Title of Invention

A METHOD OF PROVIDING FREQUENCY DISCRIMINATION OF A RECEIVED INPUT SIGNAL

Abstract

A method of providing frequency discrimination of a received input signal characterized by a receive frequency that is offset from a transmit frequency by a frequency error, the method comprising the steps of identifying a cross product and a dot product from the received input signal; comparing the value of the cross product relative to a predetermined threshold; and adjusting the cross product by an adjustment amount equivalent to a product of the dot product times a constant value on the basis of the comparison, wherein said cross product is decremented by said adjustment amount if the cross product is greater than said predetermined threshold, and said cross product is incremented by said adjustment amount, if said cross product is less than said predetermined threshold.

Full Text

FREQUENCY DISCRIMINATOR BACKGROUND OF THE INVENTION Field oi the Invmtion [0001] The present invention relates generally to communications. Particularly, rbe present invention relates to frequency discrimination in a v.■>auni«iications environment. '.inscription of the Related Axt i i)l)02] CDMA conanunicatioos systems typically use directional antennas located in the center of a cell and broadcasting into sector.; of the cell. The antennas IK?, coupled to base stations that transmit control the cells. The cells arc? typically located in mE=;cr metropolitan areas, iilcng highways, and along train tracks to allow uonsuscers to communicate both at home and while traveling. ,' :;;equency that is loiown to each, there are factors such as multipath errors and I>oppler shift in. "the frequency that introduce errors in 'the frequency that is received. Tor exiiinple, if a mobile is approaching a base station, the Doppler effect increases ;ne signal's .frequency as observed by die base station. If the mobile is moving away from the bass station, the base station observes a signal having a frequency that is less tian the frequency transmitted by the mobile. The amount of frequency shift is a t unction of t:.e $x\eed of the mobile. [00043 Another source of frequency error is the fact that the two local collators (one at the base station and one at fee mobile taat are used for generating the "clock" signal) can never be operating at exactly the same frequency. Typically, the mobile uses ,a IQIS expensive local oscillator that can introduce a frequency error of up to 10 KHz; when the carrier frequency is around 2 GHz. [iJ&OS]' During communication, the base station transmits a pilot channel that in received by the mobile. The pilot channel, comprised of pilot symbols, contains no n formation. 'Hie mobile utilizes the pilot symbols to generate time, frequency, phase, ai id sign al str;ngi3i references. [ 1006] In some systems, the mobile also transrxiits a pilot signal. The mobile's pilot signal is them similarly used by the receiving: base station to generate time, frequency, phase, and -signal strength references relative to the mobile. [0007] Ii order for a base station to communicate with a mobile on a certain frequency, bo?:h need to uae a frequency discriminator in a frsquenoy-tracking loop, [0008] FIG, 1 illustrates a typical prior art frequtsney-tracking loop (FTL) 100. 'This figure &':sw*& a signal, A/, entering a summer 101. Af represents the frequency cuTor present m an incoming signal D£ successive pilot symbols. The summer 101 ;!;\ibtraci:s from Af an initial estimate &f. [111)09] Frequency iliiscrinanator 105 is loiown and operates on the frequency' li-cror associated with successive pilot symbols. The value of each pilot symbol is h erein jepresenuid by variable y*. The period of each symbol y>. is denoted by Ts* ";i)010] An incoming sequence of pilot symbols are accumulated after input ■5i;dpnal rotation to result in a residual frequency error, out of summer 101, equal to *\fn* ■ ^pdot symbol jk having residual frequency error Afrerk may be denoted as: where nk is the additive noise corrupting the kih symbol and^ is a complex amplitude mat is a function of, among other things., the current channel attenuation. It is assumed Mat fading i;> :dow enough so that successive symbols have roughly the same complex giinplitude. {0011] A time constant (T) is herein defined as the time it takes FTL 100 to converge to 1/e of an initial frequency error. ApulHn range conventionally defines a maximum initial frequency error for which FTL 100 is able to converge. A design goal is to minimize time constant T, all the white maximizing the pull-in range, tc maintain the standard deviation of the frequency error under steady-state conditions to within desirable levels. £M>12] A loop filter L(z) 110, senes coupled to tne output or frequency ciscriniinator 10Sf is; used to adjust the time constant T» pull-in range, and standard deviation of thr, frequency error. [D013] A known type of frequency diacrirninator 105 is a cross product <:a ym operation of which may be expressed as hff i> si denoting complex conjugation. From die above equation for yk and A/4* we get I [0015] with w being a noise component Thus as A/w approaches V^ ,the value or' sin(;?;?7\A/rH) becomes smallest resulting in the following condition: ! in range- due ro ;he effect of noise. Second, when the initial frequency enor A/ is greater than Vi the theoretical pull-in range, FTL 100 takes a long time to converge to 1/5 of an initial frequency error A/, SUMMARY OF THE INVENTION [ (rsquer.cy discricarnation. In particular, the invention provides a frequency tracking lcop (FTL) providing a large effective pull-in range and fast convergence characteristics- when an initial frequency error greater than Vt a theoretical pull-in range ii detect-!.. 10018] In an embodiment, a cro&s product is first determined, on an input to the FTL. This c:x:$s product is of form imag^y^), where yk is one sample or symbol of the received signal and y^j is a preceding symbol. A dot product, expressed as real(y; y*^). ifc then also determined. J00191 When the cross product is greater than a predetermined threshold, the cross product h decremented by the product of the dot product multiplied by a ;;>rederi5imin;d constant value. In a specific implementation, a piedetennined threshold of Y3lue zero and a predetermined constant value i.n the range of 0 to 5 are selected. [(R)20] Conversely, when the cross product is less than the selected predetermined threshold, the cross product is incremented, by the product of the dot p'sduct multiplied by the predetermined constant value. The calculation of and inrcettieuting aid decrementing of the cross product is generated by a frequency d. Eliminator. This- output of the frequency discriminator is used to derive a residual frequency en or '.lot an incoming signal comprised of successive pilot, symbols. Successive symbols signals are fed into the frequency discriminator and the previously derived residual frequency error used to adjust the output of the frequency discriminator ihat then provides a new output to the F1TL BRIEF DESCRIPTION OF THE DRAWINGS [|021] HG. I i$ a general block diagram of a kr.own frequency-tracking loop (f'TL). |( 1)22] FIG. 2 shows a more detailed block diagram of the frequency [0D23] F[t3. 3 shows a block diagram of a mobile station incorporating a FTL including the frequency discriminator of the present invention. [0024] FIG. 4 shows a block diagram of a base station incorporating a FTL including the frequency discriminator of the present invention, 10025] FIG* 5 shews a plot of the response of the frequency discriminator of ihe present invention compared to a known frequency discriminator. |'i)026] FIG. 6 shows a plot of the residual frequency and a first initial ■vequency error w a function of time, assuming a first pilot strength, derived using the frequency discriminator of the present invention. :[l)027] KG. 7 shows another plot of the residual frequency error as a function of time, assigning a second pilot strength and the first initial frequency error, derived ; sing die frequency discriminator of the present invention. [(1028] HG. 8 show-s a plot of the residual frequency error as a function of thus, assuming a second initial frequency error, and the first pilot strength. [(1D29] FIG. 9 shows a ploc of the residual frequency exror as a function of tins, assamin e; a ueeond/third initial frequency error, and the second pilot strength. [0)30] FIG. 10 shows a block diagram of a frequency discriminator for use with signals having low signal-to-noise ratios. DETAILED DESCRIPTION [1)031] A frequency discriminator characterised by the following description provides, a large effective pull-in range and fast convergence in comparison to known ctoss product discriminators. [0032] h). accordance with an" embodiment, the frequency includes both a siioiple cross product discriminator and a dot product discriminator. As used above, i: e cros s prod'ac: .discriminator, denoted as cp, is expressed as: where a and it) ft;e constants whose values are design parameters based on a desired s) uem. [01*35] II;L a first embodiment, a is in the range of 0 to 5. For a = 0 the frequency discrinuiuiior collapses to a simple cross product discriminator. This can he ss:e;n by substituting 0 for a in the above expression for &f™[ [i(>36] In another embodiment a is chosen to be a power of 2. This is derived 3i' a frequency discriminator hardware-specific implementation where muHpIication virh a, where a is a power 2, becomes a simple left shift operation. |,T)037] In one embodiment, ft its in die range of a real number that is; less than 0, However, oihsc: ranges for ft can be used as well. [OtfBS] It should be further appreciated dial the frequency discriminator operation described hereit maybe implemented by a digitd signal processor (DSP). Also, trie dot product measurement may be calculated in parallel with the cross product measurements using hardware. The "if statements can be implemented as ;:iultipiixers which use thd sign bits of the cp and the dp calculation as output ;>;lecto::s. ^)039] A hardware block diagram of one embodiment of the frequency ;iscrin.inator in illustrated in HG, 2* Those skilled in tie art will recognise that ?lterna:e embodiments may encompass different hardware variations to arrive at the ^ame desired result [0040*1 'Ihe frequency discriminator of FIG. 2 includes a cross product block ;.01 and a dot product block 202. Both blocks 201 and 202 receive as inputs, sequential pilot, symbols yk and y^. 10041] £i the illustrative embodiment, the output cross product generated by cross product block 201 is a real value (as opposed to a complex value). The real value is expressed as cp = Tea](y*)real(yw) + imag(yjj)imag(y^/). [0)42] The output dot product block (202) also generates a real vsdue. This V5lue is- expressed as dp = imag(yit)real(yjw) - real(yjfe)iinag(y*.;). [ malriplexer 235, as shown. In the present example, when a = 0, a simple cross product is output, by tiie frequency discriminator 105. [i|tl44] Output dot product (dp) is fed to the zero (0) input of a first multiplier 215 where it geta multiplied by a. The output of the first multiplier 215 is input to a second 'multiplexer 225, The output of the first multiplier 215 is also input to a second r* ultiplier 220 where the s:gn of the adp signal gets inverted by multiplying the input uith -1. The oulput of second multiplier 220 is also inpu: to the second multiplexer i:25. A select input of second multiplexer 225 is received from decision block 2051 [|i«)453 When the output from decision block 205 is true, (*.#., cp high is generated and the non-inverted ctdp signal is output from multiplexer 225. When rot true., Le> cp > 0, the inverted arfp signal is output by multiplexer 225. i11046] T.iie second multiplexer 225 output is coupled to summer 230 and c.ther udp or (-o.jp) is added to output. The output from summer 230 is input to one f i) input of firs: multiplexer 235. |?!1047] Referring to the bottom of FIG. 2, the output of decision block 210 ninputs a lojiii? bigli when the condition dp holds true. A logic high signal as a ?>lect input i.c the first multiplexer 235, will cause ths first multiplexer 235. This i$ to select the output of summer 230. When the dot product is 0, the condition is false and iftt cross product is selected as the output to first multiplexer 235, and decision block HO selects the 0 input of the first multiplexer 235. (0048 J li: should be understood that the above-described signal selection procests may be implemented in various programming languages. In one embodiment, the process can be implemented in the "C" programming language, and is. expressed [O-0491 The exemplary frequency discriminator can be used in any situation that requires a low-comple;city frequency estimator, such as in the frequency-tracking loop of :?IG. 1. In: one embodiment, this frequency discriminator is used in a FTL in a mobile communication device such as a mobile telephone. In a mobile telephone, the frequency discriminator it used on the downlink direction of the communication. Le. the basts station to mobile link. [iJ050] Because tlie signal-to-noise ratio (SN&) of a downlink pilot is Milatively high, & frequency discriminator as described aboA'e is particularly desirable. [[051] 'I;h«3 above frequency discriminator can also be used on the uplink direction, le... "h& mobile-to-base station link. In die uplink, the SNR of a pilot is very l;w> Fcr example, a pilot SNR ( CA ) might be as low as -38dB. Frequency / io i .^eliminators described above may be used in a low SNR uplink. 1110521 However, compensating tor the low SNR to adjust lower SNE, it might hs desirable to increase the accumulation length of the pilot symbols (i.e., increase 'i7>. Alternatively* low-pass filtering the cross product and the dot product will also vork. Using such an embodiment changes the above equations. Factoring in a low tli>5TR, a frequency discriminator for use in an uplink for example may be expressed aiv follows. where |i is constant between 0 and I and ihe cp and dp teuns are outputs of one-tap IIBL filters. For very low pilot SNRs, a p closer to 0 is best. For p = ls the above expression yifclds the same discriminator result as the high SNR frequency cscriitiinator expression described earlier. J (:t()533 FK3- 10 illustrates a frequency discriminator in an ambdodiinent of the present invention as might be found cm the uplink of a communication system. This block ciagrar. is not discussed in detail since it is substantially similar to the frequency discrinoinator of the downlink as illustrated in FIG. 2. Hovever, the ■frequency diucrirruriator for the uplink incorporates a one-tap IIP. filter. 1001 at the output of the cress product generator $n& a second one-tap HR filter 1005 at the output ■ill' the dot product generator. Filters 1001 and 1005 are responsible for low-pass rl.Iterim; the ctons products and dot products, respectively. j)054] A block dia;*ram of a mobile station incorporating the .frequency discriminator of the preset; invention is illustrated in FIG. 3. The mobile station includes of a transmitter 302 and receiver 301 coupled to an antenna 303, Transmitter :02 mcdulate; the aural signals from the microphone 305 for transmission. Depending ;ii the iype of communication device, transmitter 30?- or like device may digitize the siural signal f'ioxi a microphone 305 prior xo modulation. Antenna 303 then radiates t*i« signal to the; intended destination, |D055'j Receiver 301 incorporates an FTL 301' constructed as described herein. Receiver 301 is responsible for receiving and demodulating signals received *er antenna 303. FTL 30V is used within receiver 301 to lock the receiver on to a desired, received frequency.. In some communication devices, the receiver may be responsible for converting received digital signals into their analog equivalent for transmission by a speaker 306. j;;O056] The communication device is controlled by a controller 304- such as a .nicrofxocessor or other controlling device. The controller is coupled to and controls he transmitter 302 and receiver 301 functions. [£©57] A display 307 and keypad 308 are coupled to the controller 304 for cjsplaying information entered by a user or; the keypad 308. For example, the user i;:.ay enter a telephone; number using the keypad 308 that is displayed on the display ■; 07 and subsequently transmitted to a base station using the transmitter 302. [0058] In one embodiment, the communication device is a cellular Uidiotelisphone incorporating me frequency discri&rinator of the present invention. .:Utemai;e embodiments include personal digital assistants with communication I.rt059] A block diagram of a base station incorporating the frequency discriminator as described herein is illustrated in FIG. 4, The base station is comprised of a transmitter 401 that receives a signal from the network to which the base station \i, coupled. Trie rtansmitter 401 modulates the signal and transmits the signal, at the : roper ;Dowe:: .level, over the antenna 405. i)060] A received signal is received by the antenna 405 and distributed to the ;.-3ceive:: 403 having a frequency discriminator 403. Receiver 403 tracks the frequency jf the -received signal using FTL 403 and demodulates any Appropriate signals. The :lemodula?ed signals are sent: over the network that is coupled to the base station to the appropriate destination. (0061] In one embodiment, the base station illustrated in FIG 4 operates in a cellular environment. Alternate embodiment base; stations can be any base station that allows a mobile, wireless communication device to communicate with a fixed icfrastiuciur^ 10062] PIG- 5 illustrates a plot of the frequency response of a frequency discriminator fc. accordance with an embodiment operation under various values of a. More specifically a plot of A/^'w is shown using Ts =2*6/x84xio6 sec. and assuming no noise*. The curve corresponding to ot=0 represents a regular cross -product discriminater. ft can be seen from HG, 5 that when ct=2, the discriminator output closely approximates /(2^A/rtf)==2^Ts.A/re> andean be assured from tliis that we have a vsxy efficiently perfonning frequency-tracking loop. For each of the curves of F7G, 5, i* is esfiuitied ro be of value zero (0). [i)63] This output of the illustrative embodiment frequency discriminator is large to:: values of Afrcs larger than half a pull-in range.. The small value cross discriminator .results of conventional solutions are ignored. The present frequency discriminator provides a larger effective pull-in range while also converging very fast vrien an initial frequency error is large. [0-064] FIGs, 6-9 illustrate results from 'simulations using a -frequency discriminator as described herein. In each simulation, the pilot symbol accumulation length in assumed to be N==256 chips. This results, in a T^%MX\O6 seconds., which is equivalent to a theoretical pull-in range of ±7.5 kHz, ('('065] FIG. (5 illustrates a plot, of residual frequency error, fs as a function of tine generated by each of two different frequency discriminators, one a conventional coss product frequency tiiscriminatcr and the other a frequency discriminator as F / dascritosd herein. An initio frequency error of 7,4 kHz. aid pilot SNR of y7 - -26 dBis assumed. Ii)()66] Ii: can be seen that, with the assumed initial frequency eixor, a [;ciiven"iona] cross .product discriminator will cause the FIT. output to diverge. On the ■rrher hand, an FTL using a frequency discriminator of a present embodiment <:un verges relatively quickly.> [J!067] HG. 7 illustrates what happens when the pilot strength is increased to z? / -y .- .20 d.8. Wldle bo:h present invention and prior art FTLs eventually converge, the presently disclosed frequency discriminator converges substantially faster than a cross ncoducl di recriminator. )0068] The plots of FIGs. 8 and 9 are similar ro FIGs. 6 and 7 respectively. FIG. 8 better illustrates residual frequency error as a function of time with a pilot SNR of ~ t.'iese plots, it cm be qincldy seen how present embodiment frequency discriminator velds converges results that are substantially faster than conventional cross product UiScriimnaToifi.. [0069] 'Die frequency discriminator of the present invention U not limited to iijiy vascous emtodiments of the specific air interface. One implementation utilizes an embodiment in a wideband code division multiple access (WCDMA) system. One skilled in the art would readily recogn^e that the invention has utilized any number of varying air interface;; such as general CDMA, system, cdma2G00, EDMA7 and TDMA. 10070] In summary, the frequency disctiininator of the presently described tuiiboditnent in a relatively low complexity frequency estimator that can be used in any system requiriug. frequency estimation. By using dot product calculations, either in is'olatioM ambulation with dot product measurements, resales in an improved solution requiring only comparisons> additions, and simple multiplications at best, ll 01)71] k .should be.noted that :;n all the embodiments described above, method ;i;;eps czn be bkrehanged without departing from the scope of the invention, !)I072] T.'iose of skill in the art will understand that information and signals may be represented using any of a variety of different technologies and techniques. For exEiinple, data, instructions, commends, information, signals, bits, symbols, and '.Mips that may b« referenced throughout the above description may be represented by voltages, cuireirts, electromagnetic waves, magnetic fields or particles, optical fields ;;r parti ;ies, or any combination thereof. Iv)073] Those of skill will further appreciate that the various illustrative logical hlocks, module;;, circuits, .and aigoiithm steps described hi connection with the •i;embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks., modules, circuits, and :;:£ps have besn described above gexierally in terms of their functionality. Whether :MCh functionality is implemented as hardwire or software depends upon the j:&rticu!ar application and design constraints imposed on the overall system. Skilled artisans, may Implement the described functionality in varying ways for each particular amplication, but «uch implementation decisions should not be interpreted as causing a , departure from tiie scope of the present invention. .0074] The various illustrative logical blocks, modules, and circuits described •HI connection with th& embodiments disclosed herein may be implemented or ■performed wich a general purpose processor, a digital signal processor (DSP), an upplicaion specific integrated circuit (ASIC), a field programmable gate array L?PGA> or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions i:escribsd herein, A general purpose processor may be a microprocessor, but in the .\icemative, the processor may be any conventional processor, controller, nicrocontrollci, or state machine- A processor may also be implemented as a combination erf' computing devices, e.g., a combination of a DSP and a e.iicroproces.aor, a plurality of microprocessors, one or more microprocessors in ;onjunction with a DSP cere, or any other such configuration. (S'075] 'Ihe steps of a method or algorithm described in connection with the :mbod:.meniir disclosed herein may be; embodied directly in hardware, in a software uioduU; ea edited, by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory. ROM memory, EFROM memory* EEPROM memory, registers, hajd disk, a removable disk, a CD-ROM, or any other iorm of storage medium known in the art. An exemplary storage medium is coupled tc the processor such the processor can read information from, and write information io, the storage medium. In the alternative* the storage medium may be integral to the processor. Ihe processor and the storage medium may reside in an ASIC. The ASIC may reside in a uuser terminal. 10076] la tlie alternative, the processor and the storage medium .may reside as discrete components in a user terminal. The previous description of the disclosed t:anbodhneni;s is provided to enable any person skilled in the art to oiake or use die l>:resen: invention. Various modifications to these embodiments will be readily apparent to those skilled in the ait, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the CLAIMS J. A method of providing frequency discrimination of .a received input s:gnai characterized by a receive frequency that is offset from a transmit frequency by a frequency error, the method comprising: identifying a cross product and a dot product from the received nput siignal; comparing the value of the cross product, relative to a predetermined Threshold; and adjusting the cros&. product by an adjustment Amount equivalent to a product of the dot product times a constant value on the basis of the zomparison. 2. The method of claim 1, wherein identifying the cross product :: wolves multiplying an imaginary portion of a product of a sample of che received :iput signal with a complex conjugate of a sample of a previous sample of die input uijnal. 3 The method of claim K wherein the predetermined tlireshold is i€TO- 4. The method of claim 1, wherein the adjusting is repeated until :'ie frequency error is decreased to a minimum value, ::!. The method of claim 1, wherein the constant value is substantially in the range of 0 to 5. 6. The method of claim 1, wherein the constant value is a value larger tiianO. 7, The method of claim 2, wherein the dot product is substantially equivalent to a real portion of the product of the sample of the input ^igiial multiplied \>v:'n the complex conjugate of the sample of the previous sample of the input signal. 8, A method of converging a frequency error of a signal, characterized by .* plurality o:: symbols, to a predetermined frequency, comprising: identifying a cross product and a dot product from the signal: multiplying the dot product by a constant value to generate a frequency adjustment product; when the cross product is greater thai) zero, decreasing die cross oroduei 'by the frequency adjustment product; imd when the cross product is lest than zero, increasing the cross product by the frequency adjusiment product. $K The method of claim S7 wherein identifying the cross product involves calcuiatingixcag(yJ.,y^.1) where y* is a symbol of the plurality of symbols. 10. The method of claim 8, wherein identifying the dot product .involves calculating rerJ(y;.v^,J where >* is a symbol of the plurality of symbols. 1L The method of claim 8, wherein die steps of decreasing and bereaving the c::os& product &re repeated until die frequency error is at a minimum ■ value, I.L The method of claim 11, wherein rhe minimum value is >.pproxi mutely zero frequency error. X 13. A frequency discriminator apparatus having an input signal comprising a plurality of symbols, the apparatus comprising: a cross product generator, coupled to the input signal, for jjeneratius a cross product of the input signal; a dot product generator, coupled to the input signal, for jgenerai:itt.g a dot product of the input signal; a multiplier coupled to the dot product generator for generating .i product in response to The dot product and a constant value; a first multiplexing device having a first input coupled to the product t:nd a second input coupled to a negative of the product, the second multiplexer selecting as an output one of either the first input or the second input ir. response to the cross product; a summer coupled to the cross product generator and the output of the fct multiplexing device, die summer generating a summation signal of the cross, product and the product; and a sejend multiplexing device having a first input coupled to the cross product generator and a second input coupled to the summer, the second multiplexing device selecting as an output one of either the cross product or the summation signal in response to the dot product, 14. The apparatus of claim 13, further including: a first comparator coupled to th* cross product generator, the first comparator generating a first selection signal in response to the relation of the cross product to a first threshold value, the tarsi selection signal coupled to a selection input of the first multiplexing device; and a second comparator coupled to the dot product generator, the second comparator generating a second selection signal in response to the dot product, the second selection signal coupled to a selection input of the second imiltiF'teidng device. 15. The apparatus of claim 14, wherein the first threshold value is substantially -.zvto and the second threshold value is substantially in the range of a real n i miber less thai \ zero. 16,. A mobile communications device comprising; & receiver for demodulating a received signal that wa:> received over ?i ::5o::omunications channel, the receiver having a frequency discriminator 1 hat estimates a frequency of the demodulated signal, the frequency iftsoiimiiator comprising: a cross product generator, coupled to the input signal, for generating a cross product of the input signal; a dot product generator, coupled to the input signal, for generating a dot product of the input signal; a multiplier coupled to the dot product generator for generating a product in response to -the dot product and a constant value; a first multiplexing device having a first input coupled to the product and a second input couple! to a negative of the product, ib? second multiplexer selecting as an oircput one of either the first iavput or the second input b response to the cross product; a summer coupled to the cross; product generator and the output of the first multiplexing device, the summer generating a summation signal of the cross product and die product; and a second multiplexing device having a first input coupled to the cross product generator and a second input coupled to ihe summer, rjie second multiplexing device selecting as an output one of either the cross product or the summation signal in response to the dot product. .17. The mobile communications device of claim 1.6, further comprising; a speaker for converting the demodulated signal to an aural signal, H microphone for generating the output signal; a display that displays mobile communications data; and a controller coupled to the receiver and the display in order to control tte mobile communications device. Vt. The mobile communications device of claim 16, further comprising a transmitter fur modulating a cede division multiple access output signal C'Verthe channel. 19. The mobile communications device of claim 16, wherein the received sigmu is a code division multiple access signal. 20. In a base station receiver adapted for use in a wireless communications network, a frequency discriminator for estimating a frequency of a received signal., tb.e frequency discriimnator comprising: a cross product generator, coupled to the input signal, for generating, a cross product of the input signal; a dot product generator, coupled to the input signal, for generating a dot product of the input signal; a first low pass filter, coupled to the cross product, for jgiener&tng a filtered cvoss product; a second low pass filter, coupled to the dot product, for £;eneratif..g a filtered dot product; a multiplier coupled to the filtered dot product generator for generating an adjustment product in response to the filtered dot product and a consult value; a fust multiplexing device having a first input coupled to the produce mid a secoric input coupled to a negative of the adjustment product, the second multiplexer selecting as an output one of either the first input or the second input in response to the filtered cross product;; a summer coupled to the filtered cross product generator and he output of the first multiplexing device, the summer generating a summation signal cf the filtered cross product and the adjustment product; and a second multiplexing device having a first input coupled to the first low pass filter and a second input coupled to the summer, the second multiplexing device selecting as an output one of either the filtered cross product or the summation signal in response to die filtered dot product. 21 A frequency tracking loop for tracking a frequency of a signal, tfit! frequency having a frequency error, the frequency tracking loop comprising: a summer that generates a residual frequency error by subtracting a current estimate of the residual frequency error from the f requeue;;/ error; and a frequency discriminator coupled to the residual error, the frequency discriminator generating the current estimate of the residual frequency error, the frequency discriminator comprising: means for determining a cross product of the residual error; means for determining a dot product for the residual error; means for decrementing tfis cross product by an adjustment amount equivalent to a product of the dot product; of the input signal times a constant value if the cross product is greater than a piedetennined threshold; and means for incrementing the cross product by the adjustment amount if the cross product is greater than or equal to the predetermined threshold. 2:2;. The frequency tracking loop of claim 21, further including a ; loop filter that couples the frequency discriminator to the summer. 2h. A frequency discriminator apparatus having an input signal comprising a plurality of symbols, the apparatus comprising: a cross product generator, coupled to the input signal, for generating a cross produce of the input signal; a dot product generator, coupled to the input signal, for generating a dot product of the input signal; a first low pass filter, coupled to the cross product, for generating a filtered cross product; a second low pass filter, coupled to the dot product, for genci&img a filtered dot product; a multiplier coupled to the filtered dot product generator for generating an adjustment product: in response to the filtered dot product and a const 33 it value; a first multiplexing device having a first input coupled to the product and a second input coupled to a negative of die adjustment product, the second multiplexer selecting as an output one of either ths first input 01 the secorc input in response to the filtered cross product; a summer coupled to the filtered cross product generator and the output of the first multiplexing device, the summer generating a summation signal of the filtered cross product and the adjustment product; and a second multiplexing device having a first input coupled to the first low pass filter and a second input coupled to the summer, the second multiplexing device selecting as an output one of either the filtered cross product or die summation signal in response to the filtered dot product. 24. A method of providing frequency discrimination substantially as herein described with reference to the accompanying drawings.

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091-chenp-2004-form 18.pdf

091-chenp-2004-form 3.pdf

091-chenp-2004-form 5.pdf

091-chenp-2004-pct.pdf