8

SP5669

DOUBLE CONVERSION TUNER SYSTEMS

The high 2.7GHz maximum operating frequency and

excellent noise characteristics of the SP5669 enables the

construction of double conversion high IF tuners.

A typical system shown in Fig.8 will use the SP5669 as the

first LO control for full band upconversion to an IF of greater

than 1GHz. The wide range of reference division ratios allows

the SP5669 to be used both for the up converter LO with a high

phase comparator frequency (hence low phase noise) and the

down converter which utilises the device in a lower

comparison frequency mode (which offers a fine step size).

50–900MHz

1.6GHz

38.9MHz

1650–2700MHz

SP5659

SP5659

First LO

Second LO

Reference Clock

Fig. 8 Example of double conversion from VHF/UHF frequencies to TV IF

CONTROL

MICRO

15nF

68pF

+30V

+5V

22k

16k

47k

+12V

2n2

BCW31

1n

1n

10n

P3

TUNER

OSCILLATOR

OUTPUT

13k3

P0

SCL

SDA

ADDRESS

REF 10n

18pF

4MHz

Optional application utilising

on–board crystal controlled

oscillator

2

3

4

5

6

7

13

12

11

10

89

116

116

14

15

P2

P1

ADC

Fig. 9 Typical appliction

APPLICATION NOTES

A generic set of application notes AN168 for designing with

synthesisers such as the SP5659 has been written. This

covers aspects such as loop filter design and decoupling. This

application note is also featured in the Media Data Book, or

refer to the Mitel Semicondor Internet Site http://

www.gpsemi.com. A generic test/demo board has been pro-

duced which can be used for the SP5669. A circuit diagram

and list of components for the board is shown in Figs. 10 and

11.

The board can be used for the following purposes:

(A) Measuring RF sensitivity performance.

(B) Indicating port function.

(C) Synthesising a voltage controlled oscillator.

(D) Testing of external reference

SP5669

SP5669