Low Cost Frequency

Multipliers Using

Surface Mount PIN Diodes

Application Note 1054

IntroductionPIN switching diodes with lowvalues of transition time canmultiply frequencies up toC-band similar to step recoverydiodes (SRD). These diodes areavailable in the low-cost SOT-23package. Several examples ofsurface mount multipliers usingthese PIN diodes are shown.

Frequency MultipliersFigure 1 shows three possible

sources for local oscillator power.A FET oscillator may be stabi-lized by a dielectric resonator.Problems may involve phasenoise, and frequency stability andaccuracy. A phase locked loop(PLL) arrangement involves acrystal source, a divider, mixer,voltage controlled oscillator, anda DC amplifier. The phase noise,excessive complexity, and costrules out this option. The crystaloscillator followed by multipliers

and amplifiers would seem to be thelogical choice for a local oscillator.However, there is an alternativelow-cost solution using Agilent’sHSMP-3820 diodes.

Low-Cost MultiplierA conventional step recoverydiode multiplier consists of adiode, a biasing resistor, andmatching filters at input andoutput. The output filter reflects

Figure 1. Local Oscillators.

÷ m ÷ n

Xm Xn

LO OUTPUT

LO OUTPUT

LO OUTPUT

FREQUENCY DIVIDERSVCO

REF OSC

φ - DET

XTAL OSC

DIELECTRIC RESONATOR

GaAs FET

GaAs FET DRO

PLL LOCAL OSCILLATOR

FREQUENCY MULTIPLIER CHAIN

2

the untuned harmonics back tothe diode where they mix to formadditional power at the tunedfrequency.

Figure 2 shows this conventionalmultiplier as well as a multiplierusing an anti-parallel pair ofdiodes. The additional dioderesults in the suppression of evenorder products, the enhancementof odd order products, and theelimination of the bias resistor.

Unfortunately the step recoverydiodes currently are too expensiveto allow the manufacture of amultiplier for high volume com-munications circuits. Fortunatelycertain kinds of epitaxial PINswitching diodes have characteris-tics which are very similar to

those of a step recovery diode. Asingle HSMP-3820 PIN diode wasmounted in shunt in a 50 ohmmicrostrip line and a 100 MHzsignal at +13 dBm was applied toit. The resulting comb of harmon-ics was measured at the output ofthe circuit as shown in Figure 3.Bias resistor was 50 ohms. As canbe seen, this epitaxial diode, witha 70 nanosecond lifetime, makes arelatively effective comb genera-tor, especially when its highvolume price is considered.

An HSMP-3822 diode pair wasmounted in shunt in a 50 ohmmicrostrip line with terminals 1and 2 connected to ground andterminal 3 soldered to the trans-mission line forming an antiparal-lel pair.

Since this product is made fromtwo dice selected from adjacentpositions on the wafer, the twodiodes are very well matched. Theresult is shown in Figure 4. Notethe suppression of even orderharmonics.

When the two spectra are overlaid(Figure 5) it is easy to see therelative enhancement of odd order

products which the antiparallelpair produces. This diode pair wasused to build two triplers and anX5 multiplier.

The first design was an X5 multi-plier operating from a 100 MHzinput at +13 dBm. The input wasmatched with a shunt inductor,and other passive componentswere added to the output toprovide filtering of unwantedsignals. The schematic of the finalcircuit is shown in Figure 6.

The measured output spectrum ofthe X5 multiplier is shown inFigure 7. As can be seen, there is astrong output at -5 dBm withunwanted signals suppressed bymore than 20 dB.

The second multiplier built(Figure 8) was an X3 type, operat-ing from a 600 MHz input. Inputmatch was accomplished with asection of series 50 ohm line 24degrees long with a shunt capaci-tor. The empirically derivedoutput matching network con-sisted of a small capacitive “flag”(a very short open circuit stub) onthe output 50 ohm line, near thediode pair.

INPUTMATCH

NETWORK

OUTPUTMATCH

NETWORK

Figure 2a. Conventional Single Diode

Multiplier.

INPUTMATCH

NETWORK

OUTPUTMATCH

NETWORK

Figure 2b. Multiplier Using Anti-

Parallel Pair of Diodes.

15

5

-5

-15

-25

-35

-45

-55

OU

TP

UT

PO

WE

R, d

Bm

0 300 600 900 1200 1500 1800 2100OUTPUT FREQUENCY, MHz

MULTIPLIER OUTPUT WITH +13 dBm INPUTAT 100 MHz

Figure 3. HSMP-3820 PIN Diode

Multiplier.

15

5

-5

-15

-25

-35

-45

-55

OU

TP

UT

PO

WE

R, d

Bm

0 300 600 900 1200 1500 1800 2100OUTPUT FREQUENCY, MHz

MULTIPLIER OUTPUT WITH +13 dBm INPUTAT 100 MHz

Figure 4. HSMP-3822 Anti-Parallel

PIN Diode Multiplier.

15

5

-5

-15

-25

-35

-45

-55

OU

TP

UT

PO

WE

R, d

Bm

0 300 600 900 1200 1500 1800 2100OUTPUT FREQUENCY, MHz

MULTIPLIER OUTPUT WITH +13 dBm INPUTAT 100 MHz

SINGLE HSMP-3820 PIN DIODE

HSMP-3822 PIN DIODE PAIR

Figure 5. Multiplier Comparison.

3

The resulting output spectrum(Figure 9) has a strong output at1.8 GHz. Unwanted sidebands aresuppressed by more than 20 dB.This was the most efficient of thethree multipliers built, with aconversion loss of 9 dB.

The final multiplier design (Figure10) was another tripler, this oneoperating from an input of 1.8GHz. The input impedancematching network/filter is shown,along with the empirically derived

output network which is also verysimple.

The output spectrum is shown inFigure 11. As was the case withthe lower frequency tripler,fundamental leakage is ratherhigh, but this is easily removedwith simple external filtering. Theoutput at 5.4 GHz is adequatelystrong, with good suppression ofthe X2 product.

Figure 12 shows conversion lossas a function of drive level for the3 multipliers. As was expected, theX5 network is the least efficientbut relatively insensitive to inputpower. The most efficient circuit,the 600 MHz input X3, was themost sensitive to drive level.None of the multipliers was asefficient as a circuit made with anexpensive, high quality SRD, butthen these examples werefabricated using inexpensive PINswitching diodes.

100 MHz

100 nH 1 pF

100 nH 3 pF42 nHINPUT13 dBm

AT 100 MHz

HSMP-3822

++13 dBM

Figure 6. X5 Multiplier.

-5

-10

-15

-25

-30

-35

-45

-50

OU

TP

UT

PO

WE

R, d

Bm

0 200 400 600 800 1000 1400 1600OUTPUT FREQUENCY, MHz

100 MHz INPUT

-20

-40

1200

Figure 7. X5 Multiplier.

C < 1 pFINPUT13 dBm

AT 600 MHz

HSMP-3822

+

12 pF

Zo = 50 Ωl = 24 DEGREES

+13 dBM

Figure 8. X3 Multiplier.

5

0

-5

-20

-25

-30

-40

-50

OU

TP

UT

PO

WE

R, d

Bm

500 1000 1500 2500OUTPUT FREQUENCY, MHz

-15

-35

2000

-10

-45

Figure 9. 600 MHz Tripler.

www.semiconductor.agilent.com

Data subject to change.Copyright © 1999 Agilent Technologies, Inc.Obsoletes 5091-4918E5966-4998E (11/99)

A possible application of thesethree multipliers is shown inFigure 13. The first multiplier ismodified to operate from a 120MHz crystal oscillator. Using twoMSA silicon monolithic amplifiers,

INPUT13 dBm

AT 1.8 GHz

HSMP-3822

+13 dBM+

2.2 pF

Zo = 50 Ωl = 41 DEGREES

5.6 pF 1.0 pF

Figure 10. 1.8 GHz Tripler.

5

0

-5

-20

-25

-30

-40

-50

OU

TP

UT

PO

WE

R, d

Bm

1.5 2.0 6.0OUTPUT FREQUENCY, MHz

-15

-35

-10

-45

2.5 3.0 3.5 4.0 4.5 5.0 5.5

Figure 11. 1.8 GHz Tripler.

9

11

13

15

17

19

21

23

25

27

29

31

CO

NV

ER

SIO

N L

OS

S, d

B

7 8 9 10 11 12 13 14 15INPUT POWER, dBm

600 MHz INPUT X3

1.8 GHz INPUT X3

100MHz INPUT X3

Figure 12. Conversion Loss vs. Input

Power.

X5MULTIPLIER

X3MULTIPLIER

X3MULTIPLIER

120 MHz+13 dBm

600 MHz–6 dBm

600 MHz+12 dBm

1.8 GHz+2 dBm

1.8 GHz+12 dBm

5.4 GHz-3 dBm

MSA-08XX MSA-08XX FET

Figure 13. X45 Multiplier.

three inexpensive multipliers, andan output amplifier, sufficientpower can be produced at 5.4 GHzfor local oscillator applications.