HSMS282X datasheet(8/14 Pages) HP

8 / 14 page

lower cost solution is available[4].

Illustrated schematically in

Figure 19, this circuit uses diode

D2 and its associated passive

components to cancel all even

order harmonics at the detector’s

RF input. Diodes D3 and D4

provide temperature compensa-

tion as described above. All four

diodes are contained in a single

HSMS- 282R package, as illus-

trated in the layout shown in

Figure 20.

RF in

V+

V–

C1 = C2

≈ 100 pF

R1 = R2 = R3 = R4 = 4.7 K

Ω

D1 & D2 & D3 & D4 = HSMS-282R

Ω

Figure 19. Schematic of Suppressed

Harmonic Detector.

HSMS-282R

4.7 K

Ω

4.7 K

Ω

100 pF

Ω

V–

RF in

V+

Figure 20. Layout of Suppressed

Harmonic Detector.

Note that the forgoing discussion

refers to the output voltage being

extracted at point V+ with respect

to ground. If a differential output

is taken at V+ with respect to V-,

the circuit acts as a voltage

doubler.

Mixer applications

The HSMS-282x family, with its

wide variety of packaging, can be

used to make excellent mixers at

frequencies up to 6 GHz.

The HSMS-2827 ring quad of

matched diodes (in the SOT-143

package) has been designed for

double balanced mixers. The

smaller (SOT-363) HSMS-282R ring

quad can similarly be used, if the

quad is closed with external

connections as shown in Figure 21.

HSMS-282R

IF out

RF in

LO in

Figure 21. Double Balanced Mixer.

Both of these networks require a

crossover or a three dimensional

circuit. A planar mixer can be

made using the SOT-143 cross-

over quad, HSMS-2829, as shown

in Figure 22. In this product, a

special lead frame permits the

crossover to be placed inside the

plastic package itself, eliminating

the need for via holes (or other

measures) in the RF portion of

the circuit itself.

HSMS-2829

IF out

RF in

LO in

Figure 22. Planar Double Balanced

Mixer.

A review of Figure 21 may lead to

the question as to why the

HSMS-282R ring quad is open on

the ends. Distortion in double

balanced mixers can be reduced

if LO drive is increased, up to the

point where the Schottky diodes

are driven into saturation. Above

this point, increased LO drive will

not result in improvements in

distortion. The use of expensive

high barrier diodes (such as those

fabricated on GaAs) can take

advantage of higher LO drive

power, but a lower cost solution

is to use a eight (or twelve) diode

ring quad. The open design of the

HSMS-282R permits this to easily

be done, as shown in Figure 23.

HSMS-282R

IF out

RF in

LO in

Figure 23. Low Distortion Double

Balanced Mixer.

This same technique can be used

in the single-balanced mixer.

Figure 24 shows such a mixer,

with two diodes in each spot

normally occupied by one. This

mixer, with a sufficiently high LO

drive level, will display low

distortion.

HSMS-282R

180

hybrid

IF out

LO in

RF in

Low pass

filter

Figure 24. Low Distortion Balanced

Mixer.

[4] Alan Rixon and Raymond W. Waugh, “A Suppressed Harmonic Power Detector for Dual

Band ‘Phones,” to be published.

88759/02-5.PM6.0J

2001.04.25, 6:41 PM

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