Signal injection for calibration of pseudo-range errors in satellite positioning system receivers

• US 5,949,372 A
• Filed: 10/03/1997
• Issued: 09/07/1999
• Est. Priority Date: 10/03/1997
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Lennen, Gary R.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/943,656
• Time in Patent Office: 704 Days
• Field of Search: 342/357, 342/357.02, 342/357.12, 701/213, 701/214
• US Class Current: 342/357.62
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements

Abstract

The present invention discloses the apparatus and the methods for calibrating a Narrow Band receiver for the group delay code phase errors. The group delay code phase errors are caused by group delay variations in the satellite signals being transmitted by a Narrow Band satellite Transmitter. A Calibration generator circuit generates a calibration signal that is substantially similar to the satellite signal but is free from the group delay variations. The calibration signal is used by the Narrow Band satellite Receiver to measure and eliminate the code phase group delay errors.

Claims

1. An apparatus for calibrating a Narrow Band satellite Receiver for group delay errors in a satellite signal;

said apparatus comprising;

a Narrow Band satellite Receiver circuit configured to receive said satellite signal;

and

a Calibration circuit configured to generate a calibration signal;

wherein said calibration signal is used to calibrate said Narrow Band satellite Receiver circuit for pseudo-range errors caused by variations in the group delay of said received satellite signal across the received bandwidth.

2. The apparatus of claim 1;

wherein said Narrow Band Receiver circuit further includes;

a Receiver Antenna circuit for receiving said satellite signal.

3. The apparatus of claim 1;

wherein said Narrow Band Receiver circuit further includes;

a Temperature Sensor.

4. The apparatus of claim 2, wherein said Calibration circuit further includes:

a Calibration Signal Generator circuit configured to generate said calibration signal.

5. The apparatus of claim 2, wherein said Calibration circuit further includes:

a Calibration Signal Generator circuit configured to generate said calibration signal; and

a Directional Coupler circuit connected to said Calibration Signal Generator circuit in order to receive said calibration signal and connected to said Receiver Antenna circuit in order to receive said satellite signal;

wherein said Directional Coupler is configured to combine said satellite signals with said calibration signal in order to generate a combined signal and in order to inject said combined signal into said Narrow Band satellite Receiver circuit.

6. The apparatus of claim 2, wherein said Calibration circuit further includes:

a Calibration Signal Generator circuit configured to generate said calibration signal;

a Power Combiner circuit connected to said Calibration Signal Generator circuit; and

a Calibration Antenna circuit connected to said Power Combiner Circuit;

wherein said Calibration Antenna is configured to transmit said calibration signal to said Receiver Antenna.

7. The apparatus of claim 2, wherein said Receiver Antenna receives said satellite signals from the GPS system including a plurality of GPS satellites and from the GLONASS system including a plurality of GLONASS satellites, and wherein the GPS system generates L1_GPS and L2_GPS signals, wherein said GLONASS system generates L1_GLONASS and L2_GLONASS signals;

and wherein said Receiver circuit further includes;

a Filter/LNA circuit conductively connected to said Receiver Antenna, wherein said Filter/LNA is configured to perform the filtering and low noise amplification of said L1_GPS, L2_GPS, L1_GLONASS, and L2_GLONASS signals;

wherein said Filter/LNA determines the signal-to-noise (SNR) ratio of the received signals;

a Downconverter circuit conductively connected to said Filter/LNA, wherein said Downconverter is configured to convert down in frequency said L1_GPS, L2_GPS, L1_GLONASS, and L2_GLONASS signals;

an IF processor conductively connected to said Downconverter, wherein said IF processor is configured to further frequency translate and digitize said L1_GPS, L2_GPS, L1_GLONASS, and L2_GLONASS signals;

a plurality of Digital Channel Processor circuits connected to said Receiver circuit, wherein each said Digital Channel Processor is configured to process satellite signals emanating from a single satellite; and

a Microprocessor connected to each said Digital Channel Processor, wherein said Microprocessor is configured to generate control signals and is configured to extract the navigational information from each said received satellite signal.

8. The apparatus of claim 7 further comprising a Master Oscillator block configured to generate a single clock frequency MASTER_-- CLK, a GPS clock frequency OSC_GPS, a GLONASS clock frequency OSC_GLONASS, and a calibration clock frequency OSC_CAL, wherein said GPS clock frequency OSC_GPS, said GLONASS clock frequency OSC_GLONASS, and said calibration clock frequency OSC_CAL are all derived from said single clock frequency MASTER_-- CLK.

9. The apparatus of claim 8 further comprising a Frequency Synthesizer connected to said Master Oscillator, wherein said Frequency Synthesizer is configured to synthesize L0₁, L0₂, L0₃, L0₄, msec, and sclk clock signals.

10. The apparatus of claim 4, wherein said Calibration Signal Generator further comprises:

a Calibration Signal Synthesizer configured to generate a code clock signal C_clk.sbsb.--_GLONASS, a code clock signal C_clk.sbsb.--_GPS, a local oscillator signal L0_L1.sbsb.--_GLONASS, a local oscillator signal L0_L2.sbsb.--_GLONASS, a local oscillator signal L0_L1.sbsb.--_GPS, and a local oscillator signal L0_L2.sbsb.--_GPS, wherein said code clock signal C_clk.sbsb.--_GLONASS, said code clock signal C_clk.sbsb.--_GPS, said local oscillator signal L0_L1.sbsb.--_GLONASS, said local oscillator signal L0_L2.sbsb.--_GLONASS, said local oscillator signal L0_L1.sbsb.--_GPS, and said local oscillator signal L0_L2.sbsb.--_GPS are locked to said calibration clock frequency OSC_CAL signal under control of a Microprocessor;

a Calibration Code Generator connected to said Calibration Signal Synthesizer, wherein said Calibration Code Generator is configured to generate a local code C_GLONASS and a local code C_GPS ;

a Mixer connected to said Calibration Signal Synthesizer and connected to said Calibration Code Generator, wherein said Mixer is configured to frequency translate said local code C_GLONASS signal using said L0_L1.sbsb.--_GLONASS signal into an L1_-- GLONASS signal, said local code C_GLONASS signal using said L0_L2.sbsb.--_GLONASS signal into an L2_-- GLONASS signal, said local code C_GPS signal using said L0_L1.sbsb.--_GPS signal into an L1_-- GPS signal, and said local code C_GPS signal using said L0_L2.sbsb.--_GPS signal into an L2_-- GPS signal;

an RF Switch block coupled to said Mixer, wherein said RF Switch block is configured to pass said L1_-- GLONASS signal, said L2_-- GLONASS signal, said L1_-- GPS signal, or said L2_-- GPS signal under the control of said Microprocessor;

and

an Attenuator block connected to said RF Switch block, wherein said Attenuator is configured to generate a calibration signal C_RF.sbsb.--_GLONASS.sbsb.--_L1, a calibration signal C_RF.sbsb.--_GLONASS.sbsb.--_L2, a calibration signal C_RF.sbsb.--_GPS.sbsb.--_L1, or a calibration signal C_RF.sbsb.--_GPS.sbsb.--_L2.

11. The apparatus of claim 10, wherein said Calibration Code Generator further comprises:

a Divide-by-10 block configured to divide said GLONASS calibration signal C_clk.sbsb.--_GLONASS, or said GPS calibration signal C_clK.sbsb.--_GPS in order to generate a C_clk.sbsb.--_P.sbsb.--_GLONASS clock signal, a C_clk.sbsb.--_C/A.sbsb.--_GLONASS clock signal, a C_clk.sbsb.--_P.sbsb.--_GPS clock signal, or a C_clk.sbsb.--_C/A.sbsb._GPS clock signal;

a Multiplexer 1 connected to said Divide-by-10 block, wherein said Multiplexer 1 block is configured to select a C_clk.sbsb.--_P.sbsb.--_GLONASS clock signal, a C_clk.sbsb.--_C/A.sbsb.--GLONASS clock signal, a C_clk.sbsb.--_P.sbsb.--_GPS clock signal, or a C_clk.sbsb.--_C/A.sbsb.--_GPS clock signal;

a GPS C/A code generator connected to said Multiplexer 1, wherein said GPS C/A code generator is configured to generate a GPS C/A code signal under the control signal of said Microprocessor μ

P;

a GPS P(Y) code generator connected to said Multiplexer 1, wherein said GPS P(Y) code generator is configured to generate a GPS P(Y) code signal under the control signal of said Microprocessor μ

P;

a GLONASS C/A code generator connected to said Multiplexer 1, wherein said GLONASS C/A code generator is configured to generate a GLONASS C/A code signal under the control signal of said Microprocessor μ

P;

a GLONASS P code generator connected to said Multiplexer 1, wherein said GLONASS P code generator is configured to generate a GLONASS P code signal under the control signal of said Microprocessor μ

P;

an H Code generator connected to said Multiplexer 1, wherein said H code generator is configured to generate an H code signal under the control signal of said Microprocessor μ

P; and

a Multiplexer 2 configured to select a single local code L_C from said GPS C/A, said GPS P(Y), said GLONASS C/A, said GLONASS C/A, or said H locally generated codes.

12. A method of a serial calibration production mode in order to create a database of group delay offsets of the received at temperature T₁ satellite signals emanating from a satellite-vehicle SV_i, a satellite system comprising a plurality of N satellite-vehicles SV_i, N being an integer, i being an integer less or equal to N, said temperature T₁ being within the range of temperatures T₀, T_c !, said method comprising the steps of:

(a) generating a calibration signal by a Calibration Signal Generator;

(b) receiving satellite signals from said satellite-vehicle SV_i by a Receiver including a single Digital Channel Processor;

(c) tracking and measuring said satellite signals at said temperature T₁ to measure a pseudo-range from said Receiver to said satellite-vehicle SV_i ;

(d) tracking and measuring said calibration signal at said temperature T₁ to measure a calibration-pseudo-range from said Receiver to said satellite-vehicle SV_i ;

(e) subtracting for said satellite-vehicle SV_i at said temperature T₁ said calibration-pseudo-range from said pseudo-range to generate a group delay offset G_SVi/T ;

(f) storing said group delay offset G_SVi/T measured at said temperature T₁ for said satellite-vehicle SV_i in a computer memory;

(g) repeating steps (a-f) for each said "i" satellite-vehicle SV_i, i being less or equal to N; and

(h) repeating steps (a-g) for another temperature T₂ within the range of temperatures T₀, T_c !.

13. A method of a real-time serial calibration process in order to remove group delay offsets G_Svi from pseudo-range measurements for satellite signals emanating from a satellite-vehicle SV_i, a satellite system comprising a plurality of N satellite-vehicles SV_i, N being an integer, i being an integer less or equal to N, said method comprising the steps of:

(a) generating a calibration signal by a Calibration Signal Generator;

(b) receiving satellite signals from said satellite-vehicle SV_i by a Receiver including a single Digital Channel Processor;

(c) tracking and measuring said satellite signals to measure a pseudo-range from said Receiver to said satellite-vehicle SV_i ;

(d) tracking and measuring said calibration signal to measure a calibration-pseudo-range from said Receiver to said satellite-vehicle SV_i ;

(e) subtracting for said satellite-vehicle SV_i said calibration-pseudo-range from said pseudo-range to generate a group delay offset G_SVi ;

(f) removing said group delay G_SVi from pseudo-range measurements for satellite signals emanating from said satellite-vehicle SV_i ; and

(g) repeating steps (a-f) for each said "i" satellite-vehicle SV_i, i being less or equal to N.

14. A method of a parallel calibration production mode in order to create a database of group delay offsets at temperature T₁ satellite signals emanating from a satellite system comprising a plurality of N satellite-vehicles SV_i, N being an integer, i being an integer less or equal to N, said temperature T₁ being within the range of temperatures T₀, T_c !, said method comprising the steps of:

(a) generating a calibration signal by a Calibration Signal Generator;

(b) receiving satellite signals from each said satellite-vehicle SV_i by a Receiver including a plurality of Digital Channel Processors;

(c) tracking and measuring each said satellite signal at said temperature T₁ to measure pseudo-ranges from said Receiver to each said satellite-vehicle SV_i ;

(d) tracking and measuring said calibration signal at said temperature T₁ to measure calibration pseudo-ranges from said Receiver to each said satellite-vehicle SV_i ;

(e) subtracting for each said satellite-vehicle SV_i at said temperature T₁ said calibration pseudo-range from said pseudo-range to generate a plurality of N group delay offsets G_SVi/T1 ;

(f) storing each said group delay offset G_SVi/T1 measured at said temperature T₁ for each said satellite-vehicle SV_i in a computer memory ; and

(g) repeating steps (a-f) for another temperature T₂ within the range of temperatures T₀, T_c !.

15. A method of a real-time parallel calibration process in order to remove group delay offsets G_SVi from pseudo-range measurements for satellite signals emanating from a plurality of satellite-vehicles SV_i, said method comprising the steps of:

(a) generating a calibration signal by a Calibration Signal Generator;

(b) receiving satellite signals from each said satellite-vehicle SV_i by a Receiver including a plurality of Digital Channel Processors;

(c) tracking and measuring said satellite signals to measure pseudo-ranges from said Receiver to each said satellite-vehicle SV_i ;

(d) tracking and measuring said calibration signal to measure calibration-pseudo-ranges from said Receiver to each said satellite-vehicle SV_i ;

(e) subtracting for each said satellite-vehicle SV_i said calibration-pseudo-range from said pseudo-range to generate a plurality of N group delay offsets G_SVi ; and

(f) removing from pseudo-range measurements of satellite signals emanating from each said satellite-vehicle SV_i said group delay G_SVi.

16. A method for calibration a Narrow Band GLONASS satellite Receiver for group delay errors in satellite signals emanating from at least one GLONASS satellite, said method comprising the steps of:

(a) receiving said at least one GLONASS satellite signal;

(b) tracking and measuring said at least one GLONASS satellite signal to measure pseudo-ranges from said Narrow Band GLONASS satellite Receiver to each said GLONASS satellite;

(c) generating a GLONASS calibration signal for each said GLONASS satellite;

(d) tracking and measuring said GLONASS calibration signal to measure calibration-pseudo-ranges from said Narrow Band GLONASS satellite Receiver to each said GLONASS satellite; and

(e) subtracting for each said GLONASS satellite said GLONASS calibration-pseudo-range from said GLONASS pseudo-range in order to remove from pseudo-range measurements of each said GLONASS satellite signal said GLONASS group delay.

17. A method for calibration a combined Narrow Band GPS/GLONASS satellite Receiver for group delay errors in satellite signals emanating from at least one GPS satellite and from at least one GLONASS satellite, said method comprising the steps of:

(a) receiving said at least one GPS satellite signal utilizing a GPS rf channel of said combined Narrow Band GPS/GLONASS satellite Receiver;

(b) tracking and measuring said at least one GPS satellite signal to measure pseudo-ranges from said combined Narrow Band GPS/GLONASS satellite Receiver to each said GPS satellite;

(c) generating a GPS calibration signal for each said GPS satellite;

(d) tracking and measuring each said GPS calibration signal to measure calibration-pseudo-ranges from said combined Narrow Band GPS/GLONASS satellite Receiver to each said GPS satellite;

(e) subtracting for each said GPS satellite said GPS calibration-pseudo-range from said GPS pseudo-range in order to remove from pseudo-range measurements of said GPS satellite signal said GPS group delay;

(f) receiving said at least one GLONASS satellite signal utilizing a GLONASS rf channel of said combined Narrow Band GPS/GLONASS satellite Receiver;

(g) tracking and measuring said at least one GLONASS satellite signal to measure pseudo-ranges from said combined Narrow Band GPS/GLONASS satellite Receiver to each said GLONASS satellite;

(h) generating a GLONASS calibration signal for each said GLONASS satellite;

(i) tracking and measuring said GLONASS calibration signal to measure calibration-pseudo-ranges from said combined Narrow Band GPS/GLONASS satellite Receiver to each said GLONASS satellite; and

(j) subtracting for each said GLONASS satellite said GLONASS calibration-pseudo-range from said GLONASS pseudo-range in order to remove from pseudo-range measurements of each said GLONASS satellite signal said GLONASS group delay.

18. A method of measuring an electron count of ionosphere employing a GPS/GLONASS Narrow Band Receiver and a Calibration Generator circuit, said method comprising the steps of:

(a) selecting a single GPS/GLONASS satellite;

(b) calibrating for an L1 GPS/GLONASS group delay within said GPS/GLONASS Narrow Band Receiver using a calibration signal C_RF.sbsb.--_GPS.sbsb.--_L1 /C_RF.sbsb.--_GLONASS.sbsb.--_L1 ;

(c) calibrating for an L2 GPS/GLONASS group delay within said GPS/GLONASS Narrow Band Receiver using a calibration signal C_RF.sbsb.--_GPS.sbsb.--_L2 /C_RF.sbsb.--_GLONASS.sbsb.--_L2 ;

(d) measuring a difference in time of reception between said calibrated for said group delay within said GPS/GLONASS Narrow Band Receiver L1 and L2 GPS/GLONASS signals; and

(e) determining said electron count of ionosphere that is proportional to said difference in time of reception between said caliobrated for said group delay within said GPS/GLONASS Narrow Band Receiver L1 and L2 GPS/GLONASS signals.

19. The method of claim 18;

wherein said step of calibrating for said L1 GPS/GLONASS group delay within said GPS/GLONASS Narrow Band Receiver using said calibration signal C_RF.sbsb.--_GPS.sbsb.--_L1 /C_RF.sbsb.--_GLONASS.sbsb.--_L1 further includes the steps of;

(a) tracking and locking on an L1 GPS/GLONASS satellite signal using said GPS/GLONASS Narrow Band Receiver; and

(b) generating said calibration signal C_RF.sbsb.--_GPS.sbsb.--_L1 /C_RF.sbsb.--_GLONASS.sbsb.--_L1 using said Calibration Generator circuit.

20. The method of claim 18;

wherein said step of calibrating for said L2 GPS/GLONASS group delay within said GPS/GLONASS Narrow Band Receiver using said calibration signal C_RF.sbsb.--_GPS.sbsb.--_L2 /C_RF.sbsb.--_GLONASS.sbsb.--_L2 further includes the steps of;

(a) tracking and locking on an L2 GPS/GLONASS satellite signal using said GPS/GLONASS Narrow Band Receiver; and

(b) generating said calibration signal C_RF.sbsb.--_GPS.sbsb.--_L2 /C_RF.sbsb.--_GLONASS.sbsb.13 _L2 using said Calibration Generator circuit.