HMC1197LP7FE datasheet(29/57 Pages) AD

29 / 57 page

For price, delivery, and to place orders: Hittite Microwave Corporation, 2 Elizabeth Drive, Chelmsford, MA 01824

Phone: 978-250-3343

Fax: 978-250-3373

Order On-line at www.hittite.com

Application Support: Phone: 978-250-3343 or apps@hittite.com

HMC1197LP7FE

v03.0314

Wideband direct Quadrature Modulator

w/ Fractional-n Pll & Vco, 100 - 4000 MHz

Reg 04h

= round(0.1 x 224) = round(1677721.6) = 1677722

fVCO =

(56 +

) = 2805 MHz + 1.192 Hz error

1677722

224

50e6

(EQ 14)

fout =

= 1402.5 MHz + 0.596 Hz error

fVCO

(EQ 15)

In this example the output frequency of 1402.5 MHz is achieved by programming the 19-bit binary value

of 56d = 38h into intg_reg in Reg 03h, and the 24-bit binary value of 1677722d = 19999Ah into frac_reg in

Reg 04h. The 0.596 Hz quantization error can be eliminated using the exact frequency mode if required.

In this example the VCO output fundamental 2805 MHz is divided by 2 (Reg 16h[5:0] = 2h) = 1402.5 MHz.

1.3.7.5 exact Frequency tuning

Due to quantization effects, the absolute frequency precision of a fractional PLL is normally limited by

the number of bits in the fractional modulator. For example, a 24 bit fractional modulator has frequency

resolution set by the phase detector (PD ) comparison rate divided by 224. The value 224 in the denominator

is sometimes referred to as the modulus. Hittite PLLs use a fixed modulus which is a binary number. In

some types of fractional PLLs the modulus is variable, which allows exact frequency steps to be achieved

with decimal step sizes. Unfortunately small steps using small modulus values results in large spurious

outputs at multiples of the modulus period (channel step size). For this reason Hittite PLLs use a large

fixed modulus. Normally, the step size is set by the size of the fixed modulus. In the case of a 50 MHz PD

rate, a modulus of 224 would result in a 2.98 Hz step resolution, or 0.0596 ppm. In some applications it is

necessary to have exact frequency steps, and even an error of 3 Hz cannot be tolerated.

Fractional PLLs are able to generate exact frequencies (with zero frequency error) if N can be

exactly represented in binary (eg. N = 50.0,50.5,50.25,50.75 etc.). Unfortunately, some common

frequencies cannot be exactly represented. For example, Nfrac = 0.1 = 1/10 must be approximated as

round((0.1 x 224)/ 224 ) ≈ 0.100000024. At fPD = 50 MHz this translates to 1.2 Hz error. Hittite’s exact

frequency mode addresses this issue, and can eliminate quantization error by programming the channel

step size to FPD/10 in Reg 0Ch to 10 (in this example). More generally, this feature can be used whenever

the desired frequency, fVCO, can be exactly represented on a step plan where there are an integer number

of steps (<224) across integer-N boundaries. Mathematically, this situation is satisfied if:





















≥

gcd

mod

0 where

gcd(

)

VCOk

VCO

and f

(EQ 16)

Where:

gcd stands for Greatest Common Divisor

fN = maximum integer boundary frequency < fVCO1

fPD = frequency of the Phase Detector

and fVCOk are the channel step frequencies where 0 < k < 224-1, As shown in Figure 40.

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other

rights of third parties that may result from its use. Specifications subject to change without notice. No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarks and registered trademarks are the property of their respective owners.

For price, delivery, and to place orders: Analog Devices, Inc.,

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106

Phone: 781-329-4700 • Order online at www.analog.com

Application Support: Phone: 1-800-ANALOG-D

HMC1197LP7FE 数据表(PDF) 29 Page - Analog Devices

HMC1197LP7FE 数据表(HTML) 29 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57

数据表下载