Phase signal filtering apparatus utilizing estimated phase signal

• US 4,939,751 A
• Filed: 10/13/1988
• Issued: 07/03/1990
• Est. Priority Date: 10/23/1987
• Status: Expired due to Fees

• Current Assignee: Anritsu Corporation
• Original Assignee: Anritsu Corporation
• Inventors: Kuroda, Masahiro
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Chin, Stephen
• Application Number:
  US07/257,326
• Time in Patent Office: 628 Days
• Field of Search: 375/80, 375/82, 375/87, 375/95, 375/110, 375/119, 375/120, 331/10-14, 331/17, 331/25, 455/260, 343/352, 343/357, 343/396, 364/446, 364/458, 370/104
• US Class Current: 375/324
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: H03L 7/08 Details of the phase-locked loop

Abstract

A phase signal estimator receives a first phase signal having a first frequency and generates a first filtered signal phase-locked with the first phase signal as an estimated phase signal. A phase locked loop section receives a second phase signal having a second frequency which corresponds to a predetermined multiple of the first frequency of the first phase signal, and outputs a second filtered signal phase-locked with the second phase signal as a desired phase signal. In the phase locked loop section, a phase comparator receives the second phase signal and the desired phase signal and generates a phase difference signal. A filter low-pass filters the phase difference signal from the phase comparator. A signal generator generates a signal having a predetermined frequency in accordance with the output from the filter. A phase adder adds the signal having the predetermined frequency from the signal generator and the estimated phase signal from the phase signal estimator and outputs the desired phase signal. A frequency compensator is selectively connected to the estimated phase signal, the second phase signal, and the desired phase signal so that the phase locked loop section has sustantially the same low-pass filtering response characteristic as the first frequency of the first phase signal.

Claims

1. A phase signal filtering apparatus, comprising:

phase signal estimation means for receiving a first phase signal having a first frequency and for generating a first filtered signal phase-locked with the first phase signal as an estimated phase signal;

phase locked loop means for receiving a second phase signal having a second frequency which corresponds to a predetermined multiple of the first frequency of the first phase signal, and for outputting a second filtered signal phase-locked with the second phase signal as a desired phase signal, said phase lock means comprising;

phase comparator means for receiving the second phase signal and the desired phase signal, and for generating a phase difference signal;

filtering means for low-pass filtering the phase difference signal from said phase comparator means;

signal generating means for generating a signal having a predetermined frequency in accordance with the output from said filtering means; and

phase adder means for adding the signal having the predetermined frequency from said signal generating means and the estimated phase signal from said phase signal estimation means, and for outputting the desired phase signal; and

means connected to at least one of the estimated phase signal, the second phase signal, and the desired phase signal, for controlling said phase locked loop means to have substantially the same low-pass filtering response characteristic as the first frequency of the first phase signal;

wherein a ratio of the first and the second frequencies is a ratio of integers N₁ and N₂ ; and

said means for controlling includes frequency divider /multiplier means connected to an output section of said phase signal estimation means for causing said phase signal estimation means to output the estimated phase signal having a frequency N₂ /N₁ times the frequency of the first filtered signal.

2. An apparatus according to claim 1, wherein said phase signal estimation means comprises a phase locked loop having a low-phase filtering response characteristic.

3. An apparatus according to claim 1, wherein a ration of the first and second frequencies is selected to be 10 or more.

4. A phase signal filtering apparatus for receiving first and second input signals, a ratio of frequencies of which is a ratio of integers N₁ and N₂, and filtering the second input signal to obtain an output the generated signal, comprising:

a phase signal estimator for receiving the first input signal and generating a filtered signal phase-locked with the first input signal;

a first frequency divider/multiplier for receiving the filtered signal and generating an estimated phase signal having a frequency N₂ /N₁ times the frequency of the filtered signal;

a phase comparator for receiving the second input signal and the output signal and forming a phase difference signal;

a filter for low-pass filtering the phase difference signal;

a signal generator for generating a signal having a frequency proportional to the output from said filter; and

a phase adder for adding phases of the signal having a proportional frequency and the estimated phase signal so as to output said output signal.

5. An apparatus according to claim 4, wherein said apparatus further comprises a first phase/complex signal converter for converting a phase of the first input signal into a complex signal, and sending the converted complex signal to said phase signal estimator, and sceond phase/complex signal converter for converting a phase of the second input signal into a complex signal and sending the converted complex signal to said phase comparator, and the compared signal is filtered to obtain an output complex signal.

6. A phase signal filtering apparatus for receiving first and second input signals, a ratio of frequencies of which is a ratio of integers N₁ and N₂, and filtering the second input signal to obtain an output signal comprising:

a phase signal estimator for receiving the first input signal and generating a filtered signal phase-locked with the first input signal;

a first frequency divider for receiving the filtered signal and generating an estimated phase signal having a frequency 1/N₁ the frequency of the filtered signal;

a second frequency divider for receiving the second input signal and generating a first phase signal having a frequency 1/N₂ the frequency of the second input signal;

a phase comparator for receiving the first phase signal and a second phase signal for forming a phase difference signal;

a filter for low-phase filtering the phase difference signal;

a signal generator for generating a signal having a frequency proportional to the output from said filter;

a phase adder for adding phases of the generated signal having a proportional frequency and the estimated phase signal so as to output the second phase signal; and

a multiplier for receiving the second phase signal and generating the output signal having a frequency N₂ times the frequency of the second phase signal.

7. An apparatus according to claim 6, wherein said apparatus further comprises a first phase/complex signal converter for converting a phase of the first input signal into a complex signal, and sending the converted complex signal to said phase signal estimator, and a second phase/complex signal converter for converting a phase of the second input signal into a complex signal and sending the converted complex signal to said phase comparator, and the compared signal is filtered to obtain an output complex signal.

8. A phase signal filtering apparatus for receiving first and second input signals, a ratio of frequencies of which is a ratio of integers N₁ and N₂, and filtering the second input signal to obtain an output the generated signal, comprising:

an phase signal estimator for receiving the first input signal and generating an estimated phase signal phase-locked with the first input signal;

a first frequency divider/multiplier for receiving the second input signal and generating a first phase signal having a frequency N₁ /N₂ times the frequency of the second input signal;

a phase comparator for receving the first phase signal and a second phase signal and forming a phase difference signal;

a filter for low-pass filtering the phase difference signal;

a signal generator for generating a signal having a frequency proportional to the outut from said filter;

a phase adder for adding phases of the signal having the proportional frequency and the estimated phase signal so as to output the second phase signal; and

a second frequency divider/multplier for receiving the second phase signal and generating the output signal having a frequency N₂ /N₁ times the frequency of the second phase signal.

9. An apparatus according to claim 8, wherein said apparatus further comprises a first phase/complex signal converter for converting a phase of the first input signal into a complex signal, and sending the converted complex signal to said phase signal estimator, and a second phase/complex signal converter for converting a phase of the second input signal into a complex signal and sending the converted complex signal to said phase comparator, and the compared signal is filtered to obtain an output complex signal.

10. A GPS (Global Positioning System) signal PLL phase locked loop filtering apparatus serving as a pre-filtering apparatus used in a GPS receiver which receives three phase signals ψ

_C/A (t), ψ

_p (t), and ψ

_CAR (t) which are sent from a GPS satellite and are related by;

##EQU3## and processes the three phase signals to perform positioning or ranging measurement, comprising;

a phase/complex signal converter for receiving the phase signal ψ

_C/A (t) and generating a (1a)th complex signal ε

^jψ

.sbsp.C/A.sup.(t) ;

a first phase comparator including means for receiving the (1a)th complex signal and a (1b)th complex signal ε

^-jψ

.sbsp.C/A.sup.(t) and generating a phase difference signal ψ

d₁ '"'"'(t) calculated by equations (2) from a phase component ψ

_C/A (t)- ψ

_C/A (t) of a product ε

^j{ψ

.sbsp.C/A.sup.(t)-ψ

.sbsp.C/A.sup.(t)} of the (1a)th and (1b)th complex signals;

##EQU4## a first loop filter for receiving the phase difference signal ψ

d₁ '"'"'(t) and generating a first oscillation frequency control signal;

a first voltage controlled oscillator for receiving the first oscillation frequency control signal and generating a first phase continuous signal having a frequency proportional to the first oscillation frequency control signal;

a first frequency divider for receiving and frequency dividing the first phase continuous signal to generate a first complex signal ε

^jψ

.sbsp.C/A.sup.(t) ;

a first conjugate complex operator for receiving the first complex signal ε

^jψ

.sbsp.C/A.sup.(t) and generating the (1b)th complex signal ε

^-jψ

.sbsp._C/A.sup.(t) conjugate therewith;

a second phase/complex signal converter for receiving the phase signal ψ

p(t) and generating a (2a)th complex signal ε

jψ

p(t);

a second phase comparator including means for receiving the (2a)th complex signal and a (2b)th complex signal ε

^-j ψ

p(t) and generating a phase difference signal ψ

_d2 '"'"'(t) calculated by equations (3) from a phase component ψ

_p (t)-ψ

_p (t) of a product ε

^j{ψ

.sbsp.p.sup.(t)-ψ

.sbsp.p.sup.(t)} of the (2a)th and (2b)th complex signals;

##EQU5## a second loop filter for receiving the phase difference signal ψ

_d2 '"'"'(t) and generating a second oscillation frequency control signal;

a second voltage controlled oscillator for receiving the second oscillation frequency control signal and generating a second phase continuous signal having a frequency proportional to the second oscillation frequency control signal;

a first phase adder for receiving the first and second phase continuous signals and generating a first sum signal of the two signals;

a second frequency divider for receiving a frequency dividing the first sum signal to generate a second complex signal ε

^jψ

.sbsp.p.sup.(t) ;

a second conjugate complex operator for receiving the second complex signal ε

^jψ

.sbsp.p.sup.(t) and generating the (2b)th complex signal ε

^-jψ

.sbsp.p.sup.(t) conjugated therewith;

a third phase/complex signal converter for receiving the phase signal ψ

_C/A (t) and generating a (3a)th complex signal ε

^jψ

.sbsp.CAR.sup.(t) ;

a third phase comparator including means for receiving the (3a)th complex signal and a (3b)th complex signal ε

^-jψ

.sbsp.CAR.sup.(t) and generating a phase difference signal ψ

d₃ '"'"'(t) calculated by equations (4) from a phase component ψ

_CAR (t)-ψ

_CAR (t) of a product ε

j{ψ

_CAR (t)-ψ

_CAR (t)} of the (3a)th and (3b)th complex signals;

##EQU6## a third loop filter for receiving the phase difference signal ψ

_d3 '"'"'(t) and generating a third oscillation frequency control signal;

a third voltage controlled oscillator for receiving the third oscillation frequency control signal and generating a third phase continuous signal having a frequency proportional to the third oscillation frequency control signal;

a second phase adder for receiving the second and third phase continuous signals and generating a second sum signal of the two signals; and

a third conjugate complex operator receiving the second sum signal and generating the (3b)th complex signal ε

^-jψ

CAR.sup.(t) conjugated therewith.

11. A phase signal filtering apparatus, comprising:

phase signal estimation means for receiving a first phase signal having a first frequency and for generating a first filtered signal phase-locked with the first phase signal as an estimated phase signal;

phase locked loop means for receiving a second phase signal having a second frequency which corresponds to a predetermined multiple of the first frequency of the first phase signal, and for outputting a second filtered signal phase-locked with the second phase signal as a desired phase signal, said phase lock loop means comprising;

phase comparator means for receiving the second phase signal and the desired phase signal, and for generating a phase difference signal;

filtering means for low-pass filtering the phase difference signal from said phase comparator means;

signal generating means for generating a signal having a predetermined frequency in accordance with the output from said filtering means; and

phase adder means for adding the signal having the predetermined frequency from said signal generating means and the estimated phase signal from said phase signal estimation means, and for outputting the desired phase signal; and

means connected to at least one of the estimated phase signal, the second phase signal, and the desired phase signal, for controlling said phase locked loop means to have substantially the same low-pass filtering response characteristic as the first frequency of the first phase signal;

wherein a ratio of the first and the second frequencies is a ratio of integers N₁ and N₂ ; and

said means for controlling includes

first frequency divider/multiplier means connected to an output section of said phase signal estimation means, for causing said phase signal estimation means to output the estimated phase signal having a frequency 1/N₁ the frequency of the first filtered signal,

second frequency divider means, connected to an input section of the second phase signal, for frequency dividing the frequency of the second phase signal to 1/N₂, and

multiplier means, connected to an output section of said phase adder means, for outputting the desired phase signal having a frequency N₂ times the frequency of the second filtered signal.

12. A phase signal filtering apparatus, comprising:

phase signal estimation means for receiving a first phase signal having a first frequency and for generating a first filtered signal phase-locked with the first phase signal as an estimated phase signal;

phase locked loop means for receiving a second phase signal having a second frequency which corresponds to a predetermined multiple of the first frequency of the first phase signal, and for outputting a second filtered signal phase-locked with the second phase signal as a desired phase signal, said phase lock loop means comprising;

phase comparator means for receiving the second phase signal and the desired phase signal, and for generating a phase difference signal;

filtering means for low-pass filtering the phase difference signal from said phase comparator means;

signal generating means for generating a signal having a predetermined frequency in accordance with the output from said filtering means; and

phase adder means for adding the signal having the predetermined frequency from said signal generating means and the estimated phase signal from said phase signal estimation means, and for outputting the desired phase signal; and

means connected to at lease one of the estimated phase signal, the second phase signal, and the desired phase signal, for controlling said phase locked loop means to have substantially the same low-pass filtering response characteristic as the first frequency of the first phase signal;

wherein a ratio of the first and the second frequencies is a ratio of integers N₁ and N₂ ; and

said means for controlling includes

first frequency divider/multiplier means, connected to an input section of the phase locked loop means, for frequency dividing/multiplying the frequency of the second phase signal by N₁ /N₂, and

second frequency divider/multiplier means, connected to an output section of the phase adder means, for frequency dividing/multiplying the frequency of the second filtered signal N₂ /N₁.