JPS6169225A - Control circuit of fm diversity receiver - Google Patents

Abstract

PURPOSE:To prevent undesired high-cut action, separation control action, etc. by comparing the outputs of a subtractor circuit which subtracts the DC voltage from the S meter output voltage when a control signal is produced and then selecting an antenna. CONSTITUTION:Minus wave detection circuits 7A and 7B produce the DC voltages VA and VB corresponding to the AC components of the S meter output. The level discriminating circuits 8A and 8B produce control signals only when the levels of the VA and VB exceeds the reference voltage levels VRA and VRB respectively. The arithmetic circuit 9A and 9B subtract the VA and VB from the S meter output voltages VSA and VSB when the circuits 8A and 8B produce control signals. A comparison control circuit 10 sends the selection signal to an IF selection circuit 4 for selection of a channel A in the case of VSA-VA> VSB-VB and then a channel B in the case VSA-VA<VSB-VB respectively. At the same time, the circuit 10 sends a signal to an MPX stereo demodulator 6 for execution of a high-cut action and a separation control action. In other words, no control signal is produced unless the DC voltage exceeds the reference voltage.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an FM diversity receiver.
This relates to one circuit.

[Prior Art] Generally, when multipath occurs in an FM diversive receiver, it is necessary to perform a high-cut operation, a separate control operation, and a switching operation to another channel. is detected using the AC component of the S meter output for IF amplification, and this A
Each of the above operations was performed by detecting the C component.

[Problem to be solved by the invention 1 However, the S meter output of an IF amplifier usually contains some AC component in addition to the DC component, and of course this AC component increases greatly when multipath occurs. However, even if multipath does not occur, it increases due to poor ΔM suppression in the receiver or overmodulation, and therefore, in conventional systems, each of the above operations cannot be performed even when the AC component increases due to causes other than multipath. The problem was that it was done.

This invention solves the problems of the above-mentioned conventional ones, and
It is an object of the present invention to provide a control circuit for an FM diversity receiver that does not perform high-cut operation, separation control operation, or switching operation to another channel when the AC component of the S meter output of an F amplifier increases due to a cause other than multibus. That is.

[Means for Solving the Problems 1] In order to achieve the above-mentioned object, the present invention provides an FM diversity receiver for the main antenna and the sub-antenna that corresponds to the AC component of the S meter output of the IF amplifier.
a circuit that generates a C voltage; a circuit that compares the DC voltage with a reference voltage and generates a control signal when the DC voltage exceeds the reference voltage; and a circuit that generates a control signal when the DC voltage exceeds the reference voltage; A subtraction circuit for subtracting the voltage is provided, and the outputs of the two reduction circuits are compared to select the antenna with the higher output, and a comparison control circuit is provided that performs high-cut operation and separation control operation. It is something that it has.

[Function] By adopting the above means, the present invention can control the DC voltage so that it does not exceed the reference voltage when the AC component of the S meter output of the 1F amplifier increases due to a cause other than multipath. No signal is generated, and a control signal is generated only when multipath occurs and the DC voltage exceeds the reference voltage ratio -4, which causes high-cut operation, separation control operation, and switching operation to other channels. .

[Example] Embodiments of the invention shown in the drawings will be described below.

The figure shows an embodiment of the present invention, where 1A is a main antenna, 1B is a sub-antenna, 2A and 2B are front-end circuits, 3A and 3B are IF amplifiers, and 4 is an IF3F! selection circuit,
5 is a noise canceller circuit, 6 is an MPX stereo demodulator, and 7A17B is a negative detection and amplification of the AC component of the S meter output of the IF amplifiers 3A and 3B, and is inversely proportional to the AC component, that is, a >DC voltage corresponding to the AC component. vA,
■.

8A and 8B are the DC voltage v
, , Compare v8 with the reference voltage ■RA1vR8 and generate a control signal only when the DC voltages ■4 and ■8 exceed the reference voltages ■RA and ■R8 (that is, when multipath occurs) The level discrimination circuits 9A and 9B convert the DC component into A when the level discrimination circuits 8A and 8B control signals are generated.
S meter output voltage where C component is heavy v8A, ■8B
A subtraction circuit that subtracts DCNIfVA1■8 from the subtraction circuit 10 compares the output vSA"-vA of the subtraction circuit 9A and the output ■SB-"B of the subtraction circuit 9B, and finds that v -v > vsB
A selection signal is sent to the IF selection circuit 4 to select channel SA A when the signal is -v8, and channel B when the signal is V8A-vA (5B-VB), and is sent to the MPX stereo demodulator 6. This is a comparison control circuit that sends signals to perform high cut operation and separation control operation.

The above FM diversity receiver uses DC voltage ■A1■8
As long as the DCI voltage does not exceed the reference voltage VIIA"ltB, the level discrimination circuits 8△ and 8B generate control signals, and the DCI voltage V
, V8 exceeds the reference voltage ■RA, vR8 (that is, when multipath occurs), the level discrimination circuits 8A, 8B generate control signals, thereby controlling high-cut operation, separation control operation, and control to other channels. A switching operation will be performed.

[Effect of the invention] Since this invention is configured as described above, the S of the IF amplifier is
If the AC component of the meter output increases due to causes other than multipath, it is possible to prevent high-cut operation, separation control operation, and switching to other channels. Therefore, it is possible to prevent channel fixation during adjustment, confirmation, and check on the production line. It has excellent effects such as not having to perform

[Brief explanation of the drawing]

The figure is a block diagram showing one embodiment of the present invention. 1A...Main antenna, 1B...Sub antenna,
2A, 2B...Front end circuit, record, 3B...
・IF amplifier, 4... IF selection circuit, 5... Noise canceller circuit, 6... MPX stereo demodulator, 7A
, IB...Minus detection circuit, 8A, 8B...Level discrimination circuit, 9A, 9B...Sigma reduction circuit, 10...
comparison control circuit

Claims (1)

[Claims] 1. In an FM diversity receiver, a circuit that generates a DC voltage corresponding to the AC component of the S meter output of the IF amplifier for the main antenna and the sub antenna, and the D
A circuit that compares the C voltage with a reference voltage and generates a control signal when the DC voltage exceeds the reference voltage, and a subtraction circuit that subtracts the DC voltage from the S meter output voltage when the control signal is generated. A control circuit comprising: a comparison control circuit which compares the outputs of both the aperture reduction circuits, selects a higher output antenna, and performs a high cut operation and a separation control operation.