JPS59161924A - Phase synchronizing oscillator - Google Patents

Abstract

PURPOSE:To shift the input wave phase of a phase comparator in order to shorten the time during which the switched frequency and phase are stabilized in a steady state, by providing a variable phase shifter and a control circuit. CONSTITUTION:The input frequency of an input terminal 10 changes to fi2 from fi1 and the phase jumps by DELTAtheta when the frequency of the input signal of the terminal 10 of a variable phase shifter 8 is set at t=0. Then a control signal which shifts the phase of the shifter 8 by DELTAphi=theta2-theta1-DELTAtheta at t=0 is transmitted to the shifter 8 from a control circuit 9 on the basis of the switch information given from an input terminal 15. The shifter 8 shift the phase of the input signal by DELTAphi. Thus an input terminal 11 receives a signal whose frequency changes to fi2 from fi1 with the phase jump set at DELTAtheta12=DELTAphi+DELTAtheta=theta2-theta1. As a result, the steady phase difference theta2 corresponding to fi2 is obtained at the output of a phase comparator 1. Then the frequency of a VCO2 is instantaneously stabilized at fi2.

Description

Detailed Description of the Invention (Technical Field) The present invention provides a phase locked oscillator (PLO) in a short time when the frequency and/or phase of one or both of two input signals of a phase comparator is switched. The present invention relates to a first-order loop phase-locked oscillator configured to transition to a steady state.

(Background Art) The PLO in the primary loop is conventionally shown in Fig. 1(a), (
b) It was structured as follows. In this figure, 1 is a phase comparator, 2 is a voltage controlled oscillator (VCO), terminals 3 and 4 are input terminals of the phase comparator, 5 is an output terminal of the phase comparator, 6 is an output terminal of the VCO, and 7 is a divider. It is a peripheral organ. These PLOs
When the frequency of the input signal of one or both of the input terminals 3 and 4 of the phase comparator suddenly changes (an example of a change in the input frequency of the input terminal 40 is when the input frequency of the frequency divider 7 changes due to an external control signal). If the division ratio is suddenly changed and VC
By changing the center frequency of O, the input voltage may shift the oscillation frequency characteristics, etc.), this P
Immediately after the LO is switched, it goes through a certain transient state and then settles into a steady state. For example, in the circuit of FIG. 1(a), when the frequency of the input signal at the input terminal 30 of the phase comparator switches from fl1 to ft2 at time t=Q, the input phase difference θ of the phase comparator, the output ■, Instantaneous oscillation frequency fv of VCO2
is as shown in FIG. 1(C). Here, θ5. ■1 is the phase comparator 1 when the input frequency of terminal 3 is 7'i1
Steady phase difference and output voltage at 0 input, θ2. ■2
Similarly, is the steady phase difference and output voltage when the input frequency is f12. Also, transient state A.

B and C are from ft+ to f1 when the input frequency is 1=00.
The phase jump of ft2 when switching to 2 is ΔθA
.

0, ΔθC, ΔVA, ΔfA and ΔW, Δ
fc is Δθ at time t=Q. and Δθ. The jump in the phase comparator output corresponding to , and the jump in the instantaneous frequency of vCO are shown. The characteristics of the phase comparator are shown in Figure 1(d).
It is assumed that the phase difference of the input signal repeats the characteristic of a tooth-like waveform every 2π as shown in , and the characteristic of the VCO is
It is assumed that the output voltage changes linearly with respect to the input voltage as shown in Figure (e). Changes in the input phase difference θ of the phase comparator, the output voltage ■, and the instantaneous oscillation frequency fv of the VCO when 1>0 in FIG. 1(C) are expressed by the following equation.

0-02-(0,,-'0.-AD)e"V=V,,-
(v2-v, -Δ■)e-ktfv=fi2(ftz-
fal-Δf)e-kt where Δθ, ΔV, Δf are 1=
indicates the amount of jump of θ + V + fV at 0,
K is the sensitivity of the phase comparator and VCO, respectively θ(V/
rad) 1. Ky(6)/V) is the loop gain expressed as θKv.

In this way, the instantaneous oscillation frequency of the VCO when the input frequency or input phase is switched passes through a transient state that can be expressed as an exponential curve with a time constant of 1/, as shown in Figure 1(a). , There is a drawback that this transient state cannot be shortened if the configuration of (b) is used as is.

The above explanation has been given for the case where the frequency and phase at the input terminal 3 of the phase comparator change in FIG. 1(a) or (b), but also when the frequency at the input terminal 4 side changes. The state of the transient change until it stabilizes to a steady state is almost the same as the above explanation.

(Problem to be solved by the invention) In order to eliminate these drawbacks, the present invention shifts the phase of the input wave of the phase comparator in order to eliminate or shorten the transient state that accompanies frequency and phase switching. will be explained in detail.

(Structure and operation of the invention) FIG. 2(a) shows an embodiment of the present invention, in which 1 is a phase comparator, 2 is a VCO 18 is a variable phase shifter, 9 is a control circuit, and 10 is an input of the variable phase shifter. Terminal, 11. , 12 is the input terminal of the phase comparator, 13 is the output terminal of the phase comparator, 14 is the VCO
15 is an input terminal of the control circuit, and 16 is an output terminal. In this figure, now phase comparator 1 and VC
It is assumed that O2 has the same characteristics as in FIG. 1(d) and (el).The operation in this example is shown in FIG.
Explain according to (d). In the same figure (bl is the signal at the phase comparator input terminal 11, (C) is the signal at 12, (
d) shows the signal at the phase comparator output. In these figures, if the input frequency of the input terminal 100 jumps from ft1 to ft2 and the phase jumps by Δθ at time t=Q (corresponding to Y in FIG. 2(b)), then the control circuit 9 inputs Based on the frequency and phase switching information from the terminal 15, a control signal is sent to the variable phase shifter 8 to phase shift the phase shifter by the next phase shift amount Δφ at time t,=Q. do.

Δφ=θ2-θ1-Δθ However, θ2 is the steady phase difference at the input of the phase comparator 10 when the input frequency is ft2, and θ is the steady phase difference at the same (fl. The phase of the input signal is shifted by Δφ.As a result, as shown in FIG.
A signal resulting in a phase jump of Δθ12 at this time is added (corresponding to Z in FIG. 2(b)). Here Δ
θ, 2 is Δθ1□=Δφ+Δθ=θ2−θ.

Therefore, as shown in FIG. 2(d), the steady phase error θ2 corresponding to the input frequency fi2 is obtained at the time of j=Q at the output of the phase comparator. As a result, the instantaneous frequency of the VCO does not go through a transition period (at time t=Q, it instantaneously stabilizes at the new frequency fiz, and the switching is completed.

FIG. 3 shows another embodiment in which the variable phase shifter 8 in FIG. 2 is placed on the input terminal 12 side of the phase comparator 10. In this example, if there is a frequency switch and a phase jump at the input terminal 11 similar to those shown in FIG. It is clear that this PLO can be instantaneously pulled into a new frequency, and that the same effect as the configuration shown in FIG. 2(a) can be obtained.

Figure 4 shows other examples of 1.2, 8, 9, 10, 11, 1.
2, 1.3, 14゜15, 16 are the same as in Figure 2, 1
7 is a variable frequency divider, and 18 is its control input. In this embodiment, a signal from a fixed reference oscillator is input to the input terminal 10, and the oscillation frequency of the VCO is changed by changing the division ratio of the frequency divider 17. A phase shifter 8 is used to shorten the switching time. In other words, when changing the division ratio of the frequency divider 17 in order to change the CO output frequency,
Although the input frequency of the phase comparator 12 tends to change temporarily, this change is canceled by controlling the amount of phase shift of the variable phase shifter 8, and the switching time is shortened. The basic operating principle is almost the same as described above.

In other words, by switching the division ratio of the frequency divider, 1=0
At time 0, the input frequency of input terminal 120 changes from fll to f+2.
When the phase shifts to Δθ with a phase jump, the transient change accompanying the switching can be canceled by shifting the variable phase shifter by the phase shift amount Δφ.

It is clear that even in this embodiment, the same effect can be obtained even if the variable phase shifter 8 is placed on the input end 12 side of the phase comparator.

In the present invention, the case where the variable phase shifter is inserted just before the phase comparator is shown, but if a predetermined phase change is obtained at the input of the phase comparator, the insertion point, variable amount, and type of the variable phase shifter can be changed. It is clear that it does not matter what it is (for example, if a mixer is used between the VCO 2 and the frequency divider 17 in Figure 4, or on the CO output side or the phase comparator side, the local oscillator) output side, etc.).

In this embodiment, the input signals in FIGS. 2(b) and 2(C) are sinusoidal waves, but it is clear that the present invention can be applied to other types of signals, such as pulsed signals.

In this example, the characteristics of the phase comparator and the characteristics of the VCO are assumed to be as shown in Figure 1 (d) and (e), but other shapes can also be used with variable phase shift. It is clear that the present invention can be applied by controlling the amount of phase shift of the device.

In the present invention, even if there is a slight deviation in the phase switching point of the variable phase shifter, by adjusting the amount of phase shift according to the deviation, it is possible to secure entry into the new station wave number and phase in a short time. can.

(Effects of the Invention) As explained above, by using the method of the present invention, it is possible to shorten the time required to stabilize the steady state when the frequency and phase in the -order loop PLO are switched, thereby eliminating the need for high-speed switching. If applied to a frequency synthesizer, etc., the advantage is that the frequency switching time can be shortened.

[Brief explanation of drawings]

Figures 1 (a) to (e) are explanatory diagrams of the configuration of a conventional primary loop PLO and operating characteristics when switching input frequency; Figure 2 (a)
~(dl is an explanatory diagram of one embodiment of the present invention and its operation, the third
The figures and FIG. 4 show other embodiments of the present invention. 1... Phase comparator, 2... Voltage controlled oscillator ("
VCO), 3 and 4...input terminal of phase comparator, 5.
... Output terminal of phase comparator, 6... Output terminal of VCO, 7... Frequency divider, 8...
Variable phase shifter, 9... Control circuit, 10... Input signal terminal of variable phase shifter, 11.12... Input signal terminal of phase comparator, 13... Output terminal of phase comparator, 14... VCO output terminal, 15... Frequency and phase switching information input terminal, 16...
- Control circuit output terminal, 17... variable frequency divider, 18.
...Input terminal of variable frequency divider. Fig. 2 t7゜----------→----------Y t-0

Claims (1)

[Scope of Claim] A phase-locked oscillator comprising a phase comparator and a voltage-controlled oscillator directly connected to the output thereof, and providing an output phase-synchronized with the output thereof, wherein at least one input of the phase comparator The frequency and phase of the phase comparator are small (when one of them is switched, means is provided for shifting the phase of the input of the phase comparator by approximately (θ2-01-Δθ) according to the switching information. Phase-locked oscillator.