JPH011335A - Transmitter with noise prevention circuit - 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 Field of the Invention The present invention relates to transmitters, and more particularly to transmitters that use digital phase comparators for frequency stabilization.

[Conventional technology] Conventionally, this pillar transmitter has been designed to stabilize the frequency by
For example, an automatic phase control circuit (AI) and an automatic frequency control circuit (AFC) are used.

Figure 2 shows an example of a conventional A))C type transmitter, in which 4 is a voltage controlled oscillator <V
CO), 5 is a frequency divider, 6 is a digital phase comparator, 7
is a reference frequency generator, 8 is a low-pass filter (LPF)
, 9 is a mixer, 10 is a high frequency amplifier, and 11 is a local oscillator.

This transmitter uses a frequency divider 5 to divide the frequency of the output signal of the VCO 4 to a frequency that allows phase comparison, and inputs the frequency to a digital phase comparator 6.

The digital phase comparator 6 compares the phases of this frequency-divided signal and the signal from the reference frequency generator 7, and outputs the ratio axis signal as L.
11F8 to control the output of VCO4 and stabilize the frequency of the oscillator.

[Problems to be Solved] However, in the conventional transmitter, when the power is turned on, the oscillation frequency of the VCo 4 rises from a place far from the center and is drawn in over several seconds to several seconds.

In this process, 1. Since the digital phase comparator 6 does not output a continuous pulse signal, but outputs a stepwise pulse No. 13 with a different duty, L))F
8 cannot sufficiently absorb this stepwise pulse signal and outputs it to the VCo 4 while containing noise components.

Due to this noise component, an FM modulated signal is output from the VCo 4, and this is observed as noise on the receiving side.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a transmitter with a noise generation prevention circuit that does not generate noise when power is turned on.

Means for Solving Problems 1 To achieve the above object, the present invention provides the following features: In a transmitter that uses a digital phase comparator for stabilizing the transmission output frequency, the present invention detects noise generated from the digital phase comparator when the power is turned on. APC voltage determination circuit.

The configuration includes a delay switching circuit that starts transmission after a predetermined delay time has elapsed after noise generation ends when the power is turned on.

"Embodiments" Next, preferred embodiments of the present invention will be described based on the drawings. Note that the same reference numerals are given to the members corresponding to those of the conventional device shown in FIG. 2, and the explanation thereof will be omitted.

FIG. 1 shows a preferred embodiment of a transmitter with a noise prevention circuit according to the present invention.

The transmitter of this embodiment is provided with an APC voltage determination circuit 1, a delay circuit 2, and a switch 3.

Then, the APC voltage determination circuit 1 determines whether the VCO control voltage output from the LPF 8 is normal or abnormal, and outputs a signal of [1] when normal and "0" when abnormal to the delay circuit 2. .

The delay circuit 2 controls the switch 3 to oven until the APC voltage becomes normal and the frequency is completely locked. Further, even if the APC control voltage indicates an abnormality, the switch 3 is immediately controlled to the oven.

In other words, for a certain period of time after the power is turned on, A P
Since the C control voltage indicates an abnormality, the APC voltage determination circuit 1 sends a logic signal of "0" to the delay circuit 2.

The delay circuit 2 immediately controls the switch 3 to open when a logic signal of "0" is input.

Next, when the APC control voltage becomes a normal value, the APC voltage determination circuit 1 generates a logic signal of 111 I+, and the delay circuit 2 generates a signal after the delay time required for the transmission output frequency to be locked. , turns on the switch 3.

Effects of the Invention-1 As explained above, according to the present invention, when the power is turned on,
This has the effect of providing a transmitter that does not generate noise even if the oscillation frequency of the VCO rises from a location far from the center.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an embodiment of an APC frequency stabilization transmitter according to the present invention, and FIG. 2 is a block circuit diagram of a conventional APC frequency stabilization transmitter.
FIG. 2 is a block circuit diagram illustrating a C frequency stabilization transmitter. 1: APC voltage judgment circuit 2: Delay circuit 3: Switch 4: VCo 5: Frequency divider 6: Phase comparator 7: Reference frequency generator 8: LPF 9: Mixer 10: High frequency amplifier 11: Local oscillator agent Patent attorney Yoshi Watanabe Hirahaku Figure 1 Figure 2

Claims (1)

[Claims] In a transmitter that uses a digital phase comparator to stabilize the transmission output frequency, there is provided an APC voltage determination circuit that detects noise generated from the digital phase comparator when power is turned on; A transmitter with a noise generation prevention circuit, comprising: a delay switch circuit that starts transmission after a predetermined delay time has elapsed after the generation ends;