HSP50215 데이터 시트보기 (PDF) - Intersil

부품명

상세내역

제조사

HSP50215

Digital UpConverter

Intersil 

HSP50215

Carrier NCO

The Carrier NCO provides the quadrature local oscillator

references for the Vector Modulator/Mixer. The Carrier NCO

input carrier frequency control word has 32 bits of resolution.

The block diagram is shown in Figure 10.

The carrier frequency is a single buffered 32-bit frequency

control, loaded 16 bits at a time into Control Words 4 and 5.

Since the DUC requires two loads, there is a possibility of a

phase glitch.

The Carrier NCO is disabled during a RST assertion or a

reset caused by writing to CW21. The Carrier NCO stays

disabled until a sync assertion is detected independent of

the initiating sync source (SYNCIN or WR CW3). The Carrier

NCO is also disabled by programming a zero in Control

Word 16 bit 3. This bit freezes the NCO and also disables

the output of the modulator.

CARRIER

FREQUENCY

SYNCIN

R

E

>G

WR CW3

R

E

>G

SYNCSEL

WR CW21

R

E

>G

RST

R

E

>G

32

START

EDGE

GEN

RESET

EDGE

GEN

EnNCO

EN OUT

R

E

>G

ACC

∑

32

> REG

SIN/COS

GEN

† ALL REGISTERS ARE

CLOCKED AT REFLCK

TO

MODULATOR

OUTPUT

18 18

SIN COS

FIGURE 10. CARRIER NCO BLOCK DIAGRAM

To avoid the phase glitch, noted above, the phase

accumulator can be disabled at reset, and the frequency can

be pre-loaded prior to asserting sync.

The maximum error is 52MHz/(232) = 0.012Hz for the

commercial part and 0.011Hz for the industrial part. The

carrier frequency can be calculated from the value loaded

into Control Address 4 and 5 by:

FCARRIER = CR(31:0) × fCLK × 2–32

(EQ. 7)

where CR(31:0) is the 32-bit frequency control word which can

range from -231 to ~231 for a NCO output range of -fCLK/2 to

~fCLK/2. fCLK is the REFCLK frequency.

This NCO frequency range allows for spectral inversion.

Given a desired carrier frequency, the value for CR(31:0)

loaded into the part can be calculated by:

CR(31:0) = INT[FC ⁄ fCLK *232 ]

(EQ. 8)

where INT[X] is the integer part of the real number X.

The most significant 18 bits of the 32-bit phase word from

the Carrier NCO drives a Sin/Cos generator. Eighteen bit

resolution is supplied on the sinusoid outputs.

Assertion of RST stops the Carrier NCO and clears the

accumulator contents. It is held disabled until a SYNCIN or

write to Control Word 3 generates an EnNCO signal to

restart the NCO.

Vector Modulator/Mixer

The frequency resolution of the vector modulator is 32 bits.

The conceptual block diagram of the Vector Modulator/Mixer

is shown in Figure 11. The modulator operates at maximum

frequency of 52MHz (commercial). The mixer takes the

sin/cos terms generated by the carrier NCO sin/cos

generator and mixes it with the input data lines I and Q. The

resulting output is given by

Output = I * cos – Q * sin

(EQ. 9)

NOTE: There is no overflow protection provided at the output of

the modulator summer, so care must be taken to ensure

that the input signals are scaled prior to input to prevent

overflow.

The mixers can be bypassed by programming Control Words

4 and 5 to zero, which sets COS = 1 and SIN = 0.

16

I(15:0)

18

COS

SIN

18

+

∑-

16

MOD(15:0)

16

Q(15:0)

EN OUT

FIGURE 11. VECTOR MODULATOR/MIXER BLOCK DIAGRAM

3-431

Share Link: