WO2006012245A1 - Receiver for use in wireless communications and method and terminal using it - Google Patents
Receiver for use in wireless communications and method and terminal using it Download PDFInfo
- Publication number
- WO2006012245A1 WO2006012245A1 PCT/US2005/022335 US2005022335W WO2006012245A1 WO 2006012245 A1 WO2006012245 A1 WO 2006012245A1 US 2005022335 W US2005022335 W US 2005022335W WO 2006012245 A1 WO2006012245 A1 WO 2006012245A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- block
- values
- imbalance
- phase
- estimator
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
- H03D3/007—Demodulation of angle-, frequency- or phase- modulated oscillations by converting the oscillations into two quadrature related signals
- H03D3/009—Compensating quadrature phase or amplitude imbalances
Definitions
- This invention relates to a receiver for use in wireless communications and a method and terminal using it.
- the invention relates to a direct conversion receiver capable of demodulating a frequency modulated (FM) RF (radio frequency) signal by resolution and use of in-phase (I) and quadrature (Q) components of the modulated signal.
- FM frequency modulated
- I in-phase
- Q quadrature
- US5705949 proposes a procedure for removing amplitude or gain error between I and Q components.
- the procedure requires complex processing capacity and is unlikely to be satisfactory in a fading environment.
- FIG. 1 is a schematic block circuit diagram of a known direct conversion RF receiver.
- FIG. 2 is a schematic block circuit diagram of a direct conversion RF receiver embodying the invention Description of embodiments of the invention
- FIG. 1 shows a known RF direct conversion FM receiver 100 illustrating the problem to be addressed by the present invention.
- An incoming FM signal x(t) is delivered via an input path 101 having branched connections 103, 105 respectively to two mixers 107, 109.
- a local oscillator 111 generates a reference signal having the same frequency as the carrier frequency of the incoming signal x(t).
- a first component of the reference signal is applied directly to the mixer 107 where it is multiplied with the input signal x(t) .
- a second component of the reference signal is applied to a phase shifter 113 and a phase shifted output of the phase shifter 113 is applied to the mixer 109 where it is multiplied with the input signal x(t).
- phase shifter 113 in combination with the mixers 107 and 109 is intended to introduce a phase shift of 90 degrees with unity gain between the components of the reference signal applied to the mixers 107 and 109, in practice a phase shift slightly different from 90 degrees and a gain slightly different from unity are introduced.
- An output signal from the mixer 107 is passed through a low pass filter (LPF) 115 to produce an output in-phase component signal I(t) and an output signal from the mixer 109 is passed through a low pass filter (LPF) 117 to produce an output quadrature component signal Q(t).
- LPF low pass filter
- LPF low pass filter
- Q(t) low pass filter
- the imbalance in amplitude introduced into the output of the mixer 109 is shown in block 119 as an imbalance gain A.
- a mathematical analysis of the arrangement shown in FIG. 1 is as follows:
- the input signal may be represented as :
- ⁇ is RF carrier frequency of the input RF signal x(t), /is oscillator arbitrary phase and ⁇ (t) is the frequency modulation of x(t) to be detected.
- x(t) I(t)+j*Q(t), whereI(t) and Q(t) are in-phase and quadrature components ofx(t).
- A represents the amplitude imbalance and arepresents the phase imbalance angle between the phase angles of I(t) and Q(t).
- the components I(t) and Q(t) are processed in a manner to be described to estimate and apply an adjustment to eliminate the amplitude imbalance A.
- the phase imbalance is also estimated and eliminated, e.g. as described in Applicant's copending UK patent application number 0411888.1
- the resulting adjusted components are combined to construct the modulation signal ⁇ (t) to provide an audio signal output.
- FIG. 2 is a block schematic diagram of a circuit 200 embodying the invention for use in a direct conversion FM receiver.
- Components having the same reference numerals as components in FIG. 1 have the same function as such components and will not be further described.
- the output signal Iff) passed by the low pass filter (LPF) 115 is sampled by a connection 201 and the output signal Q(t) passed by the low pass filter (LPF) 117 is sampled by a connection 203.
- the respective sampled signals obtained by the connections 201 and 203 are provided as respective inputs to a processor 204 which operates an amplitude imbalance algorithm to be described in detail later.
- An output signal from the processor 204 is an amplitude imbalance correction signal indicating a value of I/A. This correction signal is applied via a connection 202 to an amplitude modifier 205 which modifies the amplitude of Q(t) by a factor of I/A to eliminate the detected amplitude imbalance A.
- a phase adjustment processing circuit (not shown) using samples of I(t) and Q(t) estimates a phase imbalance between I(t) and Q(t), e.g. in the manner described in Applicant's copending UK patent application number 0411888.1, and generates a phase shift control signal corresponding to an equal and opposite value of this estimated phase imbalance.
- the phase adjustment signal estimated in this way is applied by a phase shifter 207.
- a signal corresponding to the quadrature component Q(t) is applied from the low pass filter 117 via a connection 226 to the phase shifter 207.
- the phase shifter 207 thereby applies a phase angle adjustment which compensates for the detected phase imbalance angle CC.
- An output from the phase shifter 207 corresponding to a phase adjusted value of Q(t) is applied to a processor 209.
- a signal corresponding to the in-phase component I(t) is also applied as an input to the processor 209 via a connection 224.
- the processor 209 calculates a value of the quotient Q(t)/I(t) from its respective inputs and supplies a signal representing the result to a processor 211.
- the processor 211 calculates the value of the arctangent (arctg) of the quotient parameter represented by the input signal from the processor 209.
- An output signal from the processor 211 is applied to a further processor 213 which calculates the differential with respect to time t of the input signal to the processor 213.
- an output signal from the processor 213 is applied to an audio output 215.
- the audio output 215 includes a transducer (not shown specifically) such as an audio speaker which converts an electronic signal output from the processor 213 into an audio signal, e.g. speech information.
- 10000/100 100 blocks.
- the algorithm performs . better in a fading environment with a small block size .
- an amplitude imbalance value is calculated from the power of I and the power of Q
- the block value of A n is the square root value of the power of Q divided by the power of
- the values of amplitude imbalance found for each of the blocks in a given set of blocks, say 1000 blocks, are sorted in order from lowest to highest.
- a sub-set of 45% of the highest block amplitude imbalance values in the sorted set and a sub-set of 45% of the lowest block amplitude imbalance values in the sorted set are rejected leaving only a sub-set of the 10% block amplitude imbalance values between the rejected sub-sets. So for example where there are 1000 blocks in the set, the 450 highest and the 450 lowest block amplitude imbalance values results are rejected leaving 100 block amplitude imbalance values which are further processed.
- a 00n is the amplitude imbalance to be corrected for .
- a corr is equal to the kth root of the product of the k sample results for A multiplied by each other .
- a signal corresponding to 1/A ⁇ n is issued by the processor 204 to be applied by the amplitude modifier 205.
- the algorithm is performed continuously and adaptively on the received FM modulated signal during periods when a signal is received.
- the processor 204 may be operated when any received speech signal plus associated sub-audio signalling is received by the receiver 200. However, if desired, the algorithm may be operated selectively only when a specific input signal is received by the receiver 200.
- the receiver may operate on a known analogue FM signal received from a RF transmitter. This may for example be a standard FM modulated signal in accordance with the industry standard TIA 603.
- Division into blocks of the samples processed by the processor 204 in the manner described earlier is beneficial for processing a signal received in a fading environment. If division into blocks is not applied there is no possibility to reject results that are not correct due to fading. In a fading environment there are fast variations in signal envelope. When a signal is in a deep fade the result for the quotient Q/I (for the block processed when this applies) can be very large (I is close to zero) or very small (Q is close to zero) . Division into blocks, sorting and rejecting high and low results allows incorrect results caused by fading not to be included in the amplitude imbalance estimation. In practice, a wireless terminal is always likely to work in fading environment. Block size is also significant: for fast fading a small block size is optimal, for low S/N a larger block size would be optimal.
- the receiver 200 may constantly measure the received signal power using a known RSSI (Received
- the result may be provided to the estimator 204 which may be operable to adjust the block size automatically using the result provided. It may be assumed that there is a relationship between received signal power and received S/N so that for high received power the S/N is also high.
- a threshold received power value is used to determine whether a small block size is to be used when the received power value is equal to or above the threshold or.a greater block size is to be used when the received power value is below the threshold.
- Finding the geometric average has been found to be better than finding the arithmetic average, because the latter was found to introduce a bias to the results and gave an incorrect amplitude imbalance estimation.
- processors are shown in FIG. 2. These processors may be separate processors as shown or the functions of -two or more of the processors may be combined into a single processor, e.g. digital signal processor programmed with computational software, as will be apparent to those skilled in the art.
- the error in Amp IM was measured and the results ranged from 0.08% to a maximum of 0.45% with an average error of 0.2%.
- the error in Amp IM was estimated for various simulated signals with a signal to noise ratio (SNR) ranging from 15dB to 35dB and the error ranged from 0.08% (35dB SNR) to 0.2% (15dB SNR) .
- SNR signal to noise ratio
- a memory of the radio may be programmed following manufacture to store a table of initial imbalance values versus RF frequency. During operation of the radio the imbalance values (amplitude and phase) will change with time. Thus, updated imbalance information may be gathered in use as described in the above embodiments and used to provide suitable compensation to maintain a suitable quality of audio output signal . The updated imbalance information may also be stored in the memory of the radio to replace the originally stored information.
- an improved method for adaptive amplitude imbalance compensation in a direct conversion receiver has been provided together with a receiver operating using the method.
- the method is gives a substantial improvement to estimating the required imbalance compensation in conditions where the received signal is subject to noise and/or fading.
- a look up table of initial amplitude imbalance values vs. RF frequencies may be programmed in a memory associated with the receiver, e.g. in a memory of a mobile station in which the receiver is used. This may be for example the so called codeplug which stores the operating programs and data of the mobile station.
- the amplitude imbalance as a function of frequency will change gradually with time.
- Information gathered by the processor 204 may be used to update the stored information in the memory.
- the invention gives improved audio performance in a wireless terminal having a receiver operating on an FM analogue signal in a direct conversion mode.
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2007519294A JP2008509577A (en) | 2004-06-29 | 2005-06-23 | Receiver for use in wireless communication, and method and terminal using the receiver |
CA2572236A CA2572236C (en) | 2004-06-29 | 2005-06-23 | Receiver for use in wireless communications and method and terminal using it |
DE112005001456T DE112005001456T5 (en) | 2004-06-29 | 2005-06-23 | Receivers for use in wireless messaging and method and terminal using the same |
AU2005267308A AU2005267308B2 (en) | 2004-06-29 | 2005-06-23 | Receiver for use in wireless communications and method and terminal using it |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0414459.8 | 2004-06-29 | ||
GB0414459A GB2415846B (en) | 2004-06-29 | 2004-06-29 | Receiver for use in wireless communications and method and terminal using it |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2006012245A1 true WO2006012245A1 (en) | 2006-02-02 |
Family
ID=32800330
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2005/022335 WO2006012245A1 (en) | 2004-06-29 | 2005-06-23 | Receiver for use in wireless communications and method and terminal using it |
Country Status (7)
Country | Link |
---|---|
JP (1) | JP2008509577A (en) |
CN (1) | CN100588123C (en) |
AU (1) | AU2005267308B2 (en) |
CA (1) | CA2572236C (en) |
DE (1) | DE112005001456T5 (en) |
GB (1) | GB2415846B (en) |
WO (1) | WO2006012245A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2437574B (en) | 2006-04-28 | 2008-06-25 | Motorola Inc | Receiver for use in wireless communications and method of operation of the receiver |
US8503545B2 (en) | 2006-08-31 | 2013-08-06 | Advanced Micro Devices, Inc. | I/Q imbalance compensation |
JP4850222B2 (en) * | 2008-08-26 | 2012-01-11 | 株式会社豊田中央研究所 | Correction method of offset amount in phased array radar |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4696017A (en) * | 1986-02-03 | 1987-09-22 | E-Systems, Inc. | Quadrature signal generator having digitally-controlled phase and amplitude correction |
US5901346A (en) * | 1996-12-11 | 1999-05-04 | Motorola, Inc. | Method and apparatus utilizing a compensated multiple output signal source |
US6122325A (en) * | 1998-02-04 | 2000-09-19 | Lsi Logic Corporation | Method and system for detecting and correcting in-phase/quadrature imbalance in digital communication receivers |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040013204A1 (en) * | 2002-07-16 | 2004-01-22 | Nati Dinur | Method and apparatus to compensate imbalance of demodulator |
-
2004
- 2004-06-29 GB GB0414459A patent/GB2415846B/en not_active Expired - Fee Related
-
2005
- 2005-06-23 JP JP2007519294A patent/JP2008509577A/en active Pending
- 2005-06-23 CN CN200580021656A patent/CN100588123C/en not_active Expired - Fee Related
- 2005-06-23 AU AU2005267308A patent/AU2005267308B2/en not_active Ceased
- 2005-06-23 WO PCT/US2005/022335 patent/WO2006012245A1/en active Application Filing
- 2005-06-23 CA CA2572236A patent/CA2572236C/en not_active Expired - Fee Related
- 2005-06-23 DE DE112005001456T patent/DE112005001456T5/en not_active Ceased
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4696017A (en) * | 1986-02-03 | 1987-09-22 | E-Systems, Inc. | Quadrature signal generator having digitally-controlled phase and amplitude correction |
US5901346A (en) * | 1996-12-11 | 1999-05-04 | Motorola, Inc. | Method and apparatus utilizing a compensated multiple output signal source |
US6122325A (en) * | 1998-02-04 | 2000-09-19 | Lsi Logic Corporation | Method and system for detecting and correcting in-phase/quadrature imbalance in digital communication receivers |
Also Published As
Publication number | Publication date |
---|---|
CN100588123C (en) | 2010-02-03 |
CA2572236A1 (en) | 2006-02-02 |
GB2415846A (en) | 2006-01-04 |
JP2008509577A (en) | 2008-03-27 |
GB0414459D0 (en) | 2004-07-28 |
CN1981437A (en) | 2007-06-13 |
GB2415846B (en) | 2006-08-02 |
DE112005001456T5 (en) | 2007-05-31 |
AU2005267308A1 (en) | 2006-02-02 |
CA2572236C (en) | 2010-10-19 |
AU2005267308B2 (en) | 2008-04-10 |
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