(Preliminary) Analog Frequency Multiplier

PL565-68 VCXO

PHASE NOISE PERFORMANCE

Part

Number

Input

Freq.

Range

(MHz)

Output

Freq.

Range

(MHz)

Phase Noise at Frequency Offset From Carrier (dBc/Hz)

Carrier

Freq.

(MHz)

10 100 1 10 100 1 10

Hz Hz kHz kHz kHz MHz MHz

PL565-68 62.5 - 160 125 - 320 311.04

Phase noise was measured using Agilent E5052B.

-59 -93 -122 -137 -143 -149 -155

Phase

Jitter

12KHz ~

20MHz

(ps)

0.07

SUB-HARMONIC PERFORMANCE

Part

Number

Input

Output

Frequency Frequency

(MHz)

(MHz)

Spectral Specifications / Sub-harmonic Content (dBc), Freq. (MHz)

Carrier Frequency

(Fc)

@ -50%

(Fc)

@ +50%

(Fc)

PL565-68

155.52

311.04

311.04

Note: Spectral specifications were obtained usin g Agilent E7401A

-60

-60

AFM MULTIPLYING TECHNIQUE

The analog frequency multiplication is achieved through a “squaring” operation.

The math is as follows: SIN²(x) = 0.5 - 0.5×COS(2x)

A very important property of this processing is that the result is a pure sin e wave with double frequency. In theory

there are no sub harmonics but in practice the squaring operation is not perfect and a low level of sub harmonics

is present anyway. The key is that the resulting sub harmonics are very low and simple filtering with only one

inductor per squarer is adequate for excellent performance.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1(408) 9 44-0800 • fax +1(408) 474-1000 • www.micrel.com Rev 12/08/11 Page 4

(Preliminary) Analog Frequency Multiplier

PL565-68 VCXO

INDUCTOR VALUE OPTIMIZATION

The required inductor values for the best performance depend on the operating frequency, and the board layout

or module specifications. The listed values in this datasheet are based on the calculated parasitic values from

Micrel’s evaluation board design. These inductor values provide the user with a starting point to determine the

optimum inductor values. Additional fine-tuning may be required to determine the optimal solution.

The inductor is recommended to be a high Q small size 0402 or 0603 SMD component, and must be placed

between L2X and adjacent VDDOSC pin. Place inductor as close to the IC as possible to minimize parasitic

effects and to maintain inductor Q.

To assist with the inductor value optimization, Micrel has developed AFM “Tuning Assistant” documents. You can

download these documents from Micrel’s web site (www.micrel.com). The documents consist of tables with

recommended inductor values for certain output frequency ranges.

Figure 10: Diagram Representation of the Related System Inductance and Capacitance

DIE SIDE

- Cinternal at L2X = 7.625 pF

- Cpad = 1.0 pF, Bond pad and its ESD circuitry

- C11 = 0.4 pF, The following amplifier stage

PCB side

- LWB1 = 2 nH, (2 places), Stray inductance

- Cstray = 0.5 pF, Stray capacitance

- L2X = 2x inductor

- C2X = range (0.1 to 2.7 pF), Fine tune

the tank, if used.

Work out the resonance of this network and you have a good first guess for the required inductor values for

optimum performance. Non-linear behavior at large signal amplitudes can shift the tank resonance significantly,

especially at the L2X side, to a lower frequency than the calculation suggests. The Tuning Assistant documents

are based upon actual lab tests and are corrected for the non -linear behavior.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1(408) 9 44-0800 • fax +1(408) 474-1000 • www.micrel.com Rev 12/08/11 Page 7