JPS58151717A - Sweep receiver - Google Patents

Abstract

PURPOSE:To ensure accurate and assured stoppage of sweep, by locking in a crystal oscillating circuit of a local oscillating part by the intermediate frequency component to obtain a sweep stopping signal. CONSTITUTION:The 1st PLL is provided with a crystal oscillator 17, a frequency/voltage variable crystal oscillating circuit 18, a frequency multiplier 19, a phase comparator 20, a 1/n frequency divider 21, an LPF2 and a VCO23. A phase comparator 27 compares the phases between the 1/m component of an intermediate frequency signal and the 1/p component of the reference signal. Then the 2nd PLL is formed to lock the crystal oscillating circuit in an intermedite frequency. As a result, a lock signal can be extracted by locking in a local oscillating part with the intermediate frequency signal component. This process enables the assured stoppage of sweep with no effect of the selection characteristics of an intermediate frequency stage and the frequency stability degree of the center potential of an FM demodulator.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sweep receiver, and in particular, it is an object to effectively obtain an automatic sweep stop signal of the sweep receiver during reception signal tuning.

Conventionally, a stop signal for the automatic sweep operation of a sweep receiver has been obtained by detecting the signal level of a selective reception signal obtained at an intermediate frequency amplification stage of the receiver, and obtaining a stop signal from this signal.
In an FM receiver, there is a method of obtaining a stop signal from a center potential signal of a demodulated signal obtained from an FM demodulator.

Figure 1 is a circuit block diagram for obtaining a sweep stop signal in an AM receiver.The signal received by antenna 1 is high-frequency amplified, converted to an intermediate frequency, passed through a filter, amplified to bird intermediate frequency, and detected to generate a low-frequency signal. get. On the other hand, the signal obtained at the intermediate frequency amplification stage is detected by a level detector 9, and a sweep stop signal is obtained from this detection signal.

FIG. 2 shows the case of an FM receiver, in which a center potential signal of a demodulated signal obtained from a wave detector 7 is detected by a center detector 10 to obtain a sweep stop signal.

The stop signals produced by these methods depend on the selectivity characteristics of the intermediate frequency amplification stage and the frequency stability of the center potential of the FM demodulator, and have the drawbacks of false stopping and unstable accuracy.

In the present invention, we do not consider the level or center potential,
The aim is to provide an extremely effective sweep receiver that employs a frequency-based detection method and can avoid erroneous stoppages and unstable accuracy.

FIG. 3 shows an embodiment of the invention. In FIG. 3, 1 is an antenna, 12 is a high frequency amplifier, 13 is a frequency conversion mixer, 14 is a filter, 15 is an intermediate frequency amplifier, and 16 is a detector, through which a low frequency signal is obtained. On the other hand, to explain the local oscillation circuit using one type of PLL synthesizer, 7 is a crystal oscillator, 18 is a variable frequency voltage crystal oscillator circuit, 19 is a frequency step-down device, and 20 is a phase comparator, which divides the oscillation output of vC023. The phase of the frequency component divided by the frequency component 2 and the one frequency component of the water crystal oscillation circuit is compared, and this output controls the VCO, locking the VCO 23 into the oscillation frequency signal of the crystal oscillation circuit. The first PLL in Korera
It consists of Further, the phase comparator 27 is configured to measure 1/m of the intermediate frequency signal generated when the receiver receives the signal.
A second PLL is configured which compares the phase of the component and 1/p of the reference signal generated in the crystal oscillation circuit, and locks the crystal oscillation circuit into the intermediate frequency. When this second PLL section locks in, a lock-in signal is generated through the phase comparator 28. By extracting this signal as a sweep stop signal, the sweep operation is stopped. Thereafter, the variable section of the crystal oscillator is stopped, and the reference frequency of the first pLL section returns to the initial oscillation frequency, allowing correct reception. Note that 24 is a buffer, and 29 is a low-pass filter.

As described above, according to the present invention, the sweep stop signal is obtained by locking in the crystal oscillation circuit using the intermediate frequency component, so that the selection characteristics of the conventional intermediate frequency amplification stage,
A sweep receiver can be obtained that is independent of the frequency stability of the center potential of the FM demodulator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a circuit for obtaining a sweep stop signal in a conventional AM receiver, FIG. 2 is a block diagram of a circuit for obtaining a sweep stop signal in a conventional FM receiver, and FIG. 3 is a block diagram of a circuit for obtaining a sweep stop signal in a conventional FM receiver. FIG. 2 is a circuit block diagram of a receiver. 11・・・・・・・・・Antenna, 12・・・・・・・・・
...High frequency amplifier, 13...Mixer, 1
4...Filter, 15...
...Intermediate frequency amplifier, 16......Detector,
17......Crystal oscillator, 18...
...Crystal oscillator circuit, 19... Frequency downgrader, 20, 27.28... Phase comparator, 21... Frequency divider, 22.29...
...Low pass filter p-123...
・■C0124・・・・・・・・・ノ(Nofa, 25.
26・・・・・・・・・Divider.

Claims (1)

[Claims] In a sweep receiver that uses one type of PLL synthesizer as a local oscillation circuit and performs step reception, the reference oscillation circuit constituting the first PLL is configured with a frequency voltage variable crystal oscillation circuit, and the reference oscillation circuit is configured with an intermediate frequency A second PLL that locks in to a signal is constructed by sharing the reference oscillation circuit of the first PLL, and the reference oscillation circuit is locked in by locking in to an intermediate frequency signal generated by receiving radio waves. A sweep receiver characterized in that it obtains an in signal and obtains a sweep stop signal.