CHAPTER 5 MONOLITHIC PLANAR MARCHAND BALUN USING A STANDARD SILICON IC PROCESS.65
5.2 A NALYSIS AND I MPLEMENTATION OF THE P LANAR M ARCHAND B ALUN U SING
5.3.3 Micromixer With a Miniaturized Marchand Balun for UWB Applications
silicon IC process as shown in Fig. 5-17. The compact size of the implemented balun is 0.25 × 0.5 mm2. The substrate resistivity is approximately 10 Ω·cm and the substrate thickness is 300 m. This balun is formed mainly by the top interconnect metal with the thickness of 3.05 m and the height to the substrate of 4.54 m. The spacing, width and length of the coupled line are 3 m, 6 m, and 1300 m, respectively.
Fig. 5-17 Die photograph of the lumped-element Marchand balun
The measurement results are displayed in Fig. 5-18. The operation frequencies are from 2.5 GHz to 12 GHz. At the center frequency of 7.2 GHz, S11, S21, and S31are -11.6 dB, -6.8 dB, -6.9 dB, respectively. The magnitude imbalance of outputs is below 1 dB up to 12 GHz. By the EM simulation, the Marchand balun without capacitors functions from 8 GHz to 30 GHz. The length reduction of coupled lines is more than 60% because of the lumped-element technique. Fig. 5-19 illustrates that the phase difference of the outputs is approximately 184 and that the dissipated loss is less than
5.3 Measurement Results
4 dB. Thanks to the balanced structure of the Marchand balun and the shorter coupled-line length, the outputs keep balanced and the dissipated loss is small enough.
0 5 10 15
-60 -45 -30 -15 0
dB(S11) dB(S21) dB(S31)
S-Parameters(dB)
Frequency (GHz)
Fig. 5-18 Scattering parameters of the lumped-element Marchand balun.
0 5 10 15
160 180 200
0 2 4
phase(S21)-phase(S31)
PhaseDifference(degree)
Frequency (GHz)
DissipatedLoss(dB)
2 2 2
11 21 31
10 log(
S S S)
Fig. 5-19 Output phase difference and dissipated loss of the lumped-element Marchand balun.
This section also demonstrates a wideband Gilbert mixer with an integrated lumped-element Marchand balun using the 0.35-m SiGe BiCMOS technology, as
Monolithic Planar Marchand Balun Using a Standard Silicon IC Process
84
shown in Fig. 5-20. The die photograph of the mixer is displayed in Fig. 5-21, and its chip size is 1 mm × 0.9 mm. The total current consumption is 13.9 mA at 5 V supply voltage.
LO
LO-LODC
LO+
Vcc
Lumped Element Marchand Balun
O/C
IF RF
LODC
Fig. 5-20 Schematic of the UWB Gilbert down-conversion mixer with an LO lumped-element Marchand balun.
Fig. 5-21 Die photograph of the lumped-element Marchand balun micromixer.
Because of the wideband balanced outputs of the lumped-element Marchand balun and the broadband mixing of the Gilbert cell, this single-ended micromixer has
5.3 Measurement Results
the property of wideband mixing operation, as shown in Fig. 5-22, and the mixer functions from 3.1 GHz to 10.6 GHz with the conversion gain of around 15.5 dB and within the gain flatness of 1 dB. In UWB applications, the 3.1-10.6 GHz bandwidth is divided into five band groups and 14 bands. Each band group in the first four band groups consists of three bands and the last band group consists of two bands. The power performances are IP1dB=-14.5 dBm and IIP3=-3.6 dBm at 3.96 GHz (the center frequency for band 2 of band group 1), IP1dB=-14 dBm and IIP3=-4.2 dBm at 5.544 GHz (the center frequency for band 5 of band group 2), IP1dB=-12.3 dBm and IIP3=-1.9 dBm at 7.128 GHz (the center frequency for band 8 of band group 3), IP1dB=-13.5 dBm and IIP3=-3.1 dBm at 8.712 GHz (the center frequency for band 11 of band group 4), and IP1dB=-14.6 dBm and IIP3=-2.9 dBm at 10.296 GHz (the center frequency for band 14 of band group 5).
0 5 10 15
-10 0 10 20
-40 -20 0 20
Conversion Gain
ConversionGain(dB)
RF Frequency (GHz)
Fixed IF:300MHz RF:1.3~14.3GHz/-33dBm
LO:1~14GHz/1.5dBm IP1dB IIP3
IP 1dB,IIP 3(dBm)
Fig. 5-22 Conversion gain, IP1dBand IIP3of the UWB Gilbert down-conversion mixer with an LO lumped-element Marchand balun with respect to RF frequencies.
Fig. 5-23 illustrates the noise figure and conversion gain of the lumped-element Marchand balun micromixer with respect to the IF frequency at the fixed LO
Monolithic Planar Marchand Balun Using a Standard Silicon IC Process
86
frequency of 4.9 GHz. The LO driven power of only 1.5 dBm agrees well with that the balun loss is acceptable. Here, the output balance is more important than the loss.
The noise figure is approximately 15.8 dB and the IF 3-dB bandwidth is approximately 1.5 GHz. The capacitor of 3 pF in the output stage conquers the dc offset and however limits the low IF band operation. The higher capacitance is needed if a lower IF corner frequency is desired.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 0
5 10 15 20
0 10 20 30 40
Conversion Gain
RF:4.91~7.9GHz IF:0.01GHz~3GHz
ConversionGain(dB)
IF Frequency (GHz)
Fixed LO:4.9GHz/1.5dBm
Noise Figure NoiseFigure(dB)
Fig. 5-23 Conversion gain and noise figure of the UWB Gilbert down-conversion mixer with an LO lumped-element Marchand balun with respect to IF frequencies.
The LO-to-IF and LO-to-RF isolations are below -40 dB while the RF-to-IF isolation is approximately -20 dB, as shown in Fig. 5-24. In addition, the RF input return loss and the IF output return loss are less than -20 dB and -10 dB, respectively, among whole UWB bands, as shown in Fig. 5-25. Therefore, this mixer is suitable for 5-group and 14-band UWB applications.
5.3 Measurement Results
0 5 10 15
-80 -60 -40 -20 0
Port-to-PortIsolations(dB)
Frequency (GHz)
RF-IF Isolation LO-IF Isolation LO-RF Isolation
Fig. 5-24 Port-to-port isolations of the UWB Gilbert down-conversion mixer with an LO lumped-element Marchand balun.
0 5 10 15 20
-25 -20 -15 -10 -5 0
IF Port LO Port
RF Port
ReturnLoss(dB)
Frequency (GHz)
IF Port LO Port RF Port
Fig. 5-25 Return loss of the UWB Gilbert down-conversion mixer with an LO lumped-element Marchand balun.
Monolithic Planar Marchand Balun Using a Standard Silicon IC Process
88
TABLE 5.1 Measurement Results of the Implemented Marchand Baluns and Their Applications in Mixers
0.35-mTSMC 2P4M CMOS
TSMC 0.35-m 3P3M SiGe BiCMOS
Item Planar
Magnitude Imbalance (dB) 2 ~ 3 < 1
Dissipated Loss (dB) ~ 6 < 4
Max S21(dB) ~ -10 -6.8
Fractional Bandwidth (3-dB
S21Bandwidth) (%) 120 131
Conversion Gain (dB) 15 15.5
LO Power (dBm) 6 1.5
IF Bandwidth (GHz) 0.4 1.5
IP1dB(dBm) -19 -13 ~ -14
IIP3(dBm) -7 -2 ~ -4
RF Return Loss (dB) < -14 < -20
IF Return Loss (dB) < -10 < -10
Noise Figure (dB) 13 15.8
Supply Voltage (V) 5 5
Power Dissipation (mW) 60 (Core) 69.5 (Total)
Balun/Chip Size (mm × mm) 0.25 ×0.66 0.25 × 0.5 1 × 1 1× 0.9
5.4 S UMMARY
In this chapter, a heuristic approach to derive the three-port scattering parameters of the lossy Marchand balun has been introduced. The appropriate Marchand balun topology with the capability of resisting the loss in the standard silicon IC process has been identified. A single-ended wideband Gilbert mixer with the integrated planar Marchand balun has been demonstrated using 0.35-m SiGe BiCMOS technology.
This wideband mixer with the integrated Marchand balun has the conversion gain of 15 dB, IP1dBof -19 dBm, IIP3of -7 dBm, IIP2of 12 dBm, a minimum noise figure of 13 dB, and works from 3.5 to 14.5 GHz with 400-MHz IF bandwidth. The lower bound of 3.5 GHz is limited by the LO stage, while the upper bound of 14.5 GHz is limited by the RF stage.
A monolithic lumped-element Marchand balun and a wideband micromixer
5.4 Summary
integrated with this Marchand balun are also fabricated using the standard 0.35-m SiGe BiCMOS process. Though the balun is realized on a lossy substrate, the dissipated loss of the balun is still less than 4 dB and the magnitude and phase errors of outputs are below 1 dB and approximately 184, respectively, thanks to the balanced structure of the Marchand balun and the advantage of the lumped-element technique. Integrating Marchand balun into the standard silicon IC overcomes the imbalance from the external balun and cables as well as reducing production cost due to the high integration. The micromixer has single-ended inputs and output and works from 3.1 to 10.6 GHz with the 15.5-dB conversion gain and within the 1-dB gain flatness. Besides, this mixer is also in possession of the IF 3-dB bandwidth of 1.5 GHz, noise figure of 15.8 dB, IP1dB of approximately -14 dBm, and IIP3 of approximately -3 dBm.