Transcript A new AO40 K-band Downconverter

A new AO-40 K-band
Downconverter
Grant Hodgson
G8UBN
A new AO-40 K-band
Downconverter
Grant Hodgson
G8UBN
Topics presented :
Conventional Downconverter Design
New dual-injection design with new
components


New Synthesised Local Oscillator
A new AO-40 K-band
Downconverter
Conventional 24GHz Downconverter
3 stage LNA
(NF ~ 2dB)
Sub-harmonic Mixer
Waveguide Filter
144 MHz
11.952 GHz
24.048 GHz
Harmonic Filter
x5 GaAsFET Multiplier
x5
2.3904 GHz
2.4GHz Local Oscillator
A new AO-40 K-band
Downconverter
Conventional 24GHz Downconverter
•Proven design
•Image frequency is very close to wanted frequency •
Therefore a narrow waveguide filter must be used
•
Which requires adjusting and aligning
•Local Oscillator multiplier (x4 or x5) requires aligning
•Conventional Local Oscillator also requires aligning
A new AO-40 K-band
Downconverter
Conventional 24GHz Downconverter
Photo courtesy of Mike, N1JEZ
A new AO-40 K-band
Downconverter
24GHz Waveguide Filter
Photo courtesy of Howard, G6LVB
A new AO-40 K-band
Downconverter
New 24GHz Downconverter - design objectives
•Be self-contained - no external LO etc.
•No-tune design
•Low frequency drift with temperature
•Modular design - interchange various system components
(LO, LNA etc)
•Allow reception of terrestrial Dx at 24192MHz as well as
AO-40 K-band downlink (24048MHz)
•Use new components that will not become obsolete in
less than 5 -10 years
•Encourage experimentation at microwave frequencies!
A new AO-40 K-band
Downconverter
New 24GHz Downconverter
LNA
(Optional)
24.048 GHz
Surface Mount
Sub-harmonic
Mixer
2nd Mixer
(double balanced)
4693.6 MHz
145 MHz
LSB
1st IF amp Filter
9677.2 MHz
x2
9677.2MHz x 2 = 19354.4MHz
2.4 GHz Local Oscillator
2419.3 MHz
x2
4838.6 MHz
5GHz 2-way
Splitter
4838.6 MHz
A new AO-40 K-band
Downconverter
MGA-87563
MGF4953A
HMC264
2 x MGF4953A ?
HMC204
Gali-33
x2
HMC189
HMC218
Printed Bandpass
filter
Gali-S66
Printed Wilkinson
Splitter
x2
Gali-1 Gali-6
A new AO-40 K-band
Downconverter
Harmonic suppression of HMC204 doubler
A new AO-40 K-band
Downconverter
Brief overview - image response of mixers
Intermediate
frequency
10MHz
Image
frequency
80MHz
Wanted :IF = RF - LO
100 - 90 = 10
Image response :IF = LO - image
90 - 80 = 10
Local
Wanted
Oscillator frequency
90MHz
100MHz
A new AO-40 K-band
Downconverter
A new AO-40 K-band
Downconverter
New 2.4GHz Low Phase Noise
Phase Locked Loop Synthesiser
VCO DC Control Voltage
1.3MHz Reference Frequency
2.4 GHz VCO
2419.3MHz
Loop Filter
/10
/1861
2419.3MHz / 1861 = 1.3MHz
13MHz Ultra Low Phase Noise
Oven Controlled Crystal Oscillator (OCXO)
Phase Locked Loop
Integrated Circuit :Programmable reference divider
Programmable main divider
Dual modulus prescaler
Phase/Frequency Detector
Other functions (not used)
A new AO-40 K-band
Downconverter
PCB
•Difficult choice at 24GHz
•Various options, but probably :•Separate (external) LNA
Duroid, Taconic or Similar
•Main PCB on std. FR4 fibreglass
A new AO-40 K-band
Downconverter
Summary
•Most of the design objectives have been met
•Next step is circuit design and prototyping
•Waveguide image filter has been eliminated
•True no-tune design
•Operation on K-band should become easier,
•whilst still leaving lots of room for investigation
and experimentation