JPS5928731A - Fm receiver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an FM receiver using an FM negative feedback system.
In the M receiver, as shown in Fig. 1, as a method to perform high-sensitivity reception by narrowing the intermediate frequency amplification section, the high-frequency signal from the antenna and the output of the local oscillator (3) are mixed into a mixer (2). The signal is converted into an intermediate frequency signal, amplified by an intermediate frequency amplifier (4), and then detected by an FM detector (5) to obtain an FM detection output.
A configuration in which the detected output is negatively fed back to a local oscillation device (3) is known. In the figure, (,1) is a high frequency amplifier.

In other words, by applying K frequency modulation to the local oscillator (3) using the FM detection force, the local oscillation frequency follows the frequency deviation of the high-frequency signal, and the change is compressed more than that of the high-frequency signal, so-called LQh. F) If negative feedback method F
M receivers are known.

In this conventional method, the resonant circuit (6) of the local oscillator (3)
By applying the FM detection output to the n-capacitance diode D connected in parallel with the FD and reverse biasing it, the capacitance of the i'iJ variable capacitance FD is changed and the local oscillation frequency is controlled. A] [7. Once, the variable capacitance diode D (! - resonant circuit (6) in parallel
Since the capacitance of the variable Vc is included, the amount of FM negative feedback becomes larger in the high frequency region than in the low frequency region, and the depth of modulation differs depending on the tuning frequency. That is, there was a drawback that various characteristics such as distortion rate and degree of stereo separation varied depending on the tuning frequency Q.

The present invention improves these conventional drawbacks, and has the following features:
This will be explained using the ζ diagram. In the figure, parts that are equivalent to those of the conventional example shown in FIG.

To explain this in FIG. 2, the output signal (frequency θυ number/L) of the local oscillator (7) and the output signal of the voltage controlled oscillator (8) (center frequency/V) are transferred to the second mixer (9). input the α)1 signal in the frequency 1L-fV of the difference between both signals to r(
I will. Among these, the 1711 signal 4 and the high frequency signal (frequency f) are mixed in the first mixer (10) to obtain an intermediate frequency signal with the frequency θν number/i of the difference in image quality.Here, /i= /-(/L-
fV) After this intermediate frequency signal is amplified by the intermediate frequency amplifier (4), it is detected by the F tile detector (5) to obtain the FM detection output, and this FM @ wave output is converted to the frequency θ m It has a configuration in which FM negative feedback is applied to the voltage controlled oscillator (8) as a single voltage control.

Specifically, taking as an example the FM band in Japan, which is defined as a frequency band of 76 to 90 MHz and an intermediate frequency signal of 10.7 MHz, /L = 67.3 to 81.3 MHzfV = 2
MHz, the intermediate signal ranges from 65.3 to 79.3 MHz, which is the same as the conventional local oscillation frequency.

In the embodiment described in "-", the circumference of the output signal of the local oscillator (6) and the output signal of the voltage controlled oscillator (7) is expressed as the number of cores fL,
Define fV and IL as above, and set the frequency of the difference in image quality to be the same as the conventional local oscillation frequency, or set the frequency of the sum of the image characteristics to be the same as the conventional local oscillation frequency. The configuration described in 1- below means that the oscillation frequency can be changed to 1 within a predetermined frequency range.
Unlike the conventional method, which applies FM negative feedback to the local oscillator (3), the oscillation frequency (center frequency) is constant.
F-controlled oscillator (8) KFMFM has a configuration that provides negative feedback, and there is no effect of the capacitance change of the resonant circuit in the conventional system, and the amount of FM negative feedback remains constant regardless of the tuning frequency. .

However, various characteristics such as distortion rate and stereo separation become constant over the entire frequency band.

As shown below, in the FM tuner using the FM negative feedback system of the present invention, the output signal of the local oscillator and the output signal of the voltage controlled oscillator are mixed and the frequency of the harmonization or difference between the two signals is determined. The configuration is such that an intermediate signal is obtained, this intermediate signal and a high frequency signal are mixed to obtain an intermediate frequency signal, and the FM detection output is fed back as FM negative feedback to the voltage controlled oscillator. A constant amount of FM negative feedback can be obtained over a period of time, and various characteristics such as distortion rate and degree of stereo separation are constant.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a conventional FM negative feedback type FM receiver, and FIG. 2 is a diagram showing the configuration of the FM receiver of the present invention. (1) is a high frequency amplifier, (4) is an intermediate frequency amplifier, (5
) itFM detector, (7) is the local oscillator, (8) is the voltage controlled oscillator, (9) is the second mixer, (10) is the twelfth
f'i: It is a combined volume. Patent applicant Onkyo Co., Ltd. agent Patent attorney Yatabe Sato

Claims (1)

[Scope of Claims] An FM receiver comprising the following constituent elements (a) to (g). (a) A local oscillator (7) whose oscillation frequency changes within a predetermined frequency range. (b) A voltage-controlled oscillator (8) that has a constant center frequency and whose oscillation frequency changes within a predetermined frequency range around this center frequency (c) The output signal of this voltage-controlled oscillator (8) and the above a second mixer (9) that mixes the output signal of the local oscillator (7) and outputs an intermediate signal with the frequency of the sum or difference of both signals;
. (→The first mixer (10) mixes this intermediate signal and the high frequency signal from the antenna and outputs an intermediate frequency signal with a frequency of the difference between the two signals. Amplifier (4)
. Obtain FM detector (5). (g) An FM negative feedback loop that negative-feeds this FM detection output to the voltage-controlled oscillator (8) as a frequency control voltage.