CN1220061A

CN1220061A - Apparatus for code tracking in direct sequence spread spectrum receiver

Info

Publication number: CN1220061A
Application number: CN96180312.6A
Authority: CN
Inventors: A·P·胡伯特; D·P·钱德勒
Original assignee: Roke Manor Research Ltd
Current assignee: Roke Manor Research Ltd
Priority date: 1995-02-16
Filing date: 1996-03-28
Publication date: 1999-06-16
Also published as: GB9502992D0; GB2298110A; CA2250074A1; BR9612584A; GB2298110B; CA2250074C

Abstract

Inphase and quadrature signals are applied to first, second and third correlators, the first correlator being arranged to generate prompt signals, the second correlator being arranged to generate late signals and the third correlator being arranged to generate early signals. The output from the first correlator is passed to estimation means and signals generated from the estimation means are multiplied with the outputs from the first and second correlators in respect of each channel. The inphase and quadrature channel signals generated from the second and third correlators are added together and the sum of signals are then subtracted to generate a signal for controlling a loop filter and clock generation means controls the analogue to digital converters.

Description

The equipment that is used for code tracking in the Receiver of Direct-sequence Spread Spectrum

The present invention relates to the receiver of direct sequence spread spectrum, and the code tracking part that is related to receiving equipment.

The common embodiment that is used for the code tracking device of spread spectrum comprise so-called in advance, in time, the hysteresis tracking loop, this relates to the energy measuring to waveform correlation, and this waveform correlation is usually in advance half-chip and carry out in advance relevant and the relevant waveform of the energy of the chip of hysteresis half-chip and the execution that lags behind usually.Differentiate curve by deducting to be worth in advance to produce regularly then from lagged value, this is used to closed feedback loop so that the adjustment time occurs thereby make this be worth timely in the correct time.

The objective of the invention is to cancel in advance and the relevant requirement that must occur in the half-chip part that lags behind, more specifically, is to allow them occur in chip place of plus or minus.This can cause special difficulty in common embodiment, because drop to zero at a chip place of plus or minus correlation for the circuit of the timing that is operated in nominal.Therefore, to the very large interference that can become of the energy measuring of signal, common like this embodiment can cause differentiating that curve itself is just very noisy, and can cause a very unsettled timing loop.

This equipment has used the spread-spectrum signal that carries out Nyquist (Nyquist) filtering, thereby, it uses its correlation function at the signal of old good gradient still when the zero point, this basic problem is to solve like this, promptly be not to these measurements of being done at interval or done relevant in carry out energy measuring, but they are compensated coordinating from the phase reference value that signal drew timely, reduce The noise by this, thereby can draw such distinguishing signal, it has following the getable identical signal noise ratio of situation with more traditional shifting to an earlier date/hysteresis plus or minus half-chip.

According to one embodiment of the present of invention, the equipment that is used for code tracking in Resistant DS Spread Spectrum System is provided, comprise the device that is used for received signal, be used for the signal transformation that receives is become the device of homophase and orthogonal signalling, be used for homophase and orthogonal signalling are converted to the analog-digital conversion equipment of digital signal, be used to handle first correlator of signal timely, be used to handle second correlator of the signal of hysteresis, be used to handle the third phase pass device of signal in advance, be used to draw valuation device from the valuation of first correlator output signal, be used for this valuation is multiplied each other with the output signal of third phase pass device and homophase and orthogonal channel first and second multiplication and adder added together respectively with from second, be used to deduct substracting unit, and be used for receiving output signal and the control device that produces the control signal that is used for the analogue-to-digital converters device from substracting unit from the result of described first and second multiplier.

According to an alternative embodiment of the invention, the equipment that is used for code tracking in Receiver of Direct-sequence Spread Spectrum is provided, it comprises the device that is used for received signal, be used for the signal transformation that receives is become the conversion equipment of homophase and orthogonal signalling, be used for homophase and orthogonal signalling are converted to the analog-digital conversion equipment of digital signal, be used to handle first complex correlator of signal timely, be used to handle second correlator of the signal of hysteresis, be used to handle the third phase pass device of signal in advance, the frequency phase demodulation apparatus, it is used to receive from the signal of described first correlator and produces a signal that is used for controlling by this way described conversion equipment, promptly make coherent signal be comprised on the signal phase channel, also comprise being used to deduct and close the subtracter device of the output signal of device, and be connected to described subtracter device so that be used for controlling the control device of described analogue-to-digital converters device with third phase from described second.

Now with reference to accompanying drawing various different embodiment of the present invention are described, wherein:

Fig. 1 has shown the typical correlation function for the output of correlator,

Fig. 2 has shown the block diagram of the first embodiment of the present invention, and

Fig. 3 has shown the block diagram of the second embodiment of the present invention.

With reference to Fig. 1, shown the typical correlation function of correlator output, expression is in advance, that lag behind and relevant timely normal nominal position, and for the position of the new suggested of position that shift to an earlier date and hysteresis, the position obviously is same position timely.

With reference to Fig. 2, signal input generation device 2 feed signals that are shown as antenna are given frequency-converter device 4, and the latter produces I and Q signal, and they are fed to a pair of analogue-to-digital converters 6,8.The output of these transducers is fed to three and half complex correlator.The correlator that comprises unit 10,12,14,16 is used for position timely, thereby the I sample signal of the output of transducer 6 in multiplier 10 with and time-code multiply each other, and in accumulator 14, added up, this process is same to multiplier 12 and the accumulator 14 that is used for the Q channel.The output of signal in time is sent to known other circuit that is used for the demodulation purpose of technical staff.This output also is fed to valuation device 18,20, and they are used as filter in the present embodiment basically, so that strengthen the signal to noise ratio of the measurement of this position.

Lag correlation device centering, carry out similar operation, this correlator is to comprising multiplier 22 and the accumulator 26 that is used for the I channel, and the multiplier 24 and the accumulator 28 that are used for the Q channel, yet, the output of these accumulators is multiplied each other with the valuation that draws from channel timely in multiplier 30,32, and is added together in adder 34.

Similarly, for the channel that shifts to an earlier date, by multiplier 36 and accumulator 40, multiplier 38 and accumulator 42 are carried out similar operation.Output from accumulator 40,42 is also multiplied each other by multiplier 44,46 and valuation, and it is exported by adder 48 additions.The output of adder 34,48 is subtracted each other in substracting unit 50 then.It will be appreciated that these operations can be carried out with different order, in fact, if carrying out carrying out subtraction before the multiplication, can save two multipliers, yet this embodiment can explain present principles preferably.

The output of subtracter device 50 is fed to loop filter means 52, it is used for controlling the clock generator 54 that transducer 6,8 is sampled, so that in this wise in advance or the timing of late samples, make timely signal consistent with correlation at the peak value place of correlation function.It will be appreciated that, other embodiment of the present invention also is possible, for example, sampling is carried out with the speed once higher than each chip samples at the beginning, and the generation of sample can form by the interpolater device when once the sampling of each chip, the timing of the sample that produces by the interpolater device can be set up by setting up correct interpolation coefficient, and these coefficient selection also can be controlled from the output of filter apparatus 52.Also will see, and under some environment, if the output of valuation device 18,20 is controlled in this wise they normalization, make them become constant amplitude and they only embody the phase information of this valuation, then will be an improvement.

Local code generator 56 by can produce in advance/lag behind/in time the circuit 38 of signal is controlled multiplier 10,12,22,24,36,58.

Fig. 3 has shown another embodiment.With reference to Fig. 3, signal generation device 60 is antennas.Frequency converter 62 is fed to I and Q channel by analogue-to-digital converters 64,66.As noted earlier, multiplier 68 and accumulator 72 constitute correlator together, and similarly, multiplier 70 and accumulator 74 constitute another correlator.Come the output of autocorrelator to be fed to frequency phase demodulation apparatus 76, it produces frequency control signal in the known mode of technical staff, promptly this signal is fed back to frequency converter 62, so that the phase place of control of conversion in this wise makes coherent signal all be maintained on the I channel.Like this, for the signal that shifts to an earlier date with lag behind, on the Q channel, carry out relevant just become unnecessary, thereby, as long as provide single multiplier 78 and single accumulator 80 to produce signal in advance, similarly, for delay signal, can only provide multiplier 82 and accumulator 84.Output from

accumulator

80,84 is subtracted each other in substracting unit 86, and its result is fed to loop filter 88, is used to control clock generator apparatus 90.

Local code generator 92 produces in advance/lags behind/timely signal by the circuit 94 that is used to control

multiplier

68,70,78,82.

Those skilled in the art will be easy to see that alternative scheme belongs to the scope of the invention fully.For example, can make to the connection of frequency converter by cable.

Claims

1. equipment that in Receiver of Direct-sequence Spread Spectrum, is used for code tracking, comprise the device that is used for received signal, be used for the signal transformation that receives is become the device of homophase and orthogonal signalling, be used for homophase and orthogonal signalling are converted to the analog-digital conversion equipment of digital signal, be used to handle first correlator of signal timely, be used to handle second correlator of the signal of hysteresis, be used to handle the third phase pass device of signal in advance, be used to draw valuation device from the valuation of first correlator output signal, be used for this valuation is multiplied each other with the output signal of third phase pass device and homophase and orthogonal channel first and second multiplication and adder added together respectively with from second, be used to deduct substracting unit, and be used for receiving output signal and the control device that produces the control signal that is used for the analogue-to-digital converters device from substracting unit from the result of described first and second multiplier.

2. desired equipment in the claim 1 is characterized in that, wherein each correlator comprises a multiplier and accumulator that is used to handle in-phase signal, and a multiplier and an accumulator of being used to handle orthogonal signalling.

3. desired equipment in the claim 1 or 2 is characterized in that, wherein control device comprises loop filter and clock generator.

4. desired equipment in claim 2 or the claim 3 is characterized in that, wherein the multiplier in each correlator by code generator be used to produce in advance/lag behind/the device control of signal code in time.

5. equipment that in Receiver of Direct-sequence Spread Spectrum, is used for code tracking, comprise the device that is used for received signal, be used for the signal transformation that receives is become the conversion equipment of homophase and orthogonal signalling, be used for homophase and orthogonal signalling are converted to the analog-digital conversion equipment of digital signal, be used to handle first complex correlator of signal timely, it is used to handle second correlator of the signal of hysteresis, be used to handle the third phase pass device of signal in advance, the frequency phase demodulation apparatus, it is used to receive from the signal of described first correlator and produces a signal that is used for controlling by this way described conversion equipment, make coherent signal be comprised on the signal phase channel, also comprise being used to deduct and close the subtracter device of the output signal of device, and be connected to described subtracter device so that be used for controlling the control device of described analogue-to-digital converters with third phase from described second.

6. desired equipment in the claim 5 is characterized in that, wherein first correlator comprises a multiplier and accumulator that is used for each signaling channel.

7. desired equipment in the claim 6 is characterized in that, wherein second and third phase close device and comprise a multiplier and accumulator that is used for each signaling channel.

8. desired equipment in each in the claim 5 to 7 of front is characterized in that, wherein control device comprises loop filter and clock generator.

9. desired equipment in claim 7 or the claim 8 is characterized in that, wherein the multiplier in each correlator by code generator be used to produce in advance/lag behind/in time the device of signal code is controlled.

10. basically as former with reference to the equipment of Fig. 1,2 and 3 described here.