CN104113504A - DRM receiver with analog and digital separation filter and demodulation method - Google Patents

Abstract

A digital radio mondiale (DRM) receiver and a demodulation method are disclosed. the DRM receiver comprises an analog and digital separation filter used for filtering and separating a DRM coded signal and a non-DRM coded signal of a composite RF signal received by the receiver. The DRM receiver contains a programmable down-sampling device and a programmable N-point Fast Fourier Transform (FFT) and is used for recover and demodulate an OFDM code element in the received DRM coded RF signal. The received signal is down-sampled at an integer rate, and N samplings are realized in a useful part of the OFDM code element for input to N-point FFT, wherein N equals to a power of 2. The down-sampling rate and the magnitude of FFT (N-point) are dependent on DRM coding and sending parameters, especially a robustness mode and spectrum occupancy. The receiver adopts the above structure and operation, the design is simplified, and filter order required by the analog and digital separation filter is reduced.

Description

There is DRM receiver and the demodulation method of analog-and digital-separation filter

Technical field

Present invention relates in general to communication control processor, more specifically, relate to a kind of method and receiver being used in digital radio receiver system.

Background technology

The digital radio world wide universal standard (Digital Radio Mondiale DRM) is a kind of open-standards digital radio system, this kind of radio system designs for low frequency (148.5 KHz are to 283.5 KHz), medium frequency (525 KHz are to 1705 KHz) and high-frequency (2.3 megahertzes are to 27 megahertzes) signal, and the digital radio world wide universal standard (DRM) even can be extended to the scope up to 120 megahertzes.DRM system specifications is described in the ES of ETSI (ETSI) 201 980 version 2 .2.1 (2005-10), is introduced into for reference at this.

Within DRM signal is designed to be adapted at existing amplitude modulation(PAM) (AM) broadcast channel and interval plan (based on 9 or 10 KHz interval/bandwidth), but the audio quality (near FM quality) of DRM signal is but obviously much better than current AM radio system signal.Video, audio frequency and other data can be transmitted within this DRM system.Current DRM regulation and stipulation according to the operation of (comprise 4.5,5,9,10,18 or 20 KHz, be sometimes referred to as " spectrum occupancy ") of various bandwidth mode.In addition, DRM signal can be broadcast with AM signal under simulcast mode simultaneously.

DRM system is used OFDM (OFDM), and this comprises the transmission of many narrow channels in parallel subcarrier.Within OFDM DRM system, can use various modulation schemes, such as Quadrature Phase Shift Keying (QPSK), 16-quadrature amplitude modulation (16-QAM) and 64-QAM.The quantity of subcarrier depends on selected robustness pattern and the channel width within DRM.At present, there are four kinds of healthy and strong sexual norm – A (for example, 226 subcarriers, 10 KHz bandwidth; 458 subcarriers, 20 KHz bandwidth), B (206; 410 carrier waves), C (138; 280 carrier waves) and D (88; 178 carrier waves), robustness pattern can be selected according to propagation conditions.4.8 and 72kb/s between bit rate scope can be reached, this depends on spectrum occupancy, robustness pattern, modulation technique and code rate.

Within DRM, OFDM carrier signal forms the summation of multiple subcarriers, and the base band data on each subcarrier is to use modulation technique (for example, QAM) to be modulated independently.Then, modulate main RF carrier wave with compound DRMOFDM signal.Using the benefit of OFDM is known for those skilled in the art, does not therefore need to have further described again.

Spacing between subcarrier and OFDM Baud Length change within DRM, and this depends on robustness pattern.For example, sub-carrier separation is 41.66 hertz under Mode A, and under Mode B, is 46.88 hertz.OFDM code element comprises Liang Bu Fen – useful part and protection interval.Under Mode A, Baud Length is 26.66 milliseconds, and useful part is 24 milliseconds, and protection interval is 2.66 milliseconds, and under Mode B, Baud Length is also 26.66 milliseconds, but useful part is 21.33 milliseconds, and protection interval is 5.33 milliseconds.Protection compartment is different from the ratio of the duration of useful code element, and this depends on pattern (A – 1/9, B – 1/4, C – 4/11, D – 11/14).

Although some prior art has proposed to use discrete Fourier transform (DFT) (DFT) to carry out demodulating ofdm signal, fast fourier transform (FFT) is but typically preferred, and reason is that it has reduced computational complexity.As a result, FFT processes (and reverse FFT (IFFT)) and in the system based on OFDM, is utilized to structure and recovery OFDM composite signal.

Specific prior art DRM receiver based on software, be called " dream (DREAM) receiver ", use intermediate frequency (IF) (from the conventional 455 kilo hertzs of IF down-conversions of standard heterodyne RF front end) the reception OFDM composite signal of 12 kilo hertzs and with 48 kilo hertzs of sampled signals.The DRM ofdm signal that dream receiver uses western fast fourier transform (FFTW) demodulation to receive.This is widely used freeware storehouse, for calculating DFT and special circumstances thereof.Although the program that uses distributors to optimize has more competitiveness, FFTW is not tuning for stationary machines.More precisely, FFTW makes its algorithm be adapted to hardware platform with planner, to increase performance.

In the dream receiver based on PC, after definite FFT window, the signal of 48 kilo hertzs of samplings is input to FFTW piece.All DRM robustnesses and spectrum occupancy pattern can need not be regulated with this frequency sampling, and DFT count (, the number of samples of the useful part of code element) is as follows: A Mo Shi – 1152; B Mo Shi – 1024; C Mo Shi – 704; D Mo Shi – 448.Four kinds of main algorithms are realized in FFTW, comprise Cooley-Tukey, Prime-factor, Rader and Bluestein.FFTW planner is measured the actual run time of different plans and is selected a fastest plan.FFTW also can provide so a kind of operator scheme, and wherein it returns to one " reasonably " plan rapidly, but this may not be the fastest.For the dream receiver based on PC, FFTW may be the reasonable implementation of DRM OFDM demodulation.

Use in FFT, the signal that uses in general number of samples (sometimes also referred to as " 2 power the points ") sampling of the power that equals 2 to wish is wished.But; because the ratio in DRM specification (referring to above-mentioned) between the code element of defined protection gap length and useful code element part (as implied above), so neither one robustness pattern (except B) can realize 2 power point simultaneously and realize integral point in protection interval in useful code element part.Therefore, in dream receiver, use FFTW to cause higher complexity than FFT.

Therefore, thus need a kind of new DRM receiver and method to use FFT to reduce computational complexity with demodulation DRM ofdm signal.This FFT can realize at hardware-such as the gate array (FPGA) of field-programmable, application-specific integrated circuit (ASIC) (ASIC) or (by corresponding programming) numeral or other signal processors.

As above annotating, DRM specification has been considered various simulcast mode, because current AM frequency spectrum is moved to the needed relative time of digital signal of DRM coding and the cause of cost.The radio hookup of DRM and AM signal sends and can simulate AM channel and DRM digital channel (for example, having the channel separation of 10 kilo hertzs between AM carrier frequency and digital reference frequency) is carried out by juxtaposition.Therefore all may there is a period of time in simulation (AM) and numeral (DRM) signal, simultaneously.Receiving in DRM coding and DRM receiver traditional analog AM signal, need separation filter.Because frequency band approaches, be difficulty and complicated so design such separation filter.For example, in robustness Mode A and spectrum occupancy pattern 0, may need to have the filter (interval between digital signal and analog signal is 83.33 hertz) of the instantaneous wave band that passes through wave band (subcarrier #2 is to the signal on #102) and 83.33 hertz of 2083.33 hertz.

Use conventional MATLAB design of filter instrument, and the filter parameter that hypothesis is wished is that the passband fluctuation of 1 decibel and the wave band that stops of 40 decibels are decayed, in sample frequency relatively high (100 kilo hertzs or larger), the rank of filter are just thousands of.

Therefore, need a kind of new DRM receiver and method, comprise Digital and analog separation filter, send for receiving and being separated in come in close proximity to each other within wave band the conventional simulation AM signal that sends and the digital signal of DRM coding.

Summary of the invention

According to an embodiment; a kind of digital radio world wide universal standard (DRM) receiver is provided; comprise: AD converter (ADC); for the compound RF signal receiving with the first sampling rate sampling, this compound RF signal comprises the signal of DRM coding and the signal of non-DRM coding; And down-sampler, for the composite signal of this reception of following sampling rate x down-sampling, x is positive integer herein.Mode discriminator, the output of being coupled to down-sampler, for determining the predetermined DRM parameter mode of signal and the signal of this definite DRM pattern of output instruction of the DRM coding receiving.A demodulator, is coupled to down-sampler, receives the signal of encoding through the DRM of down-sampling and is demodulated into multiple unit.This demodulator comprises programmable N point fast Fourier conversion (FFT), N is the integer that equals 2 power herein, and N is in response to the signal of this definite DRM pattern of instruction and is determined.

The method of the signal of a kind of demodulation digital radio world wide universal standard (DRM) coding is provided in another embodiment.The composite signal that comprises the signal of the digital radio world wide universal standard (DRM) coding and the signal of non-DRM coding is received, wherein the signal of this DRM coding is encoded according to predetermined DRM parameter mode, and digitally sampled with the first sampling rate, to generate complex digital signal sampling.According to this complex digital signal sampling of the first down-sampling speed x down-sampling, x is integer herein.The sampling of this complex digital signal is filtered and be separated into the signal of DRM coding and the signal of non-DRM coding.Determine the DRM parameter mode of signal and the signal of this definite DRM parameter mode of generation instruction of this DRM coding.Use programmable N point fast Fourier conversion (FFT) that the digital demodulation signal of the DRM of down-sampling coding is become to multiple unit, N is the integer that equals 2 power herein, and N is in response to the signal of this definite DRM pattern of instruction and is determined.

According to the following drawings, description and claim, to those skilled in the art, other technologies feature can easily become clear.

Brief description of the drawings

In order to understand more completely the present invention and advantage thereof, with reference now to below in conjunction with the given explanation of accompanying drawing, wherein identical numeral is specified identical object, in the accompanying drawings:

Fig. 1 is according to the block diagram of DRM receiver of the present invention; And

Fig. 2 is the details drawing in the treatment system shown in Fig. 1.

Embodiment

Fig. 1 illustrates the block diagram of receiver system 100, and receiver system 100 can operate signal and other analog signals of within given frequency range (low, in and high-frequency), receiving DRM coding.Other embodiment of receiver 100 also can use in the situation that not departing from scope of the present invention.

Before describing in more detail receiver 100, basic function and operation and the DRM coding of typical DRM transmitter first described.Term " signal of DRM coding " will be used for describing the coded signal of DRM system specifications according to described in ETSI ES 201 980 version 2 .2.1 (2005-10) (comprising any past or variant or version in the future) at this, be introduced into for reference at this.

The signal of DRM coding comprises at least three different channels that are organized into DRM superframe.These channels are called as (1) and access fast channel (FAC), (2) business description channel (SDC) and (3) MSC (MSC).FAC provides can the decode information of SDC and MSC of receiver that makes.SDC provides the additional information about channel, extra traffic and additional DRM feature.MSC sends the actual content that can be included in wherein, nearly comprises four streams of audio frequency or data.DRM transmitter can be selected between the difference configuration for SDC and MSC, depends on different condition and the error protection demand of radio transmitting channel.

DRM audio frequency and data for example, are typically incorporated in MSC after the audio coder according to hope (, MPEG-4 audio standard) coding audio data.Then according to use multilevel coding (MLC) the scheme MSC that encodes for the parameter (the error protection rank that these parameter-dependents are wished) of Bit Interleave, convolutional encoding and energy dissipation.Then use modulation scheme, for example, such as QAM (, 4,16 or 64) this bit stream is encoded.Similarly, use MLC and modulation scheme (identical or different for each channel) encoding D RM FAC and SDC.

In MSC, FAC and SDC, the information of coding and modulation is got up with reference pilot unit combination (this taken into account receiver is synchronizeed and channel estimating), will be input to the OFDM code element of reverse fast fourier transform (IFFT) in order to formation.According to DRM specification, protection interval/signal is added in each code element, in order to generate the OFDM composite signal of DRM coding.Then in carrier frequency, send this signal.In a kind of possible implementation, the output of IFFT can comprise plural I and Q signal, and the I/Q that i/q signal is used as in carrier signal sends.Other transmitters/transmission configuration and method also can be utilized, and this may be all known for those skilled in the art.

Turn to now Fig. 1, illustrate the block diagram according to the receiver 100 of one embodiment of the present of invention.Receiver 100 comprises antenna 102, for receive signal and other RF signals (signal of non-DRM coding) of radio frequency (RF) DRM coding on predetermined frequency band." other RF signals " can be included in any RF signal within predetermined frequency band, and the scope of this predetermined frequency band can be up to 30 hertz, or 85 hertz, perhaps higher, and can lowly reach about 100 kilo hertzs.These other RF signals can use AM, and FM or other modulation schemes are modulated.In a particular embodiment, these other RF signals are AM or FM signal.

Receiver front end 104 receives the RF signal of DRM coding according to known technology and circuit, carry out down-conversion, and generates and output intermediate frequency (IF) signal (for example, 455/465 kilo hertz).Alternatively, receiver front end 104 can also further be down-converted to base band.Output signal (no matter being IF or base band) is sampled with predetermined sampling rate and is used AD converter (ADC) 106 digitlizations.Determined that 384 kilo hertzs of sample frequencys (N is positive integer) that are multiplied by n are for receiver 100 provides different advantages herein, this will be illustrated more fully at this.In a specific embodiment of receiver 100, ADC moves with the sample frequency of 384 kilo hertzs.

In another embodiment, sample frequency is 1.536 megahertzes (384 kilo hertzs of x 4).Use this kind of sampling rate that the easier implementation of IQ demodulator is provided, IQ demodulator is 4 times of IF frequencies herein.Can (for example realize remaining frequency shift (FS) down-conversion by application coordination rotation digital computer (cordic), when IF is that 455 kilo hertzs and sampling adopt in 1.536 hertz, after the process based on 4 times of IF, remaining frequency shift (FS) is 455 to deduct 1536/4=71 kilohertz, then correct 71 kilo hertzs of side-play amounts with cordic, the frequency offset between transmitter and receiver also can be repaired).Be to be understood that if utilized different IQ demodulation design or scheme, so also can select 384*N kilohertz sample frequency.

It will also be understood that DRM signal can use any known modulation scheme to be modulated onto on RF carrier wave, but in one embodiment, RF signal is the RF signal of IQ modulation.In the embodiment shown in Figure 2, the RF signal of reception is the RF signal of orthogonal mixing, comprises therein plural I and Q signal (IQ modulation), and this RF signal of receiver front end 104 down-conversions, in order to generate and output IF signal.Therefore, in this embodiment, IQ demodulation occurs in after IF signal digital.Alternatively, IQ demodulation (or other RF demodulation techniques, can before by ADC 104 digitlizations, realize if you are using).

As shown, what generated by ADC 106 is received by signal processing system 108 through digitized IF signal (adopting the form of digital sample), signal processing system 108 is in one embodiment be demodulated to complex signal (I and Q digital signal) through digitized IF signal, realize the conversion (this may can comprise mixing/DDC) of IF to base band, and process digital baseband signal (digital signal of DRM coding) to extract (pilot cell, FAC, within SDC and MSC channel) coded data.Just as will be understood, the digital signal of DRM coding can be used as the complex signal processing at one or more point along path according to hope, also can be used as real number signal processing.Treatment system 108 is carried out various functions, comprises IQ demodulation, and IF is to the conversion of base band, time and symbol synchronization; sample, filtering, is used FFT, the OFDM demodulation that carrier frequency and clock frequency side-play amount are corrected again; channel equalization, and data are extracted and decoding (MSC, FAC, SDC; With final voice data and other data, with generating digital output signal (business, data, voice data).

Treatment system 108 can be used hardware, or the combination of hardware and software (with/firmware) realizes.In one embodiment, treatment system 108 comprises processor or other hardware device (not shown), in order to carry out firmware/software instruction (firmware/software), to implement processing or the function identified.In addition, any one shown in Fig. 2 or in specific or function described here can combine and be realized with software, hardware or its.

In another embodiment, treatment system 108 also comprises analog-and digital-(A & D) signal separation filter, signal and output the second audio signal (adopting number format or analog format) for filtering from the DRM coding of other RF signal (signal of non-DRM coding, such as AM or FM signal).Just as will be understood, when mentioning in A & D separation filter, term " simulation " at the frequency band of hope (for example refers to, AM, FM) signal (signal of non-DRM coding) that the traditional simulation within receives, though " simulation " signal can be digitized in receiver 100 and afterwards in digital form processing be also like this.

Determined that 384 kilo hertzs of sample frequencys (n is positive integer) that are multiplied by n are for receiver 100 provides different advantages herein, this will be illustrated more fully at this.In an embodiment of receiver 100, ADC 202 operates in the sample frequency of 1.536 megahertzes (384 kilo hertzs of x4), and in another different embodiment, sample frequency is 384 kilo hertzs.Will be appreciated that it is favourable utilizing the ADC sample frequency of 384*n kilohertz.

Forward now Fig. 2 to, show the details drawing according to the treatment system 108 of an embodiment.This treatment system comprises IQ demodulator blocka 200, for receive digitized IF signal from ADC 106.IQ demodulator 200 with the signal of frequency (or within frequency range of hope) this reception of demodulation of hope and generation with export corresponding DRM baseband signal (adopting the plural I and the Q signal form that separate).This moves to zero (or close to zero) the centre frequency of the DRM frequency spectrum receiving in general.

Utilize in the DRM of base band signal, symbol synchronisation block 204 is processed DRM baseband signal and is determined the beginning of enabling synchronous new OFDM code element.This process can according to any known technology-such as and the input of time delay between relevant realization.After synchronous, digital DRM signal sampling (being synchronized to OFDM code element) is imported into down-sampler 206 able to programme (also referred to as sampler again, low-converter, or withdrawal device).Down-sampler 206 down-sampling digital signal samples or the number of digital signal samples is reduced to predetermined multiple x (for example,, for x=12, using every the 12nd sampling and other sampling to be just dropped).This has reduced sampling rate effectively, and therefore being input to the number of samples of digital signal samples of down-sampler 206 or down-sampling (sampling again) rate reduction x doubly.For example, be that 384K samples/sec (384 kilo hertzs) and down-sampling speed are 36 (x=36) if be input to the speed of the digital signal samples of down-sampler 206, this output will equal 10.667K samples/sec so.

Will be appreciated that down-sampler 206 can support the down-sampling of less point of several times (for example, 16.0001) in addition, so just can realize the correction in the clock frequency skew of this point.

Down-sampling speed be programmable and in response to or send or coding parameter (for example, OFDM parameter) or selected generating the pattern of utilizing in the DRM signal of coding according to one or more DRM.These parameter/mode comprise robustness and spectrum occupancy.DRM pattern is any robustness pattern or spectrum occupancy pattern (or their combination) based on what utilize.After the applicable DRM pattern of signal that identifies received DRM coding, this robustness and/or spectrum occupancy mode decision or (control) down-sampling speed of effectively selecting or programme.

The digital signal samples of the down-sampling of exporting from down-sampler 206 is received at analog-and digital-(A & D) separation filter 208.The signal of DRM that 208 filtering of A & D separation filter are wished coding and itself and the signal of other hope within given channel or bandwidth are separated out.For example, in simulcast mode, the signal of this reception be included in juxtaposed broadcast singal (for example, AM, FM) within given channel or bandwidth and DRM signal these two.The recovery of these two kinds of signals is wished.Filter 208 distinguishes out these two kinds of signals or be separated out for further processing.This will described below more fully.If the routine receiving broadcast secondary signal is undesirable or unwanted, A & D separation filter 208 just can be left in the basket so.

(or non-filtered) digital signal samples through filtering of exporting from A & D separation filter 208 is imported into OFDM demodulation block 210.Ofdm demodulator 210 uses the programmable N point FFT 211 demodulating ofdm signals of the power with 2, and (power that N equals 2 herein, this power is positive integer.In one embodiment, FFT 211 can be programmed, so that make N=128,256 or 512.FFT 211 can use hardware, software or their combination realize, and in one embodiment, FFT uses the embedded type C software of carrying out in processor to be realized, described processor for example, such as digital signal processor or other processors (, arm processor).Each individual unit in ofdm demodulator 210 processing digital signal samplings and recovery OFDM code element.

Similar with programmable down-sampler 206, the points N of FFT 211 (or some size) be programmable and in response to or send or coding parameter (for example, OFDM parameter) or selected generating the pattern of utilizing in the DRM signal of coding according to one or more DRM.These parameter/mode comprise robustness and spectrum occupancy.After the applicable DRM pattern of signal that identifies received DRM coding, robustness and/or spectrum occupancy mode decision or (control) points N of effectively selecting or programme.

(or non-filtered) digital signal samples through filtering of exporting from A & D separation filter 208 is also imported into mode discriminator piece 212.Mode discriminator 212 checks the signal of DRM coding and determines the DRM pattern (robustness and/or spectrum occupancy parameter) of this signal.Accordingly, mode discriminator 212 sends to down-sampler 206 control signal, and down-sampler 206 is according to definite robustness and/or the control of spectrum occupancy pattern or its down-sampling speed of programming.Similarly, from the output control of mode discriminator 210 or be programmed in the points N of the FFT 211 within ofdm demodulator 212.And then A & D separation filter 210 also receives this output, and A & D separation filter 210 is used to according to definite spectrum occupancy mode tuning or amendment (or programming) filter parameter.

Should be appreciated that at first, when not yet determining in DRM robustness pattern, do not carry out FFT (therefore the point of FFT is incoherent).The default mode that mode discriminator 212 uses is robustness Mode B and spectrum occupancy pattern 0.Why this is the beginning that such reason is the signal receiving at DRM, only has FAC channel between [0,5 kilo hertz].

The output of OFDM modulator 212 is imported into carrier frequency offset and estimates piece 214, and time synchronized piece 216 and clock frequency side-play amount are estimated piece 218.Carrier frequency offset estimator block 214 is for the frequency offset between carrier wave and the local oscillator estimating to send.This can be by estimating that by the frequency pilot of DRM signal side-play amount completes.The side-play amount output of carrier frequency offset estimator 214 is imported into IQ demodulator 202 and is used to regulating frequency downconversion process.Synchrotimer 216 is for estimating time (phase place) side-play amount between transmitter and receiver, and its output is imported into symbol synchronization device 204, the phase place of the signal of encoding in order to the DRM regulating in succession.This can carry out side-play amount and completing estimated time by the gain pilot tone of DRM signal.Clock frequency side-play amount estimator 218 is for estimating the clock frequency side-play amount between transmitter and receiver, and its output is imported into down-sampler 206, in order to regulate local oscillator.Clock frequency is corrected (this corrects the clock frequency of DRM signal with NCO and interpolater) in numeric field.

The output of OFDM modulator 212 is also imported into equalization block 220, and the gain pilot frequency mode of the known transmission of equalization block 220 use is estimated channel transfer functions.Then utilize the inverse function of the channel transfer functions of estimating to be corrected OFDM unit.

After equilibrium, DRM signal is decoded by DRM decoder 222.Decoder 222 uses the time pilot tone of DRM or the pilot tone that gains to determine the beginning of DRM frame, in order to determine send frame starting point (, which code element is the first code element that sends frame) and these unit are separated to three information Xin Dao – MSC, in SDC and FAC.FAC provides and makes the decoder 222 can SDC and the information of MSC.SDC provides the additional information about channel, extra traffic and additional DRM feature.This MSC sends the actual content that can be included in wherein, nearly comprises four streams of digital audio or data.Audio decoder (not shown) decoding digital audio, for further being processed by receiver 200.

The present invention describes the DRM receiver and the OFDM demodulation scheme that utilize FFT, and in order to carry out demodulating ofdm signal with programmable N point FFT, N depends on DRM pattern herein.In one embodiment, the first sampling rate is selected to for guaranteeing has in the useful part of OFDM code element in OFDM code element n _u =x2 ^mindividual sampled point, and guarantee to have in protection interval n _g =y sampled point, x and y are integers herein.Then the second sampling rate or frequency are chosen as so that this FFT can be realized with N point, this is in the useful part of OFDM code element, N=2 ^mto equal 2 power.This causes having the sampling y/x-floor (y/x) of mark in OFDM code element protection interval.Under the situation without any the impact that can perceive or change on OFDM demodulation, this fractional sampling can be left in the basket, and reason is only to utilize the useful part of this code element among demodulation.

Having determined should be the integer multiple of 1/T (12 kilo hertzs) as sample frequency, in order to guarantee to have the sampling of integer number in the useful part of OFDM code element.

And, for the FFT 211 of point of 2 the power that utilizes decreased number carrys out demodulating ofdm signal, and understand the different DRM pattern (for example robustness and spectrum occupancy pattern) that has, determine the Minimum sample rate of 384 kilo hertzs that is converted to the computational complexity for simplifying this design and reduction DRM receiver 100 for the lowest common multiple of the needed sample frequency of different mode.Just as will be understood, sampling can complete with the integer multiple of 384 kilo hertzs of sampling rates.

Count and in Table I, list below the OFDM of each DRM pattern demodulation sub-carriers number and FFT minimum:

Table I.

According in the useful part of OFDM code element for the number of samples of the hope in N point FFT, in Table II, list down-sampling speed (supposing that basic sampling rate is 384 kilo hertzs), A herein, B, C and D are robustness patterns, x is spectrum occupancy pattern:

x	A	B	C	D
					0	72	64	\	\
1	72	64	\	\
					2	36	32	\	\
3	36	32	22	28
					4	18	16	\	\
5	18	16	11	14

Table II.

If the digital sample speed of the RF signal of the DRM receiving coding is 384*N kilohertz, down-sampling speed x will be adjusted to x=x*n so, suppose not insert down-sampling between ADC 104 and down-sampler 206.If middle down-sampling (integer) has occurred, sampling rate x should correspondingly be regulated so.One aspect of the present invention provides the DRM signal receiving should be sampled with the speed of 384*N kilohertz at first, N is integer herein, and down-sampling produces (in an OFDM code element) number of samples that is input to FFT, this number of samples equals according to the determined number N of use DRM parameter sending mode shown in Table I, the power that N equals 2 herein.Down-sampler 206 can comprise single down-sampler, multiple down-samplers and/or configured or comprise one or more down-sampler being provided as along a part for another element of the signal path receiving according to being provided as along one or more down-sampler of a part of another element of the signal path receiving.But, down-sampler 206 is realized as in order to down-sampling effectively with the digital sample that sampling rate was produced of ADC 104 or the number of the digital sample that this was produced is reduced to the number of samples of (in the OFDM code element being received), this number of samples equals N, and down-sampling speed x generally equals an integer.

Will be appreciated that: DRM receiver 100 except shown in and described those assemblies or function, can also comprise assembly or function, but what describe and illustrate is only that those skilled in the art understand those assemblies and the function of wanting required for the present invention.

The general operation of DRM receiver 100 is described now.The RF signal of DRM coding is received and is digitized (ADC) with the sampling rate that equals 384 kilo hertzs of integer multiples.The signal of the DRM coding receiving is examined to determine the DRM pattern of transmission, comprises robustness pattern (A, B, C, D) and spectrum occupancy pattern (0 to 6).The pattern (one or more) definite according to these, digital signal samples by according to determined DRM pattern down-sampling predetermined multiple (referring to Table II), and the N point FFT that the signal sampling of the DRM of down-sampling coding is imported into 2 power is for demodulation.This FFT is programmed to have the FFT that N is ordered, and number N is based on determined pattern (one or more) (referring to Table I) herein.

Again turn to Fig. 2, A & D separation filter 208 corresponding to the second conventional broadcast singal (is for example exported, AM, FM) secondary signal (signal 2), and processed routinely by the such (not shown) according to hope (such as converting analog format to and exporting this audio signal to audio tweeter).

Although the final purpose of DRM system is to AM, the digitlization of FM broadcast, before this will be implemented, DRM signal demand exists simultaneously.Because DRM signal be designed to will with the identical broadcasts wave band of AM and FM (the RF signal of non-DRM coding) in work, simulate AM/FM signal and DRM digital signal juxtaposition is carried out so use DRM and the data of AM/FM and the radio hookup of business (or multicast) to send by handle.Other details can be referring to ETSI ES 201 980 version 2 .2.1.As a result, DRM receiver 100 also can receive the signal (, composite signal) that appears at the non-DRM coding within channel width.A & D separation filter 208 filtering and process composite signal and these two kinds of signals are separated.But, within frequency spectrum, be close because these adjoin signal, so be difficult in general design such filter.For example, in robustness Mode A and spectrum occupancy pattern 0, the interval between digital and analog signaling is only 41 2/3 x 2+250/3 hertz, so the design of this filter is complicated.

In order to reduce the design complexity of A & D separation filter 208, low sample frequency is wished.This receiver 100 designs (for example, having programmable down-sampler 206 and programmable FFT 211) and can realize for the relative simpler design of filter with reasonable filter rank.

Because the sampling fundamental frequency of 384 kilo hertzs described herein can cause relatively high filter rank, so except benefit described above, the down-sampling of the digital sample in the signal path before A & D separation filter 208 also can make filter have lower rank.Use DRM signal wherein to have the example of robustness Mode A and spectrum occupancy pattern 0, down-sampling speed is 72 (384 kilo hertzs/72), and the useful part of OFDM code element has 128 to count.Analog-and digital-separation filter design under this sample frequency (384 kilo hertzs/72) is comparatively speaking simpler.Be 1 decibel and stop wave band and decay to 40 decibels in the situation that at passband fluctuation, the same with the aforesaid example in the situation that, the rank of separation filter should be 91(instead of several thousand).

The actual disposition of A & D separation filter 208 does not provide description at this, reason is that those of ordinary skill in the art will be understood that and recognize that specific implementation can be different, depend on method for designing hope or that utilize and parameter.

It may be favourable being illustrated in some word of using in patent document and the definition of phrase.Term " comprise " and " comprising " with and derivative, the meaning is unrestrictedly to comprise.Term " or " be inclusive, the meaning be and/or.Phrase " be associated " and with " it is associated " with and derivative, can mean comprise, be included, interconnect, comprise, be included, be connected to it or be connected, be coupled to it or with its coupling, can communicate with it, cooperate mutually with it, interlock, juxtaposition, close to, join with it or receive mutually, have, have characteristic etc.Term " controller " means that any equipment, system or its control a part at least one operation.Controller or function can realize in hardware, firmware, software or their a certain combination of at least two.Be associated with any specific controller functional can be centralized can be also distributed, and no matter be local or remotely concentrate or distribute.

Although the method that the present invention has described some embodiment and has generally been associated, the amendment to these embodiment and method and change will be also well-known to those skilled in the art.Therefore, above the description of exemplary embodiment is not limited or limits the present invention.In the case of not departing from the spirit and scope of the present invention that limited by following claim, also can make other change, substitutions and modifications.

Claims (20)

1. the digital radio world wide universal standard (DRM) receiver, comprising:

AD converter (ADC), is configured to the compound RF signal with the first sampling rate sampling reception, and this compound RF signal comprises the signal of DRM coding and the signal of non-DRM coding;

Down-sampler, is configured to the composite signal of this reception of following sampling rate x down-sampling, and x equals the first sampling rate divided by the positive integer that is greater than 1 herein;

Analog-and digital-separation filter, is configured to receive the composite signal of down-sampling and the signal of the signal of this DRM coding and non-DRM coding is separated;

Mode discriminator, the output of being coupled to down-sampler, is configured to the predetermined DRM parameter mode of the signal of determining received DRM coding and exports the signal of indicating this definite DRM pattern; With

Demodulator, be coupled to down-sampler, and be configured to the signal of the DRM coding that receives down-sampling and be demodulated into multiple unit, this demodulator also comprises programmable N point fast Fourier conversion (FFT), N is the integer that equals 2 power herein, and N is in response to the signal of this definite DRM pattern of instruction and is determined.

2. receiver as claimed in claim 1, wherein the first sampling rate is the integer multiple of 384 kilo hertzs.

3. receiver as claimed in claim 1, wherein N is one of 128,256 and 512.

4. receiver as claimed in claim 1, wherein DRM parameter mode depends on robustness pattern and spectrum occupancy pattern.

5. receiver as claimed in claim 1, wherein down-sampling speed x is programmable and depends on DRM pattern.

6. receiver as claimed in claim 1, wherein down-sampling speed x equals integer, so that when the first sampling rate is divided by down-sampling speed x, make result equal to sample from the Integer N of the useful part of an OFDM code element, and wherein N is the integer that equals 2 power.

7. receiver as claimed in claim 6, wherein N is one of 128,256 and 512.

8. receiver as claimed in claim 7, wherein N depends on robustness pattern and the spectrum occupancy pattern of defined in DRM specification, so that equal in 0 or 1 when robustness pattern equals A or B and spectrum occupancy pattern, make N equal 128, when equaling A or B and spectrum occupancy pattern, robustness pattern equals in 2 or 3, make N equal 256, and equal, in 4 or 5, to make N equal 512 when robustness pattern equals A or B and spectrum occupancy pattern.

9. receiver as claimed in claim 1, also comprises:

Decoder, the described unit and described unit is separated to quick access channel (FAC) of being configured to decode, in business description channel (SDC) and MSC (MSC), and wherein MSC comprises voice data.

10. receiver as claimed in claim 1, wherein analog-and digital-separation filter has the filter rank that are less than 100.

11. 1 kinds comprise the method for the compound RF signal of the signal of the digital radio world wide universal standard (DRM) coding and the signal of non-DRM coding for demodulation, the method comprises:

Reception comprises the composite signal of the signal of the digital radio world wide universal standard (DRM) coding and the signal of non-DRM coding, and wherein the signal of DRM coding is encoded according to predetermined DRM parameter mode;

With the first sampling rate composite signal of digitally sampling, to generate complex digital signal sampling;

According to the first down-sampling speed x down-sampling complex digital signal sampling, x equals the first sampling rate divided by the positive integer that is greater than 1 herein;

The signal of the complex digital signal sampling of filtering down-sampling and separation DRM coding and the signal of non-DRM coding;

Determine DRM coding signal DRM parameter mode and generate the signal of the definite DRM parameter mode of instruction; With

Use programmable N point fast Fourier conversion (FFT) that the digital demodulation signal of the DRM of down-sampling coding is become to multiple unit, N is the integer that equals 2 power herein, and N is in response to the signal of this definite DRM pattern of instruction and is determined.

12. methods as claimed in claim 11, also comprise the speed sampling of the integer multiple that equals 384 kilo hertzs.

13. methods as claimed in claim 11, wherein N is one of 128,256 and 512.

14. receivers as claimed in claim 11, wherein definite DRM parameter mode depends on robustness pattern and spectrum occupancy pattern.

15. receivers as claimed in claim 11, wherein down-sampling speed x is variable, and depends on definite DRM parameter mode.

16. methods as claimed in claim 11, wherein down-sampling speed x equals integer, so that when the first sampling rate is divided by down-sampling speed x, make result equal to sample from the Integer N of the useful part of an OFDM code element, and wherein N is the integer that equals 2 power.

17. methods 16 as claimed in claim, wherein N is one of 128,256 and 512.

18. methods 17 as claimed in claim, wherein N depends on robustness pattern and the spectrum occupancy pattern of defined in DRM specification, so that equal in 0 or 1 when robustness pattern equals A or B and spectrum occupancy pattern, make N equal 128, when equaling A or B and spectrum occupancy pattern, robustness pattern equals in 2 or 3, make N equal 256, and equal, in 4 or 5, to make N equal 512 when robustness pattern equals A or B and spectrum occupancy pattern.

19. methods as claimed in claim 11, also comprise:

Decode described unit and described unit is separated to quick access channel (FAC), in business description channel (SDC) and MSC (MSC), wherein MSC comprises voice data.

20. methods as claimed in claim 11, wherein the sampling of the complex digital signal of filtering down-sampling is to utilize the filter on the rank that are less than 100 to carry out.