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Topic: Costas loop

Related Topics

Phase detector

Separate channel signaling

Carrier wave

Phase modulation

Sideband

Teleconference

Quadrature

Digital milliwatt

Carrier

Federal Standard 1037C

Computer conferencing

Recorder warning tone

Coherence (physics)

Modulation

Interchangeability

	Costas loop (Site not responding. Last check: 2007-10-12)
		In telecommunication, a Costas loop is a phase-locked loop used for carrier phase recovery[?] from suppressed-carrier modulation signals, such as from double-sideband suppressed carrier signals.
		The same phase of the input signal is also applied to both phase detectors and the output of each phase detector[?] is passed through a low-pass filter.
		The outputs of these low-pass filters are inputs to another phase detector, the output of which passes through a loop filter[?] before being used to control the voltage-controlled oscillator.
	www.ebroadcast.com.au /lookup/encyclopedia/co/Costas_loop.html (107 words)

	QPSK demodulator - United States Patent 4,085,378
		The Costas approach suffers from a number of shortcomings one of which one is its inability to handle the modulator and demodulator phasor errors in a satisfactory manner and the other is that the conventional Costas approach requires the phase locking of the demodulator.
		The Costas loop technique is used to obtain a control signal from the detected I and Q channel baseband signals at the outputs of the respective low pass filters 25 and 25'.
		This is because the Costas loop assumes that the I and Q channel data are in quadrature and have been subjected to identical types of distortions whereas, in fact, often the I and Q channels are subjected to dissimilar degrees of phasor distortions.
	xrint.com /patents/us/4085378 (3563 words)

	Synchronous tracking device for direct spread spectrum receiver - United States Patent 4,841,545
		The Costas loop 200 includes VCO 14, the output of which is applied to a multiplier 24 via a frequency multiplying unit 23 to reduce the frequency of the received signal.
		When the tracking action of the receiver on the PN code has become stable in the delay lock loop, the synchronous tracking is then performed by the Costas loop, which is capable of adequately tracking the higher frequency carrier component, instead of the delay lock loop.
		Thus, the tracking operation is changed from the delay lock loop 100 to the Costas loop 200 by regulating the sample-and-hold circuit 12 (via line 25b) and the electronic switch 26 (via line 25c), which are controlled by the timing control signals of the control circuit 25.
	xrint.com /patents/us/4841545 (2476 words)

	Printer Friendly Version
		Another modified Costas loop configuration, where the sum of the squares of the I and Q channels is processed to contribute to the loop error signal, may inhibit stable operating points at false lock.
		The remodulator is stochastically equivalent to the polarity loop, i.e., the hard-limited Costas loop.
		Figure 9 depicts the Costas loop configuration wherein the input modulated signal (from the AGC amplifier) is split into two paths and mixed with the quadrature LO signal (from the PLL's VCO) to produce the desired I and Q baseband signals.
	www.mwrf.com /Articles/Print.cfm?ArticleID=9366 (3475 words)

	Costas loop carrier wave reproducing circuit - Patent 5086241
		A Costas loop carrier wave reproducing circuit includes a first differential amplifier circuit, a second differential amplifier circuit, a multiplying circuit, a first square circuit, a second circuit, and a double-balanced differential amplifier circuit.
		WEith this operation, a voltage proportional to a voltage obtained by multplying all the four signals, i.e., the demudulated signals P and Q, the sum signal (P +Q), and the difference signal (P-Q), as the multiplication result obtained by the first to third multipolying circiuts, is output across output terminals a and b.
		It is another object of the present invention to provide a Costas loop carrier wave reproducing circuit which allows the use of a MOS transistor.
	www.freepatentsonline.com /5086241.html (2283 words)

	Costas loop Information - costas loop audio data
		In telecommunication, a Costas loop is a phase-locked loop used for carrier phase recovery from digital costas loop suppressed-carrier modulation signals, such as from double-sideband suppressed carrier signals.
		Note: In the usual implementation of a Costas loop, a local voltage-controlled oscillator provides quadrature outputs, one to each costas loop digital implementations of costas loop of two phase detectors, i.e., product detectors.
		The same phase of the input signal is also applied to both phase detectors and the output of each costas loop audio data phase detector is passed through a low-pass costas loop in firmware filter.
	www.inanot.com /Ina-Electronics_Topics_Co_-_Cz-/Costas_loop.html (209 words)

	Costas Loop Implementation with Hypersignal Block Diagram/RIDE- Developer Zone - National Instruments
		The first loop, called the in-phase loop (or I arm), uses the VCO as in a PLL (Phase Locked Loop), and the second, called the quadrature loop (or Q arm) uses a 90 degree shifted VCO.
		The multiplier of the Costas loop can be thought of as allowing the bit polarity of the in-phase loop to correct the phase error orientation of the tracking loop, thereby removing the modulation.
		Note that Costas loop error is in a transient state during carrier acquisition and then stabilizes when the loop is phaselocked.
	zone.ni.com /devzone/cda/tut/p/id/3165 (1939 words)

	Costas Loop \| Practical Costas Loop Design - costas loop
		The Costas loop offers an inherent ability to self-correct the phase (and frequency) of the recovered carrier and, in the end, its implementation is no more complicated than the first technique.
		The mechanism of the Costas loop carrier recovery is to iterate its internally generated carrier — the VCO — into the correct phase and frequency based on the principle of coherency and orthogonality.
		The Costas loop, considering LPF1 and LPF2, acts similarly to a secondorder loop (the combined effect of LPF1 and LPF2 adds a second pole to the loop response.
	rfdesign.com /mag/radio_practical_costas_loop (2600 words)

	Mixers in Communications
		However, since the BPSK signal has a spectrum that is symmetrical with respect to the (suppressed) carrier frequency, a special type of phase-locked loop, called a Costas loop, may be used to supply the coherent reference signal for product detection.
		A Costas loop for BSPK demodulation is shown in figure 4.
		Whenever the loop is energized, it is just as likely to phase lock so that the binary 1's come out as binary 0's, and vice versa.
	members.tripod.com /michaelgellis/mixerscom.html (2320 words)

	CSD July 2000 Feature: Carrier Synchronization Techniques For DSP-Based Modems
		The Costas loop averages over the entire symbol interval as opposed to responding to the peak value of the symbol interval determined by the time-synchronized sample.
		The Costas loop is an approximation to the small SNR model of the maximum likelihood (ML) phase estimator.
		Since the loop is averaged over the entire interval, designers must examine the phase response of the phase detector feeding error signals to the loop filter.
	www.commsdesign.com /main/2000/07/0007feat2.htm (3768 words)

	[No title]
		The downlink signal was successfully demodulated, with reliable locking of the Costas loop and clock recovery loop over a wide dynamic range.
		However, reliable locking of the Demodulator's Costas loop was not obtained, and consequently the data could not be properly decoded.
		The Costas loop tuning (range 1 to 4 volts) followed the frequency as expected, and the Simulator maintained lock from -700 kHz to at least +420 kHz.
	www.gb.nrao.edu /ovlbi/memos/es50_vsoptest.txt (3479 words)

	ZRS - Zveza Radioamaterjev Slovenije
		In practice the loop bandwidth has to be decreased, if no AGC is used and both amplifiers operate in the limiting regime.
		The overall circuit therefore operates as a first-order, Costas phase-locked loop that is able to correct carrier-frequency errors between -24kHz and +24kHz.
		The loop gain is defined by the dividing ratio of the 74HC191 up/down counters and the clock frequency.
	www.ljudmila.org /hamradio/psk23cm.html (3091 words)

	Frequency Tracking (Site not responding. Last check: 2007-10-12)
		The Squared Difference Loop and PLL both require the received signal r(t) = s(kTs)cos(2pik*Ts+phi) be preprocessed in order to extract a "clean" version (rp(t) of the carrier.
		On the contrary, the Costas Loop operates directly on the received signal r(t), instead on rp(t).
		The Costas Loop reverses the order of processing: first modulating to DC, then low pass filtering, and finally squaring.
	www.rose-hulman.edu /~liuy/summary/commSys/frequencyTracking.htm (580 words)

	Fast-acting costas loop - Patent 5640425
		The Costas loop uses the in-phase mixer 31 to generate an in-phase-baseband signal by mixing a received spread-spectrum signal with cos.omega..sub.o t from the voltage-controlled oscillator, and a quadrature-phase mixer 33 to generate a quadrature-phase-baseband signal by mixing the received spread-spectrum signal with sin.omega..sub.o t from the voltage-controlled oscillator.
		In use of the fast-acting Costas loop of the present invention, the input is a BPSK signal, with g(t) being a pseudo random sequence.
		Since the minimum loop gain controls the frequency offset estimation error by increasing the filtering of e(t), and the maximum loop gain controls the convergence rate, two additional graphs were constructed showing this effect.
	www.freepatentsonline.com /5640425.html (4411 words)

	costas loop error correction
		I have come across a lot of literature saying that costas loop is used
		loop locks is a different matter, but that's beyond this post and it's
		The loop filter is the same as for any PLL.
	www.dsprelated.com /showmessage/8443/1.php (1199 words)

	HSP50210 Device Information (Site not responding. Last check: 2007-10-12)
		The matched filter output is routed to the slicer, which generates 3-bit soft decisions, and to the cartesian-topolar converter, which generates the magnitude and phase terms required by the AGC and Carrier Tracking Loops.
		In applications where the DCL is used with the HSP50110, these control loops are closed through a serial interface between the two parts.
		To maintain the demodulator performance with varying signal power and SNR, an internal AGC loop is provided to establish an optimal signal level at the input to the slicer and to the cartesian-to-polar converter.
	www.intersil.com /cda/deviceinfo/0,0,HSP50210,0.html (371 words)

	Linear Systems in LabVIEW- Developer Zone - National Instruments
		To create the unit delay, enclose the entire graph in a loop structure, which can index the input sequence elements and collect the results into the output sequence.
		In real-time systems the VI must process each value as it is acquired, perhaps from an analog-to-digital converter, and immediately return the result, perhaps to a digital-to-analog converter.
		In these cases the looping structures must include the acquisition and the result generation.
	zone.ni.com /devzone/cda/tut/p/id/2836 (1853 words)

	Analysis and implementation of carrier recovery process in a multimission remote sensing satellite ground station
		The loop has two operating modes, one as a carrier reference loop for BPSK (or UQPSK) and the other is for QPSK carrier regeneration.
		The analysis is identical to the analysis of Costas loop as explained above.
		The Costas loop and the multiplication loop configurations, among these, are the conventional techniques.
	rfdesign.com /mag/radio_analysis_implementation_carrier/index.html (3463 words)

	intell_bottom
		In the Fast-Acting Costas Loop method, a single feedback medium enables the Costas Loop to obtain the above desirable attributes.
		The adaptive gain control allows the loop to increase the gain when the loop is mainly driving towards the same direction.
		This is an open loop method for estimating the phase of the received signal and form a local reference to be used for data demodulation.
	www.gbtwireless.com /pages/intel/intel_b2.html (4960 words)

	BPSK with GnuRadio (Site not responding. Last check: 2007-10-12)
		Since phase is arbitrary, it encodes the data by sending a 1 as a phase transition and a 0 as no phase transition.
		The script that I used for this takes data from /dev/urandom, BPSK modulates it, and then sends it to the Costas loop.
		The costas module outputs both its I and Q arms (I forced both of them to be connected -- not sure how to detect whether I should populate the Q arm or not).
	web.mit.edu /imirkin/www/gnuradio/bpsk.html (362 words)

	FinalReport/SarahBailey - sdr
		A Costas loop to demodulate BPSK data, implemented as a GNU Radio component
		The transmitter and Costas loop have both been shown to work on the Universal Software Radio Peripheral (USRP).
		The red line is the received pseudonoise sequence, and the green line is the tracking loop's generated signal.
	nexp.cs.pdx.edu /~sdr/FinalReport/SarahBailey (304 words)

	Intusoft Newsletter, July 2002, Filter Library Updated
		Phase locked loops (PLLs) are used to synchronize a local clock signal with a signal that is transmitted asynchronously.
		The code model sine wave generator can be used as a VCO; however, the Costas VCO requires both sine and cosine signals to implement quadrature detection.
		It is interesting to note that for the case of a frequency offset, Vcntrl, in Figure 4 must have a corresponding DC value to remove the offset when the loop is locked.
	www.intusoft.com /nlhtm/nl67.htm (2523 words)

	Research Of Susinder Rajan
		The synchronization module(costas loop+delay locked loop) consumes 40% of area as well as 40% of total baseband ASIC power.
		But the claim is u don't increase total system power because we have removed those costas loops.
		I have implemented a complete BPSK receiver including the carrier and timing synchronization (Costas loop and early-late timing) modules in FPGA and tested it in actual hardware.
	www.geocities.com /susinderrajan/research.htm (1508 words)

	ECEn 444: The Costas Loop -- Feedback Carrier Phase Recovery for QPSK (Site not responding. Last check: 2007-10-12)
		The first QPSK Simulink Exercise assumed you knew the phase of the transmitted carrier.
		Design the Costas loop carrier phase recovery subsystem is shown below using blocks from the Simulink Library and the Communications Toolbox Library.
		Use the same look-up tables you used for your modulator to convert the integer d-hat (d-hat = 0,1,2,3) to the corresponding signal space representation.
	www.ee.byu.edu /class/ee485/simulink/qpskcostas/qpskcostas.html (341 words)

	what is a costas loop (Site not responding. Last check: 2007-10-12)
		08 Apr 2006 5:11 what is a costas loop
		can anyone give me a idea what a costas loop is.I am implementing the carrier recovery part for BPSK modulation on TMS320C6713 dsp processor using c language.so how does a costas loop help in implementing the demodulator part.
		It is a method of processing the incoming signal with a phase locked loop.
	www.edaboard.com /ftopic164331.html (84 words)

	[No title]
		One interesting and often-studied application is the phase-locked loop (PLL).
		Designers use this device to 'lock' a locally generated waveform onto both the phase and frequency of a received waveform.
		The structure in question is the Costas loop, named for J. Costas, a pioneer in synchronous communications.
	archive.chipcenter.com /dsp/DSP010315F1.html (166 words)

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