For example, when paired with the Children s Memory Scale CMS Cohen, 1997 a measure of learning and memory functioning in children or the WIAT-II a measure of academic achievement, information can be gained on both cognitive ability and academic achievement in young children. Combinations such as these would potentially be of use in educational settings and inform educational interventions. A further potentially useful pairing includes the used of the Adaptive Behavior Assessment System ABAS; Harrison this pairing can result in information on cognitive and adaptive functioning, both of which are required for a proper diagnosis of learning difficulties.
However, it is important to consider and recognise the limitations of using assessments. Some studies show that intelligence tests such as the WPPSI-III, especially for pre-K level, are unreliable and their results vary widely with various factors such as retesting, practice familiarizationtest administrator, time and place. 1 There are claims that some commercially available materials improve results simply by eliminating negative factors through familiarization which in turn puts children at a comfortable frame of mind.
The US standardisation of the WPPSI-III included 1,700 children aged 2 years 6 months 7 years 3 months. Iqoption conta reliability coefficients for the WPPSI-III US composite scales range from. The UK sample for the WPPSI-III was collected between 2002 2003 and contained 805 children in an attempt to accurately represent the most current UK population of children aged 2 years 6 months to 7 years 3 months according to the 2001 UK census data. The UK validation project was conducted at City University under the direction of Professor John Rust.
The WPPSI-III has been formally linked with the WIAT-II. The Psychological Corporation, 2001. The relationship between the WPPSI-III and the WPPSI-R, WISC-III, BSID-II, DAS, WIAT-II and CMS was also explored in order to evaluate the assessment s reliability. A number of special group studies were also carried out during standardisation in order to improve the clinical utility of the tool. These studies included children with intellectual disability, developmental delay, language disorders, motor impairment, ADHD and those classed as gifted.
The WPPSI-III has been translated and adapted for use with different populations including Spanish, French and French CanadianGerman, Italian, Swedish, Korean, Taiwanese Chinese versionJapanese, Canadian, Australian, Dutch, Norwegian and Hebrew. For Verbal Items, the child gives definitions for words that the examiner reads aloud. What is happening to life expectancy in the UK. This content relates to the following topics.
Publication details. Posted 22 October 2019 Comments 14 comments. This long read was last updated on 26 June 2020. For our research on the methods being used to calculate deaths from Covid-19, please see this explainer. 2011 marked a turning point in long-term mortality trends in England, with improvements slowing after decades of steady decline, prompting much debate about the causes.
The emergence of Covid-19 in 2020 will have significant implications for life expectancy. Veena also assesses how Covid-19 could have an impact on life expectancy in 2020. In this piece, Veena Raleigh examines trends in life expectancy at birth up to 2019, gender differences, geographical inequalities, how the UK compares with other countries, and possible causes of the slowing mortality improvements in recent years. Note This article presents findings for England, except where the published data relates to England and Wales.
The life expectancy data published for European Union countries provides data for the UK. How has life expectancy changed over time. Mortality has declined steadily since the 19th century, leading to a long-term rise in life expectancy for both males and females see Figure 1. Males born in 1841 could expect to live to only 40.
2 years and females to 42. 2 years, mainly because of high mortality rates in infancy and childhood. Improvements in nutrition, hygiene, housing, sanitation, control of infectious diseases and other public health measures reduced mortality rates, increasing life expectancy to 55 years for males and 59 years for females by 1920. The 20th century saw further dramatic improvements in life expectancy resulting from public health measures such as childhood immunisations, the introduction of universal health care, medical advances such as in treatment of heart disease and cancer and lifestyle changes, including a decline in smoking.
By 2019 life expectancy in England had increased to 79. 9 years for males and 83. 6 years for females these figures are provisional estimates see Figure 2. The effect on healthy life expectancy. Healthy life expectancy1 has also increased, but not as much as life expectancy, so more years are spent in poor health. Although an English male could expect to live 79. 6 years in 2016 18, his average healthy life expectancy was only 63.
2 of those years 20 per cent in not good health. 4 years ie, he would have spent 16. In 2016 18 an English female could expect to live 83. 2 years, of which 19. 3 years 23 per cent would have been spent in not good health. And although females live an average of 3. 6 years longer than males, much of that time is spent in poor health they experience only 0. 5 more years of good health than men.
Rates of disability-free life expectancy are similar to those for healthy life expectancy. Further data on life expectancy, healthy and disability-free life expectancy, including for local areas, is available from the Office for National Statistics. Healthy life expectancy is an estimate of the number of years lived in very good or good general health, based on how individuals perceive their general health.
Disability-free life expectancy is an estimate of the number of years lived without a long-lasting physical or mental health condition that limits daily activities. What s the difference in life expectancy between males and females. In the late 19th and early 20th centuries the gender gap in life expectancy started to widen, peaking at 6. Women have always lived longer than men, but the gender gap in 1841 two years was relatively small because of the high prevalence in the 19th century of diseases that killed men and women indiscriminately.
3 years by 1971 see Figure 1. Reasons for the widening gender gap included poor working conditions and smoking among men in contrast to improved life chances for women, for example, lower risk of dying in labour and from tuberculosis, which affected women more than men. The gender gap has decreased since the 1970s, with mortality falling faster in males than females because of decreases in smoking and mortality from cardiovascular diseases among men.
The gender gap in 2019 see Figure 2 is still nearly double 3. 7 years what it was in 1841 2 years. Inequalities in life expectancy. People living in more affluent areas live significantly longer than people living in deprived areas. 4 years, almost a decade longer than males in the 10 per cent most deprived areas 73. Females in the least deprived 10 per cent of areas in England could expect to live to 86.
3 years, compared with 78. 6 years for females in the most deprived areas, a difference of almost 8 years. Much of this inequality is caused by higher mortality from heart and respiratory disease, and lung cancer in more deprived areas. The gap in healthy life expectancy at birth is even greater about 19 years for both males and females. Those living in the most deprived areas spend nearly a third of their lives in poor health, compared with only about a sixth for those in the least deprived areas.
Socio-economic inequalities in life expectancy are widening as a result of greater gains in life expectancy in least deprived populations. Between 2013 15 and 2016 18, the difference in life expectancy between the most and least deprived areas in England widened by 0. 4 years among males and 0. 5 years among females. Among females living in the most deprived areas life expectancy fell by 95 days over this period, in contrast to the gain of 80 days among females in the least deprived areas.
While mortality has declined everywhere, there is a persistent north south divide in life expectancy and healthy life expectancy, with people in southern regions on average living longer and with more years in good health than those living further north. For example, in 2016 18, life expectancy for males was lowest in Blackpool and Middlesbrough, and highest in Kensington and Chelsea and Westminster, with a difference of about nine years.
In 2016 18, males in the least deprived 10 per cent of areas in England could expect to live to 83. For females, life expectancy was lowest in Blackpool and Manchester and highest in Camden and Kensington and Chelsea, with a difference of about seven years. The gap in years lived in good health across local authorities in England is even greater, about 18 years for males and females.
About 14 per cent of the population of England is non-white. Life expectancy data is not available by ethnic group because ethnicity is not recorded at death registration. Using alternative methods of analysing ethnic differences, some evidence suggests most Black, Asian and minority ethnic BAME groups have lower mortality than the white population, but that differential has been reversed by the higher mortality among BAME groups from Covid-19.
Some population groups have significantly shorter life expectancy than the general population. For example, homeless males and females live 31 years and 38 years fewer years respectively than males and females on average. The slowdown in mortality improvements after 2011. 2011 marked a turning point in long-term mortality trends, with improvements tailing off after decades of steady decline. People with learning disabilities also have shorter lives than the average, by 23 years among males and 27 years among females.
In the 100 years to 2010 12, life expectancy increased by nearly three years every decade, but between 2011 and 2019 it increased by only 0. 6 years for females, having virtually flat-lined between 2014 18. 8 years for males and 0. However, in 2019 life expectancy increased by 0. 3 years in males and 0. 4 years in females and in January March 2020, before the Covid-19 pandemic took effect, mortality was again at the lower level seen in 2019.
The life expectancy gains in 2019 and the fall in mortality in early 2020 are associated with mild flu seasons and troughs in winter mortality. In England there were 495,000 deaths in 2015, about 31,000 more than the preceding five-year average; deaths associated with flu were estimated at about 28,000. One year deserves special mention 2015, when life expectancy fell across virtually all of Europe. Life expectancy fell by 0. 2 years over the preceding year in both males and females unprecedented for decades.
As in Europe, most excess deaths occurred early in the year and among older people, with deaths from respiratory disease including flu and pneumonia being a key contributor to the largest annual rise in deaths since the 1960s. The slowdown in life expectancy improvements, and the Office for National Statistics announcement that the mortality rate in England in quarter one of 2018 was higher than in any quarter one since 2009, prompted the Department of Health and Social Care to ask Public Health England to undertake a review of mortality trends in England.
The review found that improvements in life expectancy had slowed in most areas of England and among all socio-economic groups, but the slowdown was greater among the most deprived groups and inequalities had widened. Slowing mortality improvements among people aged 50 years and over played a significant role. How does the UK compare with other European countries. In 2018, life expectancy at birth varied by 11. 1 years for males and iqoption conta. 7 iqoption conta for females across the 28 European Union EU countries1 UK was in the EU then.
Generally, western, northern and southern European countries had higher life expectancies than central and eastern European countries. In 2018 the UK ranked 10th among the 28 EU countries for male life expectancy and only 17th and below the EU average for female life expectancy Figures 3 and 4with Denmark being the only western European country to have lower female life expectancy.
For males in the UK, life expectancy was 1. Women outlive men in all EU countries. 7 years less than the highest seen in the EU Italy and Sweden and for females it was 3. 2 years shorter than the highest Spain. As in the UK, improvements in mortality, and therefore life expectancy, have slowed in many European countries in recent years. However, the slowdown has been greater in UK than in most other EU countries.
The periodic spikes in excess deaths in some recent winters, especially among older people, show similar patterns across the UK and several European countries, and, according to official agencies are associated with flu and cold spells. In particular, as in the UK, European agencies reported increased mortality in 2015 that disproportionately affected older people, especially women.
Compared with 2014, in 2015 life expectancy fell in 23 of the 28 EU countries for females and in 16 EU countries for males see Figures 5 and 6. European monitoring agencies report that this widespread fall in life expectancy resulted from excess winter mortality associated with flu. Data on life expectancy that is comparable to European countries is available for UK, not England and Wales or England.
Why have improvements in life expectancy slowed down. The reasons for these trends are unclear and have been hotly debated. Several studies attributed both the 2015 fall in life expectancy and the slowdown in mortality improvements after 2011 to the consequences of austerity-driven constraints on health, social care and other public spending and their impact on services. ref 1 6 These studies were often based on statistical associations, for example, between mortality trends and the slowdown in spending on health and social care, increased waiting times, rising numbers of delayed discharges from hospital and cuts in welfare benefits.
Others acknowledge that austerity could have had negative consequences on the quality of care, resulting in some excess deaths, but they suggest that statistical associations don t prove causality and there could be other explanations for the large numbers of extra deaths. For example, the growing complexity of medical conditions in an ageing population, and the contribution of decelerating improvements in cardiovascular disease CVD mortality and periodic bad flu seasons to the decelerating mortality improvements seen in many high-income countries.
Moreover, some European countries that didn t adopt austerity policies also experienced slowdowns in life expectancy improvements eg, Germany and Swedenwhile life expectancy increased in others that introduced severe austerity measures eg Spain, Ireland, Greece. Public Health England s review identified some of the factors contributing to slowing improvements in life expectancy increasing numbers of older people vulnerable to flu and other winter risks, slowing improvements in mortality from heart disease and stroke, widening inequalities and rising death rates from accidental poisoning among younger adults mainly due to drug misuse.
It noted that the slowdown in mortality improvements is occurring across much of the population, at a time when health and social care services have been facing increasing demand and unprecedented financial pressures. The slowdown in improvements in life expectancy seen in the UK has also been seen also in many European countries, but it has been greatest in the UK. It s likely that there are several reasons for the current trends, some specific to the UK such as widening inequalities and some common to the UK and other European countries such as the swings in flu-related mortality and slowdown in CVD mortality improvements in some countries.
What impact will Covid-19 have on life expectancy. After a mild 2020 winter and flu season with low mortality, the first deaths from Covid-19 occurred in early March 2020 and the numbers increased sharply thereafter. Between week ending 13 March 2020 and 12 June 2020, there were 48,218 deaths in England and Wales attributed to Covid-19, and 59,138 excess deaths overall ie, the difference between the number of deaths in 2020 compared with the average for the same period in the previous five years.
Covid-19 thus accounted for 82 per cent of overall excess deaths during this period; the remaining 10,920 deaths resulted from a combination of undiagnosed Covid-19 deaths and non-Covid deaths resulting from other causes because of, eg, reduced uptake of health care for potentially life-threatening conditions, causing an increase in deaths from other causes. To give an idea of scale Covid-19 is now the third leading cause of death, causing more deaths in about three months than the numbers who die in a year from heart disease or lung cancer or stroke.
Predicting the impact of Covid-19 on life expectancy is difficult for several reasons including, for example, the following. The large numbers of deaths that Covid-19 has caused, or hastened, among people with pre-existing conditions and frail older people may be counter-balanced by fewer deaths in future. However, this will not become clear for a while and is not a certainty For example, men and women in England aged 75 can expect to live another 12 years and 13 years respectively, and at age 85 it s 6 years and 7 years iqoption conta.
So, deaths even at older ages can shorten lives by several years. Some excess deaths could be offset by fewer deaths from, eg, air pollution and transport accidents. Finally, the pandemic isn t over and much depends on its impact directly and indirectly on deaths from other causes on mortality in the months ahead. The scale of excess mortality associated with Covid-19 thus far, and evidence that many lives have been cut short eg, almost 11 per cent of Covid-19 deaths were among people aged under 65 yearsis unprecedented in recent decades.
The wider socio-economic impacts of the pandemic could also have an adverse impact on health and mortality overall, particularly among more deprived and minority ethnic groups who already experience disproportionately higher mortality from Covid-19. The overall impact that this pandemic is likely to have on life expectancy in 2020 will become clearer in due course. As iqoption conta number of deaths associated with Covid-19 in the UK is among the highest in Europe and as the UK already trails many European countries in terms of life expectancy, we could see UK slide further down life expectancy league tables.
Some of the direct and indirect effects of the Covid-19 pandemic on population health and mortality in the UK could last beyond 2020. Subscribe to our email newsletter and follow TheKingsFund on Twitter to see new content as it s published, along with our other news. Hiam L, Dorling D, Harrison D, McKee M 2017. What caused the spike in mortality in England and Wales in January 2015. Journal of the Royal Society of Medicine, vol 110, no 4, pp 131 7, doi 10.
journalCode jrsb accessed on 23 June 2020. Why has mortality in England and Wales been increasing. An iterative demographic analysis. Journal of the Royal Society of Medicine, vol 110, no 4, pp 153 62. 1177 0141076817693599 accessed on 23 June 2020. Loopstra R, McKee M, Katikireddi SV, Taylor-Robinson D, Barr B, Stuckler D 2016.
Austerity and old-age mortality in England a longitudinal cross-local area analysis, 2007 2013. Journal of the Royal Society of Medicine, vol 109, pp 109 16. 1177 0141076816632215 accessed on 23 June 20200. Hiam L, Harrison D, McKee M, Dorling D 2018. Why is life expectancy in England and Wales stalling. Journal of Epidemiology and Community Health, vol 72, pp 404 8. com content early 2018 02 20 jech-2017-210401 accessed on 23 June 2020. Green MA, Dorling D, Minton J, Pickett KE 2017.
Journal of Epidemiology and Community Health, vol 71, pp 1068 971. com content jech 71 11 1068 accessed on 23 June 2020. Watkins J, Wulaningsih W, Da Zhou C, Marshall D, Sylianteng G, Dela Rosa P, Miguel V, Raine R, King L, Maruthappu M 2017. Could the rise in mortality rates since 2015 be explained by changes in the number of delayed discharges of NHS patients. com content 7 11 e017722 accessed on 23 June 2020.
Fordham R, Roland M 2017. Expert reaction to paper on health and social care spending and excess deaths in England. Social Media Centre website. org expert-reaction-to-paper-on-health-and-social-care-spending-and-excess-deaths-in-england accessed on 23 June 2020. Steventon A 2017. Effects of health and social care spending constraints on mortality in England a time trend analysis.
Can you really link delayed discharge to mortality. The evidence is far from clear. Blog, The Health Foundation website. uk blog can-you-really-link-delayed-discharge-mortality-evidence-far-clear Milne E 2017. Why the 120,000 deaths claim is unsupportable. com 2017 11 17 why-the-120000-deaths-claim-is-unsupportable accessed on 23 June 2020. Raleigh VS 2018. Stalling life expectancy in the UK.
BMJ 2018; 362. uk publications stalling-life-expectancy-uk accessed on 23 June 2020. Raleigh V 2019Trends in life expectancy in EU and other OECD countries Why are improvements slowing. OECD Health Working Papers, 108. 1787 223159ab-en accessed on 23 June 2020. EUROMOMO 2020. Euromomo website. eu accessed on 23 June 2020. OECD, The King s Fund 2020.
Is cardiovascular disease slowing improvements in life expectancy. OECD and The King s Fund Workshop Proceedings. Paris OECD Publishing. 1787 47a04a11-en accessed on 23 June 2020. Mortality rates in the UK why are improvements in life expectancy slowing down. Deaths from Covid-19 coronavirus how are they counted and what do they show. Is the problem of excessive winter deaths unique to the UK. Why have improvements in mortality slowed down. pamela ellis.
I have been shown extreme contempt and have been lied to by York Trust, Scarborough Hospital, PHSO, North Yorkshire Police and the Coroner. All of these are in a conspiracy re my mother s death March 2012. The mortality review not done correctly. I have spent since then investigating my mother s death. I have asked questions about the lies I have been told, about the information I have found out.
November 2012 the Admitted Neglect from the Outset after my investigation report. I have never been told why. The neglect was premeditated abject cruelty for which they could not care less. Delay tactics and lies by all of the above. My mother s life to them not worthy of a dog s. I have pleaded with all of them for the truth and dismissed by all. The Coroner could not care this is post mortem report reads nothing like the truth. CQC couldn t care less.
2012 was the worst year of mortality results. Mum only went into hospital for observation A E changed SECRETLY mum s admission reason and she was denied medical care, lost her teeth, I now believe deliberately so she couldn t eat properly. Friday 23rd March 2012 10am Eileen desperate to go home I WAS NOT TOLD YET 3PM had mums clothes with me but a refusal to take her home. Mum was kept a prisoner to drive her to desperation to death.
I am now 76 and they have taken my life by refusal to give me the truth of mum s last hours from when I left her looking very well and so pleased to see me. I feel guilty mum was being neglect under my eyes. THEY WILL NOT TELL ME THE TRUTH. INTERNAL Iqoption conta INTO NORTH YORKSHIRE POLICE LIES TO ME AND THE CORONER CONDONED. WHAT SORT OF LIFE ARE THE ELDERLY LIVING IN.
I BELIEVE THERE IS A SYSTEMATIC CULLING OF OUR BELOVED ELDERLY AND THE CRUELTY IS GETTING WORSE. Your report does not relay anything like what family have to endure to their loved ones. Reply Link to comment. I want my comments to you made public. I will spend to my dying day to get justice for my mother by way of truth told to my family and myself. I will be sending a report to Theresa May in the hope she is not just one of the number I have contacted to help me and hope she does not show contempt to me as all the rest of them have done.
Now aged 76 as I have already commented on and I believe on the nhs OLD PEOPLES list also for limited medical treatment. Or was the age 70 re the neglect of callup for breast scan, so this disease would go unnoticed and kill many more people. Varicose veins no-one cares and told wait until you get an ulcer then you can have treatment, this is against Consultants advice.
In Reading,Berkshire our fantastic second hospital in grounds, hydrotherapy pool, heart, stroke etc. hospital, was sold and now we have a very large Tescos, a village of flats and a mosque. How could this happen when we had two hospitals for years and years, with less people,and now the Royal Berkshire Hospital, old and little, we have, which cannot cope.
Certain operations at Thatcham and elsewhere. I have not car, so no operation. People living in Bridlington, where mum lived, have to go to Scarborough Hospital, people limited money have to pay to get to Scarborough. Many situations people have to get to York under their own steam, which is a nightmare of short visit to their loved ones to get back to Bridlington.
Bridlington has a decent building hospital, most of it closed down. I have a four week delay to see my own very lovely, unusually very caring doctor, but now trying to get a Doppler test, phoned twice but dates only set for the week whenever, despite my urgency. If mum had not had me to look after her, even when she could contact a doctor, the system was so complicated even many years ago made life for her impossible. Everything needs to be sorted in the nhs.
No-one at the helm, I am heartbroken at what happened to my mother, NO-ONE CARED, NO-ONE IN CHARGE, NO-ONE TO TELL ME THE TRUTH AND THE CORONER COULD NOT CARE LESS THE POST MORTEM REPORT GIVES THE TRUTH. Even Sir Robert Francis I contacted cannot help and I feel does not want to know the truth what is happening. I never get any comments from you or what you do with my information.
Or am I correct to say CULLING OF OUR ELDERLY IS SYSTEMATIC IN EVERY COUNTY. Mum was 92 with shortterm memory. We had a good life, I kept mum smart as she always was and wanted to be. Everyday was active which she loved. Everyday was looked forward to by her. Despite the fact she lost the reason to look after herself, and remember what happened a few minutes before or where we had been for the day, mum remained sociable, loved going out, yet did not have a clue re the date, month etc.
I believe the changing of mums tablets she had been on for years Atenolol to Amlodipine together with Simvastin was not good and twice the doctors and hosp asked for compatibility but both times ignored, I later found out could have had something to do with mum s harsh cough and intermittent heart pains she only went into hospital for observation for.
I could read certain interesting info from newspapers and leave it by her and she could ask me many times, what is this about, could not remember to take her tablets etc. I have a list of lies told to my by the hospital, phso, police and refusal by Coroner. The CEO of York Trust is a disgrace as he tried to bully me by telling me the case was closed when he fully knew the truth about mum s death had not been revealed. I am not a strong person, but they will never use their miserable cruel tactics of bullying and lying to break me, no matter how I am suffering, the sleepless nights, no life, the cost to the nhs they are causing by their disgusting disgraceful behaviour.
I m very sorry to hear about your experiences and your concerns about the care your mother received. The King s Fund are not able to comment on individual cases, however as we ve previously advised there are a number of organisations that may be able to offer you help and support regarding this. The Patients Association, who are independent charity that provides specialist information and advice. They can be contacted via their helpline 020 8423 8999 or by email at helpline patients-association.
I hope the above information is useful to you. Kind regards, Sarah. Life Expectancy mean average is not the appropriate measure to compare years lived in 1840 and now. In 1840, LE was disproportionately skewed by high death rates among children. The average age of adult deaths has only increased by approximately 15yrs, not 40yrs, since 1840. Much smaller gains for adults than we give ourselves credit for. LE and modal average have become aligned since 1970s as perinatal child mortality rates have more or less plateaued.
Isn t it therefore more appropriate to be using modal average to compare historical trends. Although causality is difficult to establish, the 120,000 extra deaths in UK 2010-15 BMJ - not due to ageing population, flu, or cold weather - occurred mainly in 65 s and care home residents. To my mind, this says something very clearly about changes in social care and NHS since 2010. Neil Bendel. I d be interested to know if this work is going to look at local variations in the slow down of life expectancy.
Is life expectancy slowing down in some areas more than others and, if so, why. Is the growth in life expectancy growth slower in more deprived areas or in particular types of area e. urban rural areas, coastal communities etc. This would help to identify if there are specific local factors in play as well as national drivers and which have had the biggest impact. Our project will look at life expectancy in local areas but not until phase 2 which takes us to Spring 2019.
In the meantime, you may be interested to see some ONS reports on this, if you haven t seen them already. If you have any further questions, please do not hesitate to get in touch. Judy Abrahams. I am 70 years old and have just spent a year of my life waiting on pain with greatly reduced mobility for a hip replacement. The NHS is under funded. Teresa May and her friends can easily afford private health care.
What can we expect. Along with the Patient Advice and Liaison Service at your local hospital and your local Healthwatch who we understand you have already been in touch with, there is. This white paper describes the theoretical background of I Q data as well as practical considerations which make the use of I Q data in communication so desirable. Each page in this series teaches you a specific concept related to common measurement applications by explaining the theory and giving practical examples.
What is I Q Data. Put simply, I Q data shows the changes in magnitude or amplitude and phase of a sine wave. If amplitude and phase changes occur in an orderly, predetermined fashion, you can use these amplitude and phase changes to encode information upon a sine wave, a process known as modulation. Modulation changes a higher frequency carrier signal in proportion to a lower frequency message, or information, signal.
I Q data is highly prevalent in RF communications systems, and more generally in signal modulation, because it is a convenient way to modulate signals. Background on Signals I Q Data in Communication Systems So Why Use I Q Data. Related NI Products Conclusions. Background on Signals. Signal modulation changes a sine wave to encode information. The equation representing a sine wave is as follows.
This white paper is part of the NI Measurement Fundamentals main page series. Figure 1 Equation for a Sine Wave. The equation above shows that you are limited to making changes to the amplitude, frequency, and phase of a sine wave to encode information. Frequency is simply the rate of change of the phase of a sine wave frequency is the first derivative of phaseso frequency and phase of the sine wave equation can be collectively referred to as the phase angle.
Therefore, we can represent the instantaneous state of a sine wave with a vector in the complex plane using amplitude magnitude and phase coordinates in a polar coordinate system. Polar Representation of a Sine Wave. In the graphic above, the distance from the origin to the black point represents the amplitude magnitude of the sine wave, and the angle from the horizontal axis to the line represents the phase.
Thus, the distance from the origin to the point remains the same as long as the amplitude of the sine wave is not changing modulating. The phase of the point changes according to the current state of the sine wave. For example, a sine wave with a frequency of 1 Hz 2π radians second rotates counter-clockwise around the origin at a rate of one revolution per second. If the amplitude doesn t change during one revolution, the dot maps out a circle around the origin with radius equal to the amplitude along which the point travels at a rate of one cycle per second.
Because phase is a relative measurement, imagine that the phase reference used is a sine wave of frequency equal to the sine wave represented by the amplitude and phase points. If the reference sine wave frequency and the plotted sine wave frequency are the same, the rate of change of the two signals phase is the same, and the rotation of the sine wave around the origin becomes stationary.
In this case, a single amplitude phase point can represent a sine wave of frequency equal to the reference frequency. Any phase rotation around the origin indicates a frequency difference between the reference sine wave and the sine wave being plotted. Up to this point, this white paper has described amplitude and phase data in a polar coordinate system. All the concepts discussed above apply to I Q data.
In fact, I Q data is merely a translation of amplitude and phase data from a polar coordinate system to a Cartesian X,Y coordinate system. Using trigonometry, you can convert the polar coordinate sine wave information into Cartesian I Q sine wave data. These two representations are equivalent and contain the same information, just in different forms. I and Q Represented in Polar Form. The figure below shows a LabVIEW example demonstrating the relationship between polar and Cartesian coordinates.
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