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Different result between sp & hpsp frequency response

November 27, 2022, 10:49 pm
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Hi everybody, 

I have the follwing circuit to check its magnitude/phase frequency response (this circuit is non-linear and also generate other harmonics rather than fundamental one) 

when i simulated with hpsp to check whether how it works with large input signal , the results are quite different in S-parameter 

i dont know how to explain it, even set input power of hpsp to about -80 dBm (small enough) : 

could anyone give me some explainations ?

this is my sp & hpsp/hp settting: 

Thanks,         

Binh

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How to plot Noise Modulating Function for VCOs in Cadence Virtuoso?

December 1, 2022, 4:37 am
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Hello,

I would like to plot the the Noise Modulating Function (NMF) for the oscillating nodes in any VCO. What are the steps for the same?

Regards,

Srayan Sankar Chatterjee

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Best Setup for Detector Circuit

December 12, 2022, 7:16 am
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Hello,

I've been having trouble figuring out the best way to set up a simulation for a detector circuit, which tool to use (e.g., VSS vs AWR) and which measurement to use. The source impedance is 50 ohms. The signal is a modulated 70 GHz carrier at -70 dBm modulated with a simple ON/OFF square wave at 100 MHz. It is incident on a Modelithics diode model configured as a low-power detector with the typical biasing circuitry for square-law detection. The intended function is that I'm able to sweep the power of the input modulated carrier from -70 dBm to -20dBm and track the rise in DC voltage at the output.

1) What is the best way to generate the modulated signal to insure it is at the right power level and has a source impedance of 50 ohms?

2) How can I take DC voltage measurements of the circuit while sweeping input power?

Thanks

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How to match the input impedance of a simple RF NMOS?

December 13, 2022, 9:46 pm
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I am trying to match the impedance of the transistor with the 50-ohm impedance of the source. I am using sp parametric Analysis and then plotting the s-parameters. 

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Simulating Kinetic Inductance in Microwave Office

December 19, 2022, 2:36 pm
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Hello all,

I am working on a project which requires me to simulate superconducting nanowires, whose reactance is dominated by kinetic inductance, in AWR Microwave Office. In order to model this, I would like to create a material which has a certain excess sheet inductance, but I am struggling with how to do this. I know that this is possible because there are several papers who claim to simulate these nanowires with AWR Microwave Office (Ex.: https://arxiv.org/pdf/1602.06895.pdf). I know that you can define impedances with excess surface reactance, but this does not work for me because I need the reactance to be frequency dependent. I would greatly appreciate any guidance on how to proceed.

Thanks,

Sam

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RF Detector

January 16, 2023, 6:58 am
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I was just wondering if there is an easy way to simulate a Rf detect IC, more specifically an ADL5902, in AWR, as i want to look at its use in an AGC system.

Simon

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IIP3 Calculation of N-path (N=4) Mixer

January 26, 2023, 9:17 pm
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Hi,

I'm trying to calculate IIP3 value of an 4-path Passive Mixer (circuit given in the figure below) 

I've few queries:

1). Which simulation is best for this purpose? (according to online tutorials, there are several approaches available: hb, qpss with hb, qpss with qpac)
2). Should I use ports for all LO frequencies or only one?
3). When I'm placing ports on all LO frequencies (4 LO with 25% duty cycle, and 90° phase shift), and trying to simulate using qpss with hb analysis, the "Total number of harmonics" is equal to 117.649k (which is huge no.) due to which the simulation is taking a very long time (screenshot attached below).

4). If there a tutorial available to achieve IIP3, P1dB, NF of n-path mixers, if yes please let me know.

Regards
Arpit

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4-Path Mixer IIP3 calculations

January 29, 2023, 8:02 pm
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Hi,

I'm trying to calculate IIP3 of a 4-path mixer. I've 6 PORTS in my circuit: 1 for RF, 1 for LO (I created quadrature signals using delay block of analoglib) and 4 PORTS on the output.

When I tried to simulate this using (qpss using hb), I got an error (screenshot attached)

My circuit:

Simulation test bench:
   

Error I got:

Please let me know the correct way to calculate these parameters for N-path mixers;

Regards
Arpit

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Regarding User Guide

February 3, 2023, 4:28 am
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Hi,

I wanted to get "Virtuoso® Spectre® Circuit Simulator and Accelerated Parallel Simulator RF Analysis User Guide".

Where I can find this guide in my installation directory?

Regards
Arpit

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Load based and frame based equipment

February 27, 2023, 5:35 am
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Hi all, I just started working in lab that offers testing and certification services. Part of my job is to know the regulations. However, I am new to this field and recently started studying Etsi EN 300 328. I would like to know what are load based equipment and frame based equipment and what are the differences.

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wqsdq

February 27, 2023, 4:29 pm
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Jee Measurement

March 9, 2023, 9:28 am
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i want to better understand how the jee parameter is obtained.

I send a 50Mhz clock through a buffer, I set a pss simulation with a beat frequency of 50Mhz and a pnoise  from 10kHz to 25Mhz with sampled noise, using as timing event trigger when the output of the buffer goes to 0 ( rise edge)

Looking at some documentation i see the jitter should be calculated as 

So i extract the slope from the pss transient, then i took the average of the Sn(f) ,looking at the average of Output Noise( multiplied by the 25Mhz-10kHz) and try to calculate the jee using the formula.

But i does not obtain the same result as the Jee using this procedure.

What i'm doing wrong? Is Sn(f) the Output Noise from the Direct Plot form?

Thanks in advance

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Using Ideal Frequency Divider Block in Cadence

March 12, 2023, 8:01 pm
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I am using the ideal freq divider block from the rflib to troubleshoot my 100GHz PLL. I need to assign the parameters in the freq div block. My input frequency (coming from the VCO) is around 100GHz, and I need an output frequency of 100MHz - so I need a divide ratio of 1000. I have attached a screenshot of the parameters I have assigned in the freq divider block. These parameters are not correct since I am getting a 0 output out of the freq div block (see attached waveform). Please help me with assigning the parameters to my freq divider block (I am not sure what some of these parameters really mean, I am a student and still learning). I appreciate any help! Green is the output of my VCO and purple is the output of freq divider. 

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RMS Phase Error Calculation of a phase shifter

March 15, 2023, 11:45 pm
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Hi,

 I have designed a phase shifter (ex: phase shift range 360 degrees, step 2.8125 degrees),  with the reference state of S21 and the phase shift state of S43. Then I have a "phase shift = phase(S43)-phase(S21)". I also created an calculated phase shift which means the exact phase shifter I want.

Now define "phase error = phase shift - calculated phase shift "

My question is how to calculate the rms phase error in the cadence virtuoso in detail. ( I did try by myself but it did not work)

Besides, these are equations I use to build rms phase error. But they are used in ADS instead. Of course, I could move all the phase shift states to ADS under s2p format file for calculation but it took me a lot of time. So I need your help!

Many thanks for any support!

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PPV Plot for flat squarish waveform

March 19, 2023, 11:46 am
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Hello,

I am trying to plot the ISF for a squarish waveform generated by an oscillator. I am aware that the simulator plots PPV not ISF. However, the shape of PPV and ISF will be more or less the same (please correct me if I'm wrong). The red waveform is the transient waveform for an output node for my oscillator. The blue waveform is the PPV plot for the same node. It has been discussed in literature that for the flat part of a squarish waveform the ISF will be 0. I have highlighted the flat-ish part of the transient output but the PPV plot is not 0 (neither constant) for that region. 

Why is it so?

Please note I have made 2 assumptions:

1. PPV and ISF look the same (they have different definitions)

2. The red waveform is treated as a squarish waveform by the simulator.

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How to substract bussed analog signals ?

March 21, 2023, 9:13 am
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Hi,

I am facing the following issue with Maestro Assembler / Explorer.

- Output # 1 is [ Test_1 = vtime('tran "/RFFE/HPPA/CORE/CHANNEL<3>/lo_pmos_msb<30:0>") ]. This is actually a bus of 31 analog waveforms. This output is correctly evaluated by Assembler.

- Output # 2 is [ Test_2 = vtime('tran "/RFFE/HPPA/CORE/CHANNEL<3>/MSB<30:0>/local_vss") ]. This is again a bus of 31 analog waveforms, which evaluates correctly.

All waveforms are from the same transient simulation : They share the same time-points.

Now, If I declare a third output as [ Test_3 = Test_1 - Test_2 ], I would expect Test_3 to be a bus of 31 waveforms with [ Test_3<i> = Test_1<i> - Test_2<i>, ], but it fails to evaluate.

Any idea to solve this ?

Thanks

/Guillaume

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N-Path Filter IIP3

April 20, 2023, 2:20 am
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Hi everyone,
I am trying to design an N-Path Filter with fLO=1GHz
But i dont know how to simulate the IIP3 of N-Path Filter on cadence spectre.
Can you give me some guide.
Thank you

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QPSS simulation

April 21, 2023, 10:53 am
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Hi everyone,

I am trying to use QPSS to simulate IIP3 of a mixer. It is ok when all source in my circuit are sin wave sources. But when i use a pulse source, the log file show that QPSS did not convergence. 

Can you give me a guide to fix it ?

Thank you.

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RE : calculating the output power of a Quartz oscillator

April 25, 2023, 5:28 am
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Help !

I am designing a Crystal Oscillator ( which is a complex load) and trying to calculate Output power (to avoid over loading the crystal). I am using pss to simulate it and I get a tran waveform.

The power is complex so it is not easy to calculate. For example in a transient simulation phase information isn't readily available.

When I create calculations in calculator tool  get several different answers, and I am not sure which to trust

How should I calculate the output power?

What is the 'recommended' method?

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Need help designing an aperturecoupling

April 25, 2023, 2:25 pm
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Hello, i have done some studies about aperture coupling and for a project i have to simulate a coupling method from 1-2GHz with good S11 and S12.

I have done small analysis to microstriplines and their S11 as well as aperture coupling. To get good S11 with a open microstripline i created a via at the end to have a short circuit from the via to the ground plane. i did some simulation for the aperture size and position but all the results i got were super bad. The signal gets coupled from the bottom port (far up in the picture) to the top parrt so i moved the via more in direction bottom end of stripline. Currently i am running a lot of trial and error simulations but i feel like this cant be the way! I added a picture from my current structure

Does anyone has experience designing an apperturecoupling and can help me with some parameters conventions?

Best regards.

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