ameblo.over-update.download

Definition: A digital modulation technique in which the amplitude of the carrier wave is altered according to the modulating signal (bitstream) is known as Amplitude Shift Keying (ASK). It is the easiest and straightforward digital modulation scheme. The term PSK or Phase shift keying is broadly used in a radio communication system.This kind of technique is mostly compatible with data communications. It allows information in a more efficient way to be carried over a radio communications signal. Jul 12, 2018 So now you can understand what is 'binary' in binary phase shift keying. As the phase of the carrier wave is modulated by the binary symbols '1' and '0' in binary phase shift keying. So here we see only two phases 0 degrees and 180 degrees. That's why it is known as binary phase shift keying (BPSK). In amplitude shift keying theory, input binary signal amplitude varies according to the carrier signal voltage. Those intervals the switch is closed and it is multiplied with the carrier signal which is generating from the function generator for the same duration. Amplitude shift keying is an.

1. Phase Shift Keying
2. Binary Phase Shift Keying Generation And Detection Test
3. Phase Shift Keying Pdf
4. Binary Phase Shift Keying Generation And Detection System
5. Binary Phase Shift Keying Bpsk
6. Binary Frequency Shift Keying
7. Binary Phase Shift Keying Generation And Detection Software

• Digital Communication Tutorial

• Digital Communication Resources

• Selected Reading

Amplitude Shift Keying (ASK) is a type of Amplitude Modulation which represents the binary data in the form of variations in the amplitude of a signal.

Any modulated signal has a high frequency carrier. The binary signal when ASK modulated, gives a zero value for Low input while it gives the carrier output for High input.

The following figure represents ASK modulated waveform along with its input.

To find the process of obtaining this ASK modulated wave, let us learn about the working of the ASK modulator.

ASK Modulator

The ASK modulator block diagram comprises of the carrier signal generator, the binary sequence from the message signal and the band-limited filter. Following is the block diagram of the ASK Modulator.

The carrier generator, sends a continuous high-frequency carrier. The binary sequence from the message signal makes the unipolar input to be either High or Low. The high signal closes the switch, allowing a carrier wave. Hence, the output will be the carrier signal at high input. When there is low input, the switch opens, allowing no voltage to appear. Hence, the output will be low.

The band-limiting filter, shapes the pulse depending upon the amplitude and phase characteristics of the band-limiting filter or the pulse-shaping filter.

ASK Demodulator

There are two types of ASK Demodulation techniques. They are −

• Asynchronous ASK Demodulation/detection
• Synchronous ASK Demodulation/detection

The clock frequency at the transmitter when matches with the clock frequency at the receiver, it is known as a Synchronous method, as the frequency gets synchronized. Otherwise, it is known as Asynchronous.

Asynchronous ASK Demodulator

The Asynchronous ASK detector consists of a half-wave rectifier, a low pass filter, and a comparator. Following is the block diagram for the same.

The modulated ASK signal is given to the half-wave rectifier, which delivers a positive half output. The low pass filter suppresses the higher frequencies and gives an envelope detected output from which the comparator delivers a digital output.

Synchronous ASK Demodulator

Synchronous ASK detector consists of a Square law detector, low pass filter, a comparator, and a voltage limiter. Following is the block diagram for the same.

The ASK modulated input signal is given to the Square law detector. A square law detector is one whose output voltage is proportional to the square of the amplitude modulated input voltage. The low pass filter minimizes the higher frequencies. The comparator and the voltage limiter help to get a clean digital output.

Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier signal.^[1] The technology is used for communication systems such as telemetry, weather balloon radiosondes, caller ID, garage door openers, and low frequency radio transmission in the VLF and ELF bands. The simplest FSK is binary FSK (BFSK). BFSK uses a pair of discrete frequencies to transmit binary (0s and 1s) information.^[2] With this scheme, the '1' is called the mark frequency and the '0' is called the space frequency.

Phase Shift Keying

Modulating and demodulating[edit]

Reference implementations of FSK modems exist and are documented in detail.^[3] The demodulation of a binary FSK signal can be done using the Goertzel algorithm very efficiently, even on low-power microcontrollers.^[4]

Other forms of FSK[edit]

Binary Phase Shift Keying Generation And Detection Test

Continuous-phase frequency-shift keying[edit]

In principle FSK can be implemented by using completely independent free-running oscillators, and switching between them at the beginning of each symbol period.In general, independent oscillators will not be at the same phase and therefore the same amplitude at the switch-over instant,causing sudden discontinuities in the transmitted signal.

In practice, many FSK transmitters use only a single oscillator, and the process of switching to a different frequency at the beginning of each symbol period preserves the phase.The elimination of discontinuities in the phase (and therefore elimination of sudden changes in amplitude) reduces sideband power, reducing interference with neighboring channels.

Gaussian frequency-shift keying[edit]

Rather than directly modulating the frequency with the digital data symbols, 'instantaneously' changing the frequency at the beginning of each symbol period, Gaussian frequency-shift keying (GFSK) filters the data pulses with a Gaussian filter to make the transitions smoother. This filter has the advantage of reducing sideband power, reducing interference with neighboring channels, at the cost of increasing intersymbol interference. It is used by Improved Layer 2 Protocol, DECT, Bluetooth,^[5]Cypress WirelessUSB, Nordic Semiconductor,^[6]Texas InstrumentsLPRF, IEEE 802.15.4, Z-Wave and Wavenis devices. For basic data rate Bluetooth the minimum deviation is 115 kHz.

A GFSK modulator differs from a simple frequency-shift keying modulator in that before the baseband waveform (levels −1 and +1) goes into the FSK modulator, it is passed through a Gaussian filter to make the transitions smoother so to limit its spectral width. Gaussian filtering is a standard way for reducing spectral width; it is called 'pulse shaping' in this application.

In ordinary non-filtered FSK, at a jump from −1 to +1 or +1 to −1, the modulated waveform changes rapidly, which introduces large out-of-band spectrum. If the pulse is changed going from −1 to +1 as −1, −0.98, −0.93, .., +0.93, +0.98, +1, and this smoother pulse is used to determine the carrier frequency, the out-of-band spectrum will be reduced.^[7]

Minimum-shift keying[edit]

Minimum frequency-shift keying or minimum-shift keying (MSK) is a particular spectrally efficient form of coherent FSK. In MSK, the difference between the higher and lower frequency is identical to half the bit rate. Consequently, the waveforms that represent a 0 and a 1 bit differ by exactly half a carrier period. The maximum frequency deviation is δ = 0.25 f_m, where f_m is the maximum modulating frequency. As a result, the modulation index m is 0.5. This is the smallest FSK modulation index that can be chosen such that the waveforms for 0 and 1 are orthogonal.

Phase Shift Keying Pdf

Gaussian minimum-shift keying[edit]

A variant of MSK called Gaussian minimum-shift keying (GMSK) is used in the GSMmobile phone standard.

Audio FSK[edit]

Audio frequency-shift keying (AFSK) is a modulation technique by which digitaldata is represented by changes in the frequency (pitch) of an audio tone, yielding an encoded signal suitable for transmission via radio or telephone. Normally, the transmitted audio alternates between two tones: one, the 'mark', represents a binary one; the other, the 'space', represents a binary zero.

AFSK differs from regular frequency-shift keying in performing the modulation at baseband frequencies. In radio applications, the AFSK-modulated signal normally is being used to modulate an RFcarrier (using a conventional technique, such as AM or FM) for transmission.

Binary Phase Shift Keying Generation And Detection System

Kindle fire 5th generation value. AFSK is not always used for high-speed data communications, since it is far less efficient in both power and bandwidth than most other modulation modes.^{[citation needed]} In addition to its simplicity, however, AFSK has the advantage that encoded signals will pass through AC-coupled links, including most equipment originally designed to carry music or speech.

AFSK is used in the U.S.-based Emergency Alert System to notify stations of the type of emergency, locations affected, and the time of issue without actually hearing the text of the alert.

Continuous 4 level continuous[edit]

Phase 1 radios in the Project 25 system use continuous 4-level FM (C4FM) modulation.^[8][9]

Applications[edit]

Binary Phase Shift Keying Bpsk

In 1910, Reginald Fessenden invented a two-tone method of transmitting Morse code. Dots and dashes were replaced with different tones of equal length.^[10] The intent was to minimize transmission time.

Some early CW transmitters employed an arc converter that could not be conveniently keyed. Instead of turning the arc on and off, the key slightly changed the transmitter frequency in a technique known as the compensation-wave method.^[11] The compensation-wave was not used at the receiver. Spark transmitters used for this method consumed a lot of bandwidth and caused interference, so it was discouraged by 1921.^[12]

Most early telephone-line modems used audio frequency-shift keying (AFSK) to send and receive data at rates up to about 1200 bits per second. The Bell 103 and Bell 202 modems used this technique.^[13] Even today, North American caller ID uses 1200 baud AFSK in the form of the Bell 202 standard. Some early microcomputers used a specific form of AFSK modulation, the Kansas City standard, to store data on audio cassettes^{[citation needed]}. AFSK is still widely used in amateur radio, as it allows data transmission through unmodified voiceband equipment.

AFSK is also used in the United States' Emergency Alert System to transmit warning information^{[citation needed]}. It is used at higher bitrates for Weathercopy used on Weatheradio by NOAA in the U.S.

The CHUshortwave radio station in Ottawa, Ontario, Canada broadcasts an exclusive digital time signal encoded using AFSK modulation.^{[citation needed]}

Standards for use in Caller ID and remote metering[edit]

Frequency-shift keying (FSK) is commonly used over telephone lines for Caller ID (displaying callers' numbers) and remote metering applications. There are several variations of this technology.

European Telecommunications Standards Institute FSK[edit]

In some countries of Europe, the European Telecommunications Standards Institute (ETSI) standards 200 778-1 and -2 – replacing 300 778-1 & -2 – allow 3 physical transport layers (Telcordia Technologies (formerly Bellcore), British Telecom (BT) and Cable Communications Association (CCA)), combined with 2 data formats Multiple Data Message Format (MDMF) & Single Data Message Format (SDMF), plus the Dual-tone multi-frequency (DTMF) system and a no-ring mode for meter-reading and the like. It's more of a recognition that the different types exist than an attempt to define a single 'standard'.

Telcordia Technologies FSK[edit]

The Telcordia Technologies (formerly Bellcore) standard is used in the United States, Canada (but see below), Australia, China, Hong Kong and Singapore. It sends the data after the first ring tone and uses the 1200 bits per secondBell 202 tone modulation. The data may be sent in SDMF – which includes the date, time and number – or in MDMF, which adds a NAME field.

Binary Frequency Shift Keying

British Telecom FSK[edit]

British Telecom (BT) in the United Kingdom developed their own standard, which wakes up the display with a line reversal, then sends the data as CCITT v.23 modem tones in a format similar to MDMF. It is used by BT, wireless networks like the late Ionica, and some cable companies. Details are to be found in BT Supplier Information Notes (SINs) 227 and 242; another useful document is Designing Caller Identification Delivery Using XR-2211 for BT from the EXAR website.

Cable Communications Association FSK[edit]

The Cable Communications Association (CCA) of the United Kingdom developed their own standard which sends the information after a short first ring, as either Bell 202 or V.23 tones. They developed a new standard rather than change some 'street boxes' (multiplexors) which couldn't cope with the BT standard. The UK cable industry use a variety of switches: most are Nortel DMS-100; some are System X; System Y; and Nokia DX220. Note that some of these use the BT standard instead of the CCA one. The data format is similar to the BT one, but the transport layer is more like Telcordia Technologies, so North American or European equipment is more likely to detect it.

See also[edit]

• Amplitude-shift keying (ASK)
• Continuous-phase frequency-shift keying (CPFSK)
• Dual-tone multi-frequency (DTMF), another encoding technique representing data by pairs of audio frequencies
• Multiple frequency-shift keying (MFSK)
• Orthogonal frequency-division multiplexing (OFDM)
• Phase-shift keying (PSK)
• Spread frequency-shift keying (S-FSK)

References[edit]

1. ^Kennedy, G.; Davis, B. (1992). Electronic Communication Systems (4th ed.). McGraw-Hill International. ISBN978-0-07-112672-4., p 509
2. ^FSK: Signals and Demodulation (B. Watson) http://www.xn--sten-cpa.se/share/text/tektext/digital-modulation/FSK_signals_demod.pdfArchived 2012-09-07 at the Wayback Machine
3. ^Teaching DSP through the Practical Case Study of an FSK Modem (TI) http://www.ti.com/lit/an/spra347/spra347.pdf
4. ^FSK Modulation and Demodulation With the MSP430 Microcontroller (TI) http://www.ti.com/lit/an/slaa037/slaa037.pdfArchived 2012-04-06 at the Wayback Machine
5. ^Sweeney, D. 'An introduction to bluetooth a standard for short range wireless networking' Proceedings. 15th Annual IEEE International ASIC/SOC Conference, Rochester, NY, US, 25-28 Sept. 2002, pp. 474–475. 2002. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1158106
6. ^Nordic Semiconductor. nRF24LU1+ Preliminary Product Specification v1.2Archived 2011-02-20 at the Wayback Machine
7. ^Bhagwat, Pravin (10 May 2005). 'Bluetooth: 1.Applications, Technology and Performance'. p. 21. Retrieved 27 May 2015.
8. ^Essam Atalla et al.'A Practical Step Forward Toward Software-Defined Radio Transmitters'.p. 1.
9. ^Steve Ford.'ARRL's VHF Digital Handbook'.2008.p. 6-2.
10. ^Morse 1925, p. 44; Morse cites British patent 2,617/11.
11. ^Bureau of Standards 1922, pp. 415–416
12. ^Little 1921, p. 125
13. ^Kennedy & Davis 1992, pp. 549–550

• Bureau of Standards (1922), The Principles Underlying Radio Communication (Second ed.), U.S. Army Signal Corps, ISBN9781440078590, Radio Communications Pamphlet No. 40. Revised to April 24, 1921.
• Little, D. G. (April 1921), 'Continuous Wave Radio Communication', Electric Journal, 18: 124–129
• Morse, A. H. (1925), Radio: Beam and Broadcast, London: Ernest Benn Limited

Binary Phase Shift Keying Generation And Detection Software

External links[edit]