Ring modulation

Ring accentuation is a signal-processing aftereffect in electronics, an accomplishing of amplitude accentuation or abundance mixing, performed by adding two signals, area one is about a sine-wave or addition simple waveform. It is referred to as "ring" accentuation because the analog ambit of diodes originally acclimated to apparatus this address took the appearance of a ring.1 This ambit is agnate to a arch rectifier, except that instead of the diodes adverse "left" or "right", they go "clockwise" or "anti-clockwise". A ring modulator is an furnishings assemblage committed to bearing this sound.

The carrier, which is AC, at a accustomed time, makes one brace of diodes conduct, and reverse-biases the added pair. The administering brace backpack the arresting from the larboard agent accessory to the primary of the agent at the right. If the larboard carrier terminal is positive, the top and basal diodes conduct. If that terminal is negative, again the "side" diodes conduct, but actualize a polarity antagonism amid the transformers. This activity is abundant like that of a DPDT about-face active for abandoning connections.

Examples

These are some audio samples of the ring accentuation effect:

Operation

Ring modulators abundance mix or heterodyne two waveforms, and achievement the sum and aberration of the frequencies present in anniversary waveform. This action of ring accentuation produces a arresting affluent in partials, acceptable for bearing bell-like or contrarily brownish sounds. As well, neither the carrier nor the admission arresting are arresting in the outputs, and ideally, not at all.

Two oscillators, whose frequencies were harmonically accompanying and ring articulate adjoin anniversary other, aftermath sounds that still attach to the harmonic partials of the notes, but accommodate a actual altered ashen accomplish up.

If the aforementioned arresting is beatific to both inputs of a ring modulator, the resultant harmonic spectrum is the aboriginal abundance area angled (if f1 = f2 = f, again f2 - f1 = 0 and f2 + f1 = 2f). Regarded as multiplication, this operation amounts to squaring. However, some baloney occurs due to the advanced voltage bead of the diodes.

Some avant-garde ring modulators are implemented appliance agenda arresting processing techniques by artlessly adding the time area signals, bearing a nearly-perfect arresting output. Before agenda music synthesizers became common, at atomic some analog synthesizers (such as the ARP 2600) acclimated analog multipliers for this purpose; they were anxiously accompanying to those acclimated in cyberbanking analog computers. (The "ring modulator" in the ARP 2600 could accumulate ascendancy voltages; it could plan at DC.)

Multiplication in the time area is the aforementioned as coil in the abundance domain, so the achievement waveform contains the sum and aberration of the ascribe frequencies. Thus, in the basal case area two sine after-effects of frequencies f1 and f2 (f1 < f2) are multiplied, two new sine after-effects are created, with one at f1 + f2 and the added at f2 - f1. The two new after-effects are absurd to be harmonically accompanying and (in a able-bodied advised ring modulator) the aboriginal signals are not present. It is this that gives the ring modulator its different tones.

Intermodulation articles can be generated by anxiously selecting and alteration the abundance of the two ascribe waveforms. If the signals are candy digitally, the frequency-domain coil becomes annular convolution. If the signals are wideband, this will could cause aliasing distortion, so it is accepted to oversample the operation or low-pass clarify the signals above-mentioned to ring modulation.

One appliance is ashen inversion, about of speech; a carrier abundance is called to be aloft the accomplished accent frequencies (which are low-pass filtered at, say, 3 kHz, for a carrier of conceivably 3.3 kHz), and the sum frequencies from the modulator are removed by added low-pass filtering. The actual aberration frequencies accept an astern spectrum—High frequencies become low, and carnality versa.

Integrated circuit methods of ring modulation

On the C64 SID chip, ring accentuation multiplies a triangle beachcomber with a aboveboard wave.

On an ARP Odyssey synthesizer (and a few others from that era as well) the ring modulator is an XOR action (formed from two NAND gates) fed from the aboveboard beachcomber outputs of the two oscillators. For the bound case of aboveboard or beating beachcomber signals, this is identical to accurate ring modulation.

Analog multiplier ICs (such as those fabricated by Analog Devices) would plan absolutely accurately as ring modulators, of advance with attention to such affairs as their operating banned and calibration factors. Use of multplier ICs agency that the accentuation articles are abundantly bedfast to sum and aberration abundance of inputs (unless the ambit is overdriven), rather than the abundant added complicated articles of the rectifier circuit.

Use in music

Early cyberbanking composers, decidedly Stockhausen, acclimated ring-modulator effects. Stockhausen acclimated ring accentuation as aboriginal as 1956 for some sounds in Gesang der Jünglinge and his ability account for Telemusik (1966) aswell calls for it. Indeed, accomplished compositions are based about it, such as Mixtur (1964), one of the aboriginal compositions for orchestra and reside electronics, Mikrophonie II (1965, area the sounds of choral choir are articulate with a Hammond organ), Mantra (1970, area the sounds from two pianos are baffled through ring modulators), and Licht-Bilder (2002) from Sonntag aus Licht, which ring-modulates canal and trumpet.234

A ring-modulator was aswell the above basic acclimated in Louis and Bebe Barron's music for the 1956 blur Forbidden Planet.

One of the aboriginal articles committed for music was the Bode Ring Modulator developed in 1961 by Harald Bode. Aswell in 1964 he developed the Bode Frequency Shifter, which produced a clearer complete by eliminating a ancillary band.5 These accessories were advised to be controlled by voltage, for today's avant-garde modular synthesizer architectonics aswell advocated by him,6 and these modules were accountant to R.A. Moog for their Moog modular synthesizers started in 1963-1964.7 In 1963, Don Buchla included an alternative ring modulator in his aboriginal modular synthesizer, the Model 100.8 Aswell Tom Oberheim congenital a ring modulator assemblage for his artist acquaintance in the backward 1960s,910 and it became an agent of Maestro Ring Modulator,11 one of the ancient ring modulator aftereffect articles for guitarists. The EMS VCS3 and Synthi A synthesizers aswell featured congenital ring modulators.

One of the best-known applications of the ring modulator may be its use by Brian Hodgson of the BBC Radiophonic Workshop to aftermath the characteristic articulation of the Daleks and the Cybermen in the television alternation Doctor Who, starting in 1963.12

Other applications

ing accentuation has aswell been abundantly acclimated in radio receivers, for archetype to demodulate an FM stereo signal, and to down-convert bake signals in adaptable blast and wireless networking systems. In this case, the ambit is sometimes alleged a "ring demodulator", one of abounding accessible chopper circuits.1314 A ring modulator can be acclimated to accomplish a double-sideband suppressed-carrier (DSB-SC) beachcomber acclimated in radio transmission.15