HSP45116VC-25 データシートの表示（PDF） - Intersil

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HSP45116VC-25

Numerically Controlled Oscillator/Modulator

Intersil 

HSP45116

Applications

The NCOM can be used for Amplitude, Phase and Frequency

modulation, as well as in variations and combinations of these

techniques, such as QAM. It is most effective in applications

requiring multiplication of a rotating complex sinusoid by an

external vector. These include AM and QAM modulators and

digital receivers. The NCOM implements AM and QAM

modulation on a single chip, and is a element in demodulation,

where it performs complex down conversion. It can be

combined with the Intersil HSP43220 Decimating Digital Filter

to form the front end of a digital receiver.

Modulation/Demodulation

Figure 4 shows a block diagram of an AM modulator. In this

example, the phase increment for the carrier frequency is

loaded into the center frequency register, and the

modulating input is clocked into the real input of the CMAC,

with the imaginary input set to 0. The modulated output is

obtained at the real output of the CMAC. With a sixteen bit,

two’s complement signal input, the output will be a 16-bit real

number, on ROUT0-15 (with OUTMUX = 00).

SIGNAL INPUT

16 RIN

32

CLK

PFCS

SIN

CMAC

16

NCOM

16 RO

MODULATED OUTPUT

32

CLK

PFCS

RIN IMIN

16

16

NCOM

16

CMAC

16

16 RO

D/A LO

FIGURE 5. QUADRATURE AMPLITUDE MODULATION (QAM)

The NCOM also works with the HSP43220 Decimating

Digital Filter to implement down conversion and low pass

filtering in a digital receiver (Figure 6). The NCOM performs

complex down conversion on the wideband input signal by

multiplying the input vector and the internally generated

complex sinusoid. The resulting signal has components at

twice the center frequency and at DC. Two HSP43220s, one

each on the real and imaginary outputs of the HSP45116,

perform low pass filtering and decimation on the down

converted data, resulting in a complex baseband signal.

HSP45116

NCOM

COS (wt)

HSP43220

DDF

LO

FIGURE 4. AMPLITUDE MODULATION

By replacing the real input with a complex vector, a similar

setup can generate QAM signals (Figure 5). In this case, the

carrier frequency is loaded into the center frequency register as

before, but the modulating vector now carries both amplitude

and phase information. Since the input vector and the internally

generated sine and cosine waves are both 16 bits, the number

of states is only limited by the characteristics of the

transmission medium and by the analog electronics in the

transmitter and receiver.

The phase and amplitude resolution for the Sine/Cosine section

(16-bit output), delivers a spectral purity of greater than 90dBc.

This means that the unwanted spectral components due to

phase uncertainty (phase noise) will be greater than 90dB

below the desired output (dBc, decibels below the carrier). With

a 32-bit phase accumulator in the Phase/Frequency Control

Section, the frequency tuning resolution equals the clock

frequency divided by 232. For example, a 25MHz clock gives a

tuning resolution of 0.006Hz.

SAMPLED

INPUT

DATA

SIN (wt)

INPUT

NCOM

OUTPUT

DDF

OUTPUT

0 10MHz

0 20MHz

0

FIGURE 6. CHANNELIZED RECEIVER CHIP SET

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