7

SP5659

DOUBLE CONVERSION TUNER SYSTEMS

The high 2·7GHz maximum operating frequency and excellent

noise characteristics of the SP5659 allow the construction of

double conversion high IF tuners.

A typical as shown in Fig. 5 uses the SP5659 as the first local

oscillator control for full band up conversion to an IF of greater

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

SP5659 to be used for both the up converter local oscillator with

a high phase comparison frequency (hence low phase noise)

and the down converter which uses the device in a lower

comparison frequency mode, which gives a fine step size.

50-900MHz

SP8659

SP8659

SP8659

SP8659

REFERENCE CLOCK

FIRST LO

SECOND LO

1650-2700MHz

1·6GHz

38·9MHz

Fig. 5 Example of double conversion from VHF/UHF frequencies to TV IF

BCW31

2·2n

47k

16k

TUNER

SP5659

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

1n

1

30V

22k

1n

OSCILLATOR OUTPUT

1

5V

10n

ADC

P0

P1

1

12V

68p

13·3k

15n

P3

P2

REF/COMP

10n

CONTROL

MICRO

REF

ADDRESS

SDA

SCL

SP5659

1

2

3

4MHz 18p

Optional application using on-chip

crystal controlled oscillator

Fig. 6 Typical application

APPLICATION NOTES

An application note, AN168, is available for designing with

synthesisers such as the SP5659. It covers aspects such as loop

filter design and decoupling.

The application note is published in the Mitel Semiconductor

Media IC Handbook. A generic test/demonstration board has

been produced, which can be used for the SP5659. A circuit

diagram and layout for the board are shown in Figs. 7 and 8.

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 external reference sources

The programming codes relevant to these tests are given in

Fig. 3.