CN1922796A - Frequency generation for a multi-band OFDM based ultra wide-band radio - Google Patents

Abstract

The present invention, generally speaking, provides for generation of at least three local oscillator signals for receiving a communication signal occupying corresponding sub-bands of a frequency band using one or more frequency synthesizers (e.g., PLLs or the like) and one or more single sideband mixers. In accordance with certain embodiments, only one single sideband mixer is encountered along the output path of a given local oscillator signal, thereby reducing spurs. In accordance with certain other embodiments, three local oscillator signals are generated continuously.

Description

Frequency based on multi-band based ultra wide-band radio OFDM produces

Technical field

The present invention relates to broadband RF communication system, particularly ultra broadband (UWB) communication system.

Background technology

Since in February, 2002, under the condition of FCC report and regular 02-48 defined, ultra-broadband signal has been legal in the U.S..In brief, the UWB signal is not able to the power spectral density emission more than-41.2dBm/MHz in the frequency band from 3.1GHz to 10.7GHz.Elsewhere, even need further to reduce this power and think that protection is existing professional.Because describe Power Limitation with power spectral density, transmitting power and bandwidth are proportional, thus be desirably in occupied bandwidth as much as possible in economy and the feasibility restriction, and maximize possible link range thus.Yet, in view of the RF path loss that increases along with carrier frequency, and the noise factor of the semiconductor device that increases, initial interest concentrates on the frequency spectrum of developing 3.1-4.9GHz.

Formed two competition tests suggestions that are used for UWB, supported by Motorola and another is supported by the association of company that is called as multi-band OFDM alliance (MBOA) for one.MBOA-OFDM (hereinafter " MB-OFDM ") system uses the existing WLAN notion of 802.11a and 802.11g in a large number.This ofdm signal is become by 128 sub carrier group.These carrier occupancies 528MHz is so this subcarrier spacing is 4.125MHz.Because the carrier spacing is 4.125MHz, causing the OFDM symbol lengths must be 1/4.125e6=242.42ns.Consider intersymbol interference, zero-energy prefix of 1/4 of using this symbol lengths (60.6ns) replaces more traditional cycle prefix.Increased the protection period (9.47ns) of 5 samplings at last.Total OFDM symbol lengths is 312.5ns.

5 of 128 subcarriers are set to zero at band edge, thereby actual occupied bandwidth only is 507.375MHz (slightly being wider than desired 500MHz).In addition, in 128 subcarriers 100 beared informations are only arranged; Other or pilot tone, user-defined, perhaps be zero.The tone of 100 beared informations transmits the QPSK modulation, thereby each provides 2 bits, and perhaps each OFDM symbol provides 200 bits.Thereby total information speed is (200/312.5e-9), perhaps 640Mbps.After considering code redundancy, the maximum protection data rate is 480Mbps (3/4 rate code).

As mentioned above, simple use OFDM causes the frequency spectrum that takies only to surpass 500MHz, and it is lower than 1/3rd of available UWB frequency spectrum under the 5GHz.Because through-put power and occupied bandwidth are proportional, do not address this problem and to have significant effects to effective range.The MB-OFDM standard uses 3-frequency band jump scheme doubly to increase with the 3-that realizes bandwidth.The method that adopts is according to the continuous OFDM symbol of jump sequence emission that pre-determines length 6 in different frequency bands.These jump sequence are designed to the conflict between the microgrid that energy minimization do not coordinate and are known as T/F interlacing scan (TFI:Time-FrequencyInterleaving) sign indicating number.Type sequence comprise 1,2,3,1,2,3}, 3,2,1,3,2,1}, 1,1,2,2,3,3} or the like, wherein a concrete 528MHz frequency band is represented in each index.

How to express down from the uncoded bit rate of basic 640Mbps and obtain PHY-SAP data rate from 53.3 to 480Mbps, wherein introduce redundant by three approach, comprise convolutional encoding (speed 1/3,11/32,1/2,5/8 and 3/4), import (introducing 1/2 factor) and temporal extension to the conjugation symmetry of IFFT, wherein complete OFDM symbol can repeat on different frequency.

Message transmission rate (Mb/s)	Modulation	Code rate (R)	Conjugation symmetry input to IFFT	Temporal extension factor (TSF)	Full expansion gain	The coded-bit of every OFDM symbol (NCBPS)
							53.3	QPSK	1/3	Be	2	4	100
55	QPSK	11/32	Be	2	4	100
							80	QPSK	1/2	Be	2	4	100
106.7	QPSK	1/3	Not	2	2	200
							110	QPSK	11/32	Not	2	2	200
160	QPSK	1/2	Not	2	2	200
							200	QPSK	5/8	Not	2	2	200
320	QPSK	1/2	Not	1 (not expansion)	1	200
							400	QPSK	5/8	Not	1 (not expansion)	1	200
480	QPSK	3/4	Not	1 (not expansion)	1	200

Fig. 1 has shown the sub-band configuration in the MB-OFDM UWB motion.Sub-band is divided into group (group A, group B, group C and group D).Three sub-frequency bands of initial embodiment plan utilization group A.Also advised the possibility of seven frequency bands, the sub-band of use group A and C.Sub-band among group B and the D is retained at present to using possible future.

Referring to Fig. 2, block diagram shows and is used to produce following three frequencies (is unit with MHz): 3432,3960 and 4488 known MB-OFDM UWB receiver frequency generator.(all frequency values that here provide unless otherwise mentioned, all are unit with MHz.) PLL 201 that is coupled to local oscillator 203 produces 4224 frequency.This signal is applied to two different paths 210 and 220.First path is connected directly to 4224 signals an input of monolateral band (SSB) frequency mixer 231.The output signal of SSB frequency mixer is required centre frequency, that is, and and 3432,3960 or 4488.

Second path comprises another SSB frequency mixer 221, divider 223 and 225 and selector 227.4224 input signals divided by factor 8 and divided by 2, are applied to 264 signals of an input of selector by continuously with generation.264 signals also are applied to an input of SSB frequency mixer.Other input to the SSB frequency mixer is 528 signals that obtain after first divider 223.The output of SSB frequency mixer is applied to 792 signals of other input of selector.

In the manner described above, second path 220 produces 264 and 792 frequency.The selected device 227 of one of them frequency is selected and is applied to second of SSB frequency mixer 231 to import to produce required centre frequency.Particularly, when second path produces 264 signals, the signal of SSB frequency mixer output 4224 ± 264, promptly 4488 and 3960.Although not shown in this figure (or follow-up figure), SSB frequency mixer 231 produces summation and difference ("+1 and-1 ") signal, and gate circuit is used to select required centre frequency.When second path produces 792 signals, the signal of SSB frequency mixer output 4224 ± 792, i.e. 5016 (not using) and 3432.

The SSB frequency mixer also typically produces and contains the significantly output signal of " burr " (that is unwanted frequency composition) except having considerable area and energy requirement.As shown in Figure 2, when multichannel SSB frequency mixer was cascaded connection, the electromotive force of unwanted burr was greatly improved.In addition, because once produce only single required frequency, be effective and stable in needs so requirement of system design is forced to guarantee emending frequency.Therefore, need frequency generator to overcome the problems referred to above.

Summary of the invention

Generally speaking, the present invention (for example stipulates to use one or more frequency synthesizers, PLL or the like) and one or more single sideband mixer, produce at least three local oscillator signals, take a signal of communication of the respective sub-bands of a frequency bandwidth with reception.According to some embodiment, only run into a single sideband mixer along the outgoing route of given local oscillated signal, thereby reduced burr.According to some other embodiment, three local oscillated signals are produced continuously.

Description of drawings

The present invention can understand from following specification in conjunction with the accompanying drawings more fully.In the accompanying drawing:

Fig. 1 shows the figure of the subband structure in the MB-OFDM UWB motion.

Fig. 2 is the block diagram of known MB-OFDM UWB receiver frequency generator;

Fig. 3 is the block diagram according to the frequency generator of one embodiment of the invention;

Fig. 4 is the block diagram of another embodiment of frequency generator;

Fig. 5 is the block diagram of a modification of the frequency generator of Fig. 4;

Fig. 6 is the block diagram of another modification of the frequency generator of Fig. 4;

Fig. 7 is the block diagram of the further embodiment of frequency generator;

Fig. 8 is a table, has summarized the operation of the frequency generator of Fig. 7;

Embodiment

With reference now to Fig. 3,, block diagram shows the frequency generator according to one embodiment of the invention.Two PLL 310 and 320 that driven by shared crystal oscillator XO are provided.The one PLL comprises a VCO, VCO1, and it receives control signal 311 and produces identical output signal 313 and 315.The output signal of benchmark divider 317 downward frequency division crystal oscillators and with the signal application that produces to frequency/phase comparator 319.Similarly, the output signal of output divider 318 downward frequency division crystal oscillators and with the signal application of generation to frequency/phase comparator 319.Frequency/phase comparator 319 produces the error signal of being filtered by loop filter 316 so that produce control signal 311.In the embodiment of this explanation, a PLL produces 528 frequency, and it equals the sub-band gap.

The 2nd PLL 320 has similar configuration.In the embodiment of this explanation, it produces 3960 frequency, is the centre frequency of sub-band #2.The output signal of first and second PLL mixes the frequency to produce 3432 and 4488 in SSB frequency mixer 331, correspond respectively to sub-band #1 and #3.

Notice that in above-mentioned embodiment described below and other embodiment, one or more VCO can move on some channelized frequencies, with being illustrated by the related output signal of downward frequency division.So in some cases configuration can be simplified the design of VCO.In addition, can use the frequency synthesis technique that is different from PLL, for example synthetic (DDS) or delay lock loop (DLL) of Direct Digital.

Replacing embodiment illustrates in Fig. 4.In this embodiment, the frequency of PLL1 generation 8976 and PLL2 produce 6864 frequency.Use divider 401 and 403 with these frequencies divided by 2 to obtain 4488 and 3432 frequency, correspond respectively to sub-band #3 and sub-band #1.Therefore, in this embodiment, the frequency that is used for two sub-frequency bands of three sub-frequency bands is directly produced, and the result has reduced burr.Directly in two frequencies that produce is sub-band #3, because existing spectrum application, it may need the maximum burr filtration needs that requires.Be used for the frequency of sub-band #3 by direct generation, and use one or more SSB frequency mixers (and the burr that produces) to produce sub-band #3 to compare, filter and require to be lowered.

The frequency quilt that is used for sub-band #3 and sub-band #1 is once more downwards divided by 2 (405,407), and the frequency that produces is mixed together in SSB frequency mixer 409 to obtain to be used for the frequency (4488/2+3432/2=7920/2=3960) of sub-band #2.

The modification of the clock generation circuit of Fig. 4 is illustrated respectively in Fig. 5 and 6.The specific frequency that is produced by PLL and the specific structure of divider may have a lot of reasonable disposition, image pattern 5 and 6 typical embodiments explanation the same.

Though the three sub-band systems of sub-band #1-3 are used in the anticipation of original M B-OFDM scheme, other system can expand the combination of using different three sub-frequency bands, perhaps can use a lot of sub-bands.For example, four are used for additional available sub-band is sub-band #6-9, corresponds respectively to 6336,6864,7392 and 7920 frequency.

Referring to Fig. 7, shown clock generation circuit can produce above-mentioned all frequencies.In the clock generation circuit of Fig. 7, the frequency that is produced by PLL1 and PLL2 is respectively 7392 and 12672.7392 signals are corresponding to sub-band #8 and directly exported.It also is imported into SSB frequency mixer 701 and is used to produce sub-band #1-3, and 6,7 and 9.By downward frequency division, wherein K can be 2,3 or 6 to 12672 signals by programmable 1/K divider 703, and the back is 1/4 divider 705.The output signal of 1/4 divider is imported into the SSB frequency mixer.The output signal that produces by the SSB frequency mixer comprises sub-band # 6,7 and 9 frequency.These frequencies of back are sub-band #1, the twice of 2 and 3 frequency separately.Therefore obtain sub-band # 1,2 and 3 frequency by output signal divided by 2 (707) with the SSB frequency mixer.

How the circuit that Fig. 8 has concluded Fig. 7 produces each related frequency, and sub-band #8 is an exception, is directly to produce.

Above-mentioned clock generation circuit uses two PLL and a SSB frequency mixer.Other clock generation circuit of other embodiment can use the PLL and/or the SSB frequency mixer of more or lesser number according to the present invention.

Referring to Fig. 9, show clock generation circuit, it uses two PLL 910 and 920 and two SSB frequency mixers 931 and 933.The one PLL directly produces the frequency that is used for sub-band #3.The frequency that the 2nd PLL produces is the twice (1056) in sub-band gap.This frequency by divided by 2 (935) to obtain to equal the frequency (528) in sub-band gap.

Two SSB frequency mixers are used for producing the frequency that is respectively applied for sub-band #1 and 2.In order to produce the frequency of sub-band # 1,4488 signals mix with 1056 signals.In order to produce the frequency of sub-band # 1,4488 signals mix with 528 signals.

Referring to Figure 10, clock generation circuit is illustrated and uses single PLL 1010 and three SSB frequency mixers 1011,1013 and 1015.PLL directly produces the frequency of sub-band #3.Frequency mixer 1011 and 1013 produces the frequency of sub-band # 1 and 2 respectively, uses the frequency of sub-band #3 as an input.Other input is 1056 the frequency that equals 528 the frequency in sub-band gap (SSB frequency mixer 1013) or equal the twice in sub-band gap (SSB frequency mixer 1015).The latter's frequency produces by a series of two divided-frequency divider 1017 and SSB frequency mixer 1015.The final output signal (i.e. 264 frequency) that SSB frequency mixer 1015 receives the frequency of sub-band #3 (4488) and divider chain is as importing, and produces 4224 frequency as output signal.Divider chain produces 2112,1056 and 528 intermediate frequency.

In the embodiment of Figure 10, three local oscillator signals are produced continuously, have simplified system design.

It will be appreciated by those skilled in the art that the present invention can implement with other concrete forms not break away from its spirit and substantive features thereof.Therefore, from every aspect, this specification all is considered to illustrative and is nonrestrictive.Scope of the present invention is represented by additional claim rather than above-mentioned specification, and all is scheduled to be included in wherein in the implication and all variations in the scope of its equivalent.

Claims (12)

1. the method for at least three local oscillated signals of a generation is used to receive the signal of communication of the respective sub-bands that takies a frequency band, and this method comprises: synthetic at least the first local oscillator signals that directly produces of frequency of utilization; And by first local oscillator signals and another frequency signal are mixed generation at least the second local oscillator signals.

2. the method for claim 1, wherein this another frequency signal comprises and separates the adjacent sub-band or the deviation frequency of its integer multiple.

3. method as claimed in claim 2, wherein this another frequency signal comprises the deviation frequency of separating adjacent sub-band, further comprises mixing by another frequency signal with the integral multiple of first local oscillator signals and this deviation frequency producing at least the three local oscillator signals.

4. method as claimed in claim 2, wherein this another frequency signal comprises the optional integral multiple of the deviation frequency of separating adjacent sub-bands.

5. method as claimed in claim 2 comprises three local oscillator signals that produce the sub-band that is used for three vicinities, and wherein first local oscillator signals is corresponding to the center sub-band of three sub-frequency bands.

6. the method for claim 1 comprises: synthetic the first and the 3rd local oscillator signals that directly produces of frequency of utilization; And produce second local oscillator signals by mixing from the signal that the first and the 3rd local oscillator obtains.

7. be used to produce the circuit of at least three local oscillator signals, be used to receive the signal of communication of sub-band of the correspondence of band occupancy, comprising: the device that is used for synthetic first local oscillating frequency; And respond the single sideband mixer that first local oscillating frequency and being used to produces another frequency signal of at least the second local oscillator signals.

8. circuit as claimed in claim 7, wherein this another frequency signal comprises and separates the adjacent sub-band or the deviation frequency of its integer multiple.

9. circuit as claimed in claim 8, wherein this another frequency signal comprises the deviation frequency of separating adjacent sub-band, comprises by another frequency signal with the integer multiple of first local oscillator signals and this deviation frequency mixing another single sideband mixer that produces at least the three local oscillator signals.

10. circuit as claimed in claim 8 comprises programmable divider, is used to produce the optional integral multiple of the deviation frequency of separating adjacent sub-bands as another frequency signal.

11. circuit as claimed in claim 8, wherein three local oscillator signals are used for the sub-band of three vicinities, and wherein first local oscillator signals corresponding to the center sub-band of three sub-frequency bands.

12. circuit as claimed in claim 7 comprises the device that is used for synthetic the 3rd local oscillating frequency, wherein single sideband mixer mixes the signal that comes from the first and the 3rd local oscillator signals.

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