SL1925

Satellite Zero IF QPSK Tuner IC

Preliminary Information

Description

The SL1925 is a wideband quadrature converter operating
from 950 to 2150 MHz, intended primarily for application
in satellite tuners.

The device contains all elements necessary, with the
exception of local oscillator sustaining network, to fabricate
a high performance I(n-phase) & Q(uadrature) phase
splitter and downconverter optimised for systems
containing RF AGC gain control. The device allows for
systems containing higher power analog interferers. For
most applications RF tunable filtering is not essential.

The SL1925 is optimised for use with a low phase noise
synthesiser, a range of which are available from Mitel
Semiconductor. This will form a complete front end tuner
function for digital satellite receiver systems utilising DSP
derotation recovery.

The device includes a very high signal handling front end
with AGC, this provides for gain control, reference local
oscillator with output buffer, phase splitter with I and Q
mixers and baseband buffer amplifiers with external
interstage filtering.

Features

Single chip system for direct quadrature down
conversion from L-band

High signal handling capability for minimum
external component count application, requires
external RF AGC of 30dB

Compatible with DSS and DVB system
requirements

Excellent gain and phase match up to 30MHz
baseband

High output referred linearity for low distortion and
multi channel application

Fully balanced low radiation design

Integral RF AGC amplifier

Two selectable varactor tuned local oscillators
with buffered output for driving external
synthesiser loop

ESD protection (Normal ESD handling procedures
should be observed)

Ordering Information

SL1925/KG/NP2S (Tubes)
SL1925/KG/NP2T (Tape and Reel)

Applications

Satellite receiver systems

Data communications systems

DS4955

Issue - 2.0

March 1999

SL1925

Preliminary Information

NP28

Figure 1 Pin connections

OPFI

OPFQ

Vcc

PSout

PSoutb

Vee

Tanks

Tanksb

Vee

Tankv

Tankvb

Vee

Vcc

Vee

IPFI

Vee

Iout

LOsel

Vcc

RFB

Vee

AGC

Qout

Vee

IPFQ

Vee

Figure 2 Block diagram

AGC

RFB

Tankv

Tankvb

Tanks

Tanksb

LOsel

vcos

DIVIDE

BY 2

AGC

SENDER

0 DEG

Iout

IPFI

OPFI

OPFQ

IPFQ

Qout

PSout

PSoutb

2, 13, 23

Vcc

5, 8, 11, 15, 17, 20, 26, 28

Vee

90 DEG

vcov

FREQUENCY

AGILE

PHASE

SPLITTER

Preliminary Information

SL1925

Quick Reference Data

Characteristic

Units

Operating range

950-2150

MHz

Input noise figure, DSB, maximum gain, 1500MHz

Maximum conversion gain (assuming 6dB filter loss)

>55

Minimum conversion gain (assuming 6dB filter loss)

<20

IP32T input referred

113

dBuV

Converter input referred IM3, two tones at 97dB

�

dBc

IP22T input referred

140

dBuV

P1dB input referred

103

dBuV

Baseband amplifier Output limit voltage

2.0

Gain match up to 22 MHz

0.2

Phase match up to 22 MHz

0.7

deg

Gain flatness up to 22 MHz

0.5

Local oscillator phase noise across entire 950MHz to 2150MHz band:
SSB @ 10 kHz offset

dBc/Hz

Table 1

The required 950MHz to 2150MHz I and Q reference LO
frequencies for quadrature direct conversion are
generated by the on board oscillators named `vcos' and
`vcov', and the phase splitter. Oscillator `vcos' operates
nominally from 1900MHz to 3000MHz and is then divided
by two to provide 950MHz to 1500MHz. Oscillator `vcov'
operates nominally from 1400MHz to 2150MHz. Only
one oscillator is active at any time and selection is made
within the phase splitter under the control of the LOsel
input. Each oscillator uses an external varactor tuned
resonant network optimised for low phase noise with a
single varactor line control. A recommended application
circuit for the oscillators is shown in Figure 4. The LO
from the phase splitter drives a buffer whose outputs
`PSout' and `PSoutb' can be used for driving an external
PLL control loop for the VCO's. The typical LO phase
noise is shown in Figure 11.

The mixer outputs are coupled to baseband buffer
outputs `OPFI' and `OPFQ' which drive external band
limit filters. The output impedance of these buffers is
contained in Figure 12. The outputs of the filters are then
connected to the inputs `IPFI' and `IPFQ' of the baseband
channel amplifiers. The outputs `Iout' and `Qout' provide
for a low impedance drive and can be used with a
maximum load as in Figure 3. The output impedance of
this section is contained in Figure 13. An example filter
for application with 30MS/s systems is contained in
Figure 14.

All port peripheral circuitry for the SL1925 is shown in
Figure 15a and 15b.

The typical key performance data at 5V Vcc and 25

�

ambient are shown in the `QUICK REFERENCE DATA'
of Table 1.

Functional Description

The SL1925 is a wideband direct conversion quadrature
downconverter optimised for application in satellite
receiver systems. A block diagram is given in Figure 2
and shows the device to include a broadband RF
preamplifier with AGC control, two oscillator sustaining
amplifiers, a frequency agile 90

�

phase splitter, I Q

channel mixers and I Q channel baseband amplifiers.
The only additional elements required are an external
tank circuit for each oscillator, and baseband interstage
filters. To fabricate a complete tuner an RF AGC stage
offering +20dB to -10 dB of gain range and a 2.2 GHz
PLL frequency synthesiser are also required. An example
application is shown in Figure 16.

In normal application the first satellite IF frequency of
typically 950 to 2150 MHz is fed via the tuner RF AGC
stage to the RF preamplifier, which is optimised for
impedance match and signal handling. The RF
preamplifier is designed such that no tracking RF filter is
required and also allows for analog interferers at up to
10 dB higher amplitude. The converter RF input
impedance is shown in Figure 5. The amplifier signal is
then fed to an AGC stage providing a minimum of 35dB
AGC control, which together with the RF attenuator
provides a possible overall tuner dynamic range of
65dB, to allow for normal operating dynamic range and
MCPC systems. The signal is then split into two balanced
channels to drive the I and Q mixers. The AGC
characteristic, and gain variation of IIP3, IIP2, P1dB and
NF are contained in Figs. 6, 7, 8, 9 and 10 respectively.

SL1925

Preliminary Information

Figure 3 Baseband output load condition

15pF

100

Note: Stripline width =0.44mm,dimensions are approximate.

Marker

Freq (MHz)

Zreal

Zimag

950

-18

1350

-15

1750

-35

2150

-29

Figure 5 Converter RF input impedance (typical)

0.5

0.2

+j0.2

+j0.5

+j1

+j2

+j5

�j5

�j2

�j1

�j0.5

�j0.2

STOP 2 500

START 700

Normalised to 50

MHz

Figure 4 Local oscillator application circuit

"vcov"

1T379

BB811

Vcnt

6.15MM STRIPLINE

9MM STRIPLINE

Tanks

Tanksb

Tankv

Tankvb

"vcos"

SL1925

Preliminary Information

Electrical Charqacterisitics

These characteristics are guaranteed by either production test or design. They apply within the specified
ambient temperature and supply voltage unless otherwise stated.
T

amb

= -20

�

C to + 70

�

C, V

= 0V, Vcc = 4.75V to 5.25V. Desired channel at fc MHz

Characteristic

Value

Min

Typ

Max

Units

Conditions

Pin

Supply current, Icc

2,13,23

130

175

RF input operating frequency

21,22

950

2150

MHz

SYSTEM

All system specification items should be
read in conjunction with Note 1.

System noise figure, DSB

21,22

Maximum gain, AGC = 1V

Variation in system NF with gain

21,22

-1

dB/dB

See Figure 10

adjust

System input referred IP2

135

140

�

See Note 2.

System input referred IP3

110

113

�

See Note 3.

System conversion gain

Terminated voltage conversion gain into

load as in Figure 3.
AGC monotonic from Vee to Vcc, see

Figure 6

Minimum AGC gain

AGC = 4.0V, 950MHz

Maximum AGC gain

AGC = 1.0V, 950MHz

Gain Roll off

950MHz to 2150MHz

System I/Q gain match

18,25

-1

Excluding interstage filter stage

System I/Q phase balance

18,25

-3

deg

Excluding interstage filter stage

System I & Q channel in band

18,25

Excluding interstage filter stage

ripple

LO 2nd harmonic interference level

-50

dBc

See Note 5

LNA 2nd harmonic interference

-35

dBc

See Note 6

level

All other spurii on I & Q outputs

18,25

�

Within 0

100MHz band, under all gain

settings, RF input set to deliver 108dB

�

at baseband outputs

CONVERTER

Converter input impedance

21,22

See Figure 5

Converter input return loss

21,22

Converter input referred IP2

21,22

121

130

�

See Note 4

Converter input referred IP3

21,22

110

112

�

See Note 4

Converter input referred IM2

21,22

-33

-24

dBc

See Note 4

Converter input referred IM3

21,22

-30

-26

dBc

See Note 4

Converter input referred 1dB

21,22

See Figure 9

gain compression (P1dB)

Converter conversion gain

Terminated voltage conversion gain in
load as in Figure 3.

Minimum AGC gain

-5

AGC = 4.0V

Maximum AGC gain

AGC = 1.0V

AGC gain control slope variation

Monotonic from Vee to Vcc, see Figure 6

AGC control input current

-250

250

�

AGC bandwidth 100kHz

Preliminary Information

SL1925

Electrical Characteristics (continued)

These characteristics are guaranteed by either production test or design. They apply within the specified
ambient temperature and supply voltage unless otherwise stated.
T

amb

= -20

�

C to + 70

�

C, V

= 0V, Vcc = 4.75V to 5.25V. Desired channel at fc MHz

Characteristic

Value

Min

Typ

Max

Units

Conditions

Pin

Converter output impedance

1,14

0.1 to 30MHz. See Figure 12

Converter output limiting

1,14

0.5

1.2

Vp-p

No Load

Converter bandwidth 1dB

MHz

No Load

Converter output roll off

1,14

dB/oct

Oscillator vcos operating range

6,7

1900

3000

MHz

Giving LO = 950MHz to1500MHz

Tanks/Tanksb

Application as in Figure 4.

Oscillator vcov operating range,

9,10

1450

2150

MHz

Application as in Figure 4.

Tankv/Tankvb

Local oscillator SSB phase noise

6,7

-80

-76

dBc/Hz

@ 10kHz offset PLL loop BW < 1kHz,

application as Figure 4. Measured at
baseband outputs of 10MHz

LO leakage to converter input

21,22

�

LOsel low voltage

0.6

Oscillator vcos enabled

LOsel high voltage

Vcc-0.7

Oscillator vcov enabled

LOsel low current

-50

�

LOsel high current

200

�

Prescaler output drive

3,4

�

Single ended into 50

. Synthesiser

should be driven differentially

Prescaler output impedance

3,4

Prescaler output return loss

3,4

BASEBAND AMPLIFIERS

Baseband amplifier input

16,27

0.1 -30MHz bandwidth

impedance

Resistance

Capacitance

Baseband amplifier input referred

16,27

�

See Note 7

IP3

Baseband amplifier input referred

16,27

111

�

See Note 7

IP2

Baseband amplifier input referred

16,27

-40

-34

dBc

See Note 7

IM3

Baseband amplifier input referred

16,27

-34

-22

dBc

See Note 7

IM2

Baseband amplifier input referred

16,27

�

Terminated voltage gain into load as in

1dB compression (P1dB)

Figure 3.

Baseband amplifier gain

16,18

Terminated voltage gain into load as in

27,25

Figure 3

SL1925

Preliminary Information

Electrical Characteristics (continued)

These characteristics are guaranteed by either production test or design. They apply within the specified
ambient temperature and supply voltage unless otherwise stated.
T

amb

= -20

�

C to + 70

�

C, V

= 0V, Vcc = 4.75V to 5.25V. Desired channel at fc MH

Characteristic

Value

Min

Typ

Max

Units

Conditions

Pin

Baseband amplifier output

18,25

impedance
Baseband amplifier output

18,25

2.0

Vp-p

pk-pk level at hard clipping.

limiting

Load as in Figure 3.

Baseband amplifier 1dB

18,25

MHz

Load as in Figure 3.

bandwidth
Baseband output roll off

18,25

dB/oct

Above 3dB point, no load

Notes : 1. Systems specifications refer to total cascaded system of front end converter/AGC stage and baseband amplifier stage

with nominal 6dB pad as interstage filter and load impedance as in Figure 3.

2. AGC set to deliver output amplitude of 108dB

�

V on desired channel, input frequency fc and amplitude of 79dB

�

V, with

two interferers of frequencies fc+146 and fc+155MHz at 97dB

�

V generating output intermodulation spur at 9MHz.

40MHz 3dB bandwidth interstage filter included.

3. AGC set to deliver output amplitude of 108dB

�

V on desired channel, input frequency fc and amplitude 79 dB

�

V, with

two interferers of frequencies fc+110 and fc+211MHz at 97 dB

�

V generating output intermodulation spur at 9MHz.

40MHz 3dB bandwidth interstage filter included.

4. Two tones within RF operating frequency range at 97dB

�

V, conversion gain set at 4dB.

5. The level of 2.01GHz downconverted to baseband relative to 1.01 GHz with the oscillator tuned to 1 GHz, measured

with no input filtering.

6. The level of second harmonic of 1.01 GHz input at -25 dBm downconverted to baseband relative to 2.01 GHz at -40 dBm

with the oscillator tuned to 2 GHz, measured with no input filtering.

7. Two tones within operating frequency range at 77dB

�

Characteristic

Value

Min

Max

Units

Conditions

Pin

Absolute Maximum Ratings

All voltages are referred to Vee at 0V (pins 5,8,11,15,17,20,26,28)

Supply Voltage, Vcc

2,13,23

-0.3

Transient condition only

PSout &PSoutb DC offset

3,4

Vcc-3.0

Vcc+0.3

Vp-p

RF & RFB input voltage

21,22

2.5

Vp-p

AC coupled, transient conditions only

All other I/O ports DC offset

1,6,7,9

-0.3

Vcc+0.3

10,12

14,16

18,19

24,25,27

Storage Temperature

-55

+150

�

Junction Temperature

+150

�

NP28 package

Thermal resistance

Chip to ambient

�

C/W

Chip to case

�

C/W

Power consumption at 5.25V

893

ESD protection

All

Mil Std-883 latest revision method 3015

class 1

Preliminary Information

SL1925

SL1925 Demo Board

The demo board contains an SL1925 direct conversion
IC and SP5769 synthesiser. Reference to the
specifications for each device may be required in
conjunction with these notes.

The board contains all components necessary to
demonstrate operation of the SL1925. The schematic
and PCB layout of the board are shown in figures 16, 17
and 18. The SP5769 synthesiser is provided to control
each of the oscillators of the SL1925.

Supplies

The board must be provided with the following supplies:

5V for the synthesiser, 30V for the varactor line and 5V
for the SL1925.

The supply connector is a 5 pin 0.1" pitch pin header.

The order of connections is 5V - GND - 30V - GND - 5V

C Bus Connections

The board is provided with a RJ11 I

C bus connector

which feeds directly to the SP5769 synthesiser. This
connects to a standard 4 way cable which is supplied
with the interface box.

Operating Instructions

1. Software

Use the Mitel Semiconductor synthesiser software. Pull
down the I

C bus section menu then select the SP5769.

It is suggested that the charge pump setting 130uA is
used, and the reference divider is set to 32. These
settings give a small loop bandwidth (i.e. 100's Hz),
which allows detailed phase noise measurements of the
oscillators to be taken, if desired.

2. VCO control

The two VCO's are selected by toggling port P1 on the
synthesiser which in turn toggles the LOsel input of the
SL1925.

VCOS is switched on (and hence VCOV off) by clicking
P1 on - a tick will appear.

VCOS oscillates at twice the LO frequency (lower band)
and is then divided by two to provide the required LO
frequency in the range 950MHz to 1500MHz
approximately.

VCOV is switched on (and hence VCOS off) by clicking
P1 off - no tick.

VCOV oscillates at the LO frequency (upper band) in the
range 1450MHz to 2150MHz approximatley.

3. AGC control

The AGC input of the SL1925 which determines the
conversion gain should be controlled by application of an
external voltage to the AGC pin, TP1.

Caution: Care should be taken to ensure the chip is
powered ON when +ve voltages are applied to the AGC
input so as to avoid powering the chip up via the ESD
protection diode of the AGC input. It is recommended
that a low current limit is set on the external source used.

4. Free running the VCO's

Select the required VCO using port P1 and then using
the software choose an LO frequency which is above the
maximum frequency capability of the oscillator. 3GHz
is suggested for both oscillators. Under this condition the
varactor control voltage is pumped to its maximum
value, i.e. to the top of the band. The oscillator frequency
may be manually tuned by varying the 30V supply.

SL1925

Preliminary Information

Figure 16

SL1925 L BAND QUADRATURE DOWNCONVERTER

Title:

MITEL

OP FI

Vcc

PSout

PSoutb

Vee

Tanks

Tanksb

Vee

Tankv

Tankvb

Vee

Vcc

OP FQ

Vee

IP FQ

Vee

Q OUT

AGC

Vee

RF inB

RF inA

Vcc

LO Sel

I OUT

Vee

IP FI

Vee

IC1

SL1925

C26

100nF

R4 1K

C25

100nF

C14

1nF

C13

1nF

VD1

1T379

VD2

1T379

VD3

BB811

VD4

BB811

C23

100nF

C24

100nF

220nF

C16

1nF

R102

120R

PORT P1

PORT P0

ADDRESS

REF/COMP

RF IP

Vee

RF IP

CH PUMP

XTAL CAP

XTAL

SDA

SCL

P3/LL

Vcc

DRIVE

IC2

SP5769

C60

150pF

C30

82pF

4MHz

R16

10K

BCW31

C31

15nF

C32

68pF

13K

5V Synth

22K

R10

R19

15K

C39

2n2

3p9

C50

100nF

C51

100pF

C42

100pF

C44

100pF

C41

4u7

C47

100pF

C43

100nF

C49

100nF

C33

100nF

100R

SMA3

I OUT

C80

15pF

R18

R100

SMA5

IP/OP FI

TP1

Ext AGC Volts

SMA1

RF IN

100R

SMA2

Q OUT

C81

15pF

R17

R101

SMA6

IP/OP FQ

SDA5

5V0

GND

SCL5

I2C BUS

C37

100pF

C38

100pF

C52

4u7

DC Power

30V

5V Synth

C34

100nF

LO SELECT

PSCb

PSCa

+5V

+30V

GND

LINK INFORMATION

2-3 FILTER INPUT

1-2 FILTER OUTPUT

LINK INFORMATION

2-3 FILTER INPUT

1-2 FILTER OUTPUT

STRIPLINE DIMENSIONS

L1 & L2 6.0mm X 0.44mm

L3 & L4 8.0mm X 0.44mm

APPROXIMATE

L1 & L2 6.15mm X 0.44mm

L3 L4 9.0mm X 0.44mm

TECHNICAL DOCUMENTATION - NOT FOR RESALE

World Headquarters - Canada

Tel: +1 (613) 592 2122

Fax: +1 (613) 592 6909

North America

Asia/Pacific

Europe, Middle East,

Tel: +1 (770) 486 0194

Tel: +65 333 6193

and Africa (EMEA)

Fax: +1 (770) 631 8213

Fax: +65 333 6192

Tel: +44 (0) 1793 518528

Fax: +44 (0) 1793 518581

http://www.mitelsemi.com

Information relating to products and services furnished herein by Mitel Corporation or its subsidiaries (collectively "Mitel") is believed to be reliable. However, Mitel assumes no
liability for errors that may appear in this publication, or for liability otherwise arising from the application or use of any such information, product or service or for any infringement of
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Purchasers of products are also hereby notified that the use of product in certain ways or in combination with Mitel, or non-Mitel furnished goods or services may infringe patents or
other intellectual property rights owned by Mitel.

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publication are subject to change by Mitel without notice. No warranty or guarantee express or implied is made regarding the capability, performance or suitability of any product or
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