Datasheet HSMS-282x (Broadcom) - 8

Both of these networks require a crossover or a three di‑
RF in D1 R1 V+
mensional circuit. A planar mixer can be made using the
D2 68 R3 R2
SOT‑143 crossover quad, HSMS‑2829, as shown in Figure
V– C1
22. In this product, a special lead frame permits the cross‑
R4 D3
over to be placed inside the plastic package itself, elimi‑
C2
nating the need for via holes (or other measures) in the RF
D4
portion of the circuit itself.
C1 = C2 ª 100 pF HSMS-2829 R1 = R2 = R3 = R4 = 4.7 K D1 & D2 & D3 & D4 = HSMS-282R Figure 19. Schematic of Suppressed Harmonic Detector. LO in RF in HSMS-282R 4.7 K 4.7 K V+ V– IF out 100 pF 100 pF Figure 22. Planar Double Balanced Mixer.
A review of Figure 21 may lead to the question as to why
RF in 68
the HSMS‑282R ring quad is open on the ends. Distortion in double balanced mixers can be reduced if LO drive is
Figure 20. Layout of Suppressed Harmonic Detector.
increased, up to the point where the Schottky diodes are driven into saturation. Above this point, increased LO Note that the forgoing discussion refers to the output volt‑ drive will not result in improvements in distortion. The use age being extracted at point V+ with respect to ground. If of expensive high barrier diodes (such as those fabricated a differential output is taken at V+ with respect to V‑, the on GaAs) can take advantage of higher LO drive power, circuit acts as a voltage doubler. but a lower cost solution is to use a eight (or twelve) diode ring quad. The open design of the HSMS‑282R permits this
Mixer applications
to easily be done, as shown in Figure 23. The HSMS‑282x family, with its wide variety of packaging, can be used to make excellent mixers at frequencies up
LO in RF in
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
HSMS-282R IF out
similarly be used, if the quad is closed with external con‑ nections as shown in Figure 21.
Figure 23. Low Distortion Double Balanced Mixer.
This same technique can be used in the single‑balanced
HSMS-282R
mixer. Figure 24 shows such a mixer, with two diodes in
LO in RF in
each spot normally occupied by one. This mixer, with a sufficiently high LO drive level, will display low distortion.
HSMS-282R RF in 180 Low pass hybrid filter IF out IF out Figure 21. Double Balanced Mixer. LO in Figure 24. Low Distortion Balanced Mixer.
Note 4. Alan Rixon and Raymond W. Waugh, “A Suppressed Harmonic Power Detector for Dual Band ‘Phones,” to be published. 8