination circuit 20 receives a trigger signal. In this way, by switching the antenna only when multipath occurs, noise generation due to erroneous switching is reduced, and at the same time, the state of the radio waves can be determined correctly, allowing reception with low multipath distortion and noise. ,can.

According to the present invention as described above, since the antenna can be selected and switched correctly, it is effective to reduce the malte pass noise and skip noise of the FM car radio.
The pulse generation setting level is set low in weak electric fields and high in areas with strong radio waves, and is switched depending on the electric field strength. Even when the noise increases, it senses the noise and issues a switching signal, increasing the number of selection opportunities and reducing the noise. Also, in strong electric fields, noise generation can be prevented without switching more than necessary.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a determination circuit of a conventional space diversity receiver, and FIG. 2 is a block diagram of a determination circuit according to the present invention. 1... antenna, 2... antenna, 3...
・Antenna switching circuit, 4...High frequency amplifier, 5...Mixer, 6...Intermediate frequency amplifier, 7...FM detector, 8...Low frequency amplifier, 9.・Speaker, 10...local oscillator,
11...Level detection, 12...Sample and hold circuit, 15...Comparator, 14...Hold circuit. 15...Clock. 16...Low pass filter, 17...Lower side detection circuit, 18...Filter. 19...Detection circuit, 20...Judgment circuit, 21-...
Sensitivity switching circuit. O 1 Illustration 2 Illustration/δ lγ

Claims (1)

[Claims] 1st. selecting a second antenna and one of the antennas;
an antenna switching circuit that guides the received signal induced in the selected antenna to a reception regeneration circuit; and an antenna switching circuit coupled to the reception regeneration circuit;
a detection circuit that detects a level signal proportional to the received signal;
a sample and hold circuit that samples and holds a detection signal of the detection circuit when receiving a control signal (pulse); a comparison circuit that compares the hold signal of the sample and hold circuit with the detection signal of the detection circuit; and a comparison circuit that is coupled to the comparison circuit. , a space diversity system comprising an antenna switching control circuit that receives the control signal and supplies an antenna switching control signal to the antenna switching circuit when the detection signal is smaller than the hold signal; A 7α component detection circuit that is coupled to the hold circuit, the comparison circuit, and the antenna switching control signal generation circuit, and detects the output component when the generated component of the detection signal of the detection circuit exceeds a set level; and the 7α component detection circuit. a control signal generation circuit that generates the control signal when receiving the detection signal and supplies the control signal to the sample and hold circuit, the comparison circuit, and the antenna switching control signal generation circuit; the detection circuit and the layer component detection circuit; 1. A space diversity receiving device comprising: a sensitivity switching circuit coupled to the detection circuit and changing the set level according to the electric field strength according to the level of the output signal of the detection circuit.