IAM-91563 Datasheet, PDF (9/14 Pages) Agilent(Hewlett-Packard) – 0.8-6 GHz 3V Downconverter

The DC bias is also applied to the mixer through the IF
port. Figure 25 shows how an inductor (RFC) is used to
isolate the IF from the DC supply. The bias line is bypassed
to ground with a capacitor to keep RF off of the DC supply
lines and to prevent dips or peaks in the response of the
mixer.
Bypass
Capacitor
V_d
RFC
RF
IF
IF
Output
LO
Figure 25. Bias Connection.
LO Port
The LO input port is internally matched to 50 Ω within a
2.2:1 VSWR over the entire operating frequency range. Ad-
ditional matching will normally not be needed. However,
if desired, a small series inductor can be used to provide
some improvement in the LO match and thus reduce the
LO drive level requirement by up to 0.7 dB. Reflection co-
efficients for the LO port are shown in the table of Typical
Reflection ­Coefficients.
Source Bypass Pin
The Source Bypass pin should be RF bypassed to ground
at both the RF and LO frequencies as well as the IF. Many
capacitors with values large enough to adequately bypass
lower intermediate frequencies contain parasitics that
may have resonances in the RF band. It is often practical
to use two capacitors in parallel for this purpose instead
of one. A small value, high quality capacitor is used to by-
pass the RF/LO frequencies and a large value capacitor for
the IF. When biased in the high linearity mode, a resistor is
added from the Source Bypass pin to ground.
High Linearity Mode
The IAM-91563 has a feature that allows the user to place
an external resistor from the Source Bypass pin to ground
and increase the device current from a nominal 9 mA to
as high as 20 mA. The additional current increases mixer
linearity (IP₃) and output power(P_1dB). Mixer performance
at higher device current is shown in Figures 26 and 27.
14
12
NF
10
8
GAIN
6
4
7 9 11 13 15 17 19
DEVICE CURRENT (mA)
1000 56 21 9 5 3
Approximate Resistor Value ( )
Figu_Fir_ge_ur2_e6₂.₆A_.v_Aa_vil_aa_ilb_al_be_leC_Co_on_nv_ve_er_rs_si_io_on_{n G}G_aa_ii_nn_aa_nn_dd_SSS_BS_NB_oN_iso_eise Figure vs. Device Current
(SoFuirgcuereRvess.iDsteovri)c.e Current (Source Resisitor).
0
-2
IP3
-4
P1 dB
-6
-8
-10
7 9 11 13 15 17 19
DEVICE CURRENT (mA)
1000 56 21 9 5 3
Approximate Resistor Value ( )
Fig_Fu_igre_ur2_e7₂.₇O_. n_Oe_ned_dB_BC_Co_om_mp_pr_re_ess_ss_ii_oo_nn_aa_nn_dd_InI_pn_up_tu_Tt_hT_irh_di_Ord_rdO_errder Intercept Point vs. De-
vic_Ie_nC_teu_rr_cr_ee_pn_tt_P(_oR_ine_ts_vis_st_.o_Dr_e)_v._{ice Current (Resistor).}
As an example of improved linearity, the use of a 15 Ω re-
sistor at the Source Bypass pin increases the device cur-
rent to 14 mA. At 1.9 GHz, the input IP₃ is increased from
-6.5 dBm to -3 dBm. Increasing the LO drive level from -5
dBm to -1 dBm further increases the input IP₃ to 0 dBm.