A19 Rythm - Agilent Technologies PSA Series Service Manual

Troubleshooting the RF Section (E4440A, E4443A, E4445A)
RF Section Description (E4440A, E4443A, E4445A)

A19 RYTHM

RYTHM stands for Routing YIG Tuned Harmonic Mixer. This is the
first mixer for the preselected high bands, bands 1 though 4. Three
major components make up RYTHM: the input switch, YIG preselected
bandpass filter, and the harmonic mixer.
Included with the RYTHM Driver PC board which includes the current
source for the YTF coil as well as bias circuitry for the ODD/EVEN IF
Switch as well as the input switch. The ODD/EVEN IF switch optimizes
conversion loss for different harmonic mixing bands. A TTL high on
L_ODD_IF from the Front End Driver board is used for bands 2, 3, and
4. A TTL low on L_ODD_IF is used for band 1. TTL levels on
L_RYTHM_LB select the RF input switch position in RYTHM: low for
Low Band position and high for High Band position.
The RYTHM bands are bands 1 through 4 whose start (minimum) and
stop (maximum) frequencies are shown in the following table:
Band Minimum Frequency
1
2
3
4
The mixing equations are:
Band 1
Band 2
Band 3, 4
F
RYTHM uses the 1, 2 and 4
the low side of the LO harmonic. Note that band 3 and band 4 use the
th
4 LO harmonic. The artificial band break between band 3 and band 4
allows for the YTF tuning curve and the frequency response curve to
more approximate straight line segments.
The PSA uses independent ramp generation circuits for the YTO and
YTF. The YTF's center frequency is a near linear function of the tuning
current. A YTF voltage ramp generator is contained on the A13 Front
End Driver Board and the YTF current source is contained on the
RYTHM PC board. The voltage ramp feeds both the RYTHM
microcircuit as well as the PRE-SEL Tune Output port on the back
panel. The YTF is specified to have a tuning sensitivity range of 41 to
49 MHz/mA.
80
2.85 GHz
6.2 GHz
12.8 GHz
18.7 GHz
F = F + F
LO RF IF
F = (F + F )/2
LO RF IF
F = (F + F )/4
LO RF IF
= 321.4 5Hz
IF
th
harmonic of the LO. The RF is always on
Maximum Frequency
6.6 GHz
13.2 GHz
19.2 GHz
26.5 GHz
Chapter 3