JPS5892148A - Synthesizer receiver - Google Patents

Abstract

PURPOSE:To automatically switch the selectivity characteristics, by easily detecting the presence/absence of an interference signal, through a DC component detection of a frequency detecting signal at a frequency near a desired signal frequency. CONSTITUTION:Taking a frequency of a desired reception signal as f0, the reception frequency of a receiver is set to f0tDELTAf ahead the start of reception. When no interference signal exists or there is an interference signal negligibly small, a detected DC component is V2 apart from V0. If an interference signal not negligible exisis in a frequency f', the detected DC component moves to V3. Depending whether or not this detected DC component exceeds a threshold value Vt1, the pass band width of the receiver is automatically selected, allowing to obtain the receiver convenient in use. The receiver like this can easily be constituted by using a microprocessor and a voltage comparator. In case of a normal FM reception, it is suitable to select DELTAf=+ or -100kHz.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synthesizer receiver, and its purpose is to automatically switch the signal passband width in an intermediate frequency amplification stage or the like in order to change the selection characteristics for a desired signal. The objective is to provide a synthesizer receiver that can.

Generally, in signal reproduction by a receiver, the wider the signal passing band width (hereinafter referred to as "bandwidth") in the high frequency amplification stage, intermediate frequency amplification stage, etc., is, the higher the high-fidelity performance of the detected signal will be. However, on the other hand, in order to remove the influence of interfering signals near the desired station, the narrower the bandwidth, the better. In recent years, receivers (especially FM receivers) have been able to switch the bandwidth of their intermediate frequency amplification stage, so that when there is no interference nearby, the receiver receives in a wide band, and when there is interference, it receives in a narrow band. It is in the direction of However, since this switching of the bandwidth is usually done manually, it is easy to judge when the presence of adjacent interference waves is clearly audible, but in other cases it is difficult to decide which bandwidth to select. It is also uncertain whether that judgment is appropriate.

Therefore, in the "Specification of Japanese Patent Application No. 55-130945", the present applicant has proposed that the desired signal signal be We have described a receiver that can automatically select the optimal bandwidth by comparing the signal level and the signal level at nearby frequencies. However, in this case, a signal level detection means with a relatively wide dynamic range is required within the receiver, and calculations for relative comparison of the levels of the desired signal and the interfering signal are also required, making the single circuit configuration extremely complex. It is expensive.

The present invention detects the degree of interference of a nearby interference signal with respect to a desired signal without detecting the signal level.

This makes it possible to select the most suitable bandwidth for the situation.

FIG. 1 is an explanatory diagram for explaining the present invention in detail.

If there is a sufficiently large interference signal in the vicinity of the desired signal located at the frequency fO, the interference cannot be removed completely by the selectivity of the filter in the intermediate frequency amplification stage, resulting in large distortion in the reproduced signal.

On the other hand, at this time, the DC component of the detected signal output from the FM detector is Vo when there is only the desired signal, but moves to Vl due to the energy of the interference signal. Further, the amount of movement depends on the level ratio between the desired signal and the interference signal (hereinafter referred to as the D/U ratio). Therefore, by detecting the DC component of the FM detection signal in a state in which it is tuned to the desired signal frequency, the degree of the interference signal can be detected. However, this is not sufficient for practical use. In other words, in a normal receiver, even if the level of the interfering signal is not high enough to cause a noticeable change in the DC component of the detected signal, a sufficiently large distortion will appear in the reproduced signal. In other words, using the detection method based on the principle shown in FIG. 1, it is difficult to detect interference more sensitively than the auditory detection limit and switch bands.

Therefore, the present invention uses a method of detecting interference signals by approaching them, as shown in FIG.

First, the reception frequency of the receiver is set to a frequency fO+Δf between the desired signal frequency fO and a frequency f' at which it is thought that there is an interfering signal that may affect this signal. If there is no interference signal or if the interference is negligible, the detected DC component will be v2, which is far away from vO. However, if non-negligible interference exists at frequency f', the DC component is D
/■ Move to v5 determined by the ratio. In this case, the influence of the desired signal and the interference signal appear almost equally on the DC component, so extremely sensitive interference detection can be achieved. Therefore, a predetermined threshold value Vt+ is provided for this DC component, and it is possible to determine whether or not the bandwidth should be switched depending on whether or not this value is exceeded. In Fig. 2, the interference signal frequency is higher than the desired signal, but the same applies to the opposite case as well.
2 All 2 settings can be detected. Further, when the number of selectable bandwidths is three or more, it is sufficient to prepare a corresponding number of thresholds.

FIG. 3 is a block diagram of an embodiment of a synthesizer receiver according to the present invention. Reference numeral 1 denotes a front end section, in which a reception frequency is set by a reception frequency control section 2. 3 is an intermediate frequency amplification section with a selectable bandwidth, and 4 is an FM detector. The DC component of the detection signal from the IFMFM detector is extracted by the low-pass filter 6 and input to the voltage comparator 6.

The bandwidth selection control section 7 selects the optimum bandwidth according to the output signal of the comparator 6. In recent years, the reception frequency control section 2 is usually constituted by a microprocessor, and it is possible to include the function of the bandwidth selection control section 70 as part of its functions (as part of a program).

In this case, the reception frequency control section 2 and the bandwidth selection control section 7 are integrated as a microprocessor 8.

FIG. 4 shows a specific configuration example of the voltage comparator 6, and each voltage
t1. It is composed of two voltage comparator circuits 9 and 10 having a threshold value of Vt2 (Vt+) Vt2), and outputs detection signals of Ql and Q2. 5. In relation to Figure 2. For detection at fo+△f, the input voltage is Vt
+, and if there is no interference, the detection signal Q1 becomes low level, and if there is, it becomes high level. Next, in the detection at fO-Δf, the input voltage is compared with Vt2, and if there is no interference, the detection signal Q2 is at a low level.

If so, it will be at a high level. However, if it is possible to set Vt+ = Vt2 depending on the characteristics of the receiver, only one comparator circuit is required.

Next, as described above, when the tuning function and the bandwidth selection function are executed by the microprocessor 8, what procedures are used to set the receiving frequency, read the detection signal of the voltage comparator 6, and select the bandwidth? The flowchart in FIG. 6 will be used to explain how the process is carried out. However, here, there are two types of switchable bandwidths: wideband and narrowband. First, in step 11, it is repeatedly checked whether a new reception frequency has been set (or whether a new station has been selected). When a new reception frequency is set, move to step 12 and select "wideband". Next, at step 13, the reception frequency is set to fO+Δf, and at step 14, the detection signal Q1 is read. At step 16, it is checked whether or not this detection signal Q1 is at a low level. If it is at a low level, that is, if there is no interference, the process moves to step 16, and this time the receiving frequency is set to fO-.
Set to Δf.

At step 17, the detection signal Q2 is read, and at step 18, it is checked whether or not it is at a low level. Here, if the level is still low, the process moves to 20 to start receiving at fO, and returns to 11 to wait for setting the next fO stage. On the other hand, when the detection signal q1 is at a high level at 15 or when the detection signal Q2 is at a high level at 18, it is considered that there is interference, so 19
After switching to "narrow band" at step 20.

Here, regarding the specific value of Δf, it is appropriate to select Δf=100KH2K since adjacent interferences of ±2oo and ±300 KHz are a problem in general FM receivers.

As explained in the above embodiments, in the present invention, detection of interference signals in the vicinity of the reception frequency f fo + △f and fO - △r
For example, if the time required for detection at each reception point is 0.1 seconds, the normal reception state can be returned promptly after a total of 0.2 seconds. Also, since the degree of interference is obtained from the DC component in the detection output,
Automatic bandwidth switching is now possible, which is advantageous in terms of cost, as it can be configured simply by adding a voltage comparator, and the decision for selection does not require computation by a complicated program.

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the principle of interference signal detection according to the present invention, Figure 2 is a diagram for explaining the practical principle of interference signal detection according to the present invention, and Figure 3 is a diagram for explaining the practical principle of interference signal detection according to the present invention. 04...FM detection Vessel, 6...
Voltage comparator, 8...Microprocessor, 9.
10... Voltage comparator circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 5

Claims (2)

[Claims] (1) A receiver capable of selecting a plurality of different signal passing bandwidths, including a detection means for detecting a DC component of a frequency detection signal, and a receiver that uses the detection result of the detection means to select one of the plurality of bandwidths. 1. A synthesizer receiver comprising: means for selecting a DC component, and controlling a receiving frequency so that the detection of a DC component by the detecting means is performed at a frequency near a desired signal frequency. (2) The synthesizer receiver according to claim 1, wherein when the desired signal frequency is fO, the DC component detection of the one-frequency detection signal is performed at fO+Δf and fO−Δf.